Gravity, when the feeling's gone and you can't go on, it's gravity
- Thread starter RudeCurve
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Mintmaster
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You don't need work to exert a force. You just need a potential energy field. Gravity provides such a thing.
If you want to look at objects following a gravity-influenced trajectory as geodesics (i.e. 'straight lines' on a curved surface), then you have to accept that not all paths have the same energy. In the absence of gravity (special relativity), an object following a trajectory has total energy E = m*c^2, with m being dependent on speed. Two objects with the same rest mass and same speed will have the same energy, regardless of which straight line they move along. When you add gravity in there (general relativity), the trajectory now also matters for energy.
If you moved earth 0.001 AU away from the sun while maintaining its velocity, you will increase its energy. If you moved it perpendicular to the the earth-sun vector, however, you would not change its energy. The energy can be mapped to a field in space, and by definition force is the negative gradient of that field; in this case, it points towards the sun.
Gravity is not fundamentally derived from Newton's formula of an attractive force equal to G*m1*m2/r^2, but it still results in a potential field that applies forces.
Actually that's a misconception, universal gravitation (and in a mathematically more correct manner too) was discovered by Johannes Kepler quite some time before Newton. Look for the book "Harmonies of the world", the reprint is still available on Amazon etc. The story of Newton watching the apple is obviously just a fairy tale to make the story more interesting.
Are you sure Kepler extended his three laws of planetary motion to apples?
So did he extend his law of planetary motions to apples or not? You can just give a simple yes or no answer, or retract your "Kepler discovered universal gravitation before Newton" comment.
Call me a traditionalist, but I learned that any acceleration of a [macroscopic] body is tied to a force. F=m*a. Gravity may not be a force per se, but it sure as fuck is an acceleration. Gravitational force, as much as it offends your anal hair, is the force that appears necessarily in tandem with this acceleration, lest the universe invert and we all turn green.
Kepler described his three laws of planetary motions in that book. And that's NOT universal gravitation. For example, it does not take account of inter-planetary gravity forces, nor it can explain why some planets have disturbances in their orbits (that's what leads to the discovery of Neptune). Do you think it's possible to explain that with the three laws alone?
You don't even need physics to show RudeCurves belief in these machines is misplaced. You simply need history and statistics. History shows us that statistically nothing ever comes of them
Yes when looking at the past....question is can you look into the future?
The things that can be explained today is based on past and current understanding...
This is the past we're looking at. 3 years ago a guy created energy from nothing, thus violating a law of Physics. He refuses to publish his work or set-up even though he has a patent issued and nobody can reproduce it outside of his lab. That's 3 years that a miracle energy device has existed with nothing to show for it. Pretty conclusive history there. He's full of sh*t and it doesn't work.
Um...a magnet is NOT a spring! A magnet is analogous to a dense piece of matter that exerts forces on other objects. All matter have an attractive force. The higher the density of the matter the stronger the attractive force. With magnets whether you pull them apart or not they are ALWAYS exerting an attraction/repulsion force on another magnet. A spring is just a piece of metal that resists compression/expansion due to its mechanical material strength and shape.
The guy's job isn't to satisfay the naysayers. He's taking his time to fully try to understand and apply his invention. Things don't get invented and made into a product by one person in a few years.
Why do you get your panties in a knot over this anyway?
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Neither does the theory from Newton take many things into account, so what's your point?
Fact is, Kepler discovered it first and even if the theory in its original form is not that sound nowadays, he was the first to see it and describe it in somewhat correct manner, way before Newton.
If you want to walk down that road, Galileo thrumps Kepler:
http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0003841.html
Your point being?
My point is, Kepler did not discover "universal" gravitation. His theory is only about planetary motion. So if you want you can call it "planetary gravitation." Newton, on the other hand, realized that the same force which moves these planets are the same force which makes apples fall to the earth. This is "universal" because he realized that everything has gravity, not just planets and the sun. This is actually very important because it's not only able to explain how planets move, it can also explain how moons move, and eventually leads to the discovery of Neptune. It won't be possible with just Kepler's three laws.
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