Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
5 online now:
Newest Member: popoi
Post Volume: Total: 915,817 Year: 3,074/9,624 Month: 919/1,588 Week: 102/223 Day: 13/17 Hour: 0/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   The Big Bang Bamma
be LIE ve
Inactive Member


Message 16 of 80 (259806)
11-15-2005 1:38 AM
Reply to: Message 15 by Christian7
11-04-2005 7:17 PM


Re: I'm no expert
due to the nature of energy, and assuming matter is comprised of strings of energy, the universe could never be created or destroyed. as we have proven in thermodynaics research, energy is always conserved and simply changed in form. you cannot make, or destroy energy. because of this, the universe never began, and it will never end.
the best way to think of the big bang is as a massive change in state of a large part of eternally existant energy. i dont wanna fly off topic and get obscenely confusing, but thats the basic jist of the nature of things.

This message is a reply to:
 Message 15 by Christian7, posted 11-04-2005 7:17 PM Christian7 has not replied

Replies to this message:
 Message 17 by cavediver, posted 11-15-2005 4:52 AM be LIE ve has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 17 of 80 (259873)
11-15-2005 4:52 AM
Reply to: Message 16 by be LIE ve
11-15-2005 1:38 AM


Re: I'm no expert
the universe could never be created or destroyed.
Yes it could. You are trying to use local concepts to describe a global situation. Simple cons of energy arguments do not work. Or if you do want to talk that way, then the simplistic picture is that your "positive" energy is balanced by the effective "negative" energy of the universe's gravitational potential, giving the universe a total "energy" of zero.

This message is a reply to:
 Message 16 by be LIE ve, posted 11-15-2005 1:38 AM be LIE ve has not replied

  
Darkmatic
Inactive Member


Message 18 of 80 (259898)
11-15-2005 9:25 AM


Matter or energy cannot be created or destroyed , it can only change state , i.e. ejecting radiation of different types , but even then that radiation will still be present in the universe . Infact the only logical way i can see of matter being destroyed is if its sucked into a black hole . But then we don't even know what happends to matter once it enters a black hole , if it still exhists or is erased completely from the universe , or is ejected elsewhere from an opening .
However , at some stage in the universes life , all energy will have change state so that all we are left with is a dark universe of radiation flying around . This is one theory anyhow . But as for the actual universe being destroyed , i've never heard of any theories describing how the actual universe , the construct which contains all matter and antimatter could be physically destroyed .
(BTW , hello all , 1st post)

Replies to this message:
 Message 19 by cavediver, posted 11-15-2005 10:25 AM Darkmatic has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 19 of 80 (259909)
11-15-2005 10:25 AM
Reply to: Message 18 by Darkmatic
11-15-2005 9:25 AM


Matter or energy cannot be created or destroyed , it can only change state
As with my previous comments, this is a local statement. It doesn't actually mean a great deal wrt the universe as an entity. And of course, matter can be created and destroyed... pair creation and pair annihilation are the obvious examples of this: two photons can create an electron/positron pair. "before" there is no matter, only massless photons, and "afterwards" there are two massive objects, the electron and the positron. Energy has been conserved, but matter has not.
i've never heard of any theories describing how the actual universe , the construct which contains all matter and antimatter could be physically destroyed
Matter that falls into a black hole is eventually re-radiated from the black hole in the form of Hawking radiation. In a perpetually expanding universe, all of the black holes will eventually disappear as they radiate themselves to extinction.
Destruction is misleading (as is creation). Think instead of there being a maximum to the concept you call time, and that maximum occurs at a point in the universe.
BTW, welcome to EvC
This message has been edited by cavediver, 11-15-2005 10:26 AM

This message is a reply to:
 Message 18 by Darkmatic, posted 11-15-2005 9:25 AM Darkmatic has replied

Replies to this message:
 Message 20 by Darkmatic, posted 11-15-2005 11:10 AM cavediver has replied

  
Darkmatic
Inactive Member


Message 20 of 80 (259923)
11-15-2005 11:10 AM
Reply to: Message 19 by cavediver
11-15-2005 10:25 AM


Interesting , i wasn't aware of this pair creation or annihilation , although im not exactly up to date with my physics , last time i learnt any actual physics was in my final year of school 4 years ago .
I would like to learn more of this pair creation if you can direct me to a site explaining it , or even explain it yourself how this works .
As i said my understanding is grimm at best , but i was under the impression that there is more to an electron that just on single particle called the electron , it is made of other smaller particles , and thus the combination of photons to for an electron would seem possible and not to be creation but rather re-uniting of particles into a larger one which we call the electron .
I am probably wrong on this , but i have somehow come to the impression that electrons are made of smaller particles .

This message is a reply to:
 Message 19 by cavediver, posted 11-15-2005 10:25 AM cavediver has replied

Replies to this message:
 Message 21 by cavediver, posted 11-15-2005 12:50 PM Darkmatic has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 21 of 80 (259947)
11-15-2005 12:50 PM
Reply to: Message 20 by Darkmatic
11-15-2005 11:10 AM


An electron is not made up of smaller particles in the way that neutrons and protons are made up of quarks. It is the closest example of an actual "point" that we have. In fact it has no size at all at any length scale that we can probe! If you stare at an electron from a decent distance, it can appear to be particle like. But as you zoom in you realise that what appeared to be empty space surrounding the electron is actually a seething sea of activity of photons and other electrons! But you never manage to resolve the central point. So in a sense, what we think of as an electron is made up of other particles: photons and more electrons!!! Confused? The problem is that the everyday particle picture has broken down and you are now observing a quantum field, or actually, two interacting quantum fields: the Dirac field of the elctrons and the Bose field of photons.
Pair creation is just one of four identical processes: pair creation, pair annihilation, compton scattering and bremsstrahlung radiation. The only difference in each of these pictures is the direction of time wrt the interaction. Two electrons and two photons undergo an exchange. It can be two photons for two eletcrons (pair creation) two electrons for two photons (pair annihilation), an electron and a photon for an electron and a photon (compton and bremsstrahlung). There's no better demonstration of the simple 4d nature of space-time than the symmetry between these "different" interactions.
\                   /
         \                 /
       e+ \               / e-       Time ^
           \  e_v    ____/
            \____----    ~
            ~             ~
           ~               ~
          ~                 ~
         ~  Ph               ~ Ph
        ~                     ~
Oops, was going to do all four but outta time... sorry!

This message is a reply to:
 Message 20 by Darkmatic, posted 11-15-2005 11:10 AM Darkmatic has not replied

Replies to this message:
 Message 24 by cavediver, posted 11-15-2005 1:50 PM cavediver has not replied

  
Ragged
Member (Idle past 3552 days)
Posts: 47
From: Purgatory
Joined: 10-26-2005


Message 22 of 80 (259952)
11-15-2005 1:01 PM


More questions.
I have some questions too, if you dont mind.
11. What do they mean when they say that the universe is flat? For local geometry, I know that it means the curvature is zero very close to zero, because "ratio of average energy density of the universe over critical energy density as " and "=1 or alittle >1". (All qoutes taken from Wikipedia.) And they also say that that "Even if the universe is not exactly flat, the curvature is close enough to zero to place the radius beyond the horizon of the observable universe." What exactly does that mean? As I read on, I get more and more confused. I can't even begin imagining how it would look like in 3(?)-D.
I'm not very big on math, so please just explain it in plain english, if that is even possible.
12. This might be a silly question, but is there a center of the universe? If we assume that Big Bang is true, and that the universe started out as a singularity and that it will eventually shrink and become a singularity and so on, then there should be a center. Like if we inflate a baloon, then we find it's center, then when we deflate it (or increase the pressure around the baloon), it will eventually become a small ball of rubber in the place where the center of the inflated baloon used to be. Given that the baloon is homogenious on the inside and made out of the same material etc.
Hubble's law says something about the objects red-shift being proportional to the obfect's distance. I heard it being interpreted as accelerating rate of expansion of the universe as the objects get farther away. But further away from what? Does it mean that we are at the center of all things? Or does it have something to do with universe being isotropic, so then it wouldn't metter where you are or what direction you are facing.
Does this question even make sence from the GR point of view or is it one of the "beyond the universe" or "before time" type of thoughts?
I've read a few threads about it on this forum and did some extra reading elsewhere on the internet, but I lack good footing in the subject. I think its a real cool theory and I'd like to learn more.

Replies to this message:
 Message 23 by cavediver, posted 11-15-2005 1:31 PM Ragged has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 23 of 80 (259962)
11-15-2005 1:31 PM
Reply to: Message 22 by Ragged
11-15-2005 1:01 PM


Re: More questions.
Ok, quickly for now...
Take a closed FRW universe - i.e. normal big bang, with <1. It has curvature. If you measure the circumference of circles that you draw around yourself, you will find they are less than 2piR. However, if there is a period of inflation, the inflated universe's curvature will be much much less. Cosider the curvature of a balloon... you can see it. Blow it up to the size of the Earth and it's no longer so obvious. You measure curvature by quoting the radius of a sphere that would match the curvature. So the curvature of the Earth's surface rather obviously has a radius of curvature of the Earth's radius! So that should explain what they mean when they say the radius of curvature of the universe is so large that it is pretty much flat. Now if >1, you don't have sphere, you have a pseudo-sphere (great fun to visualise ) but the same flattening occurs under inflation. This is how the universe finds itself so finely tuned to flatness... according to inflation anyway.
is there a center of the universe?
No, there is not. The balloon is the rubber surface, not the space inside. Same with the universe. It is the surface that matters, except that the surface is 3d. This is child's play to a mathematician as one of the first things they learn is that a sphere is a 2d object, not 3d. It is the surface that matters. There is no inside. The sphere can be defined without any reference to a 3d embedding space. The inside does not exist! There is no spoon...
But further away from what?
From us. And every other point in the universe. Think of the balloon blowing up and all the points on the surface stretching away from each other.
Does it mean that we are at the center of all things?
Only as much as every other point in the universe is also at the centre.
Does this question even make sence from the GR point of view or is it one of the "beyond the universe" or "before time" type of thoughts?
This makes perfect sense from GR. It is GR that dictates this fact to us. There is nothing else that gives a concept of topology to the universe.
I think its a real cool theory and I'd like to learn more.
Good This is not even scratching the surface...
This message has been edited by cavediver, 11-15-2005 01:32 PM

This message is a reply to:
 Message 22 by Ragged, posted 11-15-2005 1:01 PM Ragged has replied

Replies to this message:
 Message 25 by Ragged, posted 11-15-2005 3:43 PM cavediver has replied
 Message 27 by bkelly, posted 11-15-2005 9:32 PM cavediver has replied
 Message 33 by Tony650, posted 11-16-2005 8:59 AM cavediver has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 24 of 80 (259966)
11-15-2005 1:50 PM
Reply to: Message 21 by cavediver
11-15-2005 12:50 PM


Thought I'd add these for completeness...
~                     ~
              ~                   ~
               ~                 ~
             Ph ~               ~ Ph       Time ^
                 ~  e_v    ____~
                  ~____----    \
                  /             \
                 /               \         Pair annihilation
                /                 \
               / e-                \ e+
              /                     \

and

             ~                     /
              ~                   /
               ~                 /
             Ph ~               / e-       Time ^
                 ~  e_v    ____/
                  ~____----    ~
                  /             ~
                 /               ~         Compton scattering
                /                 ~
               / e-                ~ Ph
              /                     ~
Ph photon
e- electron
e+ positron
e_v virtual electron
This message has been edited by cavediver, 11-15-2005 08:25 PM
This message has been edited by cavediver, 11-15-2005 08:40 PM

This message is a reply to:
 Message 21 by cavediver, posted 11-15-2005 12:50 PM cavediver has not replied

  
Ragged
Member (Idle past 3552 days)
Posts: 47
From: Purgatory
Joined: 10-26-2005


Message 25 of 80 (259994)
11-15-2005 3:43 PM
Reply to: Message 23 by cavediver
11-15-2005 1:31 PM


Re: More questions.
I might be misunderstanding the concept of the term "radius". Ever since I can remember radius was distance from the ourter edge directrly to the center. How can a strait line have curvature?
I think I understand why they say the universe is flat. But then its only flat from our perspective, right? If there was a being so large, looking at the universe from the "outside", for that being our universe could be a perfect sphere and have a very definite and positive curvature.
"From us. And every other point in the universe. Think of the balloon blowing up and all the points on the surface stretching away from each other."
OK. I understand that. But I'm still not entirely clear about Hubble's law.
"Any two points which are moving away from the origin, each along straight lines and with speed proportional to distance from the origin, will be moving away from each other with a speed proportional to their distance apart."
So it just says that with time the universe is expandinig at a faster rate, and all the objects within the universe get further away from each other at a faster rate and so on. I guess it explains that there is no center for that purpose.
"However, the best way to calculate the recessional velocity and its associated expansion rate of spacetime is by considering the conformal time associated with the photon traveling from the distant galaxy.That is Hubble's law."
I guess that the term "distance" mislead me into wondering "where from" and "to what". In my mind, "conformal time" seems to explain it better. I think I'm starting to understand.
"No, there is not. The balloon is the rubber surface, not the space inside. Same with the universe. It is the surface that matters, except that the surface is 3d. This is child's play to a mathematician as one of the first things they learn is that a sphere is a 2d object, not 3d. It is the surface that matters. There is no inside. The sphere can be defined without any reference to a 3d embedding space. The inside does not exist! There is no spoon..."
OK, gotcha.
But, if we take a balloon and measure its circumference, or diameter, we could find its center, or really the center of the sphere of air that the balloon surounds. So could there be an imaginary center of the universe, or space within the universe?
P.S: Those graphs don't make any sense to me. I don't even know what they are of.
This message has been edited by Ragged, 11-15-2005 03:45 PM

"I may disagree with what you have to say, but I shall, to the death, defend your right to say it" ~ Voltaire

This message is a reply to:
 Message 23 by cavediver, posted 11-15-2005 1:31 PM cavediver has replied

Replies to this message:
 Message 26 by Funkaloyd, posted 11-15-2005 8:31 PM Ragged has not replied
 Message 35 by cavediver, posted 11-16-2005 1:15 PM Ragged has not replied

  
Funkaloyd
Inactive Member


Message 26 of 80 (260038)
11-15-2005 8:31 PM
Reply to: Message 25 by Ragged
11-15-2005 3:43 PM


The expansion of the Universe
Ragged writes:
with time the universe is expandinig at a faster rate, and all the objects within the universe get further away from each other at a faster rate and so on.
It's not so much to do with time as distance. On the line below, the numbers represent galaxies, and the dashes represent a unit of distance in the space between the galaxies. Together, the numbers and dashes are the Universe.
1---2---3---4---5
Now, if space expands by eight dashes over some period of time, the Universe will look like this:
1-----2-----3-----4-----5
Notice that galaxy 5, which was always far from galaxy 1, is now eight units of space farther from galaxy 1; but galaxy 2, which was rather close to galaxy 1 to begin with, is now only two units of space farther from galaxy 1.
So with time any two galaxies in the Universe will go away from each other at a faster rate, but it's the distance which determines that rate.

This message is a reply to:
 Message 25 by Ragged, posted 11-15-2005 3:43 PM Ragged has not replied

  
bkelly
Inactive Member


Message 27 of 80 (260076)
11-15-2005 9:32 PM
Reply to: Message 23 by cavediver
11-15-2005 1:31 PM


No center?
Cavediver,
As I read your post, there is no center of the universe.
The center of the universe is the spot in which the big bang occured. In theory, I think that spot could be identified in several ways. Measure the red shift of all the galaxies in all directions and plot some averages and histograms. Move a billion or two light years to the left, right, up, down etc and do the same a few times. I have not thought this all the way through but it seems that a center could be found.
Galaxies further from the center are moving faster that those closer to the center. That is whey they are further away. Find the place where the galaxies are moving away at the slowest rate and that should be the center.
Find the place where the average speed of all of the galaxies to the "left" (any arbitrary direction) is the same as all of those to the right (the opposite direction) and you have the center.

This message is a reply to:
 Message 23 by cavediver, posted 11-15-2005 1:31 PM cavediver has replied

Replies to this message:
 Message 28 by cavediver, posted 11-15-2005 9:00 PM bkelly has replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 28 of 80 (260052)
11-15-2005 9:00 PM
Reply to: Message 27 by bkelly
11-15-2005 9:32 PM


Re: No center?
The center of the universe is the spot in which the big bang occured
Then every point is the centre. Every point in space was "born" in the big bang. In a finite closed big bang scenario, all of those points were coincident.
Galaxies further from the center are moving faster that those closer to the center. That is whey they are further away. Find the place where the galaxies are moving away at the slowest rate and that should be the center.
You will find that this is true for every point in the universe. Every point thinks it is the centre because everything is moving away from it, with a speed proportional to the distance.
Find the place where the average speed of all of the galaxies to the "left" (any arbitrary direction) is the same as all of those to the right (the opposite direction) and you have the center.
Again, you will find this true for every point in the universe!
Think of the balloon analogy. Every point on the balloon skin thinks that every other point is moving away radially as the balloon inflates, so concludes that it is the centre of expansion of the balloon. But we can see from our vantage that there is no centre on the balloon surface.

This message is a reply to:
 Message 27 by bkelly, posted 11-15-2005 9:32 PM bkelly has replied

Replies to this message:
 Message 29 by GDR, posted 11-16-2005 12:35 AM cavediver has replied
 Message 37 by bkelly, posted 11-16-2005 7:37 PM cavediver has replied

  
GDR
Member
Posts: 6202
From: Sidney, BC, Canada
Joined: 05-22-2005
Member Rating: 1.9


Message 29 of 80 (260104)
11-16-2005 12:35 AM
Reply to: Message 28 by cavediver
11-15-2005 9:00 PM


Re: No center?
Using the analogy of the balloon, does it make any sense to consider the distance from the center of the ballon to the surface as depicting time?
It seems to me that the 2 dimensional surface of the ballon that represents the 3d universe inflates in porportion to the time involved which, using the analogy, is represented by the radius of the inside of the ballon.
Thanks

This message is a reply to:
 Message 28 by cavediver, posted 11-15-2005 9:00 PM cavediver has replied

Replies to this message:
 Message 30 by cavediver, posted 11-16-2005 3:56 AM GDR has not replied

  
cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 30 of 80 (260129)
11-16-2005 3:56 AM
Reply to: Message 29 by GDR
11-16-2005 12:35 AM


Re: No center?
You can think that way but it doesn't really help. It's stretching the analogy a little too far. Instead of a picture of 3d space as a surface, you want to jump to a picture of 4d space-time as a surface. Remember my globe analogy that I use frequently? North pole - big bang, South pole - big crunch. Our balloon has been reduced to a circle, a circle of latitude. The balloon inflating is now the circle of latitude growing as you move south from the north pole. Time is distance along the line of longitude. Again, inside the globe has no meaning.

This message is a reply to:
 Message 29 by GDR, posted 11-16-2005 12:35 AM GDR 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