Fundamental physics sees worlds in grains of sand and infinities in hours(economist.com)
economist.com
Fundamental physics sees worlds in grains of sand and infinities in hours
https://www.economist.com/leaders/2021/08/28/fundamental-physics-is-humanitys-most-extraordinary-achievement
17 comments
what does it really mean to "orbit the sun?" We follow an elliptical path around the sun from the perspective of the reference frame of the sun. From the perspective of the reference frame of the earth the sun and planets move around us in complicated epicycles. From the perspective of an external reference frame, outside the solar system, the earth moves in a sinusoidal manner as the sun orbits the galaxy. At the largest scale space is expanding and no orbits are cyclical. We never return to the same space twice. Rotation is said to be absolute while linear motion is relative but since space is expanding at the largest space and time scales are not orbits illusory? Due to gravity objects follow curved paths through space and time as the fabric of the Universe expands but if you think about it you never really return to the same place twice so might also at large scales apparent angular motion also be relative or convergent on linear motion, e.g. through fourier decomposition?
I don't think there should have been a reason for any of these discoveries to be mind-boggling. It's the premise that we knew anything before we knew, e.g. religious indoctrination that made it so. Would the confirmation of aliens be mind-boggling today? For some yes, why?
But on the sheer vastness of what we didn't know, it seems like that's shrinking in relevance. There are of course dark areas, black holes, quantum gravity, and so on, but they are farther and farther at the edges of scale. Not as world-changing as discovering the second island after your own, or a continent, planet, or solar system. Each one has less practical impact.
But on the sheer vastness of what we didn't know, it seems like that's shrinking in relevance. There are of course dark areas, black holes, quantum gravity, and so on, but they are farther and farther at the edges of scale. Not as world-changing as discovering the second island after your own, or a continent, planet, or solar system. Each one has less practical impact.
I think the OPs point was not that they were intellectually difficult to comprehend, rather each discovery radically alters your perspective of the world.
If we were to discover with certainty that our universe were one of many, it would completely blow my mind.
If we were to discover with certainty that our universe were one of many, it would completely blow my mind.
I wonder if there's a form of cognitive bias where an unknown is treated as an absence rather than unknown, or rather a local known is extrapolated into a global one. We have fairly high confidence that there's not other intelligent life in our solar system. Not much is known beyond that. One extrapolation is that the universe is more of that. The other is that we exist as evidence and that pattern repeats elsewhere.
A multiverse I can equally accept as not. What I would find far more incomprehensible is if we were to discover with certainty that we were the only intelligent life in the universe.
A multiverse I can equally accept as not. What I would find far more incomprehensible is if we were to discover with certainty that we were the only intelligent life in the universe.
An impressive achievement it is. But a general sentiment today seems to be that the process somehow has stalled or perhaps has slowed down dramatically - despite the fact that there are more scientists involved than ever before. Does this mean that we are at, or close to, the limit of what we can possibly know? Or even "guess," like in the case of M-theory (or other quantum gravity endeavors)? Some say that fundamental physics is essentially done, and the future progress lies with biology (which, one hopes, will lead to further advances in medicine, in particular).
Physics allows practical applications of mathematics, whether using sine/cosine to explain wave motion or complex calculation of celestial objects, like planetary orbits. Yet it still cannot explain quantum mechanics, i.e. interactions of subatomic particles because there the general laws of physics do not work.
So basically it just comes down to how much of physics knowledge that humanity has obtained up to now really explains the universe - and it seems there are still vasts gaps in science that still needs to be filled.
FYI quantum (field) theory is the best and the most accurate physical theory in existence today.
FWIW supersymmetry and string theory were never convincing to people who value science, empiricism, epistemology, etc. This sort of pseudo-scientific hype is necessary to keep the money flowing under capitalism. See also "artificial intelligence", etc.
https://arxiv.org/abs/0905.2658
https://arxiv.org/abs/0905.2658
What if the cause of the cosmological redshift is continuous photon decay? Not galactic recession, but photon hubbling, or tired light?
www.bigcircusmodel.org
www.bigcircusmodel.org
It’s intuitively a reach, because photons don’t move.
From a four dimensional perspective—which is the correct one, let’s not forget—the distance between a photon’s emission and absorption event is always zero.
“Tired light” would require the photon to spontaneously lose energy based on the Manhattan distance of the path it takes. That distance can be arbitrarily large, sure—a photon can cover the entire universe before absorption—but it isn’t the path the photon actually takes, so it’s difficult to imagine why it would matter.
From a four dimensional perspective—which is the correct one, let’s not forget—the distance between a photon’s emission and absorption event is always zero.
“Tired light” would require the photon to spontaneously lose energy based on the Manhattan distance of the path it takes. That distance can be arbitrarily large, sure—a photon can cover the entire universe before absorption—but it isn’t the path the photon actually takes, so it’s difficult to imagine why it would matter.
> From a four dimensional perspective—which is the correct one, let’s not forget—the distance between a photon’s emission and absorption event is always zero.
That would require the emission and absorption events location in the space to be the same would it not? Or do you mean that a photon does not experience time, so relative to the photon it simply travel instantaneously from emitting coordinate to absorption coordinate?
That would require the emission and absorption events location in the space to be the same would it not? Or do you mean that a photon does not experience time, so relative to the photon it simply travel instantaneously from emitting coordinate to absorption coordinate?
The distance metric for flat spacetime is given by:
ds^2 = dx^2 + dy^s + dz^2 - cdt^2
> That would require the emission and absorption events location in the space to be the same would it not?
I think they're referring to the distance in Minkowski space,[0] where the time component and space component cancel out for light.
[0]: https://en.m.wikipedia.org/wiki/Spacetime#Spacetime_interval
I think they're referring to the distance in Minkowski space,[0] where the time component and space component cancel out for light.
[0]: https://en.m.wikipedia.org/wiki/Spacetime#Spacetime_interval
Where does your claim that photons don't move come from? Very simply, the Sun is 8 minutes from the Earth. The photon is most definitely moving from the Sun to the Earth.
They are talking about "intervals" in 3+1 dimensional space time. To explain it rigorously, one needs to define a few terms like "metric" or "light cone". One defining property of the photon is that its space-time interval between any two events in its history is zero. You can think of it as the dual of the fact that a clock moving at the speed of light would be completely stopped.
Intervals are the square of the distance, so not quite, but… yes.
There’s a tendency to treat spacetime intervals as something abstract and possibly metaphysical, because we can’t see or touch them, and they work counterintuitively.
They’re actually the opposite. Our normal experience of 3D space is what is unphysical; the (square root of the) spacetime interval is simply distance, measured in meters. Or seconds, of course.
The literal, physical distance between an absorption and emission event is always zero. Reality is non-Euclidean. The Manhattan distance is larger than the actual distance, which is usually true anyway.
Well, I suspect I just spent a lot of words telling you something you already knew, so I’ll leave off with a book recommendation. Dichronauts, by Greg Egan.
Between that and the Clockwork Rocket trilogy, I don’t know a better way to inculcate an intuition for special relativity.
One is set in a 2+2 spacetime; the other in 4+0. The differences are instructive.
There’s a tendency to treat spacetime intervals as something abstract and possibly metaphysical, because we can’t see or touch them, and they work counterintuitively.
They’re actually the opposite. Our normal experience of 3D space is what is unphysical; the (square root of the) spacetime interval is simply distance, measured in meters. Or seconds, of course.
The literal, physical distance between an absorption and emission event is always zero. Reality is non-Euclidean. The Manhattan distance is larger than the actual distance, which is usually true anyway.
Well, I suspect I just spent a lot of words telling you something you already knew, so I’ll leave off with a book recommendation. Dichronauts, by Greg Egan.
Between that and the Clockwork Rocket trilogy, I don’t know a better way to inculcate an intuition for special relativity.
One is set in a 2+2 spacetime; the other in 4+0. The differences are instructive.
This made me laugh given that, actually, Greg Egan is by far my favorite author. But I also think you are going way too far by saying that our normal 3D space is what is unphysical. The fact that our everyday reality is the limit of a more interesting reality when some parameter becomes small, does not make it any less real, for any reasonable definition of "real".
Well, it's certainly consistent. And for the most part you're right; it's just light that gets hard to understand from this perspective.
Unfortunately photon behaviour is fairly important...
Unfortunately photon behaviour is fairly important...
Briefly, from special relativity. As something approaches the speed of light, time slows down for it. At the speed of light (through vacuum) time stops, and in that reference frame there is no such thing as distance.
Thoughts on gravitational lensing point above? From the photon's point of view, it is experiencing changes through time and space.
That point misses (or rather ignores) the larger point. Ignoring special relativity because you think Einstein was "lost in the notation" is an extraordinary claim for which no extraordinary proof exists.
Never said that. I'm solid on speed of light as a max, gravitational lensing, gravitational redshift, and all the real world measurements that are in total sync with relativity.
The point is that I think claims like "distance doesn't exist" is the kind of thinking that comes from people lost in notation.
The point is that I think claims like "distance doesn't exist" is the kind of thinking that comes from people lost in notation.
It's 8 minutes for an "external" observer. Physicists say the photon itself does not experience time or space.
The photon does experience change over time and space. Take gravitational lensing by the Sun. The photons that we see from behind the Sun, are definitely affected by the Sun. From the photon's point of view, it is experiencing changes through time and space. Thoughts?
Not from the photon's point of view. It is emitted and absorbed immediately. The distance traveled (in 4d spacetime) of a photon is always 0, no matter (pun intended) what's in between or what you observe.
I don't think it is true to say that "it is emitted and absorbed immediately", because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter.
I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.
I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.
>because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter.
Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless.
Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled
Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless.
Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled
"Sun->Earth or Sun->Jupiter is a small beer"? How do you mean? This is a real physical example with real physical consequences for example for how much dimmer the light is per area (by 1/r^2) and by how much redder it is (by 1/r).
What are the real physical consequences of thinking that the photon is "emitted and absorbed at the same instant"?
What are the real physical consequences of thinking that the photon is "emitted and absorbed at the same instant"?
I'm not smart enough to know if that makes any sense at all. But it's a very intriguing idea. I'd never heard of it before.
If it were the case, photon decay would be measurable.
https://physicsworld.com/a/what-is-the-lifetime-of-a-photon/
https://physicsworld.com/a/what-is-the-lifetime-of-a-photon/
E_measured / E_emitted = e^(-d / H'c)
e is 2.718... d is distance of travel H' is 13.83 billion years, the continuous decay rate
Rough calculations https://docs.google.com/spreadsheets/d/13aRdc1gZmsA3F-gKt5sK...
Data from https://ned.ipac.caltech.edu/Library/Distances/
e is 2.718... d is distance of travel H' is 13.83 billion years, the continuous decay rate
Rough calculations https://docs.google.com/spreadsheets/d/13aRdc1gZmsA3F-gKt5sK...
Data from https://ned.ipac.caltech.edu/Library/Distances/
This idea has been around almost a hundred year. It is not supported by the evidence.
https://en.wikipedia.org/wiki/Tired_light
https://en.wikipedia.org/wiki/Tired_light
What if I could rebut all the rebuttals?
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
Sorry for meta, but to downvoters: please don't downvote a what-if question that - well, questions an established theory in a casual conversation. A lot of interesting, disruptive things in science start with a question!
Thank you
Without taking a position on downvoting - this is true for new interesting questions, at some point you have to move past ones already eliminated as reasonable possibilities.
OTOH, I think this position is relevant only from the perspective of new scientific inquiry — it’s worth asking questions that have already be asked when learning / acquiring knowledge! Sure, someone could find this information on Google, but misinformation too, so I think it’s worth asking in this sort of environment so we can all more deeply understand existing theory, etc.
[deleted]
This seems very much like a disingenuous what-if - not a desire to actually seek an answer, but an attempt to convince people into believing what they do by posting a link to a very biased site.
While the comment says "What if", the site linked is more "All physics is wrong, this is how it is" and presents some model that has been disproven by evidence over and over. I think crank physics isn't worth discussing when presented in that fashion.
Not supported by data. There is plenty observational evidence that the redshift is due to cosmic expansion, e.g. galaxy surface brightness evolution, CMB, time dilation, the list goes on.
The website you link poses a number of unsubstantiated claims without any answer to the numerous problems it raises.
Then he links to this hilarious notebook; https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
I don't mean to sound rude but this doesn't look like the work of someone who has spend any considerable amount of time actually studying the Universe.
The website you link poses a number of unsubstantiated claims without any answer to the numerous problems it raises.
Then he links to this hilarious notebook; https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...
I don't mean to sound rude but this doesn't look like the work of someone who has spend any considerable amount of time actually studying the Universe.
What if I could rebut all the rebuttals?
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
And, what's your view on Dirac's large numbers hypothesis?
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
And, what's your view on Dirac's large numbers hypothesis?
This would not give blackbody radiation, and is ruled out by observation.
http://www.astro.ucla.edu/~wright/tiredlit.htm
http://www.astro.ucla.edu/~wright/tiredlit.htm
What if I could rebut all the rebuttals?
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.
- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...
- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.
Please don’t repeat the same comment over and over, it comes off as spam even though that’s not what you intended.
This doesn’t even address this particular parent’s question. Better would be to make the comment once, where it is most appropriate, then give specific responses to other threads, perhaps linking to the one comment if it’s relevant.
This doesn’t even address this particular parent’s question. Better would be to make the comment once, where it is most appropriate, then give specific responses to other threads, perhaps linking to the one comment if it’s relevant.
The supernova light curve data is red shift vs. timescale of the light curve. This doesn't make any assumption about galactic recession. And it's incompatible with tired light models.
No, the CMBR is not consistent with non-expansionary models. Tired light may get the shape of the CMBR spectrum right, but it fails to get the intensity right unless there's an extreme coincidence that we just happen to be living at exactly the right moment.
This was all explained in the page you think you were rebutting, so please go re-read it, this time for comprehension.
No, the CMBR is not consistent with non-expansionary models. Tired light may get the shape of the CMBR spectrum right, but it fails to get the intensity right unless there's an extreme coincidence that we just happen to be living at exactly the right moment.
This was all explained in the page you think you were rebutting, so please go re-read it, this time for comprehension.
I await your commentary on the SALT2 calibration mechanism. This is the point where bias is introduced. The supernovae light curve data was biased before any analysis made.
This doesn't appear anywhere in the link from the link I provided for the SN light curves.
https://arxiv.org/abs/astro-ph/0104382
https://arxiv.org/abs/astro-ph/0104382
Thanks for linking. So this paper is from 2001. Whereas SALT2 is from 2007. https://www.aanda.org/articles/aa/pdf/2007/16/aa6930-06.pdf
This 2001 paper uses a correction template that I think is a v1 of what SALT2 is. SALT2 probably is an "improvement" on this template, so I think by identifying a problem in SALT2, I have adequate (but not 100%) reason to think this template introduces the same bias.
This 2001 paper uses a correction template that I think is a v1 of what SALT2 is. SALT2 probably is an "improvement" on this template, so I think by identifying a problem in SALT2, I have adequate (but not 100%) reason to think this template introduces the same bias.
The current work on SN cosmology is making subtle measurements to try to determine difficult to measure properties of the expansion of the universe, using SN at high red shift.
Tired light is easily killed without all that, using data available decades ago, at z < 1. And this doesn't require estimation of the absolute luminosity of the SN.
Tired light is easily killed without all that, using data available decades ago, at z < 1. And this doesn't require estimation of the absolute luminosity of the SN.
Why are you bringing up something else? Awaiting your commentary on the big 3 rebuttals of tired light, and the rebuttals of those rebuttals.
It's you bringing up something else. SALT2 is a red-herring.
Now that's false.
The point is that the data calibration mechanism introduces bias before any analysis has been made. The data is calibrated to assume galactic recession. That's the problem.
The point is that the data calibration mechanism introduces bias before any analysis has been made. The data is calibrated to assume galactic recession. That's the problem.
The point of SALT2 was better models for calculating the brightness of SN, so their distance could be calculated. This is necessary for detecting subtle changes in the expansion rate of the universe.
Killing tired light doesn't require any of this. What the paper I cited did was plot the redshift vs. the rise and fall times of the light curves. This doesn't depend at all on the overall brightness of the SN. There is no need to estimate this brightness. In tired light, the result curve will be flat; in the standard cosmology it will not be. And the observations were inconsistent with tired light at 10 standard deviations, killing the theory. The SALT2 stuff you're pointing to is indeed a total red herring.
I get the feeling you're just pretending to understand all this stuff you're pointing to, for some reason.
Killing tired light doesn't require any of this. What the paper I cited did was plot the redshift vs. the rise and fall times of the light curves. This doesn't depend at all on the overall brightness of the SN. There is no need to estimate this brightness. In tired light, the result curve will be flat; in the standard cosmology it will not be. And the observations were inconsistent with tired light at 10 standard deviations, killing the theory. The SALT2 stuff you're pointing to is indeed a total red herring.
I get the feeling you're just pretending to understand all this stuff you're pointing to, for some reason.
Reminds me of Cyclic Conformal Cosmology theory (backed by Roger Penrose).
As far as I can tell, the CCC theory says that the big bang did happen but that the universe is cyclical. i.e. once the universe reaches 'heat death' another big bang happens.
As far as I can tell, the CCC theory says that the big bang did happen but that the universe is cyclical. i.e. once the universe reaches 'heat death' another big bang happens.
Penrose's observations of evaporated black holes in the cosmic background radiation map are really interesting. This is a big reason to think there are structures older than 13.8 billion years.
I'm not smart enough to understand most of cosmology or astrophysics, but the way that site is presented makes me feel that it is quackery. The fact that there are only a handful of sentences makes me feel it is trying to appeal to people with low science literacy.
I'm not trying to discount it, but that home page with 12 photos of various galaxies, and then 4 blurbs of text, then a full screen YouTube video just feels "unscientific".
I'm not trying to discount it, but that home page with 12 photos of various galaxies, and then 4 blurbs of text, then a full screen YouTube video just feels "unscientific".
I find this a bit funny as we just can't know what we don't know.
But we have pretty tight bounds on how much the things we don't know can influence the things we do know, because we have tons of observations. We are for example quite sure that there is nothing on Earth that makes apples fall upwards and we can be reasonably certain that this is also true on other planets.
I don't think the bounds are tight or it can ever be. If you don't know something, you just don't know. We don't know much about negative mass or if gravitons exist yet, two things which could make apples fall upward. There's nothing that allows us to say with absolute certainty that it isn't possible, especially on planets billions of light years away that we have no visibility into at all.
We can't assign 0 probability to any position on the grounds of "humility", but "negative mass" assuming our best theories are true is probability-0.
The relevant probabilities when making predictions are under the best theoretical assumptions we can make; which includes that the universe follows the same laws of physics everywhere.
It isn't very interesting to observe that, absent these, no proposition has a zero probability.
Eg., you dont get to claim that given the laws of physics it is possible to have a negative mass, because given no laws of physics, it is possible.
When you arent given any information at all, all propositions are equally likely.
Propositions like, "the universe has a maximum speed" aren't merely observational. They follow with probability-1 from fundamental universal laws of physics. If this is false, all of physics is false.
The relevant probabilities when making predictions are under the best theoretical assumptions we can make; which includes that the universe follows the same laws of physics everywhere.
It isn't very interesting to observe that, absent these, no proposition has a zero probability.
Eg., you dont get to claim that given the laws of physics it is possible to have a negative mass, because given no laws of physics, it is possible.
When you arent given any information at all, all propositions are equally likely.
Propositions like, "the universe has a maximum speed" aren't merely observational. They follow with probability-1 from fundamental universal laws of physics. If this is false, all of physics is false.
(I realize we may in fact be saying the same thing, but I just want to express it in a different way.)
> assuming our best theories are true
Isn't that what the course of history teaches us, that our best theories usually aren't true? At one time spontaneous generation was our best theory on where frogs came from after it rained, and it was based upon our best observations at the time. I'm not sure why this particular point in time would be special. I'm not saying that the current laws of physics aren't a great way to model the universe as we currently observe it, but it doesn't mean they actually are true and we have to be open to that possibility, if something that doesn't fit our current models and laws appear. But not until then, mind you.
> assuming our best theories are true
Isn't that what the course of history teaches us, that our best theories usually aren't true? At one time spontaneous generation was our best theory on where frogs came from after it rained, and it was based upon our best observations at the time. I'm not sure why this particular point in time would be special. I'm not saying that the current laws of physics aren't a great way to model the universe as we currently observe it, but it doesn't mean they actually are true and we have to be open to that possibility, if something that doesn't fit our current models and laws appear. But not until then, mind you.
Yes, but I think we need to be clear here on what we mean by theory, and what information we're taking as a given.
The proposition, "steel bars in this lab fall to the earth" being /false/ doesn't impact essentially any theory of physics if there are magnets in the lab. If you exclude every possible alternative, leaving gravity, then the proposition being false invalidates basically all of physics. Including the fundamental assumption that the laws of the universe are universal.
So the question is what theories *require* a proposition to be true, in that, they logically entail it.
When this is made clear it should be obvious that "maybe the maximum speed of the universe is different" is very very different to the claim, "maybe mars is habitable".
Many lay people, entirely ignorant of the best theories we have, do not understand that the former requires extraordinary levels of evidence to take seriously; while the latter requires almost none.
This type of "unknown unknown" argument often fails to make this distinction for the sake of making some fantasy as plausible as some possible reality.
The proposition, "steel bars in this lab fall to the earth" being /false/ doesn't impact essentially any theory of physics if there are magnets in the lab. If you exclude every possible alternative, leaving gravity, then the proposition being false invalidates basically all of physics. Including the fundamental assumption that the laws of the universe are universal.
So the question is what theories *require* a proposition to be true, in that, they logically entail it.
When this is made clear it should be obvious that "maybe the maximum speed of the universe is different" is very very different to the claim, "maybe mars is habitable".
Many lay people, entirely ignorant of the best theories we have, do not understand that the former requires extraordinary levels of evidence to take seriously; while the latter requires almost none.
This type of "unknown unknown" argument often fails to make this distinction for the sake of making some fantasy as plausible as some possible reality.
Well, we actually sort of know that something is different far away, since the rotation profile of galaxies do not match theoretical predictions. There are currently two different resolutions, either postulating new particles (dark matter and energy) or change of fundamental laws (MOND theories). Since we didn't manage to detect either in our solar system we know that something is different.
In our planetary system, yes. Outside evidence gets worse.
Earth has a super weak magnetic field (that can change in the future). With a stronger field, apples could fall upwards, sideways or just suspend in the air. Can an apple tree even grow in such conditions is another question.
Only if the apple is vaccinated against COVID.
EDIT: Umm, it was a joke. I don’t claim it was funny. But...just a joke.
EDIT: Umm, it was a joke. I don’t claim it was funny. But...just a joke.
Water and graphite are strong diamagnetics that repel magnetic field. This is why that frog, or anything with high water or carbon content, levitates in a strong magnetic field. I'm sure the effect can be improved with a dynamic field (something like slow em radiation that would continuously bump the object up).
True. But possibly put it best by that great thinker Donald Rumsfeld: https://www.wikiwand.com/en/There_are_known_knowns
Thankfully as a result of the time dimension it is certainly possible to know what we don’t know…
“Fundamental” physics is just the physics of what we happen to be able to observe with the technology available to us at the moment. Newton was creating the fundamental physics of his time. And a century from now, even if in our generation we succeed in erecting a complete theory that explains everything we have ever seen, physicists will be working on “fundamental physics”. And we still won’t have a good enough handle on turbulence.
Isn't turbulence more a mathematical problem than a physical one?
Experiment is still the arbiter of truth; it enables us to discern which math correctly describes nature.
I don’t think it’s considered an interesting mathematical problem, although it is related to some interesting theorems about singularities in the fluid equations. It’s of interest to applied mathematicians, engineers, and, perennially, to physicists and artists. For example, Leonardo, who was all of these things.
Solving turbulence is quite literally a millenium prize problem with a 1 million USD price tag to it. Solving it would make you famous and almost certainly give you a Fields medal as well. It’s just a particularly difficult problem.
No, it isn’t “quite literally a millenium prize problem”. The problem definition is at https://www.claymath.org/sites/default/files/navierstokes.pd.... This is related to what I mentioned in passing when I referred to theorems about singularities. You could solve this problem and collect the million bucks and still not have “solved turbulence”. Of course, there is no universal agreement about what solving turbulence means, exactly.
EDIT: But most would agree that it would involve constructing solutions to the NS equations that describe turbulence. You could solve the millennium problem by proving that smooth solutions exist, but still not show how to construct any. So it would be of theoretical interest but do nothing to handle the problems of turbulence.
It may not exactly match the problem statement of that particular prize, but “solving turbulence” is most definitely a very interesting and important area of mathematics research.
What do you mean by “solving turbulence”, and how is it of interest to pure mathematicians?
Emergence of chaos in differential equations is pretty much one of the frontiers of pure mathematics
> Solving turbulence is quite literally a millenium prize problem with a 1 million USD price tag to it.
Meanwhile, the Apple CEO received $750 million. I think mathematicians are underpaid.
Meanwhile, the Apple CEO received $750 million. I think mathematicians are underpaid.
From the practical standpoint, I think it remains more of an engineering problem than anything else. (This is not "fundamental physics" for sure.)
You might want to read into quantum chaos:
the mathematical concept of chaos haunts physics on all levels, including 'fundamental' physics
What's the distinction?
I think language and especially writing are more extrordinary achievements. Physics is useful for engineering purposes in a civilization. Civilization would not exist without language.
I think ability to walk upright is a bigger achievement
We could build modern society strictly crawling, without language we would still be hunter gatherers in small packs.
Other species can walk upright, some of them achieved walking upright long before us…and yet they are no longer around.
I’m more impressed by the ability to metabolize oxygen. Nobody will ever beat that.
well creatures that can't walk upright are not human so bipedalism can not be counted as a human achievement. Anyway maybe you are right in a broad sense. My point was that extolling physics above all other human achievements seems lopsided to me. Physics is useful for engineering purposes. It is not some all encompassing philosophy or technology that covers all aspects of human interaction with the universe. writing is certainly used far more broadly than the schrodinger equation.
Unfortunately it comes at a high price. Who doesn't have backache?
Or opposable thumbs!
Humanity’s most extraordinary achievement is that we are still alive, despite having 8 or 9 countries with nuclear weapons
For now. Going to be much more difficult for this to continue when the average temperatures are 10° higher. And I can very well see a situation arise where nuclear weapons are used because of pressures from climate change, say between India and Pakistan.
I think we were able to survive the Cold War because the threat was literally explosive: highly visible and quickly understandable. For longer term, quieter threats like climate change humanity does not appear to have the capability to avoid its destruction, or even the will to do so.
I think we were able to survive the Cold War because the threat was literally explosive: highly visible and quickly understandable. For longer term, quieter threats like climate change humanity does not appear to have the capability to avoid its destruction, or even the will to do so.
I mean it's an achievement, for sure. Understanding what the universe is made of is pretty massive.
But is it the most extraordinary one?
I think more towards how we have escaped our constraints as animals:
- It's a problem to eat too much now, contrary to the experience of all creatures other than modern people.
- We no longer live in one environment. In fact we create our own, in many places.
- We don't mind if the sun goes down, we can replace it, temporarily.
- We can use energy that was captured a long long time ago.
- We don't even need to reproduce all that much to survive. It's pretty much an expectation that we'll live past childhood, it's considered a massively unfortunate tragedy if your kid dies these days.
- We can interact with people who are far away, as if they are right in front of us.
But is it the most extraordinary one?
I think more towards how we have escaped our constraints as animals:
- It's a problem to eat too much now, contrary to the experience of all creatures other than modern people.
- We no longer live in one environment. In fact we create our own, in many places.
- We don't mind if the sun goes down, we can replace it, temporarily.
- We can use energy that was captured a long long time ago.
- We don't even need to reproduce all that much to survive. It's pretty much an expectation that we'll live past childhood, it's considered a massively unfortunate tragedy if your kid dies these days.
- We can interact with people who are far away, as if they are right in front of us.
Interestingly enough most of these are also possible because of advancements in physics.
But our advancements in physics are also only possible because of these things.
This is the classier form of the "who would win in a fight between Thanos and Darkseid" internet discussions. But yes, physics is amazing, but it doesn't exist alone. Math is particularly important, but also chemistry and engineering all co-exist in a positive feedback loop.
(If I had to isolate the single greatest insight in the modern world, it would be Descartes introducing the notion of number as different than "the length of a line segment". This change in perspective made possible all the math and physics that came after. This perspective is now so common as to be invisible, so for someone to see something so foundational, but so unknown, it is really remarkable.)
(If I had to isolate the single greatest insight in the modern world, it would be Descartes introducing the notion of number as different than "the length of a line segment". This change in perspective made possible all the math and physics that came after. This perspective is now so common as to be invisible, so for someone to see something so foundational, but so unknown, it is really remarkable.)
Could you elaborate on what Descartes did? He's known as the inventor of coordinate geometry, which seems to rely on the notion of number as the length of a line segment (two number lines placed perpendicular to one another uniquely identify any point on the plane). Are you talking about his work on algebra or other things?
https://en.wikipedia.org/wiki/Ren%C3%A9_Descartes#Mathematic...
I will look up the specific paper where he proposed that a squared number need not represent only an area, for example.
I will look up the specific paper where he proposed that a squared number need not represent only an area, for example.
Ah, I get it now. Descartes suggested that the representation of numbers need not be dictated by the geometric interpretation of how they were calculated. For example, a^2 doesn't have to be represented as an area, even though geometrically it would be the area of a square.
The "paper" was La Géométrie[1], originally published as an appendix(!) to another work, Discourses on the Method [2].
Not sure why all the downvotes. Oh well.
1 - https://en.wikipedia.org/wiki/La_G%C3%A9om%C3%A9trie
2 - https://en.wikipedia.org/wiki/Discourse_on_the_Method
Not sure why all the downvotes. Oh well.
1 - https://en.wikipedia.org/wiki/La_G%C3%A9om%C3%A9trie
2 - https://en.wikipedia.org/wiki/Discourse_on_the_Method
I'm truly humbled to be alive at a time when so many of the biggest questions that frustrated our ancestors have more or less accurate answers. We know about the big bang, the atom, black holes, the speed and nature of light--how majestic and beautiful it all is. Thank you to all the physicists that got us here, and godspeed to the physicists of the future!
That's a very euro-centric view to sat that "humanity’s most extraordinary achievement" is something that has been developed/found out/whatever you want to call it mostly in the parts of the world inhabited by white men.
Like someone else mentions in this thread, probably "humanity’s most extraordinary achievement" was standing upright in the Ethiopian plains, or language or even writing (which showed up in several parts of the world) but, again, to label a thing invented by white men (paid to develop deadly weapons, among other bad things) as the "humanity's greatest thing ever" should not be ok.
Like someone else mentions in this thread, probably "humanity’s most extraordinary achievement" was standing upright in the Ethiopian plains, or language or even writing (which showed up in several parts of the world) but, again, to label a thing invented by white men (paid to develop deadly weapons, among other bad things) as the "humanity's greatest thing ever" should not be ok.
It's not generally accurate that the developments which ultimately led to modern physics are exclusively European. Certainly the post-Renaissance work was primarily performed by Europeans, because the Ottomans shut down their observatories [1] and the Qing Dynasty banned "foreign" mathematics [2]. Europe's major competitors had simply forfeited the race. Even so, the Japanese physicist Tomonaga shared the Nobel Prize for the development of QFT [5].
Prior to that, European advancements were heavily influenced by Islamic and Indian mathematics, such as the development of place-value numerals [3] and modern optics [4]
1: https://en.wikipedia.org/wiki/Constantinople_observatory_of_...
2: https://en.wikipedia.org/wiki/Chinese_mathematics#Qing_dynas...
3: https://en.wikipedia.org/wiki/Hindu%E2%80%93Arabic_numeral_s...
4: https://en.wikipedia.org/wiki/Physics_in_the_medieval_Islami...
5: https://en.wikipedia.org/wiki/Shin%27ichir%C5%8D_Tomonaga
Prior to that, European advancements were heavily influenced by Islamic and Indian mathematics, such as the development of place-value numerals [3] and modern optics [4]
1: https://en.wikipedia.org/wiki/Constantinople_observatory_of_...
2: https://en.wikipedia.org/wiki/Chinese_mathematics#Qing_dynas...
3: https://en.wikipedia.org/wiki/Hindu%E2%80%93Arabic_numeral_s...
4: https://en.wikipedia.org/wiki/Physics_in_the_medieval_Islami...
5: https://en.wikipedia.org/wiki/Shin%27ichir%C5%8D_Tomonaga
As a mixed man (half North African, half Western European) this comes across as needlessly antagonistic. There’s nothing in the article to indicate that this was picked due to the race of these inventors nor is there any immediately clear indication of unconscious racism.
I know I’m probably biting at obvious flame bait here but this comment doesn’t really seem to be in the spirit of this site’s goals for quality discourse.
I know I’m probably biting at obvious flame bait here but this comment doesn’t really seem to be in the spirit of this site’s goals for quality discourse.
> There’s nothing in the article to indicate that this was picked due to the race
That's the worst type of racism, the one so well internalised that you don't realise is there, that's what makes it more dangerous compared to the "redneck"-out-in-your-face variety.
I'm pretty sure that the author of article wasn't aware of his/her implicit euro-centric bias, he/she comes from a culture where things like "fundamental physics" are seen as representative of the group's intellectual nous (where the "group" ~= people raised up/educated in an euro-centric culture with euro-centric values), and hence as representative of the world/humanity as a whole. I take issue with this "the bestest thing made by white men" -> "the bestest thing made by humanity" transition.
That's the worst type of racism, the one so well internalised that you don't realise is there, that's what makes it more dangerous compared to the "redneck"-out-in-your-face variety.
I'm pretty sure that the author of article wasn't aware of his/her implicit euro-centric bias, he/she comes from a culture where things like "fundamental physics" are seen as representative of the group's intellectual nous (where the "group" ~= people raised up/educated in an euro-centric culture with euro-centric values), and hence as representative of the world/humanity as a whole. I take issue with this "the bestest thing made by white men" -> "the bestest thing made by humanity" transition.
White men are not the only folks involved in researching fundamental physics and you know it. You comment devalues their work more than anything on this page.
Your account is old enough I’d expect you to know what dang’s about to say already, the whole “we’re steering a ship and don’t want to get sucked into dialectic black holes” thing.
Your account is old enough I’d expect you to know what dang’s about to say already, the whole “we’re steering a ship and don’t want to get sucked into dialectic black holes” thing.
Implying science is a European thing is anachronistic, and a direct insult and discouragement its many diverse contributors. Here's a map of contributing countries from the last experiment I worked on: https://cds.cern.ch/record/2654110/files/ATLAS-Map-July2021-..., there is also a diversity & inclusion statement: https://atlas.cern/diversity
A view of the universe from Flatland.
I don't think any of the physics we know is truly fundamental.
"Fundamental" is a direction of research in physics.
Why do you think that? (I happen to agree)
Well, unless the most fundamental laws of physics were intelligently designed (which I doubt and which would lead to a recursive argument anyway) they must be the simplest that can lead to intelligent creatures arising. Current physical laws are too complex to be the simplest possible such laws.
"If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied." --Richard Feynman
What's interesting is that the Ancient Greeks "knew" this but it took two thousand years to actually prove it. Now the question is: how long can it take to confirm one of the quantum gravity theories? (Quantum gravity remains the biggest unsolved problem in fundamental physics today.)
This is survivorship bias. They 'knew' it only retrospectively, they also 'knew' a lot of different incorrect theories. In some sense one could argue that Aristotle halted the progress of physics for about a thousand years (not related to atoms, but a general comment of what the Ancient Greek 'knew')
If the progress in physics really was halted for a millennium (actual physics was not moving that fast beforehand), any blame must rest with the intellectuals of that time.
I fully agree, I'm not blaming him.
It is interesting though that maths was taught for a 1000 years from Euclid's Elements, Euclid living approximately at the same time as Aristotle, and it is still as valid today as it was 2000 years ago but physics was taught from Aristotle's teaching and it was just bonkers. Took 1000 years for someone to finally say 'wait, something's not right'
It is interesting though that maths was taught for a 1000 years from Euclid's Elements, Euclid living approximately at the same time as Aristotle, and it is still as valid today as it was 2000 years ago but physics was taught from Aristotle's teaching and it was just bonkers. Took 1000 years for someone to finally say 'wait, something's not right'
You are right to put "knew" in quotes, as Democritus' speculation had no more support than Thales' "all is water", the four elements, the bodily humors or the celestial spheres. Knowledge lies at least as much in the justification of a fact as it does in the proposition itself.
I dust myself off and carry on as best I can, hoping to learn a little more than I did the day before, knowing there are good folks by my side to share the path we’re on.