Science

A Cosmic Thanksgiving

The Andromeda Galaxy, seen in ultraviolet light.

The Andromeda Galaxy, seen at ultraviolet wavelengths. This mosaic covers a region 200,000 light-years wide and is made up of 330 individual images taken by NASA's Swift satellite. NASA hide caption

itoggle caption NASA

It is the season to give thanks and here at 13.7 it shouldn’t be any different. Let’s lift our heads up a bit and take a good look around. No, this is not going to be a depressing romp about the state of the economy or the nation or the world. Look further up, to the sky. We are here to celebrate and celebrate we will.

Let’s start with our universe. What an amazing place to be alive! Some 200 billion galaxies, each with some 200 billion stars, a good fraction of them with planets, and these planets with moons. Trillions of worlds besides our own, each unique, each with its own history, with its own mysteries and wonders.

If Copernicus thought (he didn’t, but many who followed him did) that displacing the Earth from the center of the cosmos would make the cosmos and the Earth less interesting, he was quite wrong. This expanding fabric of space, with texture so rich we couldn’t have imagined even 20 years ago, will never cease to amaze us.

What’s beyond space? What happened before the big bang, the event that kick-started time? These are the questions so many want to understand. Can we? Yes, we can!

Our present measurements — and remember, all we can say about the world is what we can measure of it; the rest may be cool to talk about in parties but it’s speculation until measured — indicate that space is flat: this means that it goes on forever.

Now, do we know that for sure? Not really. All we can say is that the portion of space that we can measure, that is, the portion that is delimited by the distance light traveled since the initial bang 13.7 billion years ago, is flat or very very nearly so. Think of a beach and the horizon in the distance. You know the ocean doesn’t end there, just what you can see of it. Well, it's the same with space. We can see as far as light traveled since the beginning of time, a staggering 45 billion lightyears, in round numbers. Beyond that there is more space, and probably more galaxies, more stars, more planets. (Why 45 billion lightyears and not 13.7? Because light gets a “push” from the cosmic expansion as a surfer riding on a wave and covers a larger distance than only 13.7 billion light-years.)

How can we be so certain? Because our measurements tell us that the laws of physics and chemistry are the same across the vastness of space. How mind-boggling is that? We can tell what a star is made of without ever needing to go there; we can tell how galaxies formed some 10 billion years ago, way before Earth even existed. As we look into space we look into the past: the farther away, the farther into the beginning. Who said there is no magic in science?

And what about “the” beginning? Well, we don’t really know. But we do know a lot of the cosmic history all the way down to one trillionth of a second after the big bang. Not too bad for a science that is only about 400 years old, right? We also know that there isn’t much sense in asking what happened before the big bang. Kind of asking who were you before you were born. Since there was no time ticking for you, there was no you. As Saint Augustine cleverly said some 16 centuries ago, space and time came into being with the cosmos. No cosmos, no space and no time.

If only it were so simple.

Some speculate that our Universe is just a chunk of a much larger (how large?) entity, a multiverse that represents all possible realizations of universes. Or almost all. In each of them, the laws of nature may be different, and most would blatantly fail to become anything interesting. As in no life.

So, give thanks to our universe, the one among the many that has the right properties to live long enough so that galaxies and stars can form, and then planets and, in some of them, life.

But wait! Don’t get carried away. Our universe couldn’t care less about life or about preserving it. Be suspicious of arguments that claim that our universe is just right for life!

Just look at our cosmic neighbors, barren worlds, desolate and fascinating. Strip away our thin atmosphere, our protective magnetic and ozone shields and Earth would turn barren too, a dead world incapable of harboring life. (Or at least complex life. Maybe simple life is resilient enough to survive in very extreme conditions.)

So, it’s not really to the universe that we should be giving thanks but to Earth itself, our amazing, life-bearing, life-preserving planet. The more we move outwards to explore other worlds, the more remarkable our own becomes. We should all, collectively as a species, be giving thanks to our world. Most of all, for its patience in taking so much abuse from us and still letting us stick around. Few mothers would be this patient.

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