Look back time #astronomy #lookbacktime #lookback #spaceexploration #shorts

Look-back time is the time that has passed since light from a distant object was emitted and when it was detected on Earth. It’s also known as light travel time.

Here are some things to know about look-back time:

How it works
Because light travels at a finite speed, we see objects as they were when the light was emitted, not as they are now.

How it’s calculated
Look-back time is calculated by subtracting the age of the universe when photons were emitted from the age of the universe now.

How it’s expressed
Look-back time can be expressed in years or as a percentage of the universe’s current age when the light was emitted.

How it varies
The look-back time depends on the distance of the object being observed:

Nearby objects: The look-back time is almost zero.

Supernova 1987A: The look-back time was about 170,000 years.

Very distant objects: The look-back time could be 10 billion years or more.

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