It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Originally posted by Immune
reply to post by roughycannon
well at what point does the speed of rotation null the effect of the mass? a particle of dust on a speeding tire will not stay put how do we?
Gravity goes with mass. Everything that has mass also has gravity. The gravity is proportional to the mass, so if the mass increases by a certain factor then the gravity also increases by the same factor. So, gravity does not come just from planets. Gravity belongs with everything that has mass, so it also belongs with you. However, the gravity that you generate is very much weaker than the gravity that a planet generates, and is also very much weaker than the electromagnetic forces that determine the characteristics of all things around us (except for radioactivity), so usually you do not notice that things on Earth also generate gravity. Albert Einstein has taught us that space and time are interwoven, so that how long something is or how long something lasts is not the same for everyone even if everyone has perfect measuring devices. Those kinds of effects are only important for things that go almost as fast as light. For example, some very fast cosmic rays can get down to fairly low in the atmosphere because for them time goes slower, because of their very great speed (or, according to them, that the atmosphere is thinner) and it takes longer (according to their clock) for them to fall apart than it would for similar but slower cosmic rays.
Space-time (the combination of space and time) is curved by nearby mass, just like a heavy ball makes a dent if you put it on a stretched rubber sheet. We notice curvature of space-time as gravity. If you roll a marble across the rubber, then the marble will deviate from a straight course because of the dent, just as if the marble is attracted by the ball that makes the dent, but really the marble deviates only because the narrow strip of rubber that it rolls along is not level, whether that is caused by the nearby ball or by something else. In the same way, it appears as if the Earth's gravity pulls at the Moon and so keeps it in an orbit around the Earth, but really the Moon is kept from following a straight path because space-time on her path is not flat, which is due to the presence of the Earth. So, nothing special happens in a planet for it to generate gravity. You can notice the gravity of a planet only because it has such a very large mass.