Centre of the universe

[Viper]

In the centre of the universe I belive there is a giant black hole that all galaxies orbit

[KLscilevothma]

the universe doesn't have a centre

[Viper]

But then if you look at all of the galaxies they are swirled around a centre or central area or an object(s) of intebse gravity

[chroot]

Originally posted by Viper
But then if you look at all of the galaxies they are swirled around a centre or central area or an object(s) of intebse gravity
Wrong.

- Warren

[KLscilevothma]

I don't think galaxies are swirled around a centre, rather they are moving away from us. That's why we say the universe is expanding.

[Viper]

Ok but what are they stretching from. If the universe becomes too stretshed will there be like an elastic affect?

[chroot]

Originally posted by Viper
Ok but what are they stretching from. If the universe becomes too stretshed will there be like an elastic affect?
What are they "stretching from?" Can you please try to be a little more clear?

- Warren

[KLscilevothma]

the fate of the universe depends on the amount of matter inside it.

There are 3 types of universe, closed universe, open universe and critical universe.

A close universe ends up with a big crunch(the universe collpases) while an open universe ends up with a big freeze (the universe stop expanding)

Our universe is a critical universe, which has a flat curvature. So it won't end up with a Big Crunch or a Big Freeze.

(I'm not very sure about the recent developments of astronomy, scientists still think our universe is a flat one, right? )

[Loren Booda]

The universe may itself be considered a black hole, which from our perspective has potential centers everywhere within. Its centers are isotropic from every homogeneous point to their event horizons where the escape velocity exceeds the velocity of light relative to the observer.

[Viper]

Thats more like it

[Phobos]

The universe has no center or edge in 3D space. The universe is boundless. The overall expansion of the universe is essentially omni-directional (occurs in all directions from every point). Things only appear to be moving away from us because we are only viewing from one reference point. If you were to observe from another distant galaxy, things (including the Milky Way) would appear to be moving away from that point too.

Not all galaxies have a massive center. There are many elliptical/irregular shaped galaxies that are without massive/easily-to-define centers like our own. Photos one sees in the media are usually spiral galaxies because they are so picturesque.

Stretched space is not expected to snap back. It will continue to expand forever...probably at an accelerating pace.

Yes, the universe is still considered "flat" as far as I know. That means it will expand forever. An open universe will expand forever too. The "big freeze" mentioned does not refer to stopped expansion, but rather "heat death" in which all matter falls apart and all energy is reduced to ground state....the universe is left as a cold, thin soup of fundamental particles with no useful energy.

Although Loren's post makes for an interesting discussion, I think it's confusing Viper's topic. By definition, a black hole is an object residing within spacetime, not the whole of spacetime itself. But the similiarities are worth a separate topic of discussion.

[M. Gaspar]

Has anyone logged the "death" or "disappearance" of a black hole.

What could STOP a black hole from "eating" its "neighborhood"?

I don't buy Hawkings thought that because some energy radiates OUT that a black hole will eventually "evaporate". More stuff goes in; it becomes more massive; its gravity increases; it eats more stuff.

If black holes continue forming -- and consuming matter/energy -- then doesn't it follow that EVENTUALLY black holes will suck in everything in between, until they all "unite" into a singularity (AGAIN!)?

There's your "Big Crunch"...and a brief look at the "life cycle" of the Universe...an Eternal Entity of Energy that reincarnates from Big Bang to Big Bang.

[Jack]

Originally posted by Viper
But then if you look at all of the galaxies they are swirled around a centre or central area or an object(s) of intebse gravity

The unviverse has no centre because it is not expanding from a single point like an explosion but rather every bit of space increases in size and then that it turn increases in size. The galaxies are not centred around a 'central area' (as far as we know).

[Mr. Robin Parsons]

Originally posted by M. Gaspar

I don't buy Hawkings thought that because some energy radiates OUT that a black hole will eventually "evaporate". More stuff goes in; it becomes more massive; its gravity increases; it eats more stuff.

As I recollect Hawkings work, the radiation is not from the center of the Black Hole, but from the interaction of the 'event horizon' with the 'fabric' of space/time.

The Black Hole itself radiates nothing! (loses no mass)

A Black Hole does NOT "eat it's neighbourhood" as it is a gravitational well that only increases in size relative to the mass within it, so it is NOT like a vacuum cleaner sucking up everything around it, it simply empties the space around it to a decreed limitation that is imposed by the Modus Operandi of Gravity.

After that, it is up to the mass to get close enough for the gravity to take hold and effect it, suck it in.

[M. Gaspar]

And matter will cooperate over time.

[Brad_Ad23]

yes it will over time. But, eventually you run out of matter, and the black hole will evaporate. This is why it is generally said that stellar sized black hole has a lifetime of about a googol years (the bigger the hole, the much longer it takes).

[M. Gaspar]

Perhaps you "run out of matter" because it all gets compressed into a singularity -- down the road! -- from whence springs the next "Big Bang".

[Brad_Ad23]

I should point out to you that all the black holes that form will NOT colesce into one giant one. The universe will be expanding so fast that far in the future, that it'd be lucky if a black hole was within the present diameter of the universe from another black hole. And as was pointed out, black holes merely empty the space surrounding them.

That means if the sun suddenly was replaced by a black hole of equal mass, all objects would continue to orbit the black hole as they presently do...exception being Mecruy due to its proximity, but even then it is doubtful it would be pulled in.

[Mr. Robin Parsons]

Originally posted by Brad_Ad23

And as was pointed out, black holes merely empty the space surrounding them.

That is quite true for the Short ranging of gravities ability, but , Gravity is presently thought of as having Infinite range, till that is proven differently, we must accept, that given enough time Gravity will win out over everything else, and all will be drawn back together into a, well, whatever is the center of a Black Hole, presently thought of as a singularity.

It's the Newtonian thing, M + M / D2

[Brad_Ad23]

Well all things equal that is correct. However, there is that rather odd acceleration to the expansion of the universe that pretty much seals the universe's fate as the heat death.

And yes gravity has infinite range...but does that mean the gravity has the same strength? Nope. If matter is traveling sufficiently fast enough (as it would be) and if space is expanding fast enough (as it would be) then the matter will just keep on going until eventually it runs into whatever black hole it may encounter, if any.

[M. Gaspar]

Brad...

Per your posting... then I think the Universe is going to "get lucky" because, even though it may be expanding at an accelerating rate, this does not preclude an eventual deceleration...especially if there is a relentless and irresistable attractive force pulling It in.

Perhaps I'm obtuse and hopelessly uninformed, but why do physicists -- at the moment --"believe" that a black hole -- the result, itself of an imploded matter/energy -- is not "pulling things in" but instead, everything just gets "stuck" at the "event horizon".

Because of some mathematical construct that will DE-struct in the future?

And why does Hawkings think that black holes will "evaporate"?

I might be left-brain-dead, but my right brain tells me something is amiss with current "theories".

Has anyone run computer models on the pull of current -- and future additional -- black holes on the rest of the Universe over time?

And why is this "important" to me? Because I like my own belief system which has the Universe as a living, conscious Entity that expands and contracts from one incarnation to the next.

I might be wrong, but I'm having a lot of fun with my speculations.

AND, I might be right.

[Brad_Ad23]

Ah misconceptions.

Gravity is a very weak force. The strength it has occurs only near the event horizon. Think of a very severe local curvature of spacetime. Far away it is like any other body of the same mass, but very near it becomes strong. So gravity quite simply is losing the battle here.

The matter does not get stuck at the event horizon. It only seems that way to an outside observer, but it does very much pass through the event horizon.

[Mr. Robin Parsons]

Gravity at the 'event' horizon is only called that because at that particular event horizon NOTHING escapes it, including light.

For most gravitational bodies there is no real, or apparent, 'event horizon' as the vast majority cannot preclude the escaping of light.

As for this idea of continuous expansion "forever", given that the gravitational force will be forever 'braking' that expansionary force, doing the math would tell you that, 'eventually', gravity will be able to stop any object travelling away from the gravitational source, and 'eventually', reverse it's direction, till it begins to return towards the gravitational generator.

It may appear as weak, but it is inccessant!
(persistance wins!)

[Viper]

How big is the event horizon?

[Mr. Robin Parsons]

The event horizon is relatively sized to what is seen as the amount of mass that the Black Hole is 'theorized' to contain.

There is a sort of difficulty is measuring large stellar bodies as we do not have an adequate scale/balance for the task. Hence we end up with things like, we know the weight of the earth because we know how strong it's gravitational field is, and we know how strong the eath's gravitational field is, because we know how much it weighs.

Self supporting, ergo sorta 'unsupported' but accepted in general principal, and theory, cause we have no other means to test it

[Brad_Ad23]

Have you ever heard of escape velocity?

If you have a velocity greater than an escape velocity gravity will never return you to the body you came from. Hence why you need escape velocity to go anywhere outside earth orbit. The expansion drives things faster than the escape velocity of anything.

[M. Gaspar]

Brad...

My view is that you -- and many others -- are thinking SMALL SCALE and SHORT TERM.

Please read above post of Mr. Robert Parsons. He used the words "incessant" and "persistence" while I used the words "relentless" and "irresistable" to describe an ATTRACTIVE process that is in for the LONG HAUL!


Thanks, R.P., I needed that.

[Brad_Ad23]

No, you didn't. Escape velocity applies to any gravitational system on any scale. Once the expansion of spacetime reaches a rate such that it is greater than what the gravitational force is, it will only get faster, further diminishing the gravitational force, until it is all but zero as everything will be isolated within its own event horizon (many trillions of years down the road). It just goes to fast for gravity to overcome. The same way if you launch a rock up out of earth orbit at about 11.6 km/s it will never come back to earth.

[M. Gaspar]

And I say there is ENOUGH gravity -- via the ultimate coallescing of black holes -- to do the trick.


And on another subject (should I start a thread?), would someone tell me what comes to mind when I say "OFF/ON" as it related to the workings of computers...and also to electromagnetism.

Keep it simple. I'm stupid.

[Brad_Ad23]

And the entire scientific community says otherwise. Black holes are severe local distortions of spacetime. If we have a black hole of Mass 5 then from far away it has the same effects as any other objec tof mass 5. However very near it, it is easy to see the black hole is worse. They are for lack of a better word, the whirlpools of spacetime.

[M. Gaspar]

Thanks, Brad, for making my point.

I don't care what the "entire scientific community" is currently espousing. At least my speculations are being rejected by the best minds in the business!

[Brad_Ad23]

The difference is, they have the math to back them up..and it is rather elementary math at that. You have a flawed understanding of a black hole to go on. And...you ideas would most likely be rejected by any mind in the business heh.

[M. Gaspar]

So, I'll get back to you on this after a bit of research which might yeild me a few "business PARTNERS"...if you know what I mean.


Purely curious: Have there EVER been mathematical "PROOFS" that have eventually been "proven" to be false?

What if something vital is omitted from an equation?

I'm not baiting you. I really want to know.

[Brad_Ad23]

Well anyone can come up with a mathematical 'proof' that is false.

ex.

2+2= 5, therefore 1+3 = 5, therefore 1+2 = 4. Prooved.

However in the real sense I can't recall any proofs that have been shown to be false merely because proofs require such stringent circumstances. Theories and theorems sure.

However in this case, the physics is very solid and elementary. The expansion of the universe is such that any two points in space that are not gravitationally bound (there's the key...galaxies and clusters for now will remain together), will have the space between them increase such that the velocity of the seperation between them is far greater than the escape velocity of either body. Once you are above escape velocity, you can escape that massive body.

[M. Gaspar]

Processing...

[Brad_Ad23]

No problem. I suggest some helpful things to search for are potential energy, escape velocity, and dark energy.

[russ_watters]

Originally posted by M. Gaspar
Purely curious: Have there EVER been mathematical "PROOFS" that have eventually been "proven" to be false?

What if something vital is omitted from an equation? If you're wondering if we'll find the math behind black holes to be flawed, I find it unlikely that there is much wrong with the equations. Years after the equations were worked out (which was before any were found), black holes have been found and the equations have been verified by observation to be accurate.

[Sting]

One thing that is important concerning the fact that there is no "center" of the Universe since something like the Big Bang happened to space, not in space.

[Brad_Ad23]

Very true. It is not an explosion like many people picture in space. But rather it is an explosion of space...in other words every point is the center.

[Mr. Robin Parsons]

Lets see, escape velocity is the speed required to overcome the gravitational force, as to escape it.

The event horizon of a Black Hole is the point at which the escape velocity goes SUB-LIGHTSPEED, or SUB C, drops below C for the very first time, which is not to say that there is no longer any gravity there, just that the escape velocity has decreased to a point at which light could/can escape the gravitational atraction currently working there.

On the inside of the event horizon of a black Hole the escape velocity would be greater then C.

Gravitational atractiveness drops off relative to distance, the divided by D2, hence it has the abitlity to delineate space as per it's relative strength, the reason why there is an event horizon in the first place.

But the gravitational attractions do not stop at any point outside of the gravitational body, at no known distance does gravity stop working, hence all matter will,eventually, be gravitationaly recondenced.

[M. Gaspar]

PLEASE TELL ME YOUR ARE A SCIENTIST OR MATHEMATICIAN...

not a crackpot like myself.

I will FRAME your last posting if you are.

[Mr. Robin Parsons]

Sorry, neither of those professionally. (nothing right now 'Professionally')

It has been a bane in my recent life that I have NOT been able to obtain the accreditation that I am due, so, till that happens, I am just Mr. Robin Parsons......47 years old, and lots of that time spent thinking, in study, learning, on, and on, and on, but Thanks for the compliment, just the same.

[Brad_Ad23]

Unfortunatly there is one thing that seems to be neglected here. As I suggested looking up, dark energy. It is another force of sorts that is driving the expansion of the universe. So it is not just material moving away itself, it is the actual fabric of spacetime expanding between any two points.

[M. Gaspar]

Please factor in the "dark energy" per Brad and see if the Universe still collapses. Might there be a countervaling force to dark energy that has not, as yet, been theorized or "discovered".

Indeed, is dark energy the results of a mathetical theory based on observations...or is is something measurable (and I don't mean by its EFFECT).

Remember, I'm currently ill-informed, so please be kind (Brad).

[Mr. Robin Parsons]

And another one being neglected is "Dark Matter" which is needed to 'square up' the observed motion of the galaxies, the idea that the entire galactic disk turns as if it were 'one thing', unlike the water going down a drain analogy which swirls faster at the center and slower at the outer edge.

Dark energy, well, proven to be?, or speculated? as to fill in certain 'missing elements' of the current theories of the universe?

Brad_Ad23, your turn!

[Mr. Robin Parsons]

Brad_Ad23, an assist, (perhaps) look *HERE* (http://www.physicsforums.com/showthread.php?threadid=704), perhaps you will understand it better.

[M. Gaspar]

You're becoming VERY VALUABLE to me. Thanks for the lead.

(How'd you DO that?!) (Also, how to capture quotes?)

[M. Gaspar]

Your name is ROBIN. I got it now.

[Mr. Robin Parsons]

It's done like this <url=" insert adress here"> Type words here </url> and the capturing of quotes is two manners, one is to use the "quote" button on eveyones posting, or simply type <quote> the text goes in here that you want cited </quote> (you can simply copy/paste the quotable sections)

The only catch is that I have used the < > 'greater then' and 'less then' signs to demonstrate the usage, the right ones to use is the bottom set of brackets [ ].

The reason is that if I did it the other/right way, you wouldn't be able to see it. There are explaination on the forum itself, in the FAQ's section, Greg's put up several notices on the math symbols, your window for typing has several features that allow you to play with text Fonts, Colors, SIZES, and lots of other little toys of the trade, so explore!

[Brad_Ad23]

Yes actually that did help. It shows several things: One dark energy is acounted for, and does much more than dark matter (since that only interacts gravitationally as well). And it also shows how silly the notion of the universe folding on itself is. It will keep expanding. Scaling down a dimension, imagine a sphere that just keeps getting larger and larger. It won't ever fold on itself.

[Eh]

Andrei Linde posted a paper a while back on the subject of dark energy. Under some models of super gravity, the dark energy (assumed to be vacuum energy from QM) driving the acceleration would not continue to increase as time goes by. Instead, the value would eventually stop increasing, and then drop towards zero. But it wouldn't stop there - as the value would begin to take on a negative value. An omnipresent dark energy with positive preasure would then cause the universe to contract.

There was a topic about this on the old PF, but I'll see if the article is still lying around somewhere. Does anyone here know anything about super gravity?

[M. Gaspar]

From Oxford Dictionary of Science (1996) ...

Supergravity: A unified-field theory for all the known fundametal interactions that involves supersymmetry. Supergravity is most naturally formulated as a Kaluz-Klein theory in evleven dimensions. The theory contains particles of spin 2, spin 3/2, spin 1, spin 1/2 and spin 0. Although supersymmetry means that the infinities in the calculations are less severe than in other attempts to construct a quantum theory of gravity, it is probable that supergravity still contains infinities that cannot be removed by the process of renormalization. Is is thought by many physicicts that to obtain a consistent quantum theory of gravity one has to abandon quantum field theories, since they deal with point objects, and move to theories based on extended objects, such as superstrings and supermembranes, and therefore that supergravity is not a complete theory of the fundamental interactions.

Eh: I hope that was helpful. And if you can come through with recent data that supports the eventual collapse of the Universe, I will be grateful.

[Brad_Ad23]

Yes, supergravity theories are nice and all, however they have shown to be inadequate, which is why most of the research is now turned to the current big 3: M-Theory, Loop quantum gravity, and Twistor Theory (to a lesser extent than the other two)

[Mr. Robin Parsons]

*HERE* (http://www.physicsforums.com/showthread.php?postid=11626#post11626)

[Eh]

For reference, here is the article I was talking about: http://news.bbc.co.uk/2/hi/sci/tech/2346907.stm

[M. Gaspar]

I can't tell you how thrilled I am with the article you referenced.

I agree with it somewhat, except I would not use the phrase that the "Dark Energy" will turn "negative"...but believe that perhaps there will be a "trigger" (overall temperature drop, perhaps) that will cause the "Dark Energy" to convert to "Dark Matter" to start the implosion process of the Universe.

And while I agree with Prof. Linde's conjecture that the Universe will collapse, I do NOT agree that it is "doomed to disappear."

In fact, might it not be possible that it would contract to a singularity that, in turn, would burst forth into the NEXT "Big Bang".

This is a "Life Cycle" that I can live with...and that the Universe can LIVE WITH TOO!. Expanding out into a frigid eternity doesn't even appeal to the cosmologists who are proposing it. It is much more satisfying (to ME, at least) to believe the Universe is an "eternal entity of energy" that enjoys infinite incarnations via the expansion/contraction model.

In fact, as I have said before, I believe the Universe is a living, conscious Entity that evolves -- as we do -- via infinite incarnations. [?] [8)] [?] [8)] [?] [8)] [?]

But that's off topic.

[Eh]

The reference to negative energy seems to actually be about preasure. Normal matter has positive preasure, while the dark energy of the vacuum is said to have negative preasure and so does not gravitationally attract. The transformation would be that negative preasure becoming positive.

[Messiah]

Originally posted by KL Kam
the universe doesn't have a centre

Using any given point in space as an X,Y,Z axis, one may theoretically extend equidistant lines to infinity through the limitless spectrum of polar coordinates. The procedure inscribes a sphere which theoretically encompasses the Universe. By definition, the selected point is the center of that sphere - and the center of the Universe. Since the same can be done for all points, it seems every position in the cosmos is its center.

[Mr. Robin Parsons]

The center of the universe is everywhere, just that our limited perception of it allows us only to see it somewhere.

It is because the light is invisible to our eyes, all we ever see is light when it is interacting with matter, NOT when it is travelling from source, to surface, rebound, back towards surface or source, ad infinitum, sorta, it wears out in time due to interactive energy loses, hence, dark, if not replaced by more light!

It is a constant activity