- #141
chroot
Staff Emeritus
Science Advisor
Gold Member
- 10,296
- 41
The energy for a closed system never changes.
When you pull two magnets apart, you have to expend energy. The two magnets now have potential energy. When you release them, they exchange this potential energy for kinetic energy. When they smack together, they release that energy in heat and sound. You could also build a machine to harness the energy released by their release and turn it into any kind of energy you'd like -- electricity, and so on.
What you're probably asking is this:
If I come across two magnetic objects on the ground that are separated by some distance and have never been touched by anyone, they have potential energy. Where did this potential energy come from? The answer is that it came from the collapse of the solar system, because the magnets formed from that coalescing matter. Then you can ask how did the matter that coalesced into those two magnets begin so far apart to begin with, since that implies a quantity of potential energy? The answer to that one is that the universe's total energy content is fixed and non-zero. The universe just began with a specific quantity of total energy, and that energy is still driving everything from stars to coalescing planetary systems.
Of course, you can take the ultimate step and ask where did the Universe get its initial energy? and step off the map. We honestly don't know, and perhaps will never know. Certainly, science does not have a satisfactory answer to this question yet, and there are many indications it is not a question that can be answered absolutely.
- Warren
When you pull two magnets apart, you have to expend energy. The two magnets now have potential energy. When you release them, they exchange this potential energy for kinetic energy. When they smack together, they release that energy in heat and sound. You could also build a machine to harness the energy released by their release and turn it into any kind of energy you'd like -- electricity, and so on.
What you're probably asking is this:
If I come across two magnetic objects on the ground that are separated by some distance and have never been touched by anyone, they have potential energy. Where did this potential energy come from? The answer is that it came from the collapse of the solar system, because the magnets formed from that coalescing matter. Then you can ask how did the matter that coalesced into those two magnets begin so far apart to begin with, since that implies a quantity of potential energy? The answer to that one is that the universe's total energy content is fixed and non-zero. The universe just began with a specific quantity of total energy, and that energy is still driving everything from stars to coalescing planetary systems.
Of course, you can take the ultimate step and ask where did the Universe get its initial energy? and step off the map. We honestly don't know, and perhaps will never know. Certainly, science does not have a satisfactory answer to this question yet, and there are many indications it is not a question that can be answered absolutely.
- Warren