# At absolute zero and above zero [closed]

It is very well know that above zero Kelvin every body emits thermal radiation

2. And will our most precise instruments will not be able to detect the presence of any body/matter at absolute zero in absence of any external light source?

## closed as unclear what you're asking by CuriousOne, ACuriousMind♦, John Rennie, sammy gerbil, user259412Aug 1 '16 at 0:38

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• Thermal radiation is being emitted by a body in thermal equilibrium. If anything else comes out, then the body is not in equilibrium and talking about a temperature doesn't make sense. T=0 is simply ruled out by the third law of thermodynamics. – CuriousOne Jul 31 '16 at 4:42
• The first two statements of yours seems absurd and about the last I agree with it but what if it Is an ideal process i.e. no entropy change takes place – Rohit Joshi Jul 31 '16 at 4:48
• What sounds absurd to you? That there are bodies that don't have a temperature? You want an ideal process? How much time and money do you have? I am being paid by the hour and ideal processes take infinitely long, i.e. they are unphysical and expensive to observe. – CuriousOne Jul 31 '16 at 4:52
• Then why the hell we study ideal process if they physically not possible considered the exmaples of Carnot Engine ( internally reversible) Blackbodies( ideal) we do not construct these bodies but we are rather curious to know how they work, so whats the problem in having a body at absolute zero, – Rohit Joshi Jul 31 '16 at 4:58
• So you know what you can never achieve in reality, but mostly because the complete mathematical description of non-ideal processes is much, much harder. There is nothing wrong with having a body at absolute zero, except that nobody has ever seen one. Science is generally supposed to describe what has been observed and those things have not. – CuriousOne Jul 31 '16 at 5:10