A physics: speed of light vs outside observer question.?

Question

Okay, you have two little spaceships, both start out at the same speed, 99.9 the speed of light. They look across at each other and see that they are traveling the same speed. Then, one of the ships accelerates to twice it's original speed.

If an observer sees the two spaceships fly past, what will he see? If I understand it correctly, neither ship can actually go faster than the speed of light, they would instead be warping time. So how does that affect an outside observer who can't see the time effect?

Before someone says that the spaceship cannot double its speed, I beg to differ. To the occupants inside the spaceship, they could acclerate/decelerate because they wouldn't think they were at 99.9 the speed of light, they would only appear to be doing so to an outside observer.

I seem to have missed out an important point. The two spaceships are initially traveling at the same speed. They pass an observer who sees them traveling at 99.9 the speed of light (to the spaceships, the observer is going at 99.9 speed).
One of the spaceships accelerates and doubles the speed (relative to the other spaceship). Both ships then whizz by another observer traveling the same speed as the first observer. What does the observer see?

Answer 1

It doesn't matter if the person inside the ship isn't aware of his speed, he cannot double his speed if he started out going 99.9 times the speed of light. Period.

So, your question doesn't have any relevance.

Also, it is the observer from the outside that sees the slowing of time for the people in the ship. The people in the ship aren't aware of any slowing of time, because everything including their motion inside the ship, and brain functions slow down as well. They have no idea that their time is slowed.

But, you are correct: neither ship can go faster than the speed of light, and each ship will not see the other ship going faster than light either. It can't even look like something is going faster, even if its speedometer shows a speed slower than light.

Answer 2

I understand what you are trying to say, but there is a critical flaw in what you are proposing.......

"One of the spaceships accelerates and doubles the speed (relative to the other spaceship)."
--If both space shis start out at the same speed relative to a given outside observer....then to the people within the spaceships, the other space ship (and they themselves) are not moving at all, v = 0. If you double zero, is still zero. If something that is not moving accelerates to twice its speed, it is still not moving.

However, if you rephrased they to mean that one spaceship double's its speed relative to the previously mentioned outside observer, then this would not be possible at all. In any frame of reference, faster than light travel is impossible.

Lets rephrase the question again to get another answer....
Say that an outside observer measure the two spaceship's speed to be 99.9% the speed of light....then one space ship accelerates until in the other spaceship's reference frame, it is traveling at 99.9% the speed of light. Now if you take a step back to what the outside observer would measure, the accelerated spaceship would still not be traveling at the speed of light, it would still be some fraction less than c.


EDIT:
In responce to "Thirst Quencher"....
No, even if you blast off on a space ship going 99.99999% of the speed of light in the opposite direction of the motion of the Earth as seen from the Earth looking at the space ship (or as seen fro the space ship looking back at Earth), it still would NOT be going at or faster than the speed of light. When dealing with relativistic velocities, speeds do not add/subtract in the same way we would normally be used to (galilean relativity). In any frame of reference, the speed of light is constant. In no frame of reference can anything with mass travel at or faster than the speed of light in a vacuum.

Answer 3

"one of the ships accelerates to twice its original speed".

This ship cannot accelerate to twice its original speed RELATIVE TO ANYTHING. Thats the whole point. It can't go faster than the speed of light, relative to the other ship (or an outside observer or anything else).

A velocity is meaningful only as a speed relative to something else. For instance, you and I are riding in a car. What speed are we going. Well, if the car is doing 60 mph, we are also doing 60 mph relative to the ground. We are not moving at all, relative to one another, and we (and everybody else) are flying along pretty sporty relative to the sun.

If the ships were going 99.9 percent of the speed of light relative to the outside observer, neither could up their velocities much relative to that observer.

Answer 4

To compute the speed of the spaceship that accelerated, you have to combine the two speeds relativistically, To add relativistic velocities, you use the equation w = (u + v)/(1 + uv/c^2), where u and v are the individual velocities and w is the combined velocity. So, w = (.999c + .999c)/(1 + (.999c)^2/c^2) = 1.998c / 1.998001 = 0.999999c

It will still appear to the captains of both ships that their speed is 0.999c different, but to the outside observer one will only be traveling 0.000999c faster than the other.

Answer 5

At 99.9 % the speed of light, any additional energy added to the space ship would be converted into mass. thus preventing it from going beyond the speed of light.

Time would not be warped. To the outside observer time would remain moving as we know it, to those on the space ship time would dialate almost to 0.

This was part of einsteins big break through on the special theory of relativity. He realized that C was constant and time was relative to the observer.

Answer 6

There should be a caveat here. Most people should be saying according to our current understanding of the laws of Physics nothing can go faster than the speed of light.

I'm also not sure about all this relative stuff. If you took a single point of light and shot it off in one direction and I walk in the opposite direction, then from the perspective of the point of light am I not moving away faster than the speed of light? To put it differently for people who may not like that example, if I had a space ship that could travel at 99.9999% the speed of light and I blasted off from Kennedy space center in the opposite direction of the earths rotation around the sun would I not appear to those on earth to be travelling away from earth at a speed faster than light?

To me it seems ridiculous to say speed is only relative to something else, speed is absolute. Basically dpeed is relative to the object travelling or to itself. It has a specific location in space and over a time period it is somewhere else in space. It's like mass, it is an absolute.

To answer the question an observer would probably see nothing.

Answer 7

Yeah, that's actually remarkable isn't it. some russian astronauts once spent a lengthy time period out in area, vacationing at some 5,000 miles in step with hour. They spent a lot time in area that that they had actually elderly 2 seconds decrease than human beings on earth. i understand that's amazingly miniscule and insignifcant, even though it really is cool. imagine in the adventure that they were vacationing at close to the speed of sunshine; they might have come back to earth and experienced that many years had lengthy gone previous at the same time as that they had in reality elderly some weeks. study Michio Kaku's books - Hyperspace, pararell worlds and that i visit't undergo in thoughts the third one. they are quite reliable, it really is about thoretical physics!

Answer 8

JCCMA is right,infinite mass would require infinite power creating more mass,not possible.

Answer 9

My brain hurts.....