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The Expanding Universe  When light or sound moves toward or away from an observer, its frequency/wavelength changes (Known as Doppler effect)  Can be.

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Presentation on theme: "The Expanding Universe  When light or sound moves toward or away from an observer, its frequency/wavelength changes (Known as Doppler effect)  Can be."— Presentation transcript:

1 The Expanding Universe  When light or sound moves toward or away from an observer, its frequency/wavelength changes (Known as Doppler effect)  Can be used to see how fast stars/galaxies are moving towards or away from us (when moving towards the lines in the spectrum are shorter/blue wavelengths, when moving away the lines are longer/red wavelengths)

2 Hubble’s Law  The larger the shift, the greater is the speed of this movement  In 1929 Hubble announced that light from most galaxies is red shifting  Nearly all the galaxies are getting farther away from Earth  Also found that more distant galaxies have greater red shifts (means the distant galaxies are moving away faster than the closer galaxies)

3 Hubble’s Law  This relationship called Hubble’s Law, says that the speed at which a galaxy is moving away is proportional to its distance from us  The most distant galaxies are moving away at around the speed of light!!!  The observed red shift in the spectra of galaxies shows that the universe is expanding in all directions

4 The Big Bang Theory  Astronomers theorize that the universe came into being at a single moment, in an event called the big bang  According to this theory all the matter/energy of the universe were at one time concentrated at a single point  It also states that the universe began in an instant, billions of years ago, in an enormous explosion

5 The Big Bang Theory  After the big bang the universe expanded quickly and cooled down  After a few thousand years of expansion, the universe was cool enough for atoms to form  Gravity pulled atoms together into gas clouds that evolved into stars in young galaxies  Our solar system formed 4.6 billion years ago when the universe was about two thirds its present size

6 The Big Bang Theory  Evidence for the Theory: -In 1965 2 scientist noticed a signal on their radio telescope, they realized they were detecting a faint distant glow in every direction (called cosmic microwave background radiation)  This radiation was produced during the big bang and is still traveling through space

7 The Big Bang Theory  The existence of cosmic microwave background radiation and the red shift in the spectra of distant galaxies strongly support the big bang theory  It offers the best current scientific explanation of the expansion of the observable universe  Variations of this theory continue to be proposed

8 The Big Bang Theory  Age of the Universe: -Since astronomers know how fast the universe is expanding, they can infer how long it has been expanding  If you traveled backward in time, all the matter in the universe would be at a starting point 13-14 billion years ago  Astronomers estimate that the universe is 13.7 billion years old

9 Continued Expansion  To have a gravitational force strong enough to reverse the expansion, there must be sufficient mass in the universe  If there is less than this amount of mass, the universe will continue to expand  The mass that glows like stars is easy to measure because it can be seen, however most of the mass in the universe can’t be seen by astronomers

10 Continued Expansion  Dark matter is matter that does not give off radiation (Light)  Dark matter cannot be seen directly, but its presence can be directed by observing its gravitational effects on visible matter  Galaxies may contain as much as 10 times more dark matter than visible matter

11 Continued Expansion  Without this much, there would not be enough gravitational force to keep groups of galaxies from flying apart  Astronomers don’t know what it is made out of or how it is distributed through the universe  Most of the mass in the universe is composed of dark matter

12 Continued Expansion  Astronomers have discovered recently that the universe is expanding at a faster rate  Galaxies are moving apart much faster than expected  A mysterious force called dark energy is theorized to be causing the rate of expansion to increase  It’s likely the universe will expand forever


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