General Relativity: A basic guide

A friend of mine today asked me "what is General relativity anyway?" and it struck me that it is a question that quite a few people might not know the answer to, even though it is arguably the most beautiful piece of mathematics and theoretical physics ever written, and it came from undoubtedly the greatest mind of the 20th century, if not one of the greatest minds that has ever lived. I'm talking of course about Albert Einstein.

   Now, the first issue that I can think of that would perhaps explain why people do not recognise the theory of General Relativity is because they mistake it for another of Einstein’s' trailblazing works; E = MC² which is actually used to describe the relationship between the mass of an object and the energy contained within it, but a more succinct explanation should be given a blog post of its own, and this is not that post. So let us swiftly return to Relativity.

  Now that we know what relativity is not, let us explore what it is, which is, in its most basic wording, the most accurate model of the universe that we can currently provide. But I think that we should go a little deeper than that in our quest to understand General Relativity, and attempt to explain what it actually means in terms of the universe.

  The most fundamental principle of Relativity (both special and general, I would explain special relativity, but again, that’s for another post) is that any object in a gravitational field should feel an effect proportional to its mass, as in the Gravitational laws of Sir Isaac Newton, but that this ceased to be the case when an object was in “freefall” when it would experience weightlessness, whether the freefall occurred here on earth or in deep space, far from a body with a gravitational field.  He also concluded that as light moves away from a body with an immense gravitational field, such as a star, light can be slowed down or stretched so that it has the frequency of the lower energy end of the spectrum, which shows as a red colour, in a phenomenon called “red shift” as a direct result of the interaction with the stars gravitational influence.

 However, the most important aspect of Einstein’s theory of general relativity is related to the infamous formula previously stated “E = MC²” and thus we travel into a confusing area. The model used for Einstein’s universe is a 4dimensional “fabric” known as space-time, which can be bent, distorted and shaped by the momentum, mass and energy of any given body (such as a planet or star) which is the CAUSE of gravitation, the interaction between an objects mass, momentum and energy (which are essentially the same thing, according to E = MC² and special relativity) and the fabric known as space-time.

 Now, I know that this may still seem far-fetched to you, dear reader, but I will attempt to explain this further over the coming weeks and months, with other posts. If I have lost you completely, please comment with questions. =)