The answer that brought this question in my mind:
https://physics.stackexchange.com/a/298975/249090
Cant it be that the way we measure the speeds cant measure them faster than that? And for that matter, how is the speed for such high speed particles measured actually?
"I'm sorry, officer. There's no way I could have been going that fast. You see, my speedometer only goes up to 85mph."
Yeah. That doesn't work too well with the police. It doesn't work all that well in physics either. It would be an enormous ethical quagmire for the entire scientific community to try to claim nothing travels faster than light when actually we just have shoddy equipment that can't measure any better than that.
Now it is possible for all of science to be wrong. You, yourself, may be the person who thinks up something nobody has ever thought of which permits some particular particle to go faster than the speed of light. It's always possible that we just didn't think of something. It's happened before, and it will happen again. Repeatedly.
However, we are good at measuring things. Measuring the speed of a particle over time is relatively straight forward. One approach is simply to put it on a race track and observe when it reaches a fixed point every time it circles around. You know the length of the track, so you can measure the speed.
Another approach is to compare it against light directly. Fire a pulse of light next to the particles, and have both particle and light go through two gates. Each gate records the difference in time between when the light hit and when the particle hit. If you subtract the delta at the end of the track from the delta at the start of the track, you can find out whether the particle gained any distance on the light (hint: it's never happend)
We can measure things that are faster than light. The speed of dark is faster than the speed of light. That's a very loaded phrasing, and I encourage you to watch the video to see exactly what I mean. But in general, there are ways to make a signal appear along a line faster than the speed of light, even though the particles/photons conveying that signal were traveling slower.
Consider this experiment. Hold a piece of paper up like you were reading it. Now push the right edge a little further out, so that it's further from you than the left side is (not by much... maybe by an inch). Now imagine your eye was a laser, lighting up the paper with a pulse. The photons will hit the left side of the paper first, because the paper is closer there. They'll hit the right side a little later, when they travel that extra inch.
However, while the light beam only had to travel an extra inch, the paper is 8 inches wide. Thus, if you look at the timing of the signal caused by your laser pulse, you find it must be going 8 times faster than light!
Its a parlor trick. We all know that the light traveled exactly a long as it took to get from your eye to the paper. But it points out that we can generate signals that propagate faster than light, without breaking the laws of physics. And, to your question, we can measure this effect and get the results we expected. You would be astonished how exacting metrologists can be when ensuring that our experimental devices are measuring precisely what we claim they are measuring.
Thus we can demonstrate that we can measure signals propagating faster than the speed of light. We just have to configure the experiment properly. When we measure the speed of particles, we intentionally don't measure it in this parlor trick setup. We construct the experiment to ensure the signal does not propagate any faster than the particle. Typically, we do this by making the signal be the particle, and we observe it when it reaches the end of the test setup, like listening for the sweet smack of a baseball coming to rest inside a baseball glove.
So we can do the measurements of things faster than light. We can prove that. We've simply never seen a particle travel that fast. Indeed, we have found an enormous volume of evidence suggesting they can't.
In particle physics there exists the standard model, which is an encapsulation of an enormous amount of measurements and observations , and in addition its predictions are successful. This model is based on both quantum mechanics and special relativity. In special relativity nothing goes faster than light. The whole edifice would be broken if the particles composing it could go faster than c. In this sense the whole standard model is a measurement of the limiting function of c.This includes the particles we know up to now.
Now this is a model, extensions of the model bring up new particles that are always going faster than c, the tachyons, and people are looking for them, unsuccessfully up to now.
A few years ago the whole physics community was in turmoil over an experiment that had neutrinos traveling faster than light. The measurement used the distance between production and detection and complicated mathematics to come out with this observation, but unfortunately it was a measurement error.
The OPERA team made headlines after they suggested neutrinos traveled 0.002% faster than light, thus violating Einstein's theory of special relativity. The OPERA results were debunked months ago, however. So instead of the nail in the coffin of faster-than-light neutrinos, the new suite of results is more like the sod planted atop their grave.
I say "unfortunately", because particle physicists work hard to find disagreements with standard models so that the knowledge of nature expands.
