Can someone give me a good plausible answer

[Ian]

1/. I have calculated the ratio between gravitational and electric forces in atoms and it is ~ 2x10^39.

2/. I have calculated the value "velocity of light squared / permitivity of vacuum squared" and it is exactly half the value of 1 above.

Why the similarity?

 

[ZapperZ]

1/. I have calculated the ratio between gravitational and electric forces in atoms and it is ~ 2x10^39.

2/. I have calculated the value "velocity of light squared / permitivity of vacuum squared" and it is exactly half the value of 1 above.

Why the similarity?

1. I'm skeptical. How exactly did you find this? You have to make SOME assumptions somewhere (as in at what distance did you calculate each of them, and that an electron actually is in a particular location, which would not work with QM). And in making such assumptions, you are already making an approximation.

2. Unlike #1, this ratio is NOT dimensionless. So how can you compare the two?

Without you showing what you have done, there's no way to know why you accidentally got such a thing.

Zz.

 

[russ_watters]

3. "Exactly"? You have only one significant figure there!

Look at enough numbers and you will find coincidences much more interesting than this.

 

[Loren Booda]

Although "Big Number" comparisons are not known for their precision so much as their accuracy, they must be of similar dimensions to establish any correlation. One could hypothetically (and erroneously) create arbitrary systems of measurement to make correlations between numbers with any combination of units.

Here are results you may wish to digest: http://www.google.com/search?hl=en&q=%22big+numbers%22+Dirac&btnG=Search

 

[capnahab]

I think that Mr. Watters is correct about the coincidence. When I used to work with radar in the Navy the number 1.414 microseconds would be a constant in determining range. I always thought it was odd that 1.414 is the square root of two but that was only a coincidence.

 

[rbj]

1. I'm skeptical. How exactly did you find this? You have to make SOME assumptions somewhere (as in at what distance did you calculate each of them, and that an electron actually is in a particular location, which would not work with QM). And in making such assumptions, you are already making an approximation.

does it really matter what the distance is? they're both inverse-square. the ratio of forces are the same at different distances.

that 10^-39 is a common figure we see all the time. it's why they commonly say that gravity is by far the weakest of the fundamental interactions. but being a Planckian Unitarian, i would say that the ratio of forces is so disparate because, while the Elementary Charge is in the same ballpark as the Planck Charge, the mass of any of those particles is far, far less than the Planck Mass. that's why gravitational forces are so much smaller than the EM forces.

 

[ZapperZ]

does it really matter what the distance is? they're both inverse-square. the ratio of forces are the same at different distances.

Ah, but it does!

Depending on what atom you are using, there's something called SCREENING. This is where the outer shell electrons are screened from the nucleus by the inner shell electrons. So yes, it DOES make a difference. That is why I also asked what kind of ASSUMPTIONS that were made in deriving such numbers. If you ignore QM completely, then wouldn't that in itself ring a very loud bell in your head?

Zz.

 

[rbj]

Ah, but it does!

Depending on what atom you are using, there's something called SCREENING. This is where the outer shell electrons are screened from the nucleus by the inner shell electrons. So yes, it DOES make a difference. That is why I also asked what kind of ASSUMPTIONS that were made in deriving such numbers. If you ignore QM completely, then wouldn't that in itself ring a very loud bell in your head?

assuming both particles are charged ( +/-e ), does it make so much a difference that the EM forces (or the effect of the EM potential energies in the QM solution) do not completely overwelm the gravitational forces (or the effect of the gravitational potential energies in the QM solution) by a factor of somewhere around 10³⁹?

it's not an exact ratio, ignoring QM, but that ratio of around 10³⁹ is commonly cited in the lit as the ratio of EM over gravity for a pair of charged elementary particles. doesn't that ballpark figure come from just the two inverse-square relations using the known charge and known masses of the particles?

 

[ZapperZ]

assuming both particles are charged ( +/-e ), does it make so much a difference that the EM forces (or the effect of the EM potential energies in the QM solution) do not completely overwelm the gravitational forces (or the effect of the gravitational potential energies in the QM solution) by a factor of somewhere around 10³⁹?

it's not an exact ratio, ignoring QM, but that ratio of around 10³⁹ is commonly cited in the lit as the ratio of EM over gravity for a pair of charged elementary particles. doesn't that ballpark figure come from just the two inverse-square relations using the known charge and known masses of the particles?

Er.. we're not arguing about the forces between 2 charged particles. If we are, I wouldn't have asked about the assumptions about the atom. Please read the OP. He claimed that he "... calculated the ratio between gravitational and electric forces in atoms.."

Zz.

 

[rbj]

Er.. we're not arguing about the forces between 2 charged particles. If we are, I wouldn't have asked about the assumptions about the atom. Please read the OP. He claimed that he "... calculated the ratio between gravitational and electric forces in atoms.."

i guess i was thinking that the gravitational and electric forces in atoms were the gravitational and electric forces between the constituent particles inside the atoms.

dunno what else it would be.

 

[Shooting Star]

I think he has calculated the ratio of the electrical to the gravitational forces between a proton and an electron, which is about 4.4*10^40. (A Hydrogen atom!)

(As a matter of scientific history, the existence of such a high dimensionless number was interpreted by many early scientists, like Eddington and Jeans, to be equal to the number of particles in the Universe.)

 

[Ian]

Shooting star is right, I did use the Hydrogen atom, but only because it is the simplest.
What I am getting at is that the velocity of light (in vacuo) slows as gravitational potential increases (shapiro time delay).
We can calculate the velocity of light from the permitivity and permeability of a vacuum and therefore the magnitude of permitivity in vacuo must change also if the velocity of light changes.
This means that if we measure the velocity of light at the Earth's surface and obtain the value we know, and then measure the velocity of light, say, at the neutral point between sun and earth, it must be greater than we observe here on the earth.
This all points to the possibility that matter moves a little slower than we think (calculate) as gravitational potential decreases, and I wonder if there might be an answer here for the pioneer anomaly.
I won't go into how I came across what you call "coincidence", I got censured for that once already and only have one life left.

 

[ZapperZ]

Shooting star is right, I did use the Hydrogen atom, but only because it is the simplest.

See, that is why I asked what scenario you were using to get your answer. When you simply, without qualification, wave your hands and said you did this for "an atom", that is horribly too generic for you to get away with that. In doing this, what you have done is assume a classical scenario.

What I am getting at is that the velocity of light (in vacuo) slows as gravitational potential increases (shapiro time delay).

Er.. hang on. This time delay is the delay in light traveling near a gravitational body when compared to when a body isn't there. It is due to how gravity affects spacetime within the vicinity of that object. In naive terms, it means that light has to travel a "longer spacetime distance". It has nothing to do with light being "slowed down".

You may want to go back and double check this, because if this is the whole premise that you are building this on, then it might be faulty.

Zz.

 

[Ian]

Zapper,
What on Earth makes you think that light gets forced around a corner? If it did it would miss the target at the other end and the radar signal would never return! Sometimes you really ought to ignore what the math makes you think and listen to your common sense.
Look, what you have said is that space-time gets "stretched" to a longer length by matter and therefore you are back in the realm of a sort of 'aether' which you also say is non-existent.
I mean, you simply cannot change the length of something that you say is not there, and besides, you look at light and call it e-m radiation even though it appears to pass really close to the immensely strong electrical & magnetic fields of the sun and nothing happens to it.
I just look at things in a different and more interesting manner to you that's all, like you say 'Saturns Rings' and I say 'Balmer/Paschen series lines'. But your petato ain't like my potato, is it?

 

[ZapperZ]

Zapper,
What on Earth makes you think that light gets forced around a corner? If it did it would miss the target at the other end and the radar signal would never return! Sometimes you really ought to ignore what the math makes you think and listen to your common sense.
Look, what you have said is that space-time gets "stretched" to a longer length by matter and therefore you are back in the realm of a sort of 'aether' which you also say is non-existent.
I mean, you simply cannot change the length of something that you say is not there, and besides, you look at light and call it e-m radiation even though it appears to pass really close to the immensely strong electrical & magnetic fields of the sun and nothing happens to it.
I just look at things in a different and more interesting manner to you that's all, like you say 'Saturns Rings' and I say 'Balmer/Paschen series lines'. But your petato ain't like my potato, is it?

That is why I said it was a naive description!

Your insistence that this is a "time delay" that is similar to a photon slowing down isn't valid either. No where in GR is there any mention of such a thing. Would you like to point out exactly where this "time delay" has been associated with a photon slowing down? If it has, all of our measurement of the positions of various celestial bodies are wrong!

Zz.

 

[rewebster]

should this thread (now) be moved to the 'relativity' area?

 

[DaveC426913]

Sometimes you really ought to ignore what the math makes you think and listen to your common sense.

Go figure. A real world application of truthiness

- something that a person claims to know intuitively or "from the gut" without regard to evidence, logic, intellectual examination, or actual facts.

 

[Ian]

Hey ZapperZ

You and me will never see I to I, Eye don't see photons as reality

[personal theories deleted, and Zapper'Z's name corrected to correct spelling]

 

[Mentz114]

Ian said:

...if the velocity of light changes

It never changes for local observers. See many threads in this forum.

...my knowledge on the matter however limited

Very limited I'd say. You should study GR before coming out with rubbish like

If it did it would miss the target at the other end and the radar signal would never return! Sometimes you really ought to ignore what the math makes you think and listen to your common sense.

 

[pervect]

As far as GR goes, note that the speed of light near a massive body, when measured using local clocks and rulers, is always equal to 'c'.

See for instance the sci.physics.faq on this topic, which I'll quote in part:

Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory. In the 1920 book "Relativity: the special and general theory" he wrote: . . . according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity.

The problem here comes from the fact that speed is a coordinate-dependent quantity, and is therefore somewhat ambiguous. To determine speed (distance moved/time taken) you must first choose some standards of distance and time, and different choices can give different answers. This is already true in special relativity: if you measure the speed of light in an accelerating reference frame, the answer will, in general, differ from c.

In special relativity, the speed of light is constant when measured in any inertial frame. In general relativity, the appropriate generalisation is that the speed of light is constant in any freely falling reference frame (in a region small enough that tidal effects can be neglected). In this passage, Einstein is not talking about a freely falling frame, but rather about a frame at rest relative to a source of gravity. In such a frame, the speed of light can differ from c, basically because of the effect of gravity (spacetime curvature) on clocks and rulers.In general relativity, the appropriate generalization is that the speed of light is constant in any freely falling reference frame (in a region small enough that tidal effects can be neglected). In this passage, Einstein is not talking about a freely falling frame, but rather about a frame at rest relative to a source of gravity. In such a frame, the speed of light can differ from c, basically because of the effect of gravity (spacetime curvature) on clocks and rulers.

So the idea that the speed of light changes near a massive body is not necessarily totally wrong, but involves ambiguties as to "which clock" and "which ruler" to use to measure the speed of light with, ambiguities associated with the curvature of space-time. Gravitational time dilation, for instance, says (losely speaking) that clocks at different heights tick at different rates. It should therefore not be surprising that the speed of light is constant only when one picks the "correct" clock and ruler combo. Which pair is that? It is the pair of clocks and rulers associated with a local, free-falling observer at the location in question - what I call "local clocks" and "local rulers".

Using these clocks and rulers, the speed of light will always be equal to 'c'.

Note that this has absolutely nothing to do with the ratio of electromagnetic force to gravitational force as far as I can tell.

Also a general reminder: we do not allow discussion of personal theories here on PF.

 

[DaveC426913]

You and me will never see I to I, Eye don't see photons as reality

When did physics become a field of personal preference?

 

[rbj]

... It should therefore not be surprising that the speed of light is constant only when one picks the "correct" clock and ruler combo. Which pair is that? It is the pair of clocks and rulers associated with a local, free-falling observer at the location in question - what I call "local clocks" and "local rulers". ...

thanks for putting it that way, pervect. and for including the faq segment. i like conciseness.one thing... (this is for my own education) ... your free-falling observer could be at the apogee of a sort of parabolic trajectory and standing on the edge of a cliff immediately next to this apogee would be another observer and, for this instance of time neither observer sees the other's time being dilated (or rulers being contracted), so they would both measure c to be the same, no?

 

[George Jones]

one thing... (this is for my own education) ... your free-falling observer could be at the apogee of a sort of parabolic trajectory and standing on the edge of a cliff immediately next to this apogee would be another observer and, for this instance of time neither observer sees the other's time being dilated (or rulers being contracted), so they would both measure c to be the same, no?

All observers, freely falling or not, in relative motion or not, coincident at a spacetime event measure the local speed of light to be c.

 

[rbj]

So the idea that the speed of light changes near a massive body is not necessarily totally wrong, but involves ambiguties ...
It should therefore not be surprising that the speed of light is constant only when one picks the "correct" clock and ruler combo. Which pair is that? It is the pair of clocks and rulers associated with a local, free-falling observer at the location in question - what I call "local clocks" and "local rulers". ... Using these clocks and rulers, the speed of light will always be equal to 'c'.

All observers, freely falling or not, in relative motion or not, coincident at a spacetime event measure the local speed of light to be c.

i was thinking that but was sort of trying to get a grip on the caveat(s) that pervect brought up.

 

[pervect]

All observers, freely falling or not, in relative motion or not, coincident at a spacetime event measure the local speed of light to be c.

As long as they use short enough rulers (in the case of accelerating observer). Wherever you are, wherever you go, the speed of light is always "c" right where you are, but you may think that it's different somewhere else. When you actually go there, though, and measure it, you find that it's still 'c'.

In order to even measure the speed of light, you need to take along a physical measuring bar, like the one in Paris. The SI definition of the meter defines the speed of light to be a constant, in fact, so you have to use the old, outdated, previous defintion of the meter as a replica of the satandard meter bar to be able to measure the speed of light at all.

 

[rbj]

In order to even measure the speed of light, you need to take along a physical measuring bar, like the one in Paris. The [current] SI definition of the meter defines the speed of light to be a constant, in fact, so you have to use the old, outdated, previous defintion of the meter as a replica of the satandard meter bar to be able to measure the speed of light at all.

yup. we would revert back to the pre-1960 definition of the meter to even meaningfully measure c to be anything other than 299792458 m/s, and only then this physical hypothesis that c is the same for everyone would be falsifiable. so then what would it mean if someone measured it at 299792457 m/s? assuming we don't attribute it to some atoms getting shaved off the meter stick (between the scratch marks) or some other experimental error, what would it mean if, using the pre-1960 meter, people measured c to be something else? in my opinion, the salient meaning is one or both of two dimensionless parameters had changed. either the number of Planck lengths in the meter (as defined) changed (and if the meter stick is a "good" meter stick and lost or gained no Pt or Ir atoms, then the number of Planck lengths in the size of Pt or Ir atom or maybe the number of Planck lengths per Bohr radius changed) or the number of Planck times per second changed and those would be the meaningful changed parameters.

i'll go out on a little limb here and speculate: in my opinion, there is no physics as to why c = 299792458 m/s. it is not a physically meaningful question to ask "why is c = 299792458 m/s ?" the meaningful questions to ask are "why are there 6.187154 x 10³⁴ Planck lengths in a meter?" and "why are there 1.854861 x 10⁴³ Planck times in a second?" and the answers would be sort of historical or anthropocentric ones. we chose the meter to be a length about as big as we are and we chose a second to be a duration of time about as short as we would commonly experience different events. for the meter, the question would break down to why are there about 10²⁵ Planck lengths in the size of atoms (a question for physicists), why there are about 10⁵ atoms in the length of a biological cell (a question for microbiologists), and why there are about 10⁵ cells in the length of a sentient being like us (a question for some other biologists). if we answer those questions, we have some idea for why the meter is as big (relative to Planck) as it is. doing similarly for the second, from those two answers (and from the defined fact that c is always 1 Planck length per Planck time), we have the answer to why c is about 3 x 10⁸ m/s which is really just an anthropocentric concern that Nature doesn't give a rat's ass about.

i know that this is more philosophical than physics, but i think the core physical reality from Nature is that, for all of these fundamental interactions (whether I'm waving some electrically charged object around that is perturbing your charged object or if I'm waving some massive object around that is perturbing your massive object or some other interaction) that exist and have effect even across a vacuum (a true vacuum that has nothing in it as a medium to mediate any force) that reality conceivable has this choice of whether or not the speed of propagation of these interactions (across space from one location to another) is finite or infinite. the physics is that this speed is finite, not infinite. doesn't matter what the finite speed is. it is not meaningful that there be different speeds, from the POV of Nature who doesn't give a rat's ass what units we or the aliens on the planet Zog choose to use. whatever that finite speed is, it defines a constraint on the scaling of length and time so that all other speeds are meaningfully measured against this finite speed of propagation of these ostensibly "instantaneous" actions. logically, it makes no sense that c vary. it's not just light (E&M), but it's the finite speed of any fundamental interaction.

as long as c is finite, it simply is what it is, a primary quantity to measure (or simply perceive) everything else against. same thing for G and \hbar and 4 \pi \epsilon_0. Nature has not set those to any particular quantity except "finite". and then from those finite and singular values (that we may as well call unity) everything else in the universe is built and perceived. (again, i personally think it's more natural to normalize 4 \pi G and \epsilon_0 rather than what Planck and the electrostatic CGS units do, so that Gauss's Law would have no funky scaling coefficient in it and the quantities of "flux density" and "field strength" would be the same and maybe we could equate the concepts.)

anyway pervect, i know PF isn't the forum to spout personal theories, but I'm taking a stab at it. see what comes out.

 

[rewebster]

this is more a comment on rbj's post--

I think thinking about physics (the things that aren't known 'definitely') is philosophy--which is what you're doing here (thinking, and is a positive 'thing' toward understanding)---(and, really what a lot of the posts are--too bad some (posts) are not researched just even a little bit, but that's a nice thing, too, in some ways as we're all on a Bell shaped curve.).

(using physics is what some do (teaching, etc.) and try to differentiate it and say, " 'why' isn't used by physicists--which seems to be a cop out once in a while for saying "I/we don't know yet" but still may want to help by supplying knowledge of what is accepted and introducing that information.)

One other post put it, in a way of saying that what is being said is, that it is assumed that some previous knowledged is known, but, to me, it's more of what is 'accepted' information than what is 'known' (as in an application of what is known and accepted).

As far as the post goes, (and I'm not even guessing of what his preliminary starting formulas were) but it may be that when you start out using interrelated equations, using the same starting equivalents, that answers will look similar, as rbj said in post #6.

 

[Ian]

Why do physicists consider that the vacuum between the Earth and the sun is different to the vacuum between a nucleus and an electron?
They must think there is a difference because theory treats the two cases differently. What we observe when light passes from air to water is the same as what happens when light passes from the earth, grazes the solar surface and is reflected by a target beyond the sun.
Accepted theory says that light slows down when passing from air to a denser medium such as water, but accepted theory says that light has to travel a "longer spacetime distance" and has nothing to do with light being "slowed down" in the solar case. This is pure double talk whether you like it or not.

 

[Ian]

DaveC426913,
You really ought to think twice on whether physics is a matter of personal preference! Take a good hard look at the empirical evidence.

 

[pervect]

Why do physicists consider that the vacuum between the Earth and the sun is different to the vacuum between a nucleus and an electron?

While it is clear that the average speed of light in a medium is lower than 'c', it is not clear that the speed of light between the nucleus and the electron is slower than 'c'.

What we can measure, directly, is the average propagation speed of light (or energy) through a medium. This is a complicated process. If you look up the PF faq on this, you'll see that it involves a process whereby light gets absorbed and converted into lattice vibrations (also called phonons), and then re-emitted or reconverted back into light.

They must think there is a difference because theory treats the two cases differently.

They are simply aware that the process of light being transmitted through a medium is a lot more complicated than you think it is. Unfortunately, it appears that when we try an explain why things are more complicated, you reject this using "conspiracy theory" logic

This is pure double talk whether you like it or not.

You appear to have a well-entrenched world-view which is ultimately incompatible with both relativity as it is understood and practiced, AND also with quantum mechanics. And when people point out some of the oversimplifications with this wolrd-view, you prefer your own simple (but wrong) ideas, and think the more complex ideas must be a deliberate attempt to confuse you, rather than an attempt to enlighten you.

 

[pervect]

i was thinking that but was sort of trying to get a grip on the caveat(s) that pervect brought up.

As long as your distances are short enough, acceleration doesn't really matter, as George points out. I probably overspecified things a bit by stating that the rulers should be in free fall. But on the other hand there's a whole can of worms about "distance in the large" that one can sidestep by this sort of specification. This could probably start a whole new thread, this thread is probably confused enough without hijacking it in that direction.

 

[DaveC426913]

DaveC426913,
You really ought to think twice on whether physics is a matter of personal preference! Take a good hard look at the empirical evidence.

Do please elaborate.

 

[hunarahmad]

Accepted theory says that light slows down when passing from air to a denser medium such as water, but accepted theory says that light has to travel a "longer spacetime distance" and has nothing to do with light being "slowed down" in the solar case. This is pure double talk whether you like it or not.

Nice talking Ian, I'm on your side in this view.

 

[Mentz114]

Ian:

This is pure double talk whether you like it or not.

Physicists only have equations to work with - the 'talk' comes when people interpret the equations. If light takes longer to go from A to B, you have 2 ways it can happen, the path is different or the light slows down. The equations tell us unequivocally that the path is different and the light does not slow down. Should we believe you or the equations ?

 

[rewebster]

From Z's post of Einstein's quote:

"Relativity: the special and general theory" he wrote: . . . according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity."

at least, he (Einstein) considered it an 'assumption' (at the time, anyway)

 

[ZapperZ]

Why do physicists consider that the vacuum between the Earth and the sun is different to the vacuum between a nucleus and an electron?
They must think there is a difference because theory treats the two cases differently. What we observe when light passes from air to water is the same as what happens when light passes from the earth, grazes the solar surface and is reflected by a target beyond the sun.
Accepted theory says that light slows down when passing from air to a denser medium such as water, but accepted theory says that light has to travel a "longer spacetime distance" and has nothing to do with light being "slowed down" in the solar case. This is pure double talk whether you like it or not.

Note that, if you had read our FAQ, you would have noticed that even in a dense medium, the speed of photons do not slow down. This is a common misconception one has when the idea of WHAT is being measured is never considered. "god" is in the details, and this is especially true on when we consider the speed of a light pulse, which is what is commonly measured, and what is measured in a dense medium.

There is no double talk here if one has understood beyond just the superficial level of light transport.

Zz.

 

[rewebster]

z:

'"god" is in the details'

now where (or how) did you get that one?--(I've heard it differently before)-

-that's pretty funny, there, Z, (I like it)

 

[rbj]

As long as your distances are short enough, acceleration doesn't really matter, as George points out. I probably overspecified things a bit by stating that the rulers should be in free fall.

no, no! i thought you were being nicely conservative (which was persuasive to me). certainly, at least for the observer in free-fall, the speed of propagation (EM, whatever) would still be the constant c around a gravitational mass, if we accept the postulates of GR. i got it, and then tried to extrapolate that to the guy standing on the cliff and not in free fall. then applying the equivalence principle again, if it's the same c for the guy standing on the cliff, it's the same c for the guy in the rocket accelerating at the same rate, g.

But on the other hand there's a whole can of worms about "distance in the large" that one can sidestep by this sort of specification. This could probably start a whole new thread, this thread is probably confused enough without hijacking it in that direction.

i just thought that the direction it was in, regarding the OP, was a little icky.