Time and Space

[The1exile]

What is the area called that the universe is expanding into?

The next door neighbours.

[Malkithe]

What is the area called that the universe is expanding into?

Only two things are real: Atoms, and the void.

[Bouncer]

Only two things are real: Atoms, and the void.

really?.............

what about sub-atomic particles?

and energy?

and the fundamental forces of nature?

and is time not real?

[DAZMCFC]

What is the area called that the universe is expanding into?

Only two things are real: Atoms, and the void.

i`m real, i think .

[unriggable]

Except for human stupidity, nothing lasts forever.
Space is not infinite. Even the Universe has boundaries y'know.

No it doesn't, theres just nothing there.

[Bouncer]

Except for human stupidity, nothing lasts forever.
Space is not infinite. Even the Universe has boundaries y'know.

No it doesn't, theres just nothing there.

unless you think the universe is composed entirely of nothing,
then you are actually defining a boundary
- between something and nothing.

[mandalorian2298]

Time and space scare me. A lot. Mainly because they're infinite. And we have no idea what time is anyway because we can't experience it. We don't even know what space is like because we can't look at it.
We can't "step out" of time and space and see what they are because they are infinite.

"You can't see the wood for the trees"

What makes you think they are infinite? If they were, what is the chance of enough matter gathering in one place to form the known universe? Therefore, the only reasonable assumption (assuming that Time and Space are infinite, of course) is that there is roughly the same matter density everywhere, thus meaning inifnite matter. If there was infinite matter, then the entire universe would be as hot a the surface of the sun. Sinse this is plainly not true, I think we can discard the infinite space and time theory.

(This is all just basic logic on my part, with no actual research. Please tell me if my logic is faulty in some way)

I do believe that your logic is faulted. You see, if there is infinite matter, disperesed over infinite amount of space then the density of the matter could remain quite low, although the total amount of matter is infinite.

If the average density of the universe is enough to form stars, then YOUR logic is faulty.

Why would the avarage density in any way affect the possibility of stars being created?
It is obvious that there are more and less dense areas in the Universe (for example, are occupied by Earth's atmosphere is much less dense then the are occupied by Earth's crust). This being so, the avarage density of Universe and the density of Universe in the area occupied by a star (or an area in which a star is being created) are mutualy unconnected issues.

If stars can be formed outside of the known universe, then there would be an infinite number of stars. If there were an infinite number of stars, then every possible line would eventually impact with the surface of a star. This, coupled with infinite time (the radiation from all the stars has had an infinite amount of time to reach us) would mean that the entire sky would have to glow as hot as the surface of the sun.

Of course, if the average density of the universe is too low to form stars (and we live in a pocket of enhanced density) then my logic is proved false.

EDIT
Actually, I'm still correct even if the average density is too low to form stars, since there will be an infninite number of density anomalies, which will still make everything as hot as the sun.

You are forgeting that Earth doesn't just recieve and store heat. Earth also releases some of it's heat into the cold near-vacuum that surrounds it.

[The Kurgan]

Stars COULD be created when areas of matter gather closely together, because matter is not stationary in space, SO that could mean that the average density of the universe is very low but that there occasionally clumps of matter gather together.

[unriggable]

Except for human stupidity, nothing lasts forever.
Space is not infinite. Even the Universe has boundaries y'know.

No it doesn't, theres just nothing there.

unless you think the universe is composed entirely of nothing,
then you are actually defining a boundary
- between something and nothing.

But see then there is that boundary everywhere, wherever there is nothing that boundary exists.

[Neutrino]

Why would the avarage density in any way affect the possibility of stars being created?

Can't make stars if you don't have enough material to start fusion

It is obvious that there are more and less dense areas in the Universe (for example, are occupied by Earth's atmosphere is much less dense then the are occupied by Earth's crust). This being so, the avarage density of Universe and the density of Universe in the area occupied by a star (or an area in which a star is being created) are mutualy unconnected issues.

Hmmm?
But the star is still part of the universe, thererfore part of the average density. The density inside a star may be tons per cubic metre and the density of interstellar space a hydrogen molecule per cubic metre, but they still add up to an average.

What I meant is that if the average density of the unknown universe is dozens hydrogen molecules per cubic lightyear, it is pretty unlikely that anything meaningful will form (though, if space, matter and time is infinite [or even just 2/3] it will still happen an infinite number of times).



You are forgeting that Earth doesn't just recieve and store heat. Earth also releases some of it's heat into the cold near-vacuum that surrounds it.[/quote]

[unriggable]

Whoa, shit. I just watched 'the universe' and they had an episode about the Big Bang, I suggest all of you watch it. It's weird shit.

[Jehan]

Neutrino, dude i think you've missed something here, the density of the whole universe, is somewhat irrelevant to whether or not stars form, all you need for stars to form is a slight difference in density to result in a gravitational collapse which pulls matter in, if you have enough matter a star will form. So basically we have a situation where in the very early universe, quantum fluctuations, which fill all of "empty" space, causes the slight density fluctuations, which leads to matter forming into clumps. in none of this is the space-time continuum brought in.

The universe could well be infinite without containing infinite matter, its just infinite in a particular sense which is hard to comprehend without a different method of geometry. As far as i understand the hypothesis that the universe looks the same from all points, looking in all directions, relates to the fact that there is no centre of the universe, which comes back to the fact that you cant define the size, or shape of space-time. ie its not possible to define something in relation to itself. Bouncer made me laugh on the page before, when he said that space-time is expanding, expanding with relation to what??? space time???, you cant define a spatial dimension expanding, since expansion is defined by spatial dimensions, if space time expands it makes no difference to the things "inside" or "outside" since everything will "expand" in the same way.

[Bouncer]

you're confusing scalular expansion (where absolutely everything gets bigger) with the actuality of metric expansion (where only the space between objects gets bigger). the earth, planets, stars and galaxies are
not getting any larger but the distance between galaxies (or galactic clusters) certainly is. (imagine the currants in a rising cake - the sponge expands, not the currants).

this expansion of space-time has been measured, documented and analyzed for many years now and is amazingly well understood. indeed, einstein's general theory of relativity results in an expanding universe. cosmologists can now measure the rate of expansion (80000 k per parsec)and from that the size and age of the universe (around 13 billion years at the last calculation).

as for the geometry of space-time we're left with 3 simple choices - flat, curved or open. our local geometry is flat but that may change at further reaches of space.

space-time is inherent in the fabric of the universe, therefore the expansion of the universe is the expansion of space-time - it has been defined and debated, and it certainly has measurable effects on everything inside it.

[unriggable]

I had an epiphany.

Now Einstein thought that time and space where a single thing, called 'timespace'. Now I realized that if you draw a grid on a 2D piece of paper, to show the effects of a black hole (in 2D) you need to 'stretch' the paper downwards so the grid is warped and the spaces in the grid are farther apart as you get to the center of the black hole. So it requires a 3D space to really understand a black hole in 2D, therefore there are at least 4 dimensions in space, possibly being gravity.

This fits with the idea that time speeds up as you get under heavy influence of gravity.

Agree? Disagree?

[mandalorian2298]

space-time is inherent in the fabric of the universe, therefore the expansion of the universe is the expansion of space-time - it has been defined and debated, and it certainly has measurable effects on everything inside it.

Pray tell me at which speed does Time expand?

[Bouncer]

lol, good question!

time is a quality of the universe, so the quality of time expands right along with it at the rate of around 80 k/s per megaparsec.

more on space-time....
space-time can be said to be a totally human construct - a model, if you like, to co-ordinate and better describe relativity - its not space with time tacked on - but 3 dimensional space with time making a fourth dimension.

each dimension - height, width, breadth and time - are required to describe relativistic events in the universe. time cannot be separated from the three dimensions of space as the size of those dimensions depends on an object's velocity relative to the speed of light.

ultimately, objects, or matter, warp space-time - and warped space-time affects the way objects move.

[Jehan]

through what dimension do you measure the expansion of a dimension, also, i get that the distances between objects is expanding, but that doesn't necessarily mean that the dimensions themselves are "expanding" because that doesn't really make any sense, that would have no measurable effect.

[unriggable]

space-time is inherent in the fabric of the universe, therefore the expansion of the universe is the expansion of space-time - it has been defined and debated, and it certainly has measurable effects on everything inside it.

Pray tell me at which speed does Time expand?

1 second per second.

[Bouncer]

hi jehan -
your confusion lies in your use of the wrong terminology -
the universe is is known to be expanding because we continue to observe a regular increase in each of its spacial dimensions.
in the same way that i have expanded since being a baby due to an increase in my height, width and breadth
- its as simple as that.

[Jehan]

dimension or the measurements defined by dimensions? seriously, i think your missing the point which i brought up with my physics lecturer, if we take the cause of the universe to be that dimensions are expanding, then we wouldn't see any difference, expansion is something defined by dimensions isn't it? think about it for a sec, if a dimension were to expand then everything defined by it would expand as well, wouldn't it? so say we a have a ruler and we measure a distance on a particular axis, if the dimension on that axis were to expand, the ruler would expand, so we wouldn't measure any change. But i think i might be missing something here, is the red shift observed fitted perfectly to what would be expected if the red shift were due solely to the relative velocity of the source, or is it more red-shifted than that, suggesting the the dimensions are expanding and causing the wavelength of the light to get longer. If that is the case then we have to suggest that matter is not affected by dimensions in the same way that light is.
can you also explain to me how there is no place in the universe where you could look around and not see stars in a particular direction? how does that work?

[OnlyAmbrose]

Time and space scare me. A lot. Mainly because they're infinite.

What makes you say that?

[Bouncer]

hi jehan -
your definition of dimensions needs clarifying - foremost, dimension is a direction. sure you can add a value to it to make it more meaningful, but what's more important is that dimensions are a property of things (space-time, my head etc) they do not exist on their own, they must refer to something ie. the universe is expanding because the values of its dimensions are increasing.
so it might help jehan, if you dropped the 'dimensions are expanding' idea, it just doesnt make any sense without a reference to something.

i'll try to get back to you on those other points when i've finished me tea.

[daddy1gringo]

Pray tell me at which speed does Time expand?

Time expands when you are waiting for the new recruit to play his turn so you can take him out.

[daddy1gringo]

They only seem infinite as we as a race are only exist in 3 dimensions. That is out of a total of 7.

Now that's interesting. Are you just being flippant or have 7 dimensions been enumerated/theorized?

[Bouncer]

hi jehan -
rushed my last post - so i might add, it would also help to use the term 'increase' rather than 'expand' in regards to dimensions - even if it is referring to something. things expand and, strictly speaking, dimensions do not - but they have values that may change.

space (the final frontier) is stretching - carrying the galaxies (or galactic clusters) along with it like staples fixed to a stretched elastic band. if each staple is initially 20cm from its neighbours, and at some point during stretching is 30cm distant, then their relative distance has increased by 10cm. and its distance to all the other staples has also increased, exponentially if you like.
of course, the length of the elastic band is also increasing, and as it stretches, exerts a small force on each staple, trying to pull it apart. but the weakness of the force and the structural strength of each staple makes that unlikely in the near future.

as all the staples are moving away from each other, a light source, attached to one of the staples would, ideally, exhibit a redshift when it reaches another staple. the further the light has to travel the greater the redshift. by using a formula the amount of redshift can be expressed as the speed of recession of the source.
this mechanism works fine for staples 'in the same neighbourhood' as the source, but not for light sources at greater distances.

now, to keep the analogy going, imagine that the light travels along the stretched rubber band the same way it does space. in contrast to its effect on matter. the stretching has a profound effect on light, increasing its wave length relative to the distance traveled and therefore, exhibiting a redshift . stretching space caused the redshift and so is known as the cosmological redshift. the amount of redshift received can be used in a different formula, to give the perceived recession of the source.
further calculations will show the rate of the expansion of space, and therefore the universe.

thats all for now! hope it was a help.