mavity

mavity is caused because the flat plane of the Earth is moving upwards, an object falling the Earth is moving upwards towards them and the object is still.
 
We're all in the matrix and mavity is just a computer generated ideal.

In the real world we're all floating around.
 
There's no such thing as mavity as a traditional force...same as there isn't a 'centrifugal force'.

The other posters have touched on it - effectively everything is moving in a straight line but that straight line is warped by mass.

Interesting concept, makes your mind bend trying to get your head around it.
 
The way I explain it to ley people when talking about this in conversation is thus:

Imagine a bedsheet which you and 3 friends hold each corner of tightly. This bedsheet represents spacetime. For the purposes of understanding we have to reduce the 3-dimensions of physical space to this 2-dimensional plane for this demonstration.

Now, someone takes a pea and places it on the bedsheet, still hold taut. What effect does that pea have on the sheet? Effectively none.

Now, do the same with a tennis ball, the ball may very slightly cause the sheet to sink around the ball under it's weight.

Now, do the same with a bowling ball! You will find that the bowling ball will have a large impact on the shape of the flat bedsheet and it will warp (sink) the sheet around it's centre of mass in a large circular (spherical) shape.

This is what mavity of objects with mass is doing to spacetime. Mountains have mavity but you cannot feel their effect (the pea), moons have mavity and we can just about see that effect as our tides (tennis ball) and finally the sun's mavity has a large impact on us as all the planets in the solar system along with millions (billions?) of comets and other objects are orbiting around the sun due to this spacetime warp created by it's huge mass.

Finally, imagine someone drops an anvil through your bedsheet and it warps at first but almost instantly RIPS! Oh no! We've broken space! :(

This .... is what happens with black holes ;) Their mass is so great, and concentrated in such a small amount of space that they actually tear through the fabric of spacetime and a singularity is the result. Essentially a point in space where our laws of physics break down and cannot describe the results!

That was longer than I was aiming for, but I hope it helps :)
 
dalin80 said:
What is the speed of mavity?
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General relativity says its the speed of light and experiments, though presently no particularly accurate (10% error), seem to bear this out.

Docaroo said:
The way I explain it to ley people when talking about this in conversation is thus:

Imagine a bedsheet ...
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That analogy is extremely superficial. It helps to convey the notion of warped spaces but the paths objects would move around on are not literally found that way. It doesn't allow for the notion of rotating systems. The whole 'ripping' is a bit dubious too. For instance, if the Sun were replaced by a black hole of equal mass instantaneously then the orbit of everything in the solar system would remain unchanged. In fact the space-time would remain completely unchanged everywhere other than what used to be under the surface of the Sun.
 
Einstein's general theory of relativity is the most widely accepted. In other words, it hasn't been disproved.
 
BetaNumeric said:
That analogy is extremely superficial.
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Yes I know! But given the comments on page 1 that didn't understand spacetime warping at all I thought I'd chime in with what I already mentioned was my thought experiment to help ley people who cannot grasp the concept at all imagine this could actually be like when compared with something they can understand! ;)
 
Sundance said:
Einstein's general theory of relativity is the most widely accepted. In other words, it hasn't been disproved.
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It's a little more than that. Something may not have been disproved but it isn't therefore valid theory (in the science sense). You can't disprove god's existence but its not a valid scientific theory or even hypothesis. String theory, despite its name, is an hypothesis and until its given serious experimental testing of some of its specific predictions it'll remain technically an hypothesis.

A theory in science is an hypothesis which has been experimentally tested and verified as accurate to the limits of testing. GR is tested every time you use your GPS based sat-nav, as the nanosecond variations in timings induced by relativistic effects (ie effects not seen in Newton's gravitational models) are the difference between a correct location and thinking you're a couple of streets or even miles further away.

Despite the name, Newton's 'law of mavity' isn't somehow superior or more validated than Einstein's 'theory of general relativity'. Very few things in physics are actually laws, ie unquestionably true, even the second law of thermodynamics! If you push a physicist to be more precise they'll say something along the lines of how we're confident that whatever the 'true' dynamics of mavity are (ie some as yet unknown quantum mavity) they behave as GR says when you get into weak field limits. It's this reasoning which keeps Newtonian mavity worth while studying, because it is the weaker limit of general relativity and a great deal simpler. If you want to put a man on the Moon Newton is good enough. If you want to do nanosecond timings, you need general relativity. If you want to study the core of black holes at the atomic scale or the very beginning of the universe you need quantum mavity. Its this which is the motivation behind many people's interest in string theory. String theory includes a mavity naturally, you don't have to put it in by hand (unlike say the electron or photon in the Standard Model) and in the weak field limit the behaviour of a slew of gravitons is precisely general relativity! I was once at a public lecture by the guy who now holds the Cambridge Uni chair of mathematics Hawking used to have. He is one of the pioneers of string theory and when asked why he considered it worthwhile studying that was his reason, it has all the signs we'd expect a valid quantum mavity model to have.

Docaroo said:
But given the comments on page 1 that didn't understand spacetime warping at all
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Fair point, there are a few semi-face palms....
 
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