# What's the opposite of Absolute Zero? **URL:** \ **Category:** Factual Questions\ **Created:** [February 16, 2010, 5:57am UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176 "2010-02-16T05:57:01Z")\ **Posts on this page:** 18\ **Page:** 2
**Author:** ![Claude\_Remains](https://avatars.discourse-cdn.com/v4/letter/c/898d66/32.png) [@Claude\_Remains](https://boards.straightdope.com/u/Claude_Remains)\ **Post date:** [February 18, 2010, 8:48am UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/21 "2010-02-18T08:48:01Z")
> [@Zorlon](#): > > Imagine all the energy in creation concentrated into one tiny point. Imagine how hot that would be. That would be the hottest attainable temperature, but not the hottest possible… if there existed one iota more energy it too could be thrown on the pile. > > Absolute zero is the lowest temperature because it is the absence of all heat. Just like zero inches is the absence of all length. It doesn’t get any shorter. > > However, something could always be longer if you had a way to make it so. So too, something could always be hotter, as long as you had a way to make it hotter. Infinity + 1 :rolleyes: ---
**Author:** ![Claude\_Remains](https://avatars.discourse-cdn.com/v4/letter/c/898d66/32.png) [@Claude\_Remains](https://boards.straightdope.com/u/Claude_Remains)\ **Post date:** [February 18, 2010, 9:03am UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/22 "2010-02-18T09:03:00Z")
> [@Chronos](#): > > That’s only an issue if you have multiple particles traveling in different directions. A single particle in otherwise empty space will never turn into a black hole. What could make the number of particles exiting a black holes event horizon equal to the number of virtual particles entering it? ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [February 18, 2010, 1:13pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/23 "2010-02-18T13:13:40Z")
> [@Chronos](#): > > That’s only an issue if you have multiple particles traveling in different directions. A single particle in otherwise empty space will never turn into a black hole. Is that even possible in theory? “Empty” space is full of virtual particles, after all. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 18, 2010, 6:37pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/24 "2010-02-18T18:37:19Z")
> [@](#): > > Is that even possible in theory? “Empty” space is full of virtual particles, after all. Yes, but the distribution of virtual particles is such that they don’t specify a reference frame. So being “at rest” in a sea of virtual particles is the same as “zooming through” the same sea: You’ll interact with them in the same way in either case. They _do_ actually make a difference if you’re accelerating, but that’s a different topic. ---
**Author:** ![Incubus](https://avatars.discourse-cdn.com/v4/letter/i/c68b51/32.png) [@Incubus](https://boards.straightdope.com/u/Incubus)\ **Post date:** [February 18, 2010, 8:36pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/25 "2010-02-18T20:36:56Z")
Opposite of absolute zero? Why, molten cheese, particularly fondue, applied generously to one’s soft palate :eek: ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [February 18, 2010, 9:28pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/26 "2010-02-18T21:28:06Z")
**Pleonast** said: > [@](#): > > This will be hard to grok, but the maximum temperature is enumerated 0K (absolute zero). Just as one can cool a system to arbitrarily close to absolute zero, but never reach it, one can heat a system to arbitrarily close to absolute zero, but never reach it. That is, in certain systems, we can heat it -10K, add more heat, raising the temperature to -1K, then add more to get to -0.1K, etc, but will never be able to add enough heat to reach 0K. And despite the enumeration as a negative number, it is hot, not cold. Read the link, find the system completely preposterous. First off, positive and negative zero? At the ends of the scales? Second, infinity in the middle, and the transition runs from positive infinity to negative infinity as energy is applied? If there were anything more designed to sound preposterous and create confusion, I find it hard to fathom - and that includes quantum issues like wave-particle duality. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 19, 2010, 4:14pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/27 "2010-02-19T16:14:51Z")
**Irishman** , yep, it’s hard to understand. Unfortunately that math is the simplest way we have to describe those systems. Personally, I think about it terms of a [two’s complement](http://en.wikipedia.org/wiki/Two%27s_complement) representation, but that is probably more confusing to most people. Sometimes in science the hardest part is coming up with the math used to describe a phenomenon. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 19, 2010, 4:36pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/28 "2010-02-19T16:36:55Z")
> [@Chronos](#): > > The key is that it’s mass that determines whether something collapses into a black hole, and despite what you may have heard, mass does not change when you move at relativistic speed. > > Think of it this way: The central principle of relativity is that all reference frames are equally valid, right? Well, think about putting yourself in the reference frame of the fast-moving particle. In that frame, it’s not moving at all, so obviously its motion isn’t going to turn it into a black hole. And if you see that it’s not a black hole, so does everyone in every other reference frame, since whether something is a black hole is not the sort of thing two different observers can disagree about. Ok…this is confusing. E=MC[sup]2[/sup] Mass is interchangeable with energy. So, keep adding energy to a system and its mass perforce increases. I thought this was one of the sticking points of traveling at light speed. An object with mass would have infinite mass at light speed which is a problem. So how is it these energetic particles have no more mass than less energetic ones? ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 19, 2010, 5:36pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/29 "2010-02-19T17:36:19Z")
The [full equation](http://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation) is E[sup]2[/sup] = m[sup]2[/sup]c[sup]4[/sup] + p[sup]2[/sup]c[sup]2[/sup]. M is the rest mass, which is an invariant quantity–all observers will agree on what a particle’s rest mass is. P is momentum. In the case of zero momentum (that is, in the particle’s rest frame of reference), you get the famous equation E = mc[sup]2[/sup]. When a particle is moving, its rest mass\* does not change, but it’s energy E does. Note that a particle’s energy is not invariant–different observers will see a different momentum, and thus disagree about the energy. \*Physicists only use rest mass, or simply “mass”. The concept of “relativistic mass” (the “mass” that increases with a particle’s speed) is not a useful one. Confusion as we see here is a result of using it. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 19, 2010, 6:16pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/30 "2010-02-19T18:16:15Z")
> [@Pleonast](#): > > The concept of “relativistic mass” (the “mass” that increases with a particle’s speed) is not a useful one. Why? (genuinely curious…particularly when we are talking about energies where relativistic effects would seem to apply) Trying to read up on it some I found the bit below which seems to argue for using relativistic mass: > [@](#): > > A commonly heard argument against the use of relativistic mass runs as follows: “The equation E = mc2 says that a body’s relativistic mass is proportional to its total energy, so why should we use two terms for what is essentially the same quantity? We should just stay with energy, and use the word ‘mass’ to refer only to rest mass.” The first difficulty with this line of reasoning is that it is quite selective; after all, it should surely rule out the use of rest mass as well, since within special relativity, rest mass is proportional to a body’s rest energy. On that note, a second difficulty of the line of reasoning is more technical: equating energy and relativistic mass cannot be done more generally. In general relativity, it’s natural to consider quantities that are conserved for a system moving on a geodesic. However, γ m is not generally conserved along geodesics. (Actually, γ m is called pt in the language of general relativity. It turns out that a closely related quantity, pt, will be conserved along a geodesic if the metric is time independent.) Note, though, that while relativistic mass γ m is not a body’s total energy in general relativity, it’s also not simply the source of gravity within the same theory. Finally, a third difficulty with the above commonly heard argument is that, in the interests of consistency, it should surely be applied to rule out either the “momentum density” or the “energy flux density” of light, since these also are simply related by a factor of c2. Yet, and quite rightly, these last two terms co-exist in modern literature; no one ever suggests that either of these terms should be dropped in favour of the other, because they both have their uses and are fundamentally different quantities: a spatial density and an areal density. > > So likewise do the concepts of mass and energy have their uses. The above argument that E = mc2 demotes mass in favour of energy—or rather, that it selectively demotes relativistic mass, but not rest mass—also neglects the very definitions of mass and energy. Mass is a property of a body that we have an intuitive feel for; its definition as a resistance to acceleration is very fundamental. Energy, on the other hand, is defined in physics in a technical way that involves the concept of a system’s time evolution; this is not something that bears any obvious similarity to the concept of an object’s resistance to being accelerated. If the concept of mass exists in some sense “prior” to that of energy, and if energy itself is defined in a different way to mass, then it does not seem reasonable to drop the idea of mass in favour of energy. Rather, E = mc2 becomes an expression that tells us how much energy a given mass has; it also tells us how much a body will resist being accelerated depending on its energy content. And, perhaps best of all, it reminds us that Einstein’s equation is a triumph of relating two disparate quantities—and this is one of the great aims of physics. > > Another argument sometimes put forward for dropping the use of relativistic mass is that since e.g. all electrons have the same rest mass (whereas their relativistic masses depend on their speeds), then their rest mass is the only quantity able to be tabulated, and so we should discard the very idea of relativistic mass. However, when we say without qualification that “the height of the Eiffel Tower is 324 metres”, we clearly mean its rest length; but that doesn’t mean the idea of contracted length should be discarded. Similarly, it’s okay to say that the mass of an electron is about 10–30 kg without having to specify that we are referring to the rest mass; everyone knows we mean rest mass when we tabulate a particle’s mass. That’s purely a useful linguistic convention, and it does not imply that we have discarded the idea of relativistic mass, or that it should be discarded at all. > > SOURCE: [Relativistic Mass](http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html) ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 19, 2010, 8:10pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/31 "2010-02-19T20:10:19Z")
Interesting linked article. I encourage others to read it in full. I think the reason I prefer to use rest mass only, and not think in terms of relativistic mass, is that rest mass is a nice invariant property of a particle, like charge or spin. I put all the relativistic accounting into energy and momentum. It’s basically a choice about where to place the complications of relativity. It seems more natural to put the speed-variable variation in the quantities that vary the most with speed (including slow non-relativistic speeds). And as we’ve seen in this thread, relativistic mass engenders the misconception that a fast-moving object can collapse into a black hole due to it’s increased “mass”. Compare mass to length. While mass is a fundamental property of a particle, length is not. It is a macroscopic property of a system of particles, like temperature. Actually I have a similar complaint about relativistic length. It encourages some people to think that objects get compressed (as in forces squeezing the objects to make them flatter) when moving relativistically fast. They don’t; the foreshortening is a geometrical effect of spacetime. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [February 19, 2010, 8:16pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/32 "2010-02-19T20:16:03Z")
Not trying to be a pain…trying to understand so bear with me if you will: So, what happens if I take a kilo of anti-hydrogen and a kilo of hydrogen and bring them together (apart from a spectacular explosion)? I thought we go to E=MC[sup]2[/sup] again for the answer. We are taking the mass (2 kilos) and converting it all to energy. No more mass, lots and lots of energy. Are we converting the rest mass or relativistic mass using that equation? Where does the rest mass go if that equation only deals with relativistic mass? ---
**Author:** ![ShibbOleth](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@ShibbOleth](https://boards.straightdope.com/u/ShibbOleth)\ **Post date:** [February 19, 2010, 9:01pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/33 "2010-02-19T21:01:09Z")
Wouldn’t the opposite of absolute zero be “burning with the intensity of 1000 suns”? ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [February 19, 2010, 9:27pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/34 "2010-02-19T21:27:26Z")
The inside of my car at 3:00pm on any given day in July or August. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [February 19, 2010, 9:50pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/35 "2010-02-19T21:50:50Z")
What would you heat it with? ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 19, 2010, 9:54pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/36 "2010-02-19T21:54:23Z")
For matter-antimatter annihilation, the energy available is the combined total energies of the matter and antimatter. Most physicists would compute it using the equation I gave in Post 29. That uses the rest mass (invariant) and relativistic momentum (varies with speed). Instead, one could use E = mc[sup]2[/sup], where the mass is the relativistic mass. Of course, you need to know the rest mass and speed to compute that, so it’s no different than the other formulation in terms of information. And the result will be the same. In case it isn’t clear, the total energy of the matter and antimatter is converted. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 19, 2010, 10:13pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/37 "2010-02-19T22:13:45Z")
If you take a kilogram of matter and a kilogram of antimatter and bring them together (gently, so there’s no kinetic energy to worry about), then you’ll have a total of 2 kg of mass, both before and after the Earth-shattering kaboom. The key here is that the mass is a property of the whole system, not of the particles that compose it. A single photon has no mass, but a collection of photons (like what you’ll get out of that antimatter reaction) can have mass. It only looks like you’re losing mass if you look at the individual pieces of the system. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [February 19, 2010, 10:18pm UTC](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176/38 "2010-02-19T22:18:45Z")
> [@Chronos](#): > > If you take a kilogram of matter and a kilogram of antimatter and bring them together (gently, so there’s no kinetic energy to worry about), then you’ll have a total of 2 kg of mass, both before and after the Earth-shattering kaboom. The key here is that the mass is a property of the whole system, not of the particles that compose it. A single photon has no mass, but a collection of photons (like what you’ll get out of that antimatter reaction) can have mass. It only looks like you’re losing mass if you look at the individual pieces of the system. So if particles were speeding toward each other at the very very very (etc) high speeds Cecil mentions in his column about miniature black holes, when they get close to each other, an observer from outside should find that the total mass of the system exceeds the necessary mass to create a black hole out of the two particles. Is there a reason this should not happen (or would it happen)? [Previous page](https://boards.straightdope.com/t/whats-the-opposite-of-absolute-zero/529176.md?page=1)