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What would a stationary observer see if you travelled close the speed of light?


Katalos1997

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Lets say a spaceship travels at very very very close to lightspeed from point A. to point B.. And they need 10 seconds for that journey

Now because they were so fast, time moved differently, and for the rest of us 1 month went by.

Here my question:
For themselves, they moved about 10lightseconds in 10 seconds, but for everyone else, wouldnt they have moved incredibly slow, needing 10 months for that journey?

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31 minutes ago, Katalos1997 said:

Lets say a spaceship travels at very very very close to lightspeed from point A. to point B.. And they need 10 seconds for that journey

Now because they were so fast, time moved differently, and for the rest of us 1 month went by.

Here my question:
For themselves, they moved about 10lightseconds in 10 seconds, but for everyone else, wouldnt they have moved incredibly slow, needing 10 months for that journey?

You need to be very clear about which frame of reference you are measuring times and distances in. For example, how far apart are A and B as measured by the stationary observers? 

The spaceship crew would measure the distance travelled as very short (approximately 10 light seconds, as you say).

We (the "stationary" observer) would see the distance as much longer. 1 light month, based on the fact it took them one month to travel the distance (in our frame of reference).

You said they take 1 month for the journey (as measured in our frame of reference) so why would it take 10 months?

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34 minutes ago, Katalos1997 said:

Lets say a spaceship travels at very very very close to lightspeed from point A. to point B.. And they need 10 seconds for that journey

Now because they were so fast, time moved differently, and for the rest of us 1 month went by.

Here my question:
For themselves, they moved about 10lightseconds in 10 seconds, but for everyone else, wouldnt they have moved incredibly slow, needing 10 months for that journey?

Poorly worded, but I think enough clues are there to work out what you have in mind. Let me know if I get this wrong.

In some frame, points A and B are stationary objects and nearly a light-month apart.  "The rest of us" are stationary in that frame.

For "themselves", we're referring to the people in the ship.  The don't move at all in their own frame.  The object B comes at them from nearly 10 light seconds away and takes 10 seconds to get to them.

Now as for your question: No, to everyone else, they're moving at nearly light speed, taking a month to go nearly a light month. To themselves, by definition, they're not moving at all, which is slower than 'incredibly slowly'.  It is A and B that takes a 10 second journey in that frame of reference, each moving at nearly light speed.

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51 minutes ago, Strange said:

You need to be very clear about which frame of reference you are measuring times and distances in. For example, how far apart are A and B as measured by the stationary observers? 

The spaceship crew would measure the distance travelled as very short (approximately 10 light seconds, as you say).

We (the "stationary" observer) would see the distance as much longer. 1 light month, based on the fact it took them one month to travel the distance (in our frame of reference).

You said they take 1 month for the journey (as measured in our frame of reference) so why would it take 10 months?

Ah so the distance would change, if they stopped the journey, they would have moved 1 lightmonth in only 10 seconds, eventhough they only moved close the speed of light.

43 minutes ago, Halc said:

Poorly worded, but I think enough clues are there to work out what you have in mind. Let me know if I get this wrong.

In some frame, points A and B are stationary objects and nearly a light-month apart.  "The rest of us" are stationary in that frame.

For "themselves", we're referring to the people in the ship.  The don't move at all in their own frame.  The object B comes at them from nearly 10 light seconds away and takes 10 seconds to get to them.

Now as for your question: No, to everyone else, they're moving at nearly light speed, taking a month to go nearly a light month. To themselves, by definition, they're not moving at all, which is slower than 'incredibly slowly'.  It is A and B that takes a 10 second journey in that frame of reference, each moving at nearly light speed.

Yes poorly worded, sorry.

Question is already answered.

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24 minutes ago, Katalos1997 said:

Ah so the distance would change, if they stopped the journey, they would have moved 1 lightmonth in only 10 seconds, eventhough they only moved close the speed of light.

Yes poorly worded, sorry.

Question is already answered.

They only moved in the frame in which the distance between A and B was 1 light month. As measured from that frame is took just a tad over 10 month for them to cross the distance while their clock ran slow and only accumulates 10 sec.

From their perspective, A and B are moving at nearly light speed relative to them and thus the distance between them is only 10 light sec. Thus it only takes a little over 10 sec from the moment A is next to them until B reaches them.  If then then change velocity to match that of B, the distance between A and B will expand to 1 light month.

A couple of other things to take into consideration:

If we put a clock at A and B and synchronize them to each other in the rest frame of A and B, then in that frame,  they will leave A when both clocks read the same time, and arrive at B when both clocks read 1 month later.

However if we consider events by the spaceship's frame:

The occupants will agree that the clock at A reads the same time when they leave A as A does, however, they will not say the same for the clock at B. They will instead say that the clock at B already reads only about 38 microseconds short of 1 month later than What A's clock reads.

During the 10 sec the ship measures until it and B are next to each other, the clocks at A and B will run slow compared to the ship's clock and advance about 38 microseconds. 

At the moment B reaches the ship, the clock at B will read just that tad over 1 month past the time A's clock read when the ship left A.  The clock at A will have accumulated just 38 microseconds.

If the ship were to now match speeds with B and A( while remaining next to B),  not only would the distance between A and B increase to 1 light month, but the clock at A would rapidly advance ( according to the ship) until it matched the reading of the clock at B.

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1 hour ago, Katalos1997 said:

Ah so the distance would change, if they stopped the journey, they would have moved 1 lightmonth in only 10 seconds, eventhough they only moved close the speed of light.

You are mixing up frames of reference.

They travelled 1 light-month in 1 month.

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