I’ve heard a few times now in various scientific fields, mainly experiments, about things getting as hot as the sun.
How is this possible? Surely if you do something and you create heat that is that hot it would melt anything surrounding it?
Would love to know how this works 🙂
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You can use electromagnetic fields to prevent the hot substance from touching any solid msterial that would melt.
This is the method used for fusion reactirs, which need to get insanely hot. The insanely hot plasma can be moved with magnetic fields, so if you create one in just the right shape you can basically contain the plasma without it touching a wall.
Btw that‘s also how antimatter can be stores; after all it would annihilate itself if it touched matter
The surface of the sun is the coldest part of it, and those temperatures can be pretty easily reached by an electric arc.
If you’re not heating very much matter up, you can reach extremely high temperatures without a lot of actual heat. How hot something feels is more about the quantity of heat entering your body than about what temperature the thing you’re touching is. If you touch aluminum foil right out of the oven, you don’t get burned because your fingers have a whole lot more thermal mass than the foil does, so the foil cools down much faster than your fingers heat up.
If we go back to electric arcs for a moment, some welding machines use a piece of tungsten as an electrode, even if the arc temperature is double the melting point of the tungsten, you can keep it intact by cooling it down while the arc is lit, some torches even have water cooling.
The highest temperatures we know about are in particle accelerators, like the LHC. Remember that temperature is a measure of average kinetic energy, and we can get these particles very close to the speed of light. Nothing in the sun is moving that fast, even in the core, so the temperature is lower, even though there’s vastly more actual heat, it’s just spread out over a lot more matter.
time is the important factor here. the sun is largely consistent in pumping out steady heat. much of these instances where something gets as hot as the surface of the sun will only be for an extremely short period of time and in a very small space, so while there’s a lot of heat, its overall a small amount of energy available that instantly gets spread into the surroundings, so nothing around the event really heats up that much more.
Most things that are very hot are also very small amounts. A electric arc welder can create a 7000 degree arc, but it’s only in microgram amounts of air. A laser array that heats a fusion experiment target to millions of degrees is shooting a pellet of a few milligrams.
Things that are very small can be very hot without having that much total energy.
It’s usually not for a very long time, think something like a flash of lightning which can be up to 5x hotter than the surface of the sun and yes that does melt things
Mainly, the very hot thing being described that way is also very small so has little total heat energy. That same amount of energy spread out over a very large mass will only provide a fairly low temperature. That is, heat is not temperature. Temperature is a measure of the total kinetic energy (energy of motion, vibration, spinning, and wiggling of atoms, basically) of the mass under examination. Heat is the sum of all that energy plus the energy hidden in the structure itself (the arrangement of atoms uses energy too and can absorb heat). Same total heat spread over larger mass leads to much lower average temperature.
The amount of energy in a very small object will be rapidly diluted if allowed to leave and spread to another much larger mass. If each atom gives all its energy to 100 other atoms, the other atoms will only have 1/100 of the energy of the original atom (on average). And there are way more than 100 atoms in the surroundings to each atom in the hot item so temperature rapidly decreases from the source. The amount of energy is the same, but it is shared with a hugely larger number of atoms, so the temperature is way lower. This would, of course, quench the very hot item very quickly if new energy is not constantly added.
Somewhat like smashing a cue ball into the racked balls at the break, but way more dilution because there are an absurdly much larger number of atoms in the surroundings than in the tiny but very hot mass.
Making a hot spot does not mean everything around it will rise to the same temperature very quickly though. It takes time and requires that energy is constantly added to the hot thing, or the hot thing will cool off fairly quickly and stop being hot. In your question, you ask why the containers don’t melt. Well, a melting container would suck heat and cool the experiment so the high temperature would be very short lived. So, for such experiments, we don’t use a container that will melt over the course of the experiment. For many purposes, highly heat tolerant and heat resisting substances like ceramics can be used, In many cases, the experiment will involve a tiny mass (like micrograms or milligrams at most) so there is little heating of the container except over time. Often, when heating of the container would be a problem, the material will be suspended in a magnetic field withing a high vacuum, so there is as little interaction with surrounding mass as is possible. Interaction with mass will quench the object, and that is not at all desirable.
Nuclear bomb explosions that are as hot as the sun do involve a considerable amount of mass (generally kilograms of nuclear material, not tonnes) and do release a lot of energy, so the region affected by extreme heat is fairly large (enough to set a city on fire, but most of the city never gets even close to as hot as the sun; 500 degrees is a lot different from 5000 degrees). It is still only in the very heart of the explosion/reaction that the temperature is as hot as the sun. Temperature drops rapidly with distance as the surroundings get heated and the initial energy is spread out over a large volume of mass.
The sun’s heat is only a lot here on earth because the sun is so dang big (it is HUGE) and the energy it loses at surface is continually replaced by new energy from inside.
Well, the sun is extremely hot, millions of degrees, but in its core. Turns out that heat transfers very slowly to its surface so any energy that the surface of the sun gets from below, it radiates it very fast, making it not that hot. If you drop tungsten on the surface of the sun (assuming you can get it past the sun’s corona), it would melt but not boil.
Thanks everyone for some really great comments and feedback, there are some really great explanations here and it’s helped my understanding.
Ya’ll are all awesome :)!
The difference is in the anount of heat (and pressure), not the temperature.
Others are talking about creating solar temps in a lab and such. But my oxyacetylene welding torch creates a temperature hotter than the surface of the sun. That’s not exotic at all. The core of the sun is much, much hotter, but even if we were to create those temperatures in a lab on earth, or by exploding a thermonuclear weapon, the reason it wouldn’t somehow ignite everything is that it is a relatively small amount of matter being heated to that temperature.
Temperature measures how much energy is contained in each atom of whatever matter you are measuring. Heat is the energy of a whole system or volume of stuff. So, if you have a torch creating a temperature at its tip of 6000K, or some experiment creating a temperature of 10 million K, it will be in a tiny space. Each atom in there is that temperature, but they are surrounded by the rest of the world, at something like room temperature. As the very hot atoms collide with cooler ones (and also radiate heat) their surroundings are warmed, but they are losing heat in doing so. Their temperature is decreasing. So even an incredibly hot bunch of atoms can only warm so much of its surroundings before it loses all its heat energy and becomes the temperature of its surroundings.
Think of it in the extreme case. We somehow raise the temperature of one single atom to 20 million degrees and let it loose in the air. It will heat up the millions of atoms nearest to it by a bit, losing energy in the process. But those millions of atoms are within a millimeter if the first hot atom, and they are each a huge amount cooler. Out at a centimeter away you have a thousand times that number of atoms to heat, and they each rob the core of more energy. The amount of energy it took to raise an atom 20 million Kelvin will raise 20 million atoms a degree Kelvin, more or less (to an ELI5 approximation). So the heat energy dissipates quickly.
Even a hydrogen bomb faces the same situation. There is a lot more mass there, and it’s set up to create the conditions for fusion, so it releases incredible energy. Enough to be hugely destructive over a wide area. But the actual heat is dissipating the same way. Everything it heats up robs the hot parts of energy, and on a scale of the earth, or even the earth’s atmosphere, there is a lot of mass to heat up.
This leaves a lot out, of course, but covers the temperature question. The reason you don’t get a self-perpetuating fusion reaction has to do with mass as well, but it’s because you need incredible pressure and temperature to run the fusion core of a star, and that is only powered by the gravity of the gigantic mass of the star.
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