It’s time we talked about entropy.
Imagine the motion in our universe: swirling galaxies, blazing suns, roaming comets, the clouds above our heads, and the blood in our veins. Everything moves. The universe is constantly changing — matter and energy constantly shifting into a different arrangement with every passing moment. We denote these different states of the universe by stamping them with a date and time.
We call it measuring time, but in reality we’re just labeling the different arrangements of the universe. Like looking at yearbook photos throughout your life, each labeled by the year on the cover. Each year, you grow and change. We could describe when the photo was taken by charting the exact arrangement of every atom and quanta of energy in the universe at that moment, or we could just give it a number.
“You took that photo in universe #1994. Not 95 or 93, but universe number one-nine-nine-four.”
Instead of saying when the photo was taken by describing the exact arrangement of every atom in the universe, we decide to give it a number called “time.”
If you take all the atoms right now in the universe, and re-arrange them into that same arrangement as in 1994, then you could re-live that moment perfectly.
But until we learn to completely control matter and energy as easily as breathing, things will continue to move and tear themselves apart.
Dark matter rends apart galaxies, suns explode, comets erupt, clouds disperse, and we eventually return to ash and dust and blow away.
And at the same time, space is expanding.
That’s what space – like outer space – does; it expands. Space expands, but the amount of matter stays finite. Eventually, there won’t be enough matter to fill this ever-expanding universe.
Imagine a far future, where all the atoms have finally dissolved into individual little particles roaming a vast and empty universe, never even seeing each other, because space has expanded and stretched so far. They would never interact enough to form basic molecules, let alone suns and planets.
When space expands in our universe, it’s like a house that keeps adding on a room every year forever. You were given a box of chocolates, and told you had to keep at least some chocolate in each room. But you were never given any more chocolates. So you have to start chopping them up. Pretty soon, you’re getting to the microscopic level, leaving little molecules of chocolate in the newest rooms, just to have something in each room. Eventually, you have to tear apart the molecules into atoms, and the atoms into quarks to spread into the new rooms. Then into little strings of energy, the tiniest concept of matter that humans have ever perceived.
At that point, when the universe has expanded so much and matter has spread so thin, the universe will have become essentially inert, changeless, uniform in all directions. An “ultimate state of inert uniformity,” as Merriam-Webster likes to call it. Motionless. No need to measure time anymore, because one state of the universe is exactly the same as any other state at this point. From that point on, the past is the same as the future.
1994 Yearbook Photo