@The-Con Not really a theory. At 0 degrees, the atom has no energy (as energy creates heat). Unless everything we know is wrong, you can not have a substance with negative energy. (please note, this is the quantity of energy, not the charge of energy)
On earth, we can not reach absolute 0 in a lab, but close to it.
we can reach 2.76 K only! because Big Bang radiation is 2.76K and if we'll make smth cooler this radiation will just heat this smth Ok lets dont discuss about non-PowderToy things here
You could think of negative as being endothermic, absorbing heat not producing it... but as heat is the average kinetic energy and at absolute zero KE=0, you cannot reduce KE any more (thank goodness for those engineering physics courses I took lol)