Ten things you probably did’nt know about dark energy
Dark energy is the biggest mystery in the cosmos, pervading the vast emptiness of space for billions of light-years. But if you thought you knew everything there was to know about this strange force, think again.
Discovery Space sat down with Michael Turner, a cosmologist at the University of Chicago, to pin down the 10 biggest things you didn’t know about dark energy.
10. Dark Energy’s Discoverer Didn’t Coin the Term
Who came up with the term? “I did,” Turner said. “That’s because when you find something new and weird, you have to name it. It can’t just be ‘the funny stuff that helps the universe speed up.’”
The term is also used to say that it’s different than dark matter, which is yet another weird constituent of the cosmos, and behaves more like energy than anything else that we know of.
9. Albert Einstein First Stumbled on Dark Energy’s Path
Thing is, Einstein didn’t even know it.
The German-born scientist derived an historic ”cosmological constant” to make the universe static — or in other words, prevent gravity from steering the cosmos into a “big crunch” billions of years in the future.
“Instead of counteracting gravity, however, Einstein’s cosmological constant overpowers it and causes the universe to expand at an accelerating pace,” Turner told Discovery Space. “People like to say that even when Einstein thought he made a mistake he was right, but that’s a bit of a stretch.”
If Einstein’s cosmological constant does exist, it’s about four times stronger than he first anticipated.
“We don’t think the universe is static,” he said. “It’s inconsistent with what we see out there.”
8. Dark Energy Could Be Nothing
The “gravity” of dark energy is repulsive, making it a large-scale anti-gravity that acts like an overzealous traffic cop between clusters of galaxies. What’s between those galaxies? Empty space.
“The simplest explanation for dark energy is that it’s associated with something called the ‘quantum vacuum,’” Turner said.
According to quantum mechanics — which explains how the universe works on a small scale — empty space is full of particles living on borrowed time and energy, Turner explained. So it’s not too unreasonable to suggest dark energy might also occupy that “empty” space.
7. Dark Energy Can’t Be Broken into Particles
About 2,500 years ago, Democritus suggested there were four elements in the universe: air, fire, earth and water, later adding “ether.”
“He started on this path that everything is made of indivisible particles called atoms, and that path eventually led us to subatomic particles called quarks today,” Turner said. “But dark energy isn’t made of quarks, or any other particle.”
6. Dark Energy Is Everywhere
According to Einstein’s famous equation E=MC^2, matter can be converted completely into energy, and the universe can be divided into a “pie” of energy.
“One of the most important things about dark energy is that it makes up most of the stuff in the universe,” Turner told Discovery Space. ” however, locally, we don’t notice it.”
The breakdown of the pie is roughly like this:
- 74 percent is dark energy
- 22 percent is dark matter
- 3.6 percent is nearly invisible gas between stars
- 0.4 percent is stars, planets, moons and everything else. Including you.
5. Dark Energy Is the Most Elastic Substance Ever
“It’d be safe to say it’s more than a zillion times more elastic than anything we know of,” Turner said. “Even NASA’s most stretchy material, whatever it may be.”
If one were to “weigh” the energy of dark energy in a large coffee cup, it would be about 1 x 10^-27 grams (0.000000000000000000000000001 grams) or, in other words, not a whole lot.
If you do the math, Turner explained, contracting a volume of dark energy between here and the sun would create enough juice to power the Earth for about nearly 100,000 years.
4. Dark Energy Shaped the Universe
The Big Bang is thought to have kick-started the universe we live in, but after the event, dark energy began to seize its grip on matter and overcome gravity.
“Our universe was shaped by battle between dark energy and matter,” Turner said. “For the first 8 billion years or so of the universe’s existence, the gravity of matter held sway and clusters of galaxies formed.”
Roughly five billion years after that — or about one billion years ago — dark energy took over, and “put its foot on accelerator,” Turner said. “The expansion of the universe began speeding up and no larger structures were built.”
3. Dark Energy May Not be Energy at All
If it’s not made of particles, and may be nothing, is it really safe to call it energy?
“Not in the least bit,” Turner told Discovery Space. “There may very well be no dark energy at all.”
Instead, Turner suggested that Einstein’s ideas about gravity might need to be replaced.
“Few people think Einstein got the last word on gravity. His story didn’t incorporate the details of the universe at the atomic level,” he said, which is what might hold the key to gravity.”
2. Dark Energy Holds the Destiny of the Cosmos
Until we understand what dark energy is, Turner thinks we won’t really know what the fate of the universe is.
“It could continue to accelerate as it is,” he said. “If it does, then in about 100 billion years the galaxies around us will be speeding away from us too quickly to see.”
Another scenario is that the acceleration of the universe’s expansion may be doubled. And that’s bad news for everyone that might be out there — the cosmos will rip itself to shreds.
“We don’t know if the acceleration we see today is accelerating,” Turner said. “If it is, the ‘big rip’ will occur in roughly 20 billion years.”
One last option is equally as frightening.
“Maybe dark energy’s next trick is to decelerate expansion and lead to the collapse of the universe,” Turner said. “We’ve trapped ourselves time and time again believing in the simplest case, only to correct ourselves. If you want to be squeaky-clean correct, we can’t confidently guess the future of the universe yet.”
1. No One Knows What Dark Energy Is
If you thought you were clueless, even the experts don’t know.
“Welcome to the club,” Turner said. “It’s the most profound mystery in all of science. It ties together the destiny of the universe, mysteries about gravity and quantum nothingness. How’s that for a mystery?”