Stars constant light - what effect on earth

[botanic]

2 pretty simple questions really:<br />Gazing up at night sky I considered the particle nature of light and how the radiation from a (point) source diminishes with the square of the distance. How then can we see stars essentially constantly, despite our eyes being a pinprick lightyears from the source. Even if one photon was activating our eyes from each star every second, that makes a hell of a lot of photons as we see thousands of stars.<br />so <br />1) Are there basically photons from every star, striking every millimetre of the earth visible to the night sky, all the time?<br /><br />2) What is the warming effect of this considering that the energy of one photon is not entirely negligible?<br />Asked cosmologist George Ellis at my university this, and he dismissed the question saying the energetic input from stars was negligible. <br /><br />Some further thoughts: <br />Energy of single molecule is that dicated by wavelength and speed, and plancks constant(E=hf). Multiple wavelengths coming from multiple sources all the time (speed presumably the same for all light hitting the observer as any time), therefore probably an average energy per photon can be given.<br /> (e.g. E = average energy of photon from average star * number of stars visble to earth * rate of photons / cm^2 ).<br /><br />Probably it is easy enough to dismiss question one by invoking the wave nature of light.

 

[bobw]

Here's what I think.<br /><br />1. Yes, basically. Each star emits a finite quantity of photons/sec and we have to wait for our share of a random distribution. <br /><br />2. The full moon doesn't have much of a warming effect even though it is 70,000 times as bright as Sirius. If we are generous and assume that all 5000 visible stars are as bright then their combined warming effect is 14 times less than the moon. I agree with George.<br /><br />Welcome to Uplink<br /> <div class="Discussion_UserSignature"> </div>

 

[vogon13]

Photons per second per retinal cell in your eye would be related to magnitude. IIRC, for really dim objects, like 23 magnitude stuff, you are almost at the point of having a discernable interval between photon arrivals. At magnitudes typical for seeing stars with your eyes, (<6) the photons are a torrent.<br /><br />Consider if you will, in a star fusing hydrogen for fuel, 2 hydrogen atoms releases (IIRC) 3 or 4 Mev, photons you can see have an energy of like 2 or 3 ev. Divide it out, and every fusion zap makes a heap o photons. Stars can put out many, many photons, enough for you to see them by at enormous distances. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[newtonian]

botanic - For earth starlight produces negligible heating.<br /><br />I'm not so sure about for Pluto, however.<br /><br />The closer an object comes to absolute zero, the more significant warming from starlight becomes.<br /><br />A logical extension to your question, which is now my question:<br /><br />If an object were virtually absolute zero in temperature, what temperature would starlight produce for that object?<br /><br />BTW - there are other forms of interstellar and intergalactic heating.<br /><br />In fact, the IGM (= intergalactic medium) is incredibly hot! This is probably due to ionization from supernovae - at least in one model recently reported on in Scientific American.