Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Absolute Hot

en.wikipedia.org

Post reply on HN
Print view View original

61–70 of 78 posts

Re: Absolute Hot

#61

Post by Bjartr »

_4ziu wrote: post #49
Bjartr wrote: post #16

Earlier quoted context omitted.

If this were reddit I would've upvoted you, but this kind of cleverness should, if it constitutes the whole post, should be left to reddit. Now, should this thread ultimately hehehe a discussion on the virtues and approaches to creating mixtapes it would be another thing, but at this point in time I'm not seeing this as a positive contribution to discussion. That is why I downvoted your genuinely amusing comment.

tl;dr - no fun allowed.

Have your fun, just also contribute to the discussion in a meaningful way.

If you're looking exclusively for mindless fun, you're really in the wrong place. And there's nothing wrong with enjoying that kind of thing either, there are just better places to do it than HN.

Re: Absolute Hot

#62

Post by Bjartr »

probably_wrong wrote: post #20
Bjartr wrote: post #16

Earlier quoted context omitted.

If this were reddit I would've upvoted you, but this kind of cleverness should, if it constitutes the whole post, should be left to reddit. Now, should this thread ultimately hehehe a discussion on the virtues and approaches to creating mixtapes it would be another thing, but at this point in time I'm not seeing this as a positive contribution to discussion. That is why I downvoted your genuinely amusing comment.

Not that I disagree with you, but I should point out that it's a reference to the video "Absolute hot" of the YouTube channel "Casually explained".

Personally, I don't think that changes what constitutes a good discussion contribution on HN.

There's plenty of discussion here going into the details of the physics and the semantics at hand. We don't have to lower the bar for the discussion just because the topic under discussion was presented in a simple way.

Re: Absolute Hot

#64

Post by rmwaite »

Phrodo_00 wrote: post #56
sp332 wrote: post #12

Earlier quoted context omitted.

You can't accelerate anything to the speed of light without an infinite amount of energy. It just takes more and more energy to get closer to that speed. https://en.wikipedia.org/wiki/Speed_of_light#/media/File:Lor...

> You can't accelerate anything to the speed of light You can't accelerate anything _with mass_ to the speed of light. Although I guess that stuff with no mass already travels at the speed of light, so you wouldn't need to accelerate it.

Precisely. Photons always move at c.

Re: Absolute Hot

#65

Post by mmirate »

krylon wrote: post #19
antsar wrote: post #7

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Simple_English_Wikipedia It is an intentionally simplified version of English. Although, in this case, the meaning of the article seems to have been affected by the simplification. The English version makes it clear that this is a theoretical concept, whereas the Simple English version makes it sound like something concrete/absolute.

Ironically, I found the Simple English articles I tried to read harder to understand than the regular ones. Interesting concept, though.

Ironic but inevitable; the simplification appears to mostly be a matter of vocabulary. Reducing the vocabulary usually eliminates most technical jargon, and when the subject-matter is technical, the result is, well, a mess.

Re: Absolute Hot

#66

Post by badosu »

mirimir wrote: post #52
badosu wrote: post #33

Earlier quoted context omitted.

No hadron can achieve the speed of light. See: Ek=mc^2/√(1−(v/c)^2)−mc^2 For v As v->c it does not matter as much, the lorentz factor is much more significant, the mass operates just as a base multiplier and sum factor. As v->c, x->0 where Ek~1/x, i.e. tending to infinity with a division by zero when v=c. In conclusion, the speed is the relevant factor instead of mass when near speed of light, regardless of the objec…

Another perspective is that the object's effective mass is going exponential as v->c. I mean, that's why we say "rest mass", right?

Since E=mc^2 -> m=E/c^2.

For a moving object you could then m=(Er+Ek)/c^2, which creates the impression that the mass is variable (as the term Ek is zero when at rest and increasing with velocity), giving rise to the terms 'rest mass' and 'relativistic mass' respectively for the rest energy and total energy equations.

This interpretation is somewhat outdated but the terminology rest mass maintains its legacy. One could refer to it as the `(proper |invariant |intrinsic )?mass` instead.

The variable mass issue is then 'solved' by 'refactoring' the equation to use momentum where mass is coupled with velocity, over which the complexity of the lorentz factor is engulfed.

Re: Absolute Hot

#68

Post by wnoise »

shaded-enmity wrote: post #37

Hmm, at school we were taught that the maximum temperature is such that wavelength of the emitted black-body radiation would equal Planck length, is this rationale no longer sound?

It was never sound.

Black-body radiation describes the distribution of power emitted at given wavelengths or frequencies emitted by an ideal black body.

1. Distributions don't have one wavelength. There is a "peak" wavelength at which most power-per-wavelength is emitted, but there is still power emitted at all wavelengths no matter what temperature something is.

2. There is not sufficient reason to believe that the Planck length is a limit on the wavelength of light. This would break Lorentz symmetry.

3. Most things aren't ideal black bodies, but still have temperatures. Even if very hot objects couldn't emit light of Planck length, they can still couple to the environment and emit heat in other ways.

Re: Absolute Hot

#69

Post by snowwrestler »

wnoise wrote: post #59

Unfortunately, this a terrible name, concept, and even article. The vast majority of it is directly from a pop-science NOVA episode and not actually well-backed. There are reasonable bounds you can place on energy density where we expect current physical theories to stop making sense. But energy density is not the same as temperature. It is true that for things like ideal gases, temperature is roughly "energy per deg…

If the temperature wraps around to negative, doesn't that imply a maximum value at the wrap point? Do we know the temperature value at which it wraps to negative? Is it literally "infinity Kelvin?"

Re: Absolute Hot

#70

Post by wnoise »

snowwrestler wrote: post #69
wnoise wrote: post #59

Unfortunately, this a terrible name, concept, and even article. The vast majority of it is directly from a pop-science NOVA episode and not actually well-backed. There are reasonable bounds you can place on energy density where we expect current physical theories to stop making sense. But energy density is not the same as temperature. It is true that for things like ideal gases, temperature is roughly "energy per deg…

If the temperature wraps around to negative, doesn't that imply a maximum value at the wrap point? Do we know the temperature value at which it wraps to negative? Is it literally "infinity Kelvin?"

Yes, the wrap point is literally infinity, wrapping to negative infinity.

https://en.wikipedia.org/wiki/Negative_temperature is not terrible, for an overview, though the disclaimer is just annoying at this level.

For thinking about this point, it's much easier to talk about "thermodynamic beta" (sometimes called "coolness" or "coldness") which is just 1/T = partial S/partial E. The behavior of a spin system that admits negative temperatures can be described smoothly in terms of beta -- hotter systems have beta that is lower, and zero is not particularly special.

Now, any real system is coupled to the rest of the environment, so can't be in equilibrium at a negative temperature, as it would continuously leak heat until it cooled down enough to have some positive temperature. But if its internal equilibration proceeds much faster, then it's still useful to talk about its temperature as a quasi-equilibrium case.

Post reply on HN