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Author Topic:   The Twins Paradox and the speed of light
NoNukes
Inactive Member


Message 138 of 230 (628867)
08-13-2011 2:01 PM
Reply to: Message 136 by Maartenn100
08-13-2011 12:31 PM


Not so fast...
So these timedilations will cancel eachother out, I think. The accelerating astronaut will not be younger than its twin brother on Earth. Because the other brother at home will move too in the gravitational field. There is no paradox. (I think)
The time dilation effects that result from high speed velocity (significant fraction of c) dwarf those that result from differences in potential in earth's gravitational field. In a typical twin paradox problem, the rocketing twin's speed produces a gamma of 1.5 or more in order to yield an impressive result. The twin paradox is not a gravitational effect. It can be explained strictly with special relativity.
The acceleration by one twin when turning around to come home, which is not experienced by the other twin, does introduce an asymmetry in the experience of the twins, but it does not produce any significant time dilation effect per se.
Also consider that the famous mu-meson experiment is a real life validation of the twin paradox result.
By the way, your English is just fine.
Edited by NoNukes, : English remark

This message is a reply to:
 Message 136 by Maartenn100, posted 08-13-2011 12:31 PM Maartenn100 has replied

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NoNukes
Inactive Member


(1)
Message 145 of 230 (628894)
08-13-2011 7:55 PM
Reply to: Message 144 by Maartenn100
08-13-2011 6:40 PM


When you leave your twinsister on Earth she begins to rotate first from your point of view (rotation Earth), then to wobble with a moon, then to start speeding up around the sun. This happens while you are accelerating away from her.
Looks like my first post made no impression.
Do you know the magnitude of the dilation effects you are describing? They are all extremely small. You'd never detect any difference in the life span of a human due to either gravitational time shift or the accelerating away from earth.
For example, the gravitational frequency shift at earth's surface compared to that an infinite distance from earth is about one part in 10^9. Maybe if a neutron star or black hole is involved you can generate gravitational twin paradox worth discussing. But not from flitting about the solar system.
The effect to be concerned about here is time dilation due to the relative motion resulting from the acceleration.
Edited by NoNukes, : No reason given.

This message is a reply to:
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NoNukes
Inactive Member


Message 149 of 230 (628931)
08-14-2011 12:14 PM
Reply to: Message 148 by Maartenn100
08-14-2011 8:43 AM


Re: gravitational theory of relativity
g0 = a = Fb
g0 = relative observed centripetal acceleration of the body from "outside the gravitational system frame of reference".
Fb = actual Newtonian gravitational force on the body of the graviational system.
a = acceleration of the body from the body 'frame of reference (lineair)
Some of the quantities you claim are equal (Force and acceleration) do not even have the same units of measurements. So something is definitely wrong with your "math".
Please don't take my comments as encouragement to continue along these lines. But before guessing that some gravity effect is "missing" with respect to relativity, you should at least understand general relativity. So far you have not claimed to have such knowledge and your "hypothesis" does not suggest that you have such knowledge.
For example, we know from actual measurement that GPS satellites experience exactly the relativistic effect predicted by GR/SR, said effect amounting to 45 microseconds/day of time dilation.

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NoNukes
Inactive Member


(1)
Message 176 of 230 (629115)
08-15-2011 10:43 PM
Reply to: Message 174 by Maartenn100
08-15-2011 5:53 PM


Re: gravitational theory of relativity
Euhm, are you from another world?
When you are leaving Earth and you are above Earth. Do you see the Earth rotation yes or no?
That's movement.
Perhaps you should investigate cavediver's credentials before deigning to lecture him on relativity.
We observe the earth to rotate while we are still standing on the ground. Surely you've noticed that that bright yellow/white thing that seems to rise towards the east and set towards the west? That rising/setting effect is due to earth's rotation. You seem to be making a mistake I've seen before. Namely that relativity is an optical illusion of some kind.
But maybe you are right on the twins: gravity is negliblible.
I want to learn more about that!!!!
The gravity/acceleration time dilation effects are negligible. Period. Outside of GPS were extremely high time accuracy is required, it is difficult to come up with any serious applications for the masses that apply general relativity.
Nobody even gives enough detail in twin paradox problems to even calculate the gravitational time dilation effects.
Let me suggest that you are going about learning in the wrong way. It's certainly reasonable to have your own ideas about stuff, but when you know as little about the topic as you do, surely it as at least equally likely that you are wrong as it is that the so called experts are wrong. A little less hubris might be in order. Check the color of the sky on your own world before asking whether Einstein was an idiot.
That seems a contradiction to me. "It's not relativistic at all, it's x - Relativity."
But it is not a contradiction. You simply aren't familiar with the language of physics. Non-relativistic simply means slow moving, low gravity physics such that Special and General Relativity are not needed for calculations. But the concepts of relative motion and inertial reference frames are from physics according to Newton and Galileo. Relative motion is not unique to SR/GR.
Edited by NoNukes, : No reason given.

This message is a reply to:
 Message 174 by Maartenn100, posted 08-15-2011 5:53 PM Maartenn100 has not replied

  
NoNukes
Inactive Member


Message 179 of 230 (629958)
08-21-2011 1:00 PM
Reply to: Message 178 by Maartenn100
08-16-2011 11:15 AM


Re: gravitational theory of relativity
When Earth rotates "in reality", it doesn’t only do this around it’s axis, but also with a moon, a sun etc. And in that case ‘the corioliseffect’ would be very different.
The first indication that you are on the wrong track is when you claim that current physics is all wrong. The coriolis effect is perfectly well explained using Newtonian mechanics. If you think the coriolis effect would be 'very different' using your science, then your science is wrong.

This message is a reply to:
 Message 178 by Maartenn100, posted 08-16-2011 11:15 AM Maartenn100 has replied

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 Message 180 by Maartenn100, posted 08-21-2011 5:05 PM NoNukes has replied

  
NoNukes
Inactive Member


Message 181 of 230 (629986)
08-21-2011 7:25 PM
Reply to: Message 180 by Maartenn100
08-21-2011 5:05 PM


Re: gravitational theory of relativity
And I do not claim that it's science.
Good.
Hubble discovered that all starclusters are redshifting, from your point of view. Wherever you are, you will see everything redshifting at the bounderies of space and time-measurement form your point of view.
Why doesn' you see it between Earth and the moon? Or Earth and Mars?
Easily answered.
First, the red shift produced by the expansion of space is extremely tiny on the scale of the solar system. Taking the Hubble constant to be 70 (km/s)/Mpc and the distance from Earth and Mars to be about 2.6 AU which is approximately the maximum separation between the two planets, gives a velocity on the order of 10^-9 km/second for the rate of expansion of space between Earth and Mars. That rate of expansion would produce an undetectable amount of red shift.
Of course even that tiny expansion of space does not translate into the Earth and Mars moving apart because:
The earth and moon, and the entire solar system are bound together by gravity, so that the separation between them is not directly affected by the expansion of space within the solar system. It's as if the earth and mars were connected together by relatively strong springs. The springs would oppose a an expansion force attempting to separate earth and mars. The expansion of space would not result in a velocity between earth and mars, but would instead produce an extremely tiny and undetectable increased between the planets. So there would actually be no expansion based redshift between earth and mars at all.
Finally, earth and mars, due to their orbital motions have their own relative motions sometimes towards each other and sometimes away. In fact galaxies also have proper motions relative to each other. Some galaxies are moving towards us and exhibit blue shift rather than red shift. So it is not even true that all star clusters are red shifting.

This message is a reply to:
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NoNukes
Inactive Member


Message 184 of 230 (680071)
11-17-2012 1:46 PM
Reply to: Message 183 by Bolder-dash
11-17-2012 12:57 PM


Two tickets to paradox
Special relativity says nothing about acceleration or deceleration, but is simply concerned with the speed of the reference frame.
The above analysis not correct. An inertial reference frame is a frame in which there is no acceleration. This means that neither speed nor the direction associated with the speed can change. The forms of the time dilation and length contraction equation that everyone is used to using assume inertial reference frames. Special relativity can be used to handle accelerated frames, but the analysis is a bit difficult. In essence, the apparent paradox results from taking a short cut with the analysis from the view point of traveling twin.
The itineraries of the stay at home twin and the traveling twin are not symmetric. While the stay at home twin travels at constant velocity as measured any inertial reference frame, there is no single inertial reference frame from which the same can be said for the traveling twin. This is true regardless of whether the traveling twin moves in a circle at constant speed or travels out to a point and returns along a straight line path.
There is an explanation on this board from either cavediver or Son Goku in which the two paths are drawn on a space time diagram. I'd recommend looking up that diagram and the associated explanation.
Edited by NoNukes, : No reason given.
Edited by NoNukes, : No reason given.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 183 by Bolder-dash, posted 11-17-2012 12:57 PM Bolder-dash has not replied

  
NoNukes
Inactive Member


Message 185 of 230 (680098)
11-17-2012 3:54 PM
Reply to: Message 183 by Bolder-dash
11-17-2012 12:57 PM


Twin paradox space time diagram
The link below gives an explanation of the twin paradox and provides a space-time diagram of the relevant events from the perspective of the stationary twin and the traveling twin. The role of acceleration in explaining the distinction between the two views is explained.
http://www.csicop.org/si/show/twin_paradox
Added by edit:
Yet another explanation.
Twin Paradox (from Einstein Light: relativity in film clips and animations)
Edited by NoNukes, : No reason given.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 183 by Bolder-dash, posted 11-17-2012 12:57 PM Bolder-dash has replied

Replies to this message:
 Message 186 by Bolder-dash, posted 11-18-2012 4:19 AM NoNukes has replied
 Message 188 by Bolder-dash, posted 11-18-2012 5:18 AM NoNukes has replied

  
NoNukes
Inactive Member


Message 194 of 230 (680174)
11-18-2012 9:22 AM
Reply to: Message 188 by Bolder-dash
11-18-2012 5:18 AM


Re: Twin paradox space time diagram
In reviewing what.you posted, I note that your original reference more than adequately explains the twin paradox.
At this point, I think you should take on some of the effort in understanding. Try drawing the space time drawings for the scenario you want to examine.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 188 by Bolder-dash, posted 11-18-2012 5:18 AM Bolder-dash has not replied

  
NoNukes
Inactive Member


(1)
Message 195 of 230 (680177)
11-18-2012 9:44 AM
Reply to: Message 186 by Bolder-dash
11-18-2012 4:19 AM


Re: Twin paradox space time diagram
Why in my example can only one experience g force?
The twin that fires his retro rockets will feel the acceleration. The other twin will not. How could this be otherwise? Surely that should be enough to show you that acceleration is not "relative"

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 186 by Bolder-dash, posted 11-18-2012 4:19 AM Bolder-dash has replied

Replies to this message:
 Message 196 by Bolder-dash, posted 11-18-2012 10:21 AM NoNukes has seen this message but not replied

  
NoNukes
Inactive Member


Message 209 of 230 (680226)
11-18-2012 3:44 PM
Reply to: Message 203 by Bolder-dash
11-18-2012 12:04 PM


Re: Twin paradox space time diagram
Here is a simple way to answer the question plot the distance from the starting point vs time for both travelers on a space time graph. The maximum duration possible is along a horizontal path between events. That is the path traveled by the stay at home twin. Any path deviating from that will show a smaller duration.
1. Path is approximately an isoceles triangle. Duration is less than for stay at home twin. Let's assume that twin is not squished into jelly.
2. Path consists of curved sections rather than straight lines. Duration is less than stay at home twin.
3. Yes. But if we want to ask questions about ages, we will have difficulty specifying a time for a comparison because the participabts will disagree about whether given events are simultaneous.
ABE:
The convention space time graph has time along the vertical axis. I don't think it changes anything other than to say that the maximum duration between two events would be a vertical line which is the path for the stay at home twin.
End of ABE
I will make them numbers, since you are not as good with letters
Uncalled for. It's no big deal not to understand this stuff or to fail to follow the explanations. No need to lash out at people who do understand. Do you truly understand physics well enough so that your intuition that something makes no sense is something to be trusted? I know that such is not the case for me.
You are right about one thing, Einstein did publish a paper in the late 1910s in which he made remarks about the twins paradox that are now known to be incorrect. But what of it? Is there any doubt now that the twin paradox is based on actual and observed physics? If so perhaps we can address your concerns by pointing to experimental evidence.
Edited by NoNukes, : Address unconventional nature of my proposed space-time plot.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 203 by Bolder-dash, posted 11-18-2012 12:04 PM Bolder-dash has not replied

Replies to this message:
 Message 210 by cavediver, posted 11-18-2012 6:46 PM NoNukes has replied

  
NoNukes
Inactive Member


Message 211 of 230 (680249)
11-18-2012 8:30 PM
Reply to: Message 210 by cavediver
11-18-2012 6:46 PM


Re: Twin paradox space time diagram
The best I can do is a reference to Journal Article called "Einstein and the twin paradox" which describes an attempt in 1918 to explain the twin paradox using GR and the equivalence principle and focusing on the region of acceleration as the cause of the time dilation. I believe it is easy to show that for the linear ingoing/outgoing case this won't work because we can use the same acceleration region for various voyage lengths.
Below is a google docs link to the article. See pp 587-588
https://docs.google.com/viewer?a=v&q=cache:56ZgKAyYYE4J:f...
Of course the article makes clear that Einstein did understand the paradox despite making errors at times.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 210 by cavediver, posted 11-18-2012 6:46 PM cavediver has replied

Replies to this message:
 Message 212 by cavediver, posted 11-19-2012 7:29 AM NoNukes has replied

  
NoNukes
Inactive Member


Message 213 of 230 (680359)
11-19-2012 8:56 AM
Reply to: Message 212 by cavediver
11-19-2012 7:29 AM


Re: Twin paradox space time diagram
Hmmm, I'm intrigued - though I certainly think you are wrong, because Einstein's explanation is a wonderful example of the equivalence principle in full flight. But by all means present your thoughts and we can have a look.
If the story in the article is correct, Einstein appears to have acknowledged the error. In reading up on this, I've seen others indicate that Einstein's formulation was in error as well. But at least one of those others was hawking his own Mach principle explanation, so perhaps there is some doubt.
This link below includes a critique of Einstein's 1918 position
LKB | Laboratoire Kastler Brossel - ENS - Sorbonne Universit - Collge de France
quote:
His resolution involving pseudo-gravitational time dilation, inspired by the equivalence principle and general relativity crucially relies on uninterrupted running of the clocks during accelerations, and this requirement makes the Einstein resolution is 1918 ineffective, because clocks can be stopped and restarted, and the result on time dilation is not significantly changed
In any event, I have no doubt that there is a GR method of resolving the paradox. But Einstein has been quoted as saying at one point that there was no resolution of the twin paradox within Special Relativity. That at least indicates muddled thinking on the subject.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 212 by cavediver, posted 11-19-2012 7:29 AM cavediver has replied

Replies to this message:
 Message 214 by cavediver, posted 11-19-2012 12:31 PM NoNukes has replied

  
NoNukes
Inactive Member


Message 217 of 230 (680533)
11-19-2012 8:41 PM
Reply to: Message 214 by cavediver
11-19-2012 12:31 PM


Re: Twin paradox space time diagram
quote:
There is no resolution of the twin paradox within Special Relativity
cavediver writes:
And in terms of the twin paradox within our Universe, this is certainly true.
I don't understand what you mean here. Haven't you and I both been discussing resolutions of the twin paradox using strictly Special Relativity?

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 214 by cavediver, posted 11-19-2012 12:31 PM cavediver has replied

Replies to this message:
 Message 218 by cavediver, posted 11-20-2012 3:52 AM NoNukes has replied

  
NoNukes
Inactive Member


Message 219 of 230 (680586)
11-20-2012 9:03 AM
Reply to: Message 218 by cavediver
11-20-2012 3:52 AM


Re: Twin paradox space time diagram
But we live in a GR universe
I understand that, but I think we are talking past each other.
My understanding of Einstein's 1918 GR position (which admittedly is based on a description by a detractor) is that Einstein's analysis was conducted by using the equivalence principle during the small portion of the trip in which the ship was accelerating. I just don't see how that can be a correct resolution of the paradox, because the acceleration period would be the same regardless of the length of the voyage. Yet, any time dilation due to the acceleration must end once the acceleraton ends.
I understand that there is a completely GR based resolution of the twin paradox. After all GR subsumes SR and can also account for the acceleration period which we basically ignore when doing a back of the envelope calculation. But the twin paradox itself is a pure SR postulation in which the acceleration period is set up to be a vanishingly small portion of the trip.
If you make an accelerated trip out towards alpha C, you will experience the "gravitational field" of the acceleration
I know, but what if the acceleration is only at the start, middle and end of the trip. Can the twin paradox be resolved by simply using the equivalence principle during those portions? I think that is what is being alleged in the criticism in that time-wasting article I pointed you to.
-----------------------------------
But I'd really rather talk about the implications of this article if it is on topic.
Particle physicists confirm arrow of time for B mesons

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
The apathy of the people is enough to make every statue leap from its pedestal and hasten the resurrection of the dead. William Lloyd Garrison.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 218 by cavediver, posted 11-20-2012 3:52 AM cavediver has replied

Replies to this message:
 Message 220 by cavediver, posted 11-20-2012 10:02 AM NoNukes has replied

  
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