If the universe came from a bang.. then what about space?

[Nisou]

WARNING: bad grammer ahead

 

I kept wondering.. since i was 5.. teachers kept telling me that "the big bang" made the universe.. but i just couldn't understand how the "universe" came from a bang.. so, from then on, i always thought that empty space resulted from the bang... (i learn later that matter/energy.. etc)

 

now, here's what i dont understand.. if the universe came from a bang.. then, what did it expand into? another universe or just space? like.. how can space go on forever,.. ive always imagined space to be a big box of empty space.. but.. sooner or later, won't you reach a stop?.. and if you do reach that "wall".. what's after that wall.??? if space loops.. then what's outside of that loop? so confused :?

[admiral_ju00]

one of the theories is that we do not see over 90-95% of the universe.

and not just the planets and or other bodies. the space is made up of super small particles(items) called WIMPS and/or Super huge items called MACHOS - aka Dark Matter.

 

then there's another theory (by Einstein) is the string theory saying that space is made up of 11 dimensions, etc.

 

currently, the telescopes have reached as far as they can(ultra deep probes) and the amount of the black(ness) stuff or gaps between galaxies is very large and more abundant. what does it mean, there may be a limit to the space or there may not and the cosmos hasn't yet expanded enough to fill in those gaps, or that the light from ultra deep, deep, deep systems(galaxies) has not yet reached us, etc.

 

as far as what's after the wall, there may either be perhaps another dimension or an even bigger space with no solid or visible bodies before another galaxy/cosmos.

 

found a good article you might want to check:

 

Scientific American

 

but i'm nowhere near being an expert at cosmology, there maybe someone here that can give better details on the matter

[Martin]

...

 

now' date=' here's what i dont understand.. if the universe came from a bang.. then, what did it expand into?...[/quote']

 

 

some of the puzzlement about the expansion of space results from

the words used to describe things

 

it actually gets easier if you know a few technical details

like, have the idea of a metric

 

a "metric" is a mathematical gadget for specifying the distance between two points

 

the basic geometry of space, its expansion, the effects of gravity etc, is captured by the metric-----it is a really efficient way of summarizing a lot of information----the 1915 einstein equation, which is the basis for Gen Rel and for cosmology, is an equation about the metric which relates it to the density of matter (or more exactly the density of energy) in the universe or whatever region of the universe you are looking at.

the density of energy in some region influences the curvature and the expansion of the metric in that region

 

now that may sound impossibly complicated but in practice it works out very simply

cosmologists use a simplified version of the einstein equation that was discovered by a russian named Friedmann sometime in the 1920s and

they use a really simple formula for the metric called the FRW metric

(for friedmann, robertson, and walker)

and this FRW metric has a scale factor in it, called by the letter a, which changes with time

 

the changing scale factor a(t) is not the diameter of the U, it is simply a scale factor in the formula for the distance between two points.

if that factor grows, and the distance between two points increases, it is called "space expanding"

 

but in the simplest and most common model cosmologists use, space is flat and infinite in all directions and always has been like an infinite sheet of graph paper. in this simple model it didnt even come from a point.

it just always has been infinite in extent---the only thing is, distances between points keep increasing as the scale factor a(t) grows.

 

and the friedmann equation simply describes how a(t) grows

it is a rather concise harmless-looking equation about the derivative

(rate of change) of a(t) and about the acceleration or second derivative of a(t).

 

it relates the first deriv. a'(t) and the second deriv. a''(t) to the

average density of energy in the U.

 

and that is why they stick in terms like "dark energy" which is a constant energy density which we dont observe----which is assumed precisely because it makes the friedmann equation model fit the data when you stick it into the equation in addition to the other energy density that we can observe or infer.

 

it may sound a bit flimsy and specious but that's because we are only humans trying to make sense of things and it IS flimsy and specious.

 

the main thing is most of the thinking involves a very simple picture of infinite flat space---expanding in the sense that the scale factor is increasing----with the rate of expansion depending on the overall density energy and to some extent also on the type of energy

 

so the expansion never had to come from a point

and it doesnt have to be INTO anything

 

(it can have come from a point and it could even be into some larger space but that is not necessary to imagine, one can make up such models but it is an unnecessary extra complication, so why bother)

[Martin]

...and the friedmann equation simply describes how a(t) grows

it is a rather concise harmless-looking equation about the derivative

(rate of change) of a(t) and about the acceleration or second derivative of a(t).

 

it relates the first deriv. a'(t) and the second deriv. a''(t) to the

average density of energy in the U.

...

 

http://www.scienceforums.net/forums/showthread.php?p=56563#post56563

 

here is a link to a SFN sticky that has the Friedmann equations

and says what the letters in them stand for

 

in the simple flat case that most of what you read refers to

the main Fr. eqn. boils down to

 

 

[math](\frac{a'}{a})^2 = \frac{8\pi G}{3}\rho [/math]

[Martin]

I believe you can ask it to be deleted, by one of the moderators.

 

thanks Tesseract, then I hope one of the moderators does delete

that "accidentally posted twice" thing

 

in the meantime since you are at a military base in antarctica there is a very good chance that you like differential equations so here is a neat thing about this one:

 

[math](\frac{a'}{a})^2 = \frac{8\pi G}{3}\rho[/math]

 

this thing

[math]\frac{a'}{a}[/math]

 

(you may have learned this already but in case not) is the same as

the Hubble parameter H(t)

which is the percentage rate of expansion of space

or the fractional rate

that is, it is the increase in the scale factor a(t) divided by the scalefactor, which makes it a fractional rate of increase in distances

 

which is what the Hubble parameter is!

 

so this equation, which is the basic Friedmann for the spatially flat case,

actually says

 

[math](H)^2 = \frac{8\pi G}{3}\rho[/math]

 

I dont know if I am saying things you already know.

 

I like this because it is so simple. A lot of things are hard in cosmology but this is beautifully simple. It says that the density at this moment

(assuming space is flat) is related to the square of the Hubble parameter, whatever it is at this moment.

 

and also that the two have been related all along. the density has been declining as the U expanded and at the same time the Hubble parameter has been declining,

because one is essentially equal to the square of the other

 

after all

[math] \frac{8\pi G}{3}[/math]

is just some constant

 

do you like this kind of thing? I am a fan of cosmology

[Vague]

I kept wondering.. since i was 5.. teachers kept telling me that "the big bang" made the universe.. but i just couldn't understand how the "universe" came from a bang.. so, from then on, i always thought that empty space resulted from the bang... (i learn later that matter/energy.. etc)

 

 

This is a very interesting and rather the biggest puzzles of all time. Space is the only "thing" that is supposed to be absolutely seperate. It has been there you can say before the beginning of the time and will always be there. It has no end and no beginning, it is infinite in all dimensions. It does not affects anything, niether can affect it. Although the Einstein has described space that can be folded and moulded by matter to produce gravity, I believe we have yet to come to a conclusion over it.

 

And yes Universe ought to have a beginning as the Doppler affect suggests that it was too close in past to get exploded from a singularity and you cannot expect something to be there since infinity whose overall structure has always been changing.

 

<b>This is a great topic to discuss, any comments from anyone?</b>

[Martin]

Vague, I agree with part of what you say:

This is a very interesting and rather the biggest puzzles of all time.

 

<b>This is a great topic to discuss' date=' any comments from anyone?</b>[/quote']

 

 

but I disagree with what you say here:

 

"Space is the only 'thing' that is supposed to be absolutely seperate. It has been there you can say before the beginning of the time and will always be there. It has no end and no beginning, it is infinite in all dimensions. It does not affects anything, niether can affect it. Although the Einstein has described space that can be folded and moulded by matter to produce gravity, I believe we have yet to come to a conclusion over it."

 

You are saying einstein's 1915 theory of gravity is wrong, but has been the accepted theory that scientists use for over 80 years. It is the prevailing picture and in it space IS affected by matter---matter curves spacetime and spacetime guides how matter moves.

 

the old idea Newton had of absolute space (such as you describe) was thrown out a long time ago.

 

what you say about space ("It does not affects anything, niether can affect it. ") is not what today's astronomers and cosmologists believe.

 

What scientists mean by a singularity can consist of many points----in its technical meaning a singularity does not have to occur just at one single point.

 

In the conventional theory there is a singularity before which one cannot say that space or time or matter exist. As one works backwards in time using the einstein model one runs up against a barrier where the model stops working, it gets infinite answers like when you divide by zero.

that is the singularity.

 

when cosmologists improve their model they may be able to do away

with the singularity and run it even further back in time to a time before

the big expansion started

 

then we will be able to say that space and matter existed before

 

but the model we now use (which handles both matter and space together, not separately, each one controlling the other) runs into a singularity and stops working so there is no space (or matter either) before a certain time

(there is not even any "before")

 

this will probably be fixed, there already are a dozen or so scientists who now say they have an improved model (like the 1915 einstein model but including quantum effects) which overcomes the singularity and runs on back further.

 

there is a German science journalist named Rudy Vaas who has written about the removal of the singularity by these people's research

Here's a link to his article.

http://arxiv.org/abs/physics/0403112

click on PDF and you will get a PDF download

it is a good article called "The duel, Loops versus Strings"

[Vague]

Thanks for all the info Martin! I did not mean to completely rule out Einstein’s conception of space. But I also do not completely agree with it. You know that Space is just an expanse, ever wondered why zero does not affects any other number, when it is multiplied, subtracted or added to them? I am not taking division into consideration because that physically cannot happen.

 

My version might go in like this...Dirac showed that the whole Universe is filled with negative energy that cannot be usually seen and we also have positive energy that we can. Because of this positive and negative energy matter is filling up the complete Space, there is no void left. That would mean that what is curving is not in fact Space, but these negative energy particles. The geometry of Space was put in because physicists were not able to define gravity properly and as you also know that gravitons are also considered negative energy particles, that points that it is these negative energy particles that re responsible for the force of gravity and not the geometry of Space.

 

I wish if I could discuss all this with Einstein himself. It would have been great to hear his version then. Any physicists on this forum?

[admiral_ju00]

Any physicists on this forum?

yeah, lots.

 

swansont and radical edward have both a Ph.D in it. then there's YT2095, and a host of others.

[Vague]

"like.. how can space go on forever,.. ive always imagined space to be a big box of empty space.. but.. sooner or later, won't you reach a stop?.. and if you do reach that "wall".. what's after that wall.??? if space loops.. then what's outside of that loop? so confused :?"

 

 

Missed to answer this one. It seesm as if you regard Space as "something" but anything that comes up after the wall you are talking about, would also occupy space or volume...so the Space just keeps on going on and on and on and on...

[Nisou]

"like.. how can space go on forever' date='.. ive always imagined space to be a big box of empty space.. but.. sooner or later, won't you reach a stop?.. and if you do reach that "wall".. what's after that wall.??? if space loops.. then what's outside of that loop? so confused :?"

 

 

Missed to answer this one. It seesm as if you regard Space as "something" but anything that comes up after the wall you are talking about, would also occupy space or volume...so the Space just keeps on going on and on and on and on... [/quote']

 

im just confused now, is space made of MACHOS and WIMPS.. or not? like.. im talking about the "empty space".. where there are no gases.. no light, no energy, nothing.. empty space... nothing can exist here

 

if there were no machos and wimps, there would be like.. no nothing.. and no anything right?

 

how can there be TOTALLY empty space? and how can our macho/wimpy space go on forever, i still picture space as one big box.. and outside of that box is .. like.. SO empty that there is no emptiness

[admiral_ju00]

I believe the current theory on this sais that there may be both, the MACHOS ans the WIMPS.

[Martin]

Some striking turns of phrase especially where Nisou says

"SO empty that there is no emptiness."

which could be a line by a good poet.

I will try to respond too, but I dont see how right at the moment.

 

 

Nisou:

"like.. how can space go on forever,.. ive always imagined space to be a big box of empty space.. but.. sooner or later, won't you reach a stop?.. and if you do reach that "wall".. what's after that wall.??? if space loops.. then what's outside of that loop? so confused :?"

 

 

Vague:

Missed to answer this one. It seesm as if you regard Space as "something" but anything that comes up after the wall you are talking about, would also occupy space or volume...so the Space just keeps on going on and on and on and on...

 

Nisou:

how can there be TOTALLY empty space? and how can our macho/wimpy space go on forever, i still picture space as one big box.. and outside of that box is .. like.. SO empty that there is no emptiness

 

------------------------

 

I dont see why space cant keep going on and on. that is what it looks like it does when you go outside on a clear night. What is wrong with simple straightforward infinite space.

 

And no "outside"

 

All I can see that might be a mental stumbling block in this case is that it means there has to be unlimited amounts of stuff----unlimited numbers of galaxies and stars and dark matter constituents (whatever you think they are and choose to call them). Whether or not you find it a problem that the stars keep going and there's no limit to how many-----I guess it depends on you.

[cperkinson]

GOOD QUESTION... but i like to dismiss these forms of wonderment for they are unanswerable within our retrospective lives.

[iNow]

GOOD QUESTION... but i like to dismiss these forms of wonderment for they are unanswerable within our retrospective lives.

 

I disagree. The only thing which makes questions such as these "unanswerable" is the attitude you demonstrated above in your post. Ever heard of the self-fulfilling prophecy? If you give up before you begin, then you're right... There will be no answers. However, if you make seeking knowledge and finding answers part of your lifestyle and worldview, then it becomes much more difficult to write off our potential abilities and achievements in the times to come.

 

There's always an answer, we may just not understand it or like what it is.

 

 

 

EDIT: Btw... This is a five year old thread, and nothing was really added by your post necromancing it.

Edited June 15, 2009 by iNow