Size of the Universe 43 replies

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Nemmerle Forum Moderator

Voice of joy and sunshine

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#21 11 years ago

I like Red Dwarf's idea: Explode stars in sequence to spell out advertising in the sky :evilgrin:




Flash525

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#22 11 years ago

To be honest / fair, the size of the universe at its current stage is one thing, as is the shape of the universe. What fascinates me (even though I don't like to think too much into it) is the expansion of the universe. We have been told that the universe is growing. The question then, that is asked, is what is the universe growing into. The only two obvious answers are 'nothing' and 'something'. If the universe is growing into something, then that would be something that is already there (what this is, nobody knows), if the universe is growing into nothing, then there isn't actually anything outside of the universe, it is just growing though. Some people may argue that the nothing, and the something are the same, it isn't, but because we cannot grasp the concept of 'nothingness', we cannot even begin to understand it. One question that puzzles me though... To my knowledge, it is the universe, and not the galaxy(s) that are expanding. Based on that, why do people go on about the stars getting further and further away. The stars we see in the night sky are those in our galaxy, and our galaxy isn't getting growing like the universe, sure things may move around, but not grow as such.




Serio Advanced Member

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#23 11 years ago

I think it's more along the lines that the universe 'creates' something when it expands. Though that brings to mind the question; What is there in the area it creates something? Whatever it is was there before the universe, and likely will also be there after it.




Showd0wN

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#24 11 years ago

Penguin_UnitThen you are accepting an untruth. Not everything is perfectly the same throughout.[/quote] The universe being homogeneous and isotropic is the cosmological principle and is the cornerstone of modern cosmology. It does suggest that this: [/quote]For example, stars burn at different temperatures from each other[/quote] is impossible. It simply refers to the large scales. Local groups, galaxy clusters, and super galaxy clusters. And even bigger things (cf. large scale structure). It is on this scale of beyond megaparsecs that the universe is isotropic and homogeneous

The entire universe would be a single temperature if it were uniform.

well in once sense it is - cf. the Cosmic Microwave background with a temperature of 2.73k is a relic when the universe was actually in thermal equilibrium. Again tehre are pockets of change on the scale of stars and matter distribution locally, but on large scales teh universe is close to being homogeneous

To my knowledge we can't "see" the edge of the universe

we can see the edge of "our" universe. i.e. the horizon - that which is in causal contact with us. This is the effective size of teh universe for us, it is defined effectively by teh distance light could have travelled

[quote=Aerilon] We have been told that the universe is growing. The question then, that is asked, is what is the universe growing into. The only two obvious answers are 'nothing' and 'something'. If the universe is growing into something, then that would be something that is already there (what this is, nobody knows), if the universe is growing into nothing, then there isn't actually anything outside of the universe, it is just growing though.

i don't mean this in a patronising sense-but this is quite a common misconception about how the universe expands. Expansion does not mean it is "growing", growing would require teh universe to be embedded in some bigger object. If the universe is infact all there is, tehn expansion is just that the space itself is growing, sort of a strange concept but that is the basic gist of it.




NiteStryker

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#25 11 years ago

What "shape" is the universe?

What is the rate of expansion?

Wtf how does the universe expand? Whats on the other side of the universe?




Showd0wN

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#26 11 years ago

What "shape" is the universe? The universe is effectively flat by agreement of most current observations.

What is the rate of expansion? the rate of expansion is given by the scale factor from the Einstein equations, but more simply is given by hubble's law: v = Hod where V is the recession speed of plannets, Ho is a constant, and d is the distance that the object is currently from us. Wtf how does the universe expand? Whats on the other side of the universe?7 the same stuff that's on this side of teh universe, or at least the same type of stuff. The universe is expanding because of how it was created.




NiteStryker

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#27 11 years ago

clan.necrosect;4852547What "shape" is the universe? The universe is effectively flat by agreement of most current observations. [/QUOTE]

So to travel from one side to the other, going vertically (if you could determine that) would get you from one end to the other quicker than horizontally?

clan.necrosect;4852547 What is the rate of expansion? the rate of expansion is given by the scale factor from the Einstein equations, but more simply is given by hubble's law: v = Hod where V is the recession speed of plannets, Ho is a constant, and d is the distance that the object is currently from us.
So what does that amount to? [QUOTE=clan.necrosect;4852547] Wtf how does the universe expand? Whats on the other side of the universe?7 the same stuff that's on this side of teh universe, or at least the same type of stuff. The universe is expanding because of how it was created.

oOo so the universe is expanding like grass expands in a field (there is space for everything, stuff is just filling it), versus a definate end to our universe like a wierd ass portal or something?




Showd0wN

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#28 11 years ago
oOo so the universe is expanding like grass expands in a field (there is space for everything, stuff is just filling it), versus a definate end to our universe like a wierd ass portal or something?

in short no. again, these sorts of ideas assume that our universe is somehow embedded in a larger or high dimensional object. I am not say that this isn't the case, just simply that to explain expansion it is not required.

So to travel from one side to the other, going vertically (if you could determine that) would get you from one end to the other quicker than horizontally?

I can almost definitely answer this question yes, or no. both with equal certainty, just in that our universes doesn't really have a natural sense of "vertical" and as it is considered flat there will be one dimension that is more expansive than the most. You have to remembr that questions about the "edge" of the universe, or travel on scales simply not possible (i.e. exceeding the horizon) really have no actual actual - physics does not stretch this far currently; or at least explanation by someone more adept than I.

I have obviously not addressed your question on the rate of expansion as it is something that requires quite detailed discussion. The formula I presented was something that was trivially confirmed by observation that gives a rough estimate of the expansion rate of the universe. The actual detail in teh large scale structure and evolution ofthe universe is something taht really does need proper mathematical treament.




Master Ridley

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#29 11 years ago

'LIGHTNING [NL;4846353']Here you make a mistake. We accept the universe as being homogenous and isotropic. This means there is no area where there are no galaxies. All matter is evenly distributed among the universe.[/quote]

I guess you don't know about 'Voids'. Voids are places between Super Galaxy Clusters where this is little or no matter let alone Galaxies though Galaxies do exist in voids, just an extremely small amount.

Believe it or not but I have a map of the Entire Known Universe: Nearsc.gif

'LIGHTNING [NL;4846353']If you look even further back than that you can see the CMBR (Cosmic Microwave Background Radation). This is the radation from the period following the big bang in which all matter was highly compressed and very hot.[/quote]

Wrong! What you state is a misconception. In reality, the Cosmic Microwave Background Radiation appeared during the Recombination Epoch of the Universe which started from 240,000 years after the Big Bang and ending 310,000 years after the Big Bang. The CMB was the effect of the formation of Hydrogen and Helium atoms through cold fusion

'LIGHTNING [NL;4846353']Does the universe have an edge? I don't think it does.[/quote]

Technically where no matter and energy passes is the edge of the Universe.

DnC;4846480I believe in the theory is spherical like Earth. If you were to set off in a straight line in the Universe, you would end where you once began. PONDER THAT!

I can't even fathom how space-time would be spherical. There is also no way of knowing if the Universe is a spherical plain Universe.

[quote=Penguin_Unit;4846578]Then you are accepting an untruth. Not everything is perfectly the same throughout.

For example, stars burn at different temperatures from each other. The entire universe would be a single temperature if it were uniform.

It doesn't matter that the matter within the Universe have different temperatures, the Universe itself IS uniform.

[quote=Penguin_Unit;4846578]Again, if this were true, everything would be of an identical temperature. Baseless.

Not Really…The Science Consensus says otherwise.

[quote=clan.necrosect;4852547]What "shape" is the universe? The universe is effectively flat by agreement of most current observations.

The Universe isn't physically flat. The question whether the Universe is flat or not has to do with the plain of space-time, not physically.

Proof of a Flat Universe, an Open Universe, Closed Universe, Sperical Universe, and Hyperbolic Universe do not exist.




Showd0wN

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#30 11 years ago
The Universe isn't physically flat. The question whether the Universe is flat or not has to do with the plain of space-time, not physically. Proof of a Flat Universe, an Open Universe, Closed Universe, Sperical Universe, and Hyperbolic Universe do not exist.

Here I have to disagree. Anyone who talks about the "shape" of space is talking about local manifold geometry (or at least should be). This defines the "geometry of our universe". Of course space isn't physically flat. That would be stupid.

Also i never said there was proof, I said the majority of current observations (BOOMERANG, MAXIMA-I, WMAP) put \Omega_total=1 to a good degree of accuracy. Which is the situation for a flat universe or effectively flat.

Also with the scheduled launch of the Planch surveyor satellite later this month the precision to which we know the value of the total density parameter will be much improved.

Also just because making flat out statements like that need backing up: Constraints on cosmological parameters,Amedeo Balbi

Large-scale structure and matter

Detectability of cosmic topology in almost flat universes, G.I. Gomero

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edit: this is what i get for not reading stuff properly

The CMB was the effect of the formation of Hydrogen and Helium atoms through cold fusion

My gut instinct when I read this was to jump all over this statement. I have to just say no to it though. Cold fusion isn't really an accepted occurance. Also it's not what happens, recombination is an electron capture process, not a nuclear process.

I guess you don't know about 'Voids'

It is generally accepted within the scientific community that the cosmological principal is not actually accurate. however for the purposes of most discussions it is a valid enough approximation.

--------------------------------- edit2:

Originally Posted by LIGHTNING [NL] viewpost.gif If you look even further back than that you can see the CMBR (Cosmic Microwave Background Radation). This is the radation from the period following the big bang in which all matter was highly compressed and very hot. Wrong!

Well actually no it's not wrong, it's just not entirely accurate. The CMB is from a period after the big bang where the matter content was more compressed than it is now, and it was hotter.