Michael Nielsen: belief

Transcript context

…In fact, Lorentz at the end of the 19th century, before Einstein, figures out the math of how you convert from one reference frame to another reference frame, and comes up with the Lorentz transformations, which is the basis of special relativity. But his interpretation is that you are converting from the ether reference frame to these non-privileged other reference frames if you’re moving relative to the ether. His interpretation of length contraction and time dilation is that this is the effect of moving through the ether, and you have this pressure. This pressure is warping clocks. It’s warping measures of length. The interesting thing here is that experimentally you cannot distinguish Lorentz’s interpretation from special relativity. I think that’s a strong statement. Lorentz introduces this quantity called local time, which he regards as... My understanding is he’s not trying to give a physical interpretation of this, but it’s what Einstein would later just recognize as time in another inertial reference frame. He’s not trying to attribute much physical meaning to it. I think Poincaré gets much closer later on to realizing that this is the time that’s registered by clocks. About forty-odd years later, people start doing these muon experiments where they see cosmic rays hit the top of the atmosphere. They produce a shower of muons, and you can look to see at different heights in the atmosphere how many of those muons remain. They decay over time, and a very strange thing happens, which is that they’re decaying way too slow. You expect they shouldn’t be able to last the whole way through the atmosphere at all. Their decay rate is too quick, if you were in a classical theory. But if in fact their time really has slowed down, it’s okay. In fact, the measured decay rates in 1940—and there have since been more accurate experiments done—match exactly what you expect from special relativity. That’s the kind of thing where if Lorentz had been alive—he’d been dead ten or so years at that point—it seems quite likely that he would have tried to save his theory by patching it up yet again, but it would have been a massive setback. It starts to just look like time—this thing that Lorentz introduced as a mathematical convenience—that’s actually what time is, for the muons at least. Then there’s a whole bunch of other experiments that show this very similar phenomenon. When was that experiment done?…

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