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I have read that nothing can move at or faster than the speed of light, based on the theory of relativity. Yet I have also read that there is no physical law preventing anything from exceeding the speed of light, for example, scientist have accelerated light pulses up to 300 times their regular velocity, so I could move faster than light? Is Einstein wrong, but even if he is, would his theory's effects of light travel still take place (infinite mass, etc)? Which is true, can they both be true?
Question Date: 2007-06-07
Answer 1:

Well, there's a very good physical law that says nothing can move faster than the speed of light. And that's relativity. No, unfortunately given currently established theories you cannot move faster than light through space-time. Experiment has shown this again and again and again. However, space-time itself can stretch itself faster than light can travel, which is what happens when you have a black hole.

The reports you are reading are unfortunately written for laymen by laymen. Think of it this way: if you take a laser pointer, and point it at a very distant galaxy, and then swing your arm all the way across the sky, then the 'dot' would move faster than light (it moves billions of light-years with one swing!). However, you cannot transmit energy or information faster than light in this way (it still takes the actual photons the billions of light years to reach the specified place). Likewise, you can take an infinitely long wall, have a light-house rotate and shine a light on the wall. As you get further and further away from the light-house, the spot moving along the wall achieves infinite speed as the lighthouse rotates away from it... but the real physical things (the photons) generating the spot itself still move at the speed of light.

The experiments that you're thinking about are actually experiments set up such that no information or energy (and therefore matter) is transmitted faster than light. Its a fabricated thing. It is cool, but does not violate relativity. It is just a more complicated version of the lighthouse thought experiment described above.

And since you are matter and energy, you cannot be transmitted at faster than the speed of light =)

Answer 2:

One thing to keep in mind when studying Einstein's special relativity is that it is not a complete theory of nature. That does not make it a bad theory, it just means that there are some things in nature that it does not explain. It is not that it tries to explain things and gets them wrong; it's just that it doesn't try to explain everything. In particular, Einstein's special relativity does not give predictions on the complex interactions between light and matter (another theory called quantum electrodynamics is used to describe these interactions). These interactions are important in all of the experiments reporting "light that goes faster than the speed of light".In order to answer many of your questions, the ideas of "inertialreference frame" and "proper time" from Einstein's theory would be veryimportant. I can see from all of your questions that you are veryinterested in this theory. I would recommend learning more about some of the details of the theory before jumping ahead to these more difficult questions. I think you'll find that even some questions that sound simple have very fascinating answers. To start learning about special relativity in more detail, I would recommend looking for a book in your school library that focuses on explaining it with a minimum amount of math...I remember checking out a book in high school called "Relativity for the millions" that was easy to read and showed many of the most interesting aspects of special relativity.

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