|
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?
|
|
|
First, we'll review how light falls off with distance.
As we move away from a source of light, the energy
we measure decreases.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
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.
|