Register | Sign In


Understanding through Discussion


EvC Forum active members: 59 (9164 total)
3 online now:
Newest Member: ChatGPT
Post Volume: Total: 916,929 Year: 4,186/9,624 Month: 1,057/974 Week: 16/368 Day: 16/11 Hour: 0/4


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   General Relativity.
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 60 of 129 (247677)
09-30-2005 1:48 PM
Reply to: Message 15 by cavediver
09-17-2005 7:35 AM


Re: My feeble attempt at understanding
Well, after thinking a little more about the rest of what you have given me, it seems you have answered my question regarding where space goes when something “occupies” it. Looks like it becomes it!
Cavediver:
when we expand to something like supergravity or string theory, we regain this wonderful picture that space and matter are the same thing.
This is strange, but I see where it parallels string theory. So, it seems that my prior post has to be rephrased to wonder what happens as one bit of curved space approaches another bit of curved space? A photon is matter with no mass, so what does it do? I suppose from its perspective it instantaneously arrives at different locations to perform various tasks, such as adding energy to an electron, or becoming the energy released by an electron. It travels through space from ours, so, in this regard, can space be considered a medium (I have had the impression that this is an incorrect way to think about space)? Because, as has been shown, space can change the wavelength of light, so space does have some effect on light. I suppose you could even say that space is why light has a wavelength.
I also posted some other ideas earlier regarding GR that I wanted you to peruse, perhaps your a bit busy with life.
This message has been edited by madeofstarstuff, 09-30-2005 01:50 PM

This message is a reply to:
 Message 15 by cavediver, posted 09-17-2005 7:35 AM cavediver has not replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 71 of 129 (250796)
10-11-2005 12:04 PM


One more try
Since no one seemed to reply to my prior messages regarding this I must have not explained myself very well. I will try to restate my (mis)understandings of GR, and if no reply, I'll drop it and try to figure it our for myself.
Let’s say there is I, who is in an area of space that I will initially assume is removed from any significant curvature, meaning that the space around me is of uniform density. I walk thirty feet in the y direction and place a dog (point A) that stays stationary. I then return to my original position and walk 40 feet into the x direction and place a bone (point B). If I then return again to my original position and view both the dog and that bone at the same time there are a few things I can assume to be true.
Firstly I can rightfully assume that the distance between the two, from point A to point B is 50 feet, simply from PT. I can also assume that if the dog traveled at a constant velocity with respect to point A from point A to point B I would see it move at a constant velocity as well. I can finally assume that the time I would measure as the dog moves from point A to point B would be slightly more than the time measured by the dog (if it had a clock) according to the Lorentz transformation, and along with this, a calculation that would result in a slightly greater distance. Since I know this I can account for it and come to the conclusion that the 50 feet is correct.
I now watch the dog travel to the bone along a straight line at a constant velocity, say 5 feet per second, and admire its behavior. Unbeknownst to me there is an enormously massive object lying slightly off of the course that the dog must take to get to the bone. Because of this the space right in the middle of the path has severe curvature. This curvature will cause two things to occur.
1) The velocity of the dog will not appear to be uniform from my perspective.
2) The time I measure for the dog’s journey will be even greater than the time allotted for the Lorentz transformation.
This begins to trouble me and I begin to think that the dog didn’t go in a straight line at a constant velocity. I decide to take the trip myself by walking out to point A and traveling to point B. I will measure the distance I cover in space by using my constant velocity (still 5 feet per second) times the time I record.
I realize that what would actually be experienced is I would measure 10 seconds and assume 50 feet. In fact, I would actually travel more space per unit time in the severely increasingly curved volume and less space per unit time in the severely decreasingly curved volume. I wouldn’t “feel” any of this so I would still be justified in saying that I was in uniform motion. I will be surprised however, when I measure this distance using the same yardstick as before to be 60 feet instead of 50 since my motion was uniform (5 feet per second) initially with respect to point A.
This is where I am confused. Can I look from point A to point B and "see" 50 feet, but measure 60 feet? Am I justified when looking from the origin to assume 50 feet? I would assume not considering the true distance is 60 feet. Would it actually appear this way or am I confusing two issues here?
According to the dog that has gone to my original location (origin), my motion wasn’t uniform and the time it took me to traverse this space is longer on its clock (assuming it is wearing one) than on mine. Using this model though, how is it that the time measurements will differ? I understand that my motion through time will decrease while the dog’s remains the same (all motion is through time), but where is the physical representation of this occurrence? How is it that uniform motion through curved space actually increases, or decreases, your actual velocity with respect to another body? What is the element responsible for this? Do I even have an accurate understanding of this situation?

Replies to this message:
 Message 72 by cavediver, posted 10-11-2005 12:33 PM madeofstarstuff has replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 84 of 129 (251115)
10-12-2005 11:14 AM
Reply to: Message 72 by cavediver
10-11-2005 12:33 PM


Relative lengths
You won't ever see 50 feet and measure 60 feet.
If I am just standing as I have described, and know with certainty (by infinitely precise measurement) that there is, say, 30 light years of (as perfectly as possible) flat space in one direction to a point A. At 90 degrees to this there is 40 light years of flat space to a point B. Am I not justified, conventionally, in believing that there is 50 light years of flat space in a straight line between these two points assuming no curvature between?
If there were curvature between these two points, would there no longer appear to be 30 ly of flat space in direction A and 40 ly of flat space in direction B? I would further assume that perhaps the angle between the two points from my vantage point would no longer appear to be 90 degrees. Would this curvature between the two points A and B alter my perception of the position of these two points A and B so that they wouldn't appear as they would have had there been no immense mass between them?
I hope I haven't blurred my intent here, but can curvature in one area of otherwise flat space alter the perception of distant objects within said flat space so that you wouldn't perceive the 90 degree angle to begin with?

This message is a reply to:
 Message 72 by cavediver, posted 10-11-2005 12:33 PM cavediver has replied

Replies to this message:
 Message 85 by cavediver, posted 10-12-2005 1:03 PM madeofstarstuff has replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 95 of 129 (252562)
10-18-2005 12:55 AM
Reply to: Message 85 by cavediver
10-12-2005 1:03 PM


Re: Relative lengths
Cavediver:
Thus you can still have A and B appearing at 90 degrees and at the declared distances, but the line AB will certainly not be the pythagorean distance, nor the angles OAB and OBA the expected trignometric values.
So how do you distinguish between the pythagorean and the nonpythagorean distance? If you look out and are justified in seeing the pythagorean distance and have no reason to believe otherwise, with respect to what is there more than the pythagorean distance? It seems as though there is some standard of distance in a certain inertial frame of reference as long as you have no knowledge of the increased density of space. This "extra" space is seemingly packed into an apparent pythagorean amount of space, so why would you need to know the curvature was there to accurately render your environment? Why should it not be apparent?

This message is a reply to:
 Message 85 by cavediver, posted 10-12-2005 1:03 PM cavediver has replied

Replies to this message:
 Message 96 by cavediver, posted 10-18-2005 5:08 AM madeofstarstuff has replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 97 of 129 (252700)
10-18-2005 10:19 AM
Reply to: Message 96 by cavediver
10-18-2005 5:08 AM


Re: Relative lengths
OK, thats what I thought, that is strange. So if I were standing at O and saw something traveling at constant v toward AB, what would their motion look like from O as they progressed (continually from their perspective at v) from A to B?

This message is a reply to:
 Message 96 by cavediver, posted 10-18-2005 5:08 AM cavediver has replied

Replies to this message:
 Message 99 by cavediver, posted 10-18-2005 1:41 PM madeofstarstuff has replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 100 of 129 (252794)
10-18-2005 2:54 PM
Reply to: Message 99 by cavediver
10-18-2005 1:41 PM


Re: Relative lengths
Is that because the time dilation is more prominent than the spatial "contraction"?

This message is a reply to:
 Message 99 by cavediver, posted 10-18-2005 1:41 PM cavediver has not replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 101 of 129 (253087)
10-19-2005 2:10 PM


Progression of Events
I tried to get a new thread on this but it was denied, but I'm also not sure whether its relevant to a GR thread, so I will ask anyway because I am curious. When something, anything, changes from one instant to the next (strictly QED), is this due solely to the exchange of a photon from one electron to the other? I assume that these events, photon exchanges, occur instantaneously. If a body of mass (which is mostly affected by EM radiation) changes in some way (be it momentum or velocity), is this due to an exchange of a photon? Can anything noticeable happen without this exchange? Is absorbing a photon the only way to "realize" anything happened? Lastly, does this indicate that time is discrete in its progression from one "instant" to the next, or has it been shown to be analogous?

Replies to this message:
 Message 104 by cavediver, posted 10-20-2005 9:18 AM madeofstarstuff has replied

  
madeofstarstuff
Member (Idle past 5960 days)
Posts: 47
Joined: 08-12-2005


Message 105 of 129 (253403)
10-20-2005 1:40 PM
Reply to: Message 104 by cavediver
10-20-2005 9:18 AM


Re: Progression of Events
quote:
A bit too busy at the moment
I understand. I appreciate the time you have given me so far. I had also replied to your revealing to me the motion of a thing through a curved space being perceived as acceleration without force. I had wondered if this was due to the time dilation being more prominent than the spatial contraction.
Take your time, I don't plan on having my death event anytime soon, and once again thanks for your time and patience.

This message is a reply to:
 Message 104 by cavediver, posted 10-20-2005 9:18 AM cavediver has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024