Light speed: Flying into fantasy
What if particles really can exceed the speed of light?
It is a fascinating and provocative question.
But first, it should be said that Thursday's news that physicists have seen subatomic particles called neutrinos exceed the Universe's speed limit is a picture of science still at work.
The researchers at Cern in Switzerland and Gran Sasso in Italy have tried really hard to find what they might be doing wrong - over three years and thousands of experiments - because they can hardly believe what they are seeing.
The publication of their results is a call for help to pick holes in their methods, and save physics as we now know it.
"The scientists are right to be extremely cautious about interpreting these findings," said Jim Al-Khalili, a physicist from the University of Surrey, who suggested that a simple error in the measurement is probably the source of all the fuss.
But he has gone further.
"So let me put my money where my mouth is: if the Cern experiment proves to be correct and neutrinos have broken the speed of light, I will eat my boxer shorts on live TV."
Let us be clear: it would be a tremendously exciting time for physics, and a daunting one for physicists, but it is not going to change the price of milk.
Perhaps the most exciting thing is that time travel would look more feasible.
The speed of light is the cornerstone in Einstein's theory of special relativity, which is what gives us the concept of causality: causes precede effects, wherever you are.
Remove that requirement, and time becomes a much more fluid thing than the one-way arrow we think it to be.
If an effect can precede a cause, showers of neutrinos might arrive here on Earth before a supernova actually kicks off on the other side of the galaxy.
OK, here's what we really want: Back to the Future-style popping around in time might be within our reach.
It gets weirder. Einstein may not have been wrong if we concede that there are extra dimensions of space that particles can nip into and out of, and some theories have already been around a while that suggest it.
"They're not mainstream theories, but they're fine," Brian Cox, a physicist who has worked at Cern, told the BBC.
"Let's say you go from London to Sydney - you fly around the Earth," Prof Cox explained. "The other way to do it is to go through digging a big tunnel straight through the Earth, and that's the shortcut.
"In some ways extra dimensions can behave like that and ... the neutrinos could be taking a shortcut through another dimension."
That leads neatly on to the "wormholes" popularised in science fiction, connecting one place in space to another vastly distant one.
The list goes on - and there is a host of other implications, most of which arise because the speed of light figures in so many equations in science.
It holds all of quantum mechanics together, for example, and that has given us the modern era of electronics, the internet, and the gizmo on which you are reading this.
Get an information-carrying particle going faster than light, and you change computing altogether. How about solving tomorrow's problems today?
This, again, is all speculation. But even Cern's director of research Sergio Bertolucci briefly got into the game.
"We all like the idea of travel in time, but it would be very difficult," he told the BBC.
"You can imagine: we'll never get old - politicians would stay young forever."
But Antonio Ereditato, part of the Opera collaboration that found the curious result, is holding fire on what it all might mean if true.
"I would prefer not to elaborate on that," he said.
"I'm sure that there are many, many colleagues in our community who will start to elaborate, but our task for the moment is one step behind: to make sure - absolutely sure - that this is a real effect and as solid as we think.
"But this must be confirmed by other colleagues. This is the way our work is done."