The speed of light in a space is pretty much the greatest fundamental constant in physics, and conferring to the universal theory of relativity, gravity also travels at the same rate as the speed of light does. But a new research proposes that the speed of light might not have continuously been this speed. Actually, in the early Universe, the speed of light might have outpaced gravity, and this new theory could answer one of the main problems in physics.
Greatest of all, different from a lot of theories put forward in theoretical physics, this hypothesis can actually be tried, so we must be able to discover out in the coming years if it's accurate or not. So what happened with the speed of light and gravity in the first place? This puzzle comes from the first days of the Cosmos, and something is known as the horizon problem. The horizon problem fundamentally deals with the information that the Universe get hold of a uniform temperature long before light particles or photons would have had enough time to reach all places of the Universe. If the speed of light in a space surely is constant, and permanently has been, then how the cosmos did got heated so fast? Generally, this problem is dealt with by the indication of inflation, which proposes that the Universe went through an enormous period of spreading out early on.
The theory is that the temperature must have evened out when the Universe was all trivial and compressed, back when the light did not have traveled as far as it has, and then it quickly grew. That makes logic, except no one sees why inflation happened or stopped, and there is no method of testing it. Another hypothesis has now been presented by scientist Niayesh Ashfordi from the Perimeter Institute in Canada (PIC), and João Magueijo from Imperial College London (ICL). Their indication is this: in the earliest days of the Cosmos, light, and gravity journeyed at different speeds. This could mean that light was faster than it travels now, or gravity might have moved or traveled slower.
The scientists told Michael Brooks over at New Scientist, "Either way, if photons traveled faster than gravity just after the Big Bang, that would have allowed them to get far-off enough for the universe to reach an equilibrium temperature much more rapidly.”
For the moment, this is just a hypothesis. But the truly exciting part is that it can really be tested. If the theory is true, there will be specific signs left in the celestial microwave background radiation, the remaining radiation from the Big Bang that we can still sense and study nowadays. Scientists were able to evaluate that a value called the spectral index, which defines the early density of waves in the Universe, would have a stable value if their theory is right: 0.96478. Fascinatingly, the most recent spectral index data informed previous year by the Planck satellite, which maps the galactic microwave background, was around 0.968, not that distantly the number you'd imagine to see if light and gravity ever traveled at dissimilar speeds. More figures from the Planck satellite will be able to demonstrate once and for all whether those figures match up.
If they don't, the team is satisfactory with that.
Magueijo told New Scientist, "That would be awesome, I won’t have to reason about these concepts again. This entire class of theories or concepts in which the speed of light differs with respect to the speed of gravity will be lined out."
But if the interstellar microwave backgrounds spectral index actually does match the projected value, then it would have massive effects on our own understanding of physics. At the moment, there's a big break between the fashion the Universe appears to function on the quantum scale which is quantum mechanics, and how it functions on the visible scale which is general relativity, and physicists are badly looking for a 'theory of quantum gravity' to try to tie the two.
Brooks says, "If there is an appropriate match between Magueijo’s hypothesis and observations, it could completefill this gap, addition to our understanding of the Universe’s initial moments. We have a model of the Cosmos that holds the idea there must be original physics at some fact. It is difficult, clearly, but I think eventually there will be a way of updating quantum gravity from this type of cosmology."
The study will be printed in Physical Review on November 28, but you can the full article right now at arXiv.org.