When it was first developed, the standard model predicted a collection of particles, and thanks to more and more powerful colliders, physicsists have been able to find them all except one: the Higgs-Boson. It's an important one because it should explain how objects have mass. The European Large Hadron Collider should have the power and sensitivity to find the Higgs-Boson.

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we are just a bit speechless harry

Hydrogen is made of very few particles, does this not explain why it has 'lighter than air' properties?

yes harry

maybe when we unifiy quantum theory and relativity someone will answer you

tho if the higgs turns up......

Surely this force is going in the wrong direction. If you imagine yourself as the earth, whirling a ball on a string around you, you can feel the ball pulling away from you, not falling towards you.

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Spike
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I think it's more that you need to exert force inwards to stop the ball from flying off at a tangent. The motion of the ball does not cause an inwards force.
A better example might be if you sit on a roundabout and set it spinning. If you don't hold on tightly, you'll be thrown off, not pulled inwards to the centre...

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Spike
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I don't think so, Harry. What the wiki extract above says is that you need to generate an inwards (centripetal) force to maintain an object in orbit. In the example before, that's you pulling on the string to stop the ball flying off at a tangent. And for the earth, gravity provides the centripetal force that keeps objects in orbit.

The key statement is that "...centripetal force is a force requirement, not a particular kind of force." What I thought you were saying, Harry, was that an object in orbit somehow generates an inward (centripetal) force, which I don't think is correct.

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Spike
:)

So are you saying that electromagnetism is the same as gravity? Or that electromagnetism generates gravity?

In the first case, there are big differences between electromagnetism and gravity. (I think this thread covers these: Why isn't it obvious that Gravity, Electro-Magnetism, and the Stronge Nuclear force)

In the second case, what's the mechanism whereby electromagnetism generates a gravitational field? And why isn't it reproducible in a lab (because it would be pretty obvious if it happened)?

Or have I got the wrong end of the stick and there's a third option?

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Spike
:)