(Once again, the evidence for either an “accelerating Universe” or a changing speed of light. Low redshifts increase linearly with distance, showing that the Space/Time expands. High redshifts increase non-linearly, leading to much speculation about repulsive energies. Supernova redshifts are the only direct evidence of acceleration. Prediction of GM=tc^3 and a slowing speed of light still fits the data precisely.)
Just as they once thought Earth’s position was centred in the Universe, scientists have thought that the speed of light was also fixed. When redshifts of distant supernovae appeared to have increased with respect to the speed of light, scientists assumed that c was constant and the Universe was accelerating! To explain this acceleration, they inferred a repulsive force, a “dark energy.”
At one time DE was science's hot topic. Grants and research jobs appeared destined for those who claimed its existence. After 11 years of speculation, repulsive energy has only caused science to decelerate. It has muscled promising projects, like the Constellation-X spacecraft, out of the funding queue. Though DE theories have spawned like epicycles, not one of them has demonstrated any staying power. The idea of acceleration has prevented scientists from seeing what a child could figure out, that the Universe is not accelerating but the speed of light is slowing down.
This month's SCIENTIFIC AMERICAN COVER asks: Does Dark Energy Really Exist?
“In short, we are very much in the dark about dark energy. Researchers are working on a number of ambitious ground and space-based missions to find and characterize dark energy, whatever it may be. To many, it is the greatest challenge facing modern cosmology.”
The article, by Oxford’s Timothy Clifton and Pedro Ferreira, highlights the notion that we could be living in a giant cosmic bubble. Our void would have a lower density than the rest of the Universe. Distant but visible parts of the universe would expand at a different rate, making the whole thing appear to accelerate from our point of view. The authors also compare this varying expansion rate with a variation in time. Such a variation in time would be mathematically equivalent to a changing speed of light.
Another sign that times are changing comes from the website of this Summer’s Paris conference, The Invisible Universe.
“Concerning dark energy and its repulsive effect on the dynamics of the universe, the question is even more complicated. This time, it seems that even the most adventurous extensions of the standard model and of the infinitely small are not capable to give a satisfactory candidate in terms of elementary constituents that can support its most peculiar property, negative pressure. This is why, dark energy but also dark matter are interpreted is some scientific literature not as fundamental constituents, but as fundamental modifications of our laws of physics.”
Having led science down a dead-end street, “dark energy” is starting to lose its luster. DE skeptics. Like those at Oxford, are finally getting their voices heard. Alternative ideas, like cosmic voids, are getting published. Next in line could be a changing speed of light.
Check out the latest Carnival of Space!
Labels: dark energy, speed of light