Transcript: The apparent brightness of the Sun is a factor of 1010 or 10 billion times brighter than the brightest stars in the night sky like Vega, or Canopus, or Sirius. If we assume that the Sun and the stars are intrinsically the same type of object, that is they emit the same number of photons per second, we can use the inverse square law to say what the relative distance is to the stars and the Sun is. It must be a factor of the square-root of 1010 or 105. The stars are therefore roughly 105 or 100 thousand times further away than the Sun is from us. That’s 105 times 108 or 1013 kilometers, 10 trillion kilometers, or about a third of a parsec. Thus, this simple assumption gives us a rough estimate of the huge distance to the stars. We can compare the Sun and the stars directly through the medium of an equivalent light bulb of 100 watts. The Sun is like a 100 watt light bulb at a distance of 3 inches from your eye, very intense, don’t ever try that, whereas the brightest stars in the night sky are like 100 watt light bulbs at a distance of about 9 kilometers. That is a reading light at a distance of 5 miles. This gives a sense of the enormous range of apparent brightness between the Sun and even the nearest stars.