Light Speed

[xilus]

Here is what I believe to be truth:

1)The Speed of light is constant in any reference frame

2)Nothing can go faster than the speed of light (Including light)

 

Let us say that there is a space ship with a headlight which is flying away from the earth at light speed. It then turns on its headlights and the light goes zooming away from the space ship at.. once again.. lightspeed.

 

In reference to the earth, wouldn't the light be moving away at twice the speed of light?

[ajb]

Here is what I believe to be truth:

1)The Speed of light is constant in any reference frame

2)Nothing can go faster than the speed of light (Including light)

 

You mean in any inertial reference frame.

 

Let us say that there is a space ship with a headlight which is flying away from the earth at light speed. It then turns on its headlights and the light goes zooming away from the space ship at.. once again.. lightspeed.

 

In reference to the earth, wouldn't the light be moving away at twice the speed of light?

 

No, it will still be moving at the speed of light.

[xilus]

No, it will still be moving at the speed of light.

right, and this is possible because of some space time warping right?

 

Time is hardly moving for the space ship, because it is moving almost the speed of light.

so, what is actually light moving only a little faster than the space ship appears to be light moving at light speed.

 

wait... if time is moving slower for the ship then why would that make it look like the speed of light stay constant?

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I am talking about relativistic kinematics right?

This can be understand perfectly mathematically right?

where time is a fourth dimension.

[Bob_for_short]

... if time is moving slower for the ship then why would that make it look like the speed of light stay constant?

 

Forget about time. There is a law of velocity adding, a relativistic law. It is more complicated than just v3 = v1 + v2. According to this law (discovered by H. Poincaré) whatever v1 and v2 are, the resulting v3 is smaller than or equal to c.

Edited September 22, 2009 by Bob_for_short

[JillSwift]

Forget about time. There is a law of velocity adding, a relativistic law. It is more complicated than just v3 = v1 + v2. According to this law (discovered by H. Poincaré) whatever v1 and v2 are, the resulting v3 is smaller than c.

Is that the one discussed in this Wikipedia article?

[timo]

right, and this is possible because of some space time warping right?

I think in the scientific context "warping" is used for a change in spacetime curvature - if at all. There is no spacetime curvature existing/relevant for your question.

 

I am talking about relativistic kinematics right?

This can be understand perfectly mathematically right?

where time is a fourth dimension.

Yes.

 

Forget about time. There is a law of velocity adding, a relativistic law. It is more complicated than just v3 = v1 + v2. According to this law (discovered by H. Poincaré) whatever v1 and v2 are, the resulting v3 is smaller than c.

|v1|=0, |v2|=c => |v3|=c. Note that the thread particularly is about one of the velocities being c.

[xilus]

Does this equation encapsulate the concept that I need to understand?

[Bob_for_short]

Is that the one discussed in this Wikipedia article?

 

Yes, the formula for s.

[ajb]

right, and this is possible because of some space time warping right?

 

 

Yes and no.

 

Warping usually informally refers to space-time curvature, think of difference between the plane and the sphere.

 

In special relativity the space-time is flat, it is more like the plane than the sphere. However, it does have interesting geometry in the form of the Minkowski metric which defines the causal structure.