Absolute zero is the lowest possible temperature in the universe. So if there’s a lowest temperature, does that mean there’s a highest? What would happen if we reached it?

Does a maximum possible temperature exist? (THREAD)

You may think that the maximum temperature should be the opposite of absolute zero, but it isn’t that simple. Remember, absolute zero is the temperature at which all atoms would stop moving: so what would the opposite even be?

According to thermodynamics (the study of heat & energy), there is a max temperature! It’s called “absolute hot” and is 142 nonillion Kelvins! That’s 142 followed by 30 zeros.

This is so hot that if you go above this temperature, the laws of physics just... stop working.

Have we ever reached this temperature? The answer is debated, but there’s one thing we know: the closest we’ve ever been was right after the Big Bang.

Less than a second after the Big Bang, all the particles in the universe were interacting in a relatively small space - this generated an unbelievable amount of heat. It’s debated whether we reached absolute hot, but it’s definitely the closest we’ve ever gotten!

Regardless, we weren’t at this temperature for long. As the universe continues to expand, heat spreads out and we cool down.

But what would happen if we reached absolute hot again?

At absolute hot, we would all die. But also, the energies of individual particles would become so large that the gravitational forces between them would become as strong as their electromagnetic and nuclear forces.

It’s believed that if this happened, all of these fundamental forces could be unified. It’s called the “theory of everything” and is one of the most tantalizing theories in physics. And we have plenty of time to figure it out because we likely won’t reach absolute hot ever again.

Reaching this max temp is essentially impossible. Basically, heat in our universe is always trying to even out, so the only way to reach absolute hot is if EVERYTHING in the universe does and we have little reason to believe that is gonna happen any time soon.

A huge shout out goes to @rahulsundeep for asking the question that inspired this thread! If you have any questions, tweet us @AnswerInTweets! It could become a future thread!