The Earth and the other planets, the stars, the galaxies, the space around them and the energy that comes from them are all part of what we call the universe. I like to believe that there are parallel universes, and we are just one slice of a huge "loaf of bread." Interstellar, starring Matthew McConaughey, is one of my favorite sci-fi movies to date, because it explores the possibility of higher dimensions and makes our solar system very small in comparison to what's out there.
If you haven't seen it yet, I highly recommend it! Check out Roger Ebert's review.
Most astronomers believe that between 8 and 16 billion years ago, all matter and energy, even space itself, were concentrated in a single point. There was a tremendous explosion -- The Big Bang -- and within a few minutes the basic materials of the universe, such as hydrogen and helium, came to be. These gases collected together into large bodies called galaxies. Today, the universe still seems to be expanding, as evidenced by studying the radiation from The Big Bang.
Huge families, or superclusters, of galaxies are racing away from all the other clusters at incredible speeds. If the Big Bang has given them enough energy, the galaxy superclusters may keep on racing away from each other until the last star has died. But if their gravity is strong enough to slow them down, everything in the universe will eventually cascade in on itself in an event we call the Big Crunch. Then, perhaps another cycle will begin.
A Small Part of a Large Scheme
We live on the Earth, just one planet in the solar system. Our solar system is part of the Milky Way, just one galaxy in a cluster of galaxies. These clusters gather into superclusters of galaxies, all of which are expanding outward.
Scientists measure the vast distances in the universe in light years -- the distance light travels in a year. If you do the calculations, you'll find that light travels about 186,000 miles per second, which is equalent to an object travelling around the Earth seven times per second! The Andromeda Galaxy, the closest galaxy we have discovered so far, sits 9 quintillion miles away from us. It is difficult or impossible to imagine this huge distance, so we say that it is 2 million light years away.
The Big Bang took place long ago, but most of its work was accomplished in a ery short time. Hydrogen was created quickly, and the galaxies began to form soon after. As stars within these galaxies exploded, the heavier elements, such as carbon (the basis of all organic life as we know it), were formed. The ceiling of stars we can see on a clear night is just a tiny part of the universe, which is immense in both time and space. The expansion of the universe will be reversed if gravity is storng enough to pull everything together again.
Back to the Past
In 1965, scientists Arno Penzias and Robert Wilson were testing a radio antenna when they detected strange energy emissions. They searched for the source of these emissions and had a very weak level of radiation. The existence of radiation confirmed the theory of some astronomers that the Big Bang had left a cool afterglow in space. In 1978, Penzias and Wilson won the Nobel Prize in Physics for discovering this important fact about the beginning of the universe.