Asked by Moe Webster
It’s one theory on how the universe will end: the ‘Heat Death’ – also known as the ‘Big Freeze’ or the ‘Big Chill’ – has been suggested as one of the ways in which the cosmos could come to an end, especially since it’s ever expanding.
The idea of heat death actually originates from the second law of thermodynamics – that’s that idea that entropy increases in an isolated system (this system being the universe). Entropy, which is the number of ways in which a system can be arranged should never decrease, evolving to a state of maximum disorder (or thermodynamic equilibrium). When this happens, all energy will be evenly distributed throughout the cosmos, leaving no room for any reusable energy or heat to burst into existence. Processes that consume energy, which includes our very living on Earth, would cease.
You might think that Heat Death implies some astronomically high temperature that snubs everything out. However British physicist Lord Kelvin, who proposed the idea in the 1850s, referred to the loss of mechanical energy as the theory of heat. In fact, it has been suggest that the more the Universe expands, the cooler it gets.