Go Back   Physics Help Forum > Physics Forums > Physics

Physics Physics Forum - General Physics Discussion and Physics News

Like Tree3Likes
Closed Thread
 
LinkBack Thread Tools Display Modes
Old Aug 13th 2017, 03:25 AM   #21
Member
 
Join Date: Jul 2015
Posts: 84
Originally Posted by Pmb View Post
You should be more careful in what you're reading since I never said anything of the kind directly to you. I was referring to studiot's comment.
Then why did you put your criticism in your reply to my post and not in a reply to studiot's?


Originally Posted by Pmb View Post
Observers in different frames of reference measure different things. In the example I gave a baseball had a speed of 100 m/s as measured by one observer an a speed of zero as measured by another observer..
The crux of the matter is that relativists seem to assume observers lives in separate universes. In contrast, nonrelativists experience the same universe, so a baseball can only have one real speed but lots of relative speeds. Everyone keeps ignoring my reply to Woody when I said x>y' and x'<y, i.e. relativists assume there are different worlds and that they are all equally real. Why will relativists not confirm their rejection of a single reality and provide experimental proof of their multiple realities? This seems to be another unscientific hypothesis at the heart of physics. If there is any reason to think otherwise, will someone please explain it to me.


Originally Posted by Pmb View Post
And time dilation does not merely refer to one an observer "sees" but what an observer measures. And its wrong to speak of the "speed" of a clock. The correct phrase is "rate" i.e. clocks at rest in frame S' are measured to run at a different rate that clocks at rest in frame S..
I was talking about clock rate but studiot raised an objection that I found incomprehensible, so I started talking about speed in case that helped. It's a pity people waste time arguing about differences between see and observe, and rate and speed.


Originally Posted by Pmb View Post
Being confirmed does not mean the same thing as being verified. Confirmed means to establish the truth of something. Being verified means that something has been shown to be consistent with something.
So if two false statement are consistent with each other, you are saying this means they are both verified? Again, arguments about just words rather than physics is a waste of time.


Originally Posted by Pmb View Post
There's a difference between being something being directly measured and something being verified. Length contraction has been verified in several ways. For a list of some of them see
https://en.wikipedia.org/wiki/Length..._verifications.
This article confirms that distance contraction has not been measured. It says, for example, muon paths through the atmosphere indirectly verify distance contraction. This is true in that it is consistent with SR's prediction, but this is just a prediction. It does not confirm/verify SR as no contraction of the atmosphere can be measured.

The more that people insult my understanding or intelligence and waste time on irrelevances, the more convinced I become that physics is riddled with false beliefs that physicists cannot defend.

It would be surprising if I were right about everything, but if I am wrong then why will no one address the questions I have posed in the three current threads? What is the evidence for multiple realities, what is the evidence for circulating perpendicular magnetic fields (as opposed to modifications of the electric field) and what is wrong with my simple algebra concerning the relationship between EM and SR?
AndrewS is offline  
Old Aug 13th 2017, 03:35 AM   #22
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 688
PMB to studiot
By the way: if a < b and b < a then that's a contradiction and does not imply that a = b.

That could only be true if and only if a <= b and b <= a

where "<=" means "is less than or equal to"
Yes that is the proper way to put it.
Thank you for the correction, PMB

PMB to Andrew S
You make totally wrong statements as if there were the word of God,
Exactly so and here is a perfect example of his rubbish.

Andrew S
Midway between two protons there may be no net EM force
Wow are there any more laws of Physics you would like to rewrite?
studiot is offline  
Old Aug 13th 2017, 03:41 AM   #23
Pmb
Physics Team
 
Join Date: Apr 2009
Location: Boston's North Shore
Posts: 1,191
Originally Posted by studiot View Post
Wow are there any more laws of Physics you would like to rewrite?
Actually, in that particular case, he's correct. If you were to place a charged particle exactly between two protons the force on that particle will be zero since the force on it from one proton has exactly the same magnitude but in the opposite direction thus canceling the force out. I.e. the electric field between two like charges is always zero.

Ignorant people are sometimes right, just not that often.
Pmb is offline  
Old Aug 13th 2017, 03:50 AM   #24
Member
 
Join Date: Jul 2015
Posts: 84
Thanks Pmb.
AndrewS is offline  
Old Aug 13th 2017, 04:53 AM   #25
Senior Member
 
Join Date: Nov 2013
Location: New Zealand
Posts: 519
Originally Posted by AndrewS View Post
The crux of the matter is that relativists seem to assume observers lives in separate universes. In contrast, nonrelativists experience the same universe, so a baseball can only have one real speed but lots of relative speeds. Everyone keeps ignoring my reply to Woody when I said x>y' and x'<y, i.e. relativists assume there are different worlds and that they are all equally real. Why will relativists not confirm their rejection of a single reality and provide experimental proof of their multiple realities? This seems to be another unscientific hypothesis at the heart of physics. If there is any reason to think otherwise, will someone please explain it to me.
Did anyone understand what I was saying in relation to simultaneity (in the previous videos) and the lack of a universal now? There is actual no problem with x>y' and x'<y because x is not equal x' and y is not equal y'. Its not a mathematical contradiction! It would be better to say it this way. The time recorded by observer 1 of his own clock x and the other travelling clock and observer 2 clock y, according to observer 1, shows that x > y. The time recorded by observer 2 of his own clock y and the other clock x moving relative to him, clock y, according to observer 2 shows that y' > x'. They are not both looking at the same time.

Let's do a for instance to make this more concrete. Let's say observer 2 travels past observer 1 (both are in space) and they synchronize both their clocks as they pass. Observer 2 is travelling a half the speed of light for ease of calculation. Then after 1 minute, according to observer 1, observer 2 's clock, again according to observer 1, is that sqrt(1-(0.5c)^2/c^2) = sqrt(3)/2 = 0.8660... minutes (about 51 seconds) However, observer 1 is travelling a half the speed of light in the opposite direction, according to observer 1 so that after 1 minute, according to observer 2, observer 1 's clock, again according to observer 2, is that sqrt(1-(0.5c)^2/c^2) = sqrt(3)/2 = about 51 seconds, so each is seeing the other persons clock slow down. How can this be? How can they both be slower?

Only one way I can see and that is each observer is not seeing each other's clock as it is now (their "now") but as it was in the past. Therefore each observer is somehow seeing the other person's clock backwards in time. What is interesting is that neither person see's the other person's future. Golly, what would that say about free will if they actually could. That would be an even bigger conundrum.

However from here I also get a bit confused but it seems to me that's its possible the faster we move the longer it takes for the reality of slowing moving objects to "catch up". I find this easier to mentally grasp than trying to say both observers are in two different realities, they are not really, they are just out of sync. Might this be less mentally "disturbing" to @AndrewS? At least it doesn't strain so much at trying to make two mathematical inequalities the same in both directions as they are not really the same "now". Crudely speaking the "now" of each relative observer is taking a bit longer to "catch up" with the "now" of the other observer and this "catching up" happens in both directions. I think this is why we have symmetry rather than no symmetry and why no one can see into anyone's future (at least not in the sense that their "now" is ahead of ours.) So I don't think anyone is saying there is multiple realities, just that they become lagged at high velocities. @AndrewS, does this help?

If there is something slightly semantically wrong with my explanation I'll let a more seasoned physicist on this forum fix it up but that's how this concept fits in my brain.
kiwiheretic is offline  
Old Aug 13th 2017, 06:23 AM   #26
Member
 
Join Date: Jul 2015
Posts: 84
Originally Posted by kiwiheretic View Post
Did anyone understand what I was saying in relation to simultaneity (in the previous videos) and the lack of a universal now? ... They are not both looking at the same time.

Only one way I can see and that is each observer is not seeing each other's clock as it is now (their "now") but as it was in the past.

I find this easier to mentally grasp than trying to say both observers are in two different realities, they are not really, they are just out of sync. Might this be less mentally "disturbing" to @AndrewS? At least it doesn't strain so much at trying to make two mathematical inequalities the same in both directions as they are not really the same "now".
Thanks for your clear and courteous comment.

I don't see how simultaneity or the lack of a universal "now" can explain the problem. The observations could be continued over an extended period of time such that the simultaneity of any given set of measurements is not an issue. The observers can measure the same ratio, the rate of A's clock/the rate of B's clock, over months or even years so it seems to me that their "nows" are irrelevant.

I still see this as an issue of realities, a question of whether there is one ratio or not. Multiple realities would be disturbing enough, but one reality that doesn't agree with itself would be worse. Returning to my example of plotting the observed time lags on a graph, I still do not see how both sets of lines can lag behind each other. These sets of observations can be brought to the same "now" and the same inertial frame if the rockets return to a central point via identical accelerations. To put it crudely, we have two horses in a race, and when film of the race is examined we find both horses were faster than each other. Or were there really four horses?
AndrewS is offline  
Old Aug 13th 2017, 06:42 AM   #27
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 688
Originally Posted by Pmb View Post
Actually, in that particular case, he's correct. If you were to place a charged particle exactly between two protons the force on that particle will be zero since the force on it from one proton has exactly the same magnitude but in the opposite direction thus canceling the force out. I.e. the electric field between two like charges is always zero.

Ignorant people are sometimes right, just not that often.
Is he?

Take two protons in equilibirum.

Now place a third proton exactly halfway, perhaps by shielding it until it is in place then suddenly removing the shield .

What happens?
studiot is offline  
Old Aug 13th 2017, 07:17 AM   #28
Pmb
Physics Team
 
Join Date: Apr 2009
Location: Boston's North Shore
Posts: 1,191
Wink

Originally Posted by studiot View Post
Is he?

Take two protons in equilibirum.

Now place a third proton exactly halfway, perhaps by shielding it until it is in place then suddenly removing the shield .

What happens?
In reality this is a question in quantum mechanics and all we can do is speak of probabilities.

However if we're talking about classical electrodynamics then he's correct, the force on the third proton would be zero. I wrote a webpage in which I plotted the gravitational potential between two point particles in the Newtonian limit. See Figure 1 towards the bottom of the following webpage:
The Gravitational Field

At places where the gradient is zero the force on a particle placed at that point would be zero.


What do you think it should be and why?
Pmb is offline  
Old Aug 13th 2017, 08:41 AM   #29
Senior Member
 
Join Date: Apr 2015
Location: Somerset, England
Posts: 688
PMB
What do you think it should be and why?
I think this is a question of electrostatics, not electrodynamics for starters.
There are no electromagnetic or just magnetic fields in electrostatics.

Yes I agee that there is a null point in the electrostatic field at the midway point.

But that is in the field and I asked what happens if another charge is introduced as you suggested. There is no force applied to anything anywhere in the field unless another charge is introduced . The field itself is not force.

What happens depends entirely on the equilibrium of the original two protons.
That is how they are held in place.
They must be held or they would be moving apart.

If the reactive force holding them is the exact amount required to maintain equilibrium, they will be moved apart by the addition of another proton.

That is the situation changes form an electrostatic one to an electrodynamic one.

All this is, of course, a consequence of Earnshaw's theorem.
studiot is offline  
Old Aug 13th 2017, 09:04 AM   #30
Pmb
Physics Team
 
Join Date: Apr 2009
Location: Boston's North Shore
Posts: 1,191
Originally Posted by studiot View Post
I think this is a question of electrostatics, not electrodynamics for starters.
There are no electromagnetic or just magnetic fields in electrostatics.
Nobody suggested the two initial protons were to be held fixed and I don't see a reason to assume it to be the case. By the way, it's not possible to shield an electric field.

Originally Posted by studiot View Post
Yes I agee that there is a null point in the electrostatic field at the midway point.

But that is in the field and I asked what happens if another charge is introduced as you suggested.
So that's what this is all about. He said that the force between two protons may be zero and you of course thought he made no sense because there's nothing there for a force to act on. Next time just ask him about it rather than taking him literally. People do make mistakes, even crackpots like him. Don't waste your time with semantics. It never does any good.

Last edited by Pmb; Aug 13th 2017 at 09:32 AM.
Pmb is offline  
Closed Thread

  Physics Help Forum > Physics Forums > Physics

Tags
dilation, time



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Example of length contraction and time dilation. avito009 Special and General Relativity 4 Jul 6th 2017 11:38 PM
Time dilation problem monster Special and General Relativity 6 Jun 18th 2017 07:11 PM
Struggling with Time Dilation Skornyak Special and General Relativity 9 Jul 19th 2016 06:27 PM
Trouble understanding time dilation toprun91 Special and General Relativity 26 Feb 19th 2010 01:16 PM
Time Dilation HassanZahid Special and General Relativity 8 Mar 21st 2009 04:48 AM


Facebook Twitter Google+ RSS Feed