In 1842 the Austrian physicist Christian Doppler described what came to be known as the Doppler shift - an example of which is the change in frequency of a police car siren as it moves towards and away from an observer standing on the pavement.
Doppler realised that light, like sound, will change its frequency depending on the relative movement of the object emitting it and the person observing it. Light frequency changes are observed as changes in colour, so a star that moves away from Earth appears redder; if it moves towards us, it appears bluer. Using a technique called spectroscopy, astronomers measure the red shift or blue shift of stars to understand their relative motion.
Image: Christian Doppler (credit: SPL)
Prof Brian Cox studies the colour of stars to understand how the Universe began.
Prof Brian Cox explains how we can understand the origins of the Universe through differing wavelengths of light emitted by stars.
Dr Francisco Diego explains how the Doppler shift can be used to work out whether stars are moving towards us or away from us.
Christian Andreas Doppler (pron.: /ˈdɒplər/) (29 November 1803 – 17 March 1853) was an Austrian mathematician and physicist.
This entry is from Wikipedia, the user-contributed encyclopedia. If you find the content in the 'About' section factually incorrect, defamatory or highly offensive you can edit this article at Wikipedia.
BBC © 2013 The BBC is not responsible for the content of external sites. Read more.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.
