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Chapter 18: Chapter 18: Cosmology. WHAT DO YOU THINK? What does the Universe include? Did the Universe have a beginning? Is the Universe expanding, fixed.

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Presentation on theme: "Chapter 18: Chapter 18: Cosmology. WHAT DO YOU THINK? What does the Universe include? Did the Universe have a beginning? Is the Universe expanding, fixed."— Presentation transcript:

1 Chapter 18: Chapter 18: Cosmology

2 WHAT DO YOU THINK? What does the Universe include? Did the Universe have a beginning? Is the Universe expanding, fixed in size, or contracting? Will the Universe last forever?

3 You will discover… Cosmology, which seeks to explain how the Universe began, how it evolves, and its fate. The best theory we have for the evolution of the Universe – the Big Bang. How astronomers explain the overall structure of the Universe. Our understanding of the fate of the Universe.

4 In the Beginning – the Big Bang The Universe began 13.7 billion years ago with an event called the Big Bang. The Universe began 13.7 billion years ago with an event called the Big Bang. All of space-time, matter, and energy were created at the Big Bang. All of space-time, matter, and energy were created at the Big Bang. The left-over energy from the Big Bang can be detected today as the Cosmic Microwave Background Radiation. The left-over energy from the Big Bang can be detected today as the Cosmic Microwave Background Radiation. The temperature of this radiation is only a few degrees above absolute zero. The temperature of this radiation is only a few degrees above absolute zero.

5 The Beginning – The Big Bang

6 In Search of The Earliest Photons Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001

7 WMAPs Baby Picture of the Universe – Cosmic Microwave Background Radiation

8 The Universe is Expanding The Redshift of Superclusters shows us that the Universe is expanding. This Redshift is called the Cosmological Redshift, because it is caused by the expansion of space. The Redshift of Superclusters shows us that the Universe is expanding. This Redshift is called the Cosmological Redshift, because it is caused by the expansion of space. The farther away a galaxy is from us, the faster it moves away from us. The farther away a galaxy is from us, the faster it moves away from us.

9 The Expansion of the Universe – Cosmological Redshift Space itself is expanding.

10 Expanding Cake Analogy Just as all the chocolate chips move apart as the cake rises, all the superclusters of galaxies move away from each other as the space of the Universe expands.

11 The Observable Universe The cosmic light horizon today is about 13.7 billion light-years away in all directions.

12 HST – Galaxies >13 Billion LY Away This HST Ultra Deep Field Telescope image shows some of the most distant galaxies we have seen.

13 Early Universe Temperature Variations Tiny temperature fluctuations in the Cosmic Microwave Background Radiation are related to the large-scale structure of the Universe today, indicating where Superclusters and voids grew.

14 The First Stars – much larger than the Sun – with much shorter lives The burst of star formation that occurred within a few hundred million years after the Big Bang.

15 Proto-Galaxy Formation Hubble and Keck telescope images of two groups of stars that are believed to be proto-galaxies, from which bigger galaxies grew

16 Creation of Spiral and Elliptical Galaxies A galaxy begins as a huge cloud of primordial gas that collapses gravitationally. If the rate of star formation was low, then a spiral galaxy formed. If the rate of star formation was high, then an elliptical galaxy formed.

17 The Fate of the Universe The fate of the Universe depends on the shape of space-time. The fate of the Universe depends on the shape of space-time. The shape of space-time is determined by how much total matter and energy there is in the Universe. The shape of space-time is determined by how much total matter and energy there is in the Universe. Space-time could have one of three shapes: Space-time could have one of three shapes: Sphere = positive curvature = closed. Sphere = positive curvature = closed. Our floor = no curvature = flat. Our floor = no curvature = flat. Saddle = negative curvature = open. Saddle = negative curvature = open.

18 Possible Shapes of Space-time, and the Fate of the Universe Closed – Universe would collapse. Closed – Universe would collapse. Flat – Universe could slowly expand forever. Flat – Universe could slowly expand forever. Open – Universe would expand forever. Open – Universe would expand forever.

19 Cosmic Microwave Background indicates that Space- time is Flat – Universe could slowly expand forever

20 BUT – dimmer distant Supernovae mean the expansion of the Universe is speeding up.

21 100 billion years from now the Universe will appear frozen in time as we look out into space. Only the light from the Local Group of galaxies will remain visible, if anyone is still around to see it.

22 Expansion of the Universe is speeding up Very distant Type 1a Supernovae are not as bright as they should be. Very distant Type 1a Supernovae are not as bright as they should be. This means the expansion of the Universe is speeding up instead of slowing down or staying the same. This means the expansion of the Universe is speeding up instead of slowing down or staying the same. There is something really weird called Dark Energy (not the same as Dark Matter) that is causing this acceleration. There is something really weird called Dark Energy (not the same as Dark Matter) that is causing this acceleration. Dark Energy acts like anti-gravity, pushing the Universe apart. Dark Energy acts like anti-gravity, pushing the Universe apart. We do not know what this Dark Energy is, but it makes up 73% of the total energy/matter of the Universe. We do not know what this Dark Energy is, but it makes up 73% of the total energy/matter of the Universe.

23 Composition of the Universe Suppose all the matter and energy in the Universe is $100 in your wallet or purse. Suppose all the matter and energy in the Universe is $100 in your wallet or purse. $73 would be Dark Energy – the mysterious energy thats pushing the Universe apart faster and faster. $73 would be Dark Energy – the mysterious energy thats pushing the Universe apart faster and faster. $23 would be Dark Matter – matter that doesnt give off any kind of radiation, so we cant see it – but it does have gravity. $23 would be Dark Matter – matter that doesnt give off any kind of radiation, so we cant see it – but it does have gravity. So out of your Universe of $100, $96 represents Dark Energy and Dark Matter that have yet to be identified. So out of your Universe of $100, $96 represents Dark Energy and Dark Matter that have yet to be identified. Only $4 would be visible matter – the regular stuff we can see, like stars, gas clouds, and dust – the same stuff were made of. Only $4 would be visible matter – the regular stuff we can see, like stars, gas clouds, and dust – the same stuff were made of. Of the visible matter ($4), only one-tenth of it shines as stars. Thats 40 cents out of your total $100. The rest of the visible matter is gas clouds and dust. Of the visible matter ($4), only one-tenth of it shines as stars. Thats 40 cents out of your total $100. The rest of the visible matter is gas clouds and dust.

24 Composition of the Universe

25 WHAT DID YOU THINK? What does the Universe include? It is all the matter, energy, and space-time that will ever be detectable from the Earth or that will ever affect us. Did the Universe have a beginning? Yes, it occurred about 13.7 billion years ago in an event called the Big Bang. Is the Universe expanding, fixed in size, or contracting? The Universe is expanding, faster and faster. Will the Universe last forever? Current observations support the belief that it will last (expand) forever.


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