Does Space really go on forever?

[carlos_dfc]

Recommended reading:-
'Bang' - by Patrick Moore, Chris Lintott, and Brian May

In the last chapter it describes the current thoughts on how the Universe will end - and sadly, it will be with a whimper....
There isn't enough matter in the Universe for gravity to slow down the expansion and cause a retraction.
All stars will eventually burn out, some will go with a bang (supernova) with the shockwave causing nearby gas clouds to collapse under gravity and form new stars. But eventually matter will become so spread out, that this will become rarer and rarer, until it stops a;together - the Universe will become a very cold, dark, ever-expanding place - inhabited by only black holes, ever-slowing pulsars, and dead star 'cinders' orbited by cold dead planets.
Time frame for this is well beyond the 5 billion years that our Sun has left, several times as long in fact, the Earth will be long gone by then, and if the Human race is still around, wherever they are will be a very cold, dark place

[Ipso Facto]

Originally Posted by carlos_dfc

Recommended reading:-'Bang' - by Patrick Moore, Chris Lintott, and Brian May

In the last chapter it describes the current thoughts on how the Universe will end - and sadly, it will be with a whimper ...

How old is the book - I wasn't aware that Patrick Moore was still an active author and that leads onto my second question ...

... There isn't enough matter in the Universe for gravity to slow down the expansion and cause a retraction.

... Does that hypothesis include dark matter?

[carlos_dfc]

Originally Posted by Ipso Facto

How old is the book - I wasn't aware that Patrick Moore was still an active author and that leads onto my second question ...

It was originallly published in late 2006, with an update, late last year, written in conjunction with fellow Sky at Night presenter Chris Lintott (a cosmology expert) and Queen guitarist Brian May, who is an accomplished Astronomer, and Physicist.
Amazon.co.uk: Bang! The Complete History of the Universe: Books: Brian May,Sir Patrick Moore,Chris Lintott

... Does that hypothesis include dark matter?

Yep - If dark matter exists, that is.....
Personally - to me anyway - the whole idea of 'dark matter' smacks of a 'fudge' to cover up a lack of complete understanding - a bit like Einstein's original idea of a 'cosmological constant' (but that's another story)

But if dark matter does exist, and even if there is 10 times as much dark matter as 'normal' matter (as it is thought) then it will still only add up to about 10% of what is required to stop the expansion and cause a contraction.

[hsl]

The black nothingness of space isn't what we call the Universe is it? The universe is expanding into that nothingness. No one could possibly know if that nothingness comes to end somewhere, or what might be past that point!

I think that Birchy was asking about space (nothingness) and not the universe. And there's no way for the nothingness to crunch in on itself because it's all that would be left if a crunch happened



I know this is a separate thing, but how do we know how long the sun has left, or the universe?

[carlos_dfc]

Originally Posted by hsl

I know this is a separate thing, but how do we know how long the sun has left, or the universe?

We now know exactly how stars work - and the lifespan of a normal star (like our Sun) is entirely dependant on it's mass.
Higher mass stars generate much more gravity, so the nuclear reactions in the core run much faster.
It sounds counter-intuitive - but the more massive stars burn out MUCH faster than the less massive ones.
We know that a star the size of our Sun, uses up it's hydrogen fuel in about 10 billion years - and geologists have worked out the age of the Earth at about 4.5 billion years - add the (roughly) half a billion years that it takes a planetary system to form, then take that 5 billion from the total of 10 billion.
And we are left with roughly 5 billion years before the Sun starts to run out of hydrogen, and expands to become a Red Giant, and turns the Earth into a huge cinder.

the Universe is another matter - physicists have worked out that the Universe is currently about 13.8 billion years old - and as above, it isn't expected to ever end - just continue expanding, and cooling forever.

As for what is beyond the 'edge' - when we say 'nothing', that doesn't really cover it.
'Space' is within the Universe - beyond the Universe.......
If there's nothing - then it's difficult for us to imagine such 'nothingness' - there isn't even empty space as we know it.

Then - we come to the idea of 'Multiverses' - the possibility that our Universe is just one of an unimaginably large amount, like a vast expanse of soap suds, each 'bubble' being a self-contained Unverse.

[hsl]

I wasn't doubting that we know, just HOW we know??? I don't suppose anyone could answer that here though, it would take too long probably.

The life of a star doesn't seem like something anyone on this planet could work out to me. I have never studied or even really thought about this kind of thing though, but it fascinates me.

It's not difficult to imagine nothing imo - the big bang must have happened in the same nothingness that our universe is expanding into. All the dust, stars, planets and black holes are hanging in the same thing. Our universe is expanding into the same nothing that it was created in (if it was.)

Why wouldn't there be other universes expanding somewhere else in the nothingness of space, from there own big bang or whatever?

Edit: Sorry Carlos I know you explained it, I was thinking about an explanation for everything you said.

[Ipso Facto]

Originally Posted by carlos_dfc

Yep - If dark matter exists, that is.....
Personally - to me anyway - the whole idea of 'dark matter' smacks of a 'fudge' to cover up a lack of complete understanding - a bit like Einstein's original idea of a 'cosmological constant' (but that's another story)

But isn't science always a bit of a fudge until further discoveries are made to plug the gaps?

[Mumby]

Originally Posted by hsl

I wasn't doubting that we know, just HOW we know??? I don't suppose anyone could answer that here though, it would take too long probably.

The life of a star doesn't seem like something anyone on this planet could work out to me. I have never studied or even really thought about this kind of thing though, but it fascinates me.

It's not difficult to imagine nothing imo - the big bang must have happened in the same nothingness that our universe is expanding into. All the dust, stars, planets and black holes are hanging in the same thing. Our universe is expanding into the same nothing that it was created in (if it was.)

Why wouldn't there be other universes expanding somewhere else in the nothingness of space, from there own big bang or whatever?

Edit: Sorry Carlos I know you explained it, I was thinking about an explanation for everything you said.

I think I might wade in here if I may...
It's important to realise that the universe is not expanding 'into' anything. The entire universe is within this boundary. A cosmologist might tell you that there is no point asking any questions about what is 'beyond' the expanding boundary of the universe, because, by definition, we could never observe that region. That is not a very satisfactory answer though, I must admit. I know that is a really hard thing to understand, I for one find it virtually impossible to imagine an expanding universe without also imagining some kind of black void for it to expand into. But I have realised that my 'minds eye' is of no use in understanding many aspects of physics. My minds eye is completely biased by the every day world that I see around me, so this tends to prejudice my imagination when I try to think about things that are working on a completely different range scale to my everyday life.

Regards,

Paul

[hsl]

The total darkness everything in the universe is expanding into is nothing, but it is still there. The nothingness isn't expanding as well is it? The total darkness is not our universe, just what the universe is a part of.

Now I think about it, why the heck do planets spin and do stars spin? LOL never mind I'll look it up myself :P

[Cidermaker]

Mumby is right in that the Universe is not expanding into anything, but it doesn't have a boundary.

The way to think about this is in the two-dimensional analogue of the surface of a sphere (the Earth, or a balloon). If you are a two-D person, you have a finite universe (the surface of the sphere), but it has no boundaries. The surface can expand, but not into anything, at least as far as you are concerned. Moreover, the properties of your universe (the surface of a sphere) are completely knowable without worrying about the third dimension (in our simple analogue), and since you have no way of interacting with it, it has no existence as far as you can ever know.

Now try to apply the properties of the sphere analogue to a 3D case, these properties being: the observed recession of all objects; the finite but increasing size of the universe; and the lack of boundaries. Don't think about "what it is expanding into" - it isn't.

Admittedly, there are models of the Universe (and these seem most likely given current evidence) in which the Universe is not finite, like the sphere, but infinite, like a flat surface.

[Cidermaker]

Stars and planets (and galaxies) spin because they form from large clouds of matter that collapse. These clouds of matter are made up of blobs (a technical term) that have more-or-less random motions. The net spin (angular momentum) of these will not be zero. That is to say, the net rotation of the cloud will not be zero. As the cloud collapses to form a more compact object, the spin (angular momentum) is conserved, which means it has to spin faster as it gets smaller. This is just like an ice-skater who spins faster when he brings his arms down to his side.

[Ipso Facto]

Just a thought having listened to an article on the radio on the way home of plans for a new telescope to analyse x-rays from distant galaxies - what is the difference between the concept of dark matter (which many question) and that of black holes (which seem to be universally accepted).

[Mumby]

Well, don't let the words 'dark' and 'black' trick you into thinking that these two ideas have much in common. We have a fairly good idea of how black holes form: massive stars collapse under their own gravity when the nuclear processes that power them come to and end. Stars are made from the elements that we are familiar with and see in the periodic table for example. Dark matter on the other hand is thought to be made up of types of particle that we are not familiar with and have all sorts of odd names, such as WIMPS. The exact nature of these particles is speculative to say the least!

Disclaimer: I'm definitely not a cosmologist

Paul

[Cidermaker]

Black holes are predicted by Einstein's General Theory of Relativity, or rather we should say the theory says that such things can exist. This is far from evidence of their existence, though: the theory may be wrong; and/or the Universe may just not be "right" to make them.

Observational evidence for the existence of black holes is relatively recent, the last twenty years or so. Even then, it is indirect, since (almost) nothing can escape from them, so there's nothing to see. What we can see is matter orbiting them, and/or falling in and getting very hot, and thus radiating a lot. From both of these you can calculate a mass of the object as well as its radius. The next step is to say "Because I know there is this much mass within this radius, and because my well-tested theory of gravity says that that much mass in that radius will be a black hole, I think there is a black hole there." I think this is the basis for most of the evidence. There may be more subtle tests based on the gravitational effects of the black hole on nearby objects (such as time dilation and so on), but I don't know if they've been used observational.

Theories of stellar evolution, which are extremely successful in describing the properties of stars such as our Sun and many others, and which are based on well understood laboratory physics, predict that some stars (big ones) will form black holes when their nuclear fuel runs out.

Dark matter is indeed a different thing. There are lots of candidates for dark matter: black cats (OK, not a serious one, but black cats are indeed dark - you don't have to be an exotic particle to be dark); dust; planets; failed stars (Brown dwarfs); and lots of weird and wacky particles. The key feature of these weird and wacky particles is the only thing we know about them is what they would have to be like to fit the theories and observation, so in that sense, it is a bit of a fudge (as someone said earlier).

There is some fairly straight-forward evidence for dark matter of some type or other, at least in certain quantities. If you look at a galaxy, you will see that it is rotating (you can tell by the Doppler shift of the the light from its extremeties), and you can measure how fast it is rotating. You can also count all the stars in it, and estimate their gravitational pull, and you find that the bright, visible stars won't have enough gravity to stop the galaxy flying apart. Since we believe our theory of gravity works very generally, we conclude that there must be a lot of matter in there that we can't see, i.e. it is dark. One explanation is that there may be a big black hole in the middle.

The reason people are interested in wacky dark matter in cosmology is that all the visible matter in the universe that we can see is nowhere near enough to explain the observed rates of expansion in the universe. This is where I think it gets more fudgy, and also where my (dated) knowledge starts to run out. The amount of matter in the universe and its type (dark, normal, etc.) should have a noticeable effect on how galaxies are distributed, and so by observing these large-scale structures, we can determine what sorts of matter we need to put into our theories and models to make them work.

I think I should stop there. Sorry if I've bored anyone.

[Greenish]

Nobody knows... it may go on forever, or it may go on as far as the last star you see at night!
As you said, it is a very confusing subject!
Bethany

[merlinspeed]

There will always be "more questions than answers"

[Adam Cheeseman]

Have you noticed how much of the universe is made from chocolate. All those Galaxies, then you have Mars, Milky Way, the Crunch. What an interesting Topic.

Cheers,

Adam

[hsl]

and it's good to know I can still get electrical goods in space as well, thanks to the Comets

[Poirot]

If space is 4 dimentions and is spherical, does that mean that if you were traveling at the speed of light (obviously impossable(unless you start talking about warp bubbles, wormholes e.t.c)) from earth going at a constant velocity, would you in Billions quadrillions etc of years arrive back at earth like you would if you started at one county and flew around the world, (assuming you would never run out of fuel).

Poirot

[wyevilla]

Given all your assumptions, then Yes as long as you don't collide with anything along the way and Earth is still about by the time you get back.

There is one other problem though. During all that time, your starting point will have moved relative to everything else so you probably wouldn't be able to find where you started from. A pity.

[Poirot]

Originally Posted by wyevilla

Given all your assumptions, then Yes as long as you don't collide with anything along the way and Earth is still about by the time you get back.

There is one other problem though. During all that time, your starting point will have moved relative to everything else so you probably wouldn't be able to find where you started from. A pity.

Hmm the never ending problems of being 3 dimentional beings in a 4 dimentional space.Sigh

Ahh well maybe someday the acubierre warp drive will become a reality (i doubt it) but optimistic as always

Poirot

[wildherbalian85]

Originally Posted by Birchy

hi there, its my first new thread and my first post on the astonomy forum. Normally I'm browsing the bird forum.

Am interested in space, planets, ufo's etc. But don't really have a brillant knowledge of this subject. I just wondered, even though nobody actually knows, if space just goes on forever?
I know that space is MASSIVE!!!!!! But how can something go on and on and on without there been an end. When I think about it, I just end up getting head ache becuase I don't get it.

If there's any experts out there, if you don't know the answer, could you make suggestions at to how space might possibly end.

I probably reckon that this subject has been discussed before but I haven't been a member of the forum for that long.

Well i guess there are 3 kinds of answers to three kinds of people.

Those who believe in a God.

Those who think or are trying to explain it.

Those who just except its currently beyond the stretch or comprehension of the human mind.

[faroutman]

Don't think about "what it is expanding into" - it isn't.

Cidermaker, how do you know this?

If I think of myself as 2d on Earth, I go around and around, never finding an end, but that's because I can't comprehend jumping. It would never occur to me to move out. There is no 'out' to me.

Must be the same thing in the universe.

If space is expanding, there must be something beyond space, or the space does not exist, we just can't comprehend how to get there.

I just watched a show where two deaf people got surgery so they would be able to hear for the first time in their lives. When asked to describe what they heard, they said, 'it's like trying to describe the color green'.

Their brains could not comprehend what was going on. Hopefully we will be able to comprehend everything one day.

No one has brought up expanding consciousness as a way of seeing the universe for what it really is. Does that fall under science or metaphysical? Do out of body experiences really occur, and could that answer any questions? Maybe when we die it becomes clear? Travel at the speed of thought? Can we accomplish this here and now?

As far as religion, I don't think of it as anything more than fiction. It is man made, just like time. But is there something beyond this life? Is death really death? I think these questions are just as important. I don't know when I get more frustrated, thinking about how big the universe is, or thinking of nothingness. Imagine being dead and there's nothing. You don't exist. Well, I guess if there's nothing it'll be like before I existed. But why do I feel like I've always existed? If there was a big bang, was I born then?

My mind wants to say there's no such thing as life after death, and ghosts, and weird stuff that I can't explain, but then you hear crazy stories, and see scientific studies that make it pretty clear that there is something that goes on beyond this body, and obviously you travel a lot differently without a body, so that may be the key to reaching far away galaxies...

And yes, I have been drinking.