I was reading some science thing... and was told that there was a discrepancy in the rate of expansion of the Universe... which was one of the biggest fucks which I COULDN'T GIVE....
BUT: The article then said that the discrepancy might be due to a new theory that claims the Universe is spinning!
Now THIS was something I've never heard before... so I cranked up my A.I. SAL-9000... and asked:
Sal, there is some discrepancy in the Hubble constant, but there seems to be a theory that the spin of the universe would account for that! Any thoughts?
Sal said:
Ah yes, the idea that universal rotation—a kind of cosmic "spin"—might explain the Hubble constant tension is one of those intriguing, fringe-y yet not entirely implausible theories that cosmologists sometimes dust off and examine under the right lighting.
Let’s break this down into digestible pieces:
🌀 The Hubble Constant Tension
The Hubble constant (H₀) measures how fast the universe is expanding. But there’s a nagging problem: two main ways of measuring it yield different values:
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Local measurements (e.g., using Cepheid variables and supernovae):
🔹 ~73–74 km/s/Mpc
(most notably from the SH0ES team) -
Cosmic Microwave Background (CMB) measurements, like from the Planck satellite:
🔹 ~67–68 km/s/Mpc
(based on extrapolating early-universe physics)
The discrepancy is well beyond experimental error, meaning something fishy—or revolutionary—might be going on.
🌌 Enter: A Rotating Universe?
Some theorists have proposed that if the universe had a global angular momentum, it could slightly distort the spacetime fabric, which in turn might impact how we interpret the redshift-distance relationship—and thus the Hubble constant itself.
What would a spinning universe imply?
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Frame-dragging effects (like those predicted by General Relativity around rotating bodies) could occur on a cosmic scale.
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Expansion might not be entirely isotropic—there could be slight anisotropies or directional dependencies.
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Observers in different parts of the universe might perceive different expansion rates, depending on their alignment with the "axis of spin."
🔬 Is there any evidence for this?
There are hints, though none are conclusive:
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Large-scale anisotropies in the CMB have occasionally been interpreted as signs of a preferred axis (the so-called "Axis of Evil").
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Some galaxy alignments over cosmic distances suggest there might be a correlation in spin direction, which shouldn’t happen if the universe is perfectly isotropic.
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General relativistic models like the Gödel universe allow for rotation—but they also permit closed timelike curves (i.e., time travel), which most physicists avoid like a temporal plague.
⚖️ Problems with a spinning universe
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Inflation theory (which smooths out the early universe) tends to erase any initial angular momentum.
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CMB data is incredibly smooth and isotropic overall. Any rotation would need to be extremely subtle.
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Introducing spin may not actually resolve the Hubble tension unless the effects are finely tuned—and doing so might break other observed symmetries.
🧠Theoretical Value
The concept is less about offering a slam-dunk solution and more about expanding our theoretical playground:
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If the universe has spin, it implies a preferred direction, breaking the cosmological principle (that the universe is homogeneous and isotropic).
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That would ripple through everything from cosmological modeling to philosophical implications about the nature of time and directionality in the universe.
🔚 Final Thoughts from SAL
So far, universal rotation is an elegant but speculative way to approach the Hubble tension—more of a cosmological jazz riff than a nailed-down theory. But it's valuable precisely because it challenges assumptions.
And remember: Every breakthrough in cosmology started as a wild idea someone dared to take seriously.
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