The scale of the universe is vast. What we can see of the universe is a sphere about 27 billion light years across, and that’s hardly the whole universe. Our observations of the universe are limited by the speed of light; since the universe is about 13.7 billion years old, we can’t see anything farther than that, since the light would have had to originate from a time before the universe formed. Similarly, we don’t see distant galaxies as they are now—we see them as they were when they emitted the light. So, we can see into the deep past, but not very much into the present. However, it’s enough to say that the universe is huge: 100 billion large galaxies in that sphere we can see, and since there doesn’t seem to be anything special about our corner of the universe, there are so many more we can’t see and will never be able to see. (When I said that in class once, one of my students said it made her sad to know there could be beautiful galaxies she’ll never be able to look at.)
In some ways, thinking about this is daunting. A billion years is a large number when you consider that a human might live to 100 years or so, and the human species itself is a cosmic infant. Our own planet is 4.5 billion years old, and is a smallish world orbiting around a fairly average star in a large but typical galaxy. With the discovery of over 500 exoplanets (and many more potential discoveries by the Kepler probe), we’re beginning to realize how common planets are in the universe. We’re so tiny compared to all of this. On the face of it, it’s cause for anxiety or despair—what value do we have?
On the other hand, I think it’s not right to look to the universe for meaning. Cosmic meaning isn’t going to be forthcoming (and certainly science shouldn’t be expected to provide it!). Put it this way: in a cosmic sense, it doesn’t matter if we start a nuclear war that wipes out every organism on the planet. A distant galaxy will not be affected in any way; even other planets in the Solar System aren’t going to be changed. However, it means a lot to us who live on Earth—it’s easy for us to think of a lot of reasons not to attempt wholesale destruction. I don’t even have to list them! It may be “selfish” to want to survive, but it’s also completely understandable—even though it’s not a point of view that means anything in a cosmic context.
I know there are those who think that means science leads to nihilism, both from anti-science types and even some pro-science people who embrace the nihilism. I disagree: I think asking science to provide the meaning of life is well beyond what it’s intended to do, so it’s failure to provide said meaning is hardly surprising. I think we could all list things that are meaningful that cannot be derived from a theory or experiment in science. Does that make them less meaningful? I love science, and doing, teaching, and writing about science are meaningful activities to me. The activity itself can be said to provide some meaning to me, and that’s good enough.