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Past a Certain Critical Temperature, the Universe Will Be Destroyed
StartsWithABang writes: If you take all the kinetic motion out of a system, and have all the particles that make it up perfectly at rest, somehow even overcoming intrinsic quantum effects, you'd reach absolute zero, the theoretically lowest temperature of all. But what about the other direction? Is there a limit to how hot something can theoretically get? You might think not, that while things like molecules, atoms, protons and even matter will break down at high enough temperatures, you can always push your system hotter and hotter. But it turns out that the Universe limits what's actually possible, as any physical system will self-destruct beyond a certain point.
Isaac Asimov posted a column in 1957 asking the same question. The column was subsequently published in a book of his collected scientific columns. A graduate student took the question posed by the column and used it for his doctorate thesis over fifty years ago.
This guy has anawful lot of confidence in how the universe works, I'll give him that much. I am only a lowly being compared to him, but isn't this all speculation? I'm pretty sure this is not a science with any kind of proof or even basic consistent knowledge, but don't let me get in the way.
You are correct, it's mostly a bunch of pop-sci woo-woo. For example, a massless particle no matter how energetic cannot on it's own convert into a black hole as he claims, because no matter how much energy it has you can always Lorentz boost into a frame where it has arbitrarily small amounts of energy. Likewise the photons in your room have arbitrarily large amounts of energy, depending on the reference frame you choose. But they have no mass, and a system requires a certain amount of mass to convert into a black hole (and the mass of system is invariant, i.e. it's the same in every reference frame).
The "the Universe would be destroyed" bit is also completely and purely theoretical at this point: we have no real proof for inflation at all. Our physics just doesn't really extend to those energy scales yet.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
It's an Ask Ethan page. Not exactly an Explain-like-I'm-Five but plenty of pop-sci woo-woo to keep it entertaining. And that awful page layout used by every Physics web blog since 2014.
"Mass"-less black-holes are perfectly possible. They are called Kugelbitz and are composed purely of "energy." Their existence in the models gives rise to the Plank Temperature, a point at which one cannot raise the temperature of anything before it becomes a slowly cooling black hole.
The original work on singularities to refute Einstein's space-time model (and by extension the black holes around them) do not talk of a difference between energy as mass and energy as momentum. The Lortenz equations mentioned only care about relative speed to that of light as measured in time (traveling) or space (geometry.) Once you are mass-less, thus moving at light-speed, there are no Lorentz effects to consider anymore. You've either divided by zero or just have the same properties as light. Then your temperature is just your frequency by definition.
Normally, temperature for atomic, particle and molecular systems is defined as the relative motion of matter to a rest frame. Since rest frames don't really exist, the only frame with arbitrarily small amounts of energy is one in which your reference frame loses contact with the frame under consideration, in other words another 'black' hole. Inside a "boosted" frame time and thus temperature continue to rise in Ethan's magical box. Once all the temperature is high enough that matter breaks down into photons or other mass-less particles that only have momentum as measured by the frequency. Which, per the Kugelblitz results, can certainly create a black hole. This light inside the boosted frame would just appear to you really dim and cool to your reference frame but would in fact be quite warm. The Cosmic Microwave Background (CMB) is a perfect example. The CMB looks cool today but comes from a time where the Universe was ridiculously small and thus dense. Expansion of space stretched it out (the geometry part) and made is lower frequency (the cooling part).
Like Evolution, we have evidence for inflation - it is consistent with actual observation of the world around us. Namely everything flying away (redshift) and that CMB. Unlike evolution we don't get to watch it happen directly on human time scale.
Sadly our current physics doesn't seem to extend even into our current energy scales. Consider dark energy. Most the energy of the current Universe is claimed to be the invisible stuff to explain the dimming of Type 1a Supernova observations. Mystery power pushing everything away.
There are theories that inflation is the natural physical behavior of whatever space-time is and our current period of slow expansion is a fluke cause by something else. (There are plenty of graphs with knees in them where everything interesting to us happens.) Talking about the birth and death of the Universe is a fun ride, but sometimes Cosmology is a real bummer.