1. Absorption lines of a galaxy shift toward the blue end of the spectrum when it moves toward Earth. The lines shift to the red end of the spectrum when a galaxy moves away from Earth.

2. Hubble’s Law
How do astronomers know that the universe is expanding?

3. Hubble’s Law
red shift—

4. Hubble’s Law
Hubble’s Law is -

5. The Big Bang Theory
What is the big bang theory, and what evidence supports it?

6. The Big Bang Theory
The big bang theory states that –

7. The first stars and galaxies formed –
The Big Bang Theory
Big bang occurred 13.7 billion years ago.
The universe began –
The first stars and galaxies formed –
The solar system, and Earth, formed about –
First stars and galaxies formed 200 million years after big bang.
Solar system formed 4.6 billion years ago.
Earth today

8. Continued Expansion
How can dark matter be detected?

9. Continued Expansion
Dark matter is –

10. According to Hubble’s Law,
Assessment Questions
According to Hubble’s Law,
the apparent wavelength of light is dependent on relative motion compared to the observer.
the amount of matter in a large region of the universe is constant over long periods of time.
the age of a star is proportional to the red shift of its spectrum.
galaxies are moving away from Earth at speeds proportional to their distance from Earth.

11. How is dark matter in the universe detected?
Assessment Questions
How is dark matter in the universe detected?
direct observation
its effect on electromagnetic interactions
its gravitational effects on matter
very faint background radiation in the universe

12. Assessment Questions
Based on the size of the universe and its rate of expansion, the big bang is calculated to have occurred between 13 and 14 billion years ago. True False