Speed of Ships -- Special Relativity

In summary, observers in B will measure the speed of the spaceship to be slower than 0.65c, as it is moving away from A in the same direction that A is moving away from B. This can be calculated using relativistic addition, making sure that the sum of velocities is less than the speed of light.
  • #1
Barry Melby
31
0

Homework Statement


Galaxy A moves away from galaxy B at 0.650 c0 relative to B. A spaceship leaves a planet in galaxy A traveling at 0.550 c0 relative to galaxy A. If the direction in which the ship travels is the same as the direction in which A is moving away from B, what do observers in B measure for the ship's speed?

Homework Equations



The Attempt at a Solution


I thought that the speed would be .550c , but this appears to be incorrect. Any thoughts?
 
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  • #2
That would be slower than galaxy A is moving.

What do you know about velocity addition?
 
  • #3
From B's point of view, A is moving away at 0.65c. Since the spaceship is moving away from A in the direction of B at 0.55c, B will see the ship move away - but not as fast as 0.65c.
 
  • #4
.Scott said:
From B's point of view, A is moving away at 0.65c. Since the spaceship is moving away from A in the direction of B at 0.55c, B will see the ship move away - but not as fast as 0.65c.
I don't think that is right. I believe the ship is moving in the opposite direction from A.
 
  • #5
PeroK said:
I don't think that is right. I believe the ship is moving in the opposite direction from A.
If the direction in which the ship travels is the same as the direction in which A is moving away from B
You're right. So it's simple relativistic addition.
Just make sure 0.65+0.55<1
 

What is the "speed of ships" in special relativity?

The "speed of ships" refers to the speed of an object, such as a ship, relative to an observer in special relativity. This concept is important because it shows that the perceived speed of an object can change depending on the observer's frame of reference.

How does special relativity affect the speed of ships?

In special relativity, the speed of light is considered to be the maximum speed in the universe. This means that the speed of a ship cannot exceed the speed of light, and as the ship approaches the speed of light, its perceived length and time will change for an observer in a different frame of reference.

Can a ship ever travel at the speed of light in special relativity?

No, according to special relativity, it is impossible for an object with mass to reach the speed of light. As an object approaches the speed of light, its mass increases and it requires an infinite amount of energy to accelerate it further. This is known as the "mass-energy equivalence" principle.

How does time dilation affect ships traveling at high speeds in special relativity?

Time dilation is a phenomenon in special relativity where time passes at different rates for observers in different frames of reference. This means that a ship traveling at high speeds will experience time passing slower than an observer on Earth. This is due to the relationship between time and space in special relativity.

How does the theory of "length contraction" relate to the speed of ships in special relativity?

Length contraction is another consequence of special relativity, where the length of an object appears to decrease as its speed increases. This means that a ship traveling at high speeds will appear shorter to an observer in a different frame of reference. This effect is directly related to the perceived speed of the ship in special relativity.

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