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The big bang time relativity problem sometimes makes your brain hurt but this is amazing!

I’m so fascinated by the fact that we can look back through time by looking at these distant objects. I wish I went into astrophysics instead of engineering…

I went into astrophysics and came out very discouraged. The researchers actually pushing the envelope are 1% of academia and if you don't find a department with them, you are paddling in the open sea. There is an incredible amount of cruft in academia, not to mention how financially insecure that life is.

Truly, only those who think about nothing but (astro)physics can bear it.

I still love thinking about fundamental problems and upcoming research however. That will never be gone.

I realize my choice was definitely financially driven but in a future where that’s easier with AI, I’d like to focus on things that make my brain tingle.

I used to love engineering but with AI I feel like all the passion (learning things, making brain squeeze) is gone and I’m just managing another resource.

Don’t get me wrong, I like building things. I also like solving challenges and hard problems and I haven’t done that in a few years now.

what do the other 99% of researchers do?

Most research is boring incremental stuff, and very often you will find a dejected or disappointed individual that realizes this. The invention of relativity only made one scientist a household name. I guess everyone else that came before and after were doing nothing at all.

I know a few more household names but he's right.

There's a scene in Good Will Hunting where the two professors talk about Will [0] and Sean (Robin Williams) says it's "There's more to life than a fucking Fields medal". Both are correct but there's only a few names in history that will be remembered as "The Greats".

[0] https://www.youtube.com/watch?v=AjXgJ1gneK8

Everyone I know who studied astrophysics ended up in Fintech doing data science anyway. "illusion of choice"

Well there is Brian May, guitarist from Queen, who finished his astrophysics PhD in 2007 but he is probably an outlier!

I met a few in MarTech as well…

arXiv link: https://arxiv.org/abs/2505.11263v2

Note: I like arXiv links anyway, but in this case something about the page was killing my browser, had to reload a few times.

We're seeing this galaxy as it was 280 million years after the Big Bang. But the universe didn't become transparent to photons until 100 million years after that (https://en.wikipedia.org/wiki/Recombination_(cosmology)). So that's impossible. Who's wrong, Recombination theory or this paper?

Or have I missed something?

I think you've mistaken thousands of years for millions.

As per your own link:

  Solving for z_rec gives value around 1100, which converts to a cosmic time value around 400,000 years

Doh. Thanks.

If it makes you feel any better I had the same exact reaction as you and almost posted the same thing, but managed to catch my error just in time.

Does anyone know if JWST has seen stuff far enough for this effect to kick in?

[Angular Diameter Turnaround](https://xkcd.com/2622/)

Yes, as per Wikipedia that happens much closer to us, at redshift 1.5: https://en.wikipedia.org/wiki/Angular_diameter_distance

(Note: the reason to measure in red shift rather than light years is that when this comes up it suddenly gets very important to be very careful about what exactly you even mean by "how far away is that thing?")

Incredible!

So if I understand this correctly, the galaxy above in the paper is at Z=14.4 and that means it appears in the sky about as big as if it were a very small Z or roughly 350 megaparsecs away?

I think about that one a lot. It goes all the way back to the CMB, which is so "big" that it is literally everywhere you look and the shapes we see were apparently at the quantum scale.

Yes, JWST can see as far back as 300 million years after the big bang.

I love the finding, but I really like the first sentence on their abstract: "JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, z>10, where few such sources were expected."

Unless stunning has a technical meaning I'm unaware of, I like this approach of starting a technical paper with something less dry.

In scientific writing stunning can also be used in a neutral sense to mean far outside the baseline. It does not necessarily carry an aesthetic meaning like stunningly beautiful... :-)

could someone ELI5 for this ignoramus?

It sounds like JWST found a galaxy where one wasn't expected to be for the time in which it takes light to reach where JWST is?

I assume it's important because we expected nothing and there was something?

But I am just guessing, honestly

The Cosmic Microwave Background Explorer was a satellite back in the 1990s that measured the Cosmic Microwave Background of the universe. This CMB is the afterimage of the Big Bang, about 400,000 years after the Big Bang when the universe suddenly became transparent to photons- the earliest images of the universe we can possibly capture in light.

And it found that everything was the same no matter where you looked, to about 10 parts per million. So that is the level of variation in the density of the universe about a half-million years after the Big Bang, the differences are measured at the level of parts per million.

And then back in the 1990s the Hubble Space Telesecope took pictures of the previously most luminous galaxy ever recorded, and it was really far back in time, within half a billion years of the Big Bang. And these luminous galaxies were something that we expected to mean that they were built around gigantic supermassive Black Holes. Which means that in a very short amount of time we must have gone from "everything is the same to parts per million" to "here is a gigantic accumulation of mass concentrated in this one spot so densely that all of our models of physics don't work any more."

And so the Webb Space Telescope was built specifically to look for things in between what the Hubble had seen (in Visual Light) and what the COBE had seen (in Microwave), that is Infrared. It is designed to look for these supermassive galaxies that had Red Shifted (1) so far they had left the visual spectrum and gone into Infrared. Figuring out how all of these super luminous galaxies formed is the main question that the whole thing was designed around.

1: As things move away from us, the photons shift to the red end of the spectrum. According to Hubble's Law, things the faster something is moving away from us the earlier it is in time, and the further its photons are shifted to the right: this is why the Cosmic Microwave Background is in microwave, because it has been red shifted so far it has gone into the Microwave part of the spectrum.

It's a galaxy far far away and more importantly very very old. The image is 13.5 B years old, the photons were created just 280 million years after big bang. It's the oldest thing we have seen so far. And it looks mildly different than what we expected to see

In our current understanding of how universe formed galaxies accumulate gradually and it takes time. This one was quite large already, very shortly after the Big Bang, which is at odds with our understanding.

That's the most authors I've seen on any paper. I counted 46 across 36 separate institutions.

Relevant PhD comics: https://phdcomics.com/comics.php?f=1911

46 authors isn’t that many. Big projects necessitate many authors (e.g. https://arxiv.org/abs/1807.06209)

In high energy physics it can easily be thousands of authors, like in the ATLAS collaboration.

Turns out launching a gigantic camera into orbit and developing a photograph of the beginning of the universe takes teamwork.

Why did we make just an infrared telescope then? Why don't go into even lower frequencies, surely we would detect something too if we just look?

Because near/mid infrared has many uses other than high-z objects, and it’s been something of a relative blind spot to us until now, although before Webb we did have Spitzer.

For far IR/submillimeter observations we had Herschel in space, SOFIA in the stratosphere (flying on a 747), and several large terrestrial telescopes at very high altitudes can also observe at FIR/submm wavelengths. But sure, there are likely many astronomers who would love nothing more than a new spaceborne FIR telescope, given that it’s been more than a decade since Herschel’s end of mission, and SOFIA was also retired in 2022.

For microwave we’ve had several space telescopes (COBE, then WMAP, then Planck), mainly designed to map the cosmic microwave background. That’s the farthest and reddest that you can see in any EM band, 300,000 years after the big bang.

Past microwave, that’s the domain of radio astronomy, with entirely different technology needed. We have huge radio telescope arrays on the ground – the atmosphere is fairly transparent to radio so there’s no pressing reason to launch radio telescopes to space, and their size would make it completely infeasible anyway, at least until some novel low-mass, self-unfolding antenna technology.

This may be a silly question, but would you be able to create an interferometer style telescope array in space via a platform like starlink, ie small, inexpensive sats? Would that reduce/eliminate the need to launch large singular antennas?

That would probably be difficult at optical wavelengths. At radio wavelengths you might have a better shot, but we can build radio interferometric telescopes on Earth and since the atmosphere is relatively transparent at radio frequencies, you probably aren't going to get any advantage by trying to build one in Earth orbit.

Though not the same thing, you may be interested in https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant...

There is a mission concept for a far-infrared interferometer: https://asd.gsfc.nasa.gov/spice/

One would need to go to space for that of course.

The lower the frequency, the larger the wavelength and thus the larger the cupola needed to detect it. That's why radiotelescopes are on earth, they are HUGE.

Radio telescope dishes are huge so that they can receive (or even transmit in the case of Arecibo, which is gone now) a narrow beam. At long wavelengths you need something huge to get a narrow beam.

But you can also use multiple, much smaller antennas to synthesize a narrow beam, and those little antennas are often dishes but can also be very simple and rather small antennas.

interferometry is good for seeing small objects, but not faint objects. for faint objects there's nothing that works better than a giant dish

Excellent question!

The longest wavelengths of light are generally classified as "radio".

So radio telescopes have been tasked to explore the very early universe.

https://en.wikipedia.org/wiki/Reionization

If I understand it correctly, the "Period of Reionization" is first light we can see from processes like stars and galaxies.

There was ionized plasma at the beginning but the universe was like a really thick fog everywhere, and that first light was scattered around and you can't really see stars. As the universe expanded, that fog cooled down, and you could see, but cold matter doesn't emit much light, so there wasn't much to see. It took a while for gas clouds to collapse into the first stars, heating up the gas to ionized plasma once again, so it's re-ionized matter.

The Low Frequency Array, LOFAR, has been used to study this "Cosmic Dawn".

The Square Kilometer Array was designed to explore this era.

But! Not a radio telescope JWST has revealed unexpected, huge globs that seem to be galaxy-sized gas clouds collapsing into (maybe) black hole cores; the thermal emission from the collapse isn't nuclear fusion, so I don't know if those are "stars". But it's very early light.

Honestly, every time a new class of telescope is built, it discovers fundamentally new phenomena.

https://duckduckgo.com/?q=LOFAR+square+kilometer+array+reion...

https://news.ycombinator.com/item?id=44739618

https://news.ycombinator.com/item?id=46938217

I searched "Reionization" and "Cosmic Dawn" plus some favorite telescopes via web and here using the Hacker News search (Agolia).

(Certainly you know the difference between radio and infrared, but I had to look into how those choices of telescope have observed different aspects of Reionization Era, got nerd-sniped, and just had to write it down in a couple of sentences.)

because infrared is the hardest to observe from the ground. Hot objects glow, and the sky is at the temperature where it glows infrared.

It's safe to say that if we are sticking a 6-ton 20ft mirror into space that the scientists probably have a reason for it...

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Lower frequencies are microwaves and radio waves. We already have the square kilometer array.

"just an infrared telescope"

how about you go make yourself conversant with "just" the technical requirements of the main cryogenic pump onboard, leaving out the rest of the thermal management systems for whatever remains of your life, which will have to be long in order to fail honorably.

Sorry, I didn't mean it's easy to build, far from it :). I meant "just infrared" in terms of frequency — why not go further? Is there a gap between the current infrared and radio on Earth?

Wavelength for electromagnetic waves = c/frequency.

So to 'catch' a certain frequency with a receiver the size of the receiver gets proportionally larger as the frequency drops. Focusing light can be done with relatively small gear. Focusing radio waves, especially when the source is distant requires a massive structure and to keep that structure sufficiently cool and structurally rigid is a major challenge. It is already a challenge for the JWST at the current wavelengths, increasing the wavelength while maintaining the sensitivity would create some fairly massive complications.

In the end this is a matter of funding, and JWST already nearly got axed multiple times due to its expense.

I am poking fun (at your expense) at the notion that because the light is already there, adding other sensors would be feasable. Once you grasp the requirements of building an infrared telescope, you will be going, oh!, damn, wow! It's actualy not that deep a dive to get a feel for just how special the JWST is from an engineering perspective, and then a look into just how difficult it will be to get visible light from those distances, which may require a interferometric telescope with multiple huge sub units flying in formation at distances, known to a fraction of the target wave length , but perhaps several hundred thousand km, apart. doable, but :), just

The temperature gradient across that thing is mindblowing.

Controversial idea. Black holes are older than the Big Bang.

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