Interesting Idea - The Sounds of the Cosmos

Astrophysicist Janna Levin of Barnard College presents simulated sounds of gravitational waves from black holes in various systems. The idea is that, because gravitational waves, which are predicted by Einstein's general theory of relativity, would stretch and compress our ears at certain frequencies. This would be equivalent to what air pressure waves do to the ear drum membrane in our ears, which is sound. Relativity predicts the frequency of gravitational waves from any astrophysical system, and Levin then simulates what the equivalent sound would be. Keep in mind there is no direct observation of gravity waves yet, but there is a growing collection of indirect evidence that these are real and travel at the predicted speed of light. There are several sophisticated experiments running that look for gravity radiation, and most scientists do not doubt they will be found some day, as they are a natural, necessary consequence of the warping of space-time in relativistic models.

Check it out and enjoy some of the computer simulations of black hole systems.

Very Good video about gravity and Einstein's Idea

This is the snippet from Brian Greene's Elegant Universe. It deals with Einstein's general theory of relativity, and the notion of warped space-time leading to what we call gravity. There are some very good graphics which help us get some pictures in our heads as to how this all works. I encourage you to watch it, and also the 'how to' video below that has to do with relativity and the principle of equivalence, to see how Einstein reasoned light is bent by gravity.

The Basic Principle of General Relativity - Principle of Equivalence

Einstein published General Relativity in 1915. Similar to special relativity, where he only considered frames of reference moving with constant relative velocity, general relativity is based on simple principles that lead to fantastic consequences. In this case, Einstein reasoned that the Principle of Equivalence was the fundamental building block concept for gravity. It states that the effects of acceleration on a system are indistinguishable from the effects of gravity on that system. This video shows an example of this principle in action, and shows how you can quickly figure out gravity should bend the path of light, even though light has no mass (so Newton would say this cannot happen)! This principle also explains why inertial mass (the mass in F = ma) is equivalent to gravitational mass (the mass in F = GMm/r^2), which is why all objects fall at the same rate in a gravitational field. Note that general relativity leads to the Big Bang, black holes, stellar evolution, gravitational red shifts, precession of planetary orbits, effects on time (which are needed for GPS to be so accurate), frame dragging as planets and objects move through space-time, and so on. All are confirmed through observation and experiments. Check it out!

Einstein's View of Gravity in General Relativity

We know a bit about gravity, and the fact that all masses attract all other masses. Newton figured this out in the 17th century. However, Newton never understood where gravity came from. We had to wait nearly 300 years before Einstein proposed the General Theory of Relativity, and the notion of 'warped space-time.' Check out this clip from Brian Greene's Elegant Universe.