# Heat through a vacuum?

**URL:** <https://boards.straightdope.com/t/heat-through-a-vacuum/20910>\
**Category:** Factual Questions\
**Created:** [May 30, 2000, 6:12pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910 "2000-05-30T18:12:22Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Ozone](https://avatars.discourse-cdn.com/v4/letter/o/e95f7d/32.png) [@Ozone](https://boards.straightdope.com/u/Ozone)\
**Post date:** [May 30, 2000, 6:12pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910/1 "2000-05-30T18:12:22Z")

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I’m not schooled in physics, but it is my understanding that heat will not travel through a vacuum, as there are no molecules to bounce into each other. Space is pretty much a perfect vacuum, isn’t it? So, how do we get heat from the sun? If sound won’t travel through space, why does heat?

Please explain in layman’s terms if possible… 😃

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**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [May 30, 2000, 6:16pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910/2 "2000-05-30T18:16:32Z")

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You have answered your own question. Heat will travel through vacuum in the form of radiation.

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**Author:** ![BigJoe](https://avatars.discourse-cdn.com/v4/letter/b/b9bd4f/32.png) [@BigJoe](https://boards.straightdope.com/u/BigJoe)\
**Post date:** [May 30, 2000, 6:22pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910/3 "2000-05-30T18:22:46Z")

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As sailor has said. Photons, my friend, Photons

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**Author:** ![AWB](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@AWB](https://boards.straightdope.com/u/AWB)\
**Post date:** [May 30, 2000, 7:37pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910/4 "2000-05-30T19:37:31Z")

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And what the thing with vacuum cleaners? If it’s a vacuum, there’s neither anything there to clean nor any dirt to clean off the non-existant thing in the vacuum.

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**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\
**Post date:** [May 30, 2000, 9:06pm UTC](https://boards.straightdope.com/t/heat-through-a-vacuum/20910/5 "2000-05-30T21:06:06Z")

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Heat can move in three basic ways:  
[ul][li]Conduction - a hot thing touches a cooler thing, and the cooler thing warms up. This is easily understandable in terms of molecules bonking each other.[/li][li]Convection - hot things move from place to place, for example a hot air balloon. This is just a hot thing moving around - no mystery here.[/li][li]Radiation - all things emit radiation based on how hot they are, and absorb radiation as well. If you have a hotter body near a cooler body, the cooler body will absorb radiation from the hotter body and warm up.[/ul][/li]  
You can sometimes feel radiation when you are near a hot fire or stove - I feel it on my cheeks, and I can readily block it with my hand.