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?

100 billion!

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.

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

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 Applet Youtube animation

• If a star is emitting light but not moving, the light looks the same in all directions

The Doppler Effect

• 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

The Doppler EffectBLUESHIFT• 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

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!

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)

The Galaxies stay the same size but are moving further

and further apart

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.

Cosmic Microwave Background (CMB)

High resolution image of the CMB taken from the WMAP satelliteWhile there are clumps, it is mostly uniform in all directions

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!

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.