Fraser Cain:  Hey Pamela, are you ready for the Theory of Everything?

Dr. Pamela Gay: I think the correct title for this show is:  AstronomyCast:  the Episode where Fraser breaks Pamela’s brain!

Fraser:  I’ve been looking forward to this show.  We’re going to need another co-host by the end of this show, so if there are any Astrophysicists out there, I intend to shatter Pamela today, so resumes gratefully accepted.

Pamela: And I’d just like to add the disclaimer Observational Astronomist not String Theorist.

Fraser:  [Laughter] Right so at the earliest moments of the Universe there were no separate Forces.  Energy or Matter was all just the same stuff and then the different Forces froze out differentiating into Electromagnetism – the Strong Force and the Weak Force.  

Today we’re going to look at the problem that has puzzled Physicists for generations.   Is there a single equation that explains all the Forces that we see in the Universe and is there some way to put Gravity into it?  Pamela, in preparation for this show, you promised to solve the problem and then win a Nobel Prize for the show.  So how did that go?

Pamela: Um, yeah let’s not talk about that one.

Fraser:  I’m thinking you’ll just come up with it as we go. [Laughter] You’ll go:  “Oh, I know!  Here’s how it works.” Then we’ll sorta spend the rest of the show working on that [Laughter]. Then we’ll send in the application for the Nobel Prize and Sweden here we come.

Pamela: I think I can probably give a half reasonable layman’s explanation of what’s going on, but let’s leave it at that.

Fraser:  Alright.  So I guess the part that’s interesting is we’ve spent the last three shows talking about Gravity, Electromagnetism and the Strong and Weak Nuclear Forces.  How do these Forces come together and how did Physicists work this out?

Pamela: It started as so many things start, with misdirection.  Looking at all the Forces and looking at the history of Physics, people went well; originally Electricity and Magnetism were considered two completely different things. Then Maxwell came along and unified them.  What if we can just continue this trend and just keep putting things together?  

So as we develop this Four-Force theory of the Universe, which seems to work, it was Einstein perhaps who first gave the most stubborn attempt at unifying the Forces.  What he noticed was the Weak Nuclear Force and the Strong Nuclear Force that had one set of mathematical descriptions.  

Gravity and Electromagnetism have their own mathematical formulism.  But when you look at the form for Gravity and when you look at the form the Electric Force, they mathematically have the exact same set up.  

A constant times two qualities of the particles being looked at, in this case either their Masses or their Charges over their separation squared.  He figured that since they must have the same mathematical formulism according to experimentation, then perhaps there is a way to unify these two Forces.

Fraser:  Okay, hold on before you go any further. He understood that both Gravity and Electromagnetism decrease their strength by the inverse square of the distance, right?  So, the further you get the weaker they become at exactly the same rate and that they both have a Constant.  So they just look like they’re the same thing. I could see how anyone could look at that and just think they’ve got to be just two versions of the same Force.

Pamela: As a Physics Prof I’m guilty of teaching the equation for Electric Force and going “look, it’s identical to Gravity” and no it’s not.  [Laughter] What we’ve learned since then unfortunately is Gravity separated itself off first and Electromagnetism sort of separated itself off last.  You really can’t get from one to the other without getting through the Strong and the Weak Force, so he couldn’t get there.

Fraser:  Right.  So how far did he get?

Pamela: He didn’t get anywhere.  He just tried.

Fraser:  But didn’t he like end his life working on this?

Pamela: All because you end your life working on a problem doesn’t mean you’re working on it in a way that leads to anything useful.  It’s a kind of sad state.  In the early parts of Einstein’s career, he made amazing breakthroughs.  But at the end of his career as well as being an amazing mentor to the field and creating lots of quotes that go on posters nowadays, he was spending his time trying to unite two Forces that just refused to be united.  

It was a noble effort and it didn’t work.  The problem that we have is Physics is controlled by sub-atomic particles and he was looking for a more geometric way, a non-particle way to bring these forces together.  

It’s only as we’ve started to extend our understanding of Particle Physics, as we’ve started to discover things like anti-Matter, as we’ve started to think about things that still aren’t testable like Super-Symmetry and String Theory, that we’ve even found mathematical ways to make it conceivable that we can bring these Forces together.

Fraser:  Okay, so it’s almost like there was a whole bunch of additional information that has only since recently been seen with the Big Particle Accelerators and some of the other theories that have shown that the problem is a lot more complicated than Einstein might have thought that it was.

Pamela: That’s exactly the problem.

Fraser:  Right.  How then did Physicists understand that Electromagnetism could be collected together with the Weak and Strong Forces then?

Pamela: The first thing that they had to do was look at the particles that mediate the Forces.  Look at the Bosons.  In this case it’s the 4 Electromagnetism – the Photon that carries the Electromagnetic Force and the W & Z Bosons that carry the Weak Nuclear Force.  

As you crank up the energy in a system, as you turn up the temperature and the density, the Photons and the W & Z Bosons start to have similar energies.  As the Photons have the same Energy as the W & Z Bosons, they start to act in the exact same way.  At these higher energies  – exact same way is probably too strong a way – but they start to act in ways that you can’t differentiate.  

Fraser:  Okay, whoa! [Laughter] Now as I remember you teaching me, Energy and Matter are interchangeable.

Pamela: Yes.

Fraser:  So Photons, which move at the speed of light, can be turned into Matter and anti-Matter at the same time.

Pamela: Yes.

Fraser:  So what you’re saying is that if you increase the Energies of the Matter of the System, you get to the point where the Photons and the Bosons kind of have the same amount of Energy.  If you converted the Photons to Bosons, you’d get the same amount.  Is that right?

Pamela: I wouldn’t say you’re converting anything.  You’re dealing with…

Fraser:  I’m not saying that you’re converting but you’re saying you have an equivalent amount.

Pamela: Yeah.  The Photons are a type of Bosons.  So you have the Photons carrying the Electromagnetic Force and you have the W & Z Bosons – because we named them stupid, you have the W’s and the Z’s – are carrying around the Weak Nuclear Force.  As you crank up the Energy of the entire system, the Photons Energy goes up too.  

Eventually the Photons are carrying as much Energy as the W and the Z Bosons.  Once you get to these super high energies, these super high densities in temperatures you start to not be able to tell the difference between the Electromagnetic Force and the Weak Nuclear Force.  At this point the two Forces start acting as a unified Electro-Weak Force.

Fraser:  Right.  This is the Electro-Weak Force. So where did the Electro-Weak Force actually show up in the Universe?

Pamela: They first started to separate somewhere a little bit before 10 to the minus 10 seconds after the Big Bang so we’re still like way beginning of the Universe.  But, we’re going to go even earlier than this.

Fraser:  So fractions after the beginning of the Universe – the Big Bang – Bang and then you just have the Electro-Weak Force and then moments after that it separates into Electromagnetism and the Weak Force.

Pamela: Yes. The separation starts to occur when the Universe had cooled off.  I love this idea.  The Universe has cooled off to ten to the 27 Kelvin.

Fraser:  It’s merely a one followed by [Laughter] 27 zeroes Kelvin. 

Pamela: And the Energy at that point is a hundred giga Electron Volts.  

Fraser:  Right.  I think the center of the Sun is like 15 million Kelvins.  

Pamela:  It’s a big High Energy….

Fraser:  Yeah, it’s pretty High Energy Physics.  Now we’ve taken the two Forces, mushed them together, and then where does the Strong Force come into this?

Pamela: The Strong Force, we haven’t actually been able to experimentally say can probably been combined in with the Electro-Weak.  But we think it can.  This is where we’re still kinda working on things.  We know there was an Electro-Weak Force, a time when Electromagnetism and Weak were combined.  

We think using what we call Grand Unified Theories that there is an earlier time at a little bit before 10 to the negative thirty-fifth of a second after the Big Bang or so, when the Universe was a mere 10 to the 27 Kelvin, that the Strong Force and the Electro-Weak Force were able to combine using similar mechanisms to how the Weak Nuclear Force and the Electromagnetic Force were able to combine.  

You crank the Energy up, all the Bosons start acting the exact same way and when all the Bosons are acting the same way then all the Forces act the same way – we think.  

Fraser:  If I understand there have been many predictions made by this Theory and so far a lot of these Particles have been detected in the Particle Accelerators that have been used so far, right?

Pamela: This is where things start to get tricky.  We have direct evidence of W & Z Bosons.  They’ve been discovered.  The Gluons that carry the Strong Nuclear Force are a little bit trickier.  We think we have evidence of them.  We say we have evidence of them, but it’s not like we’ve tracked one in a bottle and carried it around.  

The problem with Gluons is they only exist inside Nuclei.  And to get at a Gluon you have to break something into lots of little tiny bits and thus you’ve broken apart the thing that the Gluon lives inside.  

So we see what looks like the Energy of a Gluon falling apart, but it’s a little bit harder to understand how to combine the Physics when we can’t take a Gluon and study it.

Fraser:  This is going to be one of the objectives I guess of the Large Hadron Collider, right?  Crank the Energies up to another level where you might be seeing Gluons all day long.  

Pamela: You’re still breaking apart the things they live within.  You’re still breaking up what we call Hadrons – the Particles that are inside Nuclei.  As long as those things are broken up the Gluons are unstable, they’re just falling apart.  

What the Large Hadron Collider is going to do is find us another one in the missing Bosons.  This is the Higgs Boson.  One of the things that is also kinda broken with our current understanding is we don’t know where Mass comes from.  One of the really troubling things that we have to deal with is why is it that when Electromagnetism and the Weak Force split we ended up with the Photon which has no Mass and we ended up with the W & Z Bosons that have Mass and why is it that the Gluons have so much Mass or Energy however you want to look at it?  

This is one of those things that really confuse us.  We think that it is the Higgs Boson that brings Mass to things.  The more we can learn about the Higgs Boson the more we can understand how it is able to do all the crazy things it does.

Fraser:  The hope is that the Large Hadron Collider will have enough Energy to be able to actually be able to start generating these Higgs Boson Particles so that Scientists will be able to detect them and work the accurate numbers for the Higgs Boson into their calculations.

Pamela: It’s a goal.

Fraser:  Yeah.  All right so this is the Standard Model, right?  We’re kinda up to the Standard Model here…

Pamela: Yeah.

Fraser:  …of Physics where the E^m becomes the Electro-Weak and then the Electro-Weak merges in with the Strong Nuclear Force…I think you said earlier in the show then the first Force to hive? 14:29 off was Gravity.  I’m assuming then that if we just crank the Energy levels even higher the Gluons start to act like Gravitons?

Pamela: Well and here’s where we just don’t know.  We have a Particle Physics understanding of how Electromagnetism works.  We have a Particle Physics understanding of how the Electro-Weak Force works and of how the Strong Force works by itself.  

We’re still working on the Grand Unified Theory that gets us all the way to uniting these Forces together.  But we don’t have a Particle Physics understanding of Gravity.  When we look at Gravity if you follow Einstein’s way of visualizing it, it is a change in the Geometry of Space.  

Now we’re trying to switch over to a Quantum Mechanics view of everything where Force is carried by Particles; where nothing is smooth and where you’re dealing with probabilities and Gravity just doesn’t fit within that way of looking at things.  

As we have been trying to unify the Forces, we have to first find a Quantum Mechanics view of how Gravity works – Quantum Gravity.  We don’t have that.  In order to try and get there people have been going lots of different directions and as near as we can tell the best way to get there from here is perhaps through String Theory.

Fraser:  I’m going to put a line in the sand right now and say up until now we have lots and lots and plenty of evidence.  We’re going to move into pure speculation [Laughter] land.  

It kills us to do it because we love facts-based observational Astronomy but we know that a lot of you are really interested in this subject.  We’re going to move forward into the purely theoretical – the land where there is no evidence there is only theories. [Laughter] So proceed.

Pamela: Well, okay but first let’s start a little bit more grounded in what we actually know.  We have to …….

Fraser:  I drew a line!

Pamela: I know.

Fraser:  We have a line in the sand here. Okay, I’ll let you go back as long as we can go back into crazy land again when we’re done. [Laughter]

Pamela: So we have to start with the Standard Model of Particle Physics and we have to show that it is broken.  When we look at all the stuff that’s out there, all the stuff that’s making you, me, tables, chairs, all that sort of stuff we find there are six happy little Quarks.  

The up and down Quarks conveniently make the Protons and Neutrons which are stable.  They line up in our happy little first-generation part of this chart conveniently with the Electron and the Electron Neutrino all stable themselves.  

Then we end up with a second generation – two more Quarks two more of what we call Leptons.  Electrons and Electron Neutrinos are Leptons.  So we have this generation that includes a Muon and then we have a third generation – 2 more Quarks.  Another Lepton – the Tau Particle and the Tau Neutrino to go with it.  Everything nicely lined up like little soldiers.  

Also matching these we have our 4 Bosons.  We have the Photon, the Gluon, and the W & Z Bosons.  Everything lines up symmetrically.  There’s no reason for this.  This actually led one Nobel Laureate to say who ordered the Tau Particle when it was finally discovered? Symmetries without reason are confusing but we’re about to make it worse.  

In trying to understand how it is that you can combine the Quarks to build Hadrons and how everything has Mass, we realized we couldn’t get there from here easily.  The Higgs Boson introduced a lot of challenges.  The way to get around those mathematical challenges was to then introduce a new Particle to match every Particle we already knew.  

Fraser:  Wait, hold on a second we haven’t even discovered the Higgs Boson yet but Physicists are predicting the Higgs Boson but they already know what their problem is with the Higgs Boson?  

Pamela: [Laughter] Yes.  We’ve had this happen before.  This was actually a problem that was dealt with in the 19^th Century with the Electron.  We couldn’t explain the Mass of the Electron.  There’s just too much stuff stuck into too small an area.  

The way we were finally able to explain the creation of Electrons was through anti-Matter.  Because we have Electrons and Positrons the anti-Matter version of the Electron, it’s possible to figure out mathematically how this stuff, all the Charge, all the Mass into basically a point in Space to create an Electron.

Fraser:  So we’ve got the Matter and we’ve got the anti-Matter and they come together and produce a tremendous amount of Energy or we go the other way, we turn Energy into Matter and anti-Matter.  I don’t understand what that has to do with the Higgs.

Pamela: We basically took and said okay we have all these normal Matter Particles and now we’re going to double the number of Particles by creating anti-Matter and it fixed all the math.  

Then we had the Higgs Boson and we couldn’t figure out how to make it interact politely with all the things that had Mass.  We were kind of confused by things like Photons don’t have Mass and Gluons have a high amount of Energy which is like having Mass.  

This made no sense. The way around it seemed to be to create yet another entire family of Particles.  
Fraser:  So just to make the Higgs work, you then have to predict a whole pile of additional Particles on top of that.  So, it’s almost like they all come together.  

You get the Higgs and then you get some other Particle that makes it work and the only way you can have that Particle that makes it work is have a whole bunch more particles.  

Pamela: Yes.  We’re okay with this.

Fraser:  [Laughter] Okay with this, all right.

Pamela: [Laughter] This is actually something that sort of kind of maybe makes predictions that are provable.  The Super Symmetric Partners – the Spartners have sort of kind of predicted Masses and the lightest of them is something that we like to blame Dark Matter on sometimes.  

It’s possible the lightest of these Super Symmetric Particles might be something Large Hadron Collider could get at.

Fraser:  So would there then be an equivalent – you went through all the Particles in all their happy shapes and all lined up like they’re little soldiers – there would be Symmetric Particles for all of those?

Pamela: Yes!

Fraser:  Right and including the as of yet undiscovered Higgs.

Pamela: Probably.

Fraser:  But like what does this have to do with Gravity?

Pamela: Now we’re trying to figure out how to mathematically describe all of this.  In the process of trying to describe all of these Particles, Scientists struck on the idea of what if Particles are nothing more than Strings that are oscillating in different ways and the way they oscillate defines the different characteristics of the different Particles. 

This is where the math gets scary.  It’s out of trying to come up with the math that describes all of these different Particles that as you start to try and figure out how to build a Proton out of Quarks?  How do you build Neutrons?  How do you build what we call Hadrons?  

Protons and Neutrons are Hadrons.  In the process of trying to figure this out, they ended up with this weirdo Particle that had a set of characteristics including no Mass that wasn’t generally useful unless it just happened to be the Graviton.  It actually sorta fell out of the math that you could build using String Theory a Particle that led to Gravity.

Fraser:  Oh, okay let me have another shot at this.  In creating that whole collection, that Super Symmetrical set of Particles you got one Particle in that that could work for Gravity.

Pamela: Once you start to try and figure out how to build Neutrons and Protons out of Strings.

Fraser:  I see so it’s like if you can use this method where the math seems to work that allows you to build Protons and Neutrons out of these Particles, one of the happy side effects is that it also helps to explain Gravity.

Pamela: Right.  There are lots of other things that are falling out of these theories.  We start to end up with weird characteristics like the Proton, the thing that basically Atoms need in order to act like happy Atoms.  Protons decay eventually so there’s this possibility that in like ten to the 44 years or some obnoxiously large number like that Protons will start decaying in the way that like Uranium breaks down into other different things.  

Except in this case the Protons are breaking down into Energy.  This sort of causes things like those Black Holes and White Dwarfs and Lone Solid Planets without Stars that are the only things left after the Energy Death of the Universe.  They start evaporating.

Fraser:  Yeah, I know we talked about that a bit in one of our shows.  The Large Hadron Collider for starters should be able to, if we’re lucky, detect some of those heavier particles and maybe put some parameters on the Super Symmetry. 

 On that whole other collection of Particles that mirrors the Higgs Boson.  So, find the Higgs Boson and then find the Symmetrical Particle for it and maybe keep going up the chain.  Is that right?

Pamela: Yeah, that’s unfortunately the fate we have and none of the things that we know about currently will help us really understand is this String Theory or is this just a really ugly Particle Universe where these are all just stand-alone little Particles.  

Fraser:  I think that without you actually going into the math of String Theory, I hope that gives people the understanding of where String Theory comes from.  It’s a way to mathematically solve the introduction of these Super Symmetrical Particles.  

One of the happy outcomes of that is that it might predict how Gravity works with the rest of the Particles.  So is there sort of a whole other line of thinking?

Pamela: Right now, String Theory is the direction everyone is going in.  There are people who are thinking Super Symmetry doesn’t require Strings.  We don’t really have any other alternatives.  There’s a bunch of different flavors of String Theory but it really all boils down to strings.  

There are a lot of people – myself included – that are just kind of hoping that maybe some young genius will come along a new way of visualizing the Universe that might open our eyes to some sort of creative idea.  

We’ve been working on String Theory since about 1970.  There hasn’t been a major breakthrough the way Einstein said “let’s look at everything in terms of Geometry.”  We need that young genius to think out of the box and think creatively to bring all the pieces together.  

Fraser:  As I understand String Theory is going to be almost impossible to observe observationally.  

Pamela: Right.  There are a few predictions like Cosmic Strings fall out of some of the theories and the Cosmic Strings and String Theory – the use of the word String its different strings in these two cases.  

In the case of Cosmic Strings you end up with basically this high, high density line through Space where it’s basically a line where the dimensions don’t line up right. Sort of like when you get ice cracking as it freezes in a lake.  

In this case as the Universe solidified out and ended up with these faults in its structure.  It’s possible that these things exist and we might someday detect one.  There were a couple papers a few years ago of possible detections but none of them ever panned out.

Fraser:  Right as I recall these are where you might get the first moments after the Big Bang magnified in the structure of the Universe as the Universe went through its inflation and expanded any little changes, permutations would just get blown up, really magnified into the Universe, right?  You can see it.

Pamela: Right.  There are people who have predicted that if you build a telescope that has a thousand square kilometer surface area that works in the Radio, maybe you can detect other features in the Sky.  But, that’s a telescope we don’t exactly have the resources to build.

Fraser:  Yet.  [Laughter]

Pamela: Okay, so if we go and grab an Asteroid, tear it apart and turn it into a Radio telescope…right now we’re not there.  So right now we have no way to tell all of these different proofs apart.  It’s frustrating. 

Fraser:  So, in other words there are apart from Super Symmetry there are no really serious attempts to unify Gravity and the other Forces.

Pamela: This is the direction we’re going in right now – for better or worse.

Fraser:  That’s why billions have been spent to build the Large Hadron Collider and hopefully within the next couple of years, new Particles will freeze out of the energies and we’ll be able to see them.

Pamela: And what’s cool about that Large Hadron Collider is it could always turn up something we never predicted forcing us to rethink everything but giving us an experimental starting point.  And that’s just cool.

Fraser:  You know, I don’t think you were able to come up with something brand new that would win this show the Nobel Prize.  

Pamela: No, I’m much happier with telescopes than I am with math.  

Fraser:  Well then we’re going to get the Nobel Prize with something having to do with telescopes. [Laughter] We’ll go to Sweden eventually.  Thanks Pamela and thank you for wrapping your head around this. I really hope that this was able to give people some access to what the direction of the cutting edge of the Physics is going in. 

It’s not easy to understand.  I don’t understand it.  You barely understand it and you’re in it. [Laughter] I really look forward to everything that comes out of Large Hadron Collider and the Physicists working there.  I can’t wait.

Pamela: And I know we’re going to get letters on this one.  If you want to know more go read Brian Green’s book, “An Elegant Universe.” If you are a String Theorist, we’re sorry.

 

Fraser Cain:  When you were in the middle of doing your live show at Dragon Con, I was moving.  We’re all moved in, lots of boxes all over but I’ve got Internet so that’s all that really matters.

Dr. Pamela Gay: Does anything else really matter?

Fraser:  No, just the Internet.  Thank you for doing the Dragon Con Live recording.  That was really cool to have Phil and Dr. Grazier.

Pamela: Next year we really will have you there even if I have to kidnap you.

Fraser:  That’s fine, sure.  I’ll come.  Let’s move on then.  We have a big surprise coming which if we can get ourselves organized and then it will just show up in the feed.  That’s all I’m going to say on that.  

After a quick Dragon Con break, we’re back to our tour through the fundamental forces of the Universe.  We’ve covered Gravity and Electromagnetism.  Now we’re moving on to the strong and weak nuclear forces.  We didn’t think they would need separate episodes so we’re going to put them together.  

Then we’ll cap the whole series off with our quest for the search for the theory of everything and that’s when we win our Nobel Prize. [Laughter] I can’t wait.  I hear Sweden is very nice this time of year so I’m really looking forward to that.  So where do you want to start, strong or weak?

Pamela: Let’s start with strength.  Let’s start with the Strong Force.  

Fraser:  Okay, now what is the Strong Nuclear Force?

Pamela: It’s essentially what holds the nuclei of Atoms together.  If you’ve looked at a Periodic Table recently you’ll notice that it starts to get a little fuzzy around Element 100 or so.  As you start to get these really big nuclei, the Strong Force isn’t quite strong enough to hold everything together.  For smaller Atoms, it does a very good job it is in fact one of the strongest forces we have out there which is why it is called the Strong Force.  

What it essentially does is to cause little particles; Gluons in this case, fly back and forth.  As they fly back and forth, they glue the different particles together. This is an extremely useful thing because otherwise Protons and Neutrons really don’t have any reason to stick together with the Electrostatic Force.  One is charged the other is neutral.  You have to have some other force to hold these pieces together.  

Fraser:  Right, so at the center of the Atom, you have your Protons and your Neutrons and they are being bound up together by the Strong Force.  But not Electrons, right?  

Pamela: No, the Electrons come in using strictly Electrostatic Force.  

Fraser:  Okay.  I know you can break up Protons and Neutrons into more elementary particles.  Is the Strong Force holding those elementary particles together as well?

Pamela: This is where we start to get into a sub-part of the Strong Force sometimes referred to as the Color Force.  Protons and Neutrons are made up of different flavors of Quarks.  You have up and down are the two stable Quarks that go into making pretty much everything around us stick up.  So your Protons and Neutrons are both made up of combinations of up and down.  

The Color Force is part of what gets in as its own form of the Pauli Exclusion Principle.  You have this idea with Electrons that you can only have a spin up and a spin down orbital.  If any of you have taken Chemistry, this is what explains the entire crazy orbitals of Atoms thing that you had to memorize in tenth or eleventh grade.  

With Quarks you have the same thing going on where you can’t have three Quarks that are the same color all in one Proton.  Instead you have to have combinations of colors.  Just for the sake of having names they’re generally referred to as primary colors but they’re not a real color.  There’s no real color involved, we just needed a word.  

So instead of making up a word, we decided to abuse a word. With the Strong Force we have the Protons and Neutrons are all made up of Quarks and the Quarks are held together with the Color Force which is part of the Strong Force.

Fraser:  Now you said that there are Gluons zipping back and forth between the particles and that’s what is communicating the Force, right?

Pamela: And this is actually also what limits the Force to such a short distance.  Gluons have mass and because Gluons have mass the Heisenberg Uncertainty Principle which says you can either know where something is or how fast something is moving and it gets involved in other things.  

It says that once you end up with something as heavy as a Gluon you’re limited in how far you can go, how far you can interact to about ten to the fifteenth of a meter.  So, that’s a zero followed by fourteen more zeros and a one.  Zero point 14 zeros 1 meter is the distance at which a Gluon is capable of holding things together.

Fraser:  And Gluons have actually been isolated in Particle Accelerators, right?

Pamela: They were first detected back in 1979 and since then we have been turning them up in various different places.  Stanford Linear Accelerators played with them; Brickhaven National Laboratories has played with them. All sorts of different Colliders and Accelerators have played with them. We know they’re there.  We can quantify different characteristics about them.  This part of Physics we’re quite certain about.

Fraser:  So if you then were able to intercept Gluons that were communicating back and forth between a Proton and a Neutron they would fall apart if you were able to sort of siphon away the Gluons?

Pamela: Well that’s kind of the wrong way to think about it.  All these things that are communicating for us can also exist independently.  For instance with the Electromagnetic Force that we covered a couple weeks ago, you have Photons moving back and forth.  

In some cases we refer to them as Virtual Photons because you don’t really see them.  It is these Photons that are communicating with the Electric Fields and the Magnetic Fields.  

Photons can get shot out of a laser beam and they are quite happy to exist as stand-alone particles.  If you create enough energy in some sort of collision then out of that energy you can start to get particles just materializing.  So, in this case we have something with a mass that is a little bit less than a few mega-electron volts.  

We just need to collide something so that you end up with more energy than that with the correct decay rates where you end up with Gluons as part of this energy condensing down the stable particles.  They can exist without having to be trapped inside of a Nucleus.

Fraser:  Right.  So what is the strength of this Force compared to say Gravity?

Pamela: In general the way we talk about Forces, it’s easier to not say, “this has this many Newtons of Force.” But we instead look at the relative strengths of Forces.  So, let’s say, because it’s true, that the Strong Force is the strongest of all the forces.  Well, then the Electromagnetic Force between two particles that are nearby compared to the Strong Force it has a strength of one one hundred and thirty-seventh of that.  

So if you stick two Protons next to each other in the Nucleus of an Atom, the Strong Force holds them together with a Force we’re going to call one.  But at the same time because they’re both Protons they’re trying to repel each other.  Likes repel likes in this case.  

The Force that is trying to push them apart is one divided by one hundred thirty-seven times smaller than that Strong Force.  Now, at the same time, if Gravity is trying to hold those two Protons together, here we get into ridiculously small numbers.  

Those two Protons trying to push each other together compared to the strength of the Strong Force holding them together is six times ten to the negative thirty-ninth.  So, you take a zero and you take a one, you put thirty-eight zeros and then a six and that is how much weaker this Force is.  

Fraser:  Right, and so the equivalent to think of an analogy is like you have magnets with two pointing towards North, you take the two North sides of your magnet and just jam them together.  [Laughter]  You can hold the magnet together with the force of your arms.   

You can overcome the Magnetic Force there and then as soon as you let go of the magnet they pop away from each other.  Even though Gravity is pulling the Protons together, the Electrostatic Force is pushing them apart.  The Strong Force is dominating it and it’s the thing that’s really holding them together.  

Pamela: Here there reason that we’re able to see Protons repelling each other at other distances is as soon as you get past that ten to the negative fifteenth of a meter the Protons no longer care about the Strong Force.  So in order to build the Nuclei of Atoms you have to get within this very limited distance. 

You have to slam the Protons together the same way you might slam two magnets that are trying to repel each other apart together.  Once you get them close enough, the Strong Force overcomes.  

Fraser:  We’ve covered the Strong Force, so why don’t we switch over and learn about the Weak Force, what is it?

Pamela: The Weak Force is how we look at Atoms and we observe them decay and we had to explain this somehow.  What is it that is causing all of a sudden one Atom decides it is going to transform itself into something that has the same number of stuff in the center, the same number of Protons plus Neutrons in the center?  

But all of a sudden, one of the Protons decides it is going to become a Neutron and thus the Atom changes names while maintaining very close to the same weight.  This is beta decay.

Fraser:  Give us an example of something that might decay.

Pamela: For instance if you have a Plutonium 15, this is one of the things that crops up in all sorts of different radioactive experiments.  That will end up decaying to Strontium 16.

So, you’ve changed the number of Protons, increased the number of Protons, decreased the number of Neutrons and along the way you’ve given off an Electron and you’ve given off an Electron Neutrino.  This helps keep everything balanced out.

Fraser:  Right.  The amount of energy in the whole system stays the same.

Pamela: Charge is conserved so you went from the Neutron to having a Proton and an Electron and then there’s an Electron Neutrino to help things out.

Fraser:  So the math works; like you could sit down and add up all the particles before in the energy and add up all the particles after in the energy and it all balances back out again.

Pamela: Just to get the details correct, it is an Electron and an anti-Electron Neutrino.  Those two come in pairs together.

Fraser:  Right, but I guess the question then is why?  Why does this just spontaneously go ‘pop’? [Laughter] And then you have a completely different element.

Pamela: It’s the constant quest to find the lowest possible energy level.  Neutrons in general aren’t the most stable of things.  If you leave a Neutron alone on a shelf for fifteen minutes it will decide it wants to be a Proton, and Electron and an anti-Electron Neutrino.  

It’s kinda hard to leave a Neutron alone on a shelf but if you could, and they do this in various types of experiments, in Atoms usually states that have lower energy are better balanced.  It gets a better distribution of particles in the center such that it is at a lower energy level.  

In the quest to achieve the lower energy level, you end up with Protons changing over to Neutrons or sometimes the reverse.  It depends on the particular reaction.  It just happens to be that it is the Weak Force that makes this happen.  What’s actually happening is that you have Quarks changing from up to down.  

So, as you go from that Plutonium to that Strontium, what is happening is one of the down Quarks transforms into and up Quark.  That gives us the Neutron going into a Proton and it’s that change from down to up that is triggered by the Electro Weak Force. 

Fraser:  Then how was the Weak Force discovered?

Pamela: There is first of all just the fact that WOW we have things decaying.  We have different particles where we see Electrons coming off; we see the nature of the Atoms changing.  Radioactive decay happens and so we had to explain what was going on.  

As we built the standard model of Particle Physics where we saw that Protons and Neutrons are made up of Quarks we realized that somehow a Proton had to change into a Neutron or vice versa depending on the particular reaction.  

This meant that somehow we had to conserve all these different qualities and we needed something to mediate all of this and that’s where we started looking for the Weak Force.  It actually wasn’t until the 1980s that we finally started to be able to find the particles that mediate all of this.  That’s the amazing thing about this, for most of our listeners. This is stuff that has happened in all of our lifetimes.  

In the case of the Weak Force, it is moderated by what we call Vector Bosons.  In this case they have masses of greater than eighty giga-Electron volts which is a lot, not that people tend to think in giga-Electron volts.  This large mass, this mass that is a lot bigger than the mass of the Gluons that mediate the Strong Force means that this particular Force only acts over distances smaller than a Proton.  It can only affect things at the particle size.  

What are mediating this are the W and Z Bosons.  So we again have Bosons and these Bosons were detected in the 1980s, again by creating really high energy experiments where the energy fell out into a variety of different particles that in the cascade of energy and the stable particles along the way the Vector Bosons became apparent. 

Fraser:  That seems quite amazing to me that you could perform the big collision, freeze out the energy into the particles and then have a particle bounce against one of your detectors and then say: “Hey you know, that’s probably the particle that communicates the Weak Force.”  [Laughter]  

I’m trying to think how they would do that.  Did the Scientists then in their calculations from one of their theories say, “if a particle of this amount of energy and mass bonks against your detector that’s what it has to be”?

Pamela: It’s actually even more subtle than that. What you do is you collide things violently inside of a detector.  Often you’ll end up with essentially donut shaped accelerator rings. You have two rings running parallel to each other except the particles in one are going clockwise and the particles in the other are going counterclockwise.  

Then you feed them together inside of your Detector such that you’re forcing two different streams of particles to collide inside your Detector.  Then as this amazing release of energy where you have the energy that is in the mass and the energy that is in the velocity of these particles all coming together.  This energy then freezes back out into a cascade of particles that in many Detectors are now moving through magnetic fields that have been put in place.  

How the particles move through the magnetic fields is a function of what is their mass, what is their velocity and what is their charge.  By looking at what are often really neat curly Qs, what are really neat bent paths through these magnetic or electric fields, we’re able to backtrack through well, this seems to have had this reaction time. We can figure out the velocity it lasted this long.  It curved this much in that amount of time which means it probably had this amount of charge.  

We look at all of these different characteristics and look at how they moved through the Detectors in a variety of different ways.  Sometimes fiber optics is being used; sometimes you’re doing this in gases.  There are all different ways that you can detect these different particles. 

It’s by looking at their paths at different points that we’re able to work out what the masses had to have been, what the charges had to have been and figure out what it is exactly that we’re looking at.  Sometimes we’re not entirely sure.  There’s been some, “well it could have been”, observations of something that might have been the Higgs Boson but no one believes the results.  

We know that there’s something there but we’re not positive what it is because the results weren’t solid enough.  There weren’t enough particles produced, there wasn’t enough signal in the Detector…It’s a frustrating game.  

It took until I was an undergrad at Michigan State for the final of the Quarks to be found just because it was such a massive particle that trying to get enough energy to generate it is a cascade effect.  You can’t just say “I need this many giga electron volts”, and it will create a top Quark.  You have to overshoot and see what falls out of the energy that condenses down.

Fraser:  Well we’re only about a week away from them firing up the Large Hadron Collider and the search for the particles begin and not the destruction of the Earth.

Pamela: No, Earth is not going to be destroyed.

Fraser:  It’s a search for particles.  I guess the question is, how are they connected?  They’re both called Nuclear Forests.  

Pamela: At extremely high energies, things start to all unify.  We’re still trying to understand all of this.  There are so many things about Particle Physics that we’re still working to try and understand.  

With the Standard Model of Particle Physics as you move toward higher and higher energies, there seems to be a point and a density at which things are crammed together to the point that you achieve the energies that go through the Strong Force and the Weak Force combined and act in one way.  

But at this point you also sort of have the soup so talking about individual Atoms starts to get trickier.  This is how we’re slowly trying to move towards a grand unified theory.  This is something that we’re going to talk about more next week as we start to talk about how we’re going to get our Nobel Prize, which really we won’t.  We’re just going to sorta repeat what other people have said.

Fraser:  Hey, that’s quitter talk! [Laughter]  We are so going to get a Nobel Prize.

Pamela: Right now what we talk about is the Electroweak Unification and there actually has already been a Nobel Prize for this.  We discovered the WZ 22:33particles, the Intermediate Vector Bosons that convey these Forces back in 1983.  

There is a Nobel Prize given to Weinberg, Salam and Glashow – I have probably mispronounced their names terribly. Weinberg is the only one I’ve met, so the other two haven’t told me yet how they say their names.  

It’s thought that at high temperatures where the energy of all these particles colliding one against the other against the other is about 100 giga electron volts.  At these extremely high energies, the weak and electromagnetic interactions all start to be a manifestation of a single Force.  

We’re still working to try and put these things together.  Our basic picture is at energies where Quarks start to be their own separate happy little particles we have four Forces acting completely separate from one another.  

But, as you start to get to energies of about one hundred giga electron volts, which we actually had when the Universe had a temperature of – and pardon the scientific notation – about ten to the fifteenth Kelvin.  You don’t say degrees because Kelvin is its own special thing.  At one followed by fifteen zeros Kelvin the Universe was so hot and so dense that the Electromagnetic and the Electroweak Forces combined into one Electroweak Force.  This occurred when the Universe was a little bit younger than ten to the negative tenth of a second.

Fraser:  So, early on.

Pamela: Yeah. [Laughter] Well before the first second it was done transpiring.  By second one yeah, everything was nice and happy and we had Quarks were separate and all the Forces were separate.  

But early on at that little less than ten to the negative tenth of a second, we only had three forces:  the Electroweak, the Strong and the Gravity.  Now if you keep going a little bit further back in time and get to so it’s about ten to the 27 Kelvin, at that point we start to be able to bring the Electroweak and the Strong Force together as well.  

Where we get lost is when we try and bring in Gravity.  The details of how you unify the Electroweak and the Strong Force we’re really not so sure on, but we’re pretty sure it happens.  We’re working to try and build a model that explains magnetism, explains electricity, explains Beta decay, and explains how it is that the Nucleus itself holds itself together and why it is that we don’t end up with Atoms the size of the Solar System.  Why is it that we have a finite size to the nucleus of an Atom?  The finite size of the Nucleus of an Atom comes from the Strong Force having a limited distance.  

The Beta decay comes from the Weak Force. Electromagnetism is what brings the Electrons and the Protons together and allows molecules to form and allows refrigerator magnets to adhere themselves to refrigerators.  One of the neat side effects of trying to unify these three Forces, the Electromagnetic, Weak and Strong Forces is pretty much all of the theories out there predict that Protons decay.  There is no observational evidence for this.  

In fact, all observational evidence points towards Protons really not wanting to decay.  If they do, they do it over extremely long lifetimes.  But if Protons do decay and our current ideas on how you might unify these three Forces are true, then trillions of years from now when all the Stars are dead, when all the Black Holes are sitting there happily evaporating away.  When maybe there are one or two dead cold White Dwarfs floating around but maybe not.  Everything that is left, any Protons that are out there are going to start to decay. 

That means that even any Rogue White Dwarf Stars that just might happen to have survived are going to evaporate.  Any Rogue Planets that might have survived are also going to decay away as the Protons simply become energy.  

That’s even a more depressing future than some of the ones we’ve looked at before, but we don’t know if this is true.

Fraser:  I think it’s equally as depressing. [Laughter] 

Pamela: You think so.

Fraser:  I think they’re really just exactly the same, yes.  [Laughter]  Okay, well and you’re already starting to ruin next week’s shows.  I have to stop you.  

Next week we will talk about the quest and the discoveries that were made and that were to bring everything together.  We’ll probably have another look at String Theory just because that’s part of it.

 

Fraser Cain: Let's get on with the show then. Everyone seems to like our series, our tour through the Solar System, our information about Mars. We've got a new series for you. I think people keep wondering about when we are going to run out of topics. Well, here you go.
 
We're going to handle all the forces of the Universe and this week we're going to do gravity. We haven't covered that show yet and here were are a hundred plus shows in. We're going to start with gravity, which is a force you're most familiar with. We know gravity happens when masses attract one another and we can calculate its effect with exquisite precision.
 
However, you might be surprised to know that scientists have no idea why gravity happens at all. Pamela, let's go back and just image you're in your class and you will be presenting gravity to people. Where do you typically start?

Dr. Pamela Gay: I usually drop something loud because that gets their attention. But I won't do that to our pod cast listeners because [Laughter] that might be cruel to their eardrums if they're wearing headphones.

Fraser: Preston, resist the urge to make a loud noise. [Laughter] He's our Editor. Okay.

Pamela: The way that we're most aware of gravity is things fall. We fall. We fall upstairs, downstairs and you always fall toward the center of the Earth. Keys fall, books fall, and I've fallen off of horses. Falling is one of these things that people have been aware of since they first stood up.
 
The question is why? Why is it that I always fall toward the ground and not toward the sky? Why is it that people on the North Pole and the South Pole both stay adhered to the surface of the planet and don't go flying off into Outer Space?

Fraser: You can imagine that gravity is such an all-pervasive force that ancient peoples almost didn't even think about it. You know? It's also like why when I breathe is there air in my lungs?
 
It's because gravity is holding the atmosphere next to the planet. But it's not something that you would even consider. So when did people start to realize there was something going on?

Pamela: It was often addressed as a philosophical question. Why down and not up? Why don't we go into the sky? This became even more troubling when we discovered the planet is round.
 
Galileo did our first scientific investigations of gravity. Everyone has heard the stories of Galileo dropping things off the Leaning Tower of Pisa. No one knows if that actually happened. If it happened, he certainly didn't document it. Galileo was one of these people who documented everything.
 
But, what he did do was roll balls down inclines, which doesn't sound all that exciting but prior to Galileo's investigations we had Aristotle's ruling the days ruling the day saying that objects started in motion always come to a stop. Everything comes to rest.
 
That was the way we viewed the Universe because friction does cause everything on the planet Earth to generally stop. But Galileo, through very careful investigations, realized objects of different masses, shapes and sizes only fall differently as a result of how they interact with air.
 
He realized that if you have an object moving across a smooth enough surface and it goes down an incline, it would go up an incline to the exact same height on the other side. He was able to start saying, gravity is this thing that is causing the ball to go down the incline and the go up the other side.

Fraser: Now as I remember Galileo used ramps as a way to slow the whole process down. That is was impossible to measure if you just drop things but if you put things on very slanted inclines there was a way that he could actually start to measure how long things were taking to drop.

Pamela: He was actually using water clocks. This was a really cool way to basically say if you have a bucket filled with water with a little tiny hole in it and there is a large enough surface area to that bucket – because surface area plays a role in how fluids flow – and it's a short enough period of time then you open up the spicket on the bucket and let the water start dropping out into the Galileo equivalent of a graduated cylinder. You measure the volume of water that comes out while the ball is rolling down the incline.
 
It's a surrogate for measuring time. If you assume that one drop of water falls per one second and you can figure out the volume of one drop of water, the volume becomes a measure of time. He was able to figure out this acceleration measurement for how balls fall down. They have this speed for the first second, this much larger speed for the second second; an even larger speed for the third second.
 
He was able to figure out all of this related to the angle of the incline, all sorts of really cool math. He did all of this using a water clock that he basically started and stopped by starting and stopping the water.

Fraser: And so the conclusion that Galileo came to was that the force of gravity is acceleration. I guess people always intuitively understood that. You fall off of a higher drop and you're going to get hurt worse. [Laughter] But I don't think they realized exactly how that worked.

Pamela: One of the coolest things about what Galileo did was he put together the whole notion that any two objects should fall at the same rate once you take into account air resistance.
 
This had actually been somewhat confusing before because if you imagine a barbell falling, if the rate at which something falls is a function of mass then if you replace the bar in the center of the barbell with a piece of string how does that know to fall at the same speed as the two bars connected solidly versus why would two balls without a string between them fall at a completely different rate.

Fraser: Right and you can always go back to that example of a ball versus a feather, right? I guess they thought that the feather was lighter and so it would fall more slowly while the ball would fall more quickly.

Pamela: Yes, and then you extend this idea out to small child falls slower than large man. Please don't do that experiment. It didn't really make sense though when you consider how does a man holding a child fall? Don't do that experiment either.
 
Galileo basically determined it was just air, its okay and moved on. We still don't know why though. This not knowing why was a problem that we continued to have for a while. Kepler came along and figured out equations to describe the motions of the planets. He didn't know why they were doing it but we had equations.
 
Galileo described mathematically how objects go down inclines and go up the other side but didn't know why. It was Newton who came along and according to the story saw an apple falls…

Fraser: Did this really happen – oh, he didn't get hit on the head, right? [Laughter]

Pamela: No, apparently not. I mean, who knows? But according to the story Newton saw an apple fall, looked up and saw the Moon and decided that the Moon was falling. It was probably a more complicated train of logic.
 
He worked out that if the Moon was so far away and a certain size – well we don't really need the size that much – but if the Moon is this far away, and the apple is this far away and we look at how they're falling and the Earth is this size…..
 
Using lots of cool mathematics that you can actually do with basic algebra, he was able to figure out that the Moon was just falling around the planet and managing to miss it as it goes.

Fraser: I remember the thought experiment for this was where you imagine that you have a cannon and you're firing it sideways and the ball hits the ground a few hundred meters away. Then you tilt the cannon back and you have much more powerful cannon and you shoot it and the ball will land further downfield.
 
You eventually get to the point where the cannon is strong enough that the ball just goes all the way around the Earth and lands back on the guy who fires it. Eventually you can keep shooting it harder and harder until the ball just goes all the way around and it's falling but it's like the Earth just keeps moving out of the way.

Pamela: Newton was able to take that idea and go: "Oh, Moon falling; oh, Earth falling around Sun." All of a sudden what we see is everything is falling but the curvature of its fall doesn't allow it to ever make it to the object it is falling toward. That is a kinda neat image and he had really neat math to go with it.
 
Then unfortunately there are things like oh, the planet Mercury that screwed things up. It was all well and good; we were able to find Uranus because of Newton's applications.
 
There were two different scientists, two different mathematicians one in England who did lots of equations and threw out lots of possibilities and one in France, who basically did one calculation, threw out one possibility.
 
Then an observer went out and looked at the Frenchman's coordinates and discovered a new planet. All of a sudden Uranus' orbit made sense. But, Mercury's didn't so we waited around trying to figure out what is wrong with gravity.
 
Then Einstein came along. Einstein was able to give a reason for gravity existing. Look at gravity as a curvature to the Space Time Continuum.

Fraser: Whoa! Explain that.

Pamela: Yeah, I know, it's a kinda big jump.

Fraser: Like I'm sure people thought well that was helpful. [Laughter] Thanks Einstein.

Pamela: Yeah, he just sorta reformulated how you're supposed to visualize all of everything. He came along and said basically imagine Space as more dimensions such that the gridlines of our three-dimensional grid get tightly packed as you get closer to the Sun because you're falling in toward the Sun.

Fraser: I think the analogy we always use is like a rubber sheet with a bowling ball on it.

Pamela: You can imagine that in our flattened Universe, our flattened Solar System, the Sun creates a deep pocket in our plastic sheet of Space. If you've ever seen crazy skateboarders, they can get themselves going around the edges of bowls.
 
If you watch crazy bicyclists, they'll get themselves going around the inside of velodromes which are curved surfaces. You can imagine the planet Earth as it rolls along Space moving around the rim of some sort of Cosmic Velodrome where it is the Sun that defines the center of the particular curve that we're orbiting around in.

Fraser: Just to backtrack for a second what exactly was the problem with Mercury?

Pamela: Its orbit wasn't going at the correct rate. We have an entire show on Relativity that people can go back and listen to that brings this up. Basically the problem is that its orbit precesses in a way that we couldn't fully account for.

Fraser: Ah, and the word precess?

Pamela: That means that it's an ellipse and where the end of the ellipse is changes over time.

Fraser: Okay, no I see. You've got like an oval like a loop and Mercury is going around the loop and you're sort of tracing this oval but the oval's position is slowly rotating like a Spirograph.

Pamela: Yeah, the kid's toy.

Fraser: Okay and so the position of where that oval of Mercury's orbit was supposed to be didn't match up what Newton had predicted. And Einstein said that's because of Space Time Continuum and all that junk.

Pamela: Right and then some mathematician came along and beat them with a stick and said it's an ellipse not an oval because mathematicians like to do that. So we have this problem with Newton's understanding of gravity and Einstein came along and announced he had a new formulation. It's all a curvature of Space. Gravity is nothing more than geometry.
 
The problem is gravity breaks at the beginning of the Universe and in centers of Black Holes. Things just get so dense that infinity signs start popping up and dividing by zeros starts popping up and much badness occurs.
 
About the time that people decided this is bad and math can't handle this, we also started building a standard model of particle physics where we look at other forces – which we will talk about in succeeding shows – such as electricity and magnetism, which is the electromagnetic force.
 
We started looking at them and realized there were photons, particles of light! They carry these forces. They cause the electric force they cause the magnetic force. The electromagnetic is one force.
 
We realized other forces, the weak force, the strong force, also had little particles we call bosons that walk around at extraordinarily high speeds and carry the force with them and communicate from one point to another.
 
In this particle physics way of viewing Space and time in particle physics, people began to say there must be some particle, some boson – we called it a graviton – that is the little particle that carries the force of gravity that communicates gravity from one object to another.
 
This causes objects to realize that an object in one place has moved and the realization that this move affects the other objects to be affected differently by the one that has moved.
 
It raises all sorts of all interesting questions like how fast is gravity communicated. All these questions pointed at this little particle, this graviton that we can't detect. This is one of the biggest annoyances in particle physics.

Fraser: Right, so we've moved on to the question that a 4 year-old would ask, right? Why is there gravity? [Laughter]

Pamela: And the answer if you listen to Einstein is it's the curvature of Space and time.

Fraser: But why is there a curvature of Space and time?

Pamela: Because there is. Because mass for reasons that we can't really explain causes the space around it to essentially grow hills and valleys that we can't see except in the motions of objects.

Fraser: But WHY?

Pamela: BECAUSE [Laughter] this is the way our Universe is ….

Fraser: [Laughter] The point you were saying is that the thought was maybe there are particles communicating back and forth somehow. And that's the attraction, right, is our defining the curvature of Space and we have these gravitons.

Pamela: That's the crazy thing though, once you invoke the gravitons you no longer need to invoke the curvature of Space. We now have two views.

Fraser: Right, the little rubber bands going almost going back and forth.

Pamela: Yeah and the crazy thing about this graviton notion is first of all it is a particle that has no mass because it moves at the speed of light as near as we can tell. There are gravitons flying through us all the time.
 
If we built a detector the size of Jupiter and planted it next to something like a neutron star we'd have to wait years before maybe one graviton caused something to happen in the detector. We couldn't tell the difference between that event and what neutrinos cause.
 
Neutrinos really don't interact with anything either so we can't ever really detect gravitons, except maybe through radiation. This is one of the cool things about particle physics – particles are little blobs of stuff but they're also waves.
 
We talked about the wave particle duality in a past episode. When we look out at things like pairs of neutron stars orbiting one another we see their orbits changing over time.
 
This is gravitational radiation at a certain level carrying energy away. This is gravity waves, something that LIGO and LISA are hoping to be able to detect. We are still working to get there.

Fraser: Okay so if the particle theory is right, if there are these gravitons then you have this gravitational radiation that would be given off. It should in some way be detected through some mechanism, right?

Pamela: Yeah through gravity waves.

Fraser: Right and that's where we get the whole thing about gravity waves which I think we've done a show on that as well. So that's the one camp and I guess would there be a way that you could detect these gravitons in a particle accelerator?

Pamela: No.

Fraser: No. Not at all? No chance?

Pamela: No.

Fraser: Not even theoretically? [Laughter] Okay, fine! I won't go with that line of questioning anymore. Then the competing thought is that it's just purely geometry. That is the way you might as well ask why are there triangles.

Pamela: The problem is that we know that our understanding of particle physics is incomplete and we know that the geometric understanding of gravity is incomplete because we can't describe the insides of Black Holes without math breaking. We can't describe the earliest moments of the Universe without math breaking.
 
Having gone from basically philosophical understandings of why things fall to mathematical descriptions of how things accelerate down inclines to Kepler's equations describing planetary motion to Newton's formulation of the Laws of Physics – or at least the Laws of Kinematics and Gravity – to Einstein's formulations of Relativity, we've been building and building a more comprehensive view of gravity. But we're still not complete.
 
We know that there still needs to be some way to unite Quantum Mechanics and gravity and actually be able to write down equations that describe the centers of Black Holes, to describe the earliest moments of the Universe.
 
We're not there yet. There needs to be a new brilliant person born into the Universe, or at least born onto the planet Earth. Someone on another planet might already have figured this all out.

Fraser: Now how fast does gravity move? I know that Einstein made some predictions.

Pamela: The belief – and there is some evidence for this – is that gravity propagates at the speed of light. That if you suddenly blink the Sun into some other part of Space using a transporter beam technology that will never exist, the Earth would merrily continue happily orbiting as if nothing had happened for 8 minutes.
 
Then at the end of that time, we would cease to receive light and we would start moving in a straight line instead of on the orbit that we're presently in because the Sun's light would stop hitting us and the Sun's gravitons would stop communicating with us that we should bend.

Fraser: What is the mechanism that they're trying to test this out? I guess gravity waves is one?

Pamela: Gravity waves are one. A neat experiment that didn't work – at least the theorists are saying the interpretation is wrong – was trying to look at how does light bend around objects?
 
And if that object that it's bending around happens to be moving can we separate out the object's motion and the rate at which light bends around it and learn anything meaningful?
 
There is a set of observations done in I believe 2002 where they looked at how Quasar light bent around Jupiter as Jupiter moved between a series of Quasars. The interpretations were messy.
 
The observations didn't have high enough accuracy. People are trying to find new and interesting experimental ways and like you said, we're looking for gravity waves.

Fraser: So the hope is that as a heavy object moves in front of some distant bright object you'll get the light beam tweaked, not instantaneously but at the speed at which the gravity is propagating out from the planet itself.

Pamela: Yeah.

Fraser: Okay, now I remember reading somewhere that gravity even though we think it is really strong, it's actually kind of weak isn't it?

Pamela: It is over large distances the force that tends to have the most affect on the Universe. On small scales, electrons and protons do not care about the gravitational pull of the one on the other.
 
All they care about is the electrical force. On small scales with small masses it's extremely weak and the other three forces all dominate on the smallest scales.

Fraser: Sure, you could pick up an object from a table – pick up a coin from a table – and the nuclear force holding the atoms in your hand together vastly overpower the meager force of the entire Earth pulling on that coin on the table and just your fingers can overcome that just the force holding your fingers together.
 
Stick a fridge magnet on the fridge and bang you've got that little magnet completely overpowering the force of the Earth. It's not until you get neutron stars in Black Holes where those forces are gone.

Pamela: An interesting thought experiment that basically came out of one of my classmate's mathematical errors when I was in graduate school was to just sort out what is the self-gravity of the human body?
 
If you take a human body and pull all of its atoms apart so that it's only held together with gravity all it would take is a breath to dispel all those atoms and shatter the human form.
 
So, it's all the chemical bonds, all the molecular bonds, all these things that are because of the strong force, the weak force, the electromagnetic force, that hold you and I together and gravity that holds us on the planet.
 
Really, it takes a lot to tear apart a chemical bond and it's only on the largest scales where chemistry no longer really has an effect that gravity has a chance to get noticed.

Fraser: Well, I think that covers our gravity side this week. Next week we will move on to the Electromagnetic Force and then we'll do the Strong Nuclear Force and the Weak Force and then maybe on the last episode – the fifth episode of our four-part series – [Laughter] we'll try and pull it all together.
 
We'll talk about the search for the grand unified theory. Pamela if you figure it out – Nobel Prize.

Pamela: You know, it's something to aim for but I don't think we're quite going to make it.

Fraser: Just do your research, [Laughter] get all your show notes prepared and if the solution seems to present itself then by all means put it in the show and we'll look forward to a Nobel Prize. [Laughter]

 

Fraser Cain: Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.
 
Before we get on to it, let's talk about pronunciation. I said it Lagr-ahunge points. Is that okay?
 

Dr. Pamela Gay: I have heard it said Lagr-ahunge points, Lagr-ahungian points, Lug-range points and Lug-range-ian points. So you know – go with it. Say whatever your local dialect dictates is correct.
 

Fraser: They're acceptable.
 

Pamela: They're all acceptable.
 

Fraser: All right. Maybe someone from France can jump in and give us the most correct pronunciation.
 
So, where do these come from?
 

Pamela: The basic idea is if you have a two-body system with two giant things – where giant can be defined on small scales, such as the Moon and the Earth would qualify, the Earth and the Sun would qualify – then you throw in something small (a test particle, a frozen pea, a satellite), you can look to see how the smaller object is going to gravitationally interact with the larger object.
 

Fraser: The point being this object isn't going to be pulling at the other two objects with its gravity. Its gravity is negligible in the situation.
 

Pamela: Yeah. It has no pull on the Earth or the Sun – no pull on the two giant objects that we're worried about.
 
When you start to probe all the different places you can stick this test particle, there are some places that when you stick it there, it stays. In general, if you take an object and you put it on an orbit around the Sun that's bigger than the Earth's orbit, it's going to go around the Sun a little bit more slowly. When you stick it on an orbit that's inside of the Earth's orbit from the Sun, it's going to go around the Sun more quickly than the Earth.
 

Fraser: If you have an object, which you've got the Sun and the Earth, the interaction of the Earth is going to mess with it, right?
 

Pamela: That's where the magic happens. There are a few specific points – five of them to be exact – that if you stick an object exactly in one of these five points, the combined gravitational attraction of the Earth and the Sun gang up on this object to keep it moving in lockstep with the Earth as it goes around the Sun. If you're dealing with the Moon-Earth system, you can stick things in the five specific spots that come from the combination of the Earth and the Moon so that it sticks there, following the Moon in its orbit around the Earth in lockstep.
 

Fraser: Hold on, so you're already said places where its stable. What if you're not in one of those places?
 

Pamela: if you're not in one of those places, you're happily going to end up in some sort of orbit going around the object, but you're not going to be synced up with anything. For instance, the space shuttle at the space station right now is zipping around the planet every 90-100 minutes. The moon, on the other hand, takes 20-some-odd days to go around the planet.
 
If I move the space shuttle and the space station its attached to, out into gradually further and further orbits, and position it in just the right orbit in just the right period of time, even though it's not as far away from the Earth as the moon, it would still go around the Earth with the same orbital period as the moon. It's in one of these magical Lagrangian spots where the potential and kinetic energies of the systems balance out just right to keep it there.
 

Fraser: Right. If you slowly move it out and don't necessarily have it in a perfect circular orbit, it might get caught into some weird, gravitational dance, and get thrown out of the system or hurled into the Earth or sent into orbit around the Sun, or…
 

Pamela: Most likely it will just end up in a very elliptical orbit around the Earth.
 

Fraser: Right, get turned into very elliptical orbits. So if you have a little space rock that comes into our system, in most situations it's going to crash into the Earth, crash into the Moon, get skewed away into an elliptical orbit or…
 

Pamela: It's just going to be another satellite.
 

Fraser: Yeah. It's not going to stop and pause and stick around. Let's talk, then, about these Lagrange points. How do they work?
 

Pamela: There are five of them that are ever so creatively named: L1, L2, L3, L4 and, well, L5.
 

Fraser: And that's Lagrange-1, etc. Right?
 

Pamela: Right. So Lagrange-1 is the point between the two masses that stays in sync with the smaller object. For instance with the Earth-Sun system, this is the point in space nearer the Earth that, if an object is plunked down in L1, it goes around the Sun in the same just about 365 day period that the Earth has. We will always have this constant line going Sun-object-Earth lined up like little soldiers.
 

Fraser: So if we take that object and put it closer to the Sun, it's going to be travelling at a faster orbit like Venus, so it will go around the Sun faster than the Earth will.
 

Pamela: Normally.
 

Fraser: Yeah. If we move a little more toward the Earth from that point, it will still be going faster than the Earth will, but it will actually be going slower than that point. Right? If that makes any sense. You're saying it goes in lockstep with the planet, so…
 

Pamela: Here's a different way of looking at it that's a little bit weird. If I take an object and put it the exact same distance from the Sun as L1, but I plunk it down so the Earth, Sun and this object form a right angle from above, that object is going to start going around the Sun with its own period that is way shorter than one Earth year.
 

Fraser: Right.
 

Pamela: It's just going to be heading around following Kepler's laws.
 

Fraser: Right.
 

Pamela: Now if I take that object and take it at that specific distance from the Sun at just the right moment so that you have Earth, Sun and this object in a straight line with the object between the Earth and the Sun, and then I give it just the right amount of momentum, it's going to travel around the Sun with the exact same orbital period as the Earth.
 

Fraser: Right. I'm going to make a guess here, but the point is the Earth is tugging on it and providing just that extra little bit of oomph to keep it going around at that speed.
 

Pamela: The Earth is giving it that extra pull. Well, not so much an oomph as it's combating the Sun's pull. It's because of the Sun's mass that the object would normally be zipping around so quickly. If you have the Earth pulling in the exact opposite direction, in a way philosophically, it's like you removed a chunk of the Sun. if you make the Sun smaller you can orbit it more slowly.
 
By having the Earth there, pulling away with its own gravitational pull, it slows down the velocity that's needed to stay in a nice stable orbit around the Sun.
 

Fraser: I've got an analogy. If you're diving and you're going to wear a weight belt to keep yourself perfectly stable, then if you want to go back up you could attach a balloon behind you that would start pulling you back up. You could balance it out with weights and balloons, with the Sun being the weights and the balloons being the Earth. The right spot is your Lagrange point. 1
 

Pamela: Just like with the weights and the balloons, you have to get it exactly right or you're either constantly floating or constantly sinking. With the Lagrange points, especially with the first three, you have to get it exactly right, or you're going to go flying out of it. These aren't stable locations to be. The spaceships we stick there have to have their own engines and they're constantly making their own corrections to stay in these places.
 

Fraser: Okay, so these spots, although you can keep going at that same orbital speed, they're not stable. It's almost like you're at the top of the point of a needle, and you can fall any direction and have to fall out of that Lagrange point. The only way to stay there is to keep using your rockets.
 

Pamela: Mathematically they're what we call saddle-points. In certain directions, you're going to fall right back down to the Lagrange space. If you're taking a marble and trying to balance a marble on a western saddle, if you move it toward the head or butt of the horse, the marble will roll right back to the centre of the horse's back. If you bump the marble left or right, it's fallen off the horse. I know people (including myself) who have had the same experience of falling off the horse.
 
These are semi-stable positions. The spaceships we stick there have engines that make corrections to stay put. At the same time, it's so convenient to have something that isn't in the Earth's orbit, and is following us around the Sun. it makes communications easier. It's worth the expenditure of energy.
 

Fraser: Right, if you wanted to put a spacecraft there and didn't have the help of the Earth's gravity, you'd have to fire your rockets non-stop, using tremendous amounts of fuel. Even though you've got to do minor corrections to stay at that sweet spot, it beats having to fire your rockets non-stop o stay in that kind of position.
 

Pamela: So with the L1 spot, which is between the Sun and the Earth, that's someplace we stick things that are observing the Sun for us. What's cool is they're just enough closer to the Sun that in a lot of cases, when there's a particle spray – a bunch of electrons headed our way from the Sun – they might hit SOHO that's hanging out at L1 a little bit before they hit Earth, about an hour earlier. That gives us extra time to protect our astronauts and put satellites into safety mode, because SOHO can send us radio signals at the speed of light that these electrons are coming toward us at less than the speed of light.
 

Fraser: Right. Okay, so that's L1. What's L2?
 

Pamela: If you have a position between the Earth and the Sun, there's also a point that's on the same line but it's beyond the Earth. So you go Sun-Earth-object, and that we call L2 (ever so creatively).
 
Normally if you stick an object on an orbital path bigger than the Earth's orbit, it will orbit a little bit slower. Since you have the added pull of the Earth, it's like making the Sun a little bit bigger, so an object can orbit faster and still be stable at that greater distance. It's not entirely stable: just like L1, it's saddle shaped and you can fall off the Lagrange point. It's still a great place to stick things that have to make corrections because it makes the communications easy.
 
For instance, the Herschel satellite, the Planck satellite, the James Webb Space Telescope are all candidates for the Lagrange-2 point. WMAP, the microwave anisotropy probe that has given us such wonderful information about the cosmic microwave background is hanging out at the Lagrange-2 point.
 
This is a good place to put things that is protected a little bit from the Sun's light, by the Earth hanging out there. It's in a nice safe place beyond the Earth, following us around an orbit, and because it's not orbiting us, instead orbiting the Sun, all the random junk that orbits the Earth is not in any danger of hitting these things in the Lagrange points. The radiation doesn't get there. It's a nice safe place to stick things that work in the infrared and radio that need it a little bit quieter and a little bit darker.
 

Fraser: So you wouldn't necessarily want to have one of those satellites orbiting the Earth, because of our radio static.
 

Pamela: Our heat.
 

Fraser: Our heat. Right. That would actually cause them some problems. So if you keep them away from the Earth, they'll be cold, and will have fewer radio waves blasting them. They'll have a chance to observe better the state of what the universe really is. At the same time, you want to put them some place where you're not going to have them firing their engines non-stop. You also don't want them somewhere you can't communicate with them.
 
Yeah, I can imagine if you pushed one of those telescopes out to a larger orbit than the Earth, it'll slip behind us in orbit and there will be times like when we're trying to communicate with the rovers on Mars, right? They're on the other side of the Sun and there's no way to communicate with the rovers. If we put them in the L2 point, then it's there in the exact same spot in the sky – which probably makes communication a lot simpler, less power on the spacecraft than the kind of thing the rovers need to communicate with (though they relay stuff through satellites).
 
So I can see it makes a lot of sense. Okay. What's the next point?
 

Pamela: Then there's L3, and we don't have anything hanging out there. L3 is the one that's opposite us, so that it goes Earth-Sun-object. If you can imagine an object that has an orbit on the exact opposite side of the Sun from us where it's getting pulled on by both the Sun's gravity and the Earth's gravity. Even though it's not the same distance as the Earth from the Sun, it's orbiting with the same period, constantly staying in lockstep with us, always out of sight.
 

Fraser: So if I imagine this right, you've got the Sun and the Earth and I guess the combined gravitational force is pulling on this object. That feels to me like it would fall into the Sun.
 

Pamela: Here we're talking about an object that has an orbit that's again, a snert bigger than the Earth's orbit. It's trying to head off in a line to get away from the Sun, but it's the combined gravity of the Earth and Sun that's keeping it on its circular orbit, chewing around in lockstep with the Earth. This is very similar to L2, but it's beyond the Sun from us.
 

Fraser: So if you were to look at the line from above it would be like this object will be almost the same distance from the Sun as the Earth…
 

Pamela: Almost.
 

Fraser: Hard to calculate or see, but a little bit more. Instead of just going into a larger orbit, the way it should if it's further away from the Sun, the Earth is almost increasing the mass of the Sun and keeping it at that exact same orbit.
 
Okay. Is it stable?
 

Pamela: Again, it's a saddle point. The objects are going to want to fall out of that spot. If it can balance just right, or has engines to keep it balanced, it will stay there.
 

Fraser: There are no spacecraft planned for that, are there?
 

Pamela: No, because the communications isn't possible.
 

Fraser: But I can imagine it would be great. If you ever had SOHO, you could put another SOHO on the other side of the Sun and observe it at all times.
 

Pamela: The trick is you start needing to have things at the right angles between the Earth, Sun and the object so that you can relay the communications around the Sun, just like we have satellites that allow us to relay communications around the planet Earth. We can't talk directly to a satellite that's through the planet, on the opposite side of the Earth in its orbit. Instead, satellites can relay communications from one satellite to the next to get from Australia to Washington DC.
 

Fraser: Right, so if we had other satellites going around Venus or in some of the other Lagrange points, you could actually get this communication. So you could always observe the front and backside of the Sun at the same time.
 

Pamela: Then just relay the information all the way around and put it together in the lab later.
 

Fraser: There might be uses for those. Would they be useful going around the Moon, in the Earth-Moon system?
 

Pamela: This is where you start to get into space elevators and other crazy stuff. Let's talk about L4 and L5 to get them out of the way first.
 

Fraser: Sure, yeah.
 

Pamela: There are two more Lagrange points left, just two. These are the most stable. They are points that lag behind the Earth in its orbit and ahead of the Earth, such that if you drew an angle from the Earth to the Sun to either L4 or L5, both of those angles are 60-degree angles.
 
There are these hills that it's capable to stand on top of and just hang out there and be gravitationally balanced.
 

Fraser: So it's the combination of the gravity from the planet pulling you forward, and you're still going around the star, keeping you in that orbit. If you fall too far back, the gravity of the planet pulls you back in. this is the opposite of that saddle. It's very stable – it requires energy to get out of this orbit.
 

Pamela: The objects are hanging out here. They're getting tugged forward by the Earth, or pulled back from the Earth, because their natural inclination is going to have different periods than what they are. It's really neat that if you have a map of your potential of hanging out in any particular point, these are actually at the tops of hills. They're fairly flat tops of hills. Once you're up on top, you have to take effort to fall off. What's cool is you can actually end up with things inside these larger L4 and L5 points on little tiny circular orbits, where they're going around within the L4 or L5 point and also going around the Sun. that's just kind of neat.
 

Fraser: So it's like a volcano. You've got a mountain where it's quite hard to get into that point, but once you're at the top, there's actually a crater inside that's easy to roll down into.
 

Pamela: Sort of like that, yeah.
 

Fraser: Not that there's actually volcanoes in space, but that's the way the gravity works.
 
[laughter]
 
So if we were to put a spacecraft into one of these L4 or L5 points, same deal – they'd just sit there, no energy required, right?
 

Pamela: What's cool is there are asteroids hanging out in the L4 and L5 points of Jupiter. We call these the Trojan asteroids. It looks like Neptune also has its own Neptunian version of Trojan asteroids that may even be more populated than Jupiter's. Mars is tugging on asteroids as well, holding them locked in its Trojan points. These are places where the solar system likes to store its rocks.
 

Fraser: We don't have any going around the Earth?
 

Pamela: Not as much as these bigger things like Jupiter and Neptune.
 

Fraser: I wonder, if you could fly some asteroid observing telescope out to the Earth L4 Lagrange point and place it there, would it see rocks and debris and stuff in a cloud?
 

Pamela: I'm sure the density of rocks and pebbles and pea-sized bits of gravel in the Earth's Lagrange points is probably higher than they are elsewhere in the solar system. These are just good places to store things.
 

Fraser: If you were sitting on Jupiter's orbit, maybe standing still on Jupiter's orbit while it and its Trojans go around, you'd be standing there and a whole pile of asteroids would go past you, then Jupiter, then a whole pile more asteroids.
 

Pamela: Oh yeah. That's the really cool thing. If you look at a plot of where rocks are in the solar system, if you look at a plot of where all the asteroids are located, there are just piles of them in Lagrange points for Jupiter, Saturn and Neptune. That's just neat to look at.
 

Fraser: We talked a bit about spacecraft we might put in some of those Lagrange points. I've heard ideas of putting spacecraft into the L4 and L5 points as well – space colonies, space stations. It's so stable it doesn't require energy once you put it in there.
 

Pamela: That's one of the places they have at various points talked about, with the Earth-Moon system, sticking space stations.
 
What's also cool is with the not particularly stable, but we have engines to fix it L1 and L2 points in the Earth-Moon system, you can start to think about building space elevators with regard to the Moon.
 
The moon is facing the Earth the exact same way all the time. It's going around the Earth at the same rate that it's rotating about its axis. So if you have something in the Earth-Moon system's L1 or L2 point, it's essentially in geostationary orbit around the Moon. It maintains the same orientation with the same plot of land on the surface of the Moon all the time.
 
It's not the same way with the Earth. The Earth rotates about its axis fairly quickly. There are specific geostationary orbits that we stick communications satellites in. With the Moon, you can use the L1 and L2 points. So you can conceive of potentially some day sticking some sort of space station in geosynchronous orbit above some point on the equator where there's land and building a carbon nanotube space elevator tether and dropping it down to the surface of the Earth.
 
You could have an elevator to get to geosynchronous orbit (which is pretty high up). Then you fly your little rocket from that craft to something that is in the L1 orbit between the Earth and the Moon and you take a different elevator down to the surface of the Moon. Hang around, walk to the exact opposite side (you'd probably actually want a vehicle of some sort) and then take an elevator up to the L2 point which is pointed away from the Earth-Moon system and could be pointed away from or toward the Sun, or at right angles. You could use that as a jumping off point to escape the Earth-Moon gravitational system.
 

Fraser: that would be awesome. Like heaven! How cool would that be?
 

Pamela: It's a brave new sci-fi universe.
 

Fraser: Let's get on that, people!
 
[laughter]
 

Pamela: It's a bit expensive.
 

Fraser: I want my space travel!
 
[laughter]
 
I actually did an article on that space elevator concept. The advantage is since you attach the elevator to the surface of the Moon, you don't have the problem with the instability of the L1 point, because it's tied to the ground. Just like a balloon really wants to float away, you'd be able to tie your ribbon down to the Moon and even though it'd be trying to get out of that orbit, it would be continuously held there.
 

Pamela: The only thing that's a bit scary, and anyone who's read Kim Stanley Robinson's Red Mars series has read about this, is what if the cable breaks?
 

Fraser: It would come toward the Earth.
 

Pamela: Yeah, and you can end up with a ribbon of destruction wrapping itself around the planet. That's a rather bad thing. So yeah, there are all sorts of safety things to be figured out. It's still a cool plot point and a cool thing to dream about and imagine. The future has so many possibilities. It's fascinating to think about what's possible thanks to these neat gravitational holes in space.
 

Fraser: So now hopefully, if you hear someone bring up Lagrange points, or if you read it in an article, you'll know what they're talking about. Thanks Pamela!