Because cosmic distances are so vast, astronomers use light-years as their unit of distance. One light-year is defined as . The nearest star is a little more than light-years away from us. When we see light from a galaxy 2 million light-years away, it has taken to reach us. Light from the Sun takes to reach us.

Because cosmic disaster are so vast, astronomers use light-years as their unit of distance. One light-year is defined as the distance a beam of light travels in one year. The nearest star is a little more than 4.37 light-years away from us. When we see light from a galaxy 2 million light-years away, it has taken 2 million Earth years to reach us. Light from the Sun takes approximately 8.4269 minutes to reach us

Explanation:

i) One light-year is defined as the distance a light beam travels in a time of one Earth year. One light year is equivalent to 6 × 10¹² miles or 9.7 × 10¹² km

ii) The distance to the nearest star =  4.37 light-years

iii) When a star located in a galaxy that is 2.3 million light years away is seen, it has taken 2.3 million light years to reach us

iv) The distance of the Sun to the Earth = 151.58 million kilometers

The speed of light, c = 299792.458 km/s

The time it will take light to reach us from the Sun, 't', is given as follows;

t = 151.58 × 10⁶ km/(299792.458 km/s) ≈ 8.4269 minutes.

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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