Wednesday 30 January 2008

What On Earth Is Wrong With Gravity?

Did anyone see BBC2's "Horizon" programme yesterday evening where particle physicist and ex D:Ream keyboard player *shrugs*, Dr Brian Cox narrated a documentary on the newly debated inaccuracies within Newtonian gravity and the latest experimentation into Quantum particle acceleration?

(It was better than it sounds, honestly!)

It was interesting to see that much time, money and effort is being spent presently trying to identify the "graviton" - the hypothetical particle that mediates the force of gravity (according to Einstein) - deep within the subatomic world.

Now, Gravity is one of the four fundamental forces within the Universe - the other three being Electromagnetism, and the Strong and Weak Nuclear Forces.

Scientists pretty much uniformally agree that the strongest of these forces is the Strong Nuclear Force BUT that its range of effect is miniscule thereby only having its full force at the subatomic level, binding Protons together in the atomic nucleus.

So much work is going on trying to identify what effect Gravity has on the atomic world when it is already established that the Strong Nuclear Force has no effect in the Macro-materialistic-world we all inhabit, so why can the inverse not also be true.

Gravity depends on mass. F=mg (or Force = Mass x Gravity (9.81 m/s constant)). So whereas the Sun may very well be warping Space-Time and creating this effect we call gravity, this is obviously due to the sheer massiveness of the Sun. At the subatomic level the Gravitational effect will become as insignificant as the Strong Nuclear Force is on material objects.

Now am I being brilliant or idiotic? This is one of those moments where I don't know, so I thought I'd put these thoughts here for my fellow Peakeians (and of course, Tony himself), to add their comments to help me decide.

What do you think?

A Dark Philosopher
Karl L Le Marcs


SM Kovalinsky said...

KARL: I have always thought your brilliance far surpassed any idiocy (only joking -- you ARE brilliant) but I can't seem to grasp the essential question here. Can you perhaps clarify a bit more? I hope that Tony's theory does not hinge on such, or I'll be bested by the Ferryman for sure! *giggle* Perhaps others may grapple with it succesfully. . .

ken said...


The gravitational force exerted between two objects does indeed depend on mass but it also depends on the square of the distance between the two objects:

F = G*m1*m2/r^2

so the incredibly small distances in the subatomic world will tend to increase the gravitational force expontentially.


Hurlyburly said...

Karl, you are without a doubt a complete genius.....

What was the question?

ken said...


I plugged in some numbers and I agree it is odd that scientists are concerned with gravity on the subatomic scale. At least for the proton/electron system of the hydrogen atom, the gravitational force is less than miniscule compared with the force between the earth and the sun. I did not have an accurate feel for the masses/distances in the atom and the distances are not small enough to offset the much smaller masses.

If you are interested, here are the numbers I used:

mass of sun = 2x10^30 kg
mass of earth = 6x10^24 kg
distance = 150x10^9 m

mass of proton = 1.7x10^-27 kg
mass of electron = 9x10^-31 kg
distance (Bohr radius) = 5.3 nm = 5.3x10^-9 m

So, the ratio of (m1 * m2 / r^2) for the two systems is 10^73. A fairly large number :-)

I wonder if they are concerned with proton-proton interaction? Could those distances be small enough to make gravity important?

ken said...

For proton-proton gravitation force in a uranium nucleus, I'm getting a number that is 10^57 times smaller than the force between the sun and earth.

I guess the question is: Is comparing to the sun/earth system reasonable?

What does it mean to say that the Strong Nuclear Force is the strongest of the four fundamental forces? I'm guessing it means that the Strong Force, when computed for proton-proton or proton-electron systems is larger than the force of gravity for the same system. But how much larger? What we need to do is compute the Strong Force for proton-electron or proton-proton systems and then compare with the gravitational force. If it's only 10 or 100 times more, it's still the strongest but gravity would still be interesting.

Anthony Peake said...

This is probably the most intellectually challenging of all our threads thus far. I did watch the programme and I was fascinated (although I found the 'we are all a group of lads on a BBC funded road-trip across the USA' a little irritating). For me the suggestion that the mass of an object warps the space around it a particularly beguiling one. It certainly explains how gravity can seemingly work at a distance and across a vacuum. Although not described in the programme one of the best analogies I am aware of is having a trampoline and placing a heavy object on its surface. This object 'warps' the surface by pushing down on it. This then effects any objects nearby on the surface in that the depression brought about by the object's weight (mass) makes smaller (less mass) objects role into the depression. This can be observed as 'attraction' but it is not - it is brought about by the warping of the surface of the trampoline.

As an aside I was particularly intetersted in the section of the programme on 'gravitational lensing' that brought about a single, very distant galaxy, being viewed as two adjacent identical objects when viewed from Earth - the dual image being brought about when light-waves are warped as they go round a super-dense object such as a neutron star or a black hole. In the first version of ITLAD I discussed this in some detail. I may place a posting on this later.

Anthony Peake said...

Also in the first book I had a whole section on the concept known as the "Anthropic Cosmological Principle". In its 'strong' form - known by the acronym SAP or 'Strong Anthropic Principle' - it applies the implications of the Copenhagen Interpretation (Universe needs an observer to come into existence)to the first few milliseconds of the Big Bang.

One of the crucial elements of this theory is the strength of the weak force that Karl mentions in his post. This influences how much hydrogen was processed into helium in the Big Bang. It requires a rather precise fine-tuning to avoid a runaway in one direction or the other - make the force slightly stronger and no helium would have been produced; make it slightly weaker and nearly ALL the baryons would have been converted into helium in the Big Bang. A universe in which stars were initially made only of hydrogen might not be so very different from our own; but if all the stars were originally composed of helium, they would have burnt out more quickly, perhaps not giving life time to evolve on any planets that formed (if life can indeed develop without hydrogen present to form water). The condition that some stars go through a supernova phase (triggered by a neutrino- boosted shock) is essentially the same as the condition that there be an interesting amount of cosmological helium production.

The weak force seems to be just about as weak as it can be in order to avoid all the original hydrogen being converted into helium. Supernovae might still work (exploding by a different mechanism) if the force were a little stronger, but if the force were weaker the neutrinos could not drive any kind of explosion; the Universe would be even more comfortably by hydrogen by hydrogen if the force were a little stronger; but the window of opportunity for a universe in which there is SOME helium AND exploding supernovae, is very narrow. So in simple terms, the weak force has to be the strength it is in order to have observers such as ourselves observe it - back to Copenhagen and the role of the observer!

Karl Le Marcs said...
This comment has been removed by the author.
Karl Le Marcs said...

Good comments by everyone - thank you. This is all just a snapshot of the kind of thing my mind goes over and over at all times of the day - along with some gags obviously.
And don't even get me on to the "expanding" universe debate.............

Karl Le Marcs said...

To Ken and all posters who replied (and especially Susan Marie for being so sweet - *MWAH*)
Force = Gravitational Constant multiplied by the difference in Mass of any two objects upon which Gravity is being exerted, divided by the square of their distance.
F=G M1 M2
Now, in the material world this means obviously that Gravity has a massive (no pun intended) effect given the masses involved. So at the cosmic level of Suns, Super Massive Black Holes and the like Gravity is CONSIDERABLE.
However, at the atomic level, as the masses of individual protons and electrons becomes negligible, so does the effect of Gravity regardless of the distance between the objects.
This is why i question all the efforts to find the "Graviton" at atomic level when it has never even been found at the Macro Cosmic level.
And surely, as the Strong Nuclear Force is so fundamentally powerful to negate the electromagnetic force within the Nucleus but has NO effect in the material world owing to its huge power only being felt as miniscule distances, I postulate that the inverse is true and that Gravity may only be a force at the macro level and have no or negligible effect at the atom one.