#### The Speed of Light

The speed of light limit is at this point a postulate of physics, which is necessary as:

• Electromagnetic Radiation travels at c.
• Maximum speed of particles is c. (Lorentz equation).
• Relativistic QM – depends on c as a postulate.
• Strong force.
• more…

These are in the Standard Model disparate fields and laws. Why do they all share the same speed ‘c’? The only real answer right now is ‘because’. Hence the speed of light is a postulate.  In modern physics this fact is acknowledged by saying that its not the ‘speed of light’ but rather the ‘fundamental speed’.

Postulates are never a good thing. Much of our understanding of the physical world comes from explaining away what we thought were arbitrary rules using more fundamental principles.  We do need postulates, but its a good thing when we can lower the count. The Standard Model + QM have many tens of postulates (rules, particle masses, coupling constants, etc etc).

Now look again at a universe made of only GR. The speed of light becomes the speed of gravity – a ‘mere’ bulk propagation constant – the speed of Einstein’s Aether.

If one were to then build out other fields and physical effects (e.g. emergent quantum mechanics) using GR as a base, the speed of light is not needed as a postulate. It then becomes transparent as to why the speed of light is the same as the speed of gravity, and why the equations of relativistic QM are littered with the symbol ‘c’. Some ideas of how to build todays physics from GR are outlined in other posts on this site, but also see Brady and Anderon’s paper.

#### Lorentz Transformation

The behaviour of particles and clocks at velocity is dealt with using Lorentz transformations. These same transformations arise when looking at emergent phenomena such as Brady’s sonons travelling through an inviscid medium with a sound velocity. Thus Lorentz contraction can be thought of as arising from the bulk properties of the GR field.

#### Consequences

Removing the speed of light as a postulate would be a good thing, but are there any measurable consequences? In other words, if there is some truth to this theory is there any experiment that might be done to show that the speed of light is merely a bulk property of an all encompassing field that creates all matter, fields and forces?

Look at the speed of sound on Earth. This speed forms a barrier to objects moving faster than sound. But jets and asteroids can move faster than sound. So maybe analogously we can find a way to break the light speed barrier? Its not as simple as breaking the sound barrier though, as GR is an extremely strong field with a truly huge range of perfectly linear behaviour. To get an idea of its strength, consider that a mass of the Earth formed into a black hole is only about a cm in size, and so GR behaves linearly up to within a metre or so of that incredible field strength.  But experimenters have access to extremely accurate clocks, huge collision energies and lots of computational power.

Once its accepted that the the speed of light might not a postulate, experiments are possible. There are actually quite a few people already measuring the constancy of the speed of light.

#### Conclusion

The fact that the speed ‘c’ is ingrained in all of physics and that General Relativity has this speed built in at a fundamental level is a huge clue as to the underlying makeup of the world around us.

My take: Its all GR.

–Tom Andersen, July 1 2015