Motor Daddy
Valued Senior Member
10^5,000 times the speed of light means that the object traveled 10^5,000 times farther than light in the same exact time.
The Problem of Time leads to a Problem of Energy for the Universe
- Thread starter Reiku
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10^5,000 times the speed of light means that the object traveled 10^5,000 times farther than light in the same exact time.
So it skipped space time like I said.
Motor Daddy
Valued Senior Member
What do you mean it skipped space time?
Minimal distance... C. You can't get from one point to another without crossing all points. You said..
Travelling farther than points is skipping space-time. How do you get from one place to another without crossing the same points as a photon? If you blast them out of the way you are in a black hole. A swimmer cannot go through water faster than the movement of water, else he throws the water out of the pool.
There is 4 dimensions, x,y,z, and t. That is, volume and time. You have to start at a location, and a duration of time later you are at an end location, which could be the same location if you didn't travel during that duration of time. You seem to imply an object can be at a location, and at the same time (no elapsed time) be at another location. Prove it. Prove that a point of an object can be at 2 separate locations at the same time, ie, the object is at 2,2,3 at 12:00 and it is also at 45,59,29 at 12:00.
I think the x,y,z refers to "location" in 3-D space at a time t . . . however, using your statement . . . . .(x) x (y) x (z), or volume as you say . . . . multiplied by t is a interesting 'lead-in' to visualizing universe expansion, IMO . . . .
I look in the pseudo section from time to time and I saw James had posted in a thread you'd started. I'd seen the thread before, I didn't bother to reply. I replied when you clearly bit off more than you could chew and couldn't honestly and correctly answer James's questions. There's plenty of your threads I'm not replying to.
I know you want to feel important but you really aren't.
Then you completely failed to understand the material.
I know Susskind knows it. But you have not reproduced definitions properly, you haven't given correct explanations, you've generally botched equations.
Simply saying "Some one else says all of this!" doesn't cut it. You might have listened to what they have to say but you obviously can't remember or understand it properly.
Except you then cut out essential bits, like removing every other paragraph from a book and expecting it to make sense.
The problem is you are still the boy you were 5 years ago. That's the fundamental problem you have. You haven't moved on at all.
Sorry Reiku but it is clear you have. You don't give definitions, you refer to things you haven't previously mentioned, you misreference equations. The posts I responded to were all over the shop. You're welcome to call in someone else familiar with quantum field theory, such as Guest or Cpt, and ask them whether they agree with my evaluation. I'm sure they will.
You haven't actually responded to any of my criticisms. I went through your post section by section explaining why you were mistaken, why an equation was wrong, why you've screwed up a definition. None of that you responded to. For example, you got the definition of field momentum wrong. You said L=T-U implies T+U is constant. It didn't. I asked you to explain how to go from a particular property of L to the constancy of T+U, you ignored my question.
I stand by everything I said and the fact all you can do is repeat "Nuh uh!" doesn't do anything to retort that.
Wow, do you deliberately try to misinterpret people or are you just that daft? You claim your explanations are your own understanding and wording. That's clearly not true because of how it reads as just snippets, the way you refer back to things you never mentioned. That is what I mean by passing it off as your own.
I did explain it. The fact you're now misrepresenting me in such a laughable manner says a lot, either about your honesty or your comprehension skills.
You're just not getting it are you AN?
Watch the video, I haven't botched anything up. And the order I presented that information is exactly how susskind mentions it. I didn't miss a thing when doing that, so no to rest of your idiotic assertions and accusations again.
Just like the A_x part. You said I messed that up. Well go into susskinds lecture, it is about 10 mins in. He writes it exactly the same.
Remember the time I made that Black Hole essay and you told Tach it was foolish of his aggressive attacks on the thread because he started messing things up? I'd advise you to eat some of your own cake.
Just like the other day, the total irony. You were harshly criticizing me for mixing a vector and a scalar up, when you actually messed it up yourself! Class!
Reiku:
Sorry. I mean to get back to the non-mathematical parts of your opening post, but I'm still bogged down in the maths.
That doesn't seem to define what a Lagrangian density is. You seem to be telling me something about how to use one, but not what it is.
The mass of what?
I don't understand why $$(\phi \rightarrow \phi + \epsilon)$$ indicates a symmetry? A symmetry of what? What kind of symmetry?
What is $$\dot{q}_{i}$$, then?
Aren't potentials usually functions of position? Why is $$U(q)$$ a function of a velocity?
Also, you say that the first equation is equivalent to T - U, but I see the U(q) in that equation and there's a plus sign in front of it. How does the plus sign become equivalent to a minus?
So if $$f$$ is just a number that can be set to 1, why write something like $$f(q_i)$$ when you could just write $$q_i$$?
Under which rules? You haven't mentioned any rules, have you?
What's the difference between $$L$$ and $$delta L$$?
If you can replace one by the other, why do you need both?
And what does Lorentz invariance have to do with anything?
What other kinds of momentum are there? What else can make a charge move other than a field?
What's A?
Sorry. I mean to get back to the non-mathematical parts of your opening post, but I'm still bogged down in the maths.
That doesn't seem to define what a Lagrangian density is. You seem to be telling me something about how to use one, but not what it is.
The mass of what?
I don't understand why $$(\phi \rightarrow \phi + \epsilon)$$ indicates a symmetry? A symmetry of what? What kind of symmetry?
What is $$\dot{q}_{i}$$, then?
Aren't potentials usually functions of position? Why is $$U(q)$$ a function of a velocity?
Also, you say that the first equation is equivalent to T - U, but I see the U(q) in that equation and there's a plus sign in front of it. How does the plus sign become equivalent to a minus?
So if $$f$$ is just a number that can be set to 1, why write something like $$f(q_i)$$ when you could just write $$q_i$$?
Under which rules? You haven't mentioned any rules, have you?
What's the difference between $$L$$ and $$delta L$$?
If you can replace one by the other, why do you need both?
And what does Lorentz invariance have to do with anything?
What other kinds of momentum are there? What else can make a charge move other than a field?
What's A?
''That doesn't seem to define what a Lagrangian density is. You seem to be telling me something about how to use one, but not what it is.''
It integrates over spacetime in order to compute the action. That's really all it is.
''The mass of what?''
A particle for instance.
''I don't understand why $$(\phi \rightarrow \phi + \epsilon)$$ indicates a symmetry? A symmetry of what? What kind of symmetry?''
It isn't exactly like, for instance, the kind of symmetry breaking you find in a Higgs model but it is generally the same idea. If you add a perturbation to the equations you are working with but end up with the same equation back, then there is a symmetry.
''What is $$\dot{q}_{i}$$, then?''
That is just $$\frac{\partial q_i}{\partial t}$$.
''Aren't potentials usually functions of position? Why is $$U(q)$$ a function of a velocity?''
It might have something to do with the fact the Langrangian is concerned with the kinetic energy of a moving body.
''Also, you say that the first equation is equivalent to T - U, but I see the U(q) in that equation and there's a plus sign in front of it. How does the plus sign become equivalent to a minus?''
It shouldn't be equal exactly. Sorry.
''So if $$f$$ is just a number that can be set to 1, why write something like $$f(q_i)$$ when you could just write $$q_i$$?''
The $$f$$ comes from Noethers theorem if my memory serves.
''Under which rules? You haven't mentioned any rules, have you?''
The rule of the symmetries.
''What's the difference between $$L$$ and $$\delta L$$?''
I think you already know. For instance $$\Delta t$$ reads a change in time --- so small delta is just a very small change. So it is a small change in the Langrangian.
''And what does Lorentz invariance have to do with anything?''
Ok.
''What other kinds of momentum are there? What else can make a charge move other than a field?''
There are two kinds of momentum I know about, field momentum and then linear momentum. Linear momentum is the momentum dealt with most often in the form p=Mv.
''What's A?''
That is the electromagnetic four potential, which is sometimes written as $$A_{\mu}$$.
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Sorry but you're demonstrably wrong on that, as I demonstrated.
And did you just admit that you're basically just transcribing Susskind's explanations? Couldn't you provide your own explanation rather than spewing out a load of unnecessary stuff?
I stand by what I said.
The last time you said "Susskind agrees with me" it turned out he didn't, you just didn't understand. Or the time you said Wolfe agreed with you that $$(a+ib)(a-ib) = a^{2}-b^{2} + 2abi$$.
I was pointing out that you added vectors and scalars, which you did. Rather than getting it doubly wrong you just got it wrong.Just like the other day, the total irony. You were harshly criticizing me for mixing a vector and a scalar up, when you actually messed it up yourself! Class!
I wasn't doing the algebra myself, if I had written it myself I'd have noticed such mistakes. Instead I was going through a lengthy list of your errors pertaining to all sorts of tensor problems. You wrote down fundamentally mistaken mathematics, I made a small memory slip. Quite different. And you never responded to the lengthy explanations of mine as to why you'd failed to understand the motivation behind the Dirac equation, despite you claiming to be knowledgeable in it.
You don't seem to understand that the minor memory slips I make (which everyone makes) are quite different to your fundamental misrepresentation and misunderstanding of central principles/results in things you claim to understand. Want an example? James just asked you about U(q), about how potentials are functions of position, not velocity. You just replied with "It might have something to do with the fact the Langrangian is concerned with the kinetic energy of a moving body.". Well done, you just showed you've never actually worked with such things yourself and done a problem. Potentials are always functions of position because they represent the energy a system has by virtue of its configuration. The simplest example is say radial Newtonian gravity with $$T = \frac{1}{2}m\dot{r}^{2}$$ and $$U = \frac{k}{r}$$. That'll allow someone to describe the upwards and downwards motion of a projectile. The moving part comes from T, which is a function of the time derivatives, while the way in which the kinetic behaviour changes is related to the potential. By the E-L equations you get $$m\ddot{x} = -\frac{k}{r^{2}}$$, as expected.
Quantum harmonic oscillators, Newtonian mechanics, the Dirac equation, all of them describe moving objects and the potentials are always functions of the coordinate, not its time derivative. It's something covered in any lecture course or textbook on the matter.
Now suppose I'd accidentally made a sign error in the above. It would be a small accident and not an implication I don't understand this stuff. That wouldn't then allow you to say "Look, you make mistakes too! Eat some humble pie!" because your errors are much much deeper than that. I am clearly well familiar with things like frequency, momentum, energy etc in physics so saying $$\omega$$ is a vector is an honest slip up. You failing to understand that the Dirac equation coefficients involve matrices with non-standard properties, saying $$\sqrt{a^{2}+b^{2}} = a+b$$ for numbers and not understanding what a potential is are fundamental failures of your understanding. They aren't little slip ups, the mathematical equivalent of a typo or a brain glitch, they are consistent and repeated errors.
Your attempts to excuse your own lack of understanding on things you profess to understand well enough that you try to explain them to others is either deliberate dishonest or a demonstration of how completely naive you are.
Another example of this is how you are willing to answer James's questions when you think you can get away with massive mistakes (like that potential one) but when I ask you to explain something, giving you an opportunity to step up and demonstrate some understanding, you ignore me.
You didn't actually demonstrate T+U was conserved, you incorrectly stated it was implied by something which didn't imply it. You've been talking about L=T-U, not T+U. However, there is something which indeed leads to T+U being constant from all of this. How about you tell me what that is and how you go about showing it. If you're familiar with things from quantum field theory and all the stuff you've been mentioning in this thread about symmetries and momenta and whatnot you should be aware of what I'm referring to. If instead you're just parroting Susskind then you'll be only aware of what you've heard him explicitly say, you won't have an understanding of how other things relate to this stuff or how they all fit together. This is another way of seeing a parrot compared to someone with proper understanding, they go through things in one and only one manner because they have only one source they work from. When someone gains proper understanding for themselves they can see how things fit together in different ways, in a web of implications and associations.
Come on, step up. Or are you just going to make excuses and ignore how you've shown, once again, vast gaps in your understanding.
Well, we have a site with loads of members with hearing and sight available. Maybe someone else will watch the video and compare it with what I have written because you obviously haven't.
Secondly when you gonna give it a break with the (Wolf) claim AN? That was four maybe five years ago.
Actually susskind did.
I said to the physics subforum that in physics there is a noticable difference between perpendicular and orthogonal. If you wanna keep that one going up then fine... I find it interesting that cptbork didn't even know of this definition when I spoke about it, upon which he said I was decieving everyone.
Then I linked to susskind to which someone said ''that is for pointers''.
I didn't care what it was for, it was a real definition in physics literature which susskind certainly agreed with!
Disingenuous crap.
Guest is not a physicist. Secondly, why choose two people who are completely pro-you anyway? Could you have picked any more of a biased set of individuals?
Do yourself a favor, watch the video if you are even going to throw accusations about. It seems only fair, eh?
I've just realized that what I said to James concerning why the potential depended on q isn't such a far off guess. See, the q takes on the form
$$T = \frac{1}{2}m\dot{q}^{2}$$
And all I said was the maybe it had this feature because the Langrangian is concerned with the kinetic energy of a moving body, and as AN has demosntrated, the potential energy is related to the velocity via the equation above. So my little guess wasn't completely crap.
You know what I think? I think you made a mistake and $$q_i$$ is a position rather than a velocity. What do you think?
To me, $$f_i(q)$$ looks like a functional notation. That is, $$f$$ is a function rather than a number. Could that be correct?
So $$\delta L$$ has nothing to do with variational calculus? It's just a stock-standard change in L?
From your expressions, it looks like A is a vector three-potential - especially given your integral of $$d^3 x$$ rather than $$d^4 x$$.
Anyway, I plan to move on and discuss the first part of your post...