h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Sorry, should have made it clear that >>mass<< has the unit 'kg'.

The square of a speed is the rate at which the *growth rate* of an area is increasing. However, this is meaningless outside context. The kinetic energy of a body is 1/2 mv^2, but it's not derived by looking at how fast areas are accelerating...

I'm getting a

Sorry, Felonious, but the relevance of your recent posting escapes me

h5ringer, all perfectly true in terms of the maths, but how do you propose measuring it practice? It is the physics of what is being described that interests me.

Fine, Tufty, but write it as c^2 = E/m and tell me what you think it means

h5ringer, correction to my last. What is it that you think it measures?

I am still trying to decide whether Felonious Monk's reference to kinetic energy is in relation to gravitation or radiation. Or both. In which case this is one of the points I was making in my entry; that one source of energy is common to both in the integrated system Bohr envisaged.

An earlier comment sought to tell me that inverse-square ratios were not uncommon, which is exactly the same as I said in pointing to Newton's appropriation of the one in Kepler's laws to apply to gravity with no indication on any physical connection with Hooke's use of it in describing Earth's gravity. His ludicrous later rationalisation of a pull, by every particle on every other, was trashed as absurd by the brilliant Richard Feynman. So why object when I say the same thing?

The point I am trying to make is that just because a term in a formula has the same dimensions as a term in another formula does NOT imply that they originate from consideration of the same underlying physical effect.

Also, I don't think you know what the hell you're talking about. You seem to imply that the idea of an attractive force between two bodies is rubbish, and justify it by developing an almost totally incomprehensible argument. *I* object because (a) PR is not a dumping ground for the half-baked conjectures of failed physical theorists and (b) Feynman was, among many other remarkable attributes, a profound thinker and gifted communicator. Notwithstanding any other qualities the man possessed, it is plainly evident that you are no Richard Feynman.

I am not implying that a pull by every particle... etc is rubbish, I am quoting Feynman who dismissed the very idea, as have many other prominent physicists. In clinging to that discredited concept, you would seem to be a long way behind the times.

Me and the rest of humanity, you mean.

'an energyless pull'

I think this is the basis of the problem - gravity is a pulling force, but it is not energyless. A gravitational does have an associated energy, gravitational potential energy, just as an electromagnetic field is associated with a potential difference in voltages. Both share common features like iso-countours and acceleration of particles towards lower energy positions, thus giving the particles kinetic energy. If you look at weak and strong nuclear forces you find this sort of thing, albeit in the weird and wonderful world of subatomic particles.

Inverse square rules aren't 'stolen' to fill a gap if they are already evident in nature. If something follows the 1/sqrt(x) rule then it will always have done and always will do, even if Newton was the first to notice that the rule applies to non-superheavy objects at >>c speeds.

Oh and even if all this ranting were valid, it still isn't suitable for the h2g2 Edited Guide.

Alex

>>c speeds.
-->
<<c speeds.

...or Gnomon and FM will hunt me down and lecture me.

Are you and another Scout going to put this entry out of our misery?

All right in theory Alex, but where's the physical evidence?

FM Yes!

No need, FM, this is clearly no platform for serious discussion

Anyone following FM's review of my entry may have been puzzled by two contrary statements:

1. the inverse square ratio occurs frequently in mathematical analysis, and no significance can be attached to the occasional recurrence of it.
(I myself described them as perhaps fortuitous, which means much the same)

2. Newton's discovery of a close correlation in the effects of gravity in this ratio by the Sun and the Earth justified his claim that they were related by a common force.
(which is not in dispute)

On Newton's own admission, however, describing the force as a pull was just conjecture based on the still current belief in Aristotle's theory, as his equation gave no hint of the nature of it.

The difference between his and Hooke's use of the inverse square ratio in relation to gravity was that the `d' in Newton's referred to distance (as in Kepler's law) and to diameter in Hooke's, and this is reflected in the difference between an internal and an external force. Galileo's argument convinced Hooke and through him Newton later that the force was external.

Nothing that has been said by contributors to this conversation takes notice of this central point. The rest of my entry hinges on this.

Perhaps it's because we don't understand what point you're trying to make. If only for this very reason, this is the WRIONG PLACE for such writing.

Sorry if it was all too deep for you