Of course we do and with great precision. If not, we could not put up satelittes and know their orbit ahead of time.
Hmm..turns out we don't have 'great precision' after all...
Hey for all y'all that were discussing gravity, here is an article showing how we might just be wrong in our current understanding of gravity...
.. http://www.xs4all.nl/~carlkop/gravnew.html
In this article, it details that satelites sent out into space aren't obeying the known laws of physics..then there is an article after that saying. oh wait..weve explained it, it turns out its a heat signature in the satelite..then another article after it says oops, i guess we were wrong, the satelites are not obeying the laws of physics after all..dang and we were so sure we had it right.
here is some more:
There is perhaps no current problem of greater importance to astrophysics and cosmology than that of "dark matter". The controversy, as the name implies, is centered around the notion that there may exist an enormous amount of matter in the Universe which cannot be detected from the light which it emits. This is "stuff" which cannot be seen directly. So what makes us think that it exists at all? Its presence is inferred indirectly from the motions of astronomical objects, specifically stellar, galactic, and galaxy cluster/supercluster observations.
The basic principle is that if we measure velocities in some region, then there has to be enough mass there for gravity to stop all the objects flying apart. When such velocity measurements are done on large scales, it turns out that the amount of inferred mass is much more than can be explained by the luminous stuff. Hence we infer that there is dark matter in the Universe. There are many different pieces of evidence on different scales. And on the very largest scales, there may be enough to "close" the Universe, so that it will ultimately re-collapse in a Big Crunch.
basically what it is saying in that quote is, our current understanding of gravity is that it is caused by mass. Now when scientitsts observe distant objects, they see by observation that they are behaving in ways that they shouldnt be considering the amount of mass they have.
So instead of saying, hmmm..perhaps gravity isnt caused by mass after all but something else, the scientists say oh that must mean there is some mystical invisible dark matter that makes up for the mass we fail to observe.
Please refer to my post about the moon being made of cheese. people say extraordinary claims require extraordinary proof, but sometimes extraordinary proof produces extraordinary denial for skeptics.
Critical thinking is a good thing, however too much critical thinking blinds us to new discoveries and impeeds scientific progress instead of aiding it.
-Dan
