One of the most amazing implications of Einstein’s relativity is the fact that the inertial mass of an object depends on its velocity. That sounds like a difficult thing to test, but that’s exactly what happened through a series of experiments performed by Kaufmann, Bucherer, Neumann and others.
Kaufmann’s measurements of electron charge to mass ratio diagram
Kaufmann original papers (in German) here, here, and here (translated to English)
Bucherer’s experimental setup
Bucherer papers here (translated to English), here (in German)
Transcription services provided by: GMR Transcription
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Fraser Cain: Astronomy Cast, Episode 370, Kaufmann-Bucherer-Neumann Experiments. Welcome to Astronomy Cast, your weekly fact-based journey through the cosmos. We hope you understand not only what we know but how we know what we know. My name is Fraser Cain. I’m the publisher of the Universe Today, and with me is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville and the director of CosmoQuest. Hey Pamela, how’re you doing and where are you?
Dr. Gay: I am with a crappier video camera at the Lunar and Planetary Sciences Conference down in Woodlands, Texas, which is a little tiny enclave on the north side of Houston, sadly about 45 minutes away from the Johnson Space Flight Center, but this is a much nicer conference venue than the one that we had down near Johnson, so this is where I am, and we’re discussing planets, planets, planets with some asteroids and other rocks thrown in all week long.
Fraser Cain: And for those of you who don’t know what this is, this is one of the big conferences. We have the American Astronomical Society Meeting, we have the AAAS, we have this one and then the Geophysical Society –
Dr. Gay: The American Geophysical Union.
Fraser Cain: Yeah, and those are sort of the big four meetings. So, you’re at one of the big four this year and a pile of press releases will come out and we’re gonna find out all about subsurface oceans and hydrothermic vents and potential landing spots on Mars. So, this is gonna be exciting. Keep us posted. Any other announcements this week?
Dr. Gay: Just reminding everyone our Hangout?A?Thon is set for April 24?25. If you are a super fan living in the greater St. Louis area or willing to get your butt there, we even have some opportunities for you to either volunteer or hang out as we record. We certainly need all hands on well, everything as we go. So, drop me an email, drop me a note wherever you are, and we’re looking to celebrate, making a new day work for science and the fact that these Hangout?A?Thons have kept us going.
As I was saying before we started recording, this week marks the week that we learned about sequestration back in 2012 actually and it’s only because of your donations that I’m still here. So, thank you for allowing me to keep having my career as we face numerous government cutbacks.
Fraser Cain: All right, so as we’re thanking people for giving us a chance to have a career, I should also point people the way you can help fund what I do, which is to go to patreon.com/universetoday. And this is, of course, the Patreon campaign that we run for the Universe Today and also the videos that we do. We just recorded Video No. 172. We release two of them every week, all the concepts in space and astronomy, many inspired by what we do here on Astronomy Cast, I’m not gonna lie. So, yeah, go to patreon.com/universetoday and then you can help fund what I’m working on.
Dr. Gay: And to mimic what they say on NPR, we’re here because some people have chosen to donate, and if you’ve never donated, you’re basically leaching off of the goodness of others.
Fraser Cain: Awe, yep.
Dr. Gay: Be one of those people yourself and give today.
Fraser Cain: Go ahead to patreon.com; check out what my salary is. You can see what I earn.
Dr. Gay: Yeah.
Fraser Cain: Okay, well, let’s get rolling.
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Fraser Cain: So, once again, we are pleased to have Casper Mattresses as an advertiser here on Astronomy Cast, and this is more than just a promotion. We both use this mattress, for a couple of months now. How’s yours working out for you?
Dr. Gay: I have to admit, when I first got it, the most exciting part was the box. This was the most amazingly packaged mattress ever, but –
Fraser Cain: How have they bent the laws of physics to send a mattress by mail? It blows my mind.
Dr. Gay: Right, and once you get past the excitement of the box; the mattress itself is actually really cool. We have a Tempur-Pedic at home. I grew up with normal spring mattresses, and this is my Sunday take a nap with the dog falling asleep on my iPad daybed mattress, and it’s a combination of memory foam and latex that leads to the not too squishy overheating of the Tempur-Pedic, but it doesn’t have that too firmness that you get with a lot of spring mattresses.
Fraser Cain: Yeah, you know, of all the mattresses I’ve been on, so far, it is the perfect mattress. I really like the way that it feels and when we got one to experiment with, to test out, I thought oh, we’ll see how this goes and keep the other one around, but no, it absolutely replaced the existing mattress that we’re using. And as part of this, they offer a free 100?day trial and return policy so if you for some reason aren’t happy then you can send it back and I guess fire it back through the transdimensional vortex that it got to you in.
Dr. Gay: And the prices are really reasonable. It’s $500.00 for the twin size mattress, which is what I have for my daybed and the king sized is just $950.00. So, if you need a mattress and you don’t want to – well, if you don’t want something affordable, this is awesome so go for what’s awesome and get a Casper.
Fraser Cain: Right, and of course, listeners through Astronomy Cast can get a special deal on it so just go to www.casper.com/astro and you can get $50.00 off your next mattress purchase and you just order it online on their website and it will arrive in the mail by delivery. And, again, if you get the king sized, how they’ve packaged it up will blow your mind.
Dr. Gay: Hey, I felt that way about the twin.
Fraser Cain: Yeah, yeah, so we both find that part really entertaining, but the mattress is great, and I’m really glad to keep using it so thanks Casper.
Dr. Gay: Thank you.
Fraser Cain: Go to casper.com/astro and you can get $50.00 off your mattress purchase.
So, one of the most amazing implications of Einstein relativity is the fact that the inertial mass of an object depends on its velocity. Now, that sounds like a difficult thing to test, but that’s exactly what happened through a series of experiments performed by Kaufmann-Bucherer-Newmann and others. All right, so Pamela, where do you wanna start? Do you wanna start with just this idea, you know, what are we talking about in relativity when we talk about the inertial mass of an object depending on its velocity?
Dr. Gay: So, the basic idea as misarticulated over and over again is that an object’s mass gets larger and larger and larger the faster it goes. Now, the truth is that if you increase me to near the speed of light, I’m not actually going to add atoms to my body. I’m not going to become more massive; I will do that perfectly well on my own thanks to chocolate, speed of light is not required.
Now, what will happen is my ability to interact with the world as an object with mass will seem to increase. How I move, how much energy it takes to increase my velocity will go up. And the way we actually look at this nowadays is not by saying something’s mass increases but by saying that we see a change in its momentum and we refer to it as this concept of inertial mass, which is tied to the energy required to increase or decrease something’s motion.
Fraser Cain: Now, when we talk about some of the concepts of relativity, a lot of it is relative, right? So, for example, if you’re traveling at a speed of light towards me, as we talked about last week, your length on the distance of direction traveled seems to change, but that’s really a relative thing. You’re moving towards me, I’m in theory not moving, although really, you know, so with this sort of change in inertial mass or change in the momentum, how is this relative? Like if you’ve got two things that are moving at the same speed, do they see this of each other?
Dr. Gay: You usually refer to it as relative to the frame that you accelerated out of. So, if two things start out in the same frame of reference, this is the twin’s example you often read about, and one of those twins starts accelerating, he’s the one that we look at in terms of seeing that change in mass. Now, if the two twins are going along in some frame of reference, it’s not like one of them can appear to decelerate out of that frame of reference so using the which one is accelerating as figuring out who’s mass has changed and relative to who’s is usually a safe starting point.
Fraser Cain: Okay, and so as you mentioned though, this is not about your mass increasing?
Dr. Gay: Right.
Fraser Cain: This is about your inertial mass or your momentum?
Dr. Gay: Yes, momentum.
Fraser Cain: And so can you explain what the difference is there?
Dr. Gay: So, any given object in motion has momentum. This includes light, which has no mass. The momentum can either be written out relative to kinetic energy so kinetic energy is one?half MV squared. Momentum is mass times velocity so just MV so you can get between these two different quantities. And with light, we don’t know its mass, but we know its energy so we substitute that in. Since all light moves at the speed of light, you look at the energy of the light instead of the kinetic energy and you can get at the momentum.
It’s all math just cancelling Ms and Vs and factoring in Cs, but that only works in your standard Newtonian mechanics. You have to start adding in factors related to, depending on what you’re manipulating; one usually often minus the velocity divided by the speed of light and that reduces to just one if –
Fraser Cain: If you’re going the speed of light?
Dr. Gay: Yeah, if you’re going the speed of light. And it’s actually the square root of one minus V squared over C squared is what you often see in these equations.
Fraser Cain: Great.
Dr. Gay: And so if you’re dealing with something that essentially reduces to one, you ignored it in normal day-to-day use.
Fraser Cain: Right, you need to have a one. Okay, so then let’s rewind back and let’s talk about before these experiments were run. What was the expectation by the researchers on what was gonna happen or how the universe worked?
Dr. Gay: Well, they didn’t really have much at this point. So, we’re looking at what was going on in the 1890s and the earliest to 1900s. In 1896, Henri Becquerel, whose last name I hopefully actually got right this time, realized that a lot of different elements seemed to give off these high-energy – we called them beta particles back then, which much to my dismay, I learned at some point in high school were actually just helium particles and I felt betrayed by everything because everyone talks about how exciting beta particles are, beta radiation – no, it’s just fast-moving helium.
But he didn’t know it was fast-moving helium when he found it so they called it the beta particles. And these beta particles were fairly easy to capture. They also found via beta radiation that there were often high-energy electrons that were given off during the processes led to various decays. Again, those are easy to capture and deal with. And they still didn’t fully understand the electron back then. If you think about it, this is before people were dealing with electricity as a day-to-day thing that powers every device around you.
Experiments involving electricity had gone on for a long time. You can imagine all the things Benjamin Franklin did a couple hundred years before this, but the details of understanding how to deal with electricity were completely new. So, J. J. Thompson came along and he realized in the late 1890s that you could actually change the path of an electron with magnetic fields, with electric fields, built up by nonmoving charged plates and started calculating if you have charged particles moving through these different fields, how does one electric field affect one charged particle? How does the magnetic field affect a moving charged particle?
And all of this led to a series of equations that made it possible to calculate the expected trajectory of a moving charged particle with a given velocity as it moved through electromagnetic fields. This is actually something that up until recently, everyone dealt with every single day. Cathode ray tubes, the technology that led to the television coming out in the 1930s, all of that was based on this early work by Thompson on moving electrons around with electromagnetic fields. So, they were building early Cathode ray tubes, shooting electrons, applying fields and based on the fields that they created, they could move that electron around.
Essentially, if they wanted to, they could make a very slow picture because they didn’t have all of the electronics that are required for television.
Fraser Cain: Right, but the point here is that you’re starting to learn how to control the direction using electricity of very fast-moving particles?
Dr. Gay: Right and the thing that they ran into is you can calculate for a slow-moving electron moving through one of these setups, very straightforward what the expected deflection is. You can also use this if you know the velocity of the electron, you know the charge of it, you can – well, you don’t even have to know the charge, you just have to know the velocity of the electron. You can get at the charged mass ratio based on how the electromagnetic fields deflect its path.
So, you have an electric field, you have a magnetic field, you have a known velocity and now you can get at the charged mass ratio. And what they found was if that velocity got high enough, as the velocity increased, the charged to mass ratio changed and in fact, it changed such that the faster you were going, your charge was getting held constant, your mass isn’t increasing, but it seems to be increasing so as that M goes up with that charge above it, your entire ratio goes down.
Fraser Cain: And so to just kind of understand, like I’m imaging them shooting electrons past magnets and they’re trying to control the angle that the – I’m making all kinds of hand signs so if you’re using the podcast, you’re just gonna have to imagine me shooting these beams of electrons with my hands, my hands are electron beams.
Right, so you’ve got these electrons in there and they’re turning this corner as they’re going past the magnets and then they’re going towards the Cathode ray tube. The faster you speed up these electrons, you would expect them to be harder with more momentum to kinda crank them around that corner and aim them where you want, but it got even harder than they were expecting.
Dr. Gay: And they didn’t have the high sensitivity equipment we have today so in order to precisely figure out what was going on, they’d use essentially gated systems that only allowed electrons with certain velocities to go through the system and then they’d have to look to see where on a photographic plate those flung electrons were able to escape to.
Fraser Cain: Oh, so smart.
Dr. Gay: Yeah, it was really amazing equipment that they put together. And so then they got left with this well, huh, what’s going on with this apparent increase in mass, decrease in measured charge to mass ratio as this object is moving faster and faster?
And, of course, you had experimental error that played in and you had really awful algebra that played in, and this led to about ten years of people going, huh, and Kaufmann, who’s one of the people that we’re talking about today, is actually one that in trying to put all of this stuff together, he did a very complicated experiment, complicated equipment, precise measurements and goofed his algebra in trying to explain all of it because he was trying to deal with how that ratio of velocity over the speed of light seemed to factor into everything they were doing.
And, of course, if you have an algebra mistake, you come out saying well, what I did doesn’t actually match what was theoretically predicted, which is a really interesting result, except it’s based on an algebra fallacy. So, he came out with a result in 1901 with math errors, corrected it, came back out in 1902, but then also while he did a very good experiment and he did good photographic plate measurements, it still wasn’t ideal and so they were left in this situation in the early 1900s where there were a couple of different explanations.
Lorentz had figured out how to work his – he moved from contraction due to your motion relative to the luminiferous ether so contraction of length in the direction of motion. He kept going. He figured out how to factor in increase in mass as velocity approached the speed of light. He came out with all of what we still call the Lorentz transformations, run physics to explain it, but excellent math to explain it. There were other folks.
There’s a fellow by the name of Max Abraham who came out with a set of equations to try and explain how things had to take into account both a transverse electromagnetic mass and then your normal and so people were coming up with all sorts of different ways of manipulating the variables to take into account well, maybe it’s because you’re moving in this direction versus all sorts of different things. And they also started coming up with things like well, we know the electrons have sphere. Now, imagine if the charge is distributed on the surface but that somehow gets affected. They were grasping at straws.
Fraser Cain: Right, so that the shape of the electron changes in the – like it turns into a football shape, depending on the direction of motion and that will change.
Dr. Gay: Or maybe only the charge moved on the surface.
Fraser Cain: Right.
Dr. Gay: So, the beginning of the century was kind of a mess.
Fraser Cain: Simpletons, come on.
Dr. Gay: Well, they weren’t simpletons; they were just very creative people.
Fraser Cain: No, I know, they were just thinking of ideas, right?
Dr. Gay: Yeah.
Fraser Cain: What could cause this weird change in the mass charge beyond of what we were expecting?
Dr. Gay: I’m just kind of amazed that anyone came up with the idea of let’s add and subtract and square and square root factors of one plus V over C or one minus V over C or one minus squared V over C. That is such a weird factor to come up with, but they did it. So, there was a lot of stuff that in retrospect I could only ask who came up with that idea because it worked. And once Kaufmann figured out his math error in 1902 and fixed it, everyone was working to replicate these experiments. Everyone was working to figure out how do we do better so that we can sort the difference between these different theories?
And Einstein was meanwhile off to the side. He wasn’t in the lab running experiments. That was never really Einstein’s thing to do. He was instead off to the side thinking and while Lorentz was coming up with his contractions and trying to figure out how to deal with the experiments related to the luminiferous ether, while Kaufmann was flinging electrons around, while Thompson was trying to understand the atom and the electron, Einstein was trying to figure out what is special about looking at the universe in terms of the speed of light.
How do we perceive the speed of light? Why is it the different colors of light all appear to move at the same speed? How can that be possible that you see the same speed of light irregardless of what direction you’re moving in or how fast you’re moving? And as he thought and as he worked on amazing maths, without algebra errors, I’m sure he had some, he just failed to publish them –
Fraser Cain: Right.
Dr. Gay: As he worked on all of this, he realized that the key wasn’t that there was some ether we had to figure out how we are or are not coupled to, the key was the fact that everyone perceives the speed of light the same way and in order for that to be true, you have to start changing how you perceive different things. So, as you’re going faster and faster, your perception of time changes.
Well, if your perception of time changes, how is it that the person on a high-speed train who drops a vase, sees it break and someone who’s off to the side watching the train go by where they see everything on the train in slow motion because time isn’t moving at the same rate in both situations, how is it that they see this vase slowly float down to the platform and also break? Well, you explain that by increasing its mass. So, all of these different Lorentz transformations all factor back to how do you explain two observers seeing the same things happen even though they perceive time passing so differently?
Fraser Cain: And I never had thought about that idea of the vase falling in the train and the fact that because of the relativity, you see it breaking in that way. That’s really cool.
Dr. Gay: And it leads to so many things suddenly being able to be made sense of in what we observe. My favorite is the [Inaudible] [00:24:51] Muon. It’s a high-energy particle that’s extremely unstable, forms in our upper atmosphere via high energy reactions and particle decays, but we’re able to detect it down at the surface of the planet. And the amount of time that it takes that muon to get from where it’s formed to the detectors often in our college classrooms is longer than the muon should be allowed to live. And so clearly, some magic is allowing muons to reach the surface of the earth and that magic’s relativity because the muon is moving so fast that time is slowed down for it and it is for us able to live longer, even though in its frame of reference, it lives the same amount of time.
Fraser Cain: That’s crazy.
Dr. Gay: It’s crazy awesome is what it is.
Fraser Cain: Yeah. Yeah, that’s like a science fiction story I think. Some scientist needs to extend her life and so she builds, you know, starts moving faster and faster, nearing the speed of light and therefore gets to live to see her children grow up or whatever, I don’t know.
Dr. Gay: Or lives to see the disease that she has get cured.
Fraser Cain: Get cured, yeah, exactly. Oh, that’s perfect.
Dr. Gay: Or Ender’s Game.
Fraser Cain: Hey, any science fiction writers, we just came up with your great idea.
Dr. Gay: Yeah, but they have this in Ender’s Game. They had to – I can’t remember the character’s name –
Fraser Cain: Don’t you spoil it.
Dr. Gay: I’m not spoiling anything with this part. So, basically, they had to save one of the people to mentor, Ender, until they found him. And so this person essentially skipped through the generations waiting for the right child to be born and they did it by keeping him going a very lonely life near the speed of light.
Fraser Cain: At high speeds, a relativity speeds, yeah, that’s really cool. Cool, so then, I mean even after sort of those initial experiments were done, I know they kept going. Other people kept performing the experiment with greater and greater levels of accuracy, but now it’s a matter of testing and confirming what Einstein had worked out separately.
Dr. Gay: Exactly, and it was also initially, we had equations that had things blowing up previously. There was what was referred to as the ultra violet catastrophe, which we talked about in our Black Body Radiation episode, which was the original mass to try and understand essentially what colors of light are given off in different scenarios said that you should get a whole lot more ultraviolet light than is actually being observed.
And we eventually used the fact that we knew ultraviolet light was not actually coming out in infinite amounts to realize that light must be quantized, must have discreet energies and that changed the equations. With all of the electron charged mass experiments, they seemed to indicate that if you went faster and faster and faster, your mass would go to infinity, which seems like a rather bad thing to happen. And so you have to keep wondering if I go fast enough, if I try this with different other things, will I see that that starts to turn over? There’re all of these I want to prove Einstein wrong that started from Day 0.
Fraser Cain: People have been trying to do this for centuries.
Dr. Gay: Well, no, a century.
Dr. Gay: A century. A century and ten; 1905 is when things came out.
Fraser Cain: I said two, between one and two centuries, people have been trying to do this.
Dr. Gay: It still rounds to one. Anyways, different argument. So, what was found is by gosh, yes, as you go faster and faster, it’s true, your mass does show no signs of stopping its traumatic increase.
Fraser Cain: And this just makes it impossible to go faster than the speed of light.
Dr. Gay: It makes it impossible to actually get to the speed of light because there – yeah.
Fraser Cain: Get to the speed of light and not to mention go faster.
Dr. Gay: Yeah, there’s not enough energy to do it.
Fraser Cain: Yeah, Einstein has really ruined Sci-Fi Christmas.
Dr. Gay: No, no, because he did nothing to ruin the idea of tunneling. So, we know that electrons can tunnel from one place to another. Electrons have mass. They’re essentially jumping through space and ignoring the intervening places. We just need to figure out how to tesseract.
Fraser Cain: Right, okay. All right, well, then you’re off the hook this time I’d say. Well, thanks a lot Pamela.
Dr. Gay: My pleasure.
Fraser Cain: Thanks for listening to Astronomy Cast, a nonprofit resource provided by Astrosphere New Media Association, Fraser Cain and Dr. Pamela Gay. You can fine show notes and transcripts for every episode at astronomycast.com. You can email us at email@example.com, tweet us @astronomycast, like us on Facebook or circle us on Google+. We record our show live on Google+ every Monday at 12:00 p.m. Pacific, 3:00 p.m. Eastern or 20:00 GMT. If you miss the live event, you can always catch up over at cosmoquest.org.
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Duration: 31 minutes