The size of the universe... scaled

[Alasdair]

The other day I was playing around with scaled versions of the universe, and I ended up writing some of it up here:

http://numbersandshapes.net/?p=2736

The exercise certainly gave me a better appreciation of the size of the damned thing!

-A.

[Eratosthenes]

Universe/human size ratio

Human/Planck length size ratio

The latter is many orders of magnitude greater. There seems to be MORE in the world that is smaller than us than there is in the world that is larger than us

[Alasdair]

You're quite right! The diameter of the known universe is about 10^26 metres; Planck length is about 10^(-35) metres. However, Planck length is a theoretical construct only. The smallest measurement so far made (at the LHC) is about 10^(-18)m. On the other hand, the Universe is not only expanding but accelerating, and depending on the precise values of Hubble's constant and the Cosmological constant; which are currently unknown, may yet increase by many orders of magnitude.

[julianh72]

"A human is halfway in size between an atom and the known universe"
http://ask.metafilter.com/57214/A-Problem-of-Scale-Halfway-in-size-between-an-atom-and-the-universe

[ZeroID]

I always suspected we were a bit average ... :P

[Weltevreden SA]

There's a well-illustrated version of this with a scale slider here:

http://www.htwins.net/scale2/

Note the very useful log scale in meters in the lower right corner.

=Dana

[julianh72]

There's a great movie called "Powers of Ten" from 1977: https://www.youtube.com/watch?v=0fKBhvDjuy0

It "only" goes out to 10^24 metres (100 million light years), but a bit of quick maths tells you that the scale of the observable universe is "only" about two orders of magnitude bigger (10^26 metres or ~10 billion light years).

10^0 metres (= 1 metre) is the order of magnitude of a human being.

The movie then zooms in to 10^-10 metres (the scale of an atom), 10^-14 metres (the size of a proton), and finishes at 10^-16 metres, where you're getting down towards the scale of the most fundamental theoretical particles.

9 minutes that everyone should watch!

[Eratosthenes]

Interesting how the typical estimate of the size of the universe is in the 90 billion light year vicinity and yet the Big Bang has been estimated to have occurred 13.7 billion light year ago. ;)

Is the universe expanding at greater than the speed of light folks?

Is this a spatial illusion?

Is this a contradiction?

;)

[sjastro]

Space can expand faster than light.
The Universe has also expanded in the 13.7 billion years it has taken for the most distant photons to reach us.

Regards

Steven

[Eratosthenes]

....then we have the Variable Speed of Light (VSL) theorists like Magueijo and Albrecht who claim that the speed of light is not a constant over long time scales. Indeed, Magueijo estimates that the speed of light was higher in the early stages of the Universe post Big Bang, in fact over 3 orders of magnitude faster than it is now.

So when exactly did the Big Bang occur? ;)

[sjastro]

Obviously 13.82 billion years ago give or take or few hundred million years. It is pointless to have a theory that is contradicted by observation such as Planck's data of the CMB.
One can fine tune the theory so that it agrees with observation.

Magueijo and Albrecht's paper (http://arxiv.org/pdf/astro-ph/9811018v2.pdf) deals with a variable speed of light as a substitute for Inflationary theory in dealing with the horizon and flatness issues in cosmology.

The paper doesn't attempt to overthrow BB cosmology but addresses the inflation epoch which lasted from 10^-36 to 10^-32 seconds after the BB.
Occams razor has some relevance here.
Cosmology is hard enough as it is without having to introduce complications such as the speed of light varying, in particular as to why it happens.

The speed of light in a vacuum is one of the very few physical constants in nature where theory predicts its value.
This was achieved by Maxwell in the 19th century.

Steven

[Eratosthenes]

The wave equation can be reduced to first order wave equation terms traveling in opposite directions which clearly shows propagation at a constant c

.....provided μ0 and ϵ0 are constant ;)

When do μ0 and ϵ0 become non constant tensors?;)

many people prefer to state that the speed of light is invariant under a Lorentz transformation.;)

[sjastro]

I note the blatant use of Gish Gallop tactics here.

It's no coincidence that μ0 and ϵ0 are termed physical constants so why should they vary?
The speed of light has been measured for over 300 years and no one has found the speed of light to be dependant on the motion of the observer, so why should it not be invariant under a Lorentz transformation?

Since you are the one making the claims the onus is on you to make the case.

Show me
(1) The theoretical aspects that show μ0 and ϵ0 are not constant and the speed of light is not invariant.
(2) Supporting experimental evidence.

No quote mining please.

Steven

[Eratosthenes]

Philosophically I am uncomfortable with the notion of "constants"

Lets take μ and ϵ in a "moving media" scenario. If one digs deeper into how the waves look like from particle to particle the development of the wave equation becomes a little more complex. We need to examine the interaction of light with the first moving particle and then relate that to light interaction with the second particle. The second particle has a different relative speed. So how do we derive the equations for this case in point? Well, not only do we need equations for media, but also for moving media where μ and ϵ are tensors and therefore not constant.

But as I said I dont believe in constants - they are illusions of logic, and numerical conveniences. Science is a very effective and efficient religion. Perhaps the most impressive religious tool developed by humans so far.

In 190 BC, Eratosthenes has certainly developed a long lasting tool for the priests of the Scientific religion to use in their temples and laboratories.

[Alasdair]

Well, I'm a mathematician and not a physicist, and so I'm entirely happy with the notion of constants!

I had also thought that the speed of light was constant, from every observer and in every frame of reference - as far as I understand, that's one of the cornerstones of relativity. (But see next paragraph.)

The universe is indeed bigger than we can see, simply because the stretching of space means that distant objects have been able to move further away than the distance light could reach us since the big bang. And this doesn't contradict relativity's "nothing can travel faster than light" notion, because the velocity of light, and velocity in general, relativistically speaking, is a local property. When expansion of space is considered, the whole notion of "velocity" alters.

Apparently the size of the universe (as opposed to the observable universe), is reckoned to be in the order to 10^23 times bigger.

That's quite enough Deep Thought for 12.20am.

[Eratosthenes]

Its very common for these deep thoughts to emerge in the wee hours.

10^23 times bigger?

[Slawomir]

LOL

Then perhaps, as a result of laziness and other factor, too many blindly believe in it without questioning, while too few actually practice it.

[sjastro]

ϵ and μ are nothing more than conversion constants.
They arise from the inverse square law force between electric charges, and the force between parallel wires carrying a current respectively.

Since force is expressed in Newtons, charge in Coulombs and distance in metres, the inverse square law has a unit mismatch between the left and right hand side of the equation, ϵ is introduced into the right hand side of the equation so that both sides are expressed in terms of force.

The same principles apply to μ.

While ϵ and μ are termed "physical" constants both in fact are measurement system constants.
They cannot be measured in an experiment nor do they describe the physical properties of an electromagnetic wave in a vacuum.
It is therefore totally meaningless to claim ϵ and μ change due to the interaction of electromagnetic waves with particles.

The interaction of light in a highly rarefied vacuum is based on the science of scattering.
Since light has a wave/particle duality, scattering is understood by treating light as a particle, in this case a photon.
When a photon is scattered by a particle it can either lose or gain energy.
The photon continues to travel at c but the wavelength or frequency of the photon changes.



Anyone who states science is a religion doesn't understand science.
Isn't it strange for a religion to constantly undergo revaluation through experiment and observation.

Steven

[Weltevreden SA]

Steven wrote, "Space can expand faster than light." This is oft-said and not-so oft explained. Why should space have a property which is essentially nonphysical until something physical expands to occupy it? Why, too, did space abruptly expand at at specific point in time, achieve the expansion velocity that it did, and slow to approx its present rate at a point in time so briefly after it began? What set the initial and ending boundaries? These issues have been floating without definition in my awareness for some time and this is a good occasion to address them. They are also very relevant: I’m comparing data re today’s cosmic matter-energy inventory (Fukugita et al (http://arxiv.org/abs/astro-ph/0406095v2)) and Brian Lacki’s “CMD” of the energy sky (http://arxiv.org/abs/1004.2049) (Fig 4), with a recent group of papers devoted to the properties of cosmic voids and filaments, Rieder (http://arxiv.org/abs/1307.7182), Alpaslan (http://arxiv.org/abs/1401.7331), Tempel (http://arxiv.org/abs/1502.02043), Libeskind (http://arxiv.org/abs/1503.05915). These introduce important issues, e.g., the large- to small-scale granularity of the products of inflation. But I note that all of these and others I’ve come across interpret space in terms of the interaction of mass density and energy density. Theirs is of course not the place to address what properties existed when there was space very high in potential energy density which endured an era 10 orders of magnitude in time in which no commensurate matter density existed. My question is not the hoary “Why is there something rather than nothing?” but “Why is space so small?” Steven, could you elaborate on some of these issues? It would help me no end.

And oh yes, since we are on matters of great magnificence and enormity, could you enlighten this non-Ozzie what the dickens a “Gish Gallop” is? =Thanks, Dana in S A

[xelasnave]

Dana try this
http://rationalwiki.org/wiki/Gish_Gallop
A debating approach where the number of questions and their content are to wide such that they can not be addressed.

[xelasnave]

Space is what is on the inside of the Universe which has no "outside".

[xelasnave]

As to science and religion.
Do not confuse seeking reality with the human need for structure and adherence to rules.
They can be seen as similar but one seeks to evolve and the other does not.
Will both be influenced by internal politics, well I suspect they would.

[sjastro]

Dana,

Regarding space there are two issues here.
Masses travelling through space and masses being carried by expanding space.

To travel through space work is performed in moving a mass from point A to point B which requires the expenditure of energy.
To accelerate a mass up to the speed of light requires an infinite amount of energy hence the speed of light is the upper limit for masses moving through space.

If the mass is being carried by space no work or energy is being expended as the mass is stationary relative to space's frame of reference.
From our frame of reference as the observer, galaxies with red shifts greater than z=1.4 have recession velocities exceeding the speed of light. From our frame of reference it is the space that is expanding, not the galaxies moving through space.

A canoeist makes a good analogy. A canoeist being carried by the rapids is expending no energy and is stationary relative to the water but moving relative to an observer on the bank.
If the canoeist paddles through the water he is expending energy and is moving relative to the water.

Expanding space isn't limited to the speed of light but the question arises where does the energy come from and how does it cause space to expand.
We can use the canoeist analogy again. The energy that drives the river is the conversion of gravitational potential energy into kinetic energy or in layman's terms rivers flow downhill.;)
Space is inextricably linked with a vacuum which is a field of the lowest energy state.
The theory behind inflation is that the Universe existed in a false vacuum (http://en.wikipedia.org/wiki/False_vacuum).
The false vacuum has a higher energy state than a true vacuum.
Like the river analogy, the Universe dropped from this higher level to the lower energy vacuum state releasing energy and causing space to expand at an accelerated rate.

Inflation only accounts for a tiny piece of the space expansion mechanism, we have absolutely no idea about the current acceleration of the space through dark energy. Attempting to explain dark energy as another false vacuum effect has failed miserably.

What we do know however is how the behaviour of space expansion has changed in the past and is related to the interaction of gravity and dark energy on the Universe.
In the past when the Universe was smaller gravity had a greater influence than dark energy. At some point around 6 billion years ago, the Universe had become sufficiently large for dark energy to become the major player.

I'm not quite sure about your "Why is space is so small?" question, you will need to elaborate on the background behind the question.
Also I will need to study your links in detail before commenting.





Alex has covered the topic nicely.:)

Regards

Steven

[Eratosthenes]

Well science does have its priests, worshipers, temples, ceremonies and religious texts.

It does have one redeeming and special quality that distinguishes it from all other fundamentalist religious cults.

It is prepared to alter the contents of its bible and restructures its sermons to the people.

Is it astonishing to see what proportion of scientists don't even realize they are priests attending a church and reading from scripture. They stand out as they are offended at being associated with dogma and bias.

[xelasnave]

Peter you could be burnt on the stake for your views.
Science is somewhat under seige thanks to the net...so you are either with us or against us

[Eratosthenes]

Xela,

I am well versed in the Scientific method. I know its limitations. I understand the fears and insecurities of scientists and researchers. I have been exposed to the ravages of political and corporate interference within the scientific domain.

I have never aligned myself with any tribal structures and its warm, safe and protective cushions. I am certainly not about to start now.

Are you aware that Science cannot explain how a bicycle works? (essentially why it is stable when a cyclists rides it).

[Slawomir]

I was not aware that bicycle cannot be explained - sounds like an interesting topic for a research, thank you.

Well, in the end, as far as I am aware, we still do not know what an atom looks like, what is light and why/how gravity works. Meanwhile mental problems are on the rise too; so much for our understanding of human psyche. To some degree, progress has been hindered by standardised education where curious young minds are programmed to memorise and accept information without any real and meaningful questioning. Anyway, by five cents worth of waffle.

[julianh72]

Ummmm... I'm a Structural Engineer, and I fully understand how a bicycle stands upright. Indeed, the principle is used in so many real-world applications that I can't even begin to comprehend were the claim comes from!

[julianh72]

How a bicycle works (spoiler alert!) :
http://www2.eng.cam.ac.uk/~hemh/gyrobike.htm

[Eratosthenes]

It was long thought that a bicycle gained its stability because of the gyroscopic effect, but helicopter characteristics discovered in the 1970s proved that theory to be an inaccurate explanation of bicycle stability. the "Castor Effect" was another theory that was popular but that was dismissed as well (by science). These theories, to be fair are incomplete theories in that they can explain bicycle stability but at different speeds. The latest theory I believe was tested at Delft University, with a specially designed bike which did not require the gyroscopic or Castor effect to work, and it still managed to move in a stable fashion. What the Delft bicycle revealed was that for it to be stable, it needed to be unstable, especially the steering. (the researchers dont know why this is the case)

I can sympathise with your comments on education. It is as if, the education system's main function is to bash out the natural curiosity and creativity of a young child or student. in order to push out automatons suited for the corporate world. Obedient and functional.

Its reflected in the type of fundamental research carried out in Universities and institutions. The research appears to be market driven, short term projects that can potentially generate profits, military research etc.

There doesnt seem to be any BIG idea challenges being tackled. Its reflected in some of the recent Nobel prize winners. A Nobel prize given for the invention of a blue LED (great as it is) just doesnt compare with those won by Dirac, Planck, Watson and Crieck, Shroedinger, Heisenberg, Pauling etc. Pioneers in fundamental research and profound ideas.

its sad to see medical research being driven by market forces and copyright etc. Money being poured into medical areas such as plastic surgery, rather than a disease which may effect a third world country (for example) - just no return for investors and bankers. Where are all the plans for space exploration?

Science still cant fully explain why humans require sleep - Oh Well back to the grind.............

[julianh72]

When you look at the time stamps for a lot of the posts on the IIS forums, it would appear that some people no longer have a need for sleep!
:rofl:

[xelasnave]

Hi Peter
I did not know there were problems understanding "how a bike works", if I had realised I would have worked it out for them years ago.:D
But apparently great minds are engaged so I will leave it to them.
As to why humans need sleep ..that's easy...because they get tired.
Money makes the world go round and commands many motivations so what we see is is apparent corruption of what should be. Nevertheless the system manages
to produce usable results.
NASA are working on a "warp drive" that exciting, although I am suspicious that they really have anything, that must count as exciting and if it can be made work may change everything.g
I certainly get the impression science is like a religion but I think that view comes from behaviours exhibited on science forums who frankly have very few real scientists
participating.
I think the most important area is to find a quantum gravity theory.
I of course have worked it out but I want the others to work it out.;)

[speach]

It's big very big. I feel that this is akin to 'counting how many angles can dance on the head of a pin'. The universe is expanding all the time, so it cannot have a finite dimension. If the expansion theory is held, conversely if it is expanding then it contracts back to a singularity, still we can't measure it's size. Because any measurement that we obtain will not be viable when we finish the measurement, the universe will have contracted further. In that case we could get a measurement but it would have to be at the Nano second the expansion changes to contraction. Not likely to happen. So let us suffice to say it's big very big.

[sjastro]

Expansion pertains to the visible Universe which we know is a finite size due the particle horizon being finite.
Whether the entire universe (observable + unobservable) is finite depends on its curvature. A positive curvature indicates a closed finite universe.

By measuring the angular sizes of anisotropic structures in the power spectrum of the CMB obtained by the Planck probe indicates the universe has a zero curvature and is therefore flat and probably infinite in size.

Steven

[speach]

You're wrong, the question is 'the size of the universe' no qualification, of observable or unobservable.

[Eratosthenes]

I believe it was Einstein (along with many other physicists and cosmologists)who described the Universe as "finite but unbounded"

(Boundary conditions and other assumptions are needed to describe the Universe in the mathematical realm.)

[sjastro]

For a Big Bang cosmology the question itself does require qualification in order to provide an answer.

Please explain to me how you are able to conclude "The Universe is expanding all the time it cannot have a finite dimension."

[Eratosthenes]

Has the universe always had a finite size?

Infinity conceptually, is nonsensical and indeed mathematicians refer to more than one "type" of infinity.

I am interested in whether the universe is bounded or unbounded. And whether there is only one universe.

An oscillating universe which is fluctuating in size would also produce observations which reveal that it is expanding (or contracting depending on what part of the cycle we are experiencing). We then extrapolate this expansion measurement back to time zero and assume there was a Big Bang.

We tend to like explosions.

Then we have the issue of the number of dimensions. It's difficult to conceptualise extra spatial dimensions past the 3 standard dimensions we are used to. (Plus time).

I have a gut feeling that not all is what it appears to be in the world of cosmology which is an ancient intellectual pursuit encompassing religions, philosophy, theology and science/mathematics.

String theory is a very good case in point of a theory which is still a mathematical philosophy, rather than a scientific concept. Scientific theories require observations, measurements, evidence to support (or refute) them.

:shrug:

[speach]

Simple, it's not expanding into something it's just expanding. You must get your head around the idea that to expand it must be expanding into an already created space. It's creating the space that it's expanding in to.

[sjastro]

Nice strawman argument.
Exactly where in this discussion did I suggest that the Universe was expanding into existing space?

Stop beating around the bush and answer my question.
How do you conclude a universe that is expanding all the time cannot have a finite dimension.

[xelasnave]

The term Big Bang is misleading.
It's implies explosion but the parallel is inappropriate and borders on useless.
We have a starting point for time and space which we can not describe and deal with the evolution of the Universe which inflated at at rate many times the rate of an explosion .
As Steven said inflation and expansion are separate matters. One is too grand to be called explosion and the other too humble to be called an explosion.
I think it is wise to remember we may not be describing reality but what we do describe is scientific theories which provide a very reasonable footing.
I personally find Inflation impossible to accept but I don't have an alternative theory.
My point is if one wishes to offer alternative cosmology one must offer a better theory.
As cosmology turns on general relativity one needs to offer something that takes us further than general relativity.
That won't be easy.

[xelasnave]

The term Big Bang is misleading.
It's implies explosion but the parallel is inappropriate and borders on useless.
We have a starting point for time and space which we can not describe and deal with the evolution of the Universe which inflated at at rate many times the rate of an explosion .
As Steven said inflation and expansion are separate matters. One is too grand to be called explosion and the other too humble to be called an explosion.
I think it is wise to remember we may not be describing reality but what we do describe is scientific theories which provide a very reasonable footing.
I personally find Inflation impossible to accept but I don't have an alternative theory.
My point is if one wishes to offer alternative cosmology one must offer a better theory.
As cosmology turns on general relativity one needs to offer something that takes us further than general relativity.
That won't be easy.

[Eratosthenes]

Indeed Xela,

it took several centuries before Classical Newtonian mechanics was augmented with Special Relativity (inertial/non accelerating frames of reference) and General Relativity (accelerating frames of reference).

And one needs to acknowledge that the Special Relativity and General Relativity theories are astonishingly accurate in explaining physical phenomena in the Universe (likewise Newtonian laws). However they all break down as some point (e.g singularities or phenomena that behave with an infinite curvature of space-time). In addition, the problem of unifying the Quantum world with gravity and large scale phenomena hasn't been resolved yet. This is god indication that both Quantum Mechanics and General Relativity may undergo revision or even a revolution. This of course isn't certain, because it may well turn out that resolving the microscopic domain with large scale effects could be beyond mathematics/science or inherently unresolvable. (especially with deterministic laws which are obviously contrary to the stochastic nature of Quantum mechanics).

Quantum theory is extremely accurate and reproducible, even though its description of the microscopic world is counter intuitive and insane (I will add that Quantum mechanics is not an exclusive theory of the microscopic world, but applies to the Universe as a whole and to large objects such as planets and stars and galaxies - the quantum effects are not noticeable at these scales and are swamped by other forces and more dominant effects).

The quest continues ladies and gentlemen - onward we go riding upon our grand silver horses like those that came before us.

:D

[speach]

The part of the universe that has expanded can and does have a dimension, but it's expanding so this dimension is continually changing. Lets take the analogy, that cosmologists are so fond of, a balloon. As the balloon expands it does so into nothing, but nothing is already part of the whole to allow it to be expanded into. So the conclusion must be that the emptiness it's expanding into is part of the universe.
:welcome:to the confusing world of mind experiments :)

[sjastro]

This is wrong on many counts.

Firstly it is incorrect to assert that only part of the Universe has expanded.
The entire Universe both observable and unobservable expands.
A distant galaxy that passes over the particle horizon from the observable to unobservable Universe doesn't stop receding.

Secondly you do not understand the meaning of dimension in the context of space. Dimension isn't some measured quantity but represents the degrees of freedom an object can move in space.
Since we live in what is essentially 3 dimensional Euclidean space, you are confined to 3 degrees of freedom in the "up-down", "front-back" and "sideways" directions.
Expansion changes the scale factor of space not its dimension.

Thirdly analogies are limited in their descriptions of Cosmology.
The flaw in your example is that you seem to assume this is a 3 dimensional Universe. The surface of the balloon is the Universe in this case and the observers are two dimensional whose degree of freedom is confined to the surface. The observers do not perceive movement in the third dimension namely the radial expansion of the balloon.
Hence it is meaningless to refer to the expansion of the balloon into this "nothingness".

Fourthly the idea that "nothing is already part of the whole to allow it to be expanded into" as a condition for the entire Universe being infinite is not only illogical but fails mathematically. As has already been alluded to there is nothing preventing the entire Universe being bounded and finite.
While cosmologists have measured the local curvature of the observable Universe to be zero and therefore flat, the global curvature of the entire Universe could very well be a torus!!
A torus shaped Universe is topologically flat, bounded and finite.

[Eratosthenes]

How is a finite torus model of the Universe, bounded?

Unboundedness implies there is "no end" (or no edge)

The surface of a sphere is a finite but unbounded 2D surface. It is unbounded because it does not have an 'edge'. Traveling along the surface goes on forever. You will pass over your starting point over and over again.

One model of the universe is a 'finite but unbounded' 4-dimensional space-time geometry

:question:

[sjastro]

Yes you are correct the surface of a torus is unbounded but a 3-torus is a closed manifold and therefore forms a bounded metric space ie. a finite Universe.

Steven