purintjp

The idea is that if there's enough mass within the universe the gravity between all the masses will become stronger than the original expanding-velocity given to the masses from the big bang.

 

This means that slowly expansion will slow down and everything will come together again.

 

Quite what happens then is more theories. It could all just get a bit mashed up and it'd be a wasted universe... it could form into what was there before the big bang... from then the big bang could occur again and you'd get a cycle of universes.

Why does it have to be gravity to cause the contraction ? Since it

expanded due to energy released, could not a reduction in energy begin

to slow and maybe contract spacetime until gravitation masses became

close enough to start to pull everything back together to cause a big

crunch ? I tend to accept this possiblity more than the original big

bang expansion from a singularity. I just don't like the something from

nothing explanations, although a big bang from a big crunch still does not

explain where everything came from.

I just always though that like in a vaccuum (if one really exists) that positive and negative matter can appear and dissapear (positive and negative energy), in that you can "borrow" energy from the universe as long as you pay the energy back quik enough. In this, from nothing (singularity, "before" the big bang) why cant you borrow "near infinite" positive and negative energy (mass), and as we know mass creates a "time warp" (like a black hole). So in an essence the universe only existed for an instant, yet because of its immense gravity (like a black hole) it bends wat we perceive as space time enough for us to perceive it as near infinity (near infinity, wasnt that dumb).

(if you put an object next to a object with immense gravitational field it would age relatively lower than everything observing it that is not near a large gravitational field)?

(I have trouble differentiating zero from infinity, in the same way i have trouble seperating the speed of light from a physical distance. It is hard to express zero without infinity and infinity without zero. We apparently know 1-1 =0 , also f(x) = x-x = 0, whether x be infinity or zero, and infinity is best expressed as f(x) = x/0, in that x can be any number positive or negative)

 

just one of my theories atm,

 

I will soon come up with a better one when i learn more

Adam, you are not the only one who thinks about this kind of stuff. I

posted the following some time back.

Just how empty is space, really. There are all the various radiation spectra and things like neutrinos and other exotic particles rushing through space pretty much everywhere. Not to mention stuff we probably can't even detect.

Maybe the idea of 'nothing' does not even exist.

I think that the proof of nothing is tied to the proof of infinity.

Is not the best definition of infinity as 'something' divided by 'nothing' ?

They both could be just pure mathematical concepts.

I know scientists are dead set on using mathematics to describe

everything but I doubt they will.

I often wonder if mathematics is not a victim of it's own precision.

Everything seems to break down around 0 and infinity.

What is it that is exactly equal that is larger than quantum level ?

Are we 100% sure that even quantum level stuff is equal down to

the most infinite detail ?

So based on what you are telling me, it is certain that given what we

currently know about expansion and cluster formation that we can

probably be sure that at some point in time Andromeda was nudged

into our path (or vice-versa) or that the velocity was altered at some point ?

If so, could it have been collisions that it had with other smaller galaxies ?

Thank you Martin for the reply. I had not heard of the measuring to

the CMB until this very thread.

What you replied goes to the very heart of my original thread post.

If you assumed that the two galaxies are 12 billion years old and ran

the scenario backwards the distance between the galaxies would

have been 2.5M lt/yrs + 5M lt/yrs to equal 7.5 M lt/yrs. I assume

that the Hubble constant would have been different 12 Billion yrs. ago

but the math is probably beyond me. Seems like there might be a chink

in the armor of something.

Good stuff guys!!

I hadn't ever heard about the "Great Attractor". Can someone provide a

well-respected link to learn about it.

Also, I was wondering how far away would we have to be from

Andromeda before gravity would be overcome and the expansion of

space would take over. (Approx.- I'm assuming that no other gravitational force would interfere)

Thank you Martin for your always concise explanations and time.

I hadn't considered the possiblility or them orbiting each other.

That being said I did some quick calculations and using a speed

of 130 km/s being the total approach speed giving a speed of

about .0004*c they would only have traveled about 4,000,000 lt/yrs

in 10 billion years. I know that's a rough estimate but doesn't seem

to give enough time for many orbits. Am I missing something ?

As I understand it, the galaxies moving towards us are in our local

galactic cluster. Since Andromeda is moving towards us at the current

time I was wondering if using the shrinking universe analogy

that is used to speculate that most galaxies that are moving away

from us at one time were much closer to us at creation would

suggest that Andromeda was farther away from us at our creation times.

It would seem that this would have to be true or Andromeda would have already collided with us during expansion.

Would the distances between now and then jibe with the rate at which

it is coming towards us without being too far away at creation to

be affected by gravitational forces ? It would seem that it has been

coming towards us for an awfully long time to still be 1 million light years

away.

The biggest problems with the balloon analogy is not that it is 2D; this is just a simplification to make the expansion of the universe comprehensible to us normal humans who cannot think beyond 3D. That the balloon analogy is 2D rather than 3D, well try to imagine an expanding hypersphere in four dimensional space. Good luck with that!

 

 

There some bigger problems with the balloon analogy:

• It assumes a finite universe. That remains an open question as far is I know.
  
• It implies that the universe is embedded in a higher order Euclidean space; that a Euclidean point of view is somehow preferential to a non-Euclidean description.

 

Once again, though, the balloon analogy is just that -- an analogy. It's purpose is to illustrate the expansion of the universe in a way that is easier to grasp than the rather abstract mathematical description.

I don't particularly like the balloon analogy either. I don't think that the

hypersphere is really all that hard visualize. As long as you consider the

balloon model expanding thru time and space creating a sort of pseudo-

space/time representation you pretty much have the hyper-sphere.

It is also a very useful representation of how light has to travel from the

early universe to finally reach us. A cross-section of the hypersphere

shows this quite well.

All that being said, I still have a problem with the traditional BBT.

It seems more likely to me that the universe is cyclical in nature and

expands till energy is mostly gone and there are nothing but heavy elements

left which will combine in a relatively large and no where near infinitely

small density and space and will then go critical after breaking down into

the universal building blocks. Still a big bang but without the faster than

light expansion. Trying to understand what started it all is no doubt a futile

effort. I just don't understand why so many people cling to theories that

predict seemingly outlandish results. I guess everybody is entitled to his

opinion.

Some other parts of your post confuses me a little, so I want to clarify a few things:

- The Universe is NOT thought to be a spherical thing in a big emptyness in the Big Bang model, the Big Bang was not like an explosion of matter in space, the Big Bang is about expansion of space, which never halted and is still going on.

- Light can never escape from the universe, the universe is by definition everything, wherever the light would go, would therefor also be included as a part of the universe.

- The universe was not holding back light like a black hole before the time of ~377,000 years, instead it was so dense that the light that was inside it, could not traverse through it. Think of it more lika a room so filled with smoke that you can't shine through it with a flashlight, after the recombination the smoke cleared up and the universe became transparent.

I was only positing a spherical model for ease of calculation.

Without some sort of explosive impetus why would space expand ?

I wasn't referring to light escaping the universe, I was referring to the

release of light from the singularity into space as it began to expand.

As far as light being held back by dense matter, it would seem to me if

I were able to stand outside that singularity I would be able to see

something that hot and dense unless it had black hole charactistics.

Is that what you are claiming ?

If not;

What about light at the extreme edge of this singularity, what would be

holding it back ?

I'm assuming that the universe never got smaller than 377,000 LYrs.

The Big Bang is AFAIK not thought to be the beginning of the Universe, and we already have mathematical models, although still in early stages and very speculative, that reaches back in time beyond the ignition of BB event.

 

"The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation."

http://en.wikipedia.org/wiki/Big_bang

 

"One of the main problems with the Big Bang theory is that at the moment of the Big Bang, there is a singularity of zero volume and infinite energy. This is normally interpreted as the end of the physics as we know it; in this case, of the theory of general relativity. This is why one expects quantum effects to become important and avoid the singularity.

 

However, research in loop quantum cosmology purported to show that a previously existing universe collapsed, not to the point of singularity, but to a point before that where the quantum effects of gravity become so strongly repulsive that the universe rebounds back out, forming a new branch. Throughout this collapse and bounce, the evolution is unitary."

http://en.wikipedia.org/wiki/Big_Bounce

I was thinking about this and I was wondering if it were

possible that the universe were cyclic and that it had

collapsed to the point that BBT theorists posit had

occured around 380,000 LYrs just before light is able to

escape and then big-banged into existance. I don't have

the math experience to calculate what the density would

have been at that point but I would be curious if anybody

has ever calculated that based on what the believed

density is today at 13.7 BLYrs to see if it might make

sense. (Assuming a spherical universe).

I wonder if there would be any correlation to

the density required to create a black hole and the

calculated pre-BB density. It is interesting that at those

points light could escape neither of those. Maybe all the

basic building blocks of matter have always been here

and were not created by the expansion of a point singularity

as a big bang from nothing.

It is my belief that we will never be able to integrate the universe through

mathematics. It is a victim of its own precision. Everything seems to

break down when it approaches zero or infinity. There seem to be levels

of what I like to call relative infinity or relative zero. We are insulated

from these areas and for good reason. Relative infinity is easily less than

1000 light years and any attempt to derive anything of practical value is

probably a waste of time. Our best bet is the near practical zero of

Quantum mechanics which may offer some useful practical applications

for energy production or other scientific use. The single most important

thing for science to discover is whether infinity or nothing (zero) truly

exists in our relatively closed system. Only then will we understand the

unfathomable universe.

I guess I was trying to make a point that it is possible to travel away from something faster than the speed of light if you are being "carried" rather then accelerating. It is pretty hard to wrap your mind around the difference.

As far as being closer to the Milky Way, I believe that practical infinity is easily less than a 1000 light years away and although I love all the gee-whiz stuff that comes out of scientific research I think it is probably a colossal waste of time to ascribe any sort of practical application or use in today's world. I think we would be better

served to allocate more money and time to Quantum Research as we are far more likely to reap any real world benefits. Of course, I am just and idiot without scientific credentials.

I was under the impression that far distant galaxies are a lot farther away than can

be explained by the age of the universe. We are seeing only the light from the very

beginning of the universe of the galaxies farthest away. Who knows exactly where

they are now. If you look at my post in Cosmology and Astronomy 'Big Bang Paradox'

you will see Martin trying to explain it to me. Perhaps I misunderstood. If so, mea culpa.

I totally agree, Jill, but just to be pedantic, as we currently understand the cosmos, no mass can travel faster (or at) the speed of light.

 

And yet most scientists believe that entire galaxies can travel away faster

then light as long as they are "carried" along by the expansion of

space/time. It seems we just need something to "carry" us along to

achieve the same result. Who knows what that might be.

Thanks for the info. Here in Los Angeles we have some difficult

atmospheric and illumination issues. I only had binoculars but it almost

appeared as a comet.

Can anyone tell me what the very bright object in the sky south of

Los Angeles approx. 30 to 40 degrees declination ? It seems too bright to be a planet. Time is 10PM. Thanks.

The vast majority of solid matter is empty space. If a Hydrogen nucleus was the size of a paperclip and sitting in the centre of an American football stadium, the electron would be outside the stadium.

Just how empty is space, really. There are all the various radiation spectra and things like neutrinos and other exotic particles rushing through space pretty much everywhere. Not to mention stuff we probably can't even detect.

Maybe the idea of 'nothing' does not even exist.

I think that the proof of nothing is tied to the proof of infinity.

Is not the best definition of infinity as 'something' divided by 'nothing' ?

They both could be just pure mathematical concepts.

I know you scientists are dead set on using mathematics to describe

everything but I doubt you will.

I often wonder if mathematics is not a victim of it's own precision.

Everything seems to break down around 0 and infinity.

What is it that is exactly equal that is larger than quantum level ?

Are we 100% sure that even quantum level stuff is equal down to

the most infinite detail ?

Flat universe

If the average density of the universe exactly equals the critical density so that Ω=1, then the geometry of the universe is flat: as in Euclidean geometry, the sum of the angles of a triangle is 180 degrees and parallel lines continuously maintain the same distance.

Absent of dark energy, a flat universe expands forever but at a continually decelerating rate, with expansion asymptotically approaching a fixed rate. With dark energy, the expansion rate of the universe initially slows down, due to the effect of gravity, but eventually increases. The ultimate fate of the universe is the same as an open universe.

http://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

As I understand it, it is believed that the universe is flat as stated above

by current thinking.

I was wondering how those lines stay parallel when they get beyond our

local galaxy cluster and are affected by the expansion of space so that

they are no longer parallel; ie., as two laser beams shot parallel into

space. It seems to me that the expansion creates a defacto curved space.

Perhaps a visit to Wikipedia will help: http://en.wikipedia.org/wiki/Cosmological_redshift

 

The key concept here is that the Hubble constant is not really constant. If I understand your question correctly (and there's no guarantee of that since you say I didn't answer your question with my previous post), then the variation of the Hubble constant over time and the Hubble sphere increasing or decreasing over time seems to have it covered. If I still don't understand your question, then I'm afraid I'll have to give up and admit defeat.

Thanks for your time and patience. I'll need some time to digest most of this.

I did not realize that the 'constant' varied with the cosmological model.

Is that flat, closed, or open ? Why only for small redshifts ?

How would you conduct an experiment to see how vast distances through

curved space would affect wavelength or can it be extrapolated ?

I understand all you have stated and don't disagree generally.

What I was referring to was an effect to the red shift

as it pertains to the Hubble constant. I am wondering

how we can end up with a scalar linear constant when light

has been travelling in curved space which is no where near

linear. It would seem that the light could be distorted at

varying degrees during it's journey based on varying curves

as the Universe expands since it has supposedly expanded at

different rates.

Can we really trust this constant ?

Do you think maybe the original percussions are searching for an atmosphere to slow down into and when they reach the threshold of finite "small"ness they begin to fall back on its origination in the form of energy from sound? which in turn creates the appearance of gravitationally lensed light?

Huh ????

I was reading an article about the properties of light and

it was stated that light does not react directly to a

gravitational field but instead reacts to the space-time

curvature associated with the field.

Since light from distant galaxies (or even close ones) does

not travel in a straight line from the source to our

observations and instead travels through the expanding space

of a hypersphere in a curve varying with the distance from us,

is this not a de facto curvature of space and could it have

implications for speed and wavelength (specifically the red-

shift) variations ?

With such staggeringly massive black holes being found one can only wonder if a

cosmic-sized black hole could exist somewhere beyond our observations. Has that

ever been postulated ? Could one of those have fed our universe as a white hole ?

Thanks for the excellent explanation. If I understand correctly, you are saying that t = 0 is just another tick from a previous state. It does, however, cause me to wonder if the reality of 'nothing' has ever existed or will exist. If it doesn't then would not time be eternal ?

I put the comment about the History channel knowing that someone would say exactly what you said. I could not have put it better. This is why so many misconceptions exist and I wish all the scientists could get on the same page and keep this from happening. Unfortunately, like you said, the dumbing-down of America is and has been in full swing for some time now.

I agree with that. As long as there is matter and energy in the universe isn't there always some movement at the quantum level or the cosmic level ?

I was thinking more in terms of the 'primordial atom'. Did it have it's own space or was it created out of nothing ? I guess what I'm trying to understand is what time = 0 really means.