I bumbled onto this that talks about something call E8, a possible sought after unifying theory. I can't vouch for any of it, and in a couple of places, it lost me, but I was able to stay with it better than I can trying to follow string theory. All that aside, I found it interesting enough to think it may be worth posting. It starts out presenting some of those hard to wrap your head around ideas that we we are all familiar with from those college sophomore bull sessions after midnight while drinking. Then it gets into E8, and takes on a more serious tone, and explains what we might understand so far about E8 and it's relationship to reality. Mostly I found it fun to think about it. I have no idea if it's well known in physics or if someone is just presenting a brain teaser.
https://www.youtube.com/watch?v=eRmZ_sNf2mE
Well, it's not new, but it is interesting. I don't know what the current status of this is, but I hope someone's still thinking about it.
A material view of a being, implies that as part of the universe, we individually and collectively have always been "in the pool". So far so good. Then it gets fishy ...
A fish per se can't see beyond the water. The analogy of the girl in the pool, she is meta, breaking the 4th wall, head out of the water, talking to another version of herself not in the pool.
I may look at all of this clip later, but since it is getting all wet, in philosophy, probably not.
Quote from: Baruch on September 10, 2019, 04:56:32 PM
A material view of a being, implies that as part of the universe, we individually and collectively have always been "in the pool". So far so good. Then it gets fishy ...
A fish per se can't see beyond the water. The analogy of the girl in the pool, she is meta, breaking the 4th wall, head out of the water, talking to another version of herself not in the pool.
Please stop!
Quote from: drunkenshoe on September 10, 2019, 04:57:19 PM
Please stop!
Go back to Ankara (and resume Galatian heritage).
Quote from: Baruch on September 10, 2019, 05:06:13 PM
Go back to Ankara (and resume Galatian heritage).
Come on, man.
Quote from: drunkenshoe on September 10, 2019, 05:08:14 PM
Come on, man.
If you have ancestors from Ankyra, then you probably have Galatian heritage (and Hittite). That Gaul component explains why you have so much gall ;-)
Quote from: Baruch on September 10, 2019, 05:11:05 PM
If you have ancestors from Ankyra, then you probably have Galatian heritage (and Hittite). That Gaul component explains why you have so much gall ;-)
Fuck my heritage, Baruch. Breathe. Please.
Quote from: Baruch on September 10, 2019, 05:11:05 PM
If you have ancestors from Ankyra, then you probably have Galatian heritage (and Hittite). That Gaul component explains why you have so much gall ;-)
So what does any of that have to do with the opening post, or the subject under discussion? Can you engage in a conversation without derailing it?
Quote from: drunkenshoe on September 10, 2019, 05:18:54 PM
Fuck my heritage, Baruch. Breathe. Please.
Typical SJW ... cutting of the tree your branch is connected to.
Quote from: Unbeliever on September 10, 2019, 05:20:56 PM
So what does any of that have to do with the opening post, or the subject under discussion? Can you engage in a conversation without derailing it?
Defend drunkenshoe if you want, she was being cryptic. But I don't put anyone on ignore.
I have commented for now. Be happy with that.
https://www.youtube.com/watch?v=E-LC_l3gNuc
https://www.youtube.com/watch?v=aR88KR4sg-w
QuoteE8 Lie group and E8 Lattice has sometimes been called the most beautiful mathematical structure in the world. Is it the theory of everything or the true nature of reality? It even has an entire research company behind it called "Quantum Gravity Research"
It is a 248 dimensional object, but it can also be thought of as an object that has 8 spatial dimensions, with 248 symmetries.
Why is this structure important? Well, it happens to show up in parts of String Theory. But also in 2007, a theoretical physicist Antony Garrett Lisi published a paper proclaiming that the mathematics of this structure contained all the particles and forces in the universe. He called it the “the exceptionally simple theory of everything†What Lisi did is he found a relationship between this object and all the forces and particles we know about.
According to the standard model, there are 4 fundamental forces in nature, strong force, weak force, electromagnetism and gravity. And there are 12 fundamental particles. In addition, each of these particles has a antiparticle of itself. In total, these make up all the elementary particles, and there are exactly 28 of them. 24 elementary particles, and 4 force carrier particles. Each of these distinct elementary particles has eight quantum numbers assigned to it, based on the charges each particle has.
This brings the number of distinct particles to 224.
Lisi found that he could mathematically equate all of these particles to one of the points in the E8 model.
But the model has 248 points, not 224. So what about the empty 24 extra points? He simply created 24 new theoretical particles.
Notice how the lines radiate from each point: Lisi also found patterns emerging between particles and forces like they happen in actual reality â€" for example, when photons interact with leptons, they create electrons. The same thing happens in the E8 lattice. The connections shown within points on the E8 match up to real, known connections between particles in our physical world.
One of the particles he assigned to this shape behaves very much like the force carrier for gravity â€" a graviton. And this is the key to Lisi claiming that this could be the “theory of everything.†â€" because it combines matter particles and gravity in one framework.
So Basically, all the normal things we know about can be described in terms of algebraic objects, and each of these objects happens to sit inside this complicated E8 structure.
Lisi's theory does have some problems. One of the biggest problems with the theory is that Lisi combines the force carrying particles, Bosons with the matter particles. String theory does this too, but with the rigorous mathematics to go with it. This math is not present in E8, so Lisi combining these appears to be arbitrary.
In addition, a leading mathematician and expert on Lie groups, Skip Garibaldi wrote a paper in 2010 which mathematically disproved Lisi. But Lisi came back with counter arguments to that.
But the elephant in the room is the 24 new theoretical particles that come out of this theory. So it requires the existence of undiscovered matter. However, since the startup of the Large Hardon Collider, it is possible one of lisi’s 24 new theoretical particles could be found. Lisi himself says, "I'm the first to admit that it's a long shot."
In fact, I think that even if one of the new theoretical particles is found, it would be a huge breakthrough towards proving this theory is on the right track.
How does this compare to string theory? At least there is a way to prove it, unlike string theory â€" where we don’t really have a way to prove it.
And although E8 has a vast number of dimensions, the physical universe described by the theory would have only the four dimensions we are familiar with and not the 10 or 11 of string theory.
You may have heard of a research organization called Quantum Gravity Research. This group has built a whole company around the idea of E8 being the theory of everything. They have some really well produced and slick videos on you tube that you can check out for yourself. They are like mini movies with actors, special effects, and animations. So I commend them for making this science approachable to everyday people.
The problem with their videos is they are mixing actual proven concepts in physics with a lot of unproven concepts, including new age mysticism. This really diminishes their credibility in my view because the viewer doesn’t know which part is true and which part is conjecture.
E8 is a real mathematical structure. It has been around for a long time. Quantum Gravity Research people did not come up with it.
And I think it’s an interesting idea. All that needs to be done, is for the large hadron collider to find at least one of 24 theoretical particles, and this theory may get hoards of scientists singing its praises.
Jacques Distler and Skip Garibaldi say, "There is no "Theory of Everything" inside E8 (https://arxiv.org/pdf/0905.2658.pdf)."
Quote from: PopeyesPappy on September 10, 2019, 09:13:52 PM
Jacques Distler and Skip Garibaldi say, "There is no "Theory of Everything" inside E8 (https://arxiv.org/pdf/0905.2658.pdf)."
I appreciate that. Science is based on brisk debate, challenge, and change. I was in elementary school when my geography teacher mentioned plate tectonics. She introduced it as a given, which I could accept quite easily because rocks and continents on such a big scale act like smaller softer mixtures of water and solids.
Consider that all the water and all the continents are bent to fit the curvature of the Earth. This may be wrong, nor did my teacher present it that way. It's something I visualized on my own. Her weakest justification for the theory I thought might have been here explanation that North and South America sort of fit together with the coast lines of Europe and Africa. I thought that was highly interesting, even if it was a highly interesting coincidence. Turns out that's exactly how it happened and the actual drift and it's speed has been measured.
But the strange part of all this that was unknown to me at the time, was that tectonic theory was under going contentious debate and had been for a long time, often regarded by other scientists a foolish conjecture. And stranger still was that I recently read that tectonics was not universally accepted until the 1970s, at least according the source I read. That was a few years after I finished college, and here I had been believing tectonics was real, when science wasn't even agreeing about it. There was a hot scientific debate that I lived through, and wasn't I wasn't even aware of the chaos that was actually taking place. Many of these sorts of lengthy debates happen in science, and much of it doesn't even involve religions until they begin to realize there toes are being stepped on. And then we have to go through all the shit over again until the Pope makes a statement that the new knowledge actually shows the mysterious wonder of God's love.
There's a lot of figuring out that science has to do. It was much easier when the answers were provided by stargazing goat herders spending long nights in the dark, with only the help of dim light from newly discovered fire.
Quote from: PopeyesPappy on September 10, 2019, 09:13:52 PM
Jacques Distler and Skip Garibaldi say, "There is no "Theory of Everything" inside E8 (https://arxiv.org/pdf/0905.2658.pdf)."
Perhaps one must simply refer to a "larger" group ... say the Monster Group ...
https://en.wikipedia.org/wiki/Monster_group#McKay%27s_E8_observation
It is surpassing strange it is not, that continents float on the mantle like a rubber ducky in a baby's bath water?
Quote from: SGOS on September 10, 2019, 10:07:53 PM
I appreciate that. Science is based on brisk debate, challenge, and change. I was in elementary school when my geography teacher mentioned plate tectonics. She introduced it as a given, which I could accept quite easily because rocks and continents on such a big scale act like smaller softer mixtures of water and solids.
Consider that all the water and all the continents are bent to fit the curvature of the Earth. This may be wrong, nor did my teacher present it that way. It's something I visualized on my own. Her weakest justification for the theory I thought might have been here explanation that North and South America sort of fit together with the coast lines of Europe and Africa. I thought that was highly interesting, even if it was a highly interesting coincidence. Turns out that's exactly how it happened and the actual drift and it's speed has been measured.
But the strange part of all this that was unknown to me at the time, was that tectonic theory was under going contentious debate and had been for a long time, often regarded by other scientists a foolish conjecture. And stranger still was that I recently read that tectonics was not universally accepted until the 1970s, at least according the source I read. That was a few years after I finished college, and here I had been believing tectonics was real, when science wasn't even agreeing about it. There was a hot scientific debate that I lived through, and wasn't I wasn't even aware of the chaos that was actually taking place. Many of these sorts of lengthy debates happen in science, and much of it doesn't even involve religions until they begin to realize there toes are being stepped on. And then we have to go through all the shit over again until the Pope makes a statement that the new knowledge actually shows the mysterious wonder of God's love.
There's a lot of figuring out that science has to do. It was much easier when the answers were provided by stargazing goat herders spending long nights in the dark, with only the help of dim light from newly discovered fire.
I older than modern science. In 1968, I asked the astronomy 101 professor why the arms of the Milky Way didn't get pulled to the center as it rotated and he told me it was "gravity waves". I said there had to be keeping the structure intact. Today we call that "dark matter".
When I was in Middle School, and observed that Africa and South America matched, they told me it was a coincidence. We now know that as Plate Tectonics. In high school we had a brief section on geology and I asked why some mountain ranges matched up across continents. They said it was coincidence. We now know that was further proof of plate tectonics.
Sometimes, I'm tired of being right all the time. I don't ask as many questions as I used to. I'm always told I'm wrong.
Lately, I've been thinking about gravity. In a way, it doesn't make sense... I don't like the spacetime analogy where a heavy ball on a trampoline moves around until it hits the heavy object in the center. It is something "not-that".
I suspect the next great advancement is going to be some concept that more resembles "reality" as we can sense it.
Quote from: SGOS on September 10, 2019, 10:07:53 PM
I appreciate that. Science is based on brisk debate, challenge, and change. I was in elementary school when my geography teacher mentioned plate tectonics. She introduced it as a given, which I could accept quite easily because rocks and continents on such a big scale act like smaller softer mixtures of water and solids.
Consider that all the water and all the continents are bent to fit the curvature of the Earth. This may be wrong, nor did my teacher present it that way. It's something I visualized on my own. Her weakest justification for the theory I thought might have been here explanation that North and South America sort of fit together with the coast lines of Europe and Africa. I thought that was highly interesting, even if it was a highly interesting coincidence. Turns out that's exactly how it happened and the actual drift and it's speed has been measured.
But the strange part of all this that was unknown to me at the time, was that tectonic theory was under going contentious debate and had been for a long time, often regarded by other scientists a foolish conjecture. And stranger still was that I recently read that tectonics was not universally accepted until the 1970s, at least according the source I read. That was a few years after I finished college, and here I had been believing tectonics was real, when science wasn't even agreeing about it. There was a hot scientific debate that I lived through, and wasn't I wasn't even aware of the chaos that was actually taking place. Many of these sorts of lengthy debates happen in science, and much of it doesn't even involve religions until they begin to realize there toes are being stepped on. And then we have to go through all the shit over again until the Pope makes a statement that the new knowledge actually shows the mysterious wonder of God's love.
There's a lot of figuring out that science has to do. It was much easier when the answers were provided by stargazing goat herders spending long nights in the dark, with only the help of dim light from newly discovered fire.
I older than modern science. In 1968, I asked the astronomy 101 professor why the arms of the Milky Way didn't get pulled to the center as it rotated and he told me it was "gravity waves". I said there had to be keeping the structure intact. Today we call that "dark matter".
When I was in Middle School, and observed that Africa and South America matched, they told me it was a coincidence. We now know that as Plate Tectonics. In high school we had a brief section on geology and I asked why some mountain ranges matched up across continents. They said it was coincidence. We now know that was further proof of plate tectonics.
Sometimes, I'm tired of being right all the time. I don't ask as many questions as I used to. I'm always told I'm wrong.
Lately, I've been thinking about gravity. In a way, it doesn't make sense... I don't like the spacetime analogy where a heavy ball on a trampoline moves around until it hits the heavy object in the center. It is something "not-that".
I suspect the next great advancement is going to be some concept that more resembles "reality" as we can sense it.
Quote from: Cavebear on September 11, 2019, 02:23:36 AM
Lately, I've been thinking about gravity. In a way, it doesn't make sense... I don't like the spacetime analogy where a heavy ball on a trampoline moves around until it hits the heavy object in the center. It is something "not-that".
I suspect the next great advancement is going to be some concept that more resembles "reality" as we can sense it.
Gravity is strange. I get that matter seems to be attracted to matter. That's seems simple enough... but Why?? Every time I look at the ball on the trampoline, all I really understand is that the ball weighs down the center of the trampoline. I understand that this is an analogy, but it is of little help to my understanding of gravity, which doesn't seem to act like the trampoline or the ball. I do award creativity points to the guy that came up with that, because I sense that it must be a clever analogy, even if I don't understand why it's clever.
Quote from: SGOS on September 11, 2019, 11:45:17 AM
Gravity is strange. I get that matter seems to be attracted to matter. That's seems simple enough... but Why?? Every time I look at the ball on the trampoline, all I really understand is that the ball weighs down the center of the trampoline. I understand that this is an analogy, but it is of little help to my understanding of gravity, which doesn't seem to act like the trampoline or the ball. I do award creativity points to the guy that came up with that, because I sense that it must be a clever analogy, even if I don't understand why it's clever.
Short explanation. Imagine that everything moves in a straight line, at constant speed, but not in the same directions (inertia). In a flat 3d space, all the trajectories are straight lines. Imagine a sphere. A straight line on the surface of a sphere, is a great circle, not a straight line. It is curved. So in a non-flat 3d space, all trajectories on average are non-straight lines. Then take that idea and apply it to 4d space-time. It isn't Euclidean, even when flat, because time isn't the same as space. But in flat space-time, trajectories are still straight lines, even if they behave funny in Special Relativity. Finally, extend from flat space-time to non-flat space time. At any given point in space-time (potential event location) you can draw an imaginary 4d spherical surface of a 4d sphere that describes the non-straight lines that form the previous straight lines that go thru there. in all spaces called geodesics. This imagery 4d spherical surface, varies as you go along the path of a test particle. The reciprocal of the radius of this imaginary sphere, is the local curvature. In a flat space, this radius is infinity, so the curvature is zero.
Differential geometry (study of fancy surfaces and paths on them) only works for GR, not for QT. In QT there are no test particles and no trajectories. And since gravity is so weak, even a mass the size of the Sun, doesn't do much gravitational lensing. And I have known this with full mathematics since I was 16.
Quote from: Baruch on September 11, 2019, 11:57:48 AM
Short explanation. Imagine that everything moves in a straight line, at constant speed, but not in the same directions (inertia). In a flat 3d space, all the trajectories are straight lines. Imagine a sphere. A straight line on the surface of a sphere, is a great circle, not a straight line. It is curved. So in a non-flat 3d space, all trajectories on average are non-straight lines. Then take that idea and apply it to 4d space-time. It isn't Euclidean, even when flat, because time isn't the same as space. But in flat space-time, trajectories are still straight lines, even if they behave funny in Special Relativity. Finally, extend from flat space-time to non-flat space time. At any given point in space-time (potential event location) you can draw an imaginary 4d spherical surface of a 4d sphere that describes the non-straight lines that form the previous straight lines that go thru there. in all spaces called geodesics. This imagery 4d spherical surface, varies as you go along the path of a test particle. The reciprocal of the radius of this imaginary sphere, is the local curvature. In a flat space, this radius is infinity, so the curvature is zero.
Differential geometry (study of fancy surfaces and paths on them) only works for GR, not for QT. In QT there are no test particles and no trajectories. And since gravity is so weak, even a mass the size of the Sun, doesn't do much gravitational lensing. And I have known this with full mathematics since I was 16.
Tell the rest of the World about it. They are waiting.
Quote from: Cavebear on September 11, 2019, 12:04:37 PM
Tell the rest of the World about it. They are waiting.
Others have told this story since 1916. If they were deaf 100 years ago, they are still deaf now.
There are several possible reasons why GR and QFT have't been surpassed:
1. There are different "magisteria" there isn't a single law to cover all models of physics
2. The difference between GR and QFT are basic, not superficial. A new mathematical conception may be required, like Fourier analyzing heat. Though epicycles and trigonometric functions are much older than him. What trick was required, is trigonometry had to go past the real numbers to the complex numbers. Real number trigonometry functions don't have enough moving parts to do the job.
And no amount of physics nor math makes any difference to the larger world of humanity.
Smacks too much of Kepler and his attempt to build a solar system model based on the Platonic solids. Also, 'mathematically disproven' doesn't leave much room for counter-argument. And I'm unimpressed that there's a company set up around the idea. Science is done by doing science, not by a marketing department.
Quote from: trdsf on September 11, 2019, 12:44:54 PM
Smacks too much of Kepler and his attempt to build a solar system model based on the Platonic solids. Also, 'mathematically disproven' doesn't leave much room for counter-argument. And I'm unimpressed that there's a company set up around the idea. Science is done by doing science, not by a marketing department.
I have to smile. Reading what Baruch posted, I was thinking about Kepler trying to make his perfect shapes explain the universe he saw. Not that I mean Baruch is worrying about perfect shapes, but that he has a flawed view of science.
Quote from: Cavebear on September 11, 2019, 01:10:30 PM
I have to smile. Reading what Baruch posted, I was thinking about Kepler trying to make his perfect shapes explain the universe he saw. Not that I mean Baruch is worrying about perfect shapes, but that he has a flawed view of science.
Flawed view of philosophy of science ... not the same. And in philosophy, there is no "correct".
Quote from: Baruch on September 11, 2019, 01:13:29 PM
Flawed view of philosophy of science ... not the same. And in philosophy, there is no "correct".
Tell that to a philosophist. I've actually read modern philosophy and they are generally a bunch of whackos.
Quote from: SGOS on September 11, 2019, 11:45:17 AM
Gravity is strange. I get that matter seems to be attracted to matter. That's seems simple enough... but Why?? Every time I look at the ball on the trampoline, all I really understand is that the ball weighs down the center of the trampoline. I understand that this is an analogy, but it is of little help to my understanding of gravity, which doesn't seem to act like the trampoline or the ball. I do award creativity points to the guy that came up with that, because I sense that it must be a clever analogy, even if I don't understand why it's clever.
I've been wondering lately how time and gravity are related. Time slows down in a reference frame that's in a strong gravity field, and I wonder whether it's the slowing of time that's important in the "tug" of gravity. Maybe things "want" to move as slowly through time as possible, so they "gravitate" in the direction of slower time.
It's been said that acceleration and gravity are equivalent, but there is a difference. In a gravity field, such as the surface of the Earth, time flows more slowly at sea level than it does at, say, 40 miles higher. But if you were accelerating in a space ship that was 40 miles long, you wouldn't measure any difference in the flow of time between the front end and the back end. Any time dilation would be the same no matter where in the ship you were.
Quote from: Unbeliever on September 11, 2019, 01:33:51 PM
I've been wondering lately how time and gravity are related. Time slows down in a reference frame that's in a strong gravity field, and I wonder whether it's the slowing of time that's important in the "tug" of gravity. Maybe things "want" to move as slowly through time as possible, so they "gravitate" in the direction of slower time.
It's been said that acceleration and gravity are equivalent, but there is a difference. In a gravity field, such as the surface of the Earth, time flows more slowly at sea level than it does at, say, 40 miles higher. But if you were accelerating in a space ship that was 40 miles long, you wouldn't measure any difference in the flow of time between the front end and the back end. Any time dilation would be the same no matter where in the ship you were.
Those kinds of questions bother me as well. I expect that we will have some logical breakthrough that makes our sense of reality work again. Or maybe I'm just getting too old and the newest generation would even have a problem seeing the universe the new way.
I bet 10 quatloos I'm wrong...
Quote from: Unbeliever on September 11, 2019, 01:33:51 PM
I've been wondering lately how time and gravity are related. Time slows down in a reference frame that's in a strong gravity field, and I wonder whether it's the slowing of time that's important in the "tug" of gravity. Maybe things "want" to move as slowly through time as possible, so they "gravitate" in the direction of slower time.
It's been said that acceleration and gravity are equivalent, but there is a difference. In a gravity field, such as the surface of the Earth, time flows more slowly at sea level than it does at, say, 40 miles higher. But if you were accelerating in a space ship that was 40 miles long, you wouldn't measure any difference in the flow of time between the front end and the back end. Any time dilation would be the same no matter where in the ship you were.
And some claim time is secondary, not primary. But if that is so, so is space (SR ties them together). My POV. Everything is moving at the speed of light (not velocity of light). Speed is the length of the 4-vector in space-time. And of course each particle vector isn't at the same point in space-time. So basically N test particles at N points. The 4-vectors don't point in the same direction. They are never co-located. But the length is always the same. This is where people's grasp of Relativity goes bad ... "regular matter can't accelerate to the speed of light" ... "light is always at the speed of light". Not quite true. Matter particles can point in different directions from each other, but never point in the same direction in 4-d as any light particle. Light particles can point in different directions from each other, but never in the same direction in 4-d as a matter particle. Different propagation magisteria. It doesn't describe how they locally interact. QFT does.
So no question of tachyons, warp drives etc. Right now you and I are both moving at Warp One, but not in the same direction, not from the same event (4-d location).
Time flow. Light and matter both flow at the same speed, in a vacuum. When light and matter interact (index of refraction) is is a classical approximation that the speed of light in the material is slower than it was in the vacuum. But this is an approximation. That isn't what is happening in QFT. In QFT there are no test particles, no trajectories. Just statistical experiment outcomes. It doesn't even describe reality in the absence of humans.
Quote from: Unbeliever on September 11, 2019, 01:33:51 PM
I've been wondering lately how time and gravity are related. Time slows down in a reference frame that's in a strong gravity field, and I wonder whether it's the slowing of time that's important in the "tug" of gravity. Maybe things "want" to move as slowly through time as possible, so they "gravitate" in the direction of slower time.
These concepts are interesting. More to bend your brain, and it doesn't seem unreasonable. One day maybe, this will open new doors and send us in a new direction.
Quote from: Baruch on September 11, 2019, 04:51:47 PM
And some claim time is secondary, not primary. But if that is so, so is space (SR ties them together). My POV. Everything is moving at the speed of light (not velocity of light). Speed is the length of the 4-vector in space-time. And of course each particle vector isn't at the same point in space-time. So basically N test particles at N points. The 4-vectors don't point in the same direction. They are never co-located. But the length is always the same. This is where people's grasp of Relativity goes bad ... "regular matter can't accelerate to the speed of light" ... "light is always at the speed of light". Not quite true. Matter particles can point in different directions from each other, but never point in the same direction in 4-d as any light particle. Light particles can point in different directions from each other, but never in the same direction in 4-d as a matter particle. Different propagation magisteria. It doesn't describe how they locally interact. QFT does.
So no question of tachyons, warp drives etc. Right now you and I are both moving at Warp One, but not in the same direction, not from the same event (4-d location).
Time flow. Light and matter both flow at the same speed, in a vacuum. When light and matter interact (index of refraction) is is a classical approximation that the speed of light in the material is slower than it was in the vacuum. But this is an approximation. That isn't what is happening in QFT. In QFT there are no test particles, no trajectories. Just statistical experiment outcomes. It doesn't even describe reality in the absence of humans.
According to Lewis Carrol Epstein, in his book
Relativity Visualized (https://archive.org/stream/L.EpsteinRelativityVisualizedelemTxt1994Insight/L.%20Epstein%20-%20Relativity%20Visualized%20%5Belem%20txt%5D%20%281994%2C%20Insight%29_djvu.txt), we all travel at the speed of light, since everything travels at a space-time velocity of exactly "one." Faster travel through space means a slower passage through time, and vice versa, but the combination of the two always equals one.
Quote from: Baruch on September 11, 2019, 04:51:47 PM
Everything is moving at the speed of light (not velocity of light).
Almost nothing moves at lightspeed...
Quote from: Cavebear on September 11, 2019, 06:09:08 PM
Almost nothing moves at lightspeed...
Typical ignorance ... speed not equal to velocity. Unless you mean ... no perfect vacuum ... that that is only experimental light speed. All particles are themselves in vacuum ... relative to that they only move at light speed.
See, Star Trek and most of sci-fi are based on lay ignorance of SR. Sorry, no free lunch, no Space Communism etc.
Quote from: Unbeliever on September 11, 2019, 01:33:51 PM
I've been wondering lately how time and gravity are related. Time slows down in a reference frame that's in a strong gravity field, and I wonder whether it's the slowing of time that's important in the "tug" of gravity. Maybe things "want" to move as slowly through time as possible, so they "gravitate" in the direction of slower time.
I don't think they're related as such; it's just that gravity bends space and since the speed of light in a vacuum is a constant, if the distance is changed then the time also must change so that
c isn't changed.
Quote from: Unbeliever on September 11, 2019, 01:33:51 PM
It's been said that acceleration and gravity are equivalent, but there is a difference. In a gravity field, such as the surface of the Earth, time flows more slowly at sea level than it does at, say, 40 miles higher. But if you were accelerating in a space ship that was 40 miles long, you wouldn't measure any difference in the flow of time between the front end and the back end. Any time dilation would be the same no matter where in the ship you were.
A 40 mile long ship is accelerating as a unit, so you're going to make the same measurements both fore and aft. With a globe like the earth as the source of the acceleration force, you can move away from the center of mass, so that a sufficiently exact time measurement taken at sea level will not match a measurement taken the same way at 40 miles above sea level. The reason an accelerating ship is used as a model for some gravitational field effects is because acceleration and gravitational field strength are measured in the same terms: meters per second squared.
Quote from: trdsf on September 11, 2019, 11:53:13 PM
I don't think they're related as such; it's just that gravity bends space and since the speed of light in a vacuum is a constant, if the distance is changed then the time also must change so that c isn't changed.
But what does it mean to "bend" space? From our perspective, it seems to mean compression and expansion, but time is also affected, by slowing or speeding up. This gravitational time dilation is, I think, part and parcel of the bending of space/time. I just wonder is it the cause or the effect? Or is it more of an epiphenomenon that means little?
Quote from: Unbeliever on September 12, 2019, 01:24:10 PM
But what does it mean to "bend" space? From our perspective, it seems to mean compression and expansion, but time is also affected, by slowing or speeding up. This gravitational time dilation is, I think, part and parcel of the bending of space/time. I just wonder is it the cause or the effect? Or is it more of an epiphenomenon that means little?
Not quite. Light doesn't speed up/slow down relative to vacuum. The path gets shorter or longer. Consider a bow. The arch of the bow goes from point to point, same as the taut string. The length along the bow is longer, and it is thus curved. This isn't strange relative to SR. In SR, measured lengths vary depending on conditions. To keep the speed of light constant, the measured duration has to vary inversely.
Now what is real once you have SR and GR? The idea that measurement isn't objective across all circumstances ... was a reason for older scientists to reject relativity theory. In a given circumstance ... measurement is consistent. In that way, objectivity is maintained, in a narrower sense. This is because the older model, absolute space and absolute time ... objectivity would be there for all circumstances. As it turns out, only the speed of light maintains that larger consistency.
Einstein's view is that this isn't an epiphenomenon. What you measure, is what is. It isn't a distortion of some Platonic reality. So Einstein is an empiricist and rationalist. Plato was only pre-rationalist (and fantasist) because proper logic didn't get invented until Aristotle and the Stoics came along later. But what is real with QT or QFT ... there isn't any agreement yet on that. Except that all accurate models, predict the same experimental results (the Interpretation Problem). From Bohr's POV, that is what is real. What the experiment looks like, before you measure, isn't real. Even Einstein couldn't accept that. But Einstein was wrong. This is the "Measurement Problem". There are still many Quantum scientists who don't like it. The new Entanglement Experiment didn't solve this, it was already part of the (all accurate models).
Quote from: Unbeliever on September 12, 2019, 01:24:10 PM
But what does it mean to "bend" space? From our perspective, it seems to mean compression and expansion, but time is also affected, by slowing or speeding up. This gravitational time dilation is, I think, part and parcel of the bending of space/time. I just wonder is it the cause or the effect? Or is it more of an epiphenomenon that means little?
That's why they call it spacetime -- they're linked, like electricity and magnetism are linked. When space is curved by gravity, time is also altered by gravity. Neither is properly speaking the cause of, or the effect of, the other. Matter tells space how to bend, and space tells matter (and light) how to move; there's no way to divorce the two, nor give primacy to one over the other.
Curved or not, from the viewpoint of the light, it still looks like it's moving in a straight line. It's like being in an airplane carefully following the line of latitude at 40° -- from your perspective aboard the plane, you have clearly not deviated from a straight line, but (fuel concerns notwithstanding) if you keep following it you eventually discover yourself back where you started, so you have clearly followed a curved path that never looked curved.
I'm interested in the physics that involves bending space, through other means than gravity. Particularly the Albecurrie Warp drive, given GR equation of warp fields. Just means we'll have to get our hands on some quite exotic matter and energy generation.
PBS Space Time had a vid on it 4 years ago.
https://www.youtube.com/watch?v=94ed4v_T6YM
That drive takes some sort of exotic matter that doesn't exist, like unobtainium.
But the question of out-of-the-box spaceship drives has not been entirely neglected by scientists:
https://www.scientificamerican.com/article/the-good-kind-of-crazy-the-quest-for-exotic-propulsion/
One possibility being looked at is something called the Mach effect:
https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_I_Phase_II/Mach_Effect_for_In_Space_Propulsion_Interstellar_Mission/
Freelunchium is as rare as Unobtanium.
Exotic matter is dangerous, remember a new Star Trek movie about that ...
Survival is dangerous, so danger is life's middle name. We drop from our mothers' wombs, crawl across open country under fire, then fall into our graves.
Quote from: Unbeliever on September 14, 2019, 01:42:16 PM
Survival is dangerous, so danger is life's middle name. We drop from our mothers' wombs, crawl across open country under fire, then fall into our graves.
You will never achieve SJW-hood with that bad attitude ;-)
Quote from: Unbeliever on September 14, 2019, 01:35:10 PM
That drive takes some sort of exotic matter that doesn't exist, like unobtainium.
But the question of out-of-the-box spaceship drives has not been entirely neglected by scientists:
https://www.scientificamerican.com/article/the-good-kind-of-crazy-the-quest-for-exotic-propulsion/
One possibility being looked at is something called the Mach effect:
https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_I_Phase_II/Mach_Effect_for_In_Space_Propulsion_Interstellar_Mission/
Unfortunately, that first link is behind a paywall. Can you give a nickel tour of it?
Here's another link, see if it works:
https://agenparl.eu/the-good-kind-of-crazy-the-quest-for-exotic-propulsion/
Quote from: Unbeliever on September 15, 2019, 05:52:14 PM
Here's another link, see if it works:
https://agenparl.eu/the-good-kind-of-crazy-the-quest-for-exotic-propulsion/
Thank you, yes! Interesting article; NASA has been looking at weird technologies for a while. I'm trying to find the episode of The Infinite Monkey Cage where they spoke with Dr Robert Frisbee (http://discovermagazine.com/2003/aug/cover), who had been in charge of JPL's advanced propulsion concepts section. He made an interesting point: even a towering genius like Da Vinci, who himself strove for flight, could not imagine what form aircraft eventually took, even the earliest ones. The British Interplanetary Society tried to imagine interstellar craft in the 1930s, and even the 1960s work of Dyson and Bussard
et al. may be miles away from what the final designs of interstellar spacecraft look like because we don't really know all the problems to be overcome yet.
Really, we're only working on the most obvious one right now -- how the hell do you move something fast enough to travel huge distances without having to tug along a couple comets that can be electrolyzed into hydrogen and oxygen and recycled into rocket fuel, and how do you stop at the destination rather than flashing through so fast you only have time to take three blurry photos.
So yes, to ever get out of our planetary back yard, a program like NIAC is a great place to start. Regardless of whether they get a useful drive in the next five or ten or twenty years, they're going to learn
something interesting out of what they're funding.
I don't think anything they're currently working on will rival the Alcubierre drive, but if we take baby steps we might eventually get far.