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PBS Space Time
Season 2026 • Episode 4 • The Universe Is Racing Apart. We May Finally Know Why.
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PBS Space Time Season 2026, Episode 4: The Universe Is Racing Apart. We May Finally Know Why.
We've known that the universe is expanding since 1929, and that its expansion is accelerating since 1998. The culprit behind the acceleration is unknown, so we live with a stand-in term "dark energy". Our modern cosmological model assumes that dark energy has a constant density--always the same amount of the outward-shoving stuff per volume. But there's recent evidence to the contrary--which may be why our primary efforts to measure the expansion rate of the universe disagree with each other. Watch PBS Space Time Season 2026, Episode 4 The Universe Is Racing Apart. We May Finally Know Why. in HD free online. Enjoy high-quality streaming of PBS Space Time Season 2026, Episode 4 and share your thoughts in the comments below!
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Episodes
6 episodes
The Universe Itself Might Be Hiding the Gravity Particle From Us
To progress to the next level in understanding reality, we need to combine quantum mechanics and Einstein’s general relativity. And to do that, most physicists believe we need a theory of quantum gravity .. which means we need gravitons. But it also seems like the laws of physics make it impossible to ever detect this quantum particle of gravity. Almost like the universe is set up to keep the final answer forever out of our reach. So, can we outsmart the universe, catch a graviton, and finally solve physics?
20 min
This Particle Solved Everything. We Just Found Out It Isn't Real
The universe thrums with quantum fields; and the particles of matter and force emerge as vibrational manifestations of the deep symmetries of these fields. The layers and reflections of those symmetries give us the wonderful richness of what we call the standard model of particle physics. Except there seems to be something missing: the sterile neutrino.
20 min
The Universe Tried to Hide the Gravity Particle. Physicists Found a Loophole.
Physicists have long believed that detecting the particle of gravity—the graviton—was fundamentally impossible, with the universe itself seeming to block every direct attempt. This episode explores a new generation of clever experiments that may finally let us detect gravity’s particle, and why even succeeding wouldn’t quite mean what we think it does.
19 min
The Universe Is Racing Apart. We May Finally Know Why.
We've known that the universe is expanding since 1929, and that its expansion is accelerating since 1998. The culprit behind the acceleration is unknown, so we live with a stand-in term "dark energy". Our modern cosmological model assumes that dark energy has a constant density--always the same amount of the outward-shoving stuff per volume. But there's recent evidence to the contrary--which may be why our primary efforts to measure the expansion rate of the universe disagree with each other.
21 min
Most of Reality Is Invisible. We May Finally Be About to Reveal It.
Some people worried that the large hadron collider would smash particles together so hard it would make black holes that would swallow the earth, open wormholes to other dimensions. It didn’t and won’t. But it may be making a different kind of portal. A portal to the dark sector. This isn’t the Rather, it’s a hypothetical family of elementary particles that exists in parallel to the familiar particles of the standard model, but are invisible to it. Invisible to us, and so could be the answer to the dark matter conundrum. And what is this portal? It’s the particle that the LHC was built to find in the first place - the Higgs boson.
20 min
Something Disturbing Happens When You Solve Einstein's Equations This Way
Kurt Gödel discovered a solution to General Relativity that allows time travel without any exotic physics, revealing that the theory doesn’t actually guarantee a consistent chain of cause and effect . His “Gödel universe” shows that under certain conditions, the structure of spacetime itself can loop back on itself—blurring the line between past and future and exposing a deep limitation in our understanding of reality.
16 min