# FTL Neutrinos

1. Mar 7, 2012

### QuantumLex

Okay, so, the FTL neutrino result from the OPERA experiment is still being questioned, and that's good. But, assuming they really did travel faster than light, I have a few questions:

1.
Didn't we learn that if things travel faster than light then they travel back in time? So if the neutrinos travelled faster than light and arrived a little bit earlier than light, then they travelled back in time for that little bit.
What if we place the detector further away? Wouldn't the resulting arrival time then be earlier still, or at least "earlier" in that its velocity will be measured to be a greater multiplier of the speed of light, even if the actual detection occurred later in time (i.e., at 1x kilometers its detected velocity would be, say, 1.0001c, and at 10x kilometers, its detected velocity would be, say, 1.0010c)?

2.
The measured arrival time of neutrinos and light from supernova SN 1987A as being basically equal, is taken as evidence that neutrinos travel at the speed of light. But the question has been postulated of whether the speed of neutrinos is linked to their energy. So, if the neutrinos and photons were created in the same reaction, wouldn’t the neutrinos and light from SN 1987A be expected to reach us at the same time (this says nothing about their speed except in relation to each other).

3.
There's a difference in the type of neutrinos detected from SN 1987A and in the OPERA experiment. The question remains whether the type of neutrino matters (i.e., whether muon neutrinos and electron neutrinos travel at different speeds). There is also the additional factor that in OPERA the neutrinos started out as muon neutrinos but were detected as electron neutrinos. What is the effect of decay on velocity?

Last edited: Mar 7, 2012
2. Mar 7, 2012

### Ryan_m_b

Staff Emeritus