The Big Rip Theory says the universe could end in tears

Some say the universe will end with a new Big Bang. Others say the cosmos will eventually succumb to entropy. But what if neither of those things happens? A recent theory says the universe will just tear itself apart.

The Big Rip Theory might be the scariest scenario for the end of everything we've come across.

Top image of the Andromeda Galaxy, via NASA/JPL-Caltech.

The Big Rip Theory says the universe could end in tearsS

What happens in the Big Rip?
Most experts believe the amount of matter in the universe will cause the expansion of the universe to slow down — and the universe may even contract once again to a single point, causing another Big Bang. But if there's enough dark energy in the universe, it could keep expanding indefinitely, leading to the Big Rip.

According to this theory, the universe's rate of expansion would increase over time. This is sort of like a kid on a tricycle careening down a 100-mile-long-hill without brakes. At one point in the future, the expansion would cause galaxies to separate, then planets, and eventually, individual atoms. This separation, a "ripping" of planets and atoms, leaves the universe entirely devoid of structure.

The Big Rip Theory says the universe could end in tearsS

What we know
Whether the Big Rip Theory is true depends on a particular type of dark energy — called phantom energy. Phantom energy is present when the ratio of dark energy pressure to energy density is less than -1, which means the dark energy pressure is greater than its energy density. That, in turn, allows the universe to keep expanding and accelerating outward, until the universe is ripped apart.

Robert Caldwell, a professor of Physics & Astronomy at Dartmouth College, puts forth the possibility of the Big Rip in his 2003 paper Phantom Energy and the Cosmic Doomsday. In the paper, Caldwell and his colleagues take a look at what would happen if the ratio between dark energy pressure and dark energy density being -3/2 (or -1.5 if you are not a fan of fractions). In this case, the Big Rip will occur approximately 22 billion years from the present, with the Earth exploding about 30 minutes before the finale.

The trouble is, we don't actually know the ratio between dark energy pressure and its own energy density. Current data from NASA's Wilkinson Microwave Anisotropy Probe places the value of the ratio at -1.1 ± 0.14 — which means the margin of error is great enough that the Big Rip may or may not happen.

But what if the ratio between dark energy pressure and energy density is exactly -1? In that case, the equation used to calculate the time until the Big Rip collapses. The denominator of the equation becomes zero, and the Big Rip doesn't occur. Probably.

After the Big Rip
What happens after the Big Rip? Nobody knows for sure. Matter is present, but it's dispersed, as atoms are ripped apart in the final milliseconds before the rip. If acceleration continues, infinitesimal, formless bits of matter could continue to disseminate on an atomic level, with no hope of ever being put back together. Or dark energy and phantom energy could surprise us and behave differently than people predict, and the Big Rip might not happen, or might look very different than we expect.

The Big Rip Theory says the universe could end in tearsS

Oh wait, Earth won't exist
The expansion of our Sun about 7 billion years from now will likely engulf the planet, and lead to its destruction. Hopefully, humanity (or our genetic/cyborg/trans-human offspring) will be a multi-planet species by then, ensuring our survival. Otherwise, we'll be long gone by the time anybody has to worry about the Big Rip.

If the ratio between dark energy pressure and energy density turns out to be extremely lopsided — let's say the ratio is -15 — the Big Rip will happen in just 800 million years. That's quite a long time from now, but it could easily be within the timetable of human events. Planet Earth would still be safe from destruction by the sun, and could be populated by our descendants, whatever form they take. If the Big Rip happens that soon, nothing will be able to prevent it — no matter how clever our post-human offspring have become. Let's hope they've learned to jump universes.

Image of Earth from the vantage point of the moon is courtesy of the NASA Apollo Archive, the timeline of the universe is courtesy of NASA, while the image of the Sun is courtesy of NASA/SDO. Sources linked within the article.