So people and planets and animals and clouds and gas and dust and stars, asteroids. Right?Ībout four percent of the mass energy in our universe is made up of ordinary kinds of matter that we're familiar with, matter made of atoms. I mean, it wasn't long ago that we discovered that 70 or 80 percent of the matter is dark matter that we seem to have no way of really observing in any traditional sense. The Carina Nebula, the "Cosmic Cliffs," is a star nursery 7 lightyears across. Not only do we not know, but we should be careful about what we claim to know. To me, it drives home a proper amount of humility, and also a clear sense of our fallibility. And that means that we have what's called a cosmic horizon. And what that makes very clear is that we are eventually going to hit a wall, right? We're not going to be able to see greater distances than there has been time for light to reach us since the universe, at least the observable universe, began in the Big Bang. Now you're seeing objects as they were in the very early universe. When you extend these sorts of questions to objects that are tens of millions, hundreds of millions of lightyears away, like Stephan's Quintet, or the galaxies at the very edge of our view-now you're exceeding 13 billion lightyears away. It's an incredibly limited amount of information, right? From what we understand about the observable universe, everything you can see goes back about 13.8 billion years, but we're only able to see what light has arrived at us from visible matter in the very short span of human history. And if you just think about what we've been able to gather throughout all that time, it's an incredibly thin sliver of information about what's out there. We've developed fancy technology, space telescopes. We're looking at the world, and we’ve used our eyes for most of human history. It reminds me just how limited our epistemic access is as human beings. When I look at something like the Carina Nebula, I always think about how something that’s 7,200 lightyears away, what you’re actually looking at is the thing as it was 7,200 years ago. ( There is.) What we've learned relatively recently calls into question the very idea that "now" is different from "then." Our conversation has been edited for length and clarity. As Harvard University physics lecturer Jacob Barandes explained when we spoke on Thursday, these aren't just questions of our existence, or the silly question of whether there is other intelligent life out there. These considerations are where astronomy bleeds into philosophy. A snapshot of a thousand galaxies or more, each containing billions of stars, that actually "covers a patch of sky approximately the size of a grain of sand held at arm’s length by someone on the ground." So-called "Cosmic Cliffs" that are 7 lightyears high, when one lightyear is about 6 trillion miles. These are the kind of things that come to mind for me when I look at the first five photos from the James Webb Space Telescope, released this week along with stats and facts that will put your brain in a pretzel. Certainly, when you really process the distances between us and anything else-forget a place we might actually want to live, and no, Mars does not qualify-you really start to appreciate our nice little planet here and the opportunity we have to live on it. But operating on this knowledge, that our existence is so unlikely and finite and delicate in the face of all there is, would encourage us all to start working together to keep ourselves and our species in the game. Maybe telling people they're ants on a tiny rock in one solar system in a galactic backwater wouldn't be great politics.
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