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Author Topic:   How is the Universe here?
cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 1 of 131 (486965)
10-26-2008 10:38 AM


Despite the constraints on my time, I feel a thread on this is long overdue given its prominence in the EvC debate. I want to go beyond the usual confused discussions around the Big Bang, and look at more generalised concepts (though the BB will be covered as an example in various sub-threads.) I want to look at our understanding of time, beginnings, endings, infinities, somethings-from-nothings, etc. I should stress that this will be firmly based on our understanding of relativity, with inspiration from string theory, loop QG, etc, and some quantum theory, but we will be using this to launch into *informed* speculation. The main goal is to break down common prejudices and misunderstandings - if by the end you feel you know less than when you staretd, that's not necessarily a bad thing :)

Once (if) this is promoted, I think we'll begin with time.

Big Bang and Cosmology please.

Edited by cavediver, : No reason given.


Replies to this message:
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 3 of 131 (486971)
10-26-2008 11:44 AM


Ok, time...

Einstein's Special Theory of Relativity introduces us to the concept of time as a dimension, very similar to our three spatial dimensions. (The clue to this was in Maxwell's Equations of electromagnetism, which could be written in exceptionally simple form once time was treated as the fourth member of the (x, y, z ) set.)

But this wasn't actually the biggest shake-up to our concept of time. Space-time was actually already an existing concept with Newtonian phsyics, and we can easily imagine a simple 4d space-time reality, with time perpendicular to the space. A cross-section of this space-time gives the Universe at a particular time, and the experience of time is essentially this "now" cross-section inexoriably marching forwards in time, carrying our experience with it. Imagine a tall stack of paper: each sheet of paper is space at a different time. My life would start on one sheet and would trace a path upwards through each sheet of paper until we reach the sheet of my death. At any particular moment, I am sat on a particular sheet. Everything that occurs on that sheet, occurs "now". Anything on lower down sheets happened in the past, and anything that occurs on sheets above, happens in the future.

SR showed this to be incorrect. There is no universal cross-section of the Universe, no universal now. Each of us has our own path through space-time, and we each define our own "now", which will not necessarily agree with someone else's "now". My "now" is no longer the piece of paper I'm sat on, but rather a a slice through the stack of paper at an angle, and your "now" might be a different slice, so that some things I regard as happening in my past, you may regard as yet to occur.

So our first lesson is that although time is a universal dimension, our experience of time is completely individual.

Before I bring in the changes Genral Relativity introduces, I'll pause for some discussion/questions.

Edited by cavediver, : No reason given.


Replies to this message:
 Message 9 by Agobot, posted 10-26-2008 1:55 PM cavediver has responded
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 Message 14 by johnfolton, posted 10-27-2008 11:46 AM cavediver has not yet responded
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 5 of 131 (486974)
10-26-2008 12:20 PM
Reply to: Message 4 by Agobot
10-26-2008 12:11 PM


Although obviously relevant, I want to stay away from quantum interpretation for now, in this thread at least.
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 7 of 131 (486980)
10-26-2008 1:22 PM
Reply to: Message 6 by Taz
10-26-2008 1:16 PM


Better?
This message is a reply to:
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 19 of 131 (487089)
10-27-2008 4:11 PM
Reply to: Message 13 by Thugpreacha
10-27-2008 10:21 AM


Sorry, been a very long day!!!

Are you saying that an event in my past may be an event in your future?

Yes :) But not all events. In Newtonian space-time, there is a universally agreed now (as we all set our watches by Greenwich) and all events occur either now (on our current sheet of paper), in our past, or in our future. We could be opposite sides of the universe, but we'd still agree on this three-way split of events. And, thinking ahead a bit, our relative motion would be irrelevant.

But in Special Relativity, we have the finite speed of light... Things in our past have to be able to influence us now - that's what 'in our past' means. So it must be possible to send a signal from a past event to us now. This signal can only travel at the speed of light, max. What about events that are sufficiently far away from us that they could not affect us *now*? For example, in takes 8 minutes for light to reach us from the Sun. So what about an eruption on the Sun's surface 4 minutes ago? That cannot affect us *now*. So it is not in our past :) But nor is it in our future. We say that it is 'elsewhere', because us phsyicists think that sounds cool :cool:

Now, no-one else will ever see our *past* events as anything but in our past - otherwise, they would see me influenced by something yet to happen! And that breaks causality. But *elsewhere* events cannot influence me *now*, so even though I think the explosion occured 4 minutes before I clap my hands, there's nothing wrong with someone else thinking that it happened four minutes AFTER I clapped my hands. And that may well be what they see if they are travelling at an appropriate speed and direction relative to me and the Sun.

Diagram time:


\ /
\ Future /
\ (Light / \
\ cone) / \
\ / \
\ / \ ^ Time
\ / Elsewhere |
Elsewhere \ / \ |
X------Me *now* \ |___ Space
/ \ \
/ \ \
/ \ \
/ Past \ \
/ (Light \ *
/ Cone) \ Sun goes bang
/ \

Edited by cavediver, : No reason given.


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 20 of 131 (487091)
10-27-2008 4:35 PM
Reply to: Message 12 by Straggler
10-27-2008 7:36 AM


Re: Entropy
How does the idea of ever increasing entropy fit into individual, as opposed to universal, time?

If we consider just our standard Universe, with the Big bang, then all possible paths through space-time begin in the Big Bang (all of the matter in your body for example began here) and then wind off into the future. All start in a region of low entropy and entropy increases as time increases. Some of those paths may be extremely relativistic, such that a particle my arrive here on Earth that has only seen 48 hours since the Big Bang! But it still has travelled from a low entropy time to a higher entropy time. Entropy merely reveals the flow direction of these paths, but not the rate of passage of time along these paths. Analogy - all possible paths lead down from the summit of a mountain (by definition of 'summit') but not all paths have the same gradient.

Is our view of the total entropy of the universe also individual if our view of time is individual?

It shouldn't be. Our different views cannot change 'reality'. If I see A happen before B, and you see B happen before A, that simply means that A and B are not within each other's light cones, and thus cannot affect each other. We say they are space-like separated. And there is no such thing as a time-ordering for A and B, despite our (contradictory) observations to the contrary.

But is it thought that time moves forward in discrete "sheets"

Good question - we don't know. Despite claims to the contrary, quantisation does not necessarily imply discreteness.


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


(1)
Message 21 of 131 (487092)
10-27-2008 4:48 PM
Reply to: Message 9 by Agobot
10-26-2008 1:55 PM


Cavediver writes:


SR showed this to be incorrect. There is no universal cross-section of the Universe, no universal now. Each of us has our own path through space-time, and we each define our own "now", which will not necessarily agree with someone else's "now". My "now" is no longer the piece of paper I'm sat on, but rather a a slice through the stack of paper at an angle, and your "now" might be a different slice, so that some things I regard as happening in my past, you may regard as yet to occur.

I am not sure most folks would understand this quoted paragraph

I thihk you may be right - it's a bit crap on second reading :)

Perhaps some diagrams would help?


Newtonian Picture:

Future

^ Time
|
----Now------------Me-------You--------Now--- |
|_____ Space

Past

Special Relativity:

\ /
\ Future /
\ (Light /
\ cone) /
\ /
\ / ^ Time
\ / Elsewhere |
Elsewhere \ / |
X------Me *now* |___ Space
/ \
/ \
/ \
/ Past \
/ (Light \
/ Cone) \
/ \

If we happen to meet, but are travelling at speed relative to each other:
^ Time
|
|
|___ Space

----____ Your now
----____
----____
---my now-----------------Us---------------my now------
----____
----____
----____ Your now
----


Any better?

Edited by cavediver, : No reason given.


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 25 of 131 (487099)
10-27-2008 5:04 PM
Reply to: Message 22 by onifre
10-27-2008 5:00 PM


But, even an event at 1Bly away does not take 1 billion years to reach us since light travels at (c). I believe, if im not mistaken, that 1Bly away would take light 1000 years to reach us.

No, the light year is defined as the distance light travels in one year. So one billion light years is traversed by light in one billion years (ignoring the slight cosmological considerations.) the value of c is usually measured in metres per second, ~ 300,000,000 ms-1


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 49 of 131 (487300)
10-29-2008 4:30 PM
Reply to: Message 48 by New Cat's Eye
10-29-2008 4:17 PM


Re: Reaming Time
Do you think it helps to think of this as your sheet being thicker than his?

No, not at all. What he means is that his sheets will cut across mine as they have a slightly different angle to the vertical. See my last diagram in Message 21 - the lines represent the sheets edge on.


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 54 of 131 (487724)
11-04-2008 4:29 AM
Reply to: Message 53 by john6zx
11-03-2008 8:43 PM


Re: Future and Past Ramblings
There is no physical scientific evidence that time, space, or dimensions are anything more than man made measurements.

No, none at all, unles you consider the whole of the past 100 years of relativistic and quantum field physics :laugh: Anyway, it does seem that there have been some genuine questions regarding the role of dimensions, in amongst the bleating of the ignorant, so I will get around to addressing this topic.

As a hint to the readers, if anyone starts making proclamations that space and time aren't things and are just measurments, and that real things are energy, etc, etc, then you need to actually ask them what they mean by 'things', 'energy', 'measurement', 'dimensions', etc. The fact is that they are peddling words with zero understanding. And if anyone thinks that I am doing the same, then call me on it.

But sorry guys - will be back soon, I promise. It's VAT return time, I've put my back out, and I have my largest ever orders to deal with over the next few days. Aghh...


This message is a reply to:
 Message 53 by john6zx, posted 11-03-2008 8:43 PM john6zx has responded

Replies to this message:
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 56 of 131 (487733)
11-04-2008 8:26 AM
Reply to: Message 55 by Stile
11-04-2008 8:08 AM


Re: Properties of the Universe
I think that both V-bird and cavediver are saying pretty much the same thing

god, I hope not :eek: V-bird is another loon who thinks that cosmological models are built from sciency-sounding words and layman sparks of 'inspiration'. If ever in doubt, just ask for a calculation based upon their ideas :) Say the spin-up rate of a pair of orbiting neutron stars and ask how it compares to the GR calculation based on their 'theoretical' emission of gravitational radiation...


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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 67 of 131 (487764)
11-04-2008 2:36 PM
Reply to: Message 66 by onifre
11-04-2008 2:27 PM


Re: Thin Ice.
which it doesn't seem like he wants to.

I take it you didn't read my previous post? You want to talk crap with V-bird, be my guest. But the more of that goes on the less likely I will get involved as I have no patience for this. There are a million cranks out there who all think THEY have the answer to cosmology's 'secrets' and 'surprisngly' none of these coincide other than in their universal dismissal of the knowledge contained in every cosmology/relativity departemnt in the world, and in their complete lack of evidence-backed predictions and calculations. If word-salads are your thing - go for it...


This message is a reply to:
 Message 66 by onifre, posted 11-04-2008 2:27 PM onifre has responded

Replies to this message:
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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 72 of 131 (487779)
11-04-2008 4:33 PM
Reply to: Message 68 by V-Bird
11-04-2008 2:53 PM


Re: Thin Ice.
Hi V-Bird - as much as I have no time for your own take on space-time physics, I am humbled by your restraint and grace in the face of my impatient belligerence :) All credit to you...

And if anyone was wondering, VB and I have crossed paths elsewhere in the past, so this is not new. VB has his own ideas that simply take a different path to that taken by the rest of the physics community 100 years ago when Minkowski introduced his space-time concepts to Einstein's Theory of Special Relativity. Einstein took this wholly on board and is absolutely central to his General Relativity. It is also central to our understanding of Quantum Field Theory. As anyone who follows my posts will be aware, GR and QFT are the two most successfully tested theories known to man. Essentially, VB is arguing with concepts from 100 years ago. We are now so far beyond this level of thinking that it seems bizarre to back-track to address it. But then, we have been back tracking to Newton with Buzsaw's ridiculous cosmological ideas!

I cannot stress strongly enough that the ideas I am presenting here are not soley my own, but are based on the concensus of modern day cosmology, relativity, and theoretical phsyics. I will be pushing into my own speculation, but this will be where we go beyond current understanding, and I will be presenting multiple options with no pretense that any one has supporting evidence.

If anyone is interested in VB's ideas, I suggest opening a new thread.


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 Message 68 by V-Bird, posted 11-04-2008 2:53 PM V-Bird has responded

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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 77 of 131 (487785)
11-04-2008 9:39 PM
Reply to: Message 75 by john6zx
11-04-2008 9:10 PM


Re: Future and Past Ramblings
:laugh: :laugh: :laugh:

No evidence???? Just because you know nothing of the past 100 years of EVIDENCE does not mean it does not exist. It just means that you are a fool parading your pathetic lack of knowledge before a large audience. You are going to call me on it??? :laugh: God, do you manage to tie your own shoelaces? Have you never heard of gravitational lensing, frame-dragging, binary pulsar dynamics, etc, etc. Anyone else interested, just pop along to Wikipedia. And that is just GR. SR and QFT are at the heart of every particle accelerator around the world. Guess what? They work!! That is called indisputable evidence of the correctness of SR and QFT to incredible levels of accuracy. And you say that there is no evidence :laugh:

All you need to do is do some study.

:laugh: Yeah, after god knows how many years in Cosmology I need to go do some syudy. Yep :laugh:

Just because you are incapable of understanding this stuff does not mean that you get to stand in the way of anyone else learning. You want to display your utter ignorance, go start a thread on it. Don't clutter up this thread.


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 Message 75 by john6zx, posted 11-04-2008 9:10 PM john6zx has responded

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cavediver
Member (Idle past 1898 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 83 of 131 (488255)
11-09-2008 6:51 AM


Back again, and let's first dispense with this nonsense...
Apologies for the long absence!

Ok, we were discussing the nature of time, and we had some rude interruptions questioning the nature of time, space, dimensions, etc. I should stress that these are extremely valid questions, and obviosuly deserve good answers in the context of this thread topic. However, the method of delivery revealed the lack of thought and prejudice behind the questioning, so it should be ignored as one should ignore moonshot-hoax merchants. They ask for evidence - numerous examples are given - and they continue as if nothing has been said. Neither are here to learn, but to promote their own egotistical arrogant viewpoints in contrast to that accepted by the world collection of scientists... but I digress :) I will start a new thread on this particular rant of mine.

Is space and time physical? Well, I have already introduced at least two meanings of time in this thread, so to which one are we referring? And what does 'physical' mean? That we can touch something? Well, what is 'touch'? etc, etc. I have explained this elsewhere at EvC but it is worth a recap.

john6zx reveals his classic pre-20th century view of existence - which admittedly is the viewpoint still held by 99.9% of the planet - that existence is made up of three things: physical 'things', invisible 'forces', and the arena of space which is merely where the 'things' can 'be'. Time was merely a way of accounting for change in the position or state of the 'things' (a viewpoint we still see in V-Bird's posts) 'things' are made up of atoms, and possibly atoms are further made up smaller 'thing'-like building blocks.

This all sounds reasonable and was how science viewed existence up until the late 19th Century. Electrons were discovered as even smaller 'things' and the plum pudding model of the atom was proposed - a ball of positively charged 'stuff' was impregnated with many negatively charged electrons, giving rise to a neutral atom. This still retains our basic 'thing' viewpoint of the physical. But soon Rutherford demonstrated that this was incorrect with his scattering experiements - he proposed a solar-system-like model, where a tiny positively charged nucleus is surrounded by even more tiny orbiting electrons. This is still a purely classical model. ***BUT*** it introduces the staggering result that suddenly, what we think of solid physical 'things' are not 'solid' at all, but consist of almost entirely empty space!!!

Suddenly we're back to our question of what is 'touch'? If 'things' are 99.99999999% empty space, why do they seem solid? Why do our hands not pass through each other when we clap? Clearly it isn't the 'things' - electrons and nucleus - that are giving rise to the solidity. It is actually the electromagnetic forces generated by those charged electrons. The reason you cannot pass your hands through each other is because of ELECTROSTATIC REPLUSION; not because of any sense of there being 'things' in the way or the common sense view of 'clearly things cannot pass through other things'. When you 'touch' something, all that is happening is that you are being pushed away from some area of space by electromagnetism. Switch off that electromagnetism, and your hands will happily pass straight through each other, just as with colliding galaxies, where the chances of any single pair of stars actually hitting each other is very remote.

Think about this and digest it for a while, as it is quite mind-blowing. And note that we haven't even begun to talk about quantum theory or relativity - this is purely experimental result and classical thinking, and already our concept of 'physical' is starting to change, as all those properties we thought of as unique to physical objects, are actually properties of those invisible forces. What we think of physical, tangible objects are just the net result of a web of atomic scale forces.

And this is only the beginning...

More to come.

Edited by cavediver, : No reason given.

Edited by cavediver, : No reason given.

Edited by cavediver, : No reason given.


Replies to this message:
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