1
$\begingroup$

There are trillions of stars like the Sun in our universe so "why is it space is dark and cool?" Well I really meant that our stars, giant balls of gases which exist by expelling huge amount of energy in the form of heat and light. So my question is: Why space is dark even though there are stars like sun in our space giving huge of bright light? where does these energy goes? well I meant i.e for example take the planet earth the one side of the which faces the sun is bright and hotter than the earth but another is the opposite so my question is even though there are so many stars in our universe why the space is like the side of the earth that does not faces the sun?

Improve this question
$\endgroup$
2
  • 6
    $\begingroup$ Read up on: Olber's paradox. $\endgroup$
    – Sean E. Lake
    Commented Mar 10, 2018 at 6:12
  • 2
    $\begingroup$ First, space is dark to the "human eye", it is actually filled with infrared radiation (the so called Cosmic Background Radiation). And it is cold because of the huge interstellar distances (2.7 K to be exact). $\endgroup$
    – Yuzuriha Inori
    Commented Mar 10, 2018 at 6:17

1 Answer 1

Reset to default
0
$\begingroup$

First, there seems to be a flaw. Space is a vacuum, devoid of any matter. Since heat is due to the vibration of atoms, space has, technically, no temperature.

I think you might be asking about why gas in space is so cold. Well, this is due to the huge distances between the stars and you. They are light years away. In addition, conduction and convection, which rely on material contact, cannot happen. Only heat radiating from the stars as electromagnetic waves can reach us. Now you see that the heat output of the sun is $3.8 \times 10^{26}$ watts, a rather small number, if you think about it. Now imagine that moving to earth, dissipating much energy along the way. That leaves us with a very small amount of heat. That is why gas in space can be said to be cold, not absolute 0 though.

Improve this answer
$\endgroup$
4
  • $\begingroup$ Most (over 90%) of the interstellar medium is quite warm, over 6000 kelvins. Most of the intergalactic medium is warmer still. $\endgroup$
    – David Hammen
    Commented Mar 10, 2018 at 12:06
  • $\begingroup$ Every cm$^2$ of space, even the most dilute parts, contain several hundreds of photons, which have a distribution of energies, and hence can be said to have a temperature. Since by far the CMB photons dominate over "astrophysical" photons — e.g. those emitted from stars — this temperature is the well-known 2.73 K of the CMB. $\endgroup$
    – pela
    Commented Mar 10, 2018 at 15:01
  • $\begingroup$ Well I think QuIcKmAths had understood my question $\endgroup$
    – user184625
    Commented Mar 11, 2018 at 6:27
  • $\begingroup$ And it is the right answer I am looking for it $\endgroup$
    – user184625
    Commented Mar 11, 2018 at 6:28