hello, I am a high school student from Alabama, and I'm in a college level physics class. We have just finished fluids and thermodynamics, but my physics professor claimed something that has me a little irked. according to my physics professor and the laws of thermodynamics, nothing can reach absolute zero, so I asked him about the fact that the universe is expanding, and whether or not this would still apply to a universe with infinite volume. his response was that the universe is continuously heating up due to entropy. he claimed that the universe would get even hotter as the universe expanded. this seems... incorrect. everything I've ever learned has told me that the universe started as a singularity - infinitely hot, and infinitely dense. as the universe expanded, it got cooler and cooler until it reached the average 3 Kelvin it is today. as the universe expands forever, it should get colder and colder (called the Big Freeze), until proton decay, and all the end of all molecular motion, where eventually, the expansion would cause the Big Rip. am I incorrect? if so, could you explain to me how entropy would cause the the universe to get hotter, and how come my perception of the Big Bang is so off base. if I'm correct, could you answer my original question: will the universe eventually reach 0 Kelvin (absolute zero), even though it's a theoretical asymptote?