The expanding Universe

What did Edwin Hubble discover?

A Cepheid variable star in the Andromeda nebula that had a period of 31 days, which meant that it should be very bright.

What did Hubble's results form?

A straight line on a graph showing that recessional velocity is proportional to the distance from Earth.

Who showed that some nebulae were actually galaxies?

Edwin Hubble.

How did the star appear?

Faint and when Hubble calculated how distant it was he found that it must be at least 1 million ly away, well outside of our galaxy.

What did the discovery provide evidence for?

The Big Bang Theory, which is believed by many scientists.

What does the redshift indicate?

Almost all galaxies are moving away from us.

What did Hubble study?

Cepheid variable stars in many distant galaxies and found that the further away the galaxy is the faster it is moving away from us.

Speed of recession (km/s)=

Hubble constant(km/s)/Mpc) x distance (Mpc)

What is the constant of proportionality called?

The Hubble constant.

What else did this lead to the realisation of?

The Universe was far bigger than anyone had imagined.

What does the Big Bang Theory state?

The entire Universe appeared at a single point about 14 thousand million years ago and has been expanding ever since.

What is found when the spectrum of light from a galaxy is compared to the spectra produced by stars in our own galaxy?

The spectrum is shifted, almost always towards the red end of the spectrum.