James Webb Space Telescope images show early galaxy formation : Short Wave If you ask a physicist or cosmologist about the beginnings of the universe, they'll probably point you to some math and tell you about the Big Bang theory. It's a scientific theory about how the entire universe began, and it's been honed over the decades. But recent images from the James Webb Space Telescope have called the precise timeline of the theory a little bit into question. That's because these images reveal galaxies forming way earlier than was previously understood to be possible. To understand whether it's physics itself or just our imaginations that need help, we called up theoretical physicist Chanda Prescod-Weinstein.

Got questions about the big and small of our universe? Email us at shortwave@npr.org.

What galaxies forming earlier than scientists thought possible means for physics

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EMILY KWONG, BYLINE: You're listening to SHORT WAVE from NPR.



How did it all begin? The universe, I mean. Well, it's complicated.

CHANDA PRESCOD WEINSTEIN: You know, this is actually a strangely controversial topic to discuss.

BARBER: It's a deep, existential question that philosophers and religions have given answers to. Science is a separate discipline than those two, but it does offer some mathematical answers wrapped up in the dominant theory that's been around for decades, the Big Bang.

PRESCOD WEINSTEIN: So one way of thinking about the Big Bang is it's the moment from which all other time and, therefore, space-time follows. Those of us who work in the field of cosmology, which I do, sometimes use the phrase Big Bang to refer to the time period after space-time begins when everything's very hot and very compressed.

BARBER: That's Dr. Chanda Prescod-Weinstein, a theoretical physicist at the University of New Hampshire. As a physicist, it's her job to ask these deep questions about how we and the rest of the universe got to this moment, how the universe began and how it evolved. The whole chain of events started really, really fast with what physicists call the Hot Big Bang.

PRESCOD WEINSTEIN: Then immediately afterwards, there is a phase that's less than a second long called the inflationary period, where space-time expands exponentially and becomes rapidly large.

BARBER: And the universe, it starts to heat up as part of the preheating phase. It's a mysterious, ephemeral phase lasting a few minutes.

PRESCOD WEINSTEIN: We don't really understand what happens at this point except that we know it needs to happen so that other things like the Hot Big Bang can start happening. So particles start to form. As we get particle formation, initially, the universe is in this kind of hot plasma, particle-stew situation.

BARBER: Then hydrogen and helium form. And somewhere around 380,000 years later, the universe starts to chill out, and the first inklings of the universe as we know it today start to appear.

PRESCOD WEINSTEIN: And light starts being able to stream freely through the universe. That is actually what we call the cosmic microwave background radiation. And that's something that we actually still see today. We can observe it with specialist types of microwave telescopes, which is pretty cool. At that point in time, one of the pieces of information that's imprinted in the cosmic microwave background, which we also call the CMB, is little spots where there are little fluctuations in how hot the universe was. And this is really one part in 10 to the five, so it's a very small variation. But we think that those variations correspond to where there's a little more stuff and a little less stuff. And that's actually the beginning of the formation of structures in the universe, because where there's a little more stuff, gravity causes more stuff to collect together. And so you get the first formation of stars, and then those stars start to collect together. And you get stars and galaxies, and that's really the beginning of us.


BARBER: Unless that wasn't exactly how it all worked out or how it all timed out, which is what scientists are starting to think because the new James Webb telescope, or JWST, has taken the most distant, the oldest images of our universe we have ever seen. And in these images, scientists are seeing that galaxies show up way earlier than we thought possible.

Today on the show, as our tools become more advanced, will we have to rewrite the origin story of our entire universe and the laws of physics themselves? Or do we just need more imagination when it comes to how to use the physics we already have? I'm Regina Barber, and you're listening to SHORT WAVE from NPR.


BARBER: OK, Chanda. So these new images from JWST, they're making a lot of astronomers and a lot of cosmologists kind of excited that we're seeing these galaxies so early. Like, can you break down why that is?

PRESCOD WEINSTEIN: Right. So let me start by saying that in the period when we were preparing for the launch of JWST, one of the reasons that I was so excited for this incredible feat of, like, human engineering and collaboration was because we were going to see baby galaxies. That's what I told people all the time. We're going to see baby galaxies. We're going to see baby galaxies.

BARBER: Yeah, no. I totally wanted to see baby galaxies, too. But what did those baby galaxies look like? I have a photo that we're going to put as the episode photo so listeners can see it. Can you describe what you're seeing in this image?

PRESCOD WEINSTEIN: So I'm seeing that there are some dark matter in the foreground and also that space-time has expanded so much between the time when the light was emitted and when it has arrived at us that space-time is actually acting like a funhouse mirror.


PRESCOD WEINSTEIN: And I'm also noticing how many very reddish objects there are in the image. And so, of course, it's - whenever we're looking at images from space telescopes and really even ground-based telescopes, the images that are shown to the general public have usually had some coloring restored to them, and so we're sometimes not looking at the colors themselves. And in the case of JWST, this new amazing, great observatory, it's actually an infrared instrument, and so it's not looking in the wavelengths of light that we see with our eyes. And so everything - because it's looking in the infrared, everything is reddish.


PRESCOD WEINSTEIN: But also, the people who did the coloring for this image are also cueing to us, when we see things in the image that are particularly red, that that stuff is especially red compared to the other parts of the image. And what redness signals to us often is age.

BARBER: Yeah. When we're looking at galaxies, very distant galaxies, specifically. When we're looking at nearby red stars...


BARBER: That's something else.

PRESCOD WEINSTEIN: Yes. What has turned out to be even more exciting than just seeing baby galaxies is that galaxies are being born, apparently, earlier than maybe we thought that they could be. That has definitely caused us to go back and critically reflect on the timeline that we had in mind for when galaxies should form. And obviously, this is strongly related to, what is the timeline for when stars first start to form and the rate of star formation? Maybe it's a lot higher than we thought it was. And that has implications for the evolution of galaxies because stars are radiating light.

And we don't think about this in our everyday lives, but light actually has pressure associated with it. So you have enough light, and it will actually create pressure that can push on things. And so that light pressure can actually push on the gas that's in the galaxy. It provides kind of a check on star formation because it's counterbalancing the effect of gravity. And so the star formation rate plays an important role in kind of the engine of the galaxy's life and evolution.

BARBER: Yeah. I remember being so confused about that. That this idea that gravity is pulling things in and making stars, but there's also this energy that's coming out of the stars that's keeping stars from being created, like, around it. So this kind of like, the cycle of - I think we call it feedback, right?


BARBER: And so because we have this new discovery that many of these galaxies might be happening earlier in our universe, what implications is that? Like, the fundamentals of how, like, the universe is made - is it - is that going to be affected by these discoveries?

PRESCOD WEINSTEIN: I think it could raise interesting questions about the impact of dark matter on structure formation and how we understand the significance of the kind of matter that we're familiar with from our everyday life, what we call baryonic matter. As opposed to dark matter...

BARBER: That we can interact with.

PRESCOD WEINSTEIN: Right, as opposed to dark matter. We can't interact with dark matter, but we interact with baryons. There are lots of different ways that baryons interact with each other. There's electromagnetic interactions. There's gravitational interactions. I think that these results from JWST are calling into question our understanding of how all of those pieces fit together to create a correct timeline for the evolution of what we call large-scale structure - so galaxies and clusters of galaxies. Even as we believe that we understand the fundamentals about baryons, we still have a lot to learn about what those fundamentals translate into in practice and complicated situations.

BARBER: So what does that mean for the standard cosmological model then?

PRESCOD WEINSTEIN: So I think part of the question that, certainly, people were prompted to ask when we first started getting these really exciting images from JWST and also the spectroscopic data that we've gotten is whether our standard cosmological picture is wrong, like, whether we have a fundamental misunderstanding of what kind of stuff is in the universe, how much of that stuff there is and what the large-scale geometric picture of the universe is.

BARBER: But OK. Is it not going to break physics then?

PRESCOD WEINSTEIN: I think that people have already started to veer away from that. Or people are at least skeptical of it and seem to think that maybe it's much more a question of understanding the complicated physics of how baryons interact with each other and that maybe some of the assumptions that we've been making in our simulations are not correct. And so I think that that is a question that I would like to see explored first. I'm always very mindful of what the theoretical physicist John Bell said. I'm paraphrasing. But sometimes, when physicists are unable to work out how something can be explained with physics that we already know, that's a failure of imagination. It's not 'cause the universe is doing something weird.

BARBER: Thank you so much, Chanda, for sharing your knowledge of the early universe with us. I had a great time. Thank you so much.

PRESCOD WEINSTEIN: Thank you for having me.

BARBER: Dr. Chanda Prescod-Weinstein is the author of the award-winning book, "The Disordered Cosmos: A Journey Into Dark Matter, Spacetime, and Dreams Deferred." This episode was produced by Berly McCoy, edited by our managing producer, Rebecca Ramirez, and fact-checked by Brit Hanson. Our audio engineer was Patrick Murray. Beth Donovan is our senior director of programming. And Anya Grundmann is our senior vice president of programming. I'm Regina Barber. Thanks for listening to SHORT WAVE from NPR.

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