Merry Newtonmas, Everyone!
In past years, I’ve compared science to a gift: the ideal gift for the puzzle-fan, one that keeps giving new puzzles. I think people might not appreciate the scale of that gift, though.
Maybe you’ve heard the old joke that studying for a PhD means learning more and more about less and less until you know absolutely everything about nothing at all. This joke is overstating things: even when you’ve specialized down to nothing at all, you still won’t know everything.
If you read the history of science, it might feel like there are only a few important things going on at a time. You notice the simultaneous discoveries, like calculus from Newton and Liebniz and natural selection from Darwin and Wallace. You can get the impression that everyone was working on a few things, the things that would make it into the textbooks. In fact, though, there was always a lot to research, always many interesting things going on at once. As a scientist, you can’t escape this. Even if you focus on your own little area, on a few topics you care about, even in a small field, there will always be more going on than you can keep up with.
This is especially clear around the holiday season. As everyone tries to get results out before leaving on vacation, there is a tidal wave of new content. I have five papers open on my laptop right now (after closing four or so), and some recorded talks I keep meaning to watch. Two of the papers are the kind of simultaneous discovery I mentioned: two different groups noticing that what might seem like an obvious fact – that in classical physics, unlike in quantum, one can have zero uncertainty – has unexpected implications for our kind of calculations. (A third group got there too, but hasn’t published yet.) It’s a link I would never have expected, and with three groups coming at it independently you’d think it would be the only thing to pay attention to: but even in the same sub-sub-sub-field, there are other things going on that are just as cool! It’s wild, and it’s not some special quirk of my area: that’s science, for all us scientists. No matter how much you expect it to give you, you’ll get more, lifetimes and lifetimes worth. That’s a Newtonmas gift to satisfy anyone.
4 gravitons 
I am of the “mere mortal” variety but very appreciative of your posts which are incredibly amazing. The concept of using more advanced mathematical tools almost like APIs to compress or simplify collider interactions is fascinating. You also explain your work, conferences, and research in a very human way as a true expert. In my work, we continue to build more abstract API libraries in machine learning to perform more and more sophisticated tasks with fewer lines of code. I believe we are both on the right track. Merry Christmas to you and your family.
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Merry Newtomas to you too!
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“what might seem like an obvious fact – that in classical physics, unlike in quantum, one can have zero uncertainty – has unexpected implications for our kind of calculations” – Why do you just throw this out there without an explanation? https://i.kym-cdn.com/photos/images/original/000/097/663/whywouldyoudothat.jpg
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Because I haven’t finished reading the paper/watching the talk yet. 😉
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For example, one thing I only just noticed is that the two papers share an author 😛
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You say:
“in classical physics, unlike in quantum, one can have zero uncertainty”
I think it is important to specify what this uncertainty is about. The quantum state provides a description of possible measurement results. The classical state describes the system as it is, NOT the results of future measurements on that system. Yes, the classical state of an electron does not have any uncertainty, but once you try to predict (classically) the results of measurements (position, momentum) I expect an uncertainty to appear as a result of:
Newton’s third law.
Our initial uncertainty regarding the exact *microscopic) state of the apparatus used for that measurement.
What do you think?
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The short answer is that I should have added an “in principle” to that statement. In practice, every classical measurement has some uncertainty, yes. But in a theoretical context, one can set up a classical calculation with zero uncertainty, when the corresponding quantum calculation would be uncertain. (In even shorter terms, no, that quote is unrelated to our old discussions about interpretations 😛 )
To go into a little more detail, these people are focusing on a particular set of observables that are (chosen/designed to be) meaningful on both a classical or a quantum level. An example from one of these papers: two charged particles collide, what is the field strength of the radiation? In quantum mechanics you compute an expectation value, in classical physics there should be one exact answer for each configuration of particles. But in each case it’s a meaningful question.
On a purely theoretical level, you can specify the kinematics of the incoming particles, and abstract away the measurement device. You then expect no classical uncertainty. Since the corresponding quantum problem has uncertainty, you expect that uncertainty to vanish as Planck’s constant goes to zero. And the upshot of these papers is that it does, but it has some unexpected implications.
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