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How Far, How Powerful?
Getting from here to there
A detector records a gamma-ray
burst. We measure the amount of energy that falls on this detector near Earth.
How powerful was the event that we measure? |
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First, we'll review how light
falls off with distance. As we move away from a source of light, the energy
we measure decreases. |
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Next, we'll review Hubble's
Law and the expansion of the universe. The further an object is from Earth,
the faster it is moving away. |
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We'll then see how fast a
gamma-ray burst is moving away from us by measuring the Doppler shift of
lines in its spectrum. From this, we'll find its distance from the Earth.
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Knowing the distance to the
gamma-ray burst, the energy we measured, and the rate at which the universe
is expanding, we'll find the power emitted in the event. |
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