# B Absolute zero by definition is "nothing"

1. Jun 1, 2017

### GregoryC

Is absolute zero nothing? Can a quanta exist in nothing? There could be no quantum fluctuations at absolute zero.

2. Jun 1, 2017

### rumborak

Absolute zero is just the bottom end of our temperature scale. There is no direct relation of that to the presence, or absence, of anything. You could argue that the only way of achieving absolute zero is by removing everything (including space), but that's a rather moot consideration and probably not what you mean.

3. Jun 1, 2017

### GregoryC

Yes, that is exactly what I am talking about. It is theoretical as is infinity.

4. Jun 2, 2017

### Khashishi

Absolute zero is a temperature, not nothing. You can have matter at temperatures arbitrarily close to absolute zero. It doesn't become nothing. Absolute zero is a mathematical limit which cannot be reached, only approached. You still have some zero point energy at zero temperature, so it's not correct to say the quantum fluctuations go away.

5. Jun 4, 2017

### Jamison Lahman

Is anything nothing? Never.

6. Jun 4, 2017

### Staff: Mentor

Consider a lone atom with its electrons in their ground states. This is essentially what you're talking about. The atom doesn't somehow disappear just because it is in its lowest energy configuration. The only difference between a lone atom and macroscopic object is that the extra energy is partitioned into an enormous number of states and cannot be gotten rid of entirely.

7. Jun 5, 2017

### Khashishi

Temperature only really makes sense for macroscopic systems. A lone atom has an energy, but not a temperature. That's because temperature is defined as a derivative:
$$\frac{1}{T} = \frac{\mathrm{d}S}{\mathrm{d}E}$$
The derivative doesn't really make sense on a microscopic scale because states are quantized. On a macroscopic scale, we smooth over the states, and treat the system as having a "density of states", such that the number of states varies smoothly with energy. Absolute zero is not possible to reach because you can't reasonably treat the system as continuous for very small changes in energy, and the mathematics are invalid.