Question

Explain the concepts of "speed of light" and "light year." How are these concepts related to the idea that astronomers can "see into the past?" Describe your cosmic address. Combine this understanding , along with what you know about the speed of light and the distances between objects in the universe, in a discussion of what you feel is the future of manned space travel.

Answer 1

Speed of light: It is the distance that light covers in 1 second. Speed of light depends on the medium in which it travels and is fastest in vacuum which equals
`3* 10^(8)m/s`. Generally the medium that has a higher refractive index the light will have slower speed in that medium.

Light year: It is a unit of measurement of large distances and it is a measure of the distance covered by light in 1 earth year. It equals
`9.5* 10^(12)meters`

If we know that any distant object is a few billion light years away and if we are able to predict that the age of the object is a few million years then if we see the light from such an object since the light reaches us after the death of the object since it had lesser life that the time it took the light to reach us we can see that we are looking in the past since when we are looking at the object it has long been dead thus in mere words we can say we are looking at past.

Seeing in the past also means to deduce information about the early stages of the cosmos. There are various theories that enable use to theoretically predict the nature of early universe and is backed by a sound set of experimental observations.

Since the astronomical distances are very large and require very large amounts of time to be completed these time spans are larger than the time in which an average human being can survive. Thus we can say that manned space flight shall be limited to interplanetary travel but not inter-stellar travel.