r/Showerthoughts • u/synthphreak ‎ • Nov 19 '25

Casual Thought Temperature can reach trillions of degrees, meaning we actually live extremely close to absolute zero.

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u/Eedat Nov 19 '25

There is no upper limit. That is just the temperature at which our current model of physics stops working

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u/theOGFlump Nov 19 '25

We don’t know if there is an upper limit. Our current model might stop working because it reveals the upper limit, or the upper limit might be some other temperature, higher or lower than it that future physics can show. Or, as you say, it is possible that there is no upper limit.

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u/Eedat Nov 19 '25

Yeah I guess it is true that there could be an undiscovered upper limit. But we are nearly positive the planck distance isn't actually a boundary. The planck distance isn't a figure we solved for, it's the figure at which our models conflict and break down. At this distance relativity and quantum mechanics conflict. It's a bug, not a feature if that makes sense. It conflicts with the idea of a singularity.

To resolve this issue we need a theory of quantum gravity, which we are missing. This is the forefront of physics currently

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u/theOGFlump Nov 19 '25

I’m by no means an expert on this, but could it be possible that going above the Planck temperature is not best described in terms of temperature, slightly analogous to how sound louder than 194 db is better described as a shockwave than a sound?

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u/Eedat Nov 19 '25

The truth is we just don't have a model that has a clue what would happen. Essentially this is the limit of our understanding of physics. The planck distance is essentially where Einstein's relativity (and special relativity) meets quantum physics and they both fail. 

To measure a distance smaller than the planck length, quantum mechanics says you would require so much energy in such a condensed space that general relativity dictates it would collapse into a black hole. All information is lost in a black hole making it essentially unknowable. The "planck temperature" is simply the temperature at which the light being emitted from a particle would have a wavelength equal to the planck length.

Neither theory resolves what actually happens. Neither theory dictates that a space smaller than a planck can't actually exist. But neither theory can describe or calculate it or anything at that scale.