The edges of knowledge

The brilliant British astrophysicist Becky Smethurst said, "The cutting edge of science is where all the unknowns are."  And far from being a bad thing, this is exciting.  When a scientist lands on something truly perplexing, that opens up fresh avenues for inquiry -- and, potentially, the discovery of something entirely new.

That's the situation we're in with our understanding of the evolution of the early universe.

You probably know that when you look out into space, you're looking back into time.  Light is the fastest information carrier we know of, and it travels at... well, the speed of light, just shy of three hundred thousand kilometers per second.  The farther away something is, the greater the distance the light had to cross to get to your eyes, so what you're seeing is an image of it when the light left its surface.  The Sun is a little over eight light minutes away; so if the Sun were to vanish -- not a likely eventuality, fortunately -- we would have no way to know it for eight minutes.  The nearest star other than the Sun, Proxima Centauri, is 4.2 light years away; the ever-intriguing star Betelgeuse, which I am so hoping goes supernova in my lifetime, is 642 light years away, so it might have blown up five hundred years ago and we'd still have another 142 years to wait for the information to get here.

This is true even of close objects, of course.  You never see anything as it is; you always see it as it was.  Because right now my sleeping puppy is a little closer to me than the rocking chair, I'm seeing the chair a little further in the past than I'm seeing him.  But the fact remains, neither of those images are of the instantaneous present; they're ghostly traces, launched at me by light reflecting off their surfaces a minuscule fraction of a second ago.

Now that we have a new and extremely powerful tool for collecting light -- the James Webb Space Telescope -- we have a way of looking at even fainter, more distant stars and galaxies.  And as Becky Smethurst put it, "In the past four years, JWST has been taking everything that we thought we knew about the early universe, and how galaxies evolve, and chucking it straight out of the window."

In a wonderful video that you all should watch, she identifies three discoveries JWST has made about the most distant reaches of the universe that still have yet to be explained: the fact that there are many more large, bright galaxies than our current model would predict are possible; that there is a much larger amount of heavy elements than expected; and the weird features called "little red dots" -- compact assemblages of cooler red stars that exhibit a strange spectrum of light and evidence of ionized hydrogen, something you generally only see in the vicinity hot, massive stars.

Well, she might have to add another one to the list.  Using data from LOFAR (the Low Frequency Array), a radio telescope array in Europe, astrophysicists have found bubbles of electromagnetic radiation surrounding some of the most distant galaxies, on the order of ten billion light years away.  This means we're seeing these galaxies (and their bubbles) when the universe was only one-quarter of its current age.  These radio emissions seem to be coming from a halo of highly-charged particles between, and surrounding, galaxy clusters, some of the largest structures ever studied.

[Image credit: Chandra X-ray Center (X-ray: NASA/CXC/SAO; Optical: NASA/ESA/STScI; Radio: ASTRON/LOFAR; Image Processing: NASA/CXC/SAO/N. Wolk)

"It's as if we've discovered a vast cosmic ocean, where entire galaxy clusters are constantly immersed in high-energy particles," said astrophysicist Julie Hlavacek-Larrondo of the Université de Montréal, who led the study.  "Galaxies appear to have been infused with these particles, and the electromagnetic radiation they emit, for billions of years longer than we realized...  We are just scratching the surface of how energetic the early Universe really was.  This discovery gives us a new window into how galaxy clusters grow and evolve, driven by both black holes and high-energy particle physics."

Every once in a while I'd have a student tell me, in some disdain, "I don't know why we have to learn science when it could all be proven wrong tomorrow."  My response to that is that science's ability to self-correct is a strength, not a weakness.  How is desperately hanging on to your prior understanding when you're presented with new evidence a good thing?   People like to be sure of everything, but really, are we ever?  Nothing is ever absolutely settled; we sometimes kid ourselves that we've found The Answer, but that's honestly a response born of a combination of insecurity and the desire not to think about the matter any more.

Richard Feynman, in his wonderful book The Pleasure of Finding Things Out, summarized this brilliantly:

There is no learning without having to pose a question.  And a question requires doubt.  People search for certainty.  But there is no certainty.  People are terrified — how can you live and not know?  It is not odd at all.  You only think you know, as a matter of fact.  And most of your actions are based on incomplete knowledge and you really don't know what it is all about, or what the purpose of the world is, or know a great deal of other things.  It is possible to live and not know.

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