# Albert Einstein's theory of special relativity.

1. Jan 20, 2006

### id

Looking at Albert Einstein's theory of special relativity. I can see one major flaw in it.

i add a statement from wikipedia, since it is a most acceptable form of information via the net (http://en.wikipedia.org/wiki/Speed_of_light)

"Most individuals are accustomed to the addition rule of velocities: if two cars approach each other from opposite directions, each travelling at a speed of 50 kilometres per hour (31 miles per hour), one expects that each car will perceive the other as approaching at a combined speed of 50 + 50 = 100 km/h (62 mph) to a very high degree of accuracy.

At velocities at or approaching the speed of light, however, it becomes clear from experimental results that this rule does not apply. Two spaceships approaching each other, each travelling at 90% the speed of light relative to some third observer between them, do not perceive each other as approaching at 90% + 90% = 180% the speed of light; instead they each perceive the other as approaching at slightly less than 99.5% the speed of light."

Then my thought of reason is that people dont see that that AE trying to measure something that is 180% over the term of the measurement with something that can only equal 100% of it is wrong, yet i could be wrong

2. Jan 20, 2006

### ZapperZ

Staff Emeritus
Say what?

Have you looked exactly at the Lorentz transformation of such velocities before proclaiming that there's a flaw?

Zz.

3. Jan 20, 2006

### id

No I havent but its something I shall look at, yet I shall add that I am not well versed in the terms/subject of science, yet i have a passion for the subject, and if I learn something new, then all the better for me!

4. Jan 20, 2006

### rbj

don't count on that. there is some real crap on wikipedia. some of us are trying to keep a lid on it, but there will always be some crap on it.

i think what you don't understand is that velocites do not add linearly. at speeds much less than the speed of light, it appears that they do, but that is only a very good approximation.

5. Jan 20, 2006

### Staff: Mentor

Sorry, but I have no idea what this statement means.

The quoted passage is just a statement describing how velocities must be added in the light of special relativity, which has been amply confirmed by experiment.

Where exactly is the "flaw" in applying the well-known relativistic addition of velocities (which applies to all speeds, not just speeds close to light speed)?

A more reliable source of basic information about relativity is hyperphysics: http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/einvel.html

Last edited: Jan 20, 2006
6. Jan 20, 2006

### JesseM

Perhaps it would help if you looked at the actual equation for addition of velocities. If an object is moving at a speed of v relative to me, and I am moving at a speed of u in the same direction relative to you, then in your frame the object will be moving at a speed of $$\frac{u + v}{1 + uv/c^2}$$. So, for example, if v=0.9c and u=0.9c, then this gives a speed of (0.9c + 0.9c)/(1 + 0.81) = (1.8c)/(1.81) = 0.9945c. Do you see any problem with this?

7. Jan 21, 2006

### ZapperZ

Staff Emeritus
Having a "passion" is not a licence to make statements like that, especially when you are admitting you haven't STUDIED the subject matter. Can't you see that you can easily make such a statement out of ignorance?

One should never proclaim something on a matter that one has very little knowledge on. This doesn't apply just to physics.

Zz.

8. Mar 14, 2011

### Science Proff

It seems that what you are saying about the flaw in Einstein's theory, is wrong. You can't say that if two objects are travelling at the same speed, it would seem that the total speed is the addition of both speeds. after all they are two different bodies and though momentum might be same but the overall speed would not be the sum of both. After all, Newton's laws of motion are basically applicable only for objects travelling at a speed far from the speed of light and his laws are not applicable for those travelling at a velocity close to 300000 km/s while Einstein's laws are.

9. Mar 14, 2011

### nitsuj

Actualy, one should never proclaim what another one should say about a particular subject.

And your right, that doesn't apply just to physics.

10. Mar 14, 2011

### ZapperZ

Staff Emeritus

Zz.

11. Mar 14, 2011

### harrylin

Not really! Wikipedia is usually not too bad and may have good links, but the main text is in principle unreliable. The most acceptable easily accessible form of information on the net is copies of peer reviewed journal articles, or Arxiv versions of the same.
Sorry I can't follow you, but anyway it is based on something that he did not write. You can find a rather good translation of his first paper on SRT here:

http://www.fourmilab.ch/etexts/einstein/specrel/www/

You are interested in section 5, "The composition of velocities".

Harald