What is the Temperature in Space?
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When calculating the temperature in space, it is important to understand that most estimates must take into account the varied makeup of space. Outer space is the portion of the universe which is almost entirely empty. Unlike the small pockets of our universe which are inhabited by stars, planets, and other large sections of matter, outer space contains very, very little. Nonetheless, it is not entirely empty, and this is important to understand when considering the temperature in space.
The short answer is that the temperature in space is approximately 2.725 Kelvin. That means the universe is generally just shy of three degrees above absolute zero – the temperature at which molecules themselves stop moving. That’s almost -270 degrees Celsius, or -455 Fahrenheit.
In one sense, we can talk about the temperature in space as being 2.725 K. This shifts a bit from place to place, but not by much more than a thousandth of a degree. For all intents and purposes, this is the generally accepted temperature in space.
To understand it further, we can look at what a temperature actually is, and what space actually is. When we’re measuring the temperature of something, what we’re really talking about is the energy of the molecules in it. It has to do with the density of the molecules, which in turn helps determine how often they run into one another. If they don’t run into one another, they never really lose their initial energy.
Space is very, very empty. There aren’t many molecules out there, which means none of the molecules have much of a chance to run into one another. What does this have to do with the temperature in space? If we were to take a random molecule in space, say one that is part of the solar winds, and estimate its temperature, it would probably be around a million or more degrees Kelvin. That’s because this molecule hasn’t been bumping into things to get to the temperature it naturally wants to be at – what is called its equilibrium.
How much sunlight a particular area of space is exposed to also plays an important role in determining the temperature in space in that area. When scientists talk about 2.725 K as the temperature in space, they’re talking about an average temperature – actually, what is called the Cosmic Background Radiation, which is the energy still left over from the Big Bang. If we were to look at space a bit closer to home, even somewhere very far away such as just outside of Pluto, the temperature would probably be closer to 35 or 40 K. Still very cold, but nowhere near as cold as somewhere in deep space, far from any sunlight.
So what is the temperature of space? That’s a bit like asking what the temperature of Earth is. We can find an average, and we can give a good guess for a particular region, but there is no one-size-fits-all answer. Still, 2.725 K is a fairly widely accepted answer to this frequent question, although it does not represent the temperature range that is as expansive as space itself.
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The reason air would rush out into space through a hole in a space ship is the pressure difference. Because space has so few particles in it, the pressure, or lack thereof, creates a vacuum. If someone were to enter space without a pressurized space suit their blood would boil, amongst other things, before they froze.
- anon33797
Temperature is, in a sense, a measure of the sum of the energy present in the molecules that make up the object of interest. If no matter exists you have nothing of which to measure the temperature.
That does not mean that the potential for temperature increase does not exist. Radiation from stars has the ability to transfer its energy when it strikes matter thus causing an increase in the energy of that matter and a temperature increase. This increase is based on many factors including the type of radiation from the stars that reach the object, the intensity and density (related to proximity) as well as the molecular make up of the object being struck by the radiation, even the texture of the surface can have an influence on the energy absorbed by the object. Since outer space is mostly empty there are very little molecules for which the radiation from stars to transfer its energy to, so the temperature of space is very low. - anon33401
If space have no air at all, why is it cold? why isn't it just 0?
Also, if we are (for instance) in a space ship and a door opens, why would the air inside of it and in our body be vacuumed out? - anon32097
I think it is perhaps easier to see the sun as not providing heat but rather providing a catalyst for heat. The sun produces radiation. The radiation affects molecules, causing them to speed up. This speeding up of molecules generates heat.
Friction is another catalyst but the heat is not caused directly by things rubbing together but rather from the way the molecules react to the friction. Again they speed up and end up producing heat as a result. In the case of the sun, the more intense the radiation (proximity, density, angle) and the more direct contact, the more molecules react and the hotter they become. Looking at a microwave, you can easily see that different types of molecules react differently to different catalysts. - BruceBarstow
Temperature is defined as the average kinetic energy of molecules. Most of the space is empty, no molecules, thus the concept of temperature becomes meaningless. The 3 degree K background radiation does not require atoms as most of the space is empty.
- anon24601
You say you'd freeze to death in outer space - surely you wouldn't actually lose temperature that quickly - I mean sure its cold, but there's no particles to pass your body's heat to, so the only way to lose your body's heat is through radiation, which would take a while. I'd be more worried about the lack of air...
- anon23866
H20 isn't required for anything to freeze, it simply has to be matter. Ice however forms as a result of frozen air or water. Mars for example, has plenty of ice, but no water! The ice on mars is thought to be many things, most hopefully frozen methane!
Electronics work optimally in a vacuum, so satellites don't have a problem, especially since they are heated using their solar panels! The slower molecules move, the higher the temperature, and vice versa. - anon22595
Well... you'd probably freeze to death, cus ur body is only like what, 75% H2O (Water), and it would probably be like very bad frost bite, and would just numb all pain away... Painless? maybe, maybe not... I just would like to make the suggestion that you should probably not choose to die like this. Just cause of the scenario of a small, fast moving, space chunk hitting you, and blasting you into a million pieces, hahaha
- anon22548
so if a body is in space it would freeze because of the cold temperature? But doesn't that require H2o?
- wantoknow
what is the temperature around the satellite if there is no temperature controls (i.e temperature of the part which is facing the sun and which is in the shadow region - with and without facing the sun)
- anon17862
Can I assume that in order for temperature to be at all meaningful, there must be matter present which temperature can be measured, so that the temperature of absolutely empty space really has no meaning?
- emdrgreg
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