My wife and I are reading a book about physics in the early 1900s. It’s half history of science and half biography of some of the most famous physicists, and it’s good fun. But it got me thinking about the state of physics 120 years ago.
What we’d now call classical mechanics was fully settled for quite a while, and even the mysterious electricity and magnetism had been recently put to rest by Maxwell and Heaviside. It seemed like there was nothing left to explain for a while. And then all the doors broke wide open.
As much as I personally like Einstein’s relativity work, I’d say the most revolutionary change in perspective, and driver of the most research in the intervening century, was quantum mechanics. And how did it all start? In the strangest of ways – with Niels Bohr worrying about why hydrogen and helium gasses gave off particular colors when ionized, which lead to his model of the atom and the idea of energy in quantum packets. Or maybe it was De Broglie’s idea that electrons could behave like waves or magnets, from slit and cathode-ray experiments respectively, that lead to Heisenberg’s uncertainty principle.
Either way, the birth of the strangest and most profound physics revolution – quantum mechanics – came from answering some ridiculously simple and straightforward questions. Why does helium emit pink, and how do TVs work? (I know, they didn’t have TVs yet…) Nobody looking at these phenomena, apart or together, could have thought that answering them would have required a complete re-thinking of how we think about reality. And yet it did.
I can’t help but wonder if there are, in addition to the multi-bazillion dollar projects like the Large Hadron Collider or the James Webb Space Telescope, some simpler phenomena out there that we should be asking “why?” about. Are we in a similar quiet before the storm? Or is it really true that the way to keep pushing back the boundaries of our ignorance is through these mega-projects?
I would place Einstein’s 1905 paper on the photoelectric effect near or at the top. Among other things, what is known now as “Plank’s constant” and the quantization of light come from that paper.
I would too. And it’s also one of those, hey-look-at-this phenomena that turns into a mind-bending theory.
If you had told Einstein at the time that it was going to destroy the deterministic view of the world that he held… well, we all know how that went.
(Goes looking for old Hackaday writeup: https://hackaday.com/2017/08/31/way-to-go-einstein-his-time-spent-being-wrong/)
Well, the very salient attachment of most if not all quantum physicists to unitarity a.k.a. quantum information conservation, as got evidenced in the “firewall crisis” a couple years back, belies that their view really deserves calling “non-deterministic”. What is determinism if not information conservation (and conversely)?
What is the name of the book you are reading?
The Revolution of the last century is FAR from over. I dare say, it actually got put on a shelf for the last 50 years. QFT is full of holes, there’s so many free parameters in the theory that you can “explain” almost any property of particles retrofitting your data (as von Neumann famously said, with 4 parameters i can fit an elephant, and with 5 I can make it wiggle its trunk). And yet, as a theory it is surprisingly lacking explanatory power. It doesn’t really answer any of the fundamental questions like “what is an electron?” or “how does pair production actually work?”. We need to go back to the roots of QM if we want to make some progress.
I second this question ^^
I couldn’t find it in English translation yet, so I didn’t bother calling it out by name.
For you German-readers out there: Das Zeitalter der Unschaerfe
https://www.klett-cotta.de/buch/Leben/Das_Zeitalter_der_Unschaerfe/144073
It’s more about the physicists involved and their personalities and the interplay than being a history of physics — which is actually very nice for summer reading. :)
Thanks a lot – some of your readers are German. ;)
Link ot the book? I enjoyed Bill Bryson’s Short History of Nearly Everything.
https://smile.amazon.com/Short-History-Nearly-Everything-ebook/dp/B000FBFNII/ref=sr_1_1
But it is more than just physics and the section on plate tectonics is outstanding.
Thanks for that link! My reading list gets even longer than it already is.
Can confirm. Bill Bryson’s Short History of Nearly Everything is right up there with workers by James Burke.
Well, are you leaving out Plank’s quest for light-bulb efficiency and Einstein’s explanation for light-based noise on electronic valves.
The two works that actually kickstarted Quantum Mechanics.
I think that fluid dynamics has a lot of growth in it yet; the questions like “does hot water freeze before cold water?” and “does anybody really understand how planes fly?” show the cracks in our current understanding. The interlinked phenomenon of pressure and turbulence and things like “speed of sound in various materiel” will, I hope, someday be as well understood and exploited as electromagnetic effects.
Pressure, especially, affects chemistry in ways that we take advantage of; but don’t understand in an overarching theory kind of way that would explain for example what kind of reactions might be happening 20 miles underground. We’re deeply ignorant of the things that might be happening in bigger planets and stars. (No slight intended for the practitioners of Astrophysics: they know more than me, I’m sure; but i doubt they’d assert that they know enough yet.)
Actually, we understand how planes fly very precisely… it is just that the simplified explanation of how wings work is wrong. You can actually very simply derive an equation for the geometry curvature and the pressure gradient. (Basic fluid mechanics 1o1). The Mpemba effect (hot water freezing before cold water) has also some quite good explanations… More interessting are all the phenomena with turbulence at high Reynolds numbers where we still lack the computational power to compute flow fields without modelling (simplifying) the problem. Think of rough surfaces, primary atomization of liquids, convective heat transfer aso. Still, the physical phenomena are quite well understood, it’s just because of the shape of the equations that we can’t easily predict.
The biggest breakthough would be coming from mathematics: if we find a way to solve the general 3-D Navier-Stokes equations analytically (conservation of momentum and mass in viscous fluids). That would give us instant solutions for technical problems that right now can easily require hundreds of CPUs for days and weeks to approximate solutions.
The Mpemba effect’s best explanation is that it was just wrong. There’s been quite a bit of systematic reviews over the years and basically the universal conclusion is that it was just a mistake or poorly controlled setup.
Did you know Einstein also contributed to quantum theory.
He won the Nobel Prize in Physics for his Photo-Electric Effect.
Which proved the wave particle of photons.
His other published work also helped it along.
Einstein may have had his doubts, but he contributed many things used in quantum physics today.
One thing one of my professors told me was getting to know what you don’t know is half the battle!
Gravity
I agree. It’s pretty amazing that physics all started with explorations of gravity to explain planetary motion, but we still don’t have a complete understanding of it.
We actually understand gravity better than (or as good as) the other forces! The energy scales that you need to get to before our understanding of gravity falls apart is *way* beyond where our understanding of the other forces falls apart.
It’s common popsci knowledge now that you can’t merge GR and QFT, but… you kinda can. You can happily write down a quantum field theory of gravity. It’ll work fine at low energies! It’s the same thing that happened with the nuclear forces.
The problem is that the energy scale you’re interested in (GUT scale) you know it won’t work. But neither will the other forces! Our best guess as to the reason for the huge neutrino mass gap is that there’s a “hidden” neutrino out at GUT scale, meaning… effing *everything* breaks down there.
So basically we’ve got theories that’ll work fine for all the forces up until you get to absurd energies. Gravity just gets credit because it’s boring and friggin’ nothing happens to it until then.
I should actually point out I’m being generous and suggesting interesting stuff happens with gravity at GUT scale (about a megajoule) and not Planck scale (about a gigajoule). All hell could break loose with the other interactions way before gravity ever gets involved.
Nope, modern Physics has started from Archimede’s Principle back in ancient Greece. So fluid mechanics started first before gravity.
Yeah. What is the speed of gravity? Instantaneous? Speed of light? :)
GW170817 and the near-simultaneous observation of gamma rays constrains the speed of gravity to with a few parts per quadrillion of the speed of light, under the assumption that they were emitted effectively simultaneously.
Even totally ignoring that assumption, though, you can use observations with more than 3 GW detectors to constrain the speed of gravity to basically the speed of light as well.
Thanks. This means that gravity disturbance at Pluto would take hours to affect the Earth? And that whatever gravity changes happen in other galaxies, they would take millions or billions of years to affect us?
It’d take exactly as long as light would take, give or take a few parts per quadrillion. So yeah, hours/millions of years from our point of view. Better way to say it is if you want to communicate with Pluto using gravitational waves, the round-trip time would be many hours.
There’s some difficulty in thinking about “speed of gravity” when you think about it in a static sense (“what direction does the force point”) but this is just a reference frame issue (and identical to electricity). This often leads to people saying “the speed of light has to be infinite in Newtonian gravity, you need GR to make gravity a finite speed” but that’s bad reasoning. There are plenty of simple relativistic versions of gravity that would work, they just don’t match careful orbit measurements (e.g. precession of Mercury).
I created an instrument back in the 1970’s that I called a Rotating Graviometer. It could directly measure the speed of gravity if ever built full size. It would have been costly and we decided it was so unlikely to not be the speed of light that I let it go. I coulda been famous! It probably needed large amounts of tungsten and or depleted uraniumin order to get enough mass in the rotating parts.
And large amounts of grant money?
B^)
Speed of light. If our star suddenly disappeared, we’d continue to see it and orbit it for about 8 minutes after it disappeared. I said that at a daytime sunspot and solar prominence public viewing event of our astronomy club and many were surprised. That came up from discussion of the excellent Larry Niven sci-fi short story, “Inconstant Moon.”
For sure AI and its relationship to consciousness are breaking open right now.
Agreed. Also, “Follow the money” for developments. If there’s not much cash being invested in new and interesting physics then nothing mush of will get discovered and it will look fairly gloomy compared to other areas of interest. Also, correct me if I’m wrong, but investment in cutting edge physics is crazy expensive. If anybody has figures that can compare investment in physics to investment in Ai, that would be interesting.
Desktop Accelerators aka Proton Packs. :-)
Tge entire concept of the scientific method seems for many to be replaced with the Theory about “x-> grant funding to prove “x” -> directed research request to prove condition “y” about “x” -> paper published which explains and validates “y” and establishes “y” relationship to “x”
> Or maybe it was De Broglie’s idea that electrons could behave like waves or magnets, from slit and cathode-ray experiments respectively, that lead to Heisenberg’s uncertainty principle
I think that should be “waves or particles”
Here’s one for you: why is the speed of light in vacuum the speed that it seems to be? (That’ll quickly go down the rabbit hole as one tries to figure out why certain constants are what they are.)
There are some philosophical implications to “why are the numbers exactly what they are,” but as long as the values are constant then the anthropogenic principle seems like a good answer. The speed of light being so close to 300,000km/s is only because of how we defined both the meter and the second. That any value comes close to a nice, neat, integer is down to the fundamental constants we built up from and the measurements we started with.
Kind of….?
The rabbit hole you go down here actually kind of should take you *away* from the constants themselves (which have arbitrary units) and more towards fundamental (unit less) constants. For instance, the fine structure constant, or the ratios between the various energy scales in particle physics. Those especially tend to be really interesting: like, why the heck is there such a massive gulf between electron/neutrino masses when there’s virtually none between up/down quark masses.
There’s an interesting paper from a while ago that pointed out, for instance, that you could, in fact, arbitrarily view the expansion of the Universe as a change in fundamental constants over time because we can’t actually *measure* them independently (everything we measure is effectively a ratio). It doesn’t really have any effect – in some sense it’s just a viewpoint difference – but it’s interesting to think of other similar examples.
I’d argue that mu zero and associated fine structure constant, which bear on speed of light derivation have not changed since about 300 Million years after “big bang” event, since…
https://en.wikipedia.org/wiki/GLASS-z13
That would not have happened. As apparently the tiniest fraction of a percent tweak in that causes chemistry and nuclear physics to fall apart.
That’s a bit circular: there are ways you can tweak the fine structure constant *and other constants* and nothing changes.
It’s like thinking you can mess with the mass of an electron and nothing else would change. That’s just one way to do it (the *coupling* to the Higgs field) but not the only way (you can alter the Higgs field itself). The fine structure constant is *in some sense* a free parameter in the Standard Model but that’s just a choice.
“nothing changes” is too strong, I should say “things don’t go boom.”
Isn’t there an alternative unit system that reduces everything down to plancks distance or constant or whatever. I think it is planck units or something. Basically everything gets divided down so that it is only expressed in 1 unit, and ratios rake care of everything else. I dont think everything can be done in it and it removes alot of elegance we are accustomed to but apparently adds a layer of elegance in new places. Hmm my comment feels very empty of solid fact.
The whole dark matter/dark energy thing is known to be a placeholder for an unknown area. When progress starts in that area, that has the potential to upend a lot of current assumptions.
Not the way the public sees it.
i don’t know how to guess at what might be hidden behind it, but it’s obvious that cosmology’s unknowns (dark matter, dark energy) are eventually going to turn everything upside down when they become knowns.
There are four big “there have to be more ‘things’ out there” parts:
1. Dark energy (weird vacuum or gravity stuff)
2. Dark matter (weird alternate particle physics)
3. Neutrino masses (high-energy weirdness in standard particle physics)
4. Cosmic inflation (pick one of the above or even something new!)
There are other things which annoy theorists, but the above 4 things come from experimental observations and currently cannot be explained by anything in the Standard Model. There’s one other puzzle (why are we made of matter and not antimatter) but that could still be explained in the Standard Model. If not then that’d be 5.
May I suggest you read the work of Milo Wolff (wave structure of matter) and Uri Ivamov (rhytmodynamics). Essentially, both postulate that everything we see in the universe–matter and energy–and all the forces we see–magnetism, elactrostatic forces, nuclear forces, inertia, gravity, the whole 9 yards–are simply manifestations of interference patterns in the aether.
I read somewhere that Intel was preferentially using Wolff’s work to predict electronic behavior at the atomic level, because it better predicted real-world behavior than quantum mechanics. Perhaps there is sonething to this.
Really odd not to mention the name of the book mentioned in the first paragraph!
Otherwise, gravity seems to be the big mystery.
How does Elliot and his wife read the book at the same time? Seems like they may have accidentally stumbled on an unsolved mystery in physics not yet even realised as being a ‘Thing’. Could even be evidence of time travel: Elliot reads a chapter of the book, passes it to his wife, she goes back in time and reads the same chapter at the same time.
Or one of the two reads it out loud.
It may have something to do with women being capable of full-duplex communication. Two women can talk at once to each other while fully hearing what the other is saying.
I have suspected for a very long time that at least a few women i’ve known are capable of true multitasking, as opposed to everyone else being task/context switchers…..but I eventually learned not to propose testing my hypothesis…
They each have a copy of the book. Perhaps a digital edition on a tablet or phone.
This is actually it! She likes to read on e-reader, and I in book form. She gave me the book for my birthday, picked it up casually, and ended up liking it enough that she got it on e-reader. So we have two copies.
It’s not some kind of violation of the Pauli exclusion principle…
I feel like we’re kind of in a lull, discovery wise. Nothing seems to be ‘new’ any more, just incremental improvements to that’s already out there.
“The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but ‘Hmmm… That’s funny…’” (Asimov)
That’s also the most fearful phrase to hear when debugging software, along with ‘…but that should never have worked’
Maybe the “storm” is the collapse of civilization.
After the age of enlightenment, age of darkness again? Because both religion and hurt feelings are now becoming more important than scientific facts again? Science is attacked now from both sides.
I fear you may be right. Ignorance used to be something to be ashamed of … now it’s practically a badge of honor, at least among far too many politicians and the multitudes who vote for them.
Stephenson has a bit in Anthem about how societies will inherently reject technology that is complicated enough that only an elite handful understand how it works.
Which explains why smart phones never took off.
Hilarious. :)
On the other hand, consider nuclear energy. When it goes wrong, it goes wrong in ways that are obviously terrible, so it’s largely been rejected by society.
Fossil fuels, on the other hand… when they work as designed, the consequences are worse on a much larger scale, but in a less obvious way. So here we are, burning coal and oil and gas instead of finding ways to split atoms more safely and with less waste.
Ignorance as a badge of honour seems to be a cyclical trend, and in certain countries more than others.
Sadly, yes, it seems like science itself needs to be rediscovered and appreciated.
The scope of physics and religion sometimes seems to get mixed up: while religion is about the Why and telling the difference between good and bad, the physics is about the How and telling the difference between correct and incorrect. So the science uses math to describe the nature, and the religion/philosophy tells you why that works (since math and physics are fundamentally antipodal in the sense that the one accepts only logic as proof, and the other accepts only measurements, this is quite remarkable).
There is no way to discern good from bad in science, as well as there is no way to proof a physical law in religion. You don’t read the bible to learn math or physics, as well as you don’t read a physics book to learn about god. It is wise to know the scope and the borders, for example, how do you explain the Big Bang, the forming of particles and how the universe became transparent to the people several thousand years ago? See Gen 1,1-3. Want to know, why the Big Bang happened? Good luck with science. Want to know how to describe atoms? Good luck with religion.
Lose one or both of science and/or religion, and have fun with hurt feelings and battling the reality around you.
Note that there is no way to completely scientifically proof a religion, and no way to alter the truth by believing in this or that religion. So it is useless to stop believing in a specific religion, because one doesn’t like it, but it is legit to do so, when you come to the conclusion that this religion is not true. In this sense todays scientists and medieval monks do the same: they try to find the truth behind what they read and observe. As well as the monks couldn’t even dream of our scientific knowledge, I’m sure we can’t even dream of their religious knowledge (but we may read their books, like we read math books, for not having to come up with everything ourselves).
Interesting views, thank you.
Shows why their isn’t an either/or but a complement. Some of our sciences comes from religious practitioners. e.g. Mendel, etc.
Fides et Ratio
“Age of darkness…”
Was thinking more https://en.wikipedia.org/wiki/The_Structure_of_Scientific_Revolutions
Why is time dilated by both velocity and gravity and only by velocity and gravity.
These questions don’t really have a “why” answer. They just have behaviors we can measure and predict. I’ll take a jab at it. For velocity it is a consequence of a speed limit for light. In looking at light in a rest frame and an inertial from moving relative to the rest frame, there is a conflict with the measurements and the only parameter that can explain the result is time that bends. And testing shows that is what happens.
With gravity, the properties of space change. Here again, measurements don’t work like they do in “flat” space-time and time that bends makes the math work. Measurements show this to be true even locally on the Earth.
You can approach it in other ways, like distances and angles for geometric objects do not add up if you live on and draw them on the surface of a sphere – or in curved space-time. Motions and distances will come out “wrong” unless you allow variable time rates.
Henry’s constant is useless for nearly every application. That could be something to change.
Indeed I agree so much with the nonesense of blowing zillions of money into this megascientific madness, we have not understood the holographic principle of the universe in its basics it allows me to extract and explore the unseen within any photograph. My smartphone has become a holographic processor which allows me to dive close to black holes and extract exoplanets visually. Please find the link to my astrobin profile quantOnaut to get an example of the possibilities simply by a tweaked smartphone display 😅
I was really enjoying this piece and then it just abruptly stopped. It made me sad. Yet it reminded me that as we become adults and age, we forget to ask the most basic questions like “but why?”
I hope the author gives it some more thought and returns with a longer piece.
“Hubble tension” is an interesting open issue that I suspect will lead to some changes in our understanding of cosmology.
https://platosrealm.blog/2020/05/05/the-hubble-tension-a-sign-of-new-physics-in-cosmology/
https://www.scientificamerican.com/article/hubble-tension-headache-clashing-measurements-make-the-universes-expansion-a-lingering-mystery/
“if there are… …some simpler phenomena out there that we should be asking ‘why?’ about.”
Many, most certainly. Top of all, consciousness (subjective awareness).
Interesting topic. I’ve been thinking a lot lately about space travel and have a question that I cannot find the answer to. Its hypothetical and for the sake of debate.
If an astrophysicist or a theoretical physicist saw a transversable wormhole in our sky during the night up close and in detail would that help them to solve the Black Hole Information Paradox? If yes or no, why?
It’s kindof an awkward question, but I’ll say “no… ish”: the information paradox is a *theoretical* issue, not an experimental one. It’s a problem with naive combinations of general relativity and quantum mechanics. It shouldn’t even be called the “black hole information paradox” because it’s really the “simple event horizon paradox.” It’s only related to *real* black holes tangentially – because our knowledge of actual black holes is so bad (because you can barely observe them at all) they get treated purely as theoretical constructs. What I mean is that you can’t do experiments to try to bound the entropy behavior of *actual* black holes. Instead, it’s just this theoretical issue that’s basically the same as physicists starting with “assume the cow is a sphere.”
The reason why the discovery of a traversable wormhole wouldn’t do anything to help that is that it would just break all of the rest of physics anyway. No one knows how to make a traversable wormhole without matter that follows totally different physics, so the existence of one would imply that all of the energy conditions that we founded theories of simple black hole behavior on are wrong. There are, in fact, people trying to prove (and some who claim they have proved) that you *cannot* have traversable wormholes with matter that we know of (which means “within the laws of physics we know of”).
(side note: science fiction often pretends that you can make FTL drives and wormholes with “exotic matter” because that’s the term that theorists use, but “exotic matter” isn’t a thing you can make. Exotic matter is “stuff that behaves exotically” and if you have that then you have entirely different physics than we currently have)
I think the TL;DR version of what I’m saying is that it wouldn’t help because it would render the entire discussion moot. It’d break the entire framework of the conversation – physics like that would mean that the entire “simple event horizon” version of a black hole is pointless.
The article and comments made me think of James Blish’s ‘Cities in Flight’ when it was decided that various crack-pot ideas might spark unexpected progress in unpredictable directions. Perhaps we’re reaching such a phase.
Sorry, folks: the first one to (reluctantly) talk about quanta was Planck, in his work about black body radiation. Yes, Einstein and Bohr were important too, without them, Planck’s would look just like a strange mathematical device.
Science is collective work. There are always giant’s shoulders around.
I can recommend Pullizer-winning ‘The making of the Atom Bomb’ by Richard Rhodes.
It gets around a lot of the discoveries from Rutherford onwards.
The reason for huge budget instruments like the LHC and JWST is because we’ve been very good at ferreting out all the answers to low energy “well, that’s funny…” questions. This leaves us with questions out at the extremes, which require more extreme instruments to start probing.