Why is the Speed of Light Constant?

The query "The reason is the speed of light constant?" is typically asked about by individuals attempting to learn physics. Google has 2760 links to that question. However the answer is so easy that a 10-year-old can understand it, that is, if you accept Quantum Field Theory.

Bring the ten-year-old to a lake and drop a rock in the water. Show her that the waves move through the water at a specific velocity, and tell her that this velocity depends solely on the properties of water. You may drop different items at different areas and show her that the waves go at the exact same rate, no matter the size of the object or location of the water.

Then tell her that sound travels through air with a fixed velocity that depends solely on the properties of air. You might wait for a thunderstorm and time the difference in between the lightning and the noise. Inform her that a whisper moves as fast as a scream. I believe a ten-year-old can perceive the concept that water and air have properties that establish the velocity of these waves, even if she does not understand the equations.

Any person who can understand this can then comprehend why the speed of light is constant. You see, in Quantum Field Theory space has properties, exactly as air and water have properties. These properties are known as fields.

As Nobel laureate Frank Wilczek wrote, "One of the most basic results of special relativity, that the speed of light is a limiting velocity for the propagation of any physical influence, makes the field concept almost inevitable.".

When you recognize the concept of fields (which of course is certainly not an easy one), that is really all you have to understand. Light is waves in the electromagnetic field that travel through space (not space-time) at a velocity governed by the properties of space. They abide by fairly basic formulas (not that you have to recognize them), just like sound and water waves follow basic formulas. OK, the Quantum Field Theory equations are a little bit more intricate, but quoting Wilczek again, "The move from a particle description to a field description will be especially fruitful if the fields obey simple equations ... Evidently, Nature has taken the opportunity to keep things relatively simple by using fields.".

Even so this inquiry can have a different meaning: "Why is the speed of light independent of motion?" This fact was first illustrated by the renowned Michelson-Morley experiment, in which light beams were measured as the earth revolved and rotated. The shocking result was actually that the speed of light was precisely the same no matter the earth's movement.

As I wrote in my publication (see quantum-field-theory. net): That the speed of light must be independent of movement was most surprising ... It makes no sense for a light beam - or anything, for that concern - to travel at the exact same speed regardless of the movement of the observer ... except if "something funny" is going on. The "something funny" ended up being much more astonishing than the M-M result itself. Essentially, objects contract when they move! More specifically, they contract in the direction of movement. Think about it. If the path length of Michelson's device in the forward direction contracted by the exact same amount as the extra distance the light beam would certainly have to travel due to motion, the two effects would cancel out. Indeed, this is the only way that Michelson's null result can be illustrated.

However the idea that objects contract when in motion was just as confusing as the Michelson-Morley outcome. Why should this be? Again the explanation is offered by Quantum Field Theory. Quoting once again from my publication:.

We need to recognize that even though the molecular configuration of an object appears to be stationary, the component fields are constantly interacting with one another. The EM field interacts with the matter fields and vice versa, the strong field interacts with the nucleon fields, etc. These interactions are what holds the object together. Now if the object is moving rather fast, this interaction between fields will certainly become more difficult because the fields, on the average, will need to interact through larger distances. Thus the object in motion ought to somehow adjust itself so that the identical interaction between fields can take place. How can it do this? The only way is by decreasing the distance the component fields need to travel. Since the spacing between atoms and molecules, and hence the dimensions of an item, are determined by the nature and arrangement of the force fields that bind them together, the dimensions of an object must therefore be affected by movement.

It is essential to recognize that it is not just Michelson's apparatus that contracted, it is anything and everything in the world, including Michelson himself. Even if the earth's speed and the consequent contraction were a lot greater, we on earth would continue to be ignorant of it. As John Bell discussed a moving observer:.

But will she not see that her meter sticks are contracted when laid out in the [direction of motion] - and even decontract when turned in the [other] direction? No, because the retina of her eye will also be contracted, so that just the same cells receive the image of the meter stick as if both stick and observer were at rest. - J. Bell (B2001, p. 68).

To conclude, for those who wish to comprehend physics, I say use Quantum Field Theory and: WAKE UP AND SMELL THE FIELDS.

EXACTLY WHAT DOES THE ELECTRON LOOK LIKE?

In June, 2014, I lectured at the Physics Department of the Czech Technical University in Prague. I began by asking the question "What does the electron look like?", and I presented 2 images. The first was the familiar Rutherford photo of particles orbiting a nucleus, and the 2nd was a (very simplified) photo of the electron as a field in the area surrounding the nucleus.

Then I wanted a vote. Rather remarkably only four people in the crowd chose the field photo, and not a single person picked the particle photo. In other words, THEY DID N'T KNOW. So here we are, 117 years after the electron was identified, and this highly educated group of physicists had no idea what it looks like.

Naturally when the electron was discovered by J. J. Thomson, it was naturally pictured as a particle. After all, particles are simple to imagine, while the field idea, let alone a quantized field, is not a very easy one to understand. But this photo soon ran into problems that led Niels Bohr in 1913 to offer that the particles in orbit image must be replaced by something new: undefined electron conditions that satisfy the following two postulates:

1. [They] have a peculiarly, mechanically unexplainable [emphasis added] stability.

2. In contradiction to the classical EM theory, no radiation takes place from the atom in the stationary states on their own, [however] a process of transition among two stationary states can be followed by the emission of EM radiation.

This led Louis de Broglie to suggest that the electron has wave properties. There then followed a sort of conflict, with Paul Dirac leading the "particle side" and Erwin Schrodinger the "wave side":.

We insist that the atom in truth is just the ... phenomenon of an electron wave captured, as it were, by the nucleus of the atom ... From the point of view of wave mechanics, the [particle image] would be just fictitious.-- E. Schrodinger.

Nevertheless the fact that a free electron acts like a particle could not be overcome, and so Schrodinger gave in and Quantum Mechanics became a theory of particles that are defined by probabilities.

A 2nd battle happened in 1948, when Richard Feynman and Julian Schwinger (along with Hideki Tomanaga) created various methods to the "renormalization" problem that plagued physics. Again the particle view espoused by Feynman triumphed, in huge part considering that his particle diagrams demonstrated simpler to deal with than Schwinger's field equations. So 2 generations of physicists have been brought up on Feynman designs and led to believe that nature is made from particles.

In the meantime, the theory of quantized fields was refined by Julian Schwinger:.

My retreat started at Brookhaven National Laboratory in the summer of 1949 ... Like the silicon chip of more recent years, the Feynman diagram was delivering computing to the masses ... But inevitably one has to bring it all together again, and then the piecemeal method loses a bit of its appeal ... Quantum field theory must work with [force] fields and [matter] fields on a completely equal ground ... Here was my challenge.-- J. Schwinger.

Schwinger's last variation of the theory was released between 1951 and 1954 in a collection of five documents entitled "The Theory of Quantized Fields". In his terms:.

It was to be the purpose of further developments of quantum mechanics that these 2 distinct timeless principles [particles and fields] are combined and become transcended in something that has no classical counterpart-- the quantized field that is a fresh conception of its very own, an unity that replaces the classical duality.-- J. Schwinger.

I believe that the primary reason these work of arts have been ignored is that many physicists considered them too tough to understand. (I know 1 who could not get past the very first page.).

Therefore the choice is all yours. You can believe that the electron is a particle, in spite of the many inconsistencies and absurdities, not to mention questions like how significant the particles are and what are they made of. Or you can believe it is a quantum of the electron field. The choice was described this way by Robert Oerter:.

Wave or particle? The answer: Both, and neither. You could consider the electron or the photon as a particle, but only if you wanted to let particles behave in the bizarre way illustrated by Feynman: appearing again, disrupting each other and canceling out. You can also think of it as a field, or wave, but you had to keep in mind that the detector always registers one electron, or none-- certainly never half an electron, no matter just how much the field has been split up or stretched out. Ultimately, is the field just a calculational instrument to tell you where the particle will be, or are the particles just calculational tools to tell you what the field values are? Take your pick.-- R. Oerter.

What Oerter neglected to mention is that QFT explains why the detector constantly registers one electron or none: the field is quantized. The Q in QFT is extremely important.

So when you choose, dear reader, I really hope you will not pick the image of nature that does not make sense-- that even its proponents call "bizarre". I wish that, like Schwinger, Weinberg, Wilczek, Hobson (and me), you will choose a truth made of quantum fields-- properties of space that are explained by the equations of QFT, the most philosophically appropriate picture of nature that I can think of.

More on the blog at Fields of Color.