What is entropy? Also, can anyone explain how it relates to matter, gravity, time, other physics terms?
In: Physics
Top comment is written by Johnathan Astrophysicist or something so here’s the real ELI5
So you have a bottle of soda, but it’s room temperature. So you pour it in a glass and add some ice cubes.
The iced soda is like our universe if it’s in a closed system. Well, a closed system would be more like a vacuum flask, but stay with me. It’s like the universe because there are parts with more energy, like the warm soda, and parts with less energy, like the ice. In the universe, this could be like the Sun and Pluto instead.
So ice melts, yeah? This is because the energy in the soda that’s keeping it at room temperature is blasting the ice. Energy always wants to move to places with low energy. That’s why an open window renders your heating useless. It’s all going out the window into the low energy outside. Again, this is like our universe. You give off body heat, which is energy escaping your body to reach the low energy air around you. The Sun does the same thing into space basically, as does basically everything.
So what happens when the ice is all the way melted? The soda is still probably a little cold, but there’s a bunch of water in it and it sucks. That’s because the soda energy energized the ice, which turns it into water. That’s kind of like the heat death of the universe. Once everything that has energy disperses it across the universe equally, the universe will be too cold for life as we know it to exist and the rest of eternity will be inhabited by a bunch of corpses. Grim stuff.
E: Also important is that entropy is all about energy in a closed system. In the cup analogy energy from the room will still heat the shitty soda to room temp so it’s not perfect.
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