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Does planet Earth receive any heat at all from the millions of other stars in our galaxy?
Does the light that brings the heat perhaps cool down on the long journey through space to planet Earth, explaining why no significant amount of heat arrives here?
Does the Earth receive any heat at all from the millions of other Stars in our Galaxy ?
Effectively, no. Stars are too few and far between.
Qualifying that "effectively, no": From http://stjarnhimlen.se/comp/radfaq.html#10, the stellar magnitude from total starlight is -5. Compare that to the -26.7 magnitude of the Sun as viewed from the Earth. That difference of 21.7 means that starlight is responsible for one part in 1022 of the heating of the Earth. Another way to express one part in 1022 is "effectively none".
Another way to look at it: The Earth would eventually cool to 2.7 kelvins if the Sun and stars magically turned off. If it was only the Sun magically turned off, the Earth would cool to 3 kelvins. Compare that to the nice balmy 287 kelvins we experience thanks to the Sun.
Is it light that is bringing the heat and perhaps it cools down on the long journey in Space getting to the Earth and that's why no significant amount of heat is getting here ?
The stars in our galaxy are extremely close to us in a cosmological sense. Even the Andromeda galaxy is extremely close. The light we see from stars in our galaxy is more or less the same as emitted.
Over very, very long distances (much, much longer than the distance to Andromeda), the cosmological expansion of space means that light is redshifted. How much light is redshifted offers a clue as to the distance to some remote object.
We do receive a minuscule amount of energy from the cosmic microwave background. That radiation was not emitted by stars. It marked the transition from the very early hot and opaque universe to a cooler and transparent universe. The universe transitioned from opaque to transparent when the temperature dropped below 3000 K or so. Now that the light has an effective temperature of only 2.725 K.
Yes, the Earth does receive energy from the stars, but not much. The effective temperature of the night sky is about 3 Kelvin which is not much more that that of the cosmic microwave background at 2.7 Kelvin. The difference being due to the total energy of starts etc.(room temperature is ~295 kelvin)
The coldness of the night sky is interesting in itself see Olber's Paradox
The photons emitted from each star are spreading out on a sphere whose radius is growing in proportion to time --- literally, growing at the speed of light --- so the area of that sphere is growing in proportion to the square of time, so the density of photons per unit area on that sphere is shrinking as in proportion to the inverse square of time.
So, no photon is "cooling down". It's simply that the density of photons per unit of area that are hitting you, and therefore the total heat energy density per unit area that you are receiving from that star, is really, really tiny.
As others have said, the earth gets a tiny amount of heat from the stars, but it is almost nothing. But I just wanted to emphasize that it is not because the light is "cooler" - it's just because there is so little of it.
Light heats things up when it is absorbed. Think about a light bulb in a room. It's easily bright enough to see by, but it doesn't warm you up noticeably unless you get really close. This is true even though an old fashioned incandescent light bulb gives off both visible and infrared light.
A starlit night is so dim you can barely see. Just as the faraway stars are much much less bright to us than a nearby light bulb, they also give us much much less heat.
It is true that light can be "cooler" in the sense that cool things don't give off as much short-wavelength light. (Radio waves have long wavelengths, while the wavelengths for visible light are quite short, and gamma rays are the shortest of all.) But anything giving off visible light is already pretty hot.
Of course the earth gets heat from other stars. It has to. Heat is, in actuality, kinetic energy from vibrating molecules that radiate heat waves and stars radiate that energy in all directions. Since it is kinetic energy, it is movement. That movement propagates through space. Law of inertia keeps that energy radiating forever. However, unlike a definite sized piece of mass that retains its constant velocity and it's mass, thus retains it's kinetic energy directed to a point, heat waves radiate through an ever increasing radius from the source, thus reducing the actual amount of kinetic energy that reaches a destination in space. Obviously, the further that destination is away, the larger the radius of the spherical heatwave and the more the kinetic energy is dispersed, so the further something is away, the less heat the destination will receive. But it won't ever reach a temperature of absolute zero. If you removed the sun, earth would not reach absolute zero. You would have some amount of Kelvin worth of thermal energy from other stars heating the earth. Obviously not NEAR as much as what comes from the sun, but a little bit. Given the nearest star is 4 light years away, it's not hard to see how little of that heat actually reaches earth. Definitely not zero, though.
