Can a wave be spherical?
Well, probably not.
But, it is close enough.
Can a wave be spherical?
Hello, back from a long drive and dinner.
There are five glaring mistakes on page 2, which is exactly what we expect when the level of discussion is "the article used calculus"
The Five mistakes I would like to unravel are:
1) Incorrect manipulation of expressions, which ignore the postulates. Thus he stops talking about the physics of light.
2) Ignoring the rest of the Lorentz transform
3) The absurd assertion that radially propagating light also propagates along a vertical line with fixed y.
4) The misuse of multivariable calculus that asserts that just because "$$\frac{\partial x'}{\partial x} > 0$$, if x increases, then x' increased."
5) This misuse of multivariable calculus that asserts that $$\frac{\partial x'}{\partial x} > 0$$ and $$\frac{\partial x}{\partial t} > 0$$ and $$x' < 0$$ are enough to conclude that in the primed frame the light is moving toward the coordinate origin.
Correct manipulation of expressions
Given $$z = 0 \, , \; 0 < x \, , \; 0 < y \, , \; 0 < v < c $$, $$c^2 t^2 = x^2 + y^2$$ describes a two-dimensional surface. So solutions are necessarily parameterized by two independent variables.
$$t(x,y) = \frac{1}{c} \sqrt{x^2 + y^2}$$ is one possible parameterization.
$$x(\theta,t) = ct \, \cos \theta \, , \; y(\theta,t) = ct \, \sin \theta$$ is another.
$$x(y,t) = \sqrt{c^2 t^2 - y^2}$$ is another.
So when we parameterize x', t' and y' in terms of x and t, we have the related choices:
$$x'(x,y) = \left( x - v t(x,y) \right) \gamma = \frac{c x - v \sqrt{x^2 + y^2}}{c \sqrt{1 - \frac{v^2}{c^2}}} = \frac{c x - v \sqrt{x^2 + y^2}}{\sqrt{c^2 - v^2}} \\ y'(x,y) = y \\ t'(x,y) = \left( t(x,y) - \frac{v x}{c^2} \right) \gamma = \frac{\frac{1}{c} \sqrt{x^2 + y^2} - \frac{v x}{c^2}}{\sqrt{1 - \frac{v^2}{c^2}}} = \frac{c \sqrt{x^2+y^2}-v x}{c \sqrt{c^2-v^2}} $$
Partial derivatives are only partial derivatives
Now we can take partial derivatives of these expressions, remembering to do the work Mr Banks ignored:
$$ \begin{array}{rclrclrclrcl} \frac{\partial x'(x,y)}{\partial x} & = & \frac{c - \frac{v x}{\sqrt{x^2 + y^2}}}{\sqrt{c^2 - v^2}} & \frac{\partial y'(x,y)}{\partial x} & = & 0 & \frac{\partial t'(x,y)}{\partial x} & = & \frac{\frac{cx}{\sqrt{x^2 + y^2}} - v}{c \sqrt{c^2 - v^2}} & \frac{\partial t(x,y)}{\partial x} & = & \frac{x}{c\sqrt{x^2 + y^2}} \\ \frac{\partial x'(x,y)}{\partial y} & = & \frac{- v y}{\sqrt{x^2 + y^2}\sqrt{c^2 - v^2}} & \frac{\partial y'(x,y)}{\partial y} & = & 1 & \frac{\partial t'(x,y)}{\partial y} & = & \frac{y}{\sqrt{x^2 + y^2}\sqrt{c^2 - v^2}} & \frac{\partial t(x,y)}{\partial y} & = & \frac{y}{c\sqrt{x^2 + y^2}} \end{array}$$
So here we can see that even though $$\frac{\partial x'}{\partial x} > 0$$, $$\frac{\partial x'}{\partial y} < 0$$ and so the sign of $$\partial x'$$ is indeterminate unless we add a constraint on $$\partial x \, , \; \partial y$$. Mr. Banks sees to hold y constant, but then he is no longer describing the propagation of rays of light but where the expanding sphere of light meets the line $$y = y_g$$ which is akin to a searchlight beam hitting a wall and not akin to a particle. Like a spot on the wall lit up by a laser pointer, it is not constrained to move slower than light.
$$\frac{\partial x}{\partial t} = c \sqrt{1 + \frac{y^2_g}{x^2}} > c$$
Directions need more than one coordinate
Even with all the problems, does the imaginary choice move away from the new coordinate origin?
To answer this, we must take the dot product of the velocity with the position in the new coordinate system and check the sign.
$$x'(x,y) \frac{\partial x'}{\partial t'} + y'(x,y) \frac{\partial y'}{\partial t'} = x'(x,y) \frac{\partial x'}{\partial x} \frac{\partial x}{\partial t'} + y'(x,y) \frac{\partial y'}{\partial x} \frac{\partial x}{\partial t'} = c \frac{c \sqrt{x^2+y^2}-v x}{\sqrt{c^2-v^2}} $$ which is always greater than zero, indicating that even in the bad physics, Mr. Banks has also erred when "the article used calculus."
A better way
Because of the conservation of angular momentum, we should use a better parameterization to see the fate of actual rays of light. $$x(\theta,t) = ct \, \cos \theta \, , \; y(\theta,t) = ct \, \sin \theta$$ is natural.
So when we parameterize x', t' and y' in terms of theta and t, we have the related choices:
$$x'(\theta,t) = \left( x(\theta,t) - v t \right) \gamma = \frac{c \, \cos \theta - v}{\sqrt{1 - \frac{v^2}{c^2}}} t \\ y'(\theta,t) = y(\theta,t) = ct \, \sin \theta \\ t'(\theta,t) = \left( t - \frac{v x(\theta,t)}{c^2} \right) \gamma = \frac{1 - \frac{v}{c} \, \cos \theta }{\sqrt{1 - \frac{v^2}{c^2}}} t $$
$$ \begin{array}{rclrclrclrclrcl} \frac{\partial x'(\theta,t)}{\partial \theta} & = & \frac{-c \, \sin \theta }{\sqrt{1 - \frac{v^2}{c^2}}} t & \frac{\partial y'(\theta,t)}{\partial \theta} & = & ct \, \cos \theta & \frac{\partial t'(\theta,t)}{\partial \theta} & = & \frac{\frac{v}{c} \, \sin \theta }{\sqrt{1 - \frac{v^2}{c^2}}} t & \frac{\partial x(\theta,t)}{\partial \theta} & = & - c t \, \sin \theta & \frac{\partial y(\theta,t)}{\partial \theta} & = & c t \, \cos \theta \\ \frac{\partial x'(\theta,t)}{\partial t} & = & \frac{c \, \cos \theta - v}{\sqrt{1 - \frac{v^2}{c^2}}} & \frac{\partial y'(\theta,t)}{\partial t} & = & c \sin \theta & \frac{\partial t'(\theta,t)}{\partial t} & = & \frac{1 - \frac{v}{c} \, \cos \theta }{\sqrt{1 - \frac{v^2}{c^2}}} & \frac{\partial x(\theta,t)}{\partial t} & = & c \, \cos \theta & \frac{\partial y(\theta,t)}{\partial t} & = & c \, \sin \theta \end{array}$$
So how fast is light moving in the unprimed frame (holding theta constant)?
$$\sqrt{\left( \frac{\partial x}{\partial t} \right)^2 + \left( \frac{\partial y}{\partial t} \right)^2} = c$$
And in the unprimed frame?
$$\sqrt{\left( \frac{\partial x'}{\partial t'} \right)^2 + \left( \frac{\partial y'}{\partial t'} \right)^2} = \sqrt{\left( \frac{\partial x'}{\partial t} \frac{\partial t}{\partial t'} \right)^2 + \left( \frac{\partial y'}{\partial t} \frac{\partial t}{\partial t'} \right)^2} = \sqrt{\left( \frac{c \, \cos \theta - v}{1 - \frac{v}{c} \, \cos \theta } \right)^2 + \left( c \sin \theta \frac{\sqrt{1 - \frac{v^2}{c^2}}}{1 - \frac{v}{c} \, \cos \theta } \right)^2} = c$$
So is the light moving towards the origin in the primed frame?
$$\left( \frac{c \, \cos \theta - v}{\sqrt{1 - \frac{v^2}{c^2}}} t \right) \left( \frac{c \, \cos \theta - v}{1 - \frac{v}{c} \, \cos \theta } \right) + \left( ct \, \sin \theta \right) \left( c \sin \theta \frac{\sqrt{1 - \frac{v^2}{c^2}}}{1 - \frac{v}{c} \, \cos \theta } \right) = \frac{c^2 t (v-c \cos \theta)^2}{\sqrt{c^2-v^2} (c-v \cos \theta)} + \frac{c^2 t \sqrt{c^2 - v^2} \sin^2 \theta}{c - v \cos \theta} = \frac{c^2 t (c-v \cos \theta)}{\sqrt{c^2-v^2}} > 0$$
Of course not. Only someone without the ability to understand special relativity would think so. Only someone who doesn't understand calculus would calculate so.
3) The absurd assertion that radially propagating light also propagates along a vertical line with fixed y.
Directions need more than one coordinate
Pseudoscience is where this belongs.
A load of crap by a couple of cranks.
rpenner refuted it quite nicely.
Simply ignore experiment and observation in favor of your misapplication of calculus.
There is no point in continuing to argue with you, because you ignore reality.
To defend SR, you will need to prove calculus is false.
The calculus is not applied correctly. If it was it would agree with actual measurements, and it doesn't.chinglu said:The calculus is applied correctly. Otherwise prove it is applied incorrectly.
To defend SR, we simply look at experiment, observation and application.
Reality trumps you.
The calculus is not applied correctly. If it was it would agree with actual measurements, and it doesn't.
Prove that calculus can show that actual measurements are all wrong, go on.
It's like saying you can prove that petrol isn't a fuel that powers internal combustion in an engine. Or that birds don't fly due to aerodynamic principles, but some other (mathematical) reason.
Or say, that light doesn't propagate through space due to an electromagnetic principle, which has been established, and accepted as an explanation that works, for well over a century.
It's just dumb, end of story.
No it does not.
Math and calculus wins.
You sound like a religious bigot that hates math and calculus results.
Not what I said - you're being dishonest.I agree
We're talking about corrections applied to the satelite, not the receiver. Try again, try harder (actually, I'll settle for you just trying at this point).I disagree.
The corrections which are made are described here: Global Positioning System, Correcting a GPS receiver clock
Any idiot can claim they can use calculus to prove that measurements are wrong, I see you have no idea how to do that.chinglue said:Any idiot can prove a misapplication or error.
I see you cannot do that. LOL
Only an idiot thinks that reality doesn't matter.
Cranks like to ignore reality.
They live in a universe of their own.
Any idiot can claim they can use calculus to prove that measurements are wrong, I see you have no idea how to do that.
What's that stuck on your chin, btw?