2. We orbit The Sun –which is just one of 100 billion stars that make up our galaxy, The Milky Way But how many galaxies are in the Universe?

3. Lesson Objectives. Everyone will be able to … Identify evidence that shows how the Universe is changing. Most of you will be able to … Describe the main theory of how the Universe was formed. Some of you will be able to … Consider the possible fate of the Universe.

4. THE UNIVERSE IS MASSIVE! REALLY REALLY MASSIVE! Humans can’t even begin to understand how massive it is… If our whole Solar System was a 2p coin, the Sun would be a speck of dust. The next nearest star, Proxima Centauri, would be a speck of dust two football pitches away. Powers of 10 Java Applet Powers of 10 video

5. The Doppler Effect In the EM spectrum, there is high frequency light (violet) and low frequency light (red). If the object emitting this light is moving away or towards you, the light can be shifted into other colours Doppler Effect Java AppletYoutube animation Doppler Effect Java AppletYoutube animation

6. If a star is emitting light but not moving, the light looks the same in all directions The Doppler Effect

7. But if a star is moving while emitting light, the light goes bluer if its moving towards you, or redder if its moving away The Doppler Effect REDSHIFT BLUESHIFT

8. The Doppler Effect BLUESHIFT If an object is moving towards you, the wave is squished up – and becomes high frequency. Light appears to be bluer REDSHIFT If an object is moving away from you, the wave is stretched out– and becomes low frequency. Light appears to be redder

9. RED, RED Everywhere… American astronomers Edwin Hubble (1889 – 1953) and Henrietta Leavitt (1868 – 1921) spent much time observing stars known as Cepheid Variables. Also known as standard candles, these are stars that shine with a known brightness. They noticed that nearly all of the stars they could see were redshifted Everything Was flying away From us!

10. So what does this mean? If everything is flying away from us in all directions, this means the universe is expanding! If we know it is expanding, we can rewind the clock and figure out that the entire universe must once have been squashed into a single point. THE BIG BANG Naked Science: The Birth of The Solar System (Nat Geog)

11. The Galaxies stay the same size but are moving further and further apart

12. More evidence for the Big Bang In 1964 Arno Penzias and Robert Wilson were using a very sensitive radio antenna. No matter where they pointed the antenna, they got static. They eventually worked out that they were listening to left over radiation from the Big Bang.

13. Cosmic Microwave Background (CMB) High resolution image of the CMB taken from the WMAP satellite While there are clumps, it is mostly uniform in all directions

14. Problems with the Big Bang There is not enough matter (stuff) in the Universe to account for the strength of gravity in and between galaxies. So scientist came up with dark matter – it’s there but we can’t see it or detect it. It makes up 95% of the Universe!

15. So what will happen to our Universe? 1.It will keep on expanding forever. Everything will get colder, darker and further apart. 2.It will stop expanding and start contracting, collapsing back in on itself (The Big Crunch). 3.It will reach an equilibrium position and stop.