Spectral-Shift by hedongchenchen


 Stars give off EM Waves in all directions at
  the speed of light.
 Notice: the wavelengths on the left and right
  of this start are relatively the same. Let’s say
  the peak wavelength for this star is the
  wavelength for GREEN.
   http://youtu.be/FhfnqboacV0
   http://www.colorado.edu/physics/2000/applets/doppler2.html
   http://www.colorado.edu/physics/2000/applets/doppler.html
   http://www.astro.ubc.ca/~scharein/a311/Sim.html#Doppler
   http://people.westminstercollege.edu/faculty/ccline/elements/elements1.html
 When a star is in motion, it can catch up to the waves
    on one side while moving away from the waves on
    the other side.
   Notice: The wavelengths on the left of this star are
    longer and the wavelengths on the right are shorter
   What color is associated with each type of
   Color with a long wavelength: red
   Color with a short wavelength: blue
   The star is moving away from A and toward B. So
    even though it is actually shining with a green light,
    A will see a redder light and B will see bluer light.
 The faster the star is moving, the greater the
  spectral shift.
Check Yourself:
 How do you determine the direction a star is
 Redder is moving away, blue is moving toward
 How do you determine how fast a star is moving?
 The more the shift the faster
 The next page will explain how direction and speed
  of a star will tell you distance!
How do we know how far away
stars are?
 The universe is expanding

 In general, all celestial bodies (objects in
  space) move away from each other at an
  equal rate.
 Here are 4 galaxies

 If they move away from each other at an
  equal rate, we should expect each one to be
  equally far away from each other after a
  certain amount of time

 Even though they are all         far away from
  each other, The first one is much further away
  from the last one… like this far
 This means that objects that are further away
  from us move away faster than objects that
  are close to us.

 Objects further away from us will have a
  greater red shift than objects closer to us.
Check yourself:
 Do you think the star in this image is close by
  in our universe or far away?
 Far away

violet                                         red

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