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The short answer is that it is something else.

When most people think hot or cold they are really thinking of a physical object, something made of matter. They usually don't think of a vacuum.

Let's first think about an object near you, here on Earth. It gains heat through several means two of which are [conduction](https://en.wikipedia.org/wiki/Thermal_conduction) from the surrounding matter and the other is by absorbing [heat radiation](https://en.wikipedia.org/wiki/Thermal_radiation).

Conduction occurs via actual physical contact, whether it be the molecules in the air or the contact of the molecules of a liquid or a solid.

Technical point: in this post radiation is referring to heat radiation, the absorption of energy or the release of energy by photons. These photons can have long wavelengths like infrared light, microwaves or radio waves. It can be short wavelength like visible light or ultraviolet light. It can be very short wavelength photons like x-rays or gamma rays.

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This object will also lose heat by a number of means, two of which are again conduction and radiation. If it is really hot then the conduction will be large and it is what causes you to pull your fingers away from a hot object.

Also if it is really hot the radiation emitted by the object can even be visible and the object will change colour from red, to orange, to yellow to white as it heats up. Kind of like what you see at a black smith's shop.

If you have ever sat near a fire (camp fire or fireplace) then you have even felt that heat radiation on your face or hands.

An important point to know is that an object will continue to gain temperature or lose temperature until it reaches a balance between heat coming in and heat going out.

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Okay, now on to objects in space, and by space, I mean a vacuum.

Let's think about a meteor in space. This object can no longer gain or lose heat via conduction as nothing is actually touching it. So we lose one major heat transmission pathway.

So the only way for this meteor to gain heat or lose it is via heat radiation.

If the meteor is in direct sunlight then it is going to heat up because its means of dumping heat via radiation is limited (at least while it is relatively cool).

If the meteor is in shade then it is going to cool down, somewhat slowly, again because it is only via the mechanism of heat radiation which is pretty weak when its cold.

This meteor will continue to cool down until it is at the temperature of the Universe by which I mean the [Cosmic Background Radiation](https://en.wikipedia.org/wiki/Cosmic_microwave_background) or CMB. This is the left over heat energy from the [Big Bang](https://en.wikipedia.org/wiki/Big_Bang).

It is measured to be around 2.7 K. That's very cold. 

Wait. What did I just say? The temperature of the vacuum of the Universe is at 2.7 K?

Really what this means is that if an object was cooled down to 2.7 K then the blackbody heat radiation that it would emit would be the same as that you can measure from the CMB of the Universe.

I guess it is a bit of lazy shorthand that science types use to say the vacuum is at 2.7 K when what we really mean is that it's blackbody temperature and the resultant thermal spectrum is at 2.7 K.

That's quite a mouthful so we usually just go with the lazier shortcut.

#### Closing Words

Space is really neither hot nor cold.

The background radiation from either the CMB of the Universe or a nearby star may cause you to heat up, or cool down if you are hotter than it, and it all really depends on the specific heat balance situation that you are in.

*Thank you for reading my post.*

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<sub>You may also want to take a look at my STEM blogging style guide [here.](https://steemit.com/steemstem/@procrastilearner/procrastilearner-s-style-guide-for-science-and-technology-posts-this-is-a-draft-for-comment)</sub>
<sub>You may also want to take a look at the Steemstem curators' style guide [here.](https://steemit.com/steemstem/@steemstem/helpful-guidelines-for-crafting-steemstem-content)</sub>