Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 67 (9049 total)
58 online now:
anglagard, AZPaul3, jar, nwr, PaulK (5 members, 53 visitors)
Newest Member: Wes johnson
Upcoming Birthdays: Astrophile
Post Volume: Total: 887,596 Year: 5,242/14,102 Month: 163/677 Week: 22/26 Day: 4/6 Hour: 0/2


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   What is Time and Space
randman 
Suspended Member (Idle past 3917 days)
Posts: 6367
Joined: 05-26-2005


Message 91 of 204 (231479)
08-09-2005 3:33 PM
Reply to: Message 90 by Son Goku
08-09-2005 2:42 PM


Re: thanks
however because of length contraction it also sees everything compressed to one point.
This is what I meant by their view of the world being unusual. They basically have no point of view, everything to them is crushed into a single moment, in a single spot.

Thanks for helping me here, btw.

Why couldn't that one spot be massive, many, many times the size of the universe with all points in time (all changes) spread out like folds or something or pages in a book torn out and laid out in one large spot bigger, but flatter, than the book?

I guess I don't understand "length contraction."

Once again, any help would be appreciated.


This message is a reply to:
 Message 90 by Son Goku, posted 08-09-2005 2:42 PM Son Goku has not yet responded

  
Son Goku
Member
Posts: 1181
From: Ireland
Joined: 07-16-2005


Message 92 of 204 (231488)
08-09-2005 3:50 PM


Length contraction is one prediction of relativity.

The faster I go, the shorter lengths appear.

When I'm standing still, the distance between the Earth and the moon is 384,400 km.

If I'm going at half the speed of light, the distance between the Earth and the Moon is 332, 900 km.

If I'm going at 99% of the speed of light, the distance between the Earth and the Moon is 54, 226 km

However if I'm going at the speed of light the distance between the Earth and the Moon is zero.
In fact the distance between anything is zero.
And the time between any two events is zero.

So to a photon everything happens all at once and in the same spot.
So there is no time or space for the changes to "fit" into.


Replies to this message:
 Message 93 by randman, posted 08-09-2005 4:35 PM Son Goku has responded

  
randman 
Suspended Member (Idle past 3917 days)
Posts: 6367
Joined: 05-26-2005


Message 93 of 204 (231520)
08-09-2005 4:35 PM
Reply to: Message 92 by Son Goku
08-09-2005 3:50 PM


maybe relativity is incomplete
In fact the distance between anything is zero.
And the time between any two events is zero.

So to a photon everything happens all at once and in the same spot.
So there is no time or space for the changes to "fit" into.

Maybe there is some incompleteness to relativity, specifically assuming only a 3-D with time, or 4-D, universe. Entanglement indicates processes that occur superluminally.

Maybe there are superluminal dimensions?

spiritual dimensions?

What do you think?

It doesn't seem correct that everything can exist in a single spot with no distance. I sort of see from that vantage perspective, and maybe all mass is actually non-separable and existing in one spot, but it defies the imagination how you can even have a spot without distance. Is there a quanta for distance that defines a spot that has no distance within it?

If such a concept could somehow be true, then it seems that what we are seeing with space is an imagination, something that appears to occupy distance, speed, laws, etc,...but in reality exists all in one location that is defined as occupying no real space.

Hmmmm....the mind of God?


This message is a reply to:
 Message 92 by Son Goku, posted 08-09-2005 3:50 PM Son Goku has responded

Replies to this message:
 Message 98 by Son Goku, posted 08-10-2005 2:51 PM randman has responded

  
GDR
Member
Posts: 5410
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 94 of 204 (231578)
08-09-2005 6:20 PM


Gravity?
This is maybe off topic for this thread but it is close. I understand that under GR gravity is acceleration. If I fall out of an airplane I'm just hanging in space and the Earth rushes up to meet me.

I'm having trouble with this on a couple of grounds. Is this acceleration to do with our movement relative to the sun, relative to the gravitaional field of all mass and energy, has it to do with the fact that all galaxies are accelerating away from each other, or is it something else entirely?

It also is difficult to understand how the Earth is accelerating upward at both the north and south poles simultaneously.

Any help is appreciated.


Replies to this message:
 Message 95 by cavediver, posted 08-10-2005 5:13 AM GDR has responded

  
cavediver
Member (Idle past 2662 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 95 of 204 (231711)
08-10-2005 5:13 AM
Reply to: Message 94 by GDR
08-09-2005 6:20 PM


Re: Gravity?
I understand that under GR gravity is acceleration

No, gravity is curvature.

Remember in my initial discussion on SR, we all have a 4-velocity in space-time. The question is in what direction is this velocity pointing? What track through space-time do we take? Well, just like everyday experience we follow "straight" lines. We call these geodesics. Think of the aircraft following a great circle path around the earth... it's not straight in the usual definition, but it is the straighest path over a curved globe. It is the path something will move along if pushed and then does not subsequently accelerate.

Mass/energy curves space-time, so the geodesics are curved away from naive ideas of straight. Discovery has just returned from following a straight line which happens to be so curved it closes up into a "circular" path all the way around the earth. The orthogonal straight line (geodesic) to the orbit is a path straight towards the earth. If you "fall" along these paths, you are following the curvature of space-time. You experience no acceleration, no force. Hence being weightless both in orbit and in free-fall (ignoring air-resistance). To deviate from a geodesic, you need to exert a force.

This is the crux... it led Einstein to GR. The 1g we experience on the earth is not gravity. It is the up-push from the earth forcing us off our preferred geodesic which is to "fall" to the centre of the earth.

If we increase this force, by use of Discovery for instance, we increase this 1g force and we move further away from the geodesic. In fact, with Discovery, we exert sufficient force to move us onto a new orbital geodesic.

If you jump out of plane, nothing accelerates. You just move naturally. It is, as you say, the surface of the earth accelerating towards you.

It also is difficult to understand how the Earth is accelerating upward at both the north and south poles simultaneously

Of course it's diificult, it's GR :) But it is true. Acceleration does not imply "movement". It's a problem of trying to interchange 3d concepts and 4d concepts... it doesn't work.

And this is all totally local. The space-time around the earth is massively dominated by the earth, such that the sun, moon, distant stars and galaxies have no appreciable effect.


This message is a reply to:
 Message 94 by GDR, posted 08-09-2005 6:20 PM GDR has responded

Replies to this message:
 Message 96 by GDR, posted 08-10-2005 10:42 AM cavediver has not yet responded

  
GDR
Member
Posts: 5410
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 96 of 204 (231807)
08-10-2005 10:42 AM
Reply to: Message 95 by cavediver
08-10-2005 5:13 AM


Re: Gravity?
Thanks cavediver

I'm probably reasonably normal in that my mind is locked in 3d. That was really helpful and I am going to have to think and read more on geodesics.

I should have sorted out the north and south pole thing as the idea that gravity is maintaining us on the ground at both poles is related to the concept that it we leave the north pole flying right side up we're still right side up, (not inverted), at the south pole, which, (I think) proves that the answer had to be outside of my 3d thinking. I keep trying to picture 4d in my mind but I have to say that I'm not making a lot of progress. I have to stop think of the world as a sphere in 3d and start trying to picture a tube in 4d some how.


This message is a reply to:
 Message 95 by cavediver, posted 08-10-2005 5:13 AM cavediver has not yet responded

  
GDR
Member
Posts: 5410
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 97 of 204 (231943)
08-10-2005 2:46 PM
Reply to: Message 43 by cavediver
07-31-2005 2:40 PM


Projection
cavediver writes:

And is the universe open or closed? Well, I would like it to be closed on aesthetic grounds. But I'm not that bothered. And don't forget that the chances that our observed 4d universe is the real "universe" are slim... it is much more likely part of a much larger multiverse/encompassing existence, which may embed our universe or more bizarrely "project" our universe.

I have been mulling this over ever since you posted it 10 days ago. I like the term projection. I had been thinking of us as a reflection or even a shadow but I think projection is a much more accurate depiction of the theory.

What does this mean to cosmology. If we aren't part of the "real" universe what scientists are studying isn't reality. Watching a movie on a screen doesn't tell you anything about what is going on in the projector. It seems to me that everytime there is a breakthrough in science we open one door only to find we have 4 more closed doors staring us in the face. It seems like the more we learn the less we know.

When science finally comes up with a unifying theory it will probably find that you are right. What then? We will have a great deal of knowledge about what is being projected but we'll still know very little about the projector.

Is the projector the same thing as what we refer to as the metaphysical or is that something else again? Who knows? We think that as a civilization that we have acquired so much knowledge. The trouble is, there is no objective standard for thinking that. How much knowledge is there to be had and how much of it is actually accessible to us.

Sorry to ramble on but I have just been so intrigued by your post.


Everybody is entitled to my opinion. :)

This message is a reply to:
 Message 43 by cavediver, posted 07-31-2005 2:40 PM cavediver has responded

Replies to this message:
 Message 99 by Son Goku, posted 08-10-2005 2:54 PM GDR has not yet responded
 Message 103 by cavediver, posted 08-10-2005 6:51 PM GDR has responded

  
Son Goku
Member
Posts: 1181
From: Ireland
Joined: 07-16-2005


Message 98 of 204 (231946)
08-10-2005 2:51 PM
Reply to: Message 93 by randman
08-09-2005 4:35 PM


Re: maybe relativity is incomplete
Everything is only one place and time from a photon's point of view.

Ordinary matter still experiences time and space.

This doesn't mean that space or time are ilusions in any way, just that a photon doesn't really have a conventional point of view, in fact in essence it doesn't have one at all.

The best way to phrase it is that space and time are very much real, but a photon has no consistent point of view from which to judge them.

This is summed up by the fact that a photon has no reference frame.


This message is a reply to:
 Message 93 by randman, posted 08-09-2005 4:35 PM randman has responded

Replies to this message:
 Message 100 by randman, posted 08-10-2005 5:46 PM Son Goku has not yet responded

  
Son Goku
Member
Posts: 1181
From: Ireland
Joined: 07-16-2005


Message 99 of 204 (231952)
08-10-2005 2:54 PM
Reply to: Message 97 by GDR
08-10-2005 2:46 PM


Re: Projection
http://en.wikipedia.org/wiki/Holographic_principle

This is what the whole projection thing is about.


This message is a reply to:
 Message 97 by GDR, posted 08-10-2005 2:46 PM GDR has not yet responded

Replies to this message:
 Message 101 by cavediver, posted 08-10-2005 6:41 PM Son Goku has not yet responded
 Message 102 by cavediver, posted 08-10-2005 6:47 PM Son Goku has not yet responded

  
randman 
Suspended Member (Idle past 3917 days)
Posts: 6367
Joined: 05-26-2005


Message 100 of 204 (232017)
08-10-2005 5:46 PM
Reply to: Message 98 by Son Goku
08-10-2005 2:51 PM


Re: maybe relativity is incomplete
"No reference frame"?

Does that mean the photon exists apart from 4-D? Maybe we are just seeing part of the photon and it does have a reference frame, but within a deeper, superluminal structure or dimension?

I guess it just does not yet make sense to me that a photon can exist in 4-D and not have a reference frame. That suggests we are arbitrarily limiting the universal to non-superluminal dimensions and a more complicated process is at work.

What do you think? Is GR just too incomplete?


This message is a reply to:
 Message 98 by Son Goku, posted 08-10-2005 2:51 PM Son Goku has not yet responded

  
cavediver
Member (Idle past 2662 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 101 of 204 (232044)
08-10-2005 6:41 PM
Reply to: Message 99 by Son Goku
08-10-2005 2:54 PM


Re: Projection
This is what the whole projection thing is about

That's certainly part of it... and I claim a small credit in having a very long and detailed discussion with Lenny Susskind about black hole mappings when he was just developing his ideas. He's a particle physicist really, so needed a little coaching ;) It all seems many lifetimes ago now :(

But the HP is only one aspect of what I am talking. If you scan over my posts, you should find my piece on how our space-time (target space in string speak) is just a projection from the "real" 2d string worldsheet. I love this because it reduces everything to the mathematics/geometry of Riemann surfaces. I still find this exceptionally aesthetic.


This message is a reply to:
 Message 99 by Son Goku, posted 08-10-2005 2:54 PM Son Goku has not yet responded

  
cavediver
Member (Idle past 2662 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 102 of 204 (232046)
08-10-2005 6:47 PM
Reply to: Message 99 by Son Goku
08-10-2005 2:54 PM


Re: Projection
Cool!!! Just noticed Raphael's name in the references of the Wikipedia piece. Raph, whilst studying part III, came out of one of my black hole tutorials and said "#####, that was the best lecture I've ever had" :) Later we shared an office for a few years. Oh, it takes me back...

This message is a reply to:
 Message 99 by Son Goku, posted 08-10-2005 2:54 PM Son Goku has not yet responded

  
cavediver
Member (Idle past 2662 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 103 of 204 (232050)
08-10-2005 6:51 PM
Reply to: Message 97 by GDR
08-10-2005 2:46 PM


Re: Projection
Is the projector the same thing as what we refer to as the metaphysical

No, not at all. It's just a deeper level of the maths/physics. I can get twitchy when people start using qm/gr as entrances to the metaphysical, as Randman is doing. There is nothing mysterious about QM when looked at mathematically. My personal position is that there is not a single stroke of evidence for God in the physical universe. A perfect artist doesn't leave brush strokes... or a perfect watchmaker, scratches...


This message is a reply to:
 Message 97 by GDR, posted 08-10-2005 2:46 PM GDR has responded

Replies to this message:
 Message 104 by GDR, posted 08-10-2005 7:17 PM cavediver has responded
 Message 105 by randman, posted 08-10-2005 8:55 PM cavediver has responded
 Message 116 by randman, posted 08-13-2005 12:41 AM cavediver has responded

  
GDR
Member
Posts: 5410
From: Sidney, BC, Canada
Joined: 05-22-2005


Message 104 of 204 (232059)
08-10-2005 7:17 PM
Reply to: Message 103 by cavediver
08-10-2005 6:51 PM


Re: Projection
cavediver writes:

No, not at all. It's (the projector)just a deeper level of the maths/physics.

If we are a projection then what are we a projection of?

String theory postualtes that everything is made up of minute bits of energy. Schroeder goes futher and suggests that this energy is fundamentally information. It makes sense to me that we are a projection. What constitutes the real world where the projector resides. Are we talking about something that is real, abstract or just a mathematical formula?


Everybody is entitled to my opinion. :)

This message is a reply to:
 Message 103 by cavediver, posted 08-10-2005 6:51 PM cavediver has responded

Replies to this message:
 Message 109 by cavediver, posted 08-11-2005 4:37 AM GDR has responded

  
randman 
Suspended Member (Idle past 3917 days)
Posts: 6367
Joined: 05-26-2005


Message 105 of 204 (232093)
08-10-2005 8:55 PM
Reply to: Message 103 by cavediver
08-10-2005 6:51 PM


Re: Projection
Cavediver's looking at the spiritual and metaphysical straight in the face, if not the next step past the word of God in creating and upholding the physical universe, but he doesn't see the forest for the trees.

That's Ok for this discussion. We can disagree.

The topic is the actual science and data, and hopefully cavediver won't begrudge me for learning, from him and others, and just can't help it, but the more I learn, the more it dovetails the spiritual principles I had learned before.


This message is a reply to:
 Message 103 by cavediver, posted 08-10-2005 6:51 PM cavediver has responded

Replies to this message:
 Message 106 by GDR, posted 08-11-2005 3:40 AM randman has not yet responded
 Message 107 by cavediver, posted 08-11-2005 3:55 AM randman has responded
 Message 108 by cavediver, posted 08-11-2005 4:08 AM randman has responded

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2021