How large would a bucket have to be to put out the sun?

To begin with, there is no amount of water that you can throw at the sun to ‘put it out’. Throwing water on the sun would actually make the sun burn even more.

Isn’t the sun like a giant fire?

The sun’s process is nuclear fusion, not chemical combustion which means that it is not a regular flame. You could put out a fire on a candle or a campfire with water because it would suffocate them due to the fact they burn through chemical combustion.

The electronic bonds between the atoms are altered in order without the nuclei changing in the atoms. Throwing water on a campfire would cause the water to absorb the heat from the wood (or any other fuel used).

The water will cool down the fuel to the point that the reaction can no longer occur, meaning that the fire will go out.

Hot temperatures are necessary for combustion because chemical bonds need to be broken down before the new ones can be forged. The high heat is needed for this to continue happening.

Hot Fiery Sun

Combustion is a self-sustaining reaction, meaning that it will provide the heat that continues to break down the bonds to create new ones. 

The most common source of energy in this reaction is thermal energy. So, water works to put out the flame by smothering it and also cooling the fuel down enough to stop the reaction.

So, what is the sun if it isn’t like the fire of a campfire?

The reason the sun is nothing like a giant campfire is because it does not carry out chemical combustion. Instead it carries out nuclear fusion. This is where the nuclei of atoms are forced together thanks to high pressure and then they stick together to become new heavier nuclei.

This is similar to chemical combustion is that heat definitely helps to knock the nuclei close enough together for this to occur. But that is where the similarities end.

But the main driving force is the high pressure that allows nuclear fusion to continue and even begin. This is the ultimate driver in nuclear fusion in stars.

This pressure is a direct result of the star’s own gravity. And the pressure is acting inwardly on the star to cause the pressure. The greater mass that the star has, the more pressure there is to cause this nuclear fusion.

In simpler terms: a star is so massive that the gravitational pull it exerts causes it to crush itself, and this in turn causes the atoms to fuse together.

What would happen if you through water on the sun if it doesn’t go out?

Throwing any amount of water on the sun would only increase its mass. This will therefore increase its gravity and thus the pressure that it exerts on itself. This means there would more atoms fusing and more nuclear fusion occurring.

The larger the mass of any star, the more nuclear fusion taking place and thus the more energy being pumped into the space around it. The total energy output of the sun with more mass per second, or its luminosity L is not normally linearly proportional to mass M. The sun’s energy output is around proportional to its mass to the power of four.

Following this math, just doubling the mass of the sun will cause an energy output of 16 times more energy. This would make it shine 16 times brighter. So, we would definitely see the effects of a sun with a greater mass thanks to a bucket of water being thrown on it.

How big would this bucket of water need to be then?

Well, in order to increase the luminosity L of the sun by just 1% we would need to pour a bucket of water over the sun that is the equivalent of 800 earths.

That is obviously unimaginable to our human minds. Because of this, us humans really have absolutely no way to affect the mass of the sun in any reasonable way.

Do any other stars show different behavior?

Yes, actually supermassive stars that are around twenty times the size of our sun, act very differently. They do have a linear relationship between their mass and the energy output unlike our sun.

This is down to the size of the star meaning that radiation pressure has a significant effect.

The way this works is that any time a surface reflects light, the light will exert a small amount of pressure on the surface. This is what happens within a supermassive star.

The light that is exerted from within the star will be reflected by the outer layers that are on the inside of the star. This causes radiation pressure. This causes a pushing outward on the star.

This outward radiation pressure can actually counteract the inward gravitational pressure that is acting on the star and causing nuclear fusion.

Does this not affect our sun?

No, our sun is too small a star for the radiation pressure to affect the balance or the gravitational pressure. The reason this occurs in supermassive stars is because there is a massive amount of light generated that causes the high radiation pressure.

If you were to add more mass to this kind of supermassive star, the gravitational pressure created as a result would not cause more fusion, it would just add more atoms for the fusion to occur to. This leads to a luminosity-mass relation that is linear and not quadratic like the sun’s luminosity-mass relation.

So, the difference between supermassive stars and stars like our sun is important?

When you add mass to stars around the size of our sun, the dominant effect is that the gravity will increase as a result. The effect will be around the same no matter what you were to throw onto it.

You could throw an earth sized bucket of gasoline or water and the effects would still be the same. The gasoline would have no different effects because nuclear fusion is far more powerful than combustion could ever be, so the effects of combustion are relatively obsolete.

But for supermassive stars, adding mass will have the effect of increasing the gravity overall and also the effect of giving the star more atoms to use up in fusion. This is because radiation pressure is incredible at counteracting gravity and therefore the effect of adding more atoms is simply more significant than adding more mass.

This is just like adding water would be more mass to the sun would be more significant than the fact that you are adding gasoline.

So, adding more atoms of hydrogen to a supermassive star will have more positive effects than throwing something like uranium. This is because the added mass would not really affect the supermassive star, but the fact that hydrogen atoms fuse better means that this would be more efficient for the star than any other atom type.

All of this is to say that chemical effects are nothing compared to the nuclear effects when it comes to stars. And even with our sun.

Leave a Comment