Big Bang Theory

Big bang theory suggests that the universe began from a single point about 13.82 billion years ago. What existed before this event is completely unknown to science, but there is evidence that time, space and matter had their beginnings in the big bang event.

Big bang theory suggests that the universe began from a single point about 13.82 billion years ago. What existed before this event is completely unknown to science, but there is evidence that time, space and matter had their beginnings in the big bang event.

Big bang theory suggests that the universe began from a single point about 13.82 billion years ago. What existed before this event is completely unknown to science, but there is evidence that time, space and matter had their beginnings in the big bang event.

From 1920-1960, there was a great deal of debate over which theory better described the universe. Two major pieces of evidence support the big bang theory.

This is not the only scientific theory that attempts to explain the existence of the universe. “Steady state” theory suggests that the universe had no beginning but rather has existed forever.

Big Bang Theory

This is not the only scientific theory that attempts to explain the existence of the universe. “Steady state” theory suggests that the universe had no beginning but rather has existed forever.

From 1920-1960, there was a great deal of debate over which theory better described the universe. Two major pieces of evidence support the big bang theory.

How did this theory develop, and what is the evidence for it?

Evidence for the Big Bang TheoryThere are two major pieces of evidence for the big bang theory:

This you do have to write down.

The expansion of the universe

The background radiation

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The Expansion of the UniverseEdwin Hubble was the first to take careful measurements showing that all galaxies are moving away from us, and therefore the universe is expanding. This evidence comes from examining the light emitted from galaxies. When seen through a spectroscope, the spectral lines expected for specific elements are all “red-shifted” (shifted to the red side of the spectrum).

Edwin Hubble

Edwin Hubble was the first to take careful measurements showing that all galaxies are moving away from us, and therefore the universe is expanding. This evidence comes from examining the light emitted from galaxies. When seen through a spectroscope, the spectral lines expected for specific elements are all “red-shifted” (shifted to the red side of the spectrum).

Edwin Hubble was the first to take careful measurements showing that all galaxies are moving away from us, and therefore the universe is expanding. This evidence comes from examining the light emitted from galaxies. When seen through a spectroscope, the spectral lines expected for specific elements are all “red-shifted” (shifted to the red side of the spectrum).

The Expansion of the UniverseEdwin Hubble was the first to take careful measurements showing that all galaxies are moving away from us, and therefore the universe is expanding. This evidence comes from examining the light emitted from galaxies. When seen through a spectroscope, the spectral lines expected for specific elements are all “red-shifted” (shifted to the red side of the spectrum).

hydrogen in the sun

hydrogen in another galaxy

Continuous spectrumred blue

a b c d

a b c d

All spectral lines are shifted to the red side of the spectrum.

This is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

The Expansion of the UniverseThis is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

hydrogen in the sun

hydrogen in another galaxy

Continuous spectrumred blue

a b c d

a b c d

All spectral lines are shifted to the red side of the spectrum.

This is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

This is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

This is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

This is an example of a “doppler shift” and is easiest to explain using sound as an example. When a plane flies by, you can hear a change in the frequency of the sound it makes. This is caused because the source of the sound (the plane) is moving. As the plane approaches the sound waves get bunched up. As it moves away from you the sound waves get spread out. The same principle applies to a moving source of light.

The Expansion of the Universe

waves are “bunched up”

waves are “spread out”

A moving source

The Expansion of the UniverseHubble also found that the farther away a galaxy is from us, the more its light is red-shifted. This is known as Hubble’s Law. This means that the universe is expanding (inflating). The expansion creates more space between galaxies.

Hubble also found that the farther away a galaxy is from us, the more its light is red-shifted. This is known as Hubble’s Law. This means that the universe is expanding (inflating). The expansion creates more space between galaxies.

Hubble also found that the farther away a galaxy is from us, the more its light is red-shifted. This is known as Hubble’s Law. This means that the universe is expanding (inflating). The expansion creates more space between galaxies.

Hubble also found that the farther away a galaxy is from us, the more its light is red-shifted. This is known as Hubble’s Law. This means that the universe is expanding (inflating). The expansion creates more space between galaxies.

https://www.youtube.com/watch?v=T9lkcgu5iwM

The Background Radiation The temperature at an instant after the big bang was 1023 ºC, too hot for matter to exist. By an hour after the big bang, the universe had cooled down to only 10 000 000 ºC, allowing the formation of hydrogen and helium. Even though this occurred billions of years ago, some heat should still be detectable by radio telescopes.

Arno Penzias

Robert Wilson

The temperature at an instant after the big bang was 1023 ºC, too hot for matter to exist. By an hour after the big bang, the universe had cooled down to only 10 000 000 ºC, allowing the formation of hydrogen and helium. Even though this occurred billions of years ago, some heat should still be detectable by radio telescopes.

The temperature at an instant after the big bang was 1023 ºC, too hot for matter to exist. By an hour after the big bang, the universe had cooled down to only 10 000 000 ºC, allowing the formation of hydrogen and helium. Even though this occurred billions of years ago, some heat should still be detectable by radio telescopes.

In 1963, Penzias and Wilson discovered the cosmic microwave background radiation. The Cobe spacecraft has since mapped the background radiation. The map shows that some places in the universe were hotter than others. It is in the cooler areas that matter came together to form the first stars.

The Background RadiationIn 1963, Penzias and Wilson discovered the cosmic microwave background radiation. The Cobe spacecraft has since mapped the background radiation. The map shows that some places in the universe were hotter than others. It is in the cooler areas that matter came together to form the first stars.

In 1963, Penzias and Wilson discovered the cosmic microwave background radiation. The Cobe spacecraft has since mapped the background radiation. The map shows that some places in the universe were hotter than others. It is in the cooler areas that matter came together to form the first stars.

In 1963, Penzias and Wilson discovered the cosmic microwave background radiation. The Cobe spacecraft has since mapped the background radiation. The map shows that some places in the universe were hotter than others. It is in the cooler areas that matter came together to form the first stars.