Re: gravity

Posted by ScottyHOMEy on August 09, 2008 at 19:43:30 from (71.241.215.129):

In Reply to: gravity posted by ken in texas on August 09, 2008 at 16:24:28:

Listen up, buster! Gravity is not just a good idea. It's the law! ;8^)

If it's any comfort, you're not alone.

They've done a lot with physics since Newton. And a lot of it in this century. (I was fortunate enough to sit in on a lecture by a fellow who worked with Rutherford in the old Cavendish labs in England, back in the 1920s when they were trying to prove the existence of the neutron which, at the time, was still just a theoryitcal particle.)

So we've come a long way in a short time. We can build machines that can split atoms. We've learned enough that the astrophysicists and cosmologists are trying to figure out where the dark matter and the dark energy are, we've identified several layers of ever-smaller sub-atomic particles and the strong and weak nuclear forces that make them behave as they do. But, despite a lot of work on the subject, there has been almost no progress on the very basic nature of gravity, something that was identified and quantified centuries ago. It's a force. But is it a wave? If so, low or high frequency? Why can't we detect it . . . The current direction is still part of physicists' quest to to have a unified theory of electromagnetism (think of a generator --see, we made this about tractors, didn't we!) and the strong and weak nuclear forces. Gravity is the one confounding their efforts.

Here on earth, try to think of it in the sme way as the force of air pressure that we don't sense. There's something like 15 pounds of air over every square inch of your head, but you don't feel it pushing down on you. At the equator, yes, you're spinning around through space at something like 1,000 mph, but that's on a radius of something like 3500-4000 miles. But it's the gravitational attraction that keeps your feet on the ground.

Just to tie those together, I used to wonder (a question not unlike yours) why, if the earth was spinning at 1000 mph, we didn't have 1000 mph winds on the surface. That has to do with the fact that that 15 pounds of air also has a mass that is attracted by gravity, so that it can be relatively stable. Air is, of course fluid, so it responds more readily to other forces and is subject to more variance. We call the variances weather. thankfully, we are made of sturdier stuff, so that a low pressure doesn't set our gall bladder spinning one direction while our liver spins the other.

The force of gravity can be calculated as a function of mass and distance. Basically it is the product of the two masses, multiplied again by a derived figure called the gravitational constant, all divived by the square of the distance between the centers of gravity of the objects, meaning that gravity weakens more quickly with distance than it does with the size of the objects.

As a result, while the mass of your body might not change (that is, the amount of matter that makes it up), you will weigh less atop Mount Everst than you will on the beach at Waikiki, only because you are further from the center of the earth. Your feet will be in contact with the same planet, but you are further from it's center of gravity. Go figger.

Replies:

• Re: gravity mowr 09:21:43 08/10/08 (0)

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