On Sat, 16 Feb 2008 07:33:02 UTC, Plato <|@|.|> wrote:

> OK I understand the below....

>

>

> Gravity is the other common force. Newton was the first person to study

> it seriously,
Well, actually, you could say the first was Galileo, who got the right law

for how things fall, after thousands of years of everybody being wrong.

(And before him some clever Medieval guys did things with the mathematics

of changing speeds, but they never really studied gravity.) But that was

just falling bodies here on Earth, and he never made a universal law of

it.

> and he came up with the law of universal gravitation:

>

> Each particle of matter attracts every other particle with a force which

> is directly proportional to the product of their masses and inversely

> proportional to the square of the distance between them.

>

> The standard formula for gravity is:

>

> Gravitational force = (G * m1 * m2) / (d2)

>

> where G is the gravitational constant, m1 and m2 are the masses of the

> two objects for which you are calculating the force, and d is the

> distance between the centers of gravity of the two masses.

>

> ....OK, Einstein was the second brain to study it seriously........

>

>

> But my question is:

>

> Are both those dudes correct? Or is gravity just "space" pushing us

> inwards to fill the hole a hole in space???
On the physical law, Newton was quite correct so long as you didn't have

to deal with very high speeds or very strong fields, which were impossible

to observe in his day. Einstein's version covered a lot wider range of

conditions. Under "normal" conditions, Einstein's version simplifies to be

the same as Newton's. If it hadn't, he'd have dismissed as crank; in fact,

he *would* have been a crank.

But in the way one *talks* about it, which is more or less a matter of

philosophy, the universal attractive force turns out not to work

universally; or you could say it doesn't even make sense universally.

Einstein's bent space-time does work, so far, provided you don't have to

make it work closely with quantum mechanics.

But but, "pushing us inwards" isn't really what it's about. It's about

taking the shortest course in space-time between two points in space-time.

An orbit really *looks* curved when you look at it, not like a shortest

path at all, but that's just because you're looking at it in 3 dimensions

and then looking at your watch, which is not the right way to compute the

path in the 4 dimensions. I hope this is perfectly clear to you, in which

case there will be *one* person to whom it is clear.

--

Dan Drake

(E-Mail Removed)
http://www.dandrake.com/
porlockjr.blogspot.com