Breaking the Universal Speed Limit?

Well, how do you measure the speed of light - and thus check that everything is observing this ‘universal speed limit’? Seven years ago, the closing months of 2011 saw much excitement in sciencey circles with the highly mediatized announcement that researchers at CERN, the world's most expensive physics laboratory, had detected sub-atomic particles apparently travelling faster than the speed of light. This, the papers assured us, was in defiance of Einstein and all the rules of relativity. Yet the plain ‘fact’ of the matter is that the speed of light is not magically ‘out there’ but merely a human convention. In a relativistic universe, how could it be otherwise?

Here the point is put nicely by Burt Jordaan in a blog posting of January 25, 2010. Burt writes:

‘In order to measure any one-way velocity, we essentially need two clocks: one at the start and one at the end. Obviously, the two clocks need to be synchronized and run at the same rate (and to be sure, they must not be moving relative to each other and also be at the same gravitational potential). Yet we reasonably assume that the two clocks run at the same rate, at least close enough for all practical purposes. Now we need to synchronize the two clocks to read the same at the same moment. How is this done?


In his 1905 paper on Special Relativity, Einstein says: “We have not defined a common ‘time’ for A and B, for the latter cannot be defined at all unless we establish by definition that the ‘time’ required by light to travel from A to B equals the ‘time’ it requires to travel from B to A”.

One can reasonably read Einstein's ‘by definition’ as ‘by convention’. 
Using Einstein’s convention to set the distant clock at a known distance, call it ‘D’, in empty space, we send a light signal at (say) time zero and when the distant clock detects the signal, it sets its time to D/c sec (the light travel time), where c is the standard speed of light in vacuum.

Now we can measure the speed of any object moving between the two clocks. We can also use the two clocks to measure the one-way speed of light, but we are obviously guaranteed to always get c. In this sense, we get the speed of any object only relative to c and not absolutely. 
In this way, the one-way speed of light is a convention, depending on the convention for clock synchronization."

Burt concludes by observing that there is a general belief system prevailing in physics that ‘whatever is known exists and rest is non-existent’. It is because of this belief system that scientists tend to fill  these existence-nonexistence gaps by cofficients. Yet there can be much more existent and important entities quite apart from the usual quantitites of space and time which physicist are led to ignore. This attitude is the reason that the existence of Dark Matter was unimaginable for four hundred years. As to the spped of light itslef, Burt says explicitly that he cannot understand why Einstein established a ‘religion of special abilities and qualities’ for light. Specifcally, he objects tha even though there are ways to measure the speed of light, there is no reason to believe that nothing can travel faster.

Our own correspondent, Muneeb Faiq, took up the issue for Pi too. Here he offers a thought experiment which again shows the arbitariness of the ‘speed of light’.

‘In fact, there is a lot of confusion about the harmony between the classical and quantum definitions of speed.If both quantum speed and classical speed mean the same then a very interesting difficulty comes to the front.

Suppose there exists only one body in the universe. Just a single point mass and space. Is it at rest or in motion? If, however, there come out two photons of light moving parallel to each other. What speed are they moving at? If an observor is stationed on the point mass, then both the photons are moving with the velocity of light. Suppose, all of a sudden, the point mass ceases to exist. Now there are two photons moving with same speed parallel to each other. Nothing else exists except space. Are these two photons moving now because they are at same position in relation to each other which will be defined as the state of rest.

It is interesting to note that before the point mass existed, the two photons were moving with the velocity of light. Now since the point mass has ceased to exist but nothing changed about the photons, they are not supposed to be moving now even if they are moving with the same previous speed.’

Q&A On the Status of the Speed of Light

Pi’s New Year Q&A: Is the One-way Speed of Light a Convention?

Martin Cohen and former Pi contributor, Muneeb Faiq explore one of the claimed certainties of physics.

To introduce the issue, here's blogger Burt Jordaan wondering, way back in January 2010, about why the 'speed of light' suddenly became the one true measure of all things scientific.

Burt writes:

'In order to measure any one-way velocity, we essentially need two clocks: one at the start and one at the end. Obviously, the two clocks need to be synchronized and run at the same rate (and to be sure, they must not be moving relative to each other and also be at the same gravitational potential). Let we reasonably assume that the two clocks run at the same rate, at least close enough for all practical purposes. Now we need to synchronize the two clocks to read the same at the same moment. How is this done?'

Recall that Einstein himself clearly admits, in his 1905 paper on Special Relativity, that: "We have not defined a common 'time' for A and B, for the latter cannot be defined at all unless we establish by definition that the 'time' required by light to travel from A to B equals the 'time' it requires to travel from B to A."

Burt says from this that what Einstein terms as being 'by definition' is equally 'by convention'*. Consider: Is the radius of space's curvature related to the speed of light?

The Q&A


Martin: That's a four-guinea question, innit? I believe conventional accounts make space into 'space-time' and the speed of light is allowed to determine things like that, yes.

Muneeb: I don't understand why Einstein established a religion of special abilities and qualities of light. Though there are ways to measure the speed of light but there is no reason to believe that nothing can travel faster. I think a few thought experiments should be propounded to at least break the myth that light owns special physics and light makes nature asymmetric.

There is a lot of confusion about the harmony between the classical and quantum definitions of speed, for example. If both quantum speed and classical speed mean the same then a very interesting difficulty comes to the front. Suppose there exists only one body in the universe. Just a single 'point-mass' and space. Is it at rest or in motion? If, however, there come out two photons of light moving parallel to each other. Now what speed are they moving at? If an observer is stationed on the point-mass, then both the photons are moving with the velocity of light. Yet, suppose, all of a sudden, the point-mass ceases to exist. Now there are only two photons moving with same speed parallel to each other. After all, nothing else exists except space. Before, when the point-mass existed, the two photons were moving with the velocity of light. After, when it has ceased to exist, they seem to not be moving at all! And yet nothing has changed regarding the photons. I hope I have made my point!

Martin: Yes, I get your point... I've wondered about this sort of thing too!

Isn't the usual idea that the universe started with a single point, 'the singularity', and at this time indeed none of the usual laws applied. Then there seems to be a suggestion that the speed of light may not have become 'defined' in the key moments of the first 'explosions'.

Now what this caused me to puzzle a little about, is that if, in fact, the singularity was one particle - as you say, a photon - and if it travels, by definition, at the speed of light, then surely it can be everywhere at the same instant, because of those peculiar Einsteinian laws. In other words, could it be that the universe consists of just one photon, which is everywhere, creating both space and time?

Bear with me! Suppose this is the universe, then why would it matter what speed the photon travelled at, any more than where it was or when? Nothing would be meant by these comparative terms.
What do you think? Can we put our ramblings into a form that would make a suitable webpage? I'd like to try, PI is a good way to organise and explore ideas.

Muneeb: There is an interesting point to note: what are usual laws? Why are they usual? Are the laws of physics really laws in the first place - because if they would really be laws; then they should never fail to explain behaviour of everything that exists. This difficulty hovered around the intellect of many great physicists - including Einstein - and that is why he spent so many years in search of a unified theory that he hoped would explain everything.

Mathematics, theory and philosophy should go hand-in-hand in order to get a further insight into reality. Otherwise we all have to be convinced (like Stephen Hawkings) that there can never be a grand unified theory. But I am afraid in that case, then we have to be convinced that there are no governing laws at all. All physics will melt away.

Instead, let physicists, philosophers and mathematicians come together and work in harmony in an open-hearted, interdisciplinary manner to understand what none of these disciplines will ever be able to get grasp of independently.

Martin:   Well, y'know, this is certainly a good question, but I'm not sure it is quite as clear a distinction as you imply. For example, we might say it is a law of physics that energy can neither be created nor destroyed, no? Without being obliged to throw that principle away just because (eg) some neutrinos evidently don't want to be part of the present theory about cosmic speed limits?

Muneeb:   Yes. You are right. We, of course, can say it is a law of physics that energy can neither be created nor destroyed without being obliged to throw that principle away just because some neutrinos evidently don't want to be part of the present theory about cosmic speed limits. But what is the applicability percentage of these well established laws? If energy and matter can neither be created nor destroyed, then from where did it blast into existence? Shall we then opt for the principle of first cause where these laws fail altogether? No Newtonian law holds good when we discuss atoms and sub-atomic particles. Einstein himself said that quantum mechanics (which is again a set of laws)is not absolute. Furthermore- quantum and classical worlds are composed of same material and, therefore, some basic underlying principles must be obeyed which we have not yet been able to discover. It is not the question of neutrinos only because most of the universe is composed of dark matter and dark energy which was concealed from over imagination for hundreds of years because of the over emphasis paid by physicists on the laws that are collectively described as quantum and classical mechanics.

The portion of the universes that the currently available laws explain is negligible as compared to the great splendour of dark matter and dark energy that fill the universes (previously we concieved only one universe but now we say universes). There may be some "extra-bright matter" and "extra-bright energy" awaiting our discovery. For that, we again have to wait for the failure of currently known laws of physics and those great mathematical equations that terrify all those who are not physicists and mathematicians. Once we fortunately fail, we will be obliged to look for an explanation for the failure and may consequently theorize existence of very weird materials and phenomena faintly conceivable as of now within the delineated perimeters of quantum and classical conditioning. That is why I emphasize on first understanding what makes the universe (what material and quality of materials and types thereof constitute everything), then we need to classify all that material and non material on some sound basis.

We also have to classify on the basis of discovered and not-discovered. Then we have to understand their behaviour. On the basis of the theory generated; we then can develope mathematics which explains things and helps us to imagine what we cant with the help of mere theory. I hope I don't sound insane!

Martin:   Mmmm, absolutely, I do agree that physics is full of 'black holes' to pun little! But I just want us to avoid addressing ill-founded assertions in conventional science with our own ill-founded assertions. For example, the 'dark matter' mystery - is this not a theoretical construct itself, intended to plug an experimental hole in current theory? You speak of it as a discovered reality, but isn't that to fall into the same way of thinking as the people you are critiquing?

Thinking about the 'problem' of where the energy in the universe came from, isn't it perfectly logical to simply say that there is no 'before' to be dealt with or explained?

Over to you, or anyone reading?

Muneeb: Haha! I am caught in a loop.I am not smart enough for arguments. However, though my writing apparently reveals that dark matter is a reality but I don't mean that. That is why I have guessed the existence of extra-bright matter and energy. What I am doing is to use the discoveries of physics to prove the inconsistencies in physics itself.

I should put a caveat here that I am not anti-science or anti physics. Dark matter was discovered by science to plug the black holes (as you say)and may be some other matter and energy will sooner or later be discovered which disproves everything. Does it mean that we should try to adjust our current theories without revising our basic understanding of the universes. Science has made aeroplanes fly etc. but that does not mean science is correct everywhere. Regarding your question of Un-important "before", please allow me to disagree with you because "before" is of great importance.

First question is; what time-point in the evolution of universes is the beginning? Why is a particular scale of past not a "before" and why all of a sudden we think of something as "before"? Cant it be that this "before" may give us inkling into the evolution of the behaviour of everything that apparently exists. What happened before big bang seems to me as important as what happened afterwards. This is because if we come to know the state, status and behaviour of matter, energy, space, time, void etc.before big bang, we will surely get some idea about how matter, space and time evolves to a better extent than if we stop at big bang. Thanks!

Particles Dreaming

By Perig Gouanvic
Reposted from Pi alpha

Reflecting on the Double Slit Experiment

What do particles know?

The so-called ‘double-slit experiment’ is a demonstration that light and matter can display characteristics of both classically defined waves and particles. It is also said that it displays the 'fundamentally probabilistic nature' of the universe at the quantum scale.

The original intuition of Thomas Young (back in 1802) was to reproduce the cancellation of water waves, but with light; the double slit was simply used to yield two exactly identical light sources (the same, divided in two). Notice the straight lines that seem to radiate from the source of the water waves: they are made of the cancellation of each other, and are analogous to the dark regions on the five-step picture (below), a true depiction of the impact of electrons in an experiment made by Tanamura.

In the de Broglie–Bohm theory (also called the Bohm interpretation) of quantum physics, the reason why single particles seem to interfere ‘with themselves’, in other words, the reason why, in the double-slit experiment, even single particles ultimately form a figure of interference despite of the fact that they are not emitted as beams but one after the other (see the 5-step process, below), is because each of these particles have a kind of pilot wave which does interfere with itself in some circumstances like the double slit apparatus. The analogy of the sonar helps to explain the phenomenon : picture a dolphin who would have to echolocate through two holes and you get the picture!

Bohm had many analogies for the quantum potential, his revised version of the pilot wave. The sonar is one of them. The information given by the surroundings guides the dolphin, it is called 'active information'

However, what this analogy leaves unattended is the fact that particles do not "send" signals to the surrounding and do not "wait" for this signal to bounce back. Another analogy far remote from the sonar one, was given by Bohm : each particle is like a piece of an hologram, each contains information about the whole, but each is concretised in a specific context.

The 'echolocation' process would be more like a pulsation between the particle as a located entity and the particle as one concretion of the whole. Pulsating infinitely rapidly between being-discrete and being-the-whole, the particle would be more like a process taking the form of an object.
What kind of "thing" can be everything half of the time and something the rest of the time?

Humans, for starters. We, as particles, tend to forget that we also are the whole, each night. We dream.