By David Ward
The universe is a big place. We know that there are perhaps trillions of galaxies out there, each with hundreds of billions of stars. If these sound like big numbers, they are. Our minds simply cannot grasp the vastness of it all.
Astronomers estimate that there are more stars visible in their telescopes than there are grains of sand on the planet earth. Think about that for a moment. If you counted each and every grain of sand on every beach, and in every desert, that number would not equal the number of stars up in the sky.
How big is the universe really and can we see all of it? We realize here in the 21st century that there is a horizon line out there that we cannot see over. No matter how large or how advanced a telescope we might build, we will never be able to see any farther.
What is going on with that? The universe is expanding, getting bigger and bigger all the time. The way we would like to think about that is that the galaxies are all rushing outwards through space getting more and more distant from us like we have bad breath or something. That is not really what is happening, however. Space itself is expanding, carrying all the galaxies along with it like in a vast tide.
Look at the space between your fingers. That space is actually getting bigger but it is not a lot of space so it is not expanding very much. You could look at it for a million years and not notice any change. The space between us and a distant galaxy is a lot of space and it is expanding a lot faster. The farther a galaxy is from us the more space there is to expand and the faster it is traveling away from us.
Empty gets larger
You may be wondering, how can space expand? It is just empty space, isn’t it? I do not have an answer for that question and nobody else does either. We do know it is happening as crazy as it may sound. So there comes a point way out there that the galaxies are actually receding from us faster than the speed of light. Their light will never get back to us and we will never be able to see them and they will forever be cut off from us.
So what is out there deep in the depths of space beyond that horizon line we cannot see beyond? We live in a society so wealthy that we can afford to pay very smart people to think about big questions like this. Most astronomers and cosmologists agree that the universe is infinite.
If you ever wake up in the night and cannot get back to sleep, just think about that idea, infinity. You will either go right back to sleep or you will not sleep at all for the rest of the night. First of all it means that things out there are big, really big. Also it means that the stars and galaxies go on and on forever, never coming to an end.
In an infinite universe there is room for a lot of stuff to happen. Those smart people say that an infinite number of things happens an infinite number of times in an infinite universe. That means that everything the human imagination is capable of dreaming up is happening somewhere in that vastness. Every crazy science fiction movie you ever saw is actually real somewhere. If that does not worry you, then think about this. Everything we cannot imagine is happening too, and that is what scares me.
Also it means that somewhere out there is galaxy just like our own Milky Way. In that galaxy there is a star exactly like our sun. Revolving around that star is a planet just like our own earth. It is not like this is a maybe or a possibility. It is inevitable, if the universe is infinite like all those smart people say it is.
On that planet is another me writing this column and another you reading it, right now. Maybe the only difference between this world and that one is that you cannot find your car keys tomorrow morning and are almost late for work. So make sure you know where your car keys are. You would not want to find yourself in an alternate universe trillions of light years from home!