Does Space really go on forever?

[naturelover]

You boys are blowing my mind with all this space talk,i just know its there and thats it,to understand is another thing,i know what you are saying about every thing has an end,so if space goes on for ever with no end what is for ever.?
My youngest son and i sometimes get onto this discution,for hours you can talk about it but you never seem to come up with an answer,its just one of those mysteries of life.

[naturelover]

hi whatsthat you must be new to the site welcome,i too understood marineboy he exsplained it in english,i can understand that,have fun on the site.

[Marineboy]

Hi and thankyou, watsthat and naturelover, I am glad that my thoughts landed on some fertile minds!

We can not go on believing that this wonderful planet of ours is as unique as many would have us believe.
But, this is the only one we have. The only one we know about.
Man has changed the face of this planet ever since he was able to rub two sticks together to make fire. Since those earliest times of man's rise of intelligence, knowledge and understanding, man with his immense positive impact, has in reality had a very negative impact on this planet.
Our planet is under threat from time, space and us.
Far off in the distant future our sun, the sun that gives life to this planet, will die. That unfortunately is a certainty. Not for us to be concerned about - we will be long gone. Man, if we are still in existance will have moved on to the stars.
Maybe, just maybe, another threat as big as mans impact on this planet will come into sight. Far off in distant space and time, there will be a large chunk of rock heading towards this planet. A meterorite has smashed into earth before and changed the direction of life on Earth. It may be sufficient to change the direction of life on Earth again.

Events such as this, we can do nothing about, but we can do something about our own abuse of this world. I hope that man's many global voices will one day allow us to come together with a single hand towards putting right what we have done to our beautiful blue-green planet.
In the whole concept of space, our universe is merely a pinpoint in the darkness. Our Earth is just a pinpoint within that. But, wow, isn't it wonderful!

[hsl]

About people not saying whether they are religious or not, let me say I'm definitely NOT religious. Although there are many people who are true to what their religion probably started out as and was meant to be, all religion's and especially Islam have been followed and covered (ruined?) in a very bad way by some which, rightly, won't ever be forgotten.

[zan]

I'm curious as to what's (who's?) in the other 8 dimensions we can't see yet

[zan]

PS This thread is awesome!! Totally made my day - it's been a long time since I've really thought about this stuff

[Birchy]

I've just had a thought. If the Universe is ever expanding and travelling at the speed of light or even quicker then how would you ever catch it up. It's totally impossible, you could simply never get to the end to see whats there. But if you could never catch up with the expansion then you might as well say that it infinate.

We will never find the answer but scientists will keep on making up theories I supose. We will never know the truth. Oh well it's been an interesting and fascinating thread so far. May it Continue!

[VitaEstBrevis]

That's a good question. There are two "edges" to the universe, the visible edge (that is the farthest distance it would be possible to see with the largest possible telescope) which for all intent and purpose is the only one that actually matters, and the theoretical "edge" which should be simply calculated by multiplying the age of the universe (in years) by the speed of light to obtain an answer in light-years.

The problem is Hubble's Constant which links the amount of red-shift to the distance of the object to be measured. Although there is a general consensus, there is still some disputation about the exact value of Hubble's Constant.

However, if you have built a faster than light space ship and were planning a trip, please bear in mind what was said in a previous post about the universe being curved in three dimensions around a hyper-sphere.


As for the rate at which the universe is expanding, well the theoretical edge of the universe is as always travelling at the speed of light, and all the material is travelling at somewhat less than the speed of light. Some people think that the universe will ultimately stop expanding and start contracting, Such belief is based on the Solid-State theory first postulated by Sir Fred Hoyle. This theory would predict that the rate at which the distant galaxies are accelerating would be growing smaller, as the weak but inexorable pull of gravity would pull the universe back together. Interestingly, the dscovery has been made that the Universe's rate of expansion is not slowing down but speeding up. This has led physisists to have to wrestle with the concept of dark energy.

When I start thinking about the nature of the universe, I find a couple of paracetamol helps.

Best wishes and good luck with the headache.

[VitaEstBrevis]

Originally Posted by ChristinaMarieUK

Adam,

What kind of proof would you accept?

I fail to see what this has to do with the size of the universe, but since the question has been raised, it should probably be addressed. I think anyone trying to prove or find proof in the existence of God is in for a long and intellectually frustrating journey. I should know, I spent 20 years trying to prove to people that God existed.

From a philosophical perspective, there are only four types of statement which can be evaluated:

1. Analytical
2. Empirical
3. Value Judgements
4. Metaphysical.

Each statement can either be TRUE or FALSE.

Analytical statements are defined. They are true by definition and rely on a universal acceptance of predifined terms. Analytical statements are usually confined to the field of mathematics. Hence 2+2=4 is true because of the definition of 2; +; = and 4. Mathematical statements can be proved by applying pre-defined and universally accepted rules to pre-defined and universally accepted terms. Analytical statements are the ONLY statements that can be proven. Unless you are a mathematician you really shouldn't look for or expect a "proof" unless you want to spend the rest of your life searching for something that doesn't exist.

Empirical Statements: Empirical statements are also either True or False, their truth or falsehood is measured empirically. The statement Pi = 3.14 to two decimal places is measured (not caluclated or else it would be an analytical statement) by dividing the measured circumference of a circle by the measured diameter. The statement, "I am six feet tall" would be evaluated by measuring my height with a ruler. With empirical statements, we can evaluate the accuracy using measurement and observation. The problem with evidence is that it proves nothing. Physisists for example begin with a hypothesis which they then attempt to disprove using evidence (evidence is a wrecking ball used to destroy theories, not bricks used for building arguments.) If the evidence fails to disprove the theory after very many attempts over many many years, eventually the theory becomes a law. No matter how well established a law might be or however renouned the originator of that law might be, the law can be disproved by anyone with only one piece of evidence that contradicts the theory. For exaple, if I drop an apple which suddenly falls upwards towards the ceiling, and this experiment can be repeated, bang goes Newton's laws of motion. It is IMPOSSIBLE to prove an empirical statement. It is, however, possible to DISPROVE an empirical statement.

Value Judgements:

Value Judgments are true or false from an individual's point of view. For example, one person may consider a work of art to be offensive and unsightly, another may find it inspired and/or aesthetically pleasing. In the case of value judgments, it is necessary for completeness to state the source of the value judgment although in common speech this is usually understood without the need for explicit citation. Issues of good and evil are matters of value judgments. For those who practice a religion, the value judgmnets of the principle deity of that religion are the value judgments commonly adopted by that community, nevertheless, no matter how many people believe a value judgement to be true it is still a value judgment. In Britain, the value judgments of the Queen and Parliament are law and must be adopted by every member of our society to avoid punishment but no matter how important or how well accepted a value judgmnet is, it is still a value judgment and does not necessarily have to be shared by everyone. Since it is possible for one person to love something that another person hates, love and hate are also value judgments along with the entire spectrum of human emotion.

Metaphysical.

Metaphysical statements are statements which involve a reference to a being that is outside our own experience of the laws of nature, or outside of our ability to detect or measure such entities. In practice, this tends to be a "catch-all" for any statement that is not covered by the above three. Therefore religious pantheons; deities; including the Judeo-Christian God fall under the title metaphysical, along with the tooth-fairy and fire breathing dragons. Like all of the above statements, metaphysical statements can be true of false. Just becasue God is mataphysical does not make him any more or less real it just makes him immeasurable. It is not possible to detect God directly or indirectly. Individuals may have "experienced" God but their experiences would be considered value judgments. The truth or falsehood of metaphysical statements can only be evalueated by revelation which results in either belief or disbelief.

It is an error to test the truth or falsehood of one category of statement with the conditions required for another. No one would try to evaluate my height using only the laws of mathematics and pure logic without reference to an actual measurement. Similarly it would be an error to say that 2+2 = 3, 4 or 5 depending on whose opinion you want to listen to.

I do hope this post can help us to avoid turning a question about the size of the universe into a forum for christian apologetics.

Best wishes to all and a very happy new year.

[Cidermaker]

I think VitaEstBrevis' post (the one before last, talking about cosmology) is a bit wide of the mark.

The talk of edges is misleading. Granted, we cannot see the whole of the Universe, but we can make local observations, and propose models based on these. None of these models includes an edge in the sense of a boundary, beyond which there is something that is not the Universe. Some of these models say that space is curved back on itself, analagously to the way the surface of a sphere (e.g. the Earth) is curved, and some of them say it goes on forever, like a plane.

What VEB is talking about is usually called a horizon of one sort or another, since it is the limit of what an observer can observe, but of course, another observer situated on the first observer's horizon will see something pretty similar to what the first observer sees: no edges, just horizons. Again, the analogy with the surface of the Earth is a good one.

This brings me on to the founding principal of (scientific) cosmology: that the Universe is homogeneous (i.e. there are no special places), and that the Universe is isotropic (i.e. there are no special directions). This is often called a statement of cosmic humility: we do not occupy a special place in the Universe. This principal is borne out by observations on large scales (much bigger than galaxies).

The other foundation of cosmology is the observation that distant objects are receding from us at a speed that increases with distance. We should be careful: the observation is that light from distant objects is red-shifted, and while the standard interpretation is that this is caused by recession, there are some theories that explain it differently (e.g. "tired light" theories). The appeal of the standard approach is that it uses laws of physics that can be observed directly here on Earth.

In the decades following the discovery of the red-shift (by Hubble, in the 1920s, I think), there were two competing models: The Big Bang; and the Steady-state model of Hoyle et al.

The Big Bang model very naturally incorporates the recession of distant objects, but hand-in-hand with that is the view that if the Universe is expanding now, at sometime in the past, it must've been a lot (infinitely) smaller. The Steady-state model tries to avoid this "beginning" of the Universe by saying the Universe is infinitely old, and that although it is expanding, matter is being spontaneously created to fill up the gaps, as it were.

The Big Bang model "won" with the discovery of the cosmic microwave background radiation: the Universe was filled with very hot radiation shortly after the Big Bang, which has now cooled to 2.7K. While this is a natural prediction of the BB model, the Steady-state model struggles to explain this observation.

The question then remains: will the Universe continue to expand indefinitely, or will gravity slow down the expansion, turn it around, and return the Universe to a Big Crunch? In the late 1990s, observations of distant supernovae (exploding stars, very bright) showed that the expansion is accelerating, which frankly, came as a bit of a surprise. This then begs the question: why on Earth is it expanding? I don't think anyone really knows (yet).

Kind regards,

Cidermaker.

[Adam Cheeseman]

Originally Posted by zan

I'm curious as to what's (who's?) in the other 8 dimensions we can't see yet

Different but same versions of us asking the same questions?

[Words]

(I'm going to regret posting this... )

Originally Posted by VitaEstBrevis

Metaphysical statements are statements which involve a reference to a being that is outside our own experience of the laws of nature, or outside of our ability to detect or measure such entities.

That's not strictly so. Metaphysical statements set out universal principles such that nothing can stand outside those principles. This is often degraded to explain religious notions (or non-physical occurences), but that's not strictly what metaphysics is about.

The physical sciences rely on metaphysical principles just as much as do religious paradigms, the primary one in physical science being that existence equates to measurable matter. This is counter-intuitive, since it disregards the impact of thought and conceptual modeling (pen, mightier than the sword).

A broader metaphysics would step beyond the simple argument of matter/energy and seek to establish the consolidating principles affecting both (with the effect of negating the difference between energy and matter, both of which - metaphysically - are the same; just configured differently within a continuum). So the metaphysical underpinning of the space/time arguments are limited by the presumption that existence is fundamentally material and (time)limited. An alternative, and to my mind better, position is to argue that action (or, better, 'agency') is the primary stuff of existence and that it emerges through self-generated creativity. Thus the physical limitations of time can be disregarded since the continued expansion and existence of the unvierse is essentially an on-going creative principle. The universe is in a state of perpetual re-generation out if itself, and is driven by an experience of expansion, therefore engendering (through self-habituation) further actuality of expansion. In other words, the universe expands because to do other than that would mean to remove from its universal experience some element of that experience. And each experience adds to the totality of experience, hence expansion.

[Ipso Facto]

Originally Posted by Cidermaker

... This brings me on to the founding principal of (scientific) cosmology: that the Universe is homogeneous (i.e. there are no special places) ...

That was quite a posting Cidermaker: are you a professional in the field or something?

However, on the subject of homogeneousness, doesn't Newton's 2nd Law and the fact that the universe is continuing to expand outwards suggest that at some point (the place where the big bang occured?? ... if it did! ) there should be a complete void. How can an outwardly expanding universe maintain homogenaity ... or is that a daft question?

[ogwen]

I cant understand most of what people are saying on here, like all of you though i find it fascinating.
Thinking of far off galaxies, and the vastness of space, whether there is an end to it r not is slightly daunting. Its existed for millions of years and will still be here for millions of more years.

Cool!

[Cidermaker]

Thank you, Ipso Facto.

It isn't a daft question. The easiest thing to think about is an inflating balloon, with milk-bottle tops stuck to it. Wherever you sit on the balloon, you will see everything (the bottle tops) receeding from you, but there are no voids, or centres, or origins, or anything like that - it is homogenous.

[Ipso Facto]

Originally Posted by Cidermaker

... The easiest thing to think about is an inflating balloon, with milk-bottle tops stuck to it. Wherever you sit on the balloon, you will see everything (the bottle tops) receeding from you, but there are no voids, or centres, or origins, or anything like that - it is homogenous.

A fascinating analogy that answers a lot but changes any 3 dimensional concept that any of us may have had of our universe to that of a two dimensional, spheroidal surface. That void that I was looking for becomes the inside of the balloon and the universe becomes the debris being carried forward on the crest of a pressure wave following an explosion ... it seems to make sense ... I think! ... but aren't other galaxies in our universe visible in all directions and not just laterally. Is there any evidence that the universe is wider than it is thick?

I suppose in theory we should be able to look across the diameter of the balloon and see v. distant galaxies on the other side although in practise that must be a bit too far away by now.

I prefer the balloon model for a universe to that of the jam sponges talked about earlier in this thread although I have to say that balloons don't taste as good!

[Cidermaker]

No, the Universe is not a balloon. In whichever direction we look, we see pretty much the same thing: galaxies, and clusters of galaxies, and superclusters of galaxies, all the way out to the limits of our sight. It's best not to think of it as a sphere, though, because when you think of a sphere, you will think of an object with edges.

The balloon (and the sponge) are analogies used to demonstrate parts of the argument. In this case, I was trying to demonstrate how a space, in this case a spherically-curved two-dimensional one, can expand without having a centre of the expansion.

Imagine you were a 2-D person, confined to the surface of the balloon, with no perception of the third dimension at all. You would still see all the milk-bottle tops receeding from you. Interestingly, you could still infer that your space is curved, even though you can't see into the third dimension to get any perspective. What you can see is that the geometry is not the same as the flat one you were taught in schools. The angles inside a triangle add up to 180 degress on a flat space, but not on a curved one. Imagine starting from the North Pole, heading down the Greenwich meridian, turning right at the equator to head due west, then turning right at the meridian of 90 degrees longitude, and from there, straight on up to the North Pole. This triangle is made up of three right-angles, so 270 degrees. Tests like these show how it is possible to know if a space is curved or flat without having to get outside it.

It is conceptually and mathematically possible to have 3- or 4- or more-D spaces that are curved, without having to refer to any space in which they are embedded. The question then is this: given that the world immediately around us (houses, cars, people, rivers, etc.) looks very much like a flat 3-dimensional space, why would you want to start worrying about theories with curved spaces? The answer is that although no-one has been able to measure curvature of space directly, there is one theory (Einstein's General Relativity) that postulates just this in explaining gravity. This theory makes very precise predictions, often quite different ones to theories based on flat spaces (e.g. Newton's theory of gravity), and in each and every experiment, GR has come up trumps. The most straight-forward of these tests is the precision of the orbit of Mercury. In Newton's theory, the point in its orbit at which Mercury is closest to the Sun doesn't move, but in GR and reality, it does.

In General Relativity, we live in a four dimensional space, which is curved by the presence of gravitating objects (i.e. all objects, but some objects gravitate more than others!). There is no need for there to be higher dimensions into which this space curves: to say it curves is just to say its geometry is different from the flat geometry you learn in schools. The hard bit (I think) with this idea is understanding what the fourth dimension is, but this is true of the flat spaces of Special Relativity, and also of Newton's theory, and is another story.

Hope this helps.

P.S. When I re-read this, it occured to me that one thing that may make this hard to understand is what is meant by "space". I think people may understand it as meaning the place where the stars are. Infact, what I mean is the concept of a space, which may have nothing in it, or may have lots of stars, but which has lots of geometric properties such as angles inside a triangle, straight lines, etc. You can imagine spaces with different geometric properties; you can define them mathematically; and then you can build physical theories on them that make predictions that can be compared with reality.

P.P.S. This is hard stuff. I think there are few people in the world who really understand it, and I'm am not one of them.

[Marineboy]

I love catching up with this thread. I too find others' thoughts and theories fascinating. For me theories such as the big bang pose questions like where did everything come from in the first place? And if the universe is expanding, where, and what is it expanding into? And edges, horizons and limits to space just can not conform to what we need to understand.

During these frosty clear nights, if like me, you are lucky enough to be free of light polution, put aside any preconceived ideas and just gaze up at the stars. You can only see a small part of the night sky, but before you, you will see thousands of twinkling stars. And beyond, and behind these will be thousands more. And behind them, thousands more. And it is like that all over the globe. My theory is that, where ever you are on Earth, where ever you gaze at the stars, because space is so timelessly vast, where ever you gaze, somewhere, someTIME, some THING will be gazing right back at you.

[Ipso Facto]

Originally Posted by Cidermaker

... Hope this helps ...

... I hope you were joking! I thought we were at last cruising in 6th and then you went and spoilt it again ...

I think that my problem is that any theory has to make sense to me before I am satisifed (I have the same difficulties with my own religion so don't feel too hard done to!) and I'm not sure that I am getting my head around this one. I am an engineer and I spend most of my time messing about in 3D (or 4 if you count time) and then you go and mention gravity!

Perhaps its the term Big Bang that is a fault. BB suggests 'expolsion' and the word explosion suggests that all of the debris is thrown outwards leaving a hole (look at any of those pictures on the news and you will see where I am coming from). If the universe is expanding outwards how can it not leave a hole? If there is no hole I can only think of two alternatives. 1) there are some stationary objects that stay in the middle (but how is this consistent with the BB?) or 2) something, somewhere, is providing further material for infill ... or, due to curvature (the effects of gravity?) are you suggesting that the universe is expanding whilst providing its own infill???

Sincerest regards ...

p.s. I love your example of the triangle with interior angles of 270 degrees - it is obvious when you read it but I had never come across it before.

[hsl]

Why is the universe expanding as fast as it is? And would the gravity of certain stars and black holes etc cause the universe to expand in different directions? (probably already been answered but I'm struggling to get my head round things).

Awesome posts though guys and gals.

[hsl]

I forgot to ask why the universe doesn't slow down expanding. What keeps it going so fast?

[eeyore]

some theorists say that it is actually slowing down - its just that it was going like really really fast in the first place so the infintesimal slowing isnt easy to see. These theories hold that eventually the universe will stop expanding and start contracting back on itself , and will eventually collapse in the "big crunch" after which there will be another big bang and it will start expanding again.

I wouldnt worry too much about this tho as we are talkining eons here rather than a week next tuesday