How does the Speed of Light work again?

9 Comments

• As Enigma says the doppler effect is how distance in light years can be measured. Light travels in waves, the shorter the distance an object is to the source of light (a galaxy's star) means the distance between the troughs and peaks in the waves are shorter (the higher end of the spectrum) this is called the blue shift. The further and further away an object is means the distance between the troughts and peaks are and so the the further down the spectrum the light becomes, this is called the red shift. Using telescopes they can measure the shift.
  

• Doppler shift isn't the only way they measure distance.
  
  
  
  Why not? Because of many possible factors. Doppler shift measures the speed at which the light source is moving away from (or toward) us, due to the expansion rate of the universe. However, relative motion due to other factors than universal expansion is also a possibility, so doppler shift alone can't tell us the distance (if the galaxy in question is speeding away due to galactic motion, it would seem farther away. If speeding to us, it would seem closer)
  
  
  
  Other methods are normally used as well, if possible. Cephids, gravitational lensing, and lots of other tricks are used to help bracket the distance.
  
  
  
  Currently, it's pretty widely accepted that they can get fairly close. But if you want to be accurate, we don't _really_ know. (got a fast spaceship?)
  

• One also has to keep in mind that this whole discusion also falls heavily under the General Theory of Relativity.
  
  
  
  One outcome of the theory is that the passage of time varies according to the speed at which you are travelling *relative* to some other object. Thus how we measure the age of the universe will differ in other reference frames.
  
  
  
  Objects on "the other side" of the universe typically travel 80% of the speed of light (relative to us) which therefore introduces about 0.6 time & space warping factor.
  
  
  
  Try working out if this is a real effect or some how is cancelled out.
  
  
  
  Relativity is fascinating, but it warps the brain moreso that space and time!
  

• How? With the sort of equiptment you can find in your wal-mart. A few lenses, a prism, a piece of white paper, a gas spectrometry chart, and some grade school mathematical skill.
  

• It's not "theoretically" true what the guy said about an object moving away appearing farther. Relativity says (among other things) that light is the same for all observers. Thus an object travleing at faster that light speed would outrun it's own light. The light would not travel at the objects speed + light speed if that makes sense.
  

• all i know about light is that there is two forms of light witch are the sun and man made
  

• all i know about light is that there is two forms of light witch are the sun and man made
  

• all i know about light is that there is two forms of light witch are the sun and man made
  

• well,,, there has been speculation of how old the universe has been for a long time now and despite mythical beliefs scientist ignored that the mayah once said that the universe is 14.6 billion years old and recently scientists are now more and more discovering how old it actually is. its just that the last recorded theory was 13.7 but if thats true that the universe is 14.6 billion years old and they have found something that is 13.3 away from us then that could mean that we are either closer or further away from the center of the universe! now all we have to do is find out whether or not hen we look at galaxies far away from us, if they are spireling away from us or if we are spireling away from them!it always comes down to 50/50 in science doesnt it!