What is the Reason Behind the Speed of Light?

[rogerp]

Hi

I'm a confused layman, and was hoping to get some answers to the question: why is the speed of light? That's not a typo - I mean, why is it what it is? The questions below are specific ways to ask essentially the same question.

1. The speed of light is 299,792,458 metres per second. What stops it from reaching 299,792,459 m/s?

2. If light has no mass, what stops it from having infinite speed? What’s slowing it down?

3. Light from the sun takes 8 minutes 24 seconds to reach the Earth – why can’t it get here faster?

Thanks in advance.

.

 

[HallsofIvy]

I'm not sure what your question is. Is "why is the speed of light that particular number and not some other number?"

The speed of light happens to be that number because of a particular choice of the length of a meter- which is completely arbitrary. If you measure distance in km and time in hours, or distance in feet and time in minutes, you would get some other number. Nothing very deep about that!

 

[jtbell]

The Universe has a fundamental symmetry, called Lorentz symmetry, which causes to exist an asymptotic upper limit on all relative speeds. Objects with mass can never reach that upper limit. Massless objects (such as photons) must travel at that limiting speed, and no other. These are consequences of the mathematics of Lorentz symmetry.

This obviously begs the question, "why does the universe have Lorentz symmetry?" Nobody knows. (Or at least there is no generally accepted answer, as far as I know.) This is the ultimate answer to all "why?" questions in physics, by the way. The answer to any "why?" question leads to another "why?" question, and ultimately we always come to one that we cannot answer in the context of physics, at least not yet.

 

[Gib Z]

1. The speed of light is 299,792,458 metres per second. What stops it from reaching 299,792,459 m/s?

2. If light has no mass, what stops it from having infinite speed? What’s slowing it down?

3. Light from the sun takes 8 minutes 24 seconds to reach the Earth – why can’t it get here faster?



.

1. We defined light to go that distance in 1 second. If somehow miraculously, and it cant, light went faster, that new distance is still 299,792,458m.

2. Nothings "slowing" it down, that's the fastest it can go. It can't have an infinite speed because the fabric of spacetime, and infact everything, has 2 quantities. Permittivity and Permeability. The former is sort of a measure of how well Electric fields transmit in the material, in this case spacetime. The latter is a similar measure, except of magnetic fields. Both these quantities must be finite, by definition. Something can't transmit something infinity well.

Since Light is just magnetic and electric fields traveling through space, the speed must be finite as the ability for the spacetime to transmit it is finite.

It may interest you that this equation holds:

$$c= \frac {1} {\sqrt{\varepsilon_0\mu_0}}$$

Where c is the speed of light, episilon_0 is the permittivity of free space, and mu_0 is the permeability.

3. As I said, light can't go faster than spacetime allows it to. To find out why spacetime has the values of permeability and permittivity that it does, you would need to do some serious study into both physics and mathematics so you can Understand Maxwells Famous Equation and Einsteins General Relativity.

 

[Gib Z]

Didn't you read my post >.<
EDIT: or jtbells...he's got it in the first line lol.

 

[rogerp]

Yes, thanks Gib , I did! That's why I deleted my reply.

May I ask one more question?

I'm really interested by this idea of the Permittivity and Permeability of the fabric of spacetime. But am I right that this is a circular theory - i.e. that the speed of light is defined by the Permittivity and Permeability of spacetime, and the Permittivity and Permeability of spacetime are defined by the speed of light?

I'm not sure that physics is explaining here so much as describing. I suspect this question may have been answered by the second paragraph in jtbell's post.

Can I also just thank you both for your answers.

.

 

[Gib Z]

It is somewhat circular, good spot :D

However, only in its definitions. I only when I say "only" you're thinking I'm quite an idiot :) You see, Permittivity and Permeability can be experimentally measured!

The Permittivity and Permeability of Space are defined exactly, as a consequence of the mathematical relation I posted previously. However, one can experimentally measure Permittivity and Permeability without measuring the speed of light, and use the equation to find the speed of light. Measurements are not definitions, but they do show us approximations and that the speed of light, what ever it is, in finite.

 

[rogerp]

Gib, thanks again - believe me, I think you're very, very far from an idiot; after all, you just explained some very difficult concepts to a layman in a way which he understood.

I've got to think about this some more, and come back with further impertinent questions later. One is likely to be about how there can ever be 'inertial observers' (which, as I understand it, is a postulate of special relativity) when we're all falling towards one massive body or another by the operation of gravity...

I thought of this while reading this paper:

http://www.cfa.harvard.edu/Walsworth/pdf/PhysicsWorld_2004.pdf

Anyway, thanks again

.

 

[reilly]

The plain fact is that nobody knows why c is what it is. It is built into physics from the beginning -- Maxwell's equations require knowledge of the speed of light. All the stuff about Permittivity and Permeability is after the fact, and provides no clue about c.

In short, like the charge of the electron, the gravitational constant, ... , nobody knows from c -- Nature gives us things for which we have no explanation.

Regards,
Reilly Atkinson

 

[exponent137]

good question

The plain fact is that nobody knows why c is what it is. It is built into physics from the beginning -- Maxwell's equations require knowledge of the speed of light. All the stuff about Permittivity and Permeability is after the fact, and provides no clue about c.

In short, like the charge of the electron, the gravitational constant, ... , nobody knows from c -- Nature gives us things for which we have no explanation.

Regards,
Reilly Atkinson

...Which we have no explanation, but one explanation should be.

In next reference there are clues.
https://www.physicsforums.com/showthread.php?t=138968

 

[rbj]

The plain fact is that nobody knows why c is what it is. It is built into physics from the beginning -- Maxwell's equations require knowledge of the speed of light. All the stuff about Permittivity and Permeability is after the fact, and provides no clue about c.

In short, like the charge of the electron, the gravitational constant, ... , nobody knows from c -- Nature gives us things for which we have no explanation.

the gravitational constant, the speed of propagation (EM, gravitation, information, whatever is your "instantaneous" action), Planck's constant, permitivity of free space, these are all numbers that are purely human constructs resulting on how humans chose to define units of time, length, mass, and charge. note the 4 constraints and the 4 unknowns (that are eventually measured in terms of these anthropometric units). i know that the meter is now defined to be the distance traversed by light in 1/299792458 second, but that wasn't the original definition, for the sake of illustration, let's revert the definition of the meter back before 1960.

now, if instead, you measure everything in terms of Planck units, the values for all these constants become 1, 1, 1, and $1/(4 \pi)$. the only numbers given to us by Nature are dimensionless numbers. so, to ask "why is the speed of light equal to 299792458 meters per second?" causes us to ask the more basic questions that are "why are there about 6.1821 x 10³⁴ Planck lengths in a meter?" and "why are there about 1.8549 x 10⁴³ Planck times in a second?" those are the meaningful questions.

you see, if we measure and describe everything in Planck units, there simply is no c, or G, or $\hbar$, or $4 \pi \epsilon_0$. those numbers just go away from all of our algebraic equations of physical law.

we know that the meter and second are determined to be related to our experience of reality. a meter is approximately how big we are. and a second is, well, not the absolute shortest period of time in our bioological perception, but close to it. somewhere i read that, at our prime, we can do about 20 basic logical operations or computations (crude compare operations) per second in our conscious mind, don't know if that is true or not. when we get older, our CPU slows down but we got a better database.

so then we might start asking, why are there about 10²⁵ Planck lengths in the Bohr radius (about the size of atoms)? and why are there about 10⁵ atoms in the length of a biological cell? and why are there about the same number of cells in the length of a sentient organism like us?

you could construct similar questions about physiological processes regarding why it takes about 10⁴⁰ Planck times for us to do anything with our bodies (without tools). there is a relationship of the speed of our consciousness and the time around a second. if we were tiny insects, a second might seem like a long period of time. but then we wouldn't be thinking about why the speed of light is what it is. suppose we lived for 1000 years and it took us what we now consider a minute to think every new thought. we wouldn't be manuvering cars at 100 km/hr and i don't think a second would be our unit time and the speed of light would seem even faster to us.

you answer those questions, then you'll get close to why the meter and the second are as big as they are (relative to some Natural units), and, from that, you'll have an idea why the speed of light (which as far as Planck units are concerned is just 1, not some dumb and arbitrary number like 299793458) is what it is, from our perspective.

the speed of light (and of all things instantaneous) is just the natural speed of things in the universe of which to reference all other speeds against.

now the Elementary Charge, that's something else, since the natural unit of charge is already defined. it's interesting (to me at least) that the electron charge, relative to the Planck charge, is just $$\sqrt{\alpha}$$. one can say that e is what it is because of the value of the fine-structure constant (this important dimensionless number that the universe does give us), or (what i prefer) the fine-structure constant is what it is because of the amount of charge that Nature has bestowed upon electrons and other charged particles. because i think that they should have normalized $\epsilon_0$ and $4 \pi G$ instead of $4 \pi \epsilon_0$ and $G$, i think the most natural units would come out slightly different than the Planck units (but be the same order of magnitude) and then, measured in these natural units, the electron charge would be $\sqrt{4 \pi \alpha}$ which is about 0.30282212 . VERY close (as far as orders of magnitude go) to unity. i think 0.30282212 is the number theoretical physicists should put on their walls instead of 137.035999679 . i think the latter flows from the former.

those are the sort of numerical "why?" questions i would be wondering about.

 

[rbj]

...Which we have no explanation, but one explanation should be.

In next reference there are clues.
https://www.physicsforums.com/showthread.php?t=138968

i took a look at it. G is not dimensionless and i agree with Michael Duff (and a bunch of other physicists who dispute VSL and varying-G) about the meaninglessness of the varying G or c or any other dimensionful parameter in and of themselves. it's only the dimensionless parameters (which often come out as ratios of like dimensioned quantities) that matter. variable $\alpha$ has meaning. if the fine-structure changed, we would actually notice, but not if G did or c.

as stated previously, you measure everything in Planck units and there simply is no G or c or $\hbar$ to vary. they're just not there in physical law.

here's a nice quote from John Barrow:

[An] important lesson we learn from the way that pure numbers like $\alpha$ define the world is what it really means for worlds to be different. The pure number we call the fine structure constant and denote by $\alpha$ is a combination of the electron charge, e, the speed of light, c, and Planck's constant, h. At first we might be tempted to think that a world in which the speed of light was slower would be a different world. But this would be a mistake. If c, h, and e were all changed so that the values they have in metric (or any other) units were different when we looked them up in our tables of physical constants, but the value of $\alpha$ remained the same, this new world would be observationally indistinguishable from our world. The only thing that counts in the definition of worlds are the values of the dimensionless constants of Nature. If all masses were doubled in value [including the Planck mass m_P] you cannot tell because all the pure numbers defined by the ratios of any pair of masses are unchanged.

 

[windscar]

This obviously begs the question, "why does the universe have Lorentz symmetry?" Nobody knows. (Or at least there is no generally accepted answer, as far as I know.) This is the ultimate answer to all "why?" questions in physics, by the way. The answer to any "why?" question leads to another "why?" question, and ultimately we always come to one that we cannot answer in the context of physics, at least not yet.

I think if you were to answer the question; Why does all matter move exactly the speed of light slower than light?; would give more insight into this matter. What property of matter makes everything with mass travel exactly the speed of light slower than light, that travels at one truly constant speed.

 

[HallsofIvy]

I think if you were to answer the question; Why does all matter move exactly the speed of light slower than light?; would give more insight into this matter. What property of matter makes everything with mass travel exactly the speed of light slower than light, that travels at one truly constant speed.

What?? That doesn't even make sense. It is not true that all matter moves "exactly the speed of light slower than light". Literally interpreted that would mean that everything has speed 0! I presume you mean "everything travels slower than the speed of light", not "exactly the speed of light slower".

I'm not sure you will accept it as a property of mass, by the Lorentz formula an object moving at speed v has mass
$$\frac{m0}{\sqrt{1- v^2/c^2}}$$
where m0 is the "rest mass" or "invariant mass". As long as m0 is not 0, an object cannot move at the speed of light because that would mean infinite mass. Or, since acceleration= force/mass, the increasing mass requires constantly increasing force to accelerat further. Close to the speed of light requires almost infinite force to accelerate any more.

 

[windscar]

What?? That doesn't even make sense. It is not true that all matter moves "exactly the speed of light slower than light". Literally interpreted that would mean that everything has speed 0! I presume you mean "everything travels slower than the speed of light", not "exactly the speed of light slower".

I'm not sure you will accept it as a property of mass, by the Lorentz formula an object moving at speed v has mass
$$\frac{m0}{\sqrt{1- v^2/c^2}}$$
where m0 is the "rest mass" or "invariant mass". As long as m0 is not 0, an object cannot move at the speed of light because that would mean infinite mass. Or, since acceleration= force/mass, the increasing mass requires constantly increasing force to accelerat further. Close to the speed of light requires almost infinite force to accelerate any more.

Everything with mass measure's the speed of light being exactly the speed of light. It is one of the basis that started relativity. So if every object see's light traveling exactly the speed of light, then the difference in velocity of every object relative to light is exactly the speed of light. I did not say that matter can travel the speed of light, but all matter travel's the speed of light slower than light. Because they all measure the speed of light to be C.

 

[cristo]

Everything with mass measure's the speed of light being exactly the speed of light.

Correct.

So if every object see's light traveling exactly the speed of light, then the difference in velocity of every object relative to light is exactly the speed of light.

This is an invalid comment. I can measure the speed of light in my rest frame, and I will find it to be c. But, you are saying that light can measure my velocity relative to itself. However, this is not true, since light has no inertial frame of reference, and so the notion of traveling on a photon and measuring a body's speed relative to the photon does not make sense.

 

[windscar]

You don't have to sadle up on any photons to see this. All you must do is realize that light is always the speed of light faster than you. The difference in velocity of light and matter is always C. And I was just putting a brain teaser out there that matter always travels a speed of zero relative to light when traveling at a constant speed.

 

[masudr]

matter always travels a speed of zero relative to light when traveling at a constant speed.

In which reference frame?

 

[Gib Z]

In which reference frame?

In its own.

 

[masudr]

In its own.

Good, good.

Also, what does it mean when a username has a line through it in these forums (as windscar's appears to now do in all of his/her posts)?

 

[Gib Z]

No idea mate. If windscar ever posts again, we can ask him what he did :)

 

[cristo]

In its own.

Good, good.

But there is no inertial reference frame at rest with respect to the photon. That was the point I was trying to make!

 

[Gib Z]

Sorry I didn't see what you wrote cristo, I just saw masudr's post number 18 and replied directly to that.

 

[exponent137]

i took a look at it. G is not dimensionless and i agree with Michael Duff (and a bunch of other physicists who dispute VSL and varying-G) about the meaninglessness of the varying G or c or any other dimensionful parameter in and of themselves. it's only the dimensionless parameters (which often come out as ratios of like dimensioned quantities) that matter. variable $\alpha$ has meaning. if the fine-structure changed, we would actually notice, but not if G did or c.

as stated previously, you measure everything in Planck units and there simply is no G or c or $\hbar$ to vary. they're just not there in physical law.

At first, in the third section I wrote similarly as Duff or Barrow. But I added still importance of masses of elementary particles.

Variable G is next step in derivation, it is not beggining of third section. So 3-th and 2-nd sections should be reversed.

It is also important that I use variable G in small time intervals, therefore average value is constant in time. But this is not in contradiction to arguments of Duff and Barrow.
Regards

 

[masudr]

But there is no inertial reference frame at rest with respect to the photon. That was the point I was trying to make!

I assumed he meant the reference frame where the massive particle itself is at rest.

 

[rbj]

It is also important that I use variable G in small time intervals, therefore average value is constant in time. But this is not in contradiction to arguments of Duff and Barrow.

Barrow's been saying a lot of different things now, so i cannot speak for him. i am confident that Duff scoff's at any notion, small time intervals or something else, of varying G, c, $\hbar$ or any other dimensionful universal parameter (semantic replacement for constant). http://www.arxiv.org/abs/hep-th/0208093 http://arxiv.org/abs/physics/0110060 .

i'll say it again, express everything in Planck units and there is no G, c, or $\hbar$ to vary.

 

[mina26]

Hi

I'm a confused layman, and was hoping to get some answers to the question: why is the speed of light? That's not a typo - I mean, why is it what it is? The questions below are specific ways to ask essentially the same question.

1. The speed of light is 299,792,458 metres per second. What stops it from reaching 299,792,459 m/s?

2. If light has no mass, what stops it from having infinite speed? What’s slowing it down?

3. Light from the sun takes 8 minutes 24 seconds to reach the Earth – why can’t it get here faster?

Thanks in advance.

.

light is a dual phenomenon sometimes it appear like waves as in interference patterns(young's experiment) and sometimes like particles like in quantum mechanics

the velocity of light take this constant value for many reasons the simple of them is as follow and arises from the maxwell's equations

in defining his 4 equations Maxwell's proved that the Electric field E and as well as The Magnetic field H take the form of a wave equation in the usual non-relaivistic:wave velocity* laplacian(E or H)=partial time derivative of(E or H)

in defining the velcity he found that it is 1/(epsilon mu) all power half and that's why this taken as the velcity of light and Maxwell's wrote the above value written in your message

the velcity of light is a limiting value for all other velocities in nature and this comes from the simple idea that is case of motion you are retarded cause of friction and although you increases your velcity the friction increases in proportional values so you will never move faster than light and if so you will become a photons

in general relativity and eapecialy in 1919 when A.Edington travel to South Africa to see the sun eclipse he found that the einstein proposition for light deviantion near the sun mass is true and that's why einstein in 1921 took the nobel proze in physics although it wasn't for GR

light may loose its velocity when interacting with other fields such as scalar fields wind,liquids,and many other disturbances may change the velocity of light light in GR is accpeted in particle form but in Maxwell's equations it is wave
see De Broglie equation and its explanation

 

[rbj]

1. We defined light to go that distance in 1 second. If somehow miraculously, and it cant, light went faster, that new distance is still 299,792,458m.

it's not that it can't , it's that such a change would be observationally meaningless. (maybe that means it can't.) you are correct that, given the defnition of the meter today, that c will always be 299792458 m/s, but suppose we reverted the definition of the meter back to its 1959 definition: the distance between two scratch marks on a platinum-iridium prototype bar at BIPM. now, it is conceivable that a new measurement of c can come out to be a different number. but even then there is one or two different dimensionless numbers that are the salient measure. c came out different because the number of Planck lengths between those two little scratch marks has changed or the number of Planck times in the time it takes for one oscillation of this Cesium radiation has changed. those two dimensionless numbers are what is salient. one of those changes and something in our experience, something we can measure, changes.

 

[exponent137]

Barrow's been saying a lot of different things now, so i cannot speak for him. i am confident that Duff scoff's at any notion, small time intervals or something else, of varying G, c, $\hbar$ or any other dimensionful universal parameter (semantic replacement for constant). http://www.arxiv.org/abs/hep-th/0208093 http://arxiv.org/abs/physics/0110060 .

i'll say it again, express everything in Planck units and there is no G, c, or $\hbar$ to vary.

In article »Trialogue on the number of fundamental constants« http://arxiv.org/abs/physics/0110060 .it is written »Only the variation of dimensionless constants have an intrisic physical meaning.« But Gravitatonal constant G belongs to important dimensionless constants, which include masses of elementary particles mi and Planck mass mpl. These constants are bi=(mi/mpl)^2. I thougth fast variation of these dimensionless constants. If these constants are variable on macro time scale, this is in opposition with general relativity. But this does not mean that they should not be variable on micro time scale. This means, successive fast measurements of bi give different values, only average is closer and closer to known value. This is written in my article https://www.physicsforums.com/showthread.php?t=138968.

We can imagine that that all protons, neutrons and electrons masses are smaller for factor 0.001 than they are. So our scales for distances mass, time would be different and light speed would be slower. This gives example that masses of elementary particles are also important.

 

[rbj]

In article »Trialogue on the number of fundamental constants« http://arxiv.org/abs/physics/0110060 .it is written »Only the variation of dimensionless constants have an intrisic physical meaning.« But Gravitatonal constant G belongs to important dimensionless constants,

no, it doesn't. in Planck units (and some other systems of natural units like Stoney), isn't even there. in some other system of natural units like the common Atomic units, there would be a dimensionless G that would simply be a function of the electron mass relative to the Planck mass, and fine structure constant.

$$G = \left( \frac{m_e}{m_P} \right)^2 \frac{1}{\alpha} = \frac{4 \pi \epsilon_0 m_e^2 }{e^2}$$

if that's the dimesionless G you mean, i say it's really about the other constants in that ratio. if you choose units that normalize e and $\epsilon_0$, then your G is really about the mass of the electron relative to the unit mass.

which include masses of elementary particles mi and Planck mass mpl. These constants are bi=(mi/mpl)^2. I thougth fast variation of these dimensionless constants. If these constants are variable on macro time scale, this is in opposition with general relativity.

i didn't think that GR had anything to say about the masses of electrons.

But this does not mean that they should not be variable on micro time scale. This means, successive fast measurements of bi give different values, only average is closer and closer to known value. This is written in my article https://www.physicsforums.com/showthread.php?t=138968.

i just don't find the point of it persuasive. if you define the quantitative size of anything in terms of natural units (such as Planck units) that normalize G, it becomes non-existant in physical law. there is no G left to vary. if you claim it varies due to the result of some experiment, there is always the dimensionless ratio of some other quantities that would be the root reason for the variance.

We can imagine that that all protons, neutrons and electrons masses are smaller for factor 0.001 than they are. So our scales for distances mass, time would be different and light speed would be slower. This gives example that masses of elementary particles are also important.

the ratio of masses of those elementary particles, to each other or to the Planck mass. it's those ratios that count. and G is not there. it, along with c, $\hbar$, and $\epsilon_0$ are merely reflections of arbitrary human decisions regarding the base units of length, mass, time, and charge. regarding the ostensibly deep questions about why particular universal constants take on the value that they do, these dimensionful constants should be immediately removed from that list. it only matters about the dimensionless constants (like $\alpha$ and $m_p/m_e$) and what values they take on. those are the only meaningful questions to ask. there is no meaning to any speculation as to what would be different if G or c were different. it simply is something that, in and of itself, is as Barrow puts it, "observationally indistiguishable", or as Duff puts it, "operationally indistinguishable". the key word is "indistinguishable".

 

[exponent137]

Above all, my section in article describe fast variation of μi with time. I used G, because it is easier comprehensible than variation of μi. Besides, G represents GR and this is one rare example of quantization of GR: So even in the case that I agreed with your and Duff's ideas, idea of my article remains live.

But in trialogue "Okun, Veneziano, Duff" I agree with Okun because:

1. Correct unit is c = 1 lpl/tpl and not c= 1.
2. In relativistic mathematic time is different from distance even at c=1 units.
3. Human constructions are reality, so time is different reallity than distance or mass.
4. Despite existence of all μi, quantities mass, velocity etc are still ever important and operative.
5. Duff did not give enough clear model, why forget on dimensionful values. Unimportance of Boltzman's constant is really good argument and it make my belief unclear, but I think it is not enough.

I will give one example, how G can be operative: From distant galaxy we measure that all μi are 5 times larger and fine structure constant is the same as in our space. The most appropriate explanation can be that G is 5 times larger.
Do you think that this example is not possible, because G is not operative?

 

[rbj]

Above all, my section in article describe fast variation of μi with time. I used G, because it is easier comprehensible than variation of μi. Besides, G represents GR and this is one rare example of quantization of GR: So even in the case that I agreed with your and Duff's ideas, idea of my article remains live.

But in trialogue "Okun, Veneziano, Duff" I agree with Okun because:

1. Correct unit is c = 1 lpl/tpl and not c= 1.
2. In relativistic mathematic time is different from distance even at c=1 units.
3. Human constructions are reality, so time is different reallity than distance or mass.
4. Despite existence of all μi, quantities mass, velocity etc are still ever important and operative.
5. Duff did not give enough clear model, why forget on dimensionful values. Unimportance of Boltzman's constant is really good argument and it make my belief unclear, but I think it is not enough.

I will give one example, how G can be operative: From distant galaxy we measure that all μi are 5 times larger and fine structure constant is the same as in our space. The most appropriate explanation can be that G is 5 times larger.
Do you think that this example is not possible, because G is not operative?

no, the most appropriate explanation is that this dimensionless ratio of particle mass to Planck mass $\mu_i$ is $\sqrt{5}$ times larger. behind every perception or measurement of a dimensionful quantity, like G, changing is a more fundamental dimensionless quantity (or collection of quantities in this case) changing.

 

[exponent137]

But, number of different particles (electron, proton, pions...) is large and I think that is infinite. Easier is to say that "one dimensionful constant is changed" instead of that "all dimensionless constants are changed for one factor". Even in the case that we forget G and use Planck's mass. Or do you maybe suppose that Planck's mass is dimensionless?

 

[rbj]

no, all that i am saying (this is practically tautological, so i cannot understand why it might be controversial) is that saying that "G apparently increased by a factor of 5 is the same as saying that all particle masses $\mu_i$ have increased by a factor of $\sqrt{5}$ with respect to the Planck mass (which is only dimensionless if you're thinking only in terms of Planck units, and then it is the dimensionless 1). it is this set of dimensionless ratios that is salient.

 

[exponent137]

no, all that i am saying (this is practically tautological, so i cannot understand why it might be controversial) is that saying that "G apparently increased by a factor of 5 is the same as saying that all particle masses $\mu_i$ have increased by a factor of $\sqrt{5}$ with respect to the Planck mass (which is only dimensionless if you're thinking only in terms of Planck units, and then it is the dimensionless 1). it is this set of dimensionless ratios that is salient.

I think that Duff's idea is creative, but he tried to much.

1. I think that Planck's mass is dimensionful also at Planck's units.
2. I think that it is statistically much more possible that Planck's mass is increased by factor 0.2 instead that all particle masses are increased by factor 5.
3. We peoples think in units. We feel consciousness, so time, (and mass, length etc) not only dimensionless things. Okun say in trialogue that he wrote in word (some sort of units) not only in formulas and equations.
4. time is mathematicaly different that lenght. It is not symmetric etc.