The universe is getting bigger. It's growing faster and faster, like a balloon. (Don't worry, it's not going to pop.) The space between stars is always growing farther and farther apart. How do we know this? The universe is so big and we're so small. This is like a flea on a dog telling you how big the world is and how it moves around the sun. No wait, even smaller! It's like the tiniest hair on that flea thinking about how our galaxy spins. Anyway, the point is that we are small and the universe is huge. How can we tell that it's getting bigger from way down here? We have something that the fleas""or, the hairs on those fleas""do not.Open your eyes. Look.
If you look really hard you might be able to see the 1.6 million galaxies found so far in the universe. You may need special instruments.
Our first hint is the stars. When you look up at those little lights twinkling in the sky, you are looking at light that has come from up to 142,000,000,000,000,000,000,000 kilometers to reach your eye! Now, you may not be able to see it, but all of those lights are just a little bit red. Redshift
is the color of light given off by something when it's moving away from you. As something moves away, the waves of light coming off it become stretched out farther and farther, so they make lower frequency light, like red. When we look out into space, everywhere we look, the stars are leaving red in their wakes. They are getting redder and redder . . .Get out your instruments. Listen.
So we can prove the universe is expanding just by looking at the sky? No, that would be bad science. When we point our instruments into the night sky, we find heat that is flowing toward us in the same amounts no matter where we look. The Cosmic Microwave Background
is the energy from the Big Bang that is still moving out into space. This is like the hot air inside a balloon pushing the edges out, making it bigger and bigger and thinner and thinner. While the things in the universe are getting redder, this edge grows colder. Growing quickly, it's almost like it's a teenager. I mean it is around sixteen . . . billion years old.
Turn on your brain. Think.
Just wait, in another billion years, the universe will be even bigger than it is today.
Now here comes the strange part about our growing universe. When you look at the stars, you are looking at history. The light from stars takes so long to reach your eyes that a star can die and we will not know about it here on Earth for millions of years. Other stars that were born a long time ago are so far away their light hasn't reached us yet, so all we see is dust and gas. Space-time
is the theory that space and time are connected and affect each other. Without the growing universe, time could not go forward. If you understand these things, you are way better off than Einstein when he was your age.
It's not easy for us to figure out that the universe is getting bigger. We have to use our eyes and our instruments and our brains to figure out that the stars are red and are getting redder, left over energy is pushing the universe apart, and that time and space are one. Not too bad for a person who, next to the all of space, is smaller than the smallest hair on a flea . . .
Sky Server. "The Universe" Sky Server, 2009. <http://skyserver.sdss.org/dr1/en/proj/basic/universe/>
How Stuff Works. "Einstein, Relativity, and the Space-Time Continuum" Discovery, 2012. <http://science.howstuffworks.com/warp-speed2.htm>
Scientific American. "What is the cosmic microwave background radiation?" Scientific American, 2004. <http://www.scientificamerican.com/article/what-is-the-cosmic-microw/>