Why is space cold and how cold is it?

Question

Space is freezing cold and the earth is warm, but the sun is right there! So if space is cold here, would it be even colder farther away from the sun?

Answer 1

Actually, space doesn't have a temperature. Since, as people have stated before, the space we're familiar with is a vacuum - that is, it doesn't have much matter in it, at all (only a few particles per cubic meter). However, if you wanted to get REALLY technical, you could say that there are many, many particles in the vacuum of space, due to the quantum fluctuations and virtual particle pairs that are always being created and annihilating - but, they're called "virtual particles" because they exist for such a short amount of time, they don't really have any effect or bearing upon space. So, for simplicity's sake, we'll just forget about them.

Now, let us suppose that we put a thermometer in the very deepest, very darkest part of space. First, it would have to cool off, which would take a very, very long time, because in order to cool something off, energy has to taken away from it. In our atmosphere, things cool off by transfering energy to other particles, which remove it. The easiest example to relate to is sweating. When we sweat, as you know, your body produces a liquid that collects on your skin. As the liquid evaporates, the water molecules carry the heat away from your body into the surrounding air, cooling you off and preventing you from overheating. To get a better "feel" for it, spray youself down with water, and then stand in front of a fan. As the air blowing past evaporates the water, it removes heat energy from your skin - you'll get very cold pretty quickly.

This was also the principle behind the thermos - it was a double-layered container with a vacuum in the space between the inner container wall and the exterior shell. Because there was a vacuum between the container of liquid and the exterior shell of the thermos, there would be minimal energy transference - which means little heat lost. However, a perfect vacuum is very hard to generate, and nowadays thermos containers are full of insulation, not an evacuated chamber, so thermos containers aren't as good as they used to be.

This is why it takes so long for stuff to cool down in space. Since, as we discussed before, there aren't many particles *at all* in the vacuum of space, it takes a very, very long time for something to cool down. When it does, however, it won't register absolute zero.

If you had an exceptionally accurate thermometer, it would read 2.728 Kelvin (remember, you always say the numerical value and then "Kelvin" - it's NEVER "degrees Kelvin" - just some science etiquette :-) ). Anyways, it's going to register 2.728 because of the cosmic background radiation. This stuff is microwave radiation left over from the Big Bang, and if you goggle image search "WMAP" (which stands for Wilkinson Microwave Anisotropy Probe), you'll see the map of microwave radiation in the cosmos. If you read about it, it's even cooler. But, long story short - it's the radiation left over from the Big Bang.

Now, over time, as the universe expands, this value will decrease. But, that'll take billions of years, so for now, it's safe to say that it'll be 2.728 Kelvin. Now, this numerical value might vary from source to source, but if you read anything by Michio Kaku or Stephen Hawking, they both identify it as 2,728. So, trust who you like, but I'll stick with my two world-class astrophysicists.

Now, if you hold it in space by a star, the temperature will rise, because the solar radiation will impart energy upon the object, causing the particles in the object to bump, jostle, and move more - raising the temperature. (After all, temperature is only a measure of the energy, or amount of movement, of particles).

Hope this helps!

Answer 2

The universe does indeed have a temperature, and it isn't absolute zero (as some morons have stated =\). Absolute zero is a theoretical temperature at which all the average kinetic energy of the atoms in matter cease.

When you ask the TEMPERATURE of the universe, you must understand what exactly you want to know. "Temperature" is a measure of the AVERAGE kinetic energy in an object. Think about this when you said in the question, "Doesn't space become colder the farther you are away from it?"

In terms of the universe as a whole, that relatively large decrease in temperature as we see it from Earth pales in comparison to the average temperature of the entire space-time continuum (i.e., the universe entirely). Other stars everywhere in the universe influence the space around them in the exact same way, though that decrease individually counts for near nothing in terms of the entire universe as one.

In short, scientists have discovered the temperature of the universe by measuring the cosmic microwave background radiation that still lingers (which we believe is evidence of the Big Bang). The brightness of the relic radiation is measured as a function of the radio frequency. To an excellent approximation it is described by a thermal of blackbody distribution with a temperature of T=2.735 degrees above absolute zero (that is, approx 3K).

Answer 3

Heat (kinetic energy) is transferred by collisions.

Space is "cold" for a body in that space to the extent that there is no radiation (like sunlight) moving through that space. (Think of the dark side of the moon.) That's because, away from the stars, there's very little matter in "outer space" to "bump into" things and give them more energy (heat them up).

Now, once that body is near a radiation source like the Sun, it might absorb a LOT of radiation. (Spacesuits are highly reflective!)

So the surface of Mercury is VERY hot (700 C??) because it's close to the Sun (like being close to a campfire). But the surface of Pluto is very cold (like being far from the same campfire).

Out between the stars, the AVERAGE temperature gets down near 0K, though there might be very energetic particles moving through that space.

Answer 4

Space is not really cold....if u know what i mean. People say it is cold, compared to the heat from the sun on the earth. Even though the sun is shining and other stars are too they don't heat up the whole universe. Sorry , bu i don't know how cold it is.

Answer 5

There is no heating source, therefore it is cold. The sun does not have the capability to heat up the entire universe. It really powerful to the universe like it is to us. If you want details, then you should go to a website and get professional information. Yes, space is colder farther away from the sun.

Answer 6

The coldest temperature (absolute zero) is about -486 F. Absolute zero is defined as the absolute cessation of all molecular activity. No movement, no friction, no heat. There is also second-hand heat (not the real term) which comes from radiant bodies such as suns/stars. This can be either direct or reflected off another body and you must be close enough to the source to feel the heat before it is dissipated by distance or blocked by other matter. Otherwise, it's all about ice cubes.

Answer 7

Space is really cold. Near absolute zero,which I believe would be -460 degrees Fahrenheit. The sun gives off energy at the rate of one million horsepower per square yard. earth only gets a small portion of its heat. The rest goes off into space in all directions.At 93 million miles it is just right for us. The sun is one million three hundred thousand times bigger than the earth. 887,000 miles in diameter compared to earth's almost 9000 mi. in diameter.

Answer 8

The temperature of a gas is defined one the basis of the average kinetic energy of the molecules. So according to the definition, space in the solar system is rather hot because the few molecules that are flying around are accelerated by the "sun wind", i.e. radiation from the sun.

Nevertheless, you might freeze to death if you were flying freely around in space in spite of a temperature of maybe 1000 degrees C.

This is because there are so few gas molecules that their energy is irrelevant in practice. You will loose energy by radiation from your body (the same radiation that makes you see other people in the darkness if you have an infra-read binocular).

Answer 9

Space is cold because there are barely any particles. Also, I don't think emphasizing on the Sun helps, there are at least 70 billion trillion stars out there, each giving out enormous amounts of energy.

Answer 10

Space is dense matter, our planet has a burning star called the sun to orbit and warm up. space is cold and it dose not orbit the sun or any burning star to create warmth.So space is not in a orbit to rotate around warmth, so dense space is very cold energy.