标签: speed of light

Several years ago, my mom (now 80 years old) went to school for four years or so and got a degree in something or other. She didn't need it as she had retired years befor, but, as she said, she had never had the time or opportunity to get one earlier. I remember her telling me that one of here lecturers posed a question about atoms and she happily gave him an answer – only to discover that everything she knew was out of date. As she informed the lecturer, she had been taught about atoms three times in her life, and every time she was taught something different. The point of this story is that we tend to think we know it all—especially those of us how are involved in science and high-technology—but in reality we've still only scratched the surface of everything that there is to know. For example, I think most of us remember being taught at school that nothing can travel faster than the speed of light. Of course there is the awkward fact that when two particles are entangled at the quantum level, changes to one are instantaneously reflected in the other, which would appear to violate the speed of light. Some folks get around this by saying "It's only information that is propagated faster than light," to which I roll my eyes. If something is going faster than light, I don't care what it is – it's still going faster than light. (Einstein famously referred to entanglement as "Spukhafte Fernwirkung" or "Spooky action at a distance" .) Leaving quantum entanglement aside, however (which is what physicists like to do because they can't explain it – at least not to my satisfaction – although that might be because I'm an idiot), almost every physicist on the planet would say that no atomic particles – including light itself – can travel faster than the speed of light. At least this is what they would have said up until several days ago when scientist at CERN announced that they have, in fact, clocked neutrinos traveling faster than the speed of light ( Click here to see a full-up article). This reminds me about the current conundrum with regard to gravity. We currently have quantum physics to describe the actions of the very small – and we have Einsteinian gravity to describe the actions of the very large (well, the macro level which is larger than the quantum level) – but we haven't yet found a way to tie the two together. It's generally accepted that we don't yet have a complete picture, and one or both of these fundamental theories is either incorrect or incomplete. Now if you suggest that Einstein's theory of General Relativity is not 100% complete, most folks will look at you warily and tend to back away in case you are about to do something crazy. But think of my mother being taught different versions of "the truth" with regard to the atom. We are learning new things all the time. In 1687, for example, Sir Isaac Newton described his theory of Universal Gravitation. At first this theory seemed to completely describe the motions of the planets and the stars and led to the idea of a "clockwork universe". One very interesting aspect to all of this occurred when astronomers began to realise that there was a problem with regard to the "anomalous precession of the perihelion of the planet Mercury" (which is the clever way of saying that Mercury wasn't orbiting the Sun as expected). The folks of the time absolutely believed in the theory of Newtonian gravity, so they looked for an explanation in this context. The idea they came up with was that there was an – as yet undiscovered – planet (which they called Vulcan ) in orbit between the Sun and Mercury. Based on this proposal, many folks devoted huge amounts of effort and ingenuity trying to find a planet that we now know does not exist. Then Albert Einstein came along with his theory of General Relativity. Amongst other things, this accurately predicted the orbit of Mercury without the need to introduce a "fudge factor" in the form of a non-existent planet. For close to 100 years, General Relativity has been accepted by the majority of folks as fully describing gravity. But once again there's a problem. Astronomers have discovered that the stars at the edges of rotating galaxies are travelling much faster than they should be... so fast that they should fly off into space... but they don't. In order to address this, folks have come up with the concept of Dark Matter . The idea in a nutshell is that Dark Matter is something we can't "see" or "taste" or anything like that... except through its gravitational interactions (the posh way to say this is that "Dark Matter is hypothetical 'stuff' that does not interact with the electromagnetic force, but whose presence can be inferred from gravitational effects on visible matter" ). Doesn't this seem a little strange to you. It certainly does to me. The idea is that we are so accepting that General Relativity fully defines gravity that when we make observations that don't fit we simply invent some invisible matter to make everything work. And don't even get me started about other galaxies like NGC 4736 which seem to lack Dark Matter. So, if it turns out that the scientists at CERN are correct and some particles do travel faster than the speed of light, then we will have to come up with an explanation for this. Maybe this explanation will refine our understanding of gravity (maybe we will no longer need to use Dark Matter as a fudge factor—or maybe we will gain a better understanding of what Dark Matter actually is). Maybe it will redefine our understanding of quantum physics. Maybe it will allow us to finally come up with a Unified Field Theory that ties "quantum" and gravity together (or explains one in terms of the other, or vice versa ). And maybe ... just maybe ... we may one day have faster-than-light spaceships that will carry us across our galaxy and, possibly, across our universe... See also my book reviews on the following: A Short History of Nearly Everything by Bill Bryson The Smart Swarm by Peter Miller  

Several years ago, my mother (now 80 years old) studied for four years or so and got a degree in something or other. She didn't need it—she had retired years before—but as she said, she had never had the time or opportunity to get one earlier. I remember her telling me that one of here lecturers posed a question about atoms and she happily gave him an answer – only to discover that everything she knew was out of date. As she informed the lecturer, she had been taught about atoms three times in her life, and every time she was taught something different. The point of this story is that we tend to think we know it all—especially those of us how are involved in science and high-technology—but in reality we've still only scratched the surface of everything that there is to know. For example, I think most of us remember being taught at school that nothing can travel faster than the speed of light. Of course there is the awkward fact that when two particles are entangled at the quantum level, changes to one are instantaneously reflected in the other, which would appear to violate the speed of light. Some folks get around this by saying "It's only information that is propagated faster than light," to which I roll my eyes. If something is going faster than light, I don't care what it is – it's still going faster than light. (Einstein famously referred to entanglement as "Spukhafte Fernwirkung" or "Spooky action at a distance" .) Leaving quantum entanglement aside, however (which is what physicists like to do because they can't explain it – at least not to my satisfaction – although that might be because I'm an idiot), almost every physicist on the planet would say that no atomic particles – including light itself – can travel faster than the speed of light. At least this is what they would have said up until several days ago when scientist at CERN announced that they have, in fact, clocked neutrinos traveling faster than the speed of light ( Click here to see a full-up article). This reminds me about the current conundrum with regard to gravity. We currently have quantum physics to describe the actions of the very small – and we have Einsteinian gravity to describe the actions of the very large (well, the macro level which is larger than the quantum level) – but we haven't yet found a way to tie the two together. It's generally accepted that we don't yet have a complete picture, and one or both of these fundamental theories is either incorrect or incomplete. Now if you suggest that Einstein's theory of General Relativity is not 100% complete, most folks will look at you warily and tend to back away in case you are about to do something crazy. But think of my mother being taught different versions of "the truth" with regard to the atom. We are learning new things all the time. In 1687, for example, Sir Isaac Newton described his theory of Universal Gravitation. At first this theory seemed to completely describe the motions of the planets and the stars and led to the idea of a "clockwork universe". One very interesting aspect to all of this occurred when astronomers began to realise that there was a problem with regard to the "anomalous precession of the perihelion of the planet Mercury" (which is the clever way of saying that Mercury wasn't orbiting the Sun as expected). The folks of the time absolutely believed in the theory of Newtonian gravity, so they looked for an explanation in this context. The idea they came up with was that there was an – as yet undiscovered – planet (which they called Vulcan ) in orbit between the Sun and Mercury. Based on this proposal, many folks devoted huge amounts of effort and ingenuity trying to find a planet that we now know does not exist. Then Albert Einstein came along with his theory of General Relativity. Amongst other things, this accurately predicted the orbit of Mercury without the need to introduce a "fudge factor" in the form of a non-existent planet. For close to 100 years, General Relativity has been accepted by the majority of folks as fully describing gravity. But once again there's a problem. Astronomers have discovered that the stars at the edges of rotating galaxies are travelling much faster than they should be... so fast that they should fly off into space... but they don't. In order to address this, folks have come up with the concept of Dark Matter . The idea in a nutshell is that Dark Matter is something we can't "see" or "taste" or anything like that... except through its gravitational interactions (the posh way to say this is that "Dark Matter is hypothetical 'stuff' that does not interact with the electromagnetic force, but whose presence can be inferred from gravitational effects on visible matter" ). Doesn't this seem a little strange to you. It certainly does to me. The idea is that we are so accepting that General Relativity fully defines gravity that when we make observations that don't fit we simply invent some invisible matter to make everything work. And don't even get me started about other galaxies like NGC 4736 which seem to lack Dark Matter. So, if it turns out that the scientists at CERN are correct and some particles do travel faster than the speed of light, then we will have to come up with an explanation for this. Maybe this explanation will refine our understanding of gravity (maybe we will no longer need to use Dark Matter as a fudge factor—or maybe we will gain a better understanding of what Dark Matter actually is). Maybe it will redefine our understanding of quantum physics. Maybe it will allow us to finally come up with a Unified Field Theory that ties "quantum" and gravity together (or explains one in terms of the other, or vice versa ). And maybe ... just maybe ... we may one day have faster-than-light spaceships that will carry us across our galaxy and, possibly, across our universe... See also my book reviews on the following: A Short History of Nearly Everything by Bill Bryson The Smart Swarm by Peter Miller