Ep. 499: What is the proposed Hubble-Lemaitre Law?

We started out Astronomy Cast with the controversial decision to de-planet Pluto. And here we are, more than a decade later, at the brink of recording our 500th episode when another big decision is coming down from the IAU: whose name goes on the concept that our Universe is expanding: Hubble or Lemaître? It’s a big deal and Pamela knows all about it.
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This episode is sponsored by: Casper.

Show Notes

Who was Hubble?
Edwin Powell Hubble: Biography
Who was Lemaitre?
Georges Lematrie
What is Hubble’s Law?
Edwin Hubble and the expanding universe
Expansion of the universe
Physical cosmology
International Astronomical Union


Podcast Transcription provided by GMR Transcription
Fraser: Astronomy Cast Episode 499, Hubble versus Lemaitre. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, again, is Dr. Pamela Gay, the Director of Technology and Citizen Science at the Astronomical Society of the Pacific and the Director of CosmoQuest. Hey, Pamela, how are you doing?
Pamela: My brain is good, but I mangled my arm falling off of a bicycle, and so like wrist, elbow, shoulder, ribs – they are all mad at me. So, if I’m in a slightly different position and sitting a bit stiller than normal, that’s why.
Fraser: Because you’ve got a mangled arm.
Pamela: Yeah.
Fraser: Oh.
Pamela: It turns out that bikes will randomly stop for no obvious reason. And yeah.
Fraser: Yes, yes, that is the dark side of riding a bicycle, is that you can fall down and hurt yourself.
Pamela: Yes.
Fraser: I’m glad you weren’t hurt any worse, because I’ve had a lot of friends get the old collar bone break or the arm break, elbow break, helmet explosion. So, we take our mountain biking very seriously around these parts. So, the fact that you were able to walk away from it and didn’t have anything long-term is good – but ouch.
Pamela: Yeah.
Fraser: Both of us have so much news. I think we’re just gonna have to trickle the whole thing out over the course of several months. But I think there is a couple of big things. First, next week we’re gonna be meeting in person at the 500th episode of Astronomy Cast. So, if you’re already gonna be joining us, we can’t wait to see you.
You got back from the IAU, that’s the whole point of this episode. So, we can cover that news in there.
Pamela: Right.
Fraser: And the last thing is that we’ve got a virtual observatory going. Big thanks to the good folks at Oceanside Photo and Telescope. So, if you want to hang out and observe the night sky with me and other people from the community, there is lots of news on how we’re gonna be able to do that. So, it’s really exciting. We bought this really cool telescope. I’ve done a bunch of livestreams on both Twitch and YouTube. And it is total game changer. So, stay tuned to all the work that we’re doing on all these places. Did you have any more news before we get in to the show?
Pamela: You know, Vienna is a fabulous place. I rode a brand-new bike there for multiple weeks without any accidents. I recommend Vienna and biking in Vienna, and maybe not biking on an older bike that hasn’t been repaired recently.
Fraser: Right. We started out Astronomy Cast with the controversial decision to de-planet Pluto. And here we are, more than a decade later, at the brink of recording our 500th episode, when another big decision is coming down from the IAU – whose name goes on the concept that our universe is expanding? Hubble or Lemaitre? It’s a big deal, and Pamela knows all about it. That’s as hard as I’m gonna try and pronounce Lemaitre. I may very well go back into a more English-Canadian accent as opposed to a French version of pronunciation, but that’s the best I can do. So, all the people who speak French in the audience, I hope I did his name justice.
Pamela: It’s way better than my Lematreay.
Fraser: Lematreay?
Pamela: Yeah, all my American comes out on that one.
Fraser: Is that how you say it?
Pamela: That is the Americanized pronunciation. We pronounce all of the letters because it’s not [inaudible] [00:03:34].
Fraser: First, before we get in to the actual decision, can you just like set the stage? You were in Vienna. IAU was meeting. What happened?
Pamela: Okay, so, for this year’s International Astronomical Union meeting, various groups of people working across multiple divisions, commissions, working groups, came up with a list of resolutions, things that they wanted the entire organization to vote on as these are things that we, as the astronomical community, need to dedicate our efforts towards. And this also in some cases includes dedicating our financial means towards. And among the kinds of things that we voted for was the various nations voted to dedicate funding to opening a new astronomy office for education.
The fundamental astrophysics groups voted on here are the ways we’re going to upgrade how we talk about the celestial coordinate systems now that we have better instrumentation, better algorithms, and can measure things more precisely.
My favorite vote was they shortened the resolution to okay, now we’re going to vote on the Earth’s rotation. And quite nicely, 100% of the people in the room, maybe there was one abstention, said, yes, the Earth rotates. And we were good with that.
Fraser: As opposed to the universe rotating around the Earth?
Pamela: It was the abbreviation of a new mathematical definition and the need for continued efforts on measuring the Earth’s rotation and quantifying it within software so that everyone’s using the same algorithms. But the short form was, Earth’s rotation. So, yes, we voted on the Earth’s rotation and we agreed, it’s rotating, and we need to upgrade our algorithms.
But there was one rather strange moment. It was realized roughly in the weeks leading up to the IAU, but not three months before the lead-up to the IAU, that there could be controversy surrounding a resolution to rename the distance velocity relationship that describes the expansion of our universe from being the Hubble Law to being the Hubble-Lemaitre – I don’t know how to say it – Law.
For those of you who don’t know, this person whose name I can’t pronounce –
Fraser: Google Lemaitre.
Pamela: Lemaitre – okay, we’ll go with Lemaitre. Lemaitre was a Belgian-Flemish priest who did amazing mathematics and defined a lot of the general relativity, a lot of the theories for the expansion of our universe, worked with data when he could get it. He wasn’t actually an observational astronomer.
And he published, using Hubble/Humason data that he was provided, a paper in French describing the expansion of our universe giving a value to what we now call the Hubble constant, before Hubble did. And this paper later got translated into English. And the equation that he had to describe the universe’s expansion, the paragraph describing the data from Hubble that he used, and the footnote were all strangely not in the paper translated into English. This translation occurred after Hubble’s research, and for many, many years, people thought huh, Hubble did all of this.
Fraser: But wait a second. I’m trying to understand sort of the chain of events here. So, who was the first person who observed that galaxies were moving away from us? Was that Hubble?
Pamela: No, that was an observer working down at Lowell Observatory, who had been expecting to see that all the galaxies around us are moving at a whole variety of different velocities.
Fraser: Right, some would be coming towards us, some would be going sideways, and some would be drifting away from us.
Pamela: And so, the early observations taken down at Lowell Observatory were like no, no, the bulk of the stuff is moving away from us. So, that was the first set of observations, not Hubble.
Fraser: Well, I guess I don’t understand. Who did the stealing here? Because you say that in the Lemaitre paper, there was references to Hubble and those were removed in the translation from French to English?
Pamela: Yes. So, the original equations that built on Einstein’s work and de Sitter’s work, and said no, no, no. We don’t need this cosmological constant. We don’t need to have a steady state universe. In fact, the universe is probably expanding. This falls naturally out of all of these equations. And oh, look, here is not yet interpreted data by Hubble and Humason.
Fraser: So, Hubble took the data and Lemaitre figured out that, that meant that everything was moving away.
Pamela: And he derived the mathematics describing what was happening.
Fraser: That the farther a galaxy is, the faster it’s moving away from us.
Pamela: Yeah, and this was in 1927. So, several years before Hubble’s paper.
Fraser: Yeah, when was Hubble’s? In the early ‘30s.
Pamela: It was ’31. And it was in ’31 that this poor Belgian priest was like, hey, I got there first. Look, it’s in French, but I did it.
Fraser: Is it thought that Hubble knew, that Hubble had seen his calculations and put them into his paper and didn’t give him credit?
Pamela: It’s even more subtle than that. At a early IAU, there are records showing that Hubble and Lemaitre, Lemater, however you say his name –
Fraser: Say it any way you want. He’s not around anymore.
Pamela: – that Hubble and this Belgian fellow had directly discussed this face-to-face. Now, when approached later on about this and asked if he needed corrections done, our Belgian priest said, no, I’m okay with the lack of corrections made to things. And he didn’t insist on having things added in to the translation that forgot his equation – 24, if you’re keeping count, and erased the references to Hubble.
Now, this puts us in a quandary as a field. So, there are a whole bunch of other people that worked out the maths of the expansion of the universe, and then they plunked in a constant, and the universe stopped expanding
There was Lemaitre who did it in French, which, in one article I read about this, might as well have been in Martian for the likelihood it was going to be read. He did it first, didn’t necessarily publicize it a lot. And then, when given the chance to take all the credit for it, in a way that kind of reflects in a good way the fact that he’s just a scientist doing science as a Belgian priest. He was like no, I’m good. Everyone knows the science now. And so, what do we do?
Fraser: Well, I know what we have done, which is in the past, people whoever are able to sort of win on the game of politics, Jocelyn Bell Nobel Prize, for example, gets the spoils. And so, in this case, Hubble did a great job of promoting the research and making sure that the right people saw his work. And he got his name etched onto a telescope, a space telescope.
Pamela: Now, we like to try and fix history. This is where the period luminosity relationship for Cepheid variable stars has been renamed – again IAU was involved here – has been renamed the Leavitt Law, referring to the efforts made by the female astronomer, Henrietta Leavitt, working at Harvard College Observatory.
So, we like to try and fix history and give credit where credit is due instead of where credit is demanded. So, this is one of those frustrating situations. And making things even more complicated, just in case you wanted things to be more complicated.
Fraser: Always.
Pamela: So, it was in an account that I read by Sean Carroll where he discusses the need to correct himself on whether or not our friendly Belgian priest should be given credit for the discovery after he found out about how much earlier and the fact that it was driven by data, that Lemaitre’s paper was written, he went back and was like, now we need to consider what’s going on. And it really looks malicious that the translation didn’t include these things.
So, that’s where the stage starts. So, it starts with it looking like this was a purposeful mistake made by the translator, so Hubble would get credit. Now, I’m gonna read this to you so I don’t screw it up. This is from Mario Livio, who did a great deal of research on the matter. He’s one of the great Hubble scientists. He’s also a really good science communicator through his various books.
And he writes, “I actually discovered a letter that Lemaitre wrote to the editor. He says the letter revealed that Lemaitre himself had translated the paper, and he, himself, omitted those paragraphs.” But why? “He thought there was no point,”
Livio says, because Hubble’s paper already appeared. There was no point to repeat his somewhat more tentative conclusions that appeared before that.
So, it now appears with the letter that was found by Livio, that our friendly Belgian – I’m assuming friendly – our Belgian priest scientist had basically said, nah, Hubble did it better. I don’t need to translate this part of my paper. I’m gonna let Hubble’s firmly held, demanding attention conclusions to stand. Now, he didn’t say it like that, but this seems to be the implication, that Lemaitre was willing to let Hubble take the credit, take the fame. Which just makes me want to name it after him more.
Fraser: Yeah. So, now people understand the controversy, they understand what was discovered and sort of how everything went down. And so, everybody arrived in Vienna, ready to vote.
Pamela: Yes.
Fraser: What happened?
Pamela: Well, first of all, it was realized in the weeks leading up in to the conference – but not three months before the conference. And this is the important part, that this might be controversial. And like the demotion of Pluto, it might get people in a furry. So, rather than worry about small children writing concerned emails to their local astronomers because this law that everyone loved got renamed, it was decided that the IAU would invoke one of its new rules, which is, given three-months’ notice, votes can be held electronically instead of in person at the conference.
Fraser: Oh, they fixed the Pluto problem.
Pamela: They fixed the Pluto problem, but this is where the – but they didn’t realize this three months in advance problem comes in. Because we’re all at the IAU. We all want to vote. It’s why we’re there, is we’re there to be bureaucrats.
So, here we are, ready to vote, being told, okay, we’re gonna ask you to vote. But your vote does not count because we’re going to make you vote later electronically. But we’re gonna call this a straw man vote, and we’re going to assume the voting outcome of the people in the room directly reflects the votes of the entire IAU population. Which – since I don’t think we had a majority fraction of the union present at the assembly – I’m not sure how much that works. Yeah, so we all voted.
Fraser: Yeah, yeah, and, and?
Pamela: And they didn’t tell us the exact numbers, but from looking at the hands up around the room, there was, to my eyeball, which is not scientific, about ten-ish percent people – again, this is my eyeball, ten-ish percent people that said, I’m not even gonna make a decision. You’re all on your own. So, those were the abstains. Then there was roughly another 20% that were like, no, no, we deny this vote.
And then there was a clear majority, roughly 70% according to my non-scientific eyeball, that were like yes, yes, we should do this.
But the people who were no votes were very argumentative no votes, and they weren’t given very long to debate.
Fraser: So, now we have the Pluto problem back again.
Pamela: But at some point, presuming three months from now, because it has now been announced that we’re going to be doing this. There will be an electronic vote. And in the coming months, those arguments that were first brought up in the roughly 20 minutes before our vote, and only 20 minutes, roughly, before our vote, those people are going to get the fullness of three months to say here are the reasons we shouldn’t do this or why perhaps this isn’t the first thing we should do this for.
And there was a varied and all quite sensible number of reasons that this maybe shouldn’t be our highest priority. And so, I’m expecting there to be a large number of think pieces coming out asking us to think hard about what it is we’re doing and why other things might be a higher priority, or why maybe this is opening Pandora’s box.
Fraser: So, the bottom line is, there is no official stance yet. The IAU did a pretend vote, just to get a sense of the room. It seemed overwhelmingly in favor of changing the name to the Hubble-Lemaitre Law. But you are gonna do an official vote electronically soon. And who knows what’s gonna happen?
Pamela: And there is some really interesting points that came up during the debate. The most interesting, but not the strongest argument that came up was the question was asked, why is it Hubble-Lemaitre versus Lemaitre-Hubble. And this is being done by people who can pronounce the languages.
Fraser: You know what? People in the chat are giving you a rally easy way to do this. Okay? You know when you go to a restaurant and you have the person, the maître d’ – right?
Pamela: Yes.
Fraser: So, le maître d’ – so, just Lemaitre.
Pamela: Oh, that makes sense. Okay, Lemaitre. Okay, I’m gonna go with that.
Fraser: And then if you want to get French and fancy, then you can roll your “r” at the end.
Pamela: I can’t. So, my favorite argument was, why is it Hubble-Lemaitre instead of Lemaitre-Hubble. And the response was, it’s easier and sounds better to say, Hubble-Lemaitre.
Fraser: Yes, agreed.
Pamela: And then came the question of, but didn’t Lemaitre do the hard work in the beginning, and wouldn’t it make sense since he was first, to put his name first.
Fraser: Yeah but is the hard work of saying the names in a way that sounds nice. That’s the real hard work, right?
Pamela: Apparently.
Fraser: Not the hard work of who does the math and makes these groundbreaking calculations – what matters is, how does it roll off the tongue. Now, also, you can turn it into a portmanteaux.
Pamela: Yes.
Fraser: So, you could kind of like Hubblaitre or Hubble –
Pamela: No.
Fraser: Hubblemaitre?
Pamela: So far, we aren’t doing those in astronomy, for which I am grateful. But yeah, so there was that argument. And then there were a lot of other arguments that had never quite occurred to me. The first was, what about all the things that were figured out by indigenous not white people of the world first. And then when discovered by generally white cis males of Europe, the name of the not European cis white male was ignored and omitted from the history.
Fraser: Like when that Neanderthal first named Mars?
Pamela: Well, there is that. But –
Fraser: And it wouldn’t be Mars. It would be whatever the first – what if we do find the first name somehow written down from Neanderthals of what they called the planets? Do we go back and call – if they’re great, I think maybe we should, if they are really great names.
Pamela: Well, on a complete tangent, there is actually a working group on star names that is working to collect the indigenous names for different stars and stars that do not currently have a common name in the HR, HD, pick the atlas of your choice.
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Fraser: I love that more stars have better names. Like HIP91, who cares? That’s ridiculous. That’s your name? No. The universe is gigantic. Let’s go for as many names as we can possibly go for. We will never run out of names because we will never run out of stars. In fact, every galaxy gets a name. So, I hope the IAU really brings this up next time. I know they have already added a whole pile of star names, but this should just be the beginning.
Pamela: Yeah, this is the starting point. And so, we’re working to at least collect those names. But the question is, beyond what are the names of the planets, what are the names of the stars to different peoples around the world. What about the discoveries made by people that aren’t Eddington, that aren’t Einstein, that –
Fraser: Aren’t Chandrasekhar.
Pamela: And that was the example that I was going to bring up, is Chandrasekhar was lucky enough to eventually get the limit at which a white dwarf stops being a white dwarf and decides it would rather be a neutron star or just explode. That mass limit is named the Chandrasekhar limit. But this is a man who got multiple Nobel Prizes for multiple things. And he had to fight with Eddington until Eddington died to get his work acknowledged. How many other things that Chandra did are just well, the laws of stellar evolution instead of Chandra’s laws of stellar evolution, whereas other people get multiple things named after them, like Hubble?
Fraser: So, do you go back, find the first written account at any point and make that the name of that phenomena, no matter where it came from and who came up with it, whether it’s in Chinese, whether it’s in – if it’s the Crab Nebula, is the name for the Crab Nebula whatever the astronomer from China who first observed it was? That becomes the name of the thing in the official IAU. Now, everything is going to have all kinds of nicknames, but the Lagoon Nebula is called the Borg-Homer Nebula in my mind.
So, is that the way you go? And I guess the point is, the process of searching and trying to figure out who did this first is incredibly important. And that history matters. That we do take the time to dig back in to the records, to be proper historians and give credit where credit is due to the people who did the work, and to maintain that history. And then at the same time, you can’t control what people are gonna call things. That’s ridiculous.
Pamela: So, there’s two different rabbit holes we can go down with this. One is the naming of objects, where the IAU is working to allow objects to have multiple official names reflecting the various cultures that have studied those objects over time. So, the naming of things is one rabbit hole. The other rabbit hole that we’re struggling with, with the Hubble-Lemaitre – and I’m now gonna have to say maître d’ in my head every time.
Fraser: Yeah, you’re there, though. You got it.
Pamela: With this, it becomes more a matter of who is the first person to publish through peer review, no matter the language, a complete understanding of the thing. And this is where we see things getting fixed with the acknowledgment that Jocelyn Bell is now getting for her discovery of the Pulsar. Well, the Nobel Prize didn’t go to her.
Fraser: But you totally hear like Democritus coming up with the idea of the atom.
Pamela: And we cite it.
Fraser: And Democritus had no idea what was going on, had no ability to actually figure out that atoms existed, had no actual scientific rationale for the reason, except he just did a thought process of if I cut it with a knife, can I cut it with a smaller knife. Is there a point where I can’t cut it any more? That’s the smallest possible thing. That’s not a real theory, right? Because you need to observe it. You need to perform an experiment that shows you that your theory is correct.
Pamela: And this is where I said the first complete theory is who you name it for. So, Lemaitre had the mathematical derivation. He used Hubble’s unpublished, provided to him freely, observations taken with Humason of the expanding universe, used them to determine an early value of the expansion constant that didn’t differ a lot from Hubble’s early value. And he published all of the work but did it in French.
So, his crime is he published in French. And that’s why he doesn’t get remembered. And then, Hubble came out with a better writeup with more advanced data and said, why, yes, didn’t then reference Lemaitre, who he discussed this stuff with, who he provided data to, didn’t cite him. And after Lemaitre said, but I did this first, and then translated the paper, he just omitted the thing that would have given him credit for it because he was that kind of a guy.
Fraser: Yeah.
Pamela: Do we erase him from history, which is what was on the route to happening?
Fraser: I think I said what I think. And so, I don’t think I need to double down on saying what I think, which is – when you use Stellarium and you look at an object that has a Messier number, it also has an NGC number, and it can also have an IC number, and it will have a Sinbad number. And there’s all these other numbers that it’s gonna have as well. And so, things will have multiple names.
And I think the history of these concepts are fascinating and well worth going back in time to figure out and understand the best possible story that you can. And the moment that you find plausible evidence that somebody came up with something earlier, you slot that into the history, and you should recognize it in the official places to make sure that it does get accepted and put in there. But this is a history problem, not a science problem.
Pamela: The science is the same.
Fraser: Yeah, the science is the same. This is a history issue. It’s a history problem. And I’m sure historians can already talk about how complicated naming things are and what impact that has. So, we’ve got to wrap things up. But when will we know the final answer?
Pamela: No idea. We will bring it to you.
Fraser: At some point in three months, some person is gonna show up with an envelope. They’re gonna hand it to you. You’re going to make a mark. They are gonna take that envelope away, and the answer will happen.
Pamela: I suspect it will be a checkbox on a website, and then a press release. However it takes place, we’re gonna bring all that information to you here on Astronomy Cast.
Fraser: Awesome, I can’t wait to hear the answer. Thanks, Pamela. Welcome back.
Pamela: Thank you, Fraser. Glad to be back and glad to see you.
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[End of Audio]
Duration: 32 minutes

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