The Naked Scientists

The Naked Scientists Forum

Author Topic: What is the evidence that the Universe is expanding?  (Read 12805 times)

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #25 on: 19/11/2013 22:08:57 »
Thanks for the one to one explanation :) it infinitely helped  ;D
« Last Edit: 19/11/2013 22:11:15 by barneyboy »
 

Offline Ethos_

  • Neilep Level Member
  • ******
  • Posts: 1277
  • Thanked: 14 times
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #26 on: 19/11/2013 23:54:03 »


Please bare with me on this next bit.
one theory of the big bang, so ive read, is that two "wavy branes" of a multiverse touched and at the point that they touched our universe was created. two ultra massive bodys with masses of energy released matter and energy in an instant to create our universe. now the branes are pulling apart again and their drawing their energys and matter back out at the point that they first touched.
an unimaginable force inflating then deflating our universe.

Interesting thought barney..............

At present, we suspect the increase in expansive velocity is being caused by the presence of dark energy. Notice,.........I use the word "Suspect" because we still don't understand much about this phenomenon. Not only don't we know much about dark energy, we don't have a good explanation for why it should even exist. So......, until we do, using the term "dark energy" has very little to do with the scientific method, repeatable experimental results. I submit that at present, using the term "dark energy" should be classified as merely a hypothesis and not a theory. Likewise, your estimation of this phenomenon is also lacking in the scientific method. Nevertheless, your thoughts are intriguing.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #27 on: 22/11/2013 05:09:58 »
Since so many people are so easily confused by the concept of expanding space, even when the balloon analogy is used, that I took that  balloon analogy and simplified it. Since the  balloon analogy relies on two particles moving on a great circle I looked only at the circle and created a page called the The Circle Universe which is now at
http://home.comcast.net/~peter.m.brown/gr/circle_universe.htm

The purpose of this page was to show how a calculation like this is done in lower dimensions. Please keep in mind that this is the balloon analogy, just looking at a slice of the balloon on which two particles are moving on.

Noitice the resulting equation Eq. (2). It shows that the relative speed of two "galaxies" depends on their (angular) seperation. The angular coordinates are referred to as comoving coordinates.
« Last Edit: 22/11/2013 05:14:19 by Pmb »
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #28 on: 02/12/2013 22:39:23 »
I don't know what your equations mean but if I get your explanation then what your saying is that as points b, and c, move away from their original start point a, the distance increases but at the same time the distance between b, and c, also increases showing that they must be expanding. But if I have understood that correctly then there would only be a red shift in the universe and if there was only a red shift in the universe, there would not be galaxy's crashing into each other and the Andromeda galaxy would not be aiming to take a chunk out of the milky way as if they were getting closer then there would be a blue shift here and there and if there was a blue shift here and there then b, and c, could be heading back towards a, even if d, and e, was not.
 
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #29 on: 06/12/2013 23:19:32 »

[/quote]
The universe coming out of a single point is not part of the big bang theory (BBT). The BBT can only traced back so far and then we donít know what happened before that.

Physicists used to believe that the universe might stop expanding and reverse to a big crunch. That was only one of the possibilities. Now that it appears  that the universe is expanding at an accelerating rate that does not seem possible.
[/quote]



Quote from: barneyboy
My thought is that at the same point that the big bang occurred so to could the big crunch, a point in space that is pulling all matter back to its origin therefor stretching space back towards its origin, keeping the redshift intact.
There is no place in the universe like that. People get the wrong idea quite often that the big bang occured at a particle point in spacel which is not true.
[/quote]



I'm sorry, I didn't realise that this had been proven as a scientific fact rather that an unproven theory
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #30 on: 07/12/2013 04:19:34 »
Quote from: barneyboy
I don't know what your equations meanÖ
What is the problem that youíre having understanding them. If you explain that then Iíll help you understand what they mean.

Quote from: barneyboy
.. but if I get your explanation then what your saying is that as points b, and c,Ö
What are the points b and c that youíre talking about?
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #31 on: 07/12/2013 16:56:01 »
My thought is that at the same point that the big bang occurred so to could the big crunch, a point in space that is pulling all matter back to its origin therefor stretching space back towards its origin, keeping the redshift intact.
Quote from: pmb
There is no place in the universe like that. People get the wrong idea quite often that the big bang occured at a particle point in spacel which is not true.
I'm sorry, I didn't realise that this had been proven as a scientific fact rather that an unproven theory
The point is that current big bang theory is about the expansion of spacetime itself, not like an explosion that occurs within some greater space. The whole universe was very dense and hot, and the whole universe is expanding from that condition. This idea fits what we see now very well. The idea of there being some point in space where the expansion began does not fit well with what we observe, and the maths doesn't work out.

Science doesn't really generate 'proven scientific facts'; theories are provisional explanatory models, open to refinement or replacement. Newtonian physics was a pretty good fit with observation, but Einstein's relativity is even better. The current big bang theory is not the whole story, but it's hard to see how a 'one point in space expansion' theory could be made to fit.
 

Offline Ethos_

  • Neilep Level Member
  • ******
  • Posts: 1277
  • Thanked: 14 times
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #32 on: 07/12/2013 18:27:51 »
Science doesn't really generate 'proven scientific facts'; theories are provisional explanatory models, open to refinement or replacement. Newtonian physics was a pretty good fit with observation, but Einstein's relativity is even better. The current big bang theory is not the whole story, but it's hard to see how a 'one point in space expansion' theory could be made to fit.
Good explanation dlorde, and the casual scientific observer only see's portions of the whole picture. It is becoming more popular among physicists today to talk about concepts like The Bulk. The Bulk refers to what some might call Hyperspace where many different universes could exist. This lends support to understanding how our particular universe could be expanding with it's occupants riding along as on the surface of an expanding balloon with no central point of expanding origin. Unlike the former concept of unlimited space, this idea places our finite universe within an infinite Hyperspace where many different universes could possibly exit. There would be of course no opportunity for adjacent universes to ever communicate with each other because escape from any such individual time/space continuum could not be possible.
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #33 on: 07/12/2013 20:08:03 »
Hi PMB
Quote from: barneyboy
I don't know what your equations meanÖ
What is the problem that youíre having understanding them. If you explain that then Iíll help you understand what they mean.

you equations seem simple to you and your esteemed academics but to me the are complex and alien , this does not mean im thick, it means that I have not been trained to understand them, that is why I asked for simplistic terms on explanations.  My analogies, to me seem very simple yet you do not seem to get them because they are alien to you and yet I think that they both can show the same result.
Quote from: barneyboy
.. but if I get your explanation then what your saying is that as points b, and c,Ö
What are the points b and c that youíre talking about?


I meant that if you wrote the letter b, and the letter c, on the surface of a rubber balloon and then inflated that balloon not only would they move away from the mouth piece (lets call that a,) but b, and c, will also move away from each other
« Last Edit: 07/12/2013 21:05:35 by barneyboy »
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #34 on: 07/12/2013 20:46:28 »
Hi Dlorde
I apologise, I don't get what you mean "The whole universe was very dense and hot, and the whole universe is expanding from that condition".
why is that statement different from the universe expanding from a single point.
"IF" the universe is expanding, then it was smaller to start with, either as a infinitely small and infinitely dense point that went bang or as a huge dense point that went bang.
or do you mean that the physical size of the "shell"of the universe is fixed and the hot dense material held within as it cools and coagulates into galaxy's then the more space would be created between galaxy's creating the red shift.
if you started with a set amount of space that could not either increase or decrease, lets say a 1 litre bottle and in that bottle was 1 litre of hot dense gas. as the gas cools it turns into different liquids that seperate so it doesn't take up as much space as the gas, but as the bottle cannot shrink, so some space is created. Then as the liquids turn into solids they take up even less space therefore creating MORE space because yet again the "universe" bottle cannot change size. you would end up with a 1 litre volume bottle and 1 litre of matter and a vacuum of space that had being created had this been in zero gravity then the little lumps of coagulated solids would have show an increase of space between them without the need for inflation or dark matter.
 
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #35 on: 07/12/2013 21:03:13 »

hi ethos
[/quote]. There would be of course no opportunity for adjacent universes to ever communicate with each other because escape from any such individual time/space continuum could not be possible.
[/quote]
why, of course, and how can you be so sure that it would not be possible. Are you that sure that we (you rather than me) have such a good grasp on all things physicy that you can say with no doubt that this is a science FACT and not "Science doesn't really generate 'proven scientific facts'; theories are provisional explanatory models, open to refinement or replacement"
(this one could be messy :o) sorry)
 

Offline Ethos_

  • Neilep Level Member
  • ******
  • Posts: 1277
  • Thanked: 14 times
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #36 on: 07/12/2013 21:27:15 »

hi ethos
Greetings barney.........

Quote from: barneyboy
why, of course, and how can you be so sure that it would not be possible.
Nothing is an absolute surety barney, but there is some evidence to support these possibilities.
 

Offline barneyboy

  • Jr. Member
  • **
  • Posts: 45
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #37 on: 07/12/2013 21:49:55 »
I didn't mean about the bulk theory, I meant regarding the cross universe communication.
Quote from: Ethos_ link=topic=49485.msg425933#msg425933 date=1386440871
[/quote
There would be of course no opportunity for adjacent universes to ever communicate with each other because escape from any such individual time/space continuum could not be possible.]
Quote
why would it not be possible to escape individual time/space continuum.
 

Offline Ethos_

  • Neilep Level Member
  • ******
  • Posts: 1277
  • Thanked: 14 times
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #38 on: 07/12/2013 22:05:10 »

why would it not be possible to escape individual time/space continuum.
Even though travel thru a Worm Hole may be theoretically possible someday in the very distant future, travel outside of our universe is thought by just about every credible scientist to be impossible. Travel by means of shortcut wormhole method is only theoretically possible within our own universe. And as we speak, there remains no method by which this journey outside our universe is thought possible.
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #39 on: 07/12/2013 22:33:15 »
I apologise, I don't get what you mean "The whole universe was very dense and hot, and the whole universe is expanding from that condition".
why is that statement different from the universe expanding from a single point.
As I understand it, at the big bang, the universe was arbitrarily large (possibly infinitely large). Since that time, it has expanded. It's reasonable to say that the currently observable universe would have been extremely small, but the observable universe is probably only part of the whole universe.

Quote
"IF" the universe is expanding, then it was smaller to start with, either as a infinitely small and infinitely dense point that went bang or as a huge dense point that went bang.
OK - in physics (geometry), a point has no size, so you can't have a 'huge' point. If you're saying the universe may have been huge, very hot, and very dense, then expanded rapidly, that's basically what I'm saying - although I don't think it is believed to have been infinitely dense.

Quote
... do you mean that the physical size of the "shell"of the universe is fixed and the hot dense material held within as it cools and coagulates into galaxy's then the more space would be created between galaxy's creating the red shift.
No. Not sure what you mean by 'physical shell', but the physical size of the universe is expanding, and every point in it is moving away from every other point, so the distance between objects generally increases over time except where some force holds them together.
 
Quote
if you started with a set amount of space that could not either increase or decrease, lets say a 1 litre bottle and in that bottle was 1 litre of hot dense gas. as the gas cools it turns into different liquids that seperate so it doesn't take up as much space as the gas, but as the bottle cannot shrink, so some space is created. Then as the liquids turn into solids they take up even less space therefore creating MORE space because yet again the "universe" bottle cannot change size. you would end up with a 1 litre volume bottle and 1 litre of matter and a vacuum of space that had being created had this been in zero gravity then the little lumps of coagulated solids would have show an increase of space between them without the need for inflation or dark matter.
Possibly; but that's not a realistic model for the big bang universe.The universe is a closed system, it can only cool by expansion, and a history of that is what we see when we look out there. The current big bang model was developed to account for what we actually observe.
« Last Edit: 07/12/2013 22:35:01 by dlorde »
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #40 on: 07/12/2013 23:44:07 »
Quote from: dlorde
As I understand it, at the big bang, the universe was arbitrarily large (possibly infinitely large).
I disagree. Where did you get that idea from?

Quote from: dlorde
OK - in physics (geometry), a point has no size, so you can't have a 'huge' point.
I believe that he was talking about a dynamical property of the point, not the size of the point.
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #41 on: 08/12/2013 00:32:57 »
Quote from: dlorde
As I understand it, at the big bang, the universe was arbitrarily large (possibly infinitely large).
I disagree. Where did you get that idea from?
Stuff I've read in various places. Some say it may have been infinite, others that it was finite in size, but that the observable universe is likely only part of a larger whole. From my reading, most don't think that it was an infinitesimal size. So if it wasn't infinitesimally small, it was either infinite or some other size. YMMV.

Quote
Quote from: dlorde
OK - in physics (geometry), a point has no size, so you can't have a 'huge' point.
I believe that he was talking about a dynamical property of the point, not the size of the point.
I don't understand - in what sense can a point be huge?

Oh wait - do you mean that he meant 'hugely dense'? If so, I wouldn't argue with that.
« Last Edit: 08/12/2013 00:40:00 by dlorde »
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #42 on: 08/12/2013 03:07:42 »
[
Quote from: dlorde
I don't understand - in what sense can a point be huge?

Oh wait - do you mean that he meant 'hugely dense'? If so, I wouldn't argue with that.
Yes. Thatís exactly it. In fact thatís what he was talking about, i.e. a huge mass density. If itís actually a point then the mass density would be infinite.

Think of the difference in mass between an electron and a muon. The masses are finite yet they have no size.
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #43 on: 08/12/2013 10:05:40 »
Think of the difference in mass between an electron and a muon. The masses are finite yet they have no size.
Hmm; I know in they're treated as 'point particles' in QM, but it seems debatable whether they have spatial extent - in classical relativistic physics they have a classical radius, e.g. as used in Thomson Scattering calculations; in quantum field theory, they're excitations of a field - does size have meaning for that? It seems to me that both cases are abstract models for whatever is 'really' there... I suppose it depends how you look at it.

 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #44 on: 08/12/2013 11:19:23 »
Quote from: dlorde
Hmm; I know in they're treated as 'point particles' in QM, but it seems debatable whether they have spatial extent - in classical relativistic physics they have a classical radius, e.g. as used in Thomson Scattering calculations; in quantum field theory, they're excitations of a field - does size have meaning for that? It seems to me that both cases are abstract models for whatever is 'really' there... I suppose it depends how you look at it.
What is it about the electron being a truly point particle that bothers you? It's my understanding that the electron is truly a point particle.

Suppose we were to model the electron as a classical solid sphere or radius r, mass m, with angular momentum hbar/2. If we assumed that the classical electron radius was less than r = 10^(-16) cm then the sphere would be rotating with points on the surface moving faster than the speed of light. Faster if the radius was smaller. It we require the spinning electron model to hold then we know this canít work.
« Last Edit: 08/12/2013 11:38:38 by Pmb »
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #45 on: 08/12/2013 11:34:47 »
Suppose we were to model the electron as a classical solid sphere or radius r, mass m, with angular momentum hbar/2. If we assumed that the classical electron radius was less than r = 10^(-16) cm then the sphere would be rotating with points on the surface moving faster than the speed of light. Faster if the radius was smaller. It we require the spinning electron model to hold then we know this canít work.
Yes, of course we know that macro-scale concepts don't really apply; electrons aren't little billiard balls rotating, but sometimes size, spin and angular momentum, etc., are useful metaphors for how they seem to behave, and sometimes not; sometimes we have to treat them like waves. Sometimes familiar names are given to properties that are nothing like their macro-scale namesakes, e.g. 'spin', 'color', 'flavor', etc.
 

Offline Pmb

  • Neilep Level Member
  • ******
  • Posts: 1838
  • Physicist
    • View Profile
    • New England Science Constortium
Re: What is the evidence that the Universe is expanding?
« Reply #46 on: 08/12/2013 19:02:10 »
Quote from: dlorde
Yes, of course we know that macro-scale concepts don't really apply; electrons aren't little billiard balls rotating, but sometimes size, spin and angular momentum, etc., are useful metaphors for how they seem to behave, and sometimes not; sometimes we have to treat them like waves.
Thatís not quite an accurate statement. Point particles are not treated like waves. There is only a wavelike property associated with their behavior. By this I mean that they have a property which gives rise to probability distribution. That means that there is a distribution of where theyíre detected given an ensemble of particles or measurements.
 

Offline dlorde

  • Neilep Level Member
  • ******
  • Posts: 1441
  • Thanked: 9 times
  • ex human-biologist & software developer
    • View Profile
Re: What is the evidence that the Universe is expanding?
« Reply #47 on: 08/12/2013 21:45:05 »
Quote from: dlorde
Yes, of course we know that macro-scale concepts don't really apply; electrons aren't little billiard balls rotating, but sometimes size, spin and angular momentum, etc., are useful metaphors for how they seem to behave, and sometimes not; sometimes we have to treat them like waves.
Thatís not quite an accurate statement. Point particles are not treated like waves. There is only a wavelike property associated with their behavior. By this I mean that they have a property which gives rise to probability distribution. That means that there is a distribution of where theyíre detected given an ensemble of particles or measurements.
It's accurate enough to make the point; they have both wave-like properties and particle-like properties, as professor Norton explains.
 

The Naked Scientists Forum

Re: What is the evidence that the Universe is expanding?
« Reply #47 on: 08/12/2013 21:45:05 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums