HECK, NO ONE TOOK THOSE LAWS SERIOUSLY TO BEGIN WITH:

In all the Universe, one of the most fundamental rules of all is the law of energy conservation. In its simplest form, it states that energy can neither be created nor destroyed, but only transformed from one type into another. Regardless of transformations between different types of energy, including:

gravitational potential energy,

chemical energy,

the energy of radiation,

thermal (heat) energy,

kinetic (motion) energy,

rest mass energy,

as well as any other form of energy you can dream up,

the total amounts of "initial" and "final" energy in any physical system must always add up to the same values.

But there's an underlying reason for why energy is always conserved: it's because there's a physical symmetry that corresponds to the conserved quantity of energy. In this case, it's time-translation invariance: the notion that physical properties and laws don't evolve with time. But there is a very important physical property -- not on Earth, but on cosmic scales -- that actually does evolve with time: the distance between any two cosmic objects that aren't gravitationally bound together. In the expanding Universe, distant galaxies recede from one another, growing farther apart with time.

Does that imply that energy is no longer conserved in an expanding Universe? Bizarrely, it actually does. As strange as it may seem, it's actually true: energy is not conserved in the expanding Universe.

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