eli5 How is it that things on earth can be “hotter than the surface of the sun”? If the sun is giving energy to basically everything on earth, wouldn’t any earth-item or organism only be able to mimic a fraction of the sun’s energy/power output?
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>If the sun is giving energy to basically everything on earth,
Its not. That is just totally false and not how any of this works at all. It doesn’t even make sense.
Also, the sun specifically has a certain amount of heat and temperature due to the reactions in it and the type of star it is. We can do reactions that get much hotter. Our sun isn’t actually that hot when you start talking about things that are really really hot. Our sun isn’t even that hot for a sun, its about 6000 C, which is roughly in the lower-mid range of heat for stars. Some very hot stars are 2x-4x hotter, and those even on the hot range of things we can make hot, aren’t even that hot (but still really hot of course). Really hot stars may be like 20,000 degrees C. We can use science and get things to a 1,000,000,000+ degrees C
Temperature is the average speed of molecules jiggling around. Each molecule in an area needs a certain amount of energy to reach a high speed and meet or exceed the temperature of the sun. But if the area is small and there aren’t many molecules, the total amount of energy is small. You do need to concentrate the energy of the sun by somehow storing it then releasing it, but this can happen naturally with electrical charge (lightning) and artificially with both electricity and other means.
Yes, the Earth does get *most* of its heat and energy from the sun (though nuclear reactions can “create” energy – or to be precise, convert stored energy into heat – in a way that is not directly related to energy received from the sun). So it would not be realistic to heat the ENTIRE earth to be hotter than the sun, but concentrating that energy into a small spot is another question.
The amount of energy radiating out from an object is described by [Stefan–Boltzmann law](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) it depends on the temperature and the emissivity of the material. Emissivity is how good a material in radiating out energy. The result is the power per square meter.
So if you heat an object with the same emissivity as the sun with a surface area of one square meter it will emit the same amount of energy as a square meter of the sun’s surface. The sun is enormous, its surface area is 12 000 times larger than the Earth so the amount of energy of a single square meter is only a small fraction of the total amount of energy. The surface area of the sound is 6 billion billion square meters.
This is really not any different than a candle emitting less heat than a large fire even if they burn at the same temperature.
You can collect energy and then dump it into an object really fast, and for a short period it can get very hot. Energy can come from various non-sun sources.
Even a bolt of lightning is hotter than the surface of the sun. https://www.weather.gov/safety/lightning-temperature The important part of that is that a large amount of energy builds up and is discharged very quickly.
One thing that hasn’t been mentioned is that the surface of the sun is cool compared to the interior of the sun. [It’s hotter than, like, Phoenix](https://whatif.xkcd.com/115/), but 5800 K is less than one hundredth of the temperature of the interior.
Even that temperature has been exceeded on Earth… by [a factor of a million](https://blogs.nature.com/news/2012/08/hot-stuff-cern-physicists-create-record-breaking-subatomic-soup.html) or so.
Unmentioned so far is an interesting quirk of optics: whatever you do, you cannot directly* use sunlight to create anything hotter than the surface of the sun!
So however hard you try and whatever the size of your lens(es), you won’t get 7000°C this way. In this special setting, the title’s presumption is correct!
*: Directly means things such as mirrors and lenses; don’t change the light into a different form of energy in-between.
OK, an experiment. Take something plastic and rub it with something furry. Now move the furry thing away and observe tiny sparks. Those sparks are *incredibly* hot. How do we know? Because they gave off light. We don’t need to care how hot except that they’re hotter than their only source of energy – our muscles. So it’s possible to concentrate energy till it’s hotter than its energy source. Even if we were 100% solar powered, we could still make stuff that hot.
The average energy received by earth would be less than the average energy output by the sun***. But we can exceed the average energy by collecting and concentrating it into a smaller volume in space time.
To see an ELI5 analogy of this, think of handing out 1$ to everyone that passes you on the street (and this is the only source of money in the world). Is it possible for anyone to go purchase a 10$ item? Yes, if ten people pool their money into one person’s wallet. Also yes, if that one person passes you ten times and saves his money over time.
***Caveat, the earth itself is made up of stored energy in the form of mass and heat. We can convert this mass back into energy in nuclear reactors, extracting energy and heat from a non-solar source. For example, heavy elements like uranium release high amounts of excess energy when split. We can extract the Earth’s internal heat as well for a non-solar source.
A nuclear explosion from a manmade nuclear bomb reaches several times the temperature of the sun. Do you think all that energy came from the sun?
The equation used in the measurement for the surface of the sun uses kilowatts radiating out as the coefficient. We just need to find a way to apply the more current to a material than is being radiated out of a single section of the sun…. if that makes sense.
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