The Big Bang and expansion of the universe.Image: Sidharth Nikam (JPL, NASA)
Some more eventful theorized fates could arrive sooner, like the Big Rip. You might be aware that in 1998, scientists discovered the universe wasn’t just expanding, but that the expansion rate was increasing. They theorize that some energy seemingly innate to the vacuum of the universe, called dark energy, powers the accelerated expansion. There’s a possibility that in over 100 billion years, the dark energy will cause the universe to expand so quickly that it tears apart galaxies, solar systems, planets, and atoms before they can run out of energy on their own. The space between every individual point would grow infinitely large. Physics theory seems stacked in favor of heat death over the Big Rip, but who knows—observations don’t forbid it.
Then, there’s the chance that the very vacuum of space itself could change. Maybe the “Higgs field,” a field the permeates the universe that determines the mass of subatomic particles, isn’t in the lowest energy configuriation. Maybe it is actually “metastable” and there’s a lower-energy ground state it could decay to. Imagine spending your whole life living on a platform, thinking it was the solid ground—this platform is the metastable state. Maybe one day, the platform will collapse and reveal a true floor a hundred feet below. The laws of physics as you know them would no longer work, and you would fall and die. This is essentially what would happen if the universe snapped from a metastable state to a more stable state, if we were living on the platform all along. This would end the universe as we know it, since this new, lower-energy universe would not support the existence of the present-day Standard Model that governs the identities and interactions of particles that make up matter. It’s unlikely such an event would occur before the heat death does. But it would be a spectacular death.
“At some spot in the universe you’d create a bubble of true vacuum that expands at the speed of light and envelopes the universe, destroying everything,” said Mack. Its light speed means you wouldn’t see it coming—the death would arrive simultaneously with the warning that death was coming.
But not every possible cosmic conclusion is one of utter desolation and emptiness. Maybe in some distant, post-heat-death future, the energy in the universe’s vacuum could spontaneously jump back upward at a point, initiating inflation at that point in space from which entirely new universes form, Alan Guth, MIT physicist who invented the theory of cosmic inflation, told Gizmodo. Perhaps that’s how our universe formed, and perhaps there are an infinite number of universes forming in the same way, decaying out of an infinitely inflating grander universe. Maybe there are places beyond the reach of our own universe that won’t be impacted by the demise of our own.
“This is the most optimistic point of view among theories, because even though our part of the universe will die out, other parts that may be teeming with life would go on forever,” Guth said. Our universe dies, either way.
“This is the most optimistic point of view among theories, because even though our part of the universe will die out, other parts that may be teeming with life would go on forever.”
And maybe dark energy isn’t an innate, constant value to the universe. Maybe, as we previously reported, its strength is decreasing, which might lead to the universe’s expansion eventually slowing. Everything could then turn around under gravity’s force and collapse—that’s the “Big Crunch.”
There’s a lot we don’t know about the universe, so any or none of these ideas could be right. Any new discovery about the nature of dark energy, the Higgs boson, or spacetime itself could reveal a vastly different fate of the universe, where everything wastes away to an infinitely vast nothingness, everything collapses, or new universes spawn from the ashes of the old, or something else entirely happens. Regardless, humanity’s existence and legacy—and everything else, ever—will cease to exist or have meaning.
“Even though we all know that we personally are going to die, it still kinda hurts that so is everything else,” said Mack. “There’s nothing that’s going to live on.”
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