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Physicists Find More Precise Gravity Number
DM writes "Physicists establish the most precise measurement ever achieved of Isaac Newton's gravitational constant and use this information to recalculate the mass of the earth. Check out the article at ScienceDaily." Now if they could only recalibrate to make me really buff, that would be nice.
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CAIMLAS
~/ssh slashdot.org ssh: connect to host slashdot.org port 22: too many beers
Q: What do you think about American Culture?
A: I think it's a good idea.
Q: What do you think about American Culture?
A: I think it's a good idea.
(adapted from Gandhi)
...must be some heavy packets, eh?
I use Macs for work, Linux for education, and Windows for cardplaying.
And I was just about to use this 16,000,000 mile lever to move the world and NOW its 20 feet to short... damn scientists!
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I'm a 4th Year Honours Physics Major who did something similar and did a lot of research into this so I know something about this.
As the article said, G is very vague in its defination. Some new calculations have acutally put G at 6.64x10^-11 to 6.69x10^-11 which is quite a huge range. Whereas the two other constants, h [planck's contant] and c [speed of light in vaccum] is more well defined and had gotten more accurate.
The biggest problem with measuring big G [what we are discussion here, instead of little g which is 9.81m/s^2] is the influence of other objects. We did the experiement for our class in a basement labratory and I was able to predict based on minute changes in the data I was getting that people were moving their desks around. I was 4 floors down from the top floor and when I went upstairs, the professor [I was able to predict where in the building from the measurements and the fact that he was the only one up there in that section] admitted he was moving around to re-orient his new desk.
Also, another time, a huge pickup truck came to the parking lot in front of the physics building. I noticed right away my measurements go askew cause of it.
As I said, G is very sensitve to tiny changes in the enviorment, much more then h [planck's constant] and c [speed of light]. Often, to measure the constant G, people has to work when there is no activity going [either at night] or somewhere remote. In fact, one of the recent measurements was taken in the middle of the Nevada Desert.
-- Note: These Comments are Generated by ME! Not You! ME!
Gravitation is important to be able to do simple things like throw satellites up into orbit.
Newton's Universal Law of gravitation tells us that F = GMm/d^2. That means that any two objects in the universe apply an equal gravitation force to each other proportional to the product of the two masses and inversely proportional to the distance of the two objects squared.
So to find a geosynchronous orbit for a satellite, we would equate centripetal force with gravitation and get 4(pi)^2mr/T^2 = GMm/r^2 which would isolate to T^2 = 4(pi)^2R^3/GM, where T was the period of rotation of the planet.
It takes three satellites in geosynchronous orbit to cover the entire Earth, allowing a communication from any two points in the world in up to 0.5 seconds (limited by the speed of light). We have two satellites locked into place, but we have and failed over numerous attempts at putting the third one up, missing the target. Speculation suggests that perhaps an inaccurate value of G could have attributed to some of the failure here?
Even simple energy problems are affected by G. Ep=mgh is only useful for problems close to the Earth's surface. Since g (acceleration of gravity) is an inverse square proportion to the radius from the centre, that means that as the distance changes, so does g. So we must use energy wells. They come from the integration of our F=GMm/d^2, becoming E=-GMm/d (as integral of F-d is work, being energy). So even energy calculations need G.
I could go on forever, but the point is that all masses in the universe are related with constant G, so it therefore is important for us to get a precise value of this constant.
It was suggested that life in the Universe may take on many different forms and shapes. There are theories (hypotheses) of having life on neutron stars (the left overs of the star cores that collapsed on itself to produce a remnant size of earth and mass of 2-3 Suns that due to its huge mass and small size spins at almost the speed of light.) Life on such an object would not be supported by chemical reactions since no molecules not even atoms can withstand enormous temperatures produced on the neutrino stars. Still, we should not lose all hope, for life based on strong forces remains conceivable there.
:)
Strong forces hold together the nuclei of all atoms more complex than hydrogen. Suppose a proton some 10^-13cm in size travelling at speed of 1000kilometers per second (average speed for a proton) at temperature of 1million K. It would cover a distance of 2 meters in 10^-21 of a second. Human would cover this distance in about a second. So for a proton 10^-21 second means the same as 1 second for a human.
Collisions of many elementary particles on a neutron star could produce massive nuclei, each made of thousands and tens of thousands, of elementary particles. They would last for 10^-15 of a second and then decay. In other words, a massive nucleus might have a million different collisions or other interactions before it decayed.
So if these particles could produce some equivalent of a structure capable of storing information and of replication by selective copying (like the DNA or RNA) star might produce forms of life. Individuals that interact with their environment and with other individuals in an organized way.
If this really happened, the development of life would happen much faster than what we observe in our solar system.. 10^-21 second is one billion-billionth of the thousandth of a second then the origin of life would require not about 1 billion years (our planet: ~600million years) but about 1/billionth of a year, of 1/13 of a second! It may seem short to us but it might exist on the surface of a neutron star. (too bad we could not interact with them)
On the other extreme end of this is the type of life we could call a "Gravitational Life" based on Gravitational forces. A typical subunit of life would be so large that gravity would be the dominant force for it, not electromagnetic force, a star would work in this case as a base unit. Individual stars would play the role of atoms (or molecules) on Earth. An organism so large that its basic building units are stars and galaxies (maybe even multiple universes) could in principle be possible. Would you like to think about yourself as of basicly microorganisms living in a huge super organism? Of-course star and galaxy interactions are upon scale of millionth of years, so if life originated from repeated effects of such interactions (like molecule interactions) then there is a long way to go before a living organism based on this interactions could develop.
And you think the mass of earth is important
You can't handle the truth.
You give a very self-centred view of science.
You are right, if you know surface gravity and the mass of the planet then you can get around G. But wait -- we didn't know the mass of Earth correctly. If you read the article, as a result of finding the more accurate G now we have a different number for the mass of Earth. So how is it that G is unimportant?
In close orbit perhaps the significance of these numbers is smaller, but in geosynchronous orbits where the satellite has to be locked into place 4.215x10^7 m away you'd better be sure that your numbers are right so that you're not just throwing billions of dollars randomly into space.
We can't find the mass/density of planets and stars without G. We have to throw something into orbit above it. If we don't even know mass + density then it's obvious we can't use Mass + surface gravity to do calculations. The other way is to go on the surface and measure acceleration, but good luck on planets like Venus with acid rain up the wazoo.