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Confirming Einstein scientists find spacetime foam not slowing down photons from faraway gamma-ray burst Update
" One hundred years after Albert Einstein formulated the general theory of relativity, an international team has proposed another experimental proof. In a paper published today in Nature Physics, researchers from the Hebrew University of Jerusalem, the Open University of Israel, Sapienza University of Rome, and University of Montpellier in France, describe a proof for one of the theory's basic assumptions: the idea that all light particles, or photons, propagate at exactly the same speed.
The researchers analyzed data, obtained by NASA's Fermi Gamma-ray Space Telescope, of the arrival times of photons from a distant gamma-ray burst. The data showed that photons traveling for billions of years from the distant burst toward Earth all arrived within a fraction of a second of each other.
This finding indicates that the photons all moved at the same speed, even though different photons had different energies. This is one of the best measurements ever of the independence of the speed of light from the energy of the light particles.
One of the attempts to reconcile the two theories is the idea of "space-time foam." According to this concept, on a microscopic scale space is not continuous, and instead it has a foam-like structure. The size of these foam elements is so tiny that it is difficult to imagine and is at present impossible to measure directly. However light particles that are traveling within this foam will be affected by the foamy structure, and this will cause them to propagate at slightly different speeds depending on their energy.
Yet this experiment shows otherwise. The fact that all the photons with different energies arrived with no time delay relative to each other indicates that such a foamy structure, if it exists at all, has a much smaller size than previously expected."
There's an awesome flash-based app online illustrating the relative size of things from space-time itself to the whole universe and beyond with lots of stuff in-between here:
Scale of Universe - Interactive Scale of the Universe Tool
" One hundred years after Albert Einstein formulated the general theory of relativity, an international team has proposed another experimental proof. In a paper published today in Nature Physics, researchers from the Hebrew University of Jerusalem, the Open University of Israel, Sapienza University of Rome, and University of Montpellier in France, describe a proof for one of the theory's basic assumptions: the idea that all light particles, or photons, propagate at exactly the same speed.
The researchers analyzed data, obtained by NASA's Fermi Gamma-ray Space Telescope, of the arrival times of photons from a distant gamma-ray burst. The data showed that photons traveling for billions of years from the distant burst toward Earth all arrived within a fraction of a second of each other.
This finding indicates that the photons all moved at the same speed, even though different photons had different energies. This is one of the best measurements ever of the independence of the speed of light from the energy of the light particles.
One of the attempts to reconcile the two theories is the idea of "space-time foam." According to this concept, on a microscopic scale space is not continuous, and instead it has a foam-like structure. The size of these foam elements is so tiny that it is difficult to imagine and is at present impossible to measure directly. However light particles that are traveling within this foam will be affected by the foamy structure, and this will cause them to propagate at slightly different speeds depending on their energy.
Yet this experiment shows otherwise. The fact that all the photons with different energies arrived with no time delay relative to each other indicates that such a foamy structure, if it exists at all, has a much smaller size than previously expected."
There's an awesome flash-based app online illustrating the relative size of things from space-time itself to the whole universe and beyond with lots of stuff in-between here:
Scale of Universe - Interactive Scale of the Universe Tool