How does sun radiate heat if space is a vacuum though

how does sun radiate heat if space is a vacuum though

What is radiation?

yeah but how can a wave travel through a vacuum

Radiation =/= conduction

Eletromagnetic waves can, you dipshit.

I'm not saying they can't, I just don't see how. Aether really seems like the only way.

because QUANTUM

conductor what?like in termsw of a train conducting-driver?

The energy is transmitted as "wavicles"

OP's question really does get at something about solar/stellar physics, though, and I myself know nothing about such things.

My personal variant on OP's question is: how is it that these balls of heat-gas-light keep going for many millions of years, when surrounded by the infinite cooling void of ~three kelvins? What is their self-sustaining mechanism, and how is it that this mechanism keeps going for a very-long term?

I suspect that I have just asked a fundamental question of solar physics which a wiki visit would solve, but I don't want to ask wiki right now. I want to ask you, someone who knows these things and can break them down more clearly.

Fusion is extremely energetic. The sun has A LOT of hydrogen (the thing that produces the most energy when you fuse it).

Note also that space isn't exactly an "infinite cooling void". Empty space is very insulative, and yes, things left out there will eventually cool down to 3K, this assumes the thing has no ability to warm itself whatsoever (that is, doing basically any kind of reaction). The human body, for instance, provided you have necessities like food, water, oxygen etc, would be able to easily keep itself warm.

So obviously, to the sun, the cooling effect of background radiation is basically nothing.

why is hydrogen the thing that produces the most energy when fused?

The reason EMR can travel through a vacuum is because photons behave as both waves and particles and don't need a medium to propagate through (like sound, which isn't really a physical thing by itself, but the result of compression of other particles). Heat is just radiation, my man.

The "void" isnt cooling like cold air, the low temperature particles in space are few and far between. Radiation is the least efficient from of heat transfer, and the sun loses heat in a vast majority by radiation. Vacuum is essentially the perfect insulator of heat convecton. Stars stay hot for a long time because they are massive hydrogen fusion reactions and have tremendous ammounts of hydrogen to fuse. When hydrogen atoms fuse they form helium and produce positrons and energy. Photons carry the energy through the vacuum until they interact with something else to transfer their energy, ie. Earth.

Interesting. What for you are obvious statements, are not at all obvious to me for several reasons, which deserve clarification:

-I have never taken a college-level physics course of any kind,
-I have the vague idea that a star "burns" hydrogen, the first thing that you mention (probably a mistaken view, since I'm taking your word hydrogen and comparing the idea with fuel for a conventinlal fire on earth. What is wrong with this, what chemically/physically goes on, such that it can keep repeating itself for an eon, but not indefinitely?)
-I don't understand what you mean by insulative, in terms of thermodynamics. the word as you seem to use it (let heat out, dissipate heat?), seems to be the opposite of its everyday use (keep heat in, concentrate head).

-your reaction part however seems to make sense. Human bodies are able to "do physical processes" that locally fight entropy, for a while. likewise stars. Is this a reasonable and valid comparison that I've made, and did it capture what you meant?

-I still don't get how you reach your conclusion, due to my naivete. I would appreciate your expansion on this.

Not the guy you replied to, but the reason stars fuse hydrogen is because it is the most abundant element is the universe as well as the simplest (only 1 proton and 1 electron, as opposed to, say, oxygen~ 8 protons, 8 neutrons, 8 electrons). Every other element that exists naturally exists because it was fused from lighter elements before it, which were the result of the fusion of lighter elements(etc)... which were the result of hydrogen fusing to form helium, all within the core of a star larger than our own.

Is hydrogen the most energetic fusion reaction? I don't know, but the amount of energy produced by hydrogen fusion has nothing to do with why stars are made of it.

>-I have the vague idea that a star "burns" hydrogen...
It's not a horrible way to think of it, just a long as you are aware is isn't LITERALLY burning, and as such, does not require oxygen.

Fusion requires lots of heat and pressure in order to make happen. You have to get atoms very close before they bind together for good (and release a bunch of energy in the process), and atoms don't like to do this because of electromagnetic forces pushing them away. Luckily stars are very very heavy, and that means lots of gravity. Pretty much what defines a star is being heavy enough that the center of it gets so hot and pressurized that the atoms start fusing.

Doing this though, creates radiation pressure, which is literally the heat and light pushing out and away, directly against gravity. Every stars sits at where these two forces equal out, depending on how heavy the star is this also results in big changes in it's size as a result. Anyway, our sun is only fusing enough hydrogen to balance out its gravity, and this turns out to be not that much of it, so it can keep doing this for quite a long time. Eventually, though, all the hydrogen gets fused into helium, and then it's forced to fuse helium, which doesn't produce as much energy as hydrogen, so it has to fuse more in order to counteract the gravity. Then the helium runs out, and it goes for even heavier elements, which make still less energy, and this quickly spirals out of control towards the end of the star, which can get complicated so I won't go too far into it.

>-I don't understand what you mean by insulative...
Empty space is literally nothing. By insulation I mean that, being surrounded by it, it's basically impossible to lose heat through conduction (touching things of a different temperature). The only way is by radiating that heat away, everything does this, including humans, but unless you're extremely hot, it's not a whole lot. If you've ever put your hand in front of your face by a fire, you've felt the difference the fire's radiative heat made on your face.

Stars fuse hydrogen atoms (1proton, electron) to form helium atoms. This is nuclear reaction (as opposed to a chemical one). Fusion occurs because the gigantic mass of a ball of hydrogen (a star) has such a great gravitational pull that it creates a high enough internal temperature and pressure to begin fusion, which releases large quantities of all kinds of radiation (UV, infrared, visible light, heat).

There is no burning, burning is the breakdown of molecules by heating them to the point that they readily bond with oxygen, causing other chemical bonds to break and energy is produced by the breaking of these bonds.

The reaction that a star undergoes is nuclear fusion. Hydrogen atoms are squeezed together by immense pressure and gravity, when they are squeezed hard enough the nuclei of the hydrogen combine creating deuterium, which is hydrogen with a neutron in the nucleus. This process produces a neutrino and a positron. An additional hydrogen is squeezed with deuterium and forms helium-3, and releases radiation. The heat that reaches earth is the energy from this fusion reaction. Eventually as fusion continues, heavier and heavier elements form in the core. When the core is too heavy to sustain fusion, the remainder of the star becomes unstable and is jettisoned into space (a supernova).

Insulation is somethings ability to restrict the flow of heat. Vaccum has no particles in it for heat to transfer between, so radiation of photons (very inefficient compared to convection) is the only way for heat to transfer out of the star. If there was air between the sun and earth the air around the sun would be heated to the temperature of the sun, whixh would heat the air surrounding that, which would eventually heat the earth to the temperature of the sun. Vacuum insulates us from direct convective heat from the sun.

>Fusion is extremely energetic
"Sun's interior indicate a power density of approximately 276.5 W/m3,[73] a value that more nearly approximates reptile metabolism than a thermonuclear bomb"

To cool down quickly, the hot object (the sun) needs a cool object to transfer heat to. Metals make very good heat conductors (coffee cools off quickly in an aluminum mug), liquids are okay(you get cold if you stay in the pool too long), gases are awful (staying under a blanket too long will make you really warm). Radiation is the least effective way to cool anything.

Top kek

Oh okay, this is helpful! So you provide a physical/chemical/forces model of how stars are just places where all of this is near (but of course not quite) near equilibrium, which explains the existence of stars.

Later posters (including possibly the guy I initially replied to) seem to go along these lines, but I still have general issues:

so a star releases a shit-ton of energy, is that an accurate statement? Then do most of its atoms/subatomic particles stay in its region of radius, for the above "near-equilibrium" model of forces almost cancelling each other out, is that still right? This suggests to me that the atoms are recycled constantly in the process of a star being a star.

I also gather from the helpful replies that once stars start producing higher elements such as helium, that this is an indication of the eventual decay.

>Vacuum insulates us from direct convective heat from the sun.

Thank goodness!

>Then do most of its atoms/subatomic particles stay in its region of radius, for the above "near-equilibrium" model of forces almost cancelling each other out, is that still right? This suggests to me that the atoms are recycled constantly in the process of a star being a star.
They do, although sometimes it ejects some surface matter during a solar flare.

>I also gather from the helpful replies that once stars start producing higher elements such as helium, that this is an indication of the eventual decay.
In fact, although I am slightly out of my knowledge here, I believe this is where all heavy elements, pretty much anything that isn't hydrogen, originally came from. The oxygen and carbon that mostly make up our bodies came from dying stars, as goes Carl Sagan's famous quote "We are all made of start stuff".

I believe that the general consensus of cosmologists is that the big bang left only H He and Li, all heavier elements were formed in stars/accretion disks.