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The speed of light is constant, or so textbooks say. But some scientists are exploring the possibility that this cosmic speed limit changes, a consequence of the nature of the vacuum of space.OK so it looks like sometimes our understanding of the physical world can change. So far the only thing we know for sure, the only scientific fact that is set in stone and can not be negated or modified, the only one eternal truth is this: one hundred years ago the climate was at the one perfect spot that would ensure our survival. Any change from that 'sweet spot' spells our doom.
The definition of the speed of light has some broader implications for fields such as cosmology and astronomy, which assume a stable velocity for light over time. For instance, the speed of light comes up when measuring the fine structure constant (alpha), which defines the strength of the electromagnetic force. And a varying light speed would change the strengths of molecular bonds and the density of nuclear matter itself.
A non-constant speed of light could mean that estimates of the size of the universe might be off...