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 (Peter)]

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 (Julian)]

"A human is halfway in size between an atom and the known universe"
http://ask.metafilter.com/57214/A-Pr...d-the-universe

[ZeroID (Brent)]

Originally Posted by julianh72

"A human is halfway in size between an atom and the known universe"
http://ask.metafilter.com/57214/A-Pr...d-the-universe

I always suspected we were a bit average ...

[Weltevreden SA (Dana)]

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 (Julian)]

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 (Peter)]

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]

Originally Posted by 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?

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 (Peter)]

....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]

Originally Posted by 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?

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 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 (Peter)]

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]

Originally Posted by 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.

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 (Peter)]

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 (Peter)]

Originally Posted by Alasdair

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.

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

10^23 times bigger?

[Slawomir (Suavi)]

Originally Posted by Eratosthenes

Science is a very effective and efficient religion.

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]

Originally Posted by 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.

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.

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.

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 (Dana)]

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) and Brian Lacki’s “CMD” of the energy sky (Fig 4), with a recent group of papers devoted to the properties of cosmic voids and filaments, Rieder, Alpaslan, Tempel, Libeskind. 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.