P16, Lesson 5 - The Beginning and Future of the Universe
CMBR, Big Bang, steady state, dark matter
Covered last lesson
CMBR, Big Bang, steady state, dark matter
CMBR, Big Bang, steady state, dark matter
CMBR, Big Bang, steady state, dark matter
P16 Lesson 5 - The beginning and future of the Universe
Answer in your book:
CMBR, Big Bang, steady state, dark matter
P16 Lesson 5 - The beginning and future of the Universe
Check your answers:
CMBR, Big Bang, steady state, dark matter
P16 Lesson 5 - The beginning and future of the Universe
Learning objectives:
Any ideas of how these 2 images are connected?
CMBR, Big Bang, steady state, dark matter
So what is the Big Bang Theory?
Not this one!
CMBR, Big Bang, steady state, dark matter
So what is happening to the Universe now?
The universe is expanding
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
Big Bang Vs. Steady State theory
Both the Big Bang theory and the Steady State theory can explain why distant galaxies are moving apart.
CMBR, Big Bang, steady state, dark matter
Learning check
In your book explain the main points of the following:
You should use the words expanding, matter and time in your explanations.
CMBR, Big Bang, steady state, dark matter
Learning check
In your book explain the main points of the following:
CMBR, Big Bang, steady state, dark matter
Can you think why people were reluctant to accept these theories?
CMBR, Big Bang, steady state, dark matter
The evidence was found.
The Universe is NOT 13,700 billion years old - the video is wrong on this!
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
Evidence for the Big Bang
CMBR, Big Bang, steady state, dark matter
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
CMBR, Big Bang, steady state, dark matter
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
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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
CMBR, Big Bang, steady state, dark matter
We know its there but we can’t see it.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
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?
New telescope and technologies will help improve our understanding of the Universe and also create more questions for scientists to investigate.
CMBR, Big Bang, steady state, dark matter
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.
CMBR, Big Bang, steady state, dark matter
Not in the spec but………..
CMBR, Big Bang, steady state, dark matter
Check your notes
CMBR, Big Bang, steady state, dark matter
Logos / symbols
CMBR, Big Bang, steady state, dark matter