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Originally Posted by Tassel
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Originally Posted by davidlpf
Heres my two cents, mass is the amount of stuff in an object, weight is the effect that two objects have on one another say the earth and a person which is F in both equations.
f=m*a or sometimes written f=m*g is the force of acceraleration in gravitional feild of the the earth and can change if the mass of the larger object changed to like a star or blackhole or another planet and the f= m*m*G/(r^2) is just two particles in isolated system like deep
space but this G is a constant of the universe. At least that my version of whats going on i could be could wrong I am often.
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Particularly because this thread is in the "General Astronomy" forum, I think that it should be pointed out that you're right on the money, David. All evidence points to a constant G and it seems to me that you correctly understand the difference between weight and mass. |
This is all we know for now. If we had reason to suspect otherwise, I am sure we'd be looking into it. And looking is exactly what we are about to do.
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Originally Posted by papageno
So, why do you think anomalies like the Pioneer anomalies, have anything to do with G?
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Let's leave that to
ESA's future probe, where they will have a separated "flywheel" registering inertial mass, and the equivalence principle. But what if they find that inertial mass and spin are different there? Would "equivalence" not dictate a different gravity at work in that part of space, say at 10-30 AU from the Sun, for example? And if that gravity is different, would it not impact how G is measured out there? And if it shows to be a variable, are we prepared to cope with that conceptually?
But I personally think the Pioneers Anomaly is the least of our problems,that there are enough holes out there in our cosmological theories to allow for new thinking. For example:
- [1.] How are stars born from hydrogen clouds, since there is insufficient gravity to make the clouds come together with enough force to start nuclear fusion, a mystery.
[2.] "Dark matter" foils our understanding of how galaxies rotate, in violation of the inverse square law for gravity.
[3.] Why do the gas giants sport such massive atmospheres, especially if the inner core planet is small? Why does our local moon have no atmosphere, but Pluto a small planet a fraction of our moon, or Saturn's Arizon sized Enceladus, does have an atmosphere?
[4.] How can a "dark matter galaxy" exist, when it has no visible stars?
[5.] Cosmic light redshift, though now ascribed to a Doppler effect of expanding universe, may find a different interpretation if gravity is different for 99.99% of the spacevacuum between galaxies.
[6.] Why are there unmodeled gravitational anomalies on Mars, or Venus, for their prominent features? Or why are the giant's rings dirtier near the planet than further out, where they're almost pure water ice?
[7.] Why did astronomers find "clumps of dark matter" in space?
I think the Pioneers Anomaly is the smallest of our mysteries, judging from the list above. Explaining these things takes incredible contortions of reason, if not outright fancy, such as the Big Bang; including theorized gravity waves never detected, or more "elementary" particles yet to be discovered, like the Higgs boson. There's lots of room for an improved theory on how gravity works, or how it interacts closer in to star generated energies. Can a variable gravity, a variable G as discussed here, be the answer? I don't know. But we should try to see if that may not work better than what we had been working with so far, assuming a universal Newton's 1 G proportional for the whole cosmos.