Physics 2.6 The Universe

What is used to split light into its different wavelengths?

A diffraction grating

What can line emission spectra identify?

Different elements

How did scientists identify the chemical composition of stars?

Observe the light they emitted through a spectroscope and compare the line absorption spectra with the spectra of known elements

What is red-shift?

An observed increase in the wavelength of light caused by the source moving away from the observer

Who observed spectra from distant galaxies to demonstrate red shift?

Sir Edwin Hubble

What two things can be said about the motion and wavelength of emitted light from a galaxy

the further away it is?

What does red-shift provide evidence for?

Provides evidence that the universe is expanding. Supports the Big Bang theory

What does the Big Bang theory suggest?

The entire universe started from a very small

Compare the observed red-shift of two galaxies

one further away than the other.

What did scientists observe to provide evidence that the universe is expanding at an ever faster rate?

They observed supernovae

Prior to observations of supernovae

what was believed about the rate of expansion of the universe and why?

What does CMBR stand for?

Cosmic Microwave Background Radiation

What does CMBR provide further evidence for?

The Big Bang Theory. It is believed that CMBR originates from radiation produced in the Big Bang

How does the existence of CMBR support the expansion of the universe?

It is thought that gamma radiation was released in the Big Bang. The expansion of the universe has stretched this radiation