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Messages - PhysBang

Pages: [1]
1
General Science / Re: Does the end of my ruler travel faster than the speed of light ?
« on: 08/05/2017 13:32:48 »
First I would suggest that you think about the energy required to move that ruler.

But we can disregard that. You are assuming that the ruler is infinitely rigid. It's not. One of the consequences of Special Relativity is that there is an upper limit to rigidity. Your ruler will bend significantly.
The following users thanked this post: neilep

2
New Theories / Re: Is heterogenics is the sole purpose of sex?
« on: 20/04/2017 21:15:08 »
Quote from: the5thforce on 20/04/2017 20:42:28
Quote from: PhysBang on 19/04/2017 20:21:06
Quote from: the5thforce on 19/04/2017 18:53:18
Are you denying that women are capable of orgasm during sex?
Nope, just denying that you provided an answer to the question asked.
Quote
Theres no other reason for clitoral bulbs to exist aside from clitoral mechanics enabling penetrative clitoral motion, its a matter of persuasion and practice which includes all forms of stimulation
So says you. Without any evidence. Or argument.

There are endless demonstrations of clitoral mechanics in high definition online, I encourage you to research in the name of science..

Moderator please remove the 'is' you added to my thread title
You are, unsurprisingly, dodging the real point: you have no citations, evidence, or arguments to support your claim about the purpose of sex or its value.
The following users thanked this post: atrox, smart

3
New Theories / Re: Is heterogenics is the sole purpose of sex?
« on: 19/04/2017 12:23:18 »
Quote from: the5thforce on 19/04/2017 03:54:26
Quote from: Kryptid on 19/04/2017 03:26:49
Can you explain what "heterogenics" means?

Heterosexual natural selection
So the answer to Kryptid's question was, "No, I can't explain."
The following users thanked this post: smart

4
New Theories / Re: What are the economics of sexual orientation?
« on: 16/04/2017 14:33:06 »
Quote from: the5thforce on 16/04/2017 08:30:08
Gays can never kiss face to face during climax,
That is not even close to true. You clearly have a very limited knowledge of sex and a very limited imagination.
Quote
in the multiverse everyone tends to be straight,
There is little evidence that there is more than one universe and there is clearly no sociological data on any planet other than Earth, so this claim is baseless.
Quote
all sperm start heterosexual, relationship openness is a spectrum...
Sperm do not have neurons or anything else that could instantiate desire or other cognitive functions, so they cannot possibly have a sexual orientation.

What we clearly have evidence for is that the5thforce is a bigot with very little in the way of education or intellectual ability. The latter failures are acceptable but the first is not.
The following users thanked this post: smart, Demolitiondaley

5
Physics, Astronomy & Cosmology / Re: Is the estimated age of the Universe absolute, or relative?
« on: 06/04/2017 20:06:09 »
Two quick notes:

First, if we look at recession velocities in the recent cosmological past, we find that things farther away are receding faster the farther away they are. But we do not see this happen in a linear fashion the farthest away that we can observe. Scientists use the specific way that recession velocity relates to distance to measure many different parameters of the universe. It is not the case that we are looking all the way back to the early universe and just seeing things move faster in the early history of the universe.

Second, that the universe may have begun with a singularity does not mean that the universe has or had a center. Even infinitely large spaces can collapse into a singularity and singularities can open in to infinitely large spaces (the temporal reverse of the first procedure).

The following users thanked this post: jeffreyH

6
New Theories / Re: Is the Lorentz contraction physical or just visual?
« on: 26/11/2016 16:34:06 »
Quote from: GoC on 26/11/2016 13:18:02
For all of you who accept mathematics over mechanism shame on you.
So, shame on Isaac Newton then?
The following users thanked this post: jeffreyH

7
New Theories / Re: Is the Lorentz contraction physical or just visual?
« on: 20/11/2016 15:06:58 »
J S Bell produced a very nice derivation of length contraction given movement relying on Maxwell's electromagnetism.

Harvey Brown wrote a nice paper about the derivation and its pros and cons. http://cds.cern.ch/record/396878/files/9908048.pdf
The following users thanked this post: jeffreyH, GoC

8
New Theories / Re: Is the Lorentz contraction physical or just visual?
« on: 19/11/2016 23:48:05 »
Quote from: GoC on 14/11/2016 12:19:04
Quote
This is not a trivial question. The answer has significant implications. Time dilation is a definite physical effect and has been confirmed experimentally. It may not be possible to confirm Lorentz contraction in the same way. It is then only via close examination of the mathematics of relativity that an insight can be gained.

Exactly! While there is no mechanical reason for contraction there is mathematics that show image contraction.
Except that there is mechanical reason for contraction and there is evidence for contraction, i.e., if there was no contraction, one could not have time dilation, since one could not have a consistent theory.
The following users thanked this post: Alex Dullius Siqueira

9
New Theories / Re: Why does a mass in motion tend to move in a straight line at constant velocity?
« on: 19/08/2016 22:14:52 »
Why do you assume that not moving is a natural state? How do you distinguish between what is moving and what isn't moving?
The following users thanked this post: jeffreyH

10
Physics, Astronomy & Cosmology / Re: Frames of Reference and Proper Time
« on: 16/08/2016 13:00:59 »
You are giving, roughly, the definition of proper time. As long as that "observer" only has inertial motion, then this is OK for Special Relativity.
The following users thanked this post: jeffreyH, TyroJack

11
New Theories / Re: Can a preferred frame of reference be identified?
« on: 14/08/2016 21:43:17 »
I'll see when I have enough time. I'm sorry that you have learning problems, but not sorry that you're a real ____.

In the end, you are a crank, so there is not much I can do to help you. I wish you the best of luck and I hope you don't waste too much time with your education website. And I really hope you have some support system to pay for your needs.
The following users thanked this post: David Cooper

12
New Theories / Re: Can a preferred frame of reference be identified?
« on: 14/08/2016 17:35:09 »
OK, so we start with a reference frame, A, that we will take to be at rest.

We will then imagine a reference frame , A', moving to the NE of our original reference frame at a speed of 0.866 of the speed of light. (We will just use units adjusted so that the speed of light in a frame is 1 in our units).

Let's make this a unit square, so that the SW corner of the square rests at the origin of A'. This means that the SW corner of the square is at A'(t,0,0) for all values of t. For al corners:

SW A'(t,0,0)
NE A'(t,1,1)
NW A'(t,0,1)
SE A'(t,1,0)

Let's make things easy for ourselves and arrange frames A and A' so that the SW corner of our square passes through A(0,0,0) as the square moves through A.

Then we have to ask where the other points of the square lie?

For ease of reference, I have used the boost matrix formulation available at wikipedia. https://en.wikipedia.org/wiki/Lorentz_transformation#Boost_matrix

Our velocity is 0.866, but we have to adjust this based on our angle of motion. We can do this by multiplying by the normals in each direction, n_x=0.707 and n_y = 0.707. Our gamma remains 2. (Please note that I am using reduced significant digits in this presentation.)

This means that to translate a position from A to A':
t'=2t + (-2)(0.866)(0.707)x + (-2)(0.866)(0.707)y
x'=(-2)(0.866)(0.707)t + (1 +(2-1)(0.707)^2)x + (2-1)(0.707)(0.707)y
y'=-2(0.866)(0.707)t  + (2-1)(0.707)(0.707)x + (1 +(2-1)(0.707)^2)y

To get the inverse, we have to essential run a translation at the same speed in the opposite direction. This means flipping the sign on the normals for each direction.

This means that to translate a position from A' to A:
t=2t' + (-2)(0.866)(-0.707)x' + (-2)(0.866)(-0.707)y'
x=(-2)(0.866)(-0.707)t' + (1 +(2-1)(-0.707)^2)x' + (2-1)(-0.707)(-0.707)y'
y=-2(0.866)(-0.707)t'  + (2-1)(-0.707)(-0.707)x' + (1 +(2-1)(-0.707)^2)y'

So let's look at the unit square at time A'(t=0):
SW A'(0,0,0)
NE A'(0,1,1)
NW A'(0,0,1)
SE A'(0,1,0)

Translated to frame A:
SW A(0,0,0)
NE A(2.45,2,2)
NW A(1.22,0.5,1.5)
SE A(1.22,1.5,0.5)

We see here a problem for determining the shape of our square in frame A: our points are now at different times! This isn't much of a problem, because we know that the parts of the square are all moving at a constant rate relative to frame A. We just have to trace their path back.

This means looking at delta(t) and then figuring out the change in each coordinate and applying that (taking a negative value of delta(t) to go backwards in time). So:
delta(x) = delta(t)(v)n_x = delta(t)(-0.866)(0.707)
delta(y) = delta(t)(v)n_y = delta(t)(-0.866)(0.707)

So, looking back, we can find all the points of the square at A(t=0):
SW A(0,0,0)
NE A(0,0.5,0.5)
NW A(0,-0.25,0.75)
SE A(0,0.75,-0.25)

This gives us a nice rhombus shape, with a distance between NW and SE of sqrt(2), which is what we expect and a distance between SW and NE of 0.707, which is also what we expect from length contraction.

So what if we imagine that this square was hovering over rails? Does the distortion of the box mean that it goes over the rails?

Well, since the box was literally placed over the rails, then we should expect the rails to be in exactly the same place under the box: they undergo the same translations!

These tracks are 1 unit apart in A', but only 0.707 units apart in frame A, which we know because of length contraction. The tracks run W-E where they are at rest, but they are at rest in A', which means that they are moving NE in A.

This also means that the tracks are farther north the farther east one goes and are farther south the farther west one goes. This is a product of the relativity of simultaneity: where each frame assigns the track to be at different times. It depends on when frame A assigns the track to cross certain points. In A', we have a track sitting still, running W to E, but in A we have a track moving NE, oriented NW to SE.

But let's move the box along, say 10 units in frame A. Then the x position and the y position of every point changes by 10(0.866)(0.707)=6.123 and the t of every point becomes 10.

Now we're looking at these points:
SW A(10,6.123,6.123)
NE A(10,6.623,6.623)
NW A(10,5.873,6.873)
SE A(10,6.873,5.873)

Since the rail is moving along with the square, the square stays nicely with the rail. But can we translate back?

Here are the translated positions (3 significant figures):
SW A'(5,0,0)
NE A'(3.78,1,1)
NW A'(4.39,0,1)
SE A'(4.39,1,0)

As we can see, these are all points on the unit square in Frame A', which means that they are points on the rail.

Let's imagine a rail stationary in frame A, over which the square (rhombus) is moving, touching at the NW and SE corners. This means that the rail runs SW to NE, is sqrt(2) wide and one rail passes through A(0,-0.25,0.75) and the other through A(0,0.75,-0.25).

We already know that the square stays on this track in frame A', since the exact same translations that we used above for the other track apply for this track on the corner.

I think that's enough for now.
The following users thanked this post: David Cooper

13
Physics, Astronomy & Cosmology / Re: Why does light take billions of years to cross the Universe?
« on: 13/08/2016 19:21:43 »
Quote from: Blame on 13/08/2016 14:58:41
Quote from: PmbPhy on 13/08/2016 13:59:40

You're quite wrong on the size of the visible universe. The diameter of the visible universe is 93 billion light years.

How did you get that figure? The universe is something like 14 billion years old (assuming the big bang theory is right) so light can only at best have traveled 14 billion light years. Call that a radius and you get a diameter of something like 28 Billion light years.

The universe has been expanding quite a bit over those 14 billion years.
The following users thanked this post: PmbPhy

14
Physics, Astronomy & Cosmology / Re: could expansion of the universe be a relaxation of the vacuum?
« on: 28/07/2016 19:04:06 »
The idea is wrong because if the vacuum has a density, then that is dark energy.

Whether or not there has been a change in the energy density associated with the vacuum is an open question. Current cosmological projects are attempting to measure possible change in vacuum energy density.
The following users thanked this post: jeffreyH

15
That CAN'T be true! / Re: How does darkness enter my eyes so I can ''see'' it?
« on: 05/07/2016 16:48:50 »
Quote from: Thebox on 05/07/2016 14:12:08
Yes I agree you see areas that are less illuminated, but these areas are quite clearly and measurable to be in their exact geometrical position. These areas are not inside our brain, to see and to ''see'' is not what you are seeing.
Everything that you see is inside your brain. Your visual field is a construction of your brain. Many, many times, our brains do not properly represent the world around us.
The following users thanked this post: Alex Dullius Siqueira

16
Physics, Astronomy & Cosmology / Re: What is the basis of the twin paradox and general relativity?
« on: 01/07/2016 16:35:30 »
Quote from: jeffreyH on 20/06/2016 08:28:40
Two twins on earth measure the expansion of the universe and determine the redshift of light for selected galaxies. Then one twin goes on a space flight at close to the speed of light to a distant planet. Both twins carry on measurements of their selected galaxies. While the earthbound twin gets the predicted results the journeying twin finds the galaxies redshifted directly behind and blue shifted in front. From this he can determine he is in motion. Therefore both twins can determine who will be time dilated and age more slowly. Thus when they meet up again they won't be surprised at the age difference. No paradox.
This doesn't work because the Earth is in motion relative to the CMB average, but the twin scenario still works.

The "answer" to the is non-paradox is that the situation is not symmetric. The one twin does not have one inertial reference frame; this is required for the twin to turn around and come back.
The following users thanked this post: jeffreyH

17
Physics, Astronomy & Cosmology / Re: Does gravity attract masses in space, or does it curve space between them?
« on: 01/07/2016 16:32:08 »
Quote from: Alan McDougall on 30/06/2016 13:40:41
What is causing them to drift toward each other a force or the bending of space or both?
One can describe spacetime in such a way that the objects, at rest, just approach each other with no force on the objects. This is part of general relativity.
The following users thanked this post: jeffreyH

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