Quantum gravity physics based on facts, giving checkable predictions

## Friday, November 11, 2005

Gravity mechanism: explosion analogy

Air based explosions

First consider a sphere of 1-m radius at sea level. The normal air pressure acting outward at the 1- radius is 101,000 Pascals, and the spherical surface area is 4Pi or 12.6 square metres. The outward force is therefore F = PA = 101,000 x 12.6 = 1,270,000 Newtons. Now this sphere of compressed air doesn’t explode outward at sea level, because the air beyond it is at the same pressure. The inward force cancels this outward force.

Second, consider an explosion. In an explosion in the air, the pressure at the boundary or ‘shock front’ is greater than normal atmospheric pressure. The excess pressure is normally called ‘overpressure’. Thus the outward force in an explosion is greater than the inward force from the surrounding ambient pressure air! This is why an explosion occurs.

But consider the original problem again: Newton’s 3rd law says that every action has an equal and opposite reaction. What is the reaction to the outward force due to the excess pressure in an explosion? Initially, before a vacuum develops, the reaction is simply the fact that the shock wave going north has an equal and opposite reaction by virtue of the part of the shock wave going south.

However, within seconds of an air burst, the out rushing air creates a nearly perfect vacuum at ground zero. This vacuum is a barrier preventing the force reaction from being carried by the opposite-directed outward shock wave. What happens then is that the reaction force occurs behind the shock front, as a long ‘under pressure’ phase develops, with wind blowing towards ground zero. This has in inward directed pressure and force, and is the reaction to the outward force of the blast wave.

The big bang: an explosion in the gauge-boson filled vacuum of space

Now look again at the big picture: the big bang. We know space is flooded with gauge bosons going at light speed and causing forces, because quantum field theory works well and is based on the concept that a force is caused by the exchange of gauge bosons, such as virtual photons between charges for electromagnetic forces. There are high-energy Higgs bosons in electroweak unification that cause inertial mass, and since Einstein’s equivalence principle of general relativity says inertial and gravitational masses are identical, the Higgs bosons may provide the physical mechanism of gravity.

In the big bang we also we see speeds increasing with distances, but really they are varying with time past. This is because when we see galaxies we don’t see them at a fixed distance (they are receding from us all the time), but at a fixed time in the chronology of the big bang! Actually there is a variation with both distance and time past, and we see recession velocities at bigger distances but also further back in time. (We cannot see to distance x without looking back in time by the amount t = x/c.) However, since the gravity force is carried at light speed, just like the visible light that carries the information on red shift, what matters regarding gravity is what we see. The linear variation of speed with time implies a fixed acceleration outward, equal to the speed of light divided by the age of the universe, which comes to 6 x 10^-10 m/s^2.

This tiny acceleration, when multiplied by the mass of the receding matter in the big bang, gives a massive outward force of F=ma = ~ 7 x 10^43 Newtons. This can’t be right, you think, because where is the reaction, the equal inward force implied by Newton’s 3rd law? GRAVITY! The gauge bosons form a perfect fluid, physically causing a drag-type directional-compression (the contraction term of general relativity and special relativity for gravity and for inertial motion, respectively) without any viscosity, since the gauge bosons or Higgs field only resist accelerations! The bosons flow around moving subatomic particles, filling in the volume they vacate. If the subatomic particles appear to accelerate in outward in the big bang from our perspective, the spacetime fabric bosons appear to accelerate the other way, predicting gravity by pushing things together: http://nigelcook0.tripod.com/

At 4:59 PM,  Kevin Brunt said...

Nigel,

You have omitted an important step - the situation where the air pressure around the 1m sphere is instantaneously reduced. (This cannot happen in reality, but can be envisaged and discussed.)

What happens is that the motion of some of the gas molecules within the boundardy of the sphere takes them outside, carrying kinetic energy with them. This would happen with equal pressures on each side, but with the reduced external pressure the number of molecules moving inward is reduced.

This means that there is a net transfer of kinetic energy across the boundary. This is work done, and although it is difficult to define exactly what has moved and how far, the formula work=force.distance applies. However it applies both to the increase in energy outside and the increase in energy inside. There are therefore two forces, one acting with the motion and one acting against the motions. These forces and only these forces are Newton's 3rd Law.

Once the molecules close to the boundary start moving out there is a reduction in the pressure just inside the boundary, so that there will be a net outward movement of the moleules just further in - and so on right into the centre of the sphere. Once the motion has started it will continue, so a pressure gradient propagates into the centre at a rate related to the velocity of the molecules (which turns out to be the speed of sound.)

Although this process is happening over the whole surface, there is no "3rd Law" element to what is happening at opposite points, because they are "separated" by the time it takes for sound to cross the sphere.

Note that until there is a net flow molecules out through the boundary, the pressure within the sphere is equal throughout.

This is where your "explosion" is getting into deep water. You have started by creating a pressure inequality. Furthermore, if you have a "shock front" you have created the inequality in such a way as to cause it to propagate at a velocity in excess of the speed of sound for the medium.

In your air burst the "north" and "south" shock waves exist because of the symmetry of the situation. Although the 3rd Law applies (because it always does!) you are trying to use it in an inappropriate way. The analysis of what is going on should be possible by considering an arbitrary radius from the centre of the sphere.

If a vacuum forms at the centre, it is due to the specific conditions involved. It is a result of the previous pressure inequalities and is merely an "overshoot" due to the "dynamics", ie momentum and kinetic energy. Since there is now a reverse pressure gradient, there will be net motion of molecules back towards the centre once the overfast ones moving out get out of the way. It is very much the same sort of thing as the splash where you drop something into water, when the water is caused to moved faster than a water wave.

I'm afraid that your "force reactions" and "reaction forces" simply don't make sense. You seem to have left out several of the connecting steps in the description, with the result that you have an argument involving force, energy and velocity without the proper causal connections.

Your 'big bang' discussion also has gaps. In particular, if objects further away are moving faster than closer one because of when we are seeing them rather than where we are seeing them, it follows that objects are slowing down rather than speeding up, so that there is a force acting inwards against their motion. While it would be necessary to explain that force, there is no mystery about its 3rd Law reaction. If the force is acting on an object, reducing its kinetic energy, the reaction is merely the object acting on the process creating the force to transfer energy into it!

It looks to me as if this action-reaction business is because you're floundering around trying to fix your initial error in the sign of the acceleration.

At 2:49 AM,  nige said...

The sound wave has an outward overpressure followed by an equal under-pressure phase, giving an outward force and equal-and-opposite inward reaction that allows music to propagate. Nobody hears the force of music on the eardrum (but they ‘hear’ talk about the equation of a sound ‘wave’!). The outward force phase of a sound wave is like the forward thrust of a rocket in air, while the inward force of sound that follows is like the backward thrust of exhaust. ‘String theory’ cranks suppress all evidence of the outward force of an explosion, because its equal inward reaction by the third law of motion in the case of the big bang is the force of gravity, as proved on the
Feynman gravity blog

How about understanding explosions before dealing with the big bang and gravity? Or is real physics too arcane?

At 2:50 AM,  nige said...

WHOOPS, I mean proved here:

(This has been updated today, 13 Nov 05)

At 1:13 PM,  Kevin Brunt said...

Nigel,

Consider the diaphragm of a loudspeaker, and the velocity of the gas molecules impinging on it; specifically the component of the velocity perpendicular to the plane of the diaphragm.

With the diaphragm at rest, the molecules bounce off it with their initial velocities reversed - the average velocity of the bounced molecules will be the same as that of the approaching molecules. To reverse the motion of the molecules a force is required. This is exerted by the diaphragm on the molecules. Newton's 3rd Law says that there must be a reaction, which is the force exerted by the molecules on the diaphragm. Equally, you could say that the molecules are exerting the force, and the diaphragm is exerting the the reaction. It is entirely a matter of viewpoint.

Now move the diaphragm forward. Once it has moved and come to a stop the equal approaching and receding velocity situation applies. However, while the diaphragm is moving it imparts additional velocity to the bounced molecules. One way of looking at it is that we have placed a new surface for the molecules to bounce off ahead of the original one, and have dumped the molecules from between the surfaces back in front, having imparted to them a additional velocity away from the surface.

It should be clear that what we have is a volume containing extra molecules moving at an increased velocity. This is an overpressure, and it is clearly moving away from the diapgragm. However, behind this overpressure there is no underpressure - as long as the diaphragm remains in its forward position the equal forward and reverse velocity scenario applies.

It is only when the diaphragm retreats, at which point the bounce velocities are reduced and the extra volume has to be filled, that the pressure is reduced. Thus the underpressure phase is not a direct result of the overpressure phase, but is a result of the cyclic nature of the motion of the diaphragm.

I've omitted the implications of collisions between the molecules moving in opposite directions. In the overpressure phase, the outgoing molecules have more momentum (on average) so that when they collide with inbound molecules, they will (on average) slow them down. This will tend to reduce the inbound velocity somewhat. It is related to the disparity in momentum, so for loudspeakers (where the overpressure is small) and for nuclear fireballs (where the overpressure is enormous) the effect is large. It is a conservation of momentum issue, not a 3rd Law one (except in that there is acceleration, so there is force, so there must be a reaction,) and the inward force does not "follow" the outward one - it is the consequential reduction in the inward velocity that is seen to "follow".

The "outward force" of an explosion is the initial conversion of stored energy into kinetic energy. After that what is "outward" is motion (and momentum, etc.) The forces acting are due to the processes abstracting energy. The "inward force" abstracts the energy; the "outward force" is the 3rd Law reaction delivering the energy.