space-time, mass-energy, gravity-information?
June 30, 2019 1:49 AM Subscribe
The Simple Idea Behind Einstein's Greatest Discoveries - "Lurking behind Einstein's theory of gravity and our modern understanding of particle physics is the deceptively simple idea of symmetry. But physicists are beginning to question whether focusing on symmetry is still as productive as it once was."
What Does It Mean That Quantum Gravity Has No Symmetry? - "GR and QFT individually are both insufficient. We need something more: an understanding of gravity at the quantum level."[1]
Optimal quantum computation linked to gravity - "Information and gravity may seem like completely different things, but one thing they have in common is that they can both be described in the framework of geometry. Building on this connection, a new paper suggests that the rules for optimal quantum computation are set by gravity."[2]
How to Understand the Universe When You're Stuck Inside of It - "Lee Smolin has a radical idea for how to understand an object with no exterior: Imagine it built bit-by-bit from relationships between events."
What Does It Mean That Quantum Gravity Has No Symmetry? - "GR and QFT individually are both insufficient. We need something more: an understanding of gravity at the quantum level."[1]
Optimal quantum computation linked to gravity - "Information and gravity may seem like completely different things, but one thing they have in common is that they can both be described in the framework of geometry. Building on this connection, a new paper suggests that the rules for optimal quantum computation are set by gravity."[2]
How to Understand the Universe When You're Stuck Inside of It - "Lee Smolin has a radical idea for how to understand an object with no exterior: Imagine it built bit-by-bit from relationships between events."
E=EndivesSquash
posted by pracowity at 6:13 AM on June 30, 2019 [20 favorites]
posted by pracowity at 6:13 AM on June 30, 2019 [20 favorites]
But physicists are beginning to question whether focusing on symmetry is still as productive as it once was
Didn’t that husband/wife team out of CalTech recently win a Nobel for this?
posted by doctor tough love at 7:01 AM on June 30, 2019 [2 favorites]
Didn’t that husband/wife team out of CalTech recently win a Nobel for this?
posted by doctor tough love at 7:01 AM on June 30, 2019 [2 favorites]
It is sort of half-ass tangentially true, in that the energy is stored in chemical potential energies...
You were right the first time. The binding energies themselves contribute (trivially) to the overall mass.
posted by sjswitzer at 7:27 AM on June 30, 2019 [11 favorites]
You were right the first time. The binding energies themselves contribute (trivially) to the overall mass.
posted by sjswitzer at 7:27 AM on June 30, 2019 [11 favorites]
Solar energy arrives on Earth and becomes mass in the form of green leaves [...]
The author describes the sun turning mass into energy – and I think was straining to find a symmetrical example of the sun's energy turning into matter (I don't think it was a good example).
The first example I can recall learning of energy turning into matter was the creation of electron-positron pairs from cosmic rays and in particle accelerators – it doesn't lend itself to a 'common world experience' metaphor.
posted by rochrobbb at 7:31 AM on June 30, 2019 [1 favorite]
The author describes the sun turning mass into energy – and I think was straining to find a symmetrical example of the sun's energy turning into matter (I don't think it was a good example).
The first example I can recall learning of energy turning into matter was the creation of electron-positron pairs from cosmic rays and in particle accelerators – it doesn't lend itself to a 'common world experience' metaphor.
posted by rochrobbb at 7:31 AM on June 30, 2019 [1 favorite]
Another Wikipedia title is mass defect which says:
posted by XMLicious at 7:38 AM on June 30, 2019If a combination of particles contains extra energy—for instance, in a molecule of the explosive TNT—weighing it reveals some extra mass, compared to its end products after an explosion. (The weighing must be done after the products have been stopped and cooled, however, as the extra mass must escape from the system as heat before its loss can be noticed, in theory.) On the other hand, if one must inject energy to separate a system of particles into its components, then the initial mass is less than that of the components after they are separated. In the latter case, the energy injected is "stored" as potential energy, which shows as the increased mass of the components that store it. This is an example of the fact that energy of all types is seen in systems as mass, since mass and energy are equivalent, and each is a "property" of the other.
re: chlorophyll
quantum biology![3]
(also btw ;)
posted by kliuless at 7:52 AM on June 30, 2019 [1 favorite]
quantum biology![3]
(also btw ;)
posted by kliuless at 7:52 AM on June 30, 2019 [1 favorite]
I should say I read the article and found it interesting and well written overall – it was enough beyond what I know that if it went off the rails again I couldn't tell. I'd assume the author knew what they were talking about (or read and spoke to people who knew what they were talking about).
posted by rochrobbb at 8:04 AM on June 30, 2019 [2 favorites]
posted by rochrobbb at 8:04 AM on June 30, 2019 [2 favorites]
Meanwhile, from the fourth link
How to Understand the Universe When You're Stuck Inside of It
From the very first text after the headline:
Lee Smolin has a radical idea for how to understand an object with no exterior: Imagine it built bit-by-bit from relationships between events.
This has already helped my Sunday morning brain. And then a little later:
“Perimeter,” in fact, is the perfect word to describe Smolin’s place near the boundary of mainstream physics. When most physicists dived headfirst into string theory, Smolin played a key role in working out the competing theory of loop quantum gravity. When most physicists said that the laws of physics are immutable, he said they evolve according to a kind of cosmic Darwinism. When most physicists said that time is an illusion, Smolin insisted that it’s real.
This Amanda Gefter knows how to science write ...
posted by philip-random at 8:12 AM on June 30, 2019 [1 favorite]
How to Understand the Universe When You're Stuck Inside of It
From the very first text after the headline:
Lee Smolin has a radical idea for how to understand an object with no exterior: Imagine it built bit-by-bit from relationships between events.
This has already helped my Sunday morning brain. And then a little later:
“Perimeter,” in fact, is the perfect word to describe Smolin’s place near the boundary of mainstream physics. When most physicists dived headfirst into string theory, Smolin played a key role in working out the competing theory of loop quantum gravity. When most physicists said that the laws of physics are immutable, he said they evolve according to a kind of cosmic Darwinism. When most physicists said that time is an illusion, Smolin insisted that it’s real.
This Amanda Gefter knows how to science write ...
posted by philip-random at 8:12 AM on June 30, 2019 [1 favorite]
I gave the first article a chance, but it does not get less wishy washy:
Specifically, Einstein was puzzled by a difference that didn’t make a difference, a symmetry that didn’t make sense. It’s still astonishing to drop a wad of crumped paper and a set of heavy keys side by side to see that somehow, almost magically, they hit the ground simultaneously — as Galileo demonstrated (at least apocryphally) by dropping light and heavy balls off the tower in Pisa. If the force of gravity depends on mass, then the more massive an object is, the faster it should sensibly fall. Inexplicably, it does not.
Newton was puzzled too!
posted by haemanu at 8:17 AM on June 30, 2019
Specifically, Einstein was puzzled by a difference that didn’t make a difference, a symmetry that didn’t make sense. It’s still astonishing to drop a wad of crumped paper and a set of heavy keys side by side to see that somehow, almost magically, they hit the ground simultaneously — as Galileo demonstrated (at least apocryphally) by dropping light and heavy balls off the tower in Pisa. If the force of gravity depends on mass, then the more massive an object is, the faster it should sensibly fall. Inexplicably, it does not.
Newton was puzzled too!
posted by haemanu at 8:17 AM on June 30, 2019
But further thinking about it, I guess the biggest issue is that since no isotopes are changing in the Calvin Cycle, it is completely inappropriate to equate the stored energy as a change in mass. That doesn't happen without nuclear combination or decay and the addition/subtraction of protons/neutrons.Hmm. I'd argue that if you weighed - or used an inertial mass measurement on - a leaf that had a significant amount of stored chemical energy compared to an identical one that did not, you'd get a larger number. Calling it mass is kind of weird, but it's not actually wrong. Put a box around it, and it's mass.
But, I'm picking nits. . .and I agree with you and others about how convincing the article is. I made it all the way to the speed of light discussion before giving up in frustration.
posted by eotvos at 8:56 AM on June 30, 2019 [1 favorite]
The energy of a photon of red light is around 2 eV, so a photon of light absorbed in the most common form of photosynthesis must be in the neighborhood of 3 eV, whereas the rest mass of neutrinos is thought by many to be less than 0.3 eV.
So the mass of a molecule of chlorophyll increases by at least ten neutrinos' worth when it absorbs a photon.
posted by jamjam at 9:53 AM on June 30, 2019 [3 favorites]
So the mass of a molecule of chlorophyll increases by at least ten neutrinos' worth when it absorbs a photon.
posted by jamjam at 9:53 AM on June 30, 2019 [3 favorites]
I think the theoretical explanation is that a leaf is being defined as a closed system, and light entering (or exiting) a closed system changes (i.e., requires that) the rest mass of the system.
posted by polymodus at 10:49 AM on June 30, 2019 [2 favorites]
posted by polymodus at 10:49 AM on June 30, 2019 [2 favorites]
I just noticed that the journalist's justification for that line in the article is to cite Feynman's comment about potatoes. But Feynman there is claiming that potatoes become conscious which is really to say that matter is transformed into energy. And the reverse is true with photosynthesis which is what justifies the author's claim. So either both Feynman and the author are true/correct in some sense (having to do with physical symmetry and invariance), or both are wrong in some sense.
posted by polymodus at 11:29 AM on June 30, 2019 [1 favorite]
posted by polymodus at 11:29 AM on June 30, 2019 [1 favorite]
I'm not a scientist or nuthin' but I think this may not be metaphorical... in a college physics class it was specifically stated to me that E=mc² really genuinely means that the energy of chemical bonds measurably alters the mass of the molecules they're part of. So if this is a misapprehension it appears to be one shared by at least some physics professors with the OP reporter.
posted by XMLicious at 1:53 PM on June 30, 2019 [1 favorite]
posted by XMLicious at 1:53 PM on June 30, 2019 [1 favorite]
The equivalence of gravitational and inertial mass is pretty easy to see from a simple thought experiment; it's odd that nobody thought of it for so long:
Drop two equal sized bricks next to each other and time how long it takes them to fall. Now glue the two bricks together (or tie a string between them) and drop them. Why would they drop at a different rate?
Skipping ahead to the third article, there's something I like about the holographic and computational models. I've always been troubled by the many-body problem and that every particle needs to be in communication with every other particle in the universe in order to know what to do. That just seems, um, unphysical. Exchange particles, albeit virtual, go some way to soothe my unease, but then entanglement rears its head and ups my unease. So there must be something, I feel, like the Shell Theorem that reduces the complexity of quotidian interactions to something "computationally tractable." It seems like the computational and holographic universe ideas may be a step in this direction. (But what do I know?)
posted by sjswitzer at 2:05 PM on June 30, 2019 [1 favorite]
Drop two equal sized bricks next to each other and time how long it takes them to fall. Now glue the two bricks together (or tie a string between them) and drop them. Why would they drop at a different rate?
Skipping ahead to the third article, there's something I like about the holographic and computational models. I've always been troubled by the many-body problem and that every particle needs to be in communication with every other particle in the universe in order to know what to do. That just seems, um, unphysical. Exchange particles, albeit virtual, go some way to soothe my unease, but then entanglement rears its head and ups my unease. So there must be something, I feel, like the Shell Theorem that reduces the complexity of quotidian interactions to something "computationally tractable." It seems like the computational and holographic universe ideas may be a step in this direction. (But what do I know?)
posted by sjswitzer at 2:05 PM on June 30, 2019 [1 favorite]
I would say instead that 'the (rough) equivalence of gravitational and inertial mass is pretty easy to see from a simple thought experiment', because if you drop two bricks at the same time, whether or not they're glued together, the Earth will rise faster to meet them than it will for one dropped brick, and as a result, not only will the elapsed time before impact be shorter, the velocity of the two bricks will be greater at every moment in the time of the two brick fall because the closer Earth will exert more force on the two bricks as a consequence of the inverse square law.
But rough equivalence is not quite the same as equivalence.
posted by jamjam at 2:34 PM on June 30, 2019
But rough equivalence is not quite the same as equivalence.
posted by jamjam at 2:34 PM on June 30, 2019
I've come to suspect that the trouble with quantizing gravity is that it is in fact a fictitious force. An effect, not a cause. No force means no field, no particle, and nothing to be quantized.
Basically, gravitational acceleration may be no more real than the centripetal force that you feel when turning a corner in your car. You feel it, but not as it actually is.
Don't think too much about it though, or all of space may appear to suddenly implode into a single point. ;)
posted by wierdo at 2:50 PM on June 30, 2019 [1 favorite]
Basically, gravitational acceleration may be no more real than the centripetal force that you feel when turning a corner in your car. You feel it, but not as it actually is.
Don't think too much about it though, or all of space may appear to suddenly implode into a single point. ;)
posted by wierdo at 2:50 PM on June 30, 2019 [1 favorite]
I should have said: 'the velocity of the two bricks will be greater at every moment in in the time of the two brick fall because the closer Earth will exert more force on [each of] the two bricks as a consequence of the inverse square law.'
posted by jamjam at 2:51 PM on June 30, 2019
posted by jamjam at 2:51 PM on June 30, 2019
(But both bricks fell each time; it was only the glue or string that was different.)
posted by sjswitzer at 3:46 PM on June 30, 2019
posted by sjswitzer at 3:46 PM on June 30, 2019
I thought you were using the string/no string argument to demonstrate that heavy objects can't fall faster than lighter by arguing that if it were the case that heavy objects do fall faster than lighter ones then tying or gluing the two bricks together would make them into a heavier object and therefore they should fall faster than when they aren't tied, which is obviously not true.
Did I miss the point?
posted by jamjam at 8:36 PM on June 30, 2019
Did I miss the point?
posted by jamjam at 8:36 PM on June 30, 2019
Saying solar radiation becomes mass in the "form of green leaves" is really bad, like Swift's Laputas trying to convert cucumbers to sunlight bad. The mass in the leaf comes from things are not sunlight; the energy mostly goes to biosynthesis which is a horrible set of "wasteful" steps, thermodynamically.
I think the theoretical explanation is that a leaf is being defined as a closed system, and light entering (or exiting) a closed system changes (i.e., requires that) the rest mass of the system.
The problem is that a leaf is not a closed system, and you can't really make it approximate one "theoretically." One of the major products, oxygen, gets vented to the atmosphere. And that takes not just the raw mass of the O2 but also the energy it took to rip the atoms off the water.
It's kind of cool how much effort people are putting into saving the claim but the kindest interpretation is that it's a flowery turn of phrase, and the author liked the conceit enough to be indifferent to the fact that it lacked any scientific accuracy.
posted by mark k at 9:38 PM on June 30, 2019 [3 favorites]
I think the theoretical explanation is that a leaf is being defined as a closed system, and light entering (or exiting) a closed system changes (i.e., requires that) the rest mass of the system.
The problem is that a leaf is not a closed system, and you can't really make it approximate one "theoretically." One of the major products, oxygen, gets vented to the atmosphere. And that takes not just the raw mass of the O2 but also the energy it took to rip the atoms off the water.
It's kind of cool how much effort people are putting into saving the claim but the kindest interpretation is that it's a flowery turn of phrase, and the author liked the conceit enough to be indifferent to the fact that it lacked any scientific accuracy.
posted by mark k at 9:38 PM on June 30, 2019 [3 favorites]
"A tiny fraction of solar energy becomes mass in the form of a change of potential energy in the chemical bonds between the atoms that make up the plant/atmosphere system on Earth" is not so poetic, no.
posted by Zalzidrax at 10:36 PM on June 30, 2019 [1 favorite]
posted by Zalzidrax at 10:36 PM on June 30, 2019 [1 favorite]
the more massive an object is, the faster it should sensibly fall. Inexplicably, it does not.
Not this again.
"Welcome to Frictionless Railways, our unique technology [patents dreamt of] allows us to move objects with no friction at all!"
Exhibit A is a 10kg payload.
Exhibit B is a 100kg payload.
"I invite you to apply a force of 1 to both payloads on our frictionless trackway."
What? Exhibit B Inexplicably does not accelerate as much as Exhibit A even with no friction!
"Aha", you say - "of course it doesn't - you have forgotten about inertia! Only a fool would expect the same force to accelerate 2 different masses by the same amount. That's been known since Newtons time."
"Indeed, indeed", I say, crestfallen. "I know, lets apply ten times the force to Exhibit B - so the force is proportional to its mass."
So not I apply force 1 to Exhibit A, and force 10 to exhibit B.
I'm applying 10 times the force to Exhibit B, so it should sensibly accelerate faster than Exhibit A right? Inexplicably, it does not.
posted by HiroProtagonist at 10:37 PM on June 30, 2019 [3 favorites]
Not this again.
"Welcome to Frictionless Railways, our unique technology [patents dreamt of] allows us to move objects with no friction at all!"
Exhibit A is a 10kg payload.
Exhibit B is a 100kg payload.
"I invite you to apply a force of 1 to both payloads on our frictionless trackway."
What? Exhibit B Inexplicably does not accelerate as much as Exhibit A even with no friction!
"Aha", you say - "of course it doesn't - you have forgotten about inertia! Only a fool would expect the same force to accelerate 2 different masses by the same amount. That's been known since Newtons time."
"Indeed, indeed", I say, crestfallen. "I know, lets apply ten times the force to Exhibit B - so the force is proportional to its mass."
So not I apply force 1 to Exhibit A, and force 10 to exhibit B.
I'm applying 10 times the force to Exhibit B, so it should sensibly accelerate faster than Exhibit A right? Inexplicably, it does not.
posted by HiroProtagonist at 10:37 PM on June 30, 2019 [3 favorites]
FWIW, I think this is a great FPP but IMO the comments went off the rails ("and I helped!") over the chlorophyll thing in the first article.
It would be interesting to hear if anyone has any thoughts about the subsequent articles, particularly about symmetry and quantum computation.
posted by sjswitzer at 4:07 AM on July 2, 2019
It would be interesting to hear if anyone has any thoughts about the subsequent articles, particularly about symmetry and quantum computation.
posted by sjswitzer at 4:07 AM on July 2, 2019
I just came across this blog post by Peter Woit where he accuses the author KC Cole of portraying themselves as an expert in neutrino physics, when she is a really journalist with a BA in political science. Really odd.
posted by polymodus at 1:08 AM on July 14, 2019
posted by polymodus at 1:08 AM on July 14, 2019
The problem is that a leaf is not a closed system, and you can't really make it approximate one "theoretically." One of the major products, oxygen, gets vented to the atmosphere. And that takes not just the raw mass of the O2 but also the energy it took to rip the atoms off the water.
Actually, the technicality is this:
"The mass-energy relation, moreover, implies that, if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease. Such a conversion of rest energy to other forms of energy occurs in ordinary chemical reactions, but much larger conversions occur in nuclear reactions. "
—britannica
posted by polymodus at 1:28 AM on July 14, 2019
Actually, the technicality is this:
"The mass-energy relation, moreover, implies that, if energy is released from the body as a result of such a conversion, then the rest mass of the body will decrease. Such a conversion of rest energy to other forms of energy occurs in ordinary chemical reactions, but much larger conversions occur in nuclear reactions. "
—britannica
posted by polymodus at 1:28 AM on July 14, 2019
I came across a very interesting 7 minute Veritasum video the other day which claimed that the vast majority (~99%) of the mass of ordinary matter, in the example they chose of the human body, consists not in interactions with the Higgs field which gives electrons their mass, or even in the Higgs-attributable mass of quarks which make up protons and neutrons, but in the energy it takes to suppress vacuum fluctuations in the flux tubes between the bound quarks that make up the protons and neutrons.
So in a very real sense, our mass is mainly due to energy very like the energy that adds a miniscule amount of mass to a liquid which gets heated up.
posted by jamjam at 12:19 PM on July 14, 2019 [1 favorite]
So in a very real sense, our mass is mainly due to energy very like the energy that adds a miniscule amount of mass to a liquid which gets heated up.
posted by jamjam at 12:19 PM on July 14, 2019 [1 favorite]
- How (Relatively) Simple Symmetries Underlie Our Expanding Universe - "Although Einstein's theory of space-time seems more complicated than Newtonian physics, it greatly simplified the mathematical description of the universe."
- Ask Ethan: Why Do Gravitational Waves Travel Exactly At The Speed Of Light? - "General Relativity has nothing to do with light or electromagnetism at all. So how do gravitational waves know to travel at the speed of light?"
- What Is the Source Code for Reality? or Physics of the Big Bang, Hopf fibrations, Gauge Theory, and Spin - Eric Weinstein and Joe Rogan (cw: 'intellectual dark web' adjacent! and thiel lieutenant ;)
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Solar energy arrives on Earth and becomes mass in the form of green leaves,
Does the author know how to science?
posted by notsnot at 5:27 AM on June 30, 2019 [11 favorites]