work work
Posted: 29 May 2012, 15:46
this is what i imagine Pat does when he's not trying to break his bike in half sprinting on the track.
http://vimeo.com/41434123
http://vimeo.com/41434123
As the video states, a commonly used "standard candle" is a Cepheid variable star. These stars pulsate regularly, and the relationship between the frequency of the pulsation and the luminoscity of these stars is generally well known. So you simply have to find a Cepheid variable star, observe its pulsation frequency, from which you can look up its known luminoscity, and from there, you calculate the distance by the loss of brightness at your observation point. As the inverse square law for brightness states, when the distance from a light source doubles, its brightness is reduced by a factor of four. Since the only unknown is the distance, you put all the other inputs into the equation, and voila: the distance is now known!How do they know which stars are 'standard candles'?