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I was thinking recently about what might happen if you were to place a block of material in the middle of a complete vacuum. Obviously there's not going to be a way to ever achieve such a scenario but what would happen if you were to put a block of let's say steel at 100C in a vacuum such that the block is not in contact with any material connected to the containment and have it such that outside energy is minimized. I assume the block would lose heat/vibrational energy but what would be the mechanism for such an energy loss and what time scale would it take for the block to reach let's say 0C?

Let me know if there's anything I can add to make the question more clear.

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  • $\begingroup$ One word: radiation. See Stefan-Boltzman law. $\endgroup$ – Jon Custer Oct 25 '17 at 18:25
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The block of steel would lose energy via black body radiation. All objects at a temperature above absolute zero according the the priciples of black body radiation. A steel block at 100 degress C will radiate in the infrared. A typical blackbody spectrum is shown below. Notice how the frequecy gets smaller as the objects temperature gets less. Radiation can pass thru a vacuum fine.

enter image description here

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the sun is a block of material in the middle of a complete vacum. Although its not in contact with any material it loses energy through radiation.Radiation does not need an indermidiate medium in order to exchange energy. I also believe that there are ways to achieve the same with a block of steel in a given temprerature suspended in a vacum through magnetic forces. You can easy find from littature the rate of radiation of any material.

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An answer cannot be given unless you make a statement about the vacuum which can have em waves (radiation) travelling through it.

Your block will lose energy by radiating it out as electromagnetic waves (mainly infra-red) but at the same time it might also be receiving radiation from whatever is outside it.

You will also have to consider what the surface of your block is like because that will also be a factor in terms of how much energy your body emits and absorbs.

The rate of energy emission is proportional to the temperature of your block (in kelvin) to the fourth power.
This is called Stefan’s law.

If the vacuum radiates much less than your block then all you need to do is to consider only the radiation emitted from your block.

To estimate the time you will need to do an integration as the rate of energy loss by radiation will depend on the temperature of the block and remember to have the temperatures in kelvin.n

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The amount of energy will depend on the mass of the block and what it is made up of. A small body will lose energy at such a slow rate that it can outlast our sun.

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