- last post: 01.01.0001 12:00 AM PDT
Posted by: Recon Number 54
Some radars (and lasers) work using the principle of the Doppler effect. EMR (radar and light) have a constant speed, they are however effected by the speed of other objects.
Just like a police siren (or a horn) will change pitch as a car approaches and then recedes from an observer, EMR encounters the same "pitch" (frequency) change. By measuring the amount that the frequency has changed, a angular velocity can be calculated.
The same principal can be used to calculate how far away stars are from the earth, because stars that are further away are moving faster from the earth, therefore the electromagnetic radiation emmitted from them is "stretched" causing the electromagnetic radiation to appear as though it is of a lower wavelength than it actually is, hence "Red Shift".
Sorry, I've gone off topic....