The Spectrum

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Slide 67

Slide 68

To sum up that animation (again)

Because light waves travel only at a fixed speed, a light-emitting object like a star will be “redder” if it moves away from us and “bluer” if it moves towards us, meaning that the pattern of spectral lines will shift to the red or blue but maintaining their relative positions to each other

And you find it in classic rock!

Slide 69

Armand Hippolyte Louis Fizeau (September 23, 1819 – September 18, 1896

First predicted red shift shortly after Doppler discovered it

Also showed that two telescopes could be combined, forming a single, much larger aperture

Interferometry

Slide 70

Red Shift

Slide 71

Huggins had noted this in 1868

Doppler widening

Slide 72

Spin

Astronomers can tell if a distant galaxy is spinning and how fast

The light on one edge is blue (moving towards us) and the other edge is red (moving away)

I p-shopped this up to make a point 

Slide 73

What was that about a bad neighborhood?

In the 1920s Edwin Hubble examined the spectra of stars of many galaxies

He did his work at the Wilson Observatory

Here he is with his pipe

You can almost hear his British accent

(He was born in Marshfield, Missouri)

Slide 74

An Expanding Universe

Hubble discovered that the more distant a galaxy was from us, the faster it was moving away

Can only be explained by an expanding Universe

A lecture for another day