Gigantic gravitational waves could explain the universe's biggest mysteries

Illustration for article titled Gigantic gravitational waves could explain the universes biggest mysteries

Modern physics assumes the universe is the same all over... but that might not be the case. Until recently, physics held that the universe was contracting... now we're stuck with dark energy. But one moderately insane new theory could explain it all.

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The discovery, just over a decade ago, that the universe is accelerating its expansion rocked astrophysics and forced theorists to invoke the existence of dark energy, a mysterious force that drove this expansion and accounted for as much as 74% of all the mass-energy in the universe. It's not exactly the most elegant solution, but it's the best explanation for the evidence currently available. For a more detailed primer on why dark energy makes more sense than all the alternatives, check out Dr. Dave Goldberg's primer.

As for the cosmological principle, which holds that the universe has the same laws of physics everywhere and the same basic structure, well... there's no evidence yet to overturn that, but there are some strange anomalies. Recent findings indicate the universe might be accelerating slightly faster in one direction than another, and some astrophysicists have actually dubbed an apparent asymmetry in the cosmic microwave background the "axis of evil" because it has such potential to wreak havoc on our understanding of physics, assuming the observations hold up.

That, however, is a very big assumption, because if these anomalies really do exist, then that opens up the possibility that the laws of physics aren't the same everywhere. What was once a relatively straightforward cosmos could become impossibly messy. And, while there's no guarantee that the universe has to be elegant, physics has so far done such a good job explaining the nature of the cosmos that we shouldn't throw it all away for such a radical alternative without very, very good evidence. We're not even close to that point just yet.

But what if there's a middle path, one that acknowledges the existence of these baffling anomalies and leaves multiple centuries worth of physics intact? That's basically the new idea put forward by Edmund Schluessel of Cardiff University. The answer, he argues, is found in gravitational waves, which are disturbances in the fabric of spacetime created by massive gravitational disturbances like colliding black holes or the Big Bang. So far, these waves are too subtle for us to have directly observed, but we're decently sure they exist — again, check out our primer for more.

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Most models of the universe only incorporate gravitational waves with relatively short wavelengths, while Schluessel hypothesizes the existence of waves that are the size of the curvature of the universe, about 10 billion light-years across. The Big Bang is probably the only thing powerful enough to produce such waves — and even then, a curvature-sized wave is one hell a big thing to invoke — and Schluessel suggests they could still be slowly moving through the universe billions of years later.

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The idea is that these waves would be big enough to disrupt our observation of the distant universe, but they would still be too weak for us to easily observe them directly. Waves of this magnitude could distort the cosmic microwave background, he argues, and it could even throw off the light of distant objects to make the universe appear to be accelerating when, in fact, it isn't.

That's potentially a very appealing model, because it in one fell swoop removes the need for dark energy and completely restores the cosmological principle. That's an elegant solution — except for the part where it relies on an extremely exotic form of a phenomenon whose more basic form we still only barely understand, and haven't even directly observed. Besides, while its ability to explain dark energy is a definite plus, it's still an open question whether there's really any problem with the cosmological principle — the evidence there is inconclusive at best, and the apparent anomalies may just be errors in observation.

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Still, it's an intriguing hypothesis, and one that probably deserves some followup. Schuessel is optimistic that the next generation of telescopes will be powerful enough to detect evidence of these waves. But, for now, it isn't really any more elegant than the dark energy model, and it's got way less evidence backing it up.

arXiv via Technology Review. Image by Tod Strohmayer (GSFC), CXC, NASA, Illustration: Dana Berry (CXC).

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DISCUSSION

Welshidocs and the Three Quarks:

There was once a family of quarks who lived in a cozy cottage in the farthest reaches of space. There was a great big Papa Quark, a medium size Momma Quark, and a little tiny baby quark.

One morning Mama Quark cooked them some unaccounted-for mass for breakfast. As the mystery-breakfast was both hotter and moving faster than predicted, the three quarks decided to take a walk in the darkness while it cooled.

They had not been gone long when a physicist from Cardiff named Welshidocs came along. He had been picking Bosons and had wandered into the depths of infinity. When he saw the three quarks' cottage, he smiled and clapped his hands. "How elegant!" he cried. "I wonder who lives there?" He stood on his toes and peaked into the Computer Model. There didn't seem to be anyone home, so Welshidocs opened the door and went right inside!

The first thing he saw was the table set with three bowls of unaccounted-for mass; a great big bowl for Papa Quark, a medium size bowl for Momma Quark, and a tiny little bowl for baby quark. "Oh, that Nobel Prize in Physics smells so good!" Welshidocs said. Then, as he was feeling a little hungry, he picked up a spoon and tasted the mystery-breakfast in the Great Big Bowl.

"OUCH!" he cried, dropping the spoon. "That mass is MUCH too arbitrarily assumed to be spherically symmetric!"

He tasted the doctrine in the medium size bowl. But that chaos was MUCH too cold.

Then he tasted the ideas in the tiny little bowl. "Mmmmmm," he said. "This set of assumptions is JUST right!" so he ate it all up!

Having eaten his fill, Welshidocs moved into the living room and climbed into the Great Big Superstring Theory that belonged to Papa Quark. "Oh, no!" he said. "That theory is MUCH too hard."

Then he clambered into Mamma Quark's Classical Mechanics Theory "Oh, no," he said. "That theory is MUCH too soft!"

Next, he dropped himself down in Baby Quark's Dark Energy Theory. "Ahhhh," he said with a smile. "This theory is JUST right!"

Just then there was a loud CRAAACK! and Baby Quark's theory broke right through!

Welshidocs stood up and dusted himself off. Then he climbed upstairs to the bedroom. There he saw three Gravitational Waves all in a row. "Oh," he said, yawning, "I am feeling sleepy."

So he pulled down the covers and climbed into Papa Quark's Great Big Gravitational Wave. But he quickly jumped down. "That wave is MUCH too hard!" he said.

Then he tried Mamma Quarks's Reasonably Observably Sized Gravitational Wave. But it was far too soft.

So he climbed into Baby Quark's Curiously Perfect Gravitational Wave. It was JUST right. Soon Welshidocs was lulled fast asleep!

A little while later the Three Quarks returned from their walk. They were feeling very hungry and were looking forward to eating the nice bowls of tasty unaccounted-for mass.

Suddenly Papa cried out in his Great Big voice, "Someone has been eating my spherically symmetric mass!"

Then Mamma cried out in her medium size voice, "Someone has been eating MY chaos theory!"

And Baby Quarkvcried out in his Tiny Little Voice, "Some has been eating my wild hokum. And they've eaten it ALL UP!"

Then the Three Quarks saw their theories near the fireplace.

"Someone has been sitting in my hypothesis!" Papa Quark said in his Great Big Voice.

"Someone has been sitting in MY hypothesis!" Mamma Quark said in her medium size voice.

"Someone has been sitting in MY hypothesis," Baby Quark cried in his tiny little voice. "And now it's BROKEN!"

Then the Three Quarks went upstairs to the bedroom.

"Someone has been sleeping in my Wave, which I can observe although the wave itself is inconceivably large!" Papa Quark shouted in his Great Big Voice.

"And someone has been sleeping in MY Wave of reasonably observable size that I have no evidence of existing!" Mamma Quark exclaimed in her Medium Size Voice.

"Someone has been sleeping in MY Fermi Paradoxical wave," Baby Quark squeaked in his Tiny Little Voice. "AND HERE HE IS!"

Just then Welshidocs woke up! When he saw the three quarks standing around him, he leaped off the Wave and ran down the stairs and out the door.

He didn't stop until he was wee, wee, wee, all the way home.

And the Three Quarks never saw Welshidocs again!