# If neutrinos move faster than light, is time travel possible?

## Question

Hi Chris,

The question I'd really like to ask is... Following the reconfirmed results that a neutrino can travel faster than light, why is it then assumed that travelling through time is possible? A neutrino coming from the sun would still take several minutes to reach Earth, say, even if it does get here faster then a ray of light that left at the same time. In the media I haven't found the answer to this question, I just come across the assumption!

Cheers,

Shane Record

## Answer

Dave - Essentially, if you take all of Einstein's equations - the first thing it says is that to go at the speed of light, you need an infinite amount of energy which kind of means if you go any faster than the speed of light, if you get out of the speed of light, you need, in fact, energy and all the equations explode, and everything breaks. But if you put the numbers where you're going faster than the speed of light in there, you sort of get some results which seem a bit more meaningful. It gives the appearance that light - that time appears to be going backwards for you if you are travelling faster than light. And it essentially makes the direction which you're travelling in seem to look a bit - mathematically - it look more like a time axis and certain time look more like a normal axis. So, it's possible that space and time gets really confused for you if you're going faster than the speed of light. But fundamentally, what I've said at the beginning was that all of our maths, our physics, breaks if you can go faster than the speed of light which means we don't really know until we can actually test it, and we get a better theory.

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