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Australian Time Scientist Says that Time "Passing" is an Illusion
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Yes, I've seen that 4-D tesseract shadow-of-cube in 3D before. I don't really comprehend it. Do any of you? I remember having a math professor tell us that some of her friends could visualize up to 5 or 6 dimensions. That was beyond me. Note I think that the lowest dimensional unified field theory may have 11 dimensions (Some of the dimensions being rolled up so tightly that we can't see them. I think Kaluza first hypothesized this for unifying gravity and electromagnetic theory. Einstein as a peer reviewer initially rejected it, but later changed his mind and said it was worth pursuing.) Some unified theories have way more dimensions. Note that no dimension beyond our usual 4 has ever been discovered, although scientist are looking.
I miss Carl Sagan's Cosmos TV series.
I miss Carl Sagan's Cosmos TV series.
With all due respect of someone who's not as familiar with this, I would still disagree.
I included the caveman gif because I couldn't find a good Encino Man one.
I did this as an example where, for the caveman who was in suspended animation, in his mind he has "time traveled into the future", but to everyone else, time has passed him by.I feel this is basically the same for someone travelling at super high speeds where everything slows down for them. However, it does become interesting if you consider that all matter in our world is currently travelling through space at a certain speed and our "time" is basically reference to everything else around us. Then travelling faster or slower than the speed of everything else changes your concept of time. "Time travel" them is a bit more fitting.
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ThirstyBarbarian
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rcktnut
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Maybe there are really big people keeping us as pets with the universe in an aquarium.
Funkworks
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A tesseract is apparently for representing 4 dimensions that are equivalent. But in special relativity, the time dimension is unlike the 3 spatial dimensions. For that reason, I would not discuss tessaracts in a context of relativity. (if some pros have done it, I am not aware)
Leaving to come back when everyone and everything is older than the traveller. If that isn't travelling to the future, I don't know what is. But don't take my word for it, here are a few more links if you're interested:
minutephysics;
fermilab;
physicsgirl.
These are all different ways to explain the Lorentz transformations (Prof. Lorentz hatched these equations first, and then Einstein showed that if the speed of light was a universal constant, then the Lorentz transformations necessarily followed).
She has two series I know of: Cunk on Britain (much of which is on YouTube), and the newer Cunk on Earth.
rcktnut
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I've been watching this, very good also. Everything about the Universe is so unbelievable to the extent that anything (theories) is/ are believable.
Yes, it is my understanding that Lorentz discovered those factors first (before Einstein) in order to translate the Maxwell's equations from one inertial reference frame to another. However, he didn't realize that the very same factors also show that space and time can be transformed, too. Thus, he did not make the connection to the start of Special Relativity.
I won't say that anything is believable, but certainly there are many proposals based in theory that tax my ability to believe. Yes, the edge of the observable universe is about 13 billion years back in time or our universe is about 13 billion years old. However, the diameter of our universe is on the order of 30 billion light years. How can this be? It is consistent with General Relativity, because our universe is expanding. Within the context of GR some non-material bodies can move faster than the speed of light. The edge of a shadow is listed as one. The "boundary of our universe" is another. So, while the farthest light has been racing toward us for us to see, space is being creating as the universe expands, so that the diameter of our universe is around 30 billion light years.
There are many wild interpretations out there. Another one is that our space-time is some kind of holograhic projection from the surface of black holes.
Funkworks
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Maxwell had a wave equation for electromagnetic fields, which included a speed. People were used to the speed of a wave being dependent on a medium (sound in air, water waves, violin cords, etc.), so people started looking for a medium for electromagnetic fields (ether). After they failed, Einstein basically thought something like "what if there is in fact no medium and the wave speed is constant and the same for everyone?" Not obvious.
Maxwell's equations?
Funkworks
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Historically (1700s), d'Alembert used Newton's laws to create a mechanical wave equation, which can express the behavior of a guitar, piano, or violin string, the string in the video, with some adjustments, and sound, with some adjustments.
Then (1800s), Maxwell found symmetry in the known electromagnetic laws by adding some bits, and used the result (now called Maxwell's equations) to create electromagnetic wave equations.
Then (1900s), Bohr and de Broglie thought an electron might be some kind of wave, and Schrodinger sought a wave equation for an electron around a hydrogen atom (the simplest atom). What he found is appropriately called the Schrodinger equation. (Solutions of the Schrodinger equation are the atomic orbitals seen in chemistry classes.)
So historically, yes, Schrodinger's equation is inspired by both d'Alembert's mechanical wave equation and Maxwell's electromagnetic wave equations.
But, Maxwell's electromagnetic wave equations are not strictly required to understand Schrodinger's equation (quantum mechanics). Students first learn to work with the mechanical wave equation. This provides visuals allowing us to better tackle Maxwell's and Shrodinger's more abstract equations later on.
Mathematically, these are all forms of the wave equation, but used for different experimental observables: mechanical amplitude (d'Alembert's), field amplitude (Maxwell's), probability amplitude (Schrodinger's).
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Are Maxwell's equations a routine part of the modern syllabus?
Funkworks
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Definitely. Not just routine but mandatory. There's no way around them. Newton's, Maxwell's and Shrodinger's are the core of the modern physics syllabus. They neatly tie everything together. Then, people specialize. Physicists explore them in detail, while engineers use what they need to make useful things ASAP.
Edit: Even the basic electromagnetic laws you might have seen in highschool, whichever they are, Maxwell's equations include them all and ties them together. I've never even heard of an alternative theory for electricity and magnetism. Literally the most reliable statements I know of.
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I can remember during my degree having to derive Maxwell's and Shrodinger's equations from first principles.
As an old electronic engineering manager told us once, all our calculations, rules of thumb and even the circuits we design are just approximations for Maxwell's equations.
As an old electronic engineering manager told us once, all our calculations, rules of thumb and even the circuits we design are just approximations for Maxwell's equations.
Yes, QM and QFT can be derived from first principles by minimizing the path integral for the langrangian in accordance with calculus of variations.
Maxwell's equations describe the elwctromagnetc field. All physical laws like f=ma, Maxwell's eqns, etc. are the same in all inertial reference frames. Using the principle of Least Action described in my laast post one can derive QED.
Funkworks
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Experiments led to Newton's laws, which are now considered first principles of mechanics.
Experiments led to Maxwell's equations, which are now considered first principles of electromagnetism.
Schrodinger's equation is an assumption, that leads to results matching experiment, and is therefore a first principle of atomic scale behavior.
That's what I understand by "first principles". However, theorists can start from deeper "first principles" and derive the above (like starting from the principle of least action and obtain Newton's laws). So "first principles" is a bit of a fuzzy phrase because one has options as to where to start. People usually pick the easiest math possible for the problem at hand.
Experiments led to Maxwell's equations, which are now considered first principles of electromagnetism.
Schrodinger's equation is an assumption, that leads to results matching experiment, and is therefore a first principle of atomic scale behavior.
That's what I understand by "first principles". However, theorists can start from deeper "first principles" and derive the above (like starting from the principle of least action and obtain Newton's laws). So "first principles" is a bit of a fuzzy phrase because one has options as to where to start. People usually pick the easiest math possible for the problem at hand.
Actually schrodingers eqn can be deprived from the Principle of Least Action. It is often introduced to undergrads in a cook book fashion. I have a good book on calculus of variations that shows the derivation.
Funkworks
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I think I know what you mean but since the introduction of Planck's constant is arbitrary, it isn't a derivation in the usual sense.
The principle of least action is purely classical (1800s) and cannot predict Planck's constant.
Planck had to postulate his constant (1901) for Schrodinger to use it (1925). Schrodinger's equation including Planck's constant is presented as a postulate (although it can be truly derived from later formulations of QM).
(See "Schrodinger" in here: )
https://en.wikipedia.org/wiki/Hamilton–Jacobi_equation
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Sure, it uses Plancks constant, but the derivation goes far beyond that. Einstein GR contains the gravitational constant. That doesn't mean he didn't derive GR.
Funkworks
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The gravitational constant is from Newton and Cavendish's measurements in the 1700's. Relativity ultimately sprouts from Newtononian mechanics and Maxwell's electromagnetism. Einstein tied the two.
Planck introduced his constant to fit an experimental curve (blackbody spectrum) that could not be explained with either Newton's or Maxwell's.
De Broglie guessed that Planck's constant was related to momentum. Shrodinger plugged de Broglie's relation in Newtonian (classical) mechanics to create the Shrodinger equation, which is now seen as the starting point of QM theory and the way to start solving an atomic-scale problem.
Here's the simplest way to build Shrodinger's equation. Basically a summary of what he did. At about 3 min, de Broglie's relation (Planck's constant) is used. It's an add-on to account for atomic behavior, which was previously unknown.
Planck introduced his constant to fit an experimental curve (blackbody spectrum) that could not be explained with either Newton's or Maxwell's.
De Broglie guessed that Planck's constant was related to momentum. Shrodinger plugged de Broglie's relation in Newtonian (classical) mechanics to create the Shrodinger equation, which is now seen as the starting point of QM theory and the way to start solving an atomic-scale problem.
Here's the simplest way to build Shrodinger's equation. Basically a summary of what he did. At about 3 min, de Broglie's relation (Planck's constant) is used. It's an add-on to account for atomic behavior, which was previously unknown.
I'd humbly disagree.
In essence time slows for you and when you return it is the future, but they don't see you as a time traveller anymore than Futurama Fry or Captain America were seen by others as time travelers.
Now if you can return back to your time, then you're a time traveler, but I have yet to hear of a way for that, so I'd say it's more of a "time lagger".
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Yes.
1. In the year 2000, each of two twins is 30 years old.
2. The travelling twin travels near lightspeed for 1 year on his watch and heart beat, and comes back to Earth. At this point, he is 31 years old.
3. During the trip, the stay-put twin might have seen 20 years pass by, so it's 2020 on Earth, and he's 50 years old.
4. It's 2020, they meet again. The stay-put twin is 50 years old, while the travelling twin is 31 years-old.
5. The 50 year-old stay-put twin receives his 31 year-old travelling brother in 2020, as a guy from 2000.
6. The 50 year-old stay-put twin receives his 31 year-old travelling brother in 2020, as a guy from the past.
That's impossible. (wormholes and quantum effects are for particles and some of their properties, not people.)
Classical Quantum Mechanics for non-relativistic speeds starts with the classical conservation of energy. The Principle of Least Action starts with the Lagrangian L=T - V and so return will return the same equations of motion consistent with the classical conservation of energy. Actually, the derivation in post #83 is completely consistent with Principle of Least Action. The book, "Calculus of Variations" by Robert Weinstock shows how the Schrodinger equation can be derived. Feynman has a lecture on this subject, too.
https://www.feynmanlectures.caltech.edu/II_19.html
https://www.feynmanlectures.caltech.edu/II_19.html
Conceivably, one could write Einstein's formula for General Relativity very simply in tensor form as:
G = 8 pi g0 T
There may be some "c" terms in this equation that have been dropped. In any case writing the equation is deceptively over simplified. The G is often called Einstein's tensor, pi is 3.14..., g0 is the universal gravitational constant, and T is the mass energy tensor. The popular understanding at the time Einstein introduced this equation was that the universe had always existed. So, Einstein interested a Cosmological constant to make this equation reflect that concept. In the late 1920's things began to change. In 1927 Lemaitre introduced his solution for Einstein's equation showing an expanding universe. Later, Hubble in 1929 published his results that the universe is expanding. Einstein later said that his introduction of the Cosmological constant was the biggest mistake of his life. So, I would think that one interpretation would be that space is expanding and so time is expanding, too. You have to realize that the G on the LHS of the GR equation describes the metric tensor that was talked about earlier in this thread with regard to the invariant. The metric tensor describes the differentials of space and time with any chosen reference frame. Using the concept of covariant differentiating any reference frame is just as valid as any other. I would say that time is unfolding as viewed from my reference reference frame and/or any other reference frame. Others might argue that the block universe includes all of this.
G = 8 pi g0 T
There may be some "c" terms in this equation that have been dropped. In any case writing the equation is deceptively over simplified. The G is often called Einstein's tensor, pi is 3.14..., g0 is the universal gravitational constant, and T is the mass energy tensor. The popular understanding at the time Einstein introduced this equation was that the universe had always existed. So, Einstein interested a Cosmological constant to make this equation reflect that concept. In the late 1920's things began to change. In 1927 Lemaitre introduced his solution for Einstein's equation showing an expanding universe. Later, Hubble in 1929 published his results that the universe is expanding. Einstein later said that his introduction of the Cosmological constant was the biggest mistake of his life. So, I would think that one interpretation would be that space is expanding and so time is expanding, too. You have to realize that the G on the LHS of the GR equation describes the metric tensor that was talked about earlier in this thread with regard to the invariant. The metric tensor describes the differentials of space and time with any chosen reference frame. Using the concept of covariant differentiating any reference frame is just as valid as any other. I would say that time is unfolding as viewed from my reference reference frame and/or any other reference frame. Others might argue that the block universe includes all of this.
Personally, I think this Australian "Time Scientist" is an "illusion" . . . Wild, un-proveable theories are not the basis of "Good Science" !
Dave F.
Dave F.
