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CBSE Class 9 Answered

is time travel is possible?if not why?if yes Why?    
Asked by abhinav34.9dgatl | 04 Jan, 2021, 11:49: AM
answered-by-expert Expert Answer
Time travel means , just like back and forth movement beween two locations in space travel, we should move forward and backward in time also.
 
From our experience , we are feeling only forward movement in time. But NASA's space telescopes  give us a way to look back in time.
Telescopes help us see stars and galaxies that are very far away. It takes a long time for the light from faraway galaxies to reach us.
So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.
 
Albert Einstein has proved from his theory of relativity, space and time are not absolute but relative.
But this concept can be experienced only objects are moving very near to speed of light. We don't feel this relativity phenomenon when the 
objects are moving with speed much less than speed of light. As per theory of relativity ,
when a clck is moving with speed very near to speed of light, then this clock will run slow compare to the identical clock at rest.
 
Let us assume two identical clocks are syncronized , one is kept at earth and other is kept in a rocket that moves with speed (1/10)th of speed of light.
 
If a signal is communicated to earth from rocket to represent some event in rocket and we assume this signal is received instantaneously
on earth at time say t = 10 s just after launching of rocket ( t = 0 ) , but this same event is recorded in rocket at t = 9.95 s
 
Hence though the event is seen instantaneous , we are moving back in time by 0.05 s according to the clock placed in rocket.
 
We have to keep in mind such small backward time difference is possible , only the clocks that showing the time of event moving 
with speed very near to speed of light.
 
Answered by Thiyagarajan K | 04 Jan, 2021, 12:46: PM

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