Wednesday, December 29, 2021

Try to wrap your head around this

With ironic and fitting timing, NASA and partners launched the long awaited James Webb Space Telescope on a rocket on Christmas morning, and astronomers around the world erupted in jubilation.

This is the most capable and advanced telescope ever created, greatly superseding even the Hubble telescope, which itself has been spectacularly successful. The Webb's most important feature will be its ability to resolve the most distant objects in the visible universe, and thus to look far back in time, almost to the universe's very beginning.

Look back in time? Yes. When we view extremely distant objects, we're seeing them as they were long ago. That's because the farther away an object is, the longer it takes for its light to reach us. The light from celestial bodies that we see today was emitted in the distant past.

Thus, the Webb will be able to resolve and study the very first stars and galaxies that existed in the early universe, almost 14 billion years ago.

Because the universe is about 14 billion years old, the visible universe—the part we can see—has a radius, from our position, of about 14 billion light years. (It's actually more, but never mind.) Note that a light year is a unit of distance, not time. It's the distance light travels in one year. 14 billion light years is the distance light (the speed of which is 186,000 miles per second) travels in 14 billion years.

So the visible universe is almost unimaginably immense, and scientists believe the visible part is but a small fraction of the entire universe. The parts that we can't see, and will never see, are just too distant for their light to ever reach us. Because the universe is expanding, with the galaxies all moving away from each other at great and increasing speed, there is a "horizon" beyond which the light of very distant objects will never reach us. The more distant an object is, the faster it is moving away from us.

The visible universe contains around 200 billion galaxies, with each galaxy containing many (perhaps hundreds of) billions of stars. There are more stars in the part of the universe that we can see than all the grains of sand on planet Earth.

One of those stars, our Sun, has a planet on which life evolved. Us. But given the vast number of stars in the universe, most of which (we are finding) have planets, it's almost inconceivable that life didn't evolve elsewhere in the universe too, probably many times. It's even likely that great advanced civilizations have come and gone (as ours will) in the universe's 14 billion years of existence.

All of which puts the Genesis account of creation into a bit of perspective, does it not? No Christian (or, in my crowd, Catholic) is compelled to take Genesis literally, and many thoughtful and informed believers do not. But even if you, as most scholars, view Genesis as just allegory, it still represents a decidedly naive understanding of the world that God supposedly created. Which is not surprising for an account that comes from an ignorant, pre-scientific past when the Earth was thought to be the center of everything, when galaxies were completely unknown, and when even stars were not understood. "The firmament" suspended above the ground contained just the nearest objects, in our own galaxy, that could be seen with the unaided eye (but without comprehension) by pre-scientific man. The vast reaches of the universe beyond, which is to say almost everything, were entirely unrevealed.

But it's not just the ancient belief about creation that needs to be revised. What we now know about the immensity of the universe calls into question our very understanding of God's project, whatever it may be. Is it intellectually plausible that God created all this—more stars than grains of sand—for the express purpose of planting mankind on a lonely planet of no particular importance in the vast yawning immensity, so that we might take fleeting root in a "garden," sin, get kicked out, and then be redeemed by having God's Son come down (down?) from heaven to live and die among us?

If that's what God was shooting for, couldn't a far simpler arrangement have done the job? Perhaps God is an over-achiever.

Let's dispense with one untenable objection up front. If you dispute that the universe is as I have said that it is, then you are disputing that which we can see. The constitution of the universe as I have described it is empirical, not theoretical. The purpose of the Webb telescope is to look at what is there, as our previous telescopes have already done with less but still extraordinary detail.

The Hubble telescope in particular revealed that there are galaxies (again, with hundreds of billions of stars each) everywhere we look; that it's impossible to find a part of space that's truly empty. This discovery was driven home in 1995 with the "Hubble Deep Field" investigation, in which astronomers pointed Hubble at a tiny patch of space where, from the standpoint of our most powerful ground-based telescopes, there seemed to be nothing but dark emptiness. That tiny angular region of space that was studied for 10 days represents about one 24-millionth of the entire sky. Almost all the 3,000 objects found there were galaxies. Similar studies of other "dark" regions of space have found galaxies at about the same density. When we look at the composition of the universe, we find it to be very uniform, with galaxies everywhere.

And just this year, data from NASA's New Horizons space probe provided our most accurate estimate so far of the number of galaxies in the visible universe: "only" 200 billion. (Previous mathematical models using Hubble data estimated 2 trillion. But what's an order of magnitude among friends?)

Each of those hundreds of billions of galaxies is itself so vast as to in some intuitive sense be its own universe, at least with respect to its inhabitants' ability to conceive of (let alone traverse) immensity. If you could travel at the speed of light, it would take you more than 100,000 years to get from one side of our own Milky Way galaxy to the other. It would also take that long for a radio signal, and hence information, to get all the way across. Thus communication itself, never mind travel, is impossible at galactic scale. Two-way communication with our nearest neighbor star (Proxima Centauri, which has at least two planets) would be doable but tedious, with a single round trip exchange (say, me dialing your phone number and receiving your "Hello" in reply) taking about 8 years.

Blame evolution, which had other things to attend to, but the scale and composition of the universe is almost unfathomable to the human mind. And remember: Everything I've described is just the part that we can see, and that in turn is but a tiny slice of the entire universe, most of which will be forever hidden from us. Can it really be that all this exists so that Jesus Christ would be born in a stable to live and die on Earth? That those billion stars we can see at night are just divine decoration to light Earth's sky, and the billion trillion beyond them are just extraneous irrelevancy? It defies credulity.

Science can neither prove nor disprove the existence of God. But it can discover the nature of physical reality, and has described it with ever increasing detail and accuracy, with more yet to come from the Webb telescope and its successors. If God really created all that we can see, then the narratives and myths handed down from our distant ancestors about God's purpose are surely wrong. By my lights the best approach is to leave God out of the explanation completely. But if you insist that there be a creator of everything, then I contend you very much misunderstand what that creation is all about.

A belated Merry Christmas.

 

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