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Traveling in a flight from say India to USA

If I have to travel from India to the USA, I take flight. The flight flies and keeps traveling towards USA for about say 17 hours. Why does it kepps travelling? If it flies and stays still for the hours we assume USA to be behind India time, will it land there and reach USA? If no why?

United (States) Parcel Service.


Asked Ashwini Joshi

Questions waiting to be answered

Pranav Asked:

What are LED lamps and what is there advantage over other lamps?

Superconductors are those substances that conduct  electricity without any resistance, so why cant we use them in transmitting electricity?


Abdul Najeeb asked

i want to know more about Loop quantum gravity and tz implications on gravity, time, space and how will it change our perspective on big bang???????


Anju SV asked:

The magnets of earphones are of opposite polarities at left and right ears.why?

Abhijith Asked

Why do we see the same face of moon always?


Noel asked:

what is big bang?had it really happened?if it did,where is the proof?is it correct to say that earth and other celestial bodies were formed of this process?

Adarsh Asked:

Why does masses attract each other even though they are separated by even vacuum ?


why does the earth’s magnetic field flip?


Anuja M Bose asked

Is it possible to travel back in time using a time machine and interact with the people who lived in that period?

Vyshakhan asked

1.Is there any body on this universe known to man which is purely frictionless?
2.Is it true that light travels in the same(relative to us) speed even if we are going away from or towards it?Is this proved by experiments and is this phenomena the basis for time travel?

Gokul R Pillaiasked

Sir, I have learnt that the black hole finally opens into a white hole. If it is so, then how much distance would the objects attracted by the black hole travel, before they come out through the white hole?

A Physics Problem from Projectile Motion and Laws of Motion

A fish launches himself from a 6 cm cannon straight up in the sir. When he leaves the cannon he is traveling at 6.5 m/s. assume constant acc while in the cannon.
~What acceleration did the cannon apply to the fish?
~How long was he in the cannon?
~Once the fish is flying upwards, what is his acceleration?
~once he left the cannon, how high did he travel in the air?

The fish can hold his breath for 1.2 s out of water. Assuming that while in the cannon the fish is underwater  and once launched he is immediately in the air
~How long until he splashes back down into the water?
~What was the fish’s velocity  when he splashed back into the water?


Time Travel

Abhirami asks:

Suppose there are two brothers who are twins. One of them travels in space by orbiting earth  at a very high speed for a few years, and the other one stays on earth.When the person who had travelled in space comes back to earth, he would be looking much younger than his twin brother. Why is it so?

Time Travel, Relativity

I’ve just watched “Faster than the speed of light” programme on ITV. There is one assumption that these people always have that I have never understood. Why does travelling faster than the speed of light have to mean “time travel”??. The only reasoning i ever hear is that “You would arrive before you left”. This just doesn’t make sense to me. Why is light any different to sound? In theory, you can make a sound then travel faster than the speed of sound to hear your own voice in another location.
If they mean Einstein’s theory about time slowing down as you reach the speed of light, why not say that? Why state that “it’s impossible to go faster because you “would arrive before you departed”? Do you know what I mean??



According to Einstein’s assumptions in the theory of relativity, the velocity of light in vacuum is a constant and no particle can travel faster than light. The theory of relativity is based on this central concept. So, if we imagine to travel faster than light, time will reverse (As per theoretical results) and we may go back in time. That is why travel with or above the speed of light is referred to as “Time Travel”.

Light is an electromagnetic wave and is different from sound as it is a mechanical wave which requires a medium to travel. Sound cannot travel through vacuum.

If neutrino travels faster than light?

If neutrinos travel at the speed of light through a vacuum, and rarely interact with matter, how fast do they travel through the nucleus of an atom?

(David Tate asked)

What is twin paradox?

TWIN PARADOX is a paradoxical situation coming in while explaining the theory of relativity. “Time dilation” is one of the important consequences of relativity. It says that if a body is moving with relativistic speeds, time will dialate for it. That is, a duration of 1 second for him will be more than that for a person at rest or moving at ordinary speeds.

The relativistic time is given by the equation,

timedilation.gif (113×68)

Twin Paradox - Relativity

So, if we imagine twin brothers, one at rest at earth and other going on a relativistic interstellar trip (certainly he has to go out of solar system as the velocity of light is very much more than escape velocity of solar system, and further, he will reach the sun in just 8 minutes if traveled with the speed of light)

Let us take that his speed is 0.9 times the speed of light in vacuum. Then 1 second for him is equal to 27 s (approximately) for his brother on earth. So, if he returns after one year of space programme, he will be older by 1 year, but his brother who was at home will be older by 27 years or more; if alive.

This is the TWIN Paradox.


You are welcome to think of the possibilities of a relativistic travel and the related issues here.

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