I was trying to explain this to my sister – or at least, the concept that everything is finite (we have *very* strange conversations), but I cannot explain it to save my life. What’s a good way of explaining entropy and the basics of thermodynamics to a layperson?
In: Physics
Start with its a theory, but probably true. If you throw a rock at a plane of glass… its a lot easier to break the glass than to put it back together. If heat was the equivalent of glass in this case, it is much easier to distribute the heat than to put it back together.
As time moves forward, heat tends to go from where it is concentrated to where it is not.
As processes happen, some amount of the energy in the system becomes heat.
Give it long enough and all processes will have happened and all heat will exist. Give it even longer and all heat will have mixed throughout the cosmos such that there are no areas where it is concentrated and areas where it is not
Everything tries to move into an equal state. Eventually all of the energy will disperse into the universe. Stars will die, turn into whatever they’re next stage is. Eventually those will also fully die and have nothing left. Blackholes will eventually disappear.
Everything will be so spread out evenly through the universe there will be no way to make energy anymore and thus the universe will be dead.
Imagine a bathtub. You fill it with hot water, it slowly cools down as heat radiates into the environment where it’s not as hot. The water becomes cold, then if left long enough the water evaporates into gas, given enough time that gas loses it’s internal heat on the atomic level, the energy holding individual bonds of H2O gas “cool off” and molecules break apart, then individual hydrogen atoms do the same thing, electrons lose their own “heat” and slowly stop moving. Basically this happens to all things in the universe on an insanely long timescale. There’s tons of simplification here, but it’s sort of an abstract way of how it works.
Imagine an empty lighter. You flick it and the flint makes contact with the spark wheel and you see a little tiny “explosion” or sparks if you will. Probably lasts a second and then nothing.
All of the energy from the friction is spent in that second.
If you were to record that event close up on a super slow motion camera you could stretch out that event to minutes, hours, days, etc and you could watch all of the flint particles heat up, explode, fly out, and eventually dissipate to nothing.
That’s basically the universe on a really really really really really really long timeline.
If we were able to get a recording of that, we would just fast forward it x whatever number to equate a second and it will look something like that lighter being flicked.
Energy can never be passed from an object or place with less energy to one with more energy, even as water never flows uphill.
Eventually the places with more energy will have given sufficient energy to the places with less energy that all places have the same quantity. At this point no further transfers of energy can occur.
Imagine a universe where there are only two objects. One is really hot and the other is really cold. The hot object will gradually cool down while the cool object will gradually absorb the heat from the hot one. When the two objects are the same temperature, it’s no longer possible for any heat to pass from one to the other. That moment represents the heat death of the system.
The universe we live in has a lot more than two objects, and some of them have ways to generate more heat for everything else to absorb. Because of that, it will take a long time to achieve true heat death, on the order of quintillions of years. But current models suggest that it will eventually happen.
In order for something to be hot, something around it has to be colder than it. Otherwise it’s not a hot thing, it’s just a room-temperature thing.
Eventually there will likely be a time when everything has reached the same temperature. Nothing will be hotter than anything else anymore, ergo nothing will ever be “hot” ever again.
Heat death is not the death of all things via heat. Heat death is the *death of heat itself*.
You need a temperature difference to get any work out of it. We can generate electricity heat when we burn stuff because it is warmer than the colder environment around it.
Heat water to 150C and you can get steam you can use because room temperature is around 20C. But room temperature is if you measure in absolute temperature around 300K (kelvin) and 150C water is 423K. We cant use the 300K water to get any useful energy unless we have something a lot colder.
The heat death is when every part of the universe has reached the same temperature. If you just leave to object att a different temperature in contact the warmer will transfer energy to the cooler and the temperature of both will end somewhere in between the starting temperatures. This will happen to all of the universe in the future.
I would ignore entropy completely.
I would say that you can only burn gasoline once. Only heat generation is 100% efficient, if you use it to run a car or something else there is always losses mainly as heat.
You could make gasoline again from the combustion process. At best it requires the same energy as you get out from burning it. But because not process is 100% efficient you spend more energy the you get out.
This also applies to everything else like nuclear fusion in stars
The observable universe is finite in size and amount of matter. So any process we have to get any useful energy out is limited by the amount of matter in the universe and it is limtied.
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