What is the universe made of? Humans have pondered this question for centuries, but now astronomers are coming up with some surprising ideas.
Stars are a logical component of everything that is since we see thousands of them when we look up into the night sky. We now know that what we see is just a tiny fraction of the stars that shine off in the depths of space. But stars account for only one half of 1% of everything that makes up the universe.
So what is the other 99.5%? About 25% is something we know almost nothing about. We cannot see it because it does not interact with light. It does have gravity, and we can infer some ideas about it because of its pull on stars and galaxies. We call it dark matter.
That leaves a lot left over, about 70% of the universe. Astronomers have been scratching their heads over this one, and one of the few things they know about it is its name, dark energy. That really does not count since they named it themselves.
So what is dark energy, and should we worry about it? Quoting Wikipedia, dark energy is a negative repulsive energy, the opposite of gravity. That does not sound too bad. There are times when we could all do with a little less gravity. So what does it do?
Back in the early 1900s the famous American astronomer, Edwin Hubble, made a remarkable discovery: the universe was getting bigger and bigger. Up until this point everyone thought the universe was static, an idea that can be traced back to Aristotle. The universe was just out there, minding its own business, as it had since time began and would forever.
Hubble’s ideas changed all that. As an interesting footnote to history, Einstein’s equations showed that the universe was expanding, but he did not believe it so he introduced an error into his equations to keep the universe as it was. When Hubble showed him proof that the universe was actually getting bigger, Einstein retracted his error and admitted that it was the greatest blunder of his career.
So the idea of dark energy was invented to explain why the universe is expanding. It is the push, embedded in space itself, that is carrying distant galaxies away from us like we have bad breath.
One way to look at the universe is that dark matter, which adds a lot of gravity to everything, is the parking brake slowing it all down. Dark energy is the gas pedal speeding it up.
Some astronomers think that without dark energy we would not be able to live on this earth. Why? Because without it the stars would be too close together. When one explodes, which all stars do eventually, it might be close enough to blow us right off our little planet. That is an interesting idea, but not one that everyone agrees with.
Give it a Rip?
One idea that many astronomers do agree on is that dark energy may very well be our doom. They are uncomfortably aware that if their equations are tweaked ever so slightly, then dark energy turns into something ominous, phantom dark energy.
That sounds kind of scary, and it is. Imagine dark energy running amok through the universe not only pushing the expansion of the universe but also tearing everything apart down to the very atoms in our bodies. People that study such things call it the Big Rip and say it is one way our universe could end.
When will this happen? Probably not soon enough to become a campaign issue in 2024. I have seen estimates of 100 billion years from now and up. To put that in perspective the universe itself is only 13.8 billion years old.
If you find yourself out under a spectacular night sky, be sure to pause for a few moments and take in the stars and planets up there. I have been keeping an eye on Venus, low in the southwest just as it gets dark. She is getting higher in the sky and easier to spot. Looking higher Jupiter is the next bright one and reddish Mars is higher still.
All the bright stars of winter are on display so enjoy them while they are still visible and do not worry about dark energy. We would never see it coming anyway.