Definiton of a Universe

[Ibbo]

I am interested to hear what peoples opinion are on the definiton of our universe is. The Wikipedia definiton is:

 

"[in] materialist philosophical terms, the universe is the summation of all particles that exist and the space in which all events occur which has an equivalent idea amongst some theoretical scientists known as the total universe".

 

Another cosmological definition is:

 

"A finite or infinite space-time continuum in which all matter and energy exist"

 

But what about the possibility of other dimensions? They wont necessicarly be included into a "summation" of all particles that exist in our universes space. Or when we use the term 'universe' do we mean to include everything, even possible other dimentions and universes? Or just the space in which our planet floats along with all the planets, solar systems, galaxys and galatic clusters? If the universe is boundless, how can one word summarise EVERYTHING?

 

And, if possible, what if this "space-time continuum in which all matter and energy exist" includes more than matter or energy? Something else unseen? What about anti-matter and the bits which arn't made of anything but of which there are vast quantities in our known universe?

[Tormod]

If the universe is boundless, how can one word summarise EVERYTHING?

 

In fact, you just answered your own question. :tongue:

[infamous]

I am interested to hear what peoples opinion are on the definiton of our universe is.

Infinity times an infinity of infinities........

[Buffy]

Some thoughts on the questions you raise (not that any of these are correct or anything more than "musings" :phones: ):

• You hint at a tendency to believe that things that are outside our current ability to perceive--for example other dimensions or dark matter/energy--are "outside" the universe. I think that's a natural tendency, but it brings up the question: in defining something as efemeral as "the universe" why is it reasonable to exclude any concept simply because it is not *yet* understood?
  
• The conventional wisdom is that the universe is "finite and unbounded"--which is a hard concept to grok--which opens up lots of possibilities. Even given that its "unbounded" (no edge that we can see), there's still room for an "outside", and there's lots of possibilities from Andre Linde's Self-Reproducing Universes (aka "Multiverses") to the Many Worlds Hypothesis (which has been extrapolated to compute the space that would be required to represent copies of our own universe with every conceivable permutation of states of all elements: a big number but computable!). Are these truly "outside" or do they constitute what we *ought* to include in the "universe"?
  
• Apply Goedel's Incompleteness Theorem: is it possible to define the universe in terms of a single instance of it (the only one we are able to see)? Is it *really* definable in its own terms?

 

This question is as philosophical as it is scientific, but its a good one and it justifies much ponderment...

 

Existentially,

Buffy

[Tormod]

It is indeed the basis for much of modern cosmology.

 

"I could be bounded in a nutshell and count myself king of infinite space." - Hamlet

[Ibbo]

Thank you all for your replies.

 

Buffy, in reply to:

 

"You hint at a tendency to believe that things that are outside our current ability to perceive--for example other dimensions or dark matter/energy--are "outside" the universe. I think that's a natural tendency, but it brings up the question: in defining something as efemeral as "the universe" why is it reasonable to exclude any concept simply because it is not *yet* understood?"

 

In your opinion then, does your definiton of 'the universe' include everything, from everywhere (every dimension) time and place? For example, if our universe was finite (or had finite volume yet boundless) then would your personal explanation of the universe include that all the other dimensions and times and spaces (and everything else we cannot yet perceive) fall under the same definition?

 

Are we severly restricting ourselves by using the term universe to describe JUST what we, as simple human beings can see? And if the universe is infinite, and has an invinite amount of dimensions, then can we really use one word to describe everything everwhere ever? Can one word really mean so much?

[Buffy]

"When *I* use a word," said Humpty Dumpty in a scornful tone, "it means just what I choose it to mean, neither more nor less."

Words need only to be defined and relationships between them clarified: I actually come down on the side of saying that the definition of the word "Universe" is *our* instance of it, but that there are a multitude of universes out there, and there are different theories that are unprovable as of yet that could indicate that the *number* of universes out there might either be finite *or* infinite.

 

So to answer your question about my opinion: I dunno. :shrug:

 

The truth as always, will be far stranger, :phones:

Buffy

[InfiniteNow]

The semantics issue has already been raised, and for good reason. My belief is that a big part of the problem is the root "Uni" as it implies oneness. I think that what we used to call the "universe" has since grown into myriad possibilities through the years, and multiverse may be more appropriate.

 

However, if one were to expand their definition of "universe" to incorporate everything, I see it as the ultimate set. Everything else being a subset.

 

Personal opinion, but I think that the "universe" is the only TRUE representation of infinity.

[Jay-qu]

I could tell you what infinity is - it would just take me forever :eek_big:

 

I think the universe is everything - but it may be only considered as everything 'around us', all I mean is that if the universe was everything then why doesnt the multiverse theory still use the word universe for what it all is..

[CraigD]

I think the idea of causal connectedness is important in defining the term “universe”.

 

2 attributes – particles in a model of the physical universe, points in a point set, or whatever formal system one chooses – can be considered in the same universe if and only if they are able, directly or thought other attributes, to effect one another. Since every formal system (or informal idea) we can articulate is represented by something in the physical universe – magnetic polarization or charge in a computer memory, ink atoms on paper, or the state of neurons in our brains – all formal systems, even ones that are not causally connected by their own axioms, can be considered included in the physical universe. So, the physical universe in which we find ourselves is The Universe.

 

Suppose there exist other universes, along the lines of those proposed by the many-worlds interpretation of quantum mechanics. If some physical phenomena exists that allows interaction, however slight or useful, between these “worlds” – whether imagined, unimagined, or unimaginable to science – then they are all part of “The Universe”. If not, these other universe are not, and for all practical purposes do not exist. This is not to say that in some larger sense, wherein evidence is not required for the knowing of a thing, these other universes don’t exist, nor that our “Universe” is in some absolute way more real than these others, just that we can never know, or in any physical way benefit or suffer from their “acausal existence”.

 

Since we can’t logically exclude the possibility of such world-joining phenomena, the actual “size and topology” of The Universe remains an open (and mind-boggling) question.

[HydrogenBond]

I believe that the definition of the universe is what is real and tangible. The idea of multidimensional universes is what religions has taught for thousands of years. The new rendition was consciously or unconsciously borrowed from religion. For example, heaven was never said to be in this material universe but a parallel nonmaterial universe. The original religious idea is considered silly, yet the borrowed version is considered legitimate? Where does science make its distinction?

[CraigD]

I believe that the definition of the universe is what is real and tangible.

I share this belief, which I usually term materialism.

The idea of multidimensional universes is what religions has taught for thousands of years.

Although I don’t know the precise history of cultural ideas of heaven, but it’s worth noting that, despite the prevalence of the idea of heaven as a “parallel universe” that HydrogenBond describes, the idea is not a longstanding tradition in any but a few, fairly obscure organized religions (much like the popular present-day belief that one’s pets also go to heaven).

 

Early Christians, for example, fairly clearly believed in an afterlife scenario in which their physical remains would be reanimated to live again on Earth, resulting in what one might call an obsession with the preservation of corpses, and, eventually, bones. This practice – which included a grim competition in which Christians struggled to hide and preserve their coreligionists’ remains, while their opponents sought to find and destroy them – produced hundreds of miles of catacombs in practically every western population center where such excavation was possible. “Heaven” was interpreted by most Jews, Christians, and Muslims, to be a physical place, high above the ground, the dwelling place of God, Angels, and, according to some, certain prophets and saints. The idea that entities other than God could exist as incorporeal spirits was heretical.

 

Although it’s difficult to determine precisely when this very physical idea of heaven began to give way to a more metaphysical one, there’s clear evidence that the idea was well established in at least a minority of religionists by the late 18th century. There appears to be a connection between the emergence of “spiritualistic” religions, and popular awareness that the stars are suns, potentially orbited by planets containing creatures similar to human beings.

 

I suspect that current “New Age” spiritualism is influenced in a similar way by popular awareness of hypotheses suggesting the existence of parallel universes. Though scientific support for these hypotheses is scant and highly speculative, explorations of the idea in the popular media (eg: Star Trek) has made them well known.

[sanctus]

The original religious idea is considered silly, yet the borrowed version is considered legitimate? Where does science make its distinction?

 

I think the distinction lies in the fact that science still says it's a theory, that means a thing that could be right (logical thinking behind), but cause of lack of proof so far is still only a theory. Religion says it is the truth, without having proofs.

[Ibbo]

If the theory of multiable universe's (seperate dimensions) can be proved, but we discover there is no physical link between ours and theirs, then are they the same thing? Does the word 'Multiverse' really convey enough meaning to be able to define the idea of a possible infinite amount of other universes that are not touching ours, which (again in theory) are infinite theirselves?

 

Its like- If you had a room full of different balls: basket balls, footballs, rugby balls, tennis balls etc... then can you define your room as being just full of balls? Even though the balls are different sizes, shapes and colours? Ok, its a pretty naff analogy, but the point im trying to raise is that, in my opionion (and general ramblings) the word universe is too broad, especially for scientific purposes. I would also like to thank everyone else for their own definitons and posts on this topic!

[Harry Costas]

The Universe

 

The word Universe stands for "ALL" and in so meaning that, we cannot expand it, compact it, place more than one of itslef.

But! It is home for all the parts within. These parts can be expanded, compacted, recycled, collide with each other and behave as units with others and themsleves.

 

Man with his limited knowledge will add different theories from the Big Bang to the steady state and so on. Can one be correct to describe the universe, no way. Both are wrong.

The theories apply to the parts within the universe and in many cases all theories add to describe the behaviour of these parts.

[ingannilo]

hmm.

 

I was under the impression that we've sortof re-defined the term universe in the scientific world. Some time ago, from a credible source I was told that hubble had photographed/was able to see the edge of our 'universe', that it was the name we had for this mass of galaxies. I've read figures on it's rate of expansion, etc. I imagine we've got some more tangible concept of what a universe is than what's being discussed here...

 

If I had any more information I'd contribute it, but I'd kill to see a definitive answer!

 

EDIT-- a bit of google searching gave me this, it's got some good information: http://skyserver.sdss.org/astro/en/proj/basic/universe/conclusion.asp

[CraigD]

I was under the impression that we've sortof re-defined the term universe in the scientific world. Some time ago, from a credible source I was told that hubble had photographed/was able to see the edge of our 'universe', that it was the name we had for this mass of galaxies.

I’m under the same impression.

 

To keep this use of the term distinct from the several other mathematical, scientific, philosophical, and literary ones, people appear to qualify it with the phrase “visible universe”. Most appear to mean everything within about a 14,000,000,000 light-year radius (centered on what? I don’t know), whether we can see it or not – that is, including any “dark matter/energy” that might exist.

 

I found this sensible-seeming webpage, which estimate the mass of the visible universe at 3*10^55 grams.

 

What’s in the visible universe is rather – no pun intended – up in the air at present with the wide scientific community, I think. Consider the following naively simplified hypothetical scenario

• The collection of gravitationally interacting object in which our planet, solar system, and galaxy is a part is about 14,000,000,000 years old, and began with the big bang.
  
• Another similar collection of gravitationally interacting objects began around the same time, 14,000,000,000 or fewer LYs away
  
• Just now, light from the earliest period of that other collection is arriving here. Distinguishing it from light from our own collection is difficult – however, it would present a disuniformity in the seemingly homogenous distribution of light sources in the sky – including the cosmic background radiation. It would also present dramatic violations of Hubble’s law – very old, distant objects with large blueshifts instead of redshifts.
  
• With the passage of time, more and more such “local big bang” artifacts appear in the sky.

Since we don’t (it appears) see this now, these other LBBAs either don’t exists, or are still too far away.

 

If something like this scenario is accurate, the visible universe, though still finite, will constantly increase in mass/energy, independently of the conditions near the location/instant of our own LBB.

 

I recall that there are at least a few heretics here at hypography who are sympathetic to enthusiastic about the idea of LBBs.