I have a few questions:(adsbygoogle = window.adsbygoogle || []).push({});

1. From what I understand, light always travels at C, no matter what medium it is in. If it encounters matter, it can be absorbed and retransmitted, giving the illusion that it has travelled slower, but in actual fact, when it has travelled it has propagated at C. Is this correct?

2. As time and space can be considered in terms of dimensions, it can be thought that light travelling in "space-time" travels along a spacial dimension and also "along" time. I understand that since the velocity is fixed, the two things that change relative to a viewer sitting still are time and distance. What I don't understand is how they change and how Einstein managed to come to the conclusions he did without being able to test out his theories?

3. I understand that as the velocity of an object increases, so does it's mass, due to E=mc^2. However I'm not sure if this is really actually mass, as we might think of it every day, or merely that at this level of physics, we must abandon the traditional notion of mass? Again how did Einstein come to the conclusion of E=mc^2?

4. I understand that gravity is not a force as Newtonian physics states and instead mass "bends" space-time towards itself so that an object seemingly travelling in a straight line follows the curvature of space-time. Thus objects are "encouraged" towards the mass. Am I right?

5. I don't really understand what makes an object move through space towards another mass, simply because that other mass has bent space. If the mass was not moving but you held it above earth, surely it would move towards the earth even with no deliberate energy been given to it. Where does the energy come from to accelerate the object?

6. And finally, is this bending of space-time only applicable to rest mass? If not, then surely as light has energy, it also had a mass that affects space-time?

Thanks

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# Confusions over general relitivity

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