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P16, Lesson 5 - The Beginning and Future of the Universe

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Covered last lesson

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  • Print handout
  • Full dark energy video for Google classroom (6:20)
  • Start
    • Recall questions
  • Main
    • Explain and discuss the Big bang theory - video
    • Explain and discuss the Steady State theory
    • Learning check questions
    • Discuss evidence for the Big Bang (CMBR & red-shift) - video
    • Discuss the future of the Universe - link to density and annotate handout
    • Discuss dark matter and dark energy - video
  • Plenary
    • Exam questions and check notes

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P16 Lesson 5 - The beginning and future of the Universe

Answer in your book:

  • Define red-shift.
  • Explain how red-shift can tell us what is happening to the Universe.
  • Give the name of the person who discovered what is happening to the Universe.

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P16 Lesson 5 - The beginning and future of the Universe

Check your answers:

  • Define red-shift. The observed increase in wavelength of EM waves emitted by a star or galaxy due to its motion away from the observer.
  • Explain how red-shift can tell us what is happening to the Universe. Light from distant galaxies is red-shifted. This tells us the galaxies are moving away from us. Light from the most distant galaxies undergoes the greatest red-shift so they are receding fastest. This tells us the Universe is expanding.
  • Give the name of the person who discovered what is happening to the Universe. Edwin Hubble

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P16 Lesson 5 - The beginning and future of the Universe

Learning objectives:

  • Describe what the Big Bang theory of the Universe is.
  • Describe what cosmic microwave background radiation (CMBR) is and how is supports the Big Bang theory.
  • Discuss the possible options for the future of the Universe.

Any ideas of how these 2 images are connected?

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So what is the Big Bang Theory?

Not this one!

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So what is happening to the Universe now?

The universe is expanding

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The Big Bang Theory

This states that before the Big Bang there was nothing, not even time!

All space, time and matter were created in the Big Bang.

The Universe began after a rapid expansion from an extremely hot and dense region, and it is still expanding today, 13.7 billion years later.

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Is there another way this could be explained?

Steady State theory:

Many scientists disagreed with the Big Bang theory.

Can you think of a reason why?

They put forward the alternative Steady State theory. This states that galaxies are being pushed apart, and this was caused by matter entering the Universe through “white holes”, therefore keeping the overall density of the Universe the same.

In the Steady State theory the Universe has no beginning, or end, in time.

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Big Bang Vs. Steady State theory

Both the Big Bang theory and the Steady State theory can explain why distant galaxies are moving apart.

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Learning check

In your book explain the main points of the following:

  • The Big Bang theory
  • The Steady State theory.

You should use the words expanding, matter and time in your explanations.

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Learning check

In your book explain the main points of the following:

  • The Big Bang theory. The Big Bang theory states that space, time and matter were created in the big bang which happened 13.7 billion years ago. The Universe was created in a rapid expansion from an extremely hot and dense region and is still expanding today.
  • The Steady State theory. The steady State theory states that the Universe is always expanding while maintaining a constant density due to new matter entering through “white holes”. A Steady State universe has no beginning or end in time.

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Can you think why people were reluctant to accept these theories?

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The evidence was found.

The Universe is NOT 13,700 billion years old - the video is wrong on this!

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Cosmic microwave background radiation (CMBR)

Discovered by accident in 1965, the cosmic microwave background radiation (CMBR) provides evidence for the Big Bang.

CMBR was created as high-energy gamma radiation just after the Big Bang. It has been travelling through space ever since.

As the Universe has expanded its wavelength stretched and it is now microwave radiation. It has been mapped out using microwave detectors on Earth and on satellites.

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More evidence

Red-shift

Remember that light from distant galaxies is red-shifted. The wavelength of the light has moved towards the red end of the spectrum. This means the galaxies are moving away from us.

The light from the most distant galaxies undergoes the greatest amount of red-shift, so they are moving away fastest.

This fact tells us that the Universe is expanding.

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Evidence for the Big Bang

CMBR was created as high-energy gamma radiation just after the Big Bang. It has been travelling through space ever since.

As the Universe has expanded its wavelength stretched and it is now microwave radiation.

Remember that light from distant galaxies is red-shifted. The wavelength of the light has moved towards the red end of the spectrum. This means the galaxies are moving away from us.

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Evidence for the Big Bang

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The future of the Universe

What happens to the Universe in the future depends on its density.

Will the force of gravity between distant galaxies be enough to stop them moving away from each other?

That depends on the total mass of the galaxies, how much matter is between them and how much space they take up - the density of the Universe.

P6

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The future of the Universe

If the density of the Universe is less than a particular amount, it will continue to expand forever. (Big Yawn)

If the density of the Universe is more than a particular amount, it will stop expanding and go into reverse, receding back to a small point. (Big Crunch)

Annotate your handout

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Dark matter

Astronomers are faced with a confusing problem - the observable mass of the Universe is too small when compared to what it should be.

Galaxies should spin much faster if their stars were the only matter in them.

The missing mass is called dark matter. It is called this because it can’t be seen.

The nature of this dark matter will determine the fate of the Universe.

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An uncertain future

The expansion of the Universe is accelerating. Observations of supernovae in distant galaxies suggest the galaxies are accelerating away from each other.

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Remember:

Objects only accelerate if there are unbalanced forces acting on them.

If the galaxies are accelerating away from each other there must be a force bigger than the effect of gravity pushing them apart.

As the galaxies are moving this force is acting over a distance and:

Energy transferred = force x distance

But where is the energy coming from?

P8

P1

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We know its there but we can’t see it.

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Dark Energy

Scientists can’t explain why galaxies are accelerating away from each other with our current knowledge of the Universe.

One possible explanation is an unknown energy source called dark energy causing the acceleration.

The only known force acting on distant galaxies is gravity. This can’t be used to explain dark energy as it is an attractive force so acts against the expansion of the galaxies.

New telescope and technologies will help improve our understanding of the Universe and also create more questions for scientists to investigate.

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Dark Energy

Scientists can’t explain why galaxies are accelerating away from each other

The only known force acting on distant galaxies is gravity. Why can we rule this out?

  • Possible explanation is dark energy causing the acceleration.

New telescope and technologies will help improve our understanding of the Universe and also create more questions for scientists to investigate.

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Exam technique: When you are asked the difference between two things in an exam question you must discuss both things in your answer in order to gain full marks.

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Not in the spec but………..

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Check your notes

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Logos / symbols

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