# Can an object above absolute zero temperature exists in principle, if there is only one object in the whole universe and nothing else

It is said that:

All matter with a temperature greater than absolute zero emits thermal radiation.

For suppose, there is only object in the whole universe and it emits radiations above absolute zero temperature. Does this case even possible? Isn't the temperature came into existence only after the particles gets separated from each other?

• The definition of temperature is $1/T = \partial S / \partial E$, which probably should still work. Radiation is just a side effect. Of course if your "one object" is so simple there is no entropy (e.g.it's a single particle) then $T$ is not well defined, but in such a simple system, doing stat mech is pointless anyway. – knzhou Jan 6 '16 at 20:29
• @knzhou My question is how can an universe with single object can gain a property of absolute zero. What is the trigger for it? – GP92 Jan 6 '16 at 20:32
• For a notion of temperature, you need a notion of thermal equilibrium first. This is not possible if there is only a single object, as far as I can tell. – Danu Jan 6 '16 at 20:57
• if the objext were above absolute zero, it would emit thermal radiation so there would be a bunch of photons too. – Peter R Jan 6 '16 at 21:28