Answer :
The gap between the universe's current age and the age it was at the time that light departed the galaxy is known as the lookback time. are more precise than distances when discussing very distant objects.
The measurement of distances to far-off objects is challenging due to the universe's expansion. Astronomers measure the redshift of far-off objects, including galaxies, as opposed to distance units. However, the universe has been expanding as the light traveled, and the object is now much farther away, therefore this is not the distance to the object in light years. A more away an object is, the more it will be redshifted.
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