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# Time Machine - Page 7

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In our own Universe, we can see a long, long way. We can't see to the edge, because light hasn't had time to come to us from more than about 15 billion light years out. But, we can see more or less a sphere with a radius of 15 billion light years

Then how do we know where the "edge" of the universe is?
Is it because we know when the "Big Bang" occurred and so the "edge" of the universe is as far away as light can travel from that point in time"?
How do we know how long ago it was that the Big Bang occurred?

If there's an edge, what's beyond the edge?

What happened before the Big Bang?

If the universe is expanding how far can it expand? What is it displacing as it expands?

Why did the chicken cross the road?

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Space is curved just as the earth is. Travel far enough along the curve and you end up back where you started. There is what there is. There is no need to distinguish between where space begins and ends because it is based on a misundertanding of the nature of space.
Okay help me to understand this.
Dean said we can almost see to the "edge" of the universe. He said we can see out to a radius of 15 billion light years from where we are.

Isn't an edge a boundary between something and something else. Does that definition not apply here? Whether it's curved or what not, doesn't "edge" imply that there is this thing we're calling a universe and something else is outside of it?

Also when we say the universe started with the "Big Bang" and then began to expand outward from that, are we talking about the matter which was propelled outward or is the expanding universe both the matter and the space it occupies? If the latter then what did the expanding universe displace?
Look in a mirror. You're seeing to the "edge" and back. If we could look far enough in space we could do the same thing.
If you looked like me would you want to look in a mirror?

I don't get it. If I look in a mirror I'm "seeing to the edge and back" and that's the same as the universe?
If I look in a mirror I simply see light reflected back to my eyes.
I don't understand how that gives me a way to understand 1. a universe that is "curved" and 2. the universe having an "edge" but there is nothing beyond the edge?
When I said 'the edge' I was being a little careless. As mentioned there might not be an edge. I really meant 'back to the point of the big bang, which isn't an edge really, its a point in time.

It is possible that our space is a closed 3D space, which is impossible for us to imagine, so its easier to do it with 2D, as is commonly done in books on the subject. If you lived in 'flatland' a 2D world. You would only know about 2 dimensions, and only crazy people on internet forums would talk about 3D worlds. However, your flat world could basically just be the surface of a 3D sphere. You couldn't know that, because it wouldn't be apparent to you at all as long as the sphere was very large (as we know that our space is.)

Light would travel along in your 2D world, and would appear to go straight to you, though it would actually curve along the surface of this 3D sphere. There would really be no experiment that you could do to prove or disprove this theory, because there would be no way for you to measure the curvature of your own world. A 2D world's laser beam would travel along this surface, so though you would seem to be 'out of line of site' to a 3D person looking in from the outside, the light would bend right around along the surface of that sphere.

It is thought that our space is like that, but we are on the surface of a 4D sphere, which unfortunately, our little minds cannot picture, just like the little minds of the 2D people cannot picture a 3D sphere, or a sphere at all since they are at least 3D by definition. So its possible that there is no edge at all, and that if you go far enough, you get back to where you started. Unfortunately, going far enough means at least more than 15 billion light years. And, if many of the 'inflationary' theories are correct, our 15 billion light year radius sphere might be as small relative to the actual space in our universe as the earth is to that 15 billion light year radius area we can see, i.e. it may be immense beyond all comprehension.
We've verified that matter, energy, time, gravity etc. works the same way throughout this little space. And that little space in comparison to the size of the "universe" could be as small as a grain of sand compared to a sphere with a 15 billion light year across radius (or even incomprehensibly smaller).

And because of that we have ruled out any other fundamentally different things occuring outside of that grain of sand sized space? Is that correct?

When we say it started with a big bang and then began to expand are we referring to matter expanding or matter and space?
I now realize that last one was a silly question. The expanding universe must mean not only matter but space too. Because if we weren't talking about space too then it wouldn't be a universe expanding would it. It would just be some lousy matter expanding within a universe. So don't humiliate me by answering that one.

So now on to the next question. If the universe is "expanding" then what is it displacing when it expands?
I'm starting to get some inkling here that maybe I'm asking that last question only because I'm trying to understand it all in 3D. But time (the 4th dimension) throws in a monkey wrench that makes my question stupid? Only because I cannot visualize the whole thing in 4D. Is that correct?
Bob,

It is frustrating when our brains try to understand things by analogy to the tangible (e.g. expanding bubbles = shape of universe in 4D). The analogies always have limits, like you point out, there is nothing to displace. I personally think coming toward better understanding of our world and universe requires climbing a ladder of abstractions. You have to convince yourself of each along the way, and then move on to the next.

Anyway, I don't know a lot about cosmology or astronomy so won't comment more on this line of questioning. But I found proof that Freud was absolutely right about men and the size of their tools.

http://news.bbc.co.uk/1/hi/sci/tech/2116605.stm

M
When we talk about our space being a surface on a 4D space, in that case, time isn't that 4th dimension, but literally a 4th (or higher for that matter.) geometrical dimension. When talking about space/time, then time is considered a 4th dimension. It can get confusing sometimes because, to a scientist, any measurable 'axis' of the problem can be called a 'dimension', because they are using it in the generic sense, whereas we use the word so often to talk about the physical dimensions of our world that we tend to think of any discussed dimension as a physical one, when it may or may not be.

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And because of that we have ruled out any other fundamentally different things occuring outside of that grain of sand sized space? Is that correct?

Nothing is ruled out really. Its just a matter of probabilties. If you look at it from that stand point, you come up with things like:

- Given that physics is the same as far out as we can see, how likely is it that it changes just beyond where we can see? Its a low probabiliti.

- If physics is the same in our universe, but there are many others, other than as a huge philosophical issue, the probability that this will be of much use to us is low, because we are stuck with the physcs of the universe we live in. If you are stuck in one room with no food, the fact that there is a feast going on in a room nearby that you cannot get to is just a philosophical matter.

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So now on to the next question. If the universe is "expanding" then what is it displacing when it expands?

The universe is not expanded into 'space'. Space is expanding with the universe. We cannot really say what its expanding into. In the larger (literally) scheme of things, our inconceivably large universe might be so small as to be unobservable from the scale of whatever that larger space is.

But getting into these types of arguments is a waste of time, unless you have a bag of good pot around :-) Its an infinitely regressive problem, since what did that 'outer' space expand into, and so on and so on. Basically, the best way to look at it is that you and I don't exist. This is all just a complex halluciation in the mind of a small frog, sitting at the bottom of a deep pool of infinite size, watched over by a dwarf.
I see Dean had found the bag, and isn't sharing.

Gus
Quote:

When we talk about our space being a surface on a 4D space, in that case, time isn't that 4th dimension, but literally a 4th (or higher for that matter.) geometrical dimension. When talking about space/time, then time is considered a 4th dimension. It can get confusing sometimes because, to a scientist, any measurable 'axis' of the problem can be called a 'dimension', because they are using it in the generic sense, whereas we use the word so often to talk about the physical dimensions of our world that we tend to think of any discussed dimension as a physical one, when it may or may not be.

Lord have mercy on my soul, that is so heavy that I can't even begin to even try to even get an inkling. I think I'm gonna have to go with the frog and the dwarf.
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If you are stuck in one room with no food, the fact that there is a feast going on in a room nearby that you cannot get to is just a philosophical matter.

It is unless you choose to try and make a hole in the wall and get to the food on the other side.
After reading the replies above I'm not sure if I understand which of these two statements is the most accurate...

1. the universe did not expand into anything

2. the universe did expand into and (may or may not) have displaced some "thing" but we don't know what that thing is.

If the answer is the latter then that thing, whatever it is, used to occupy the same location we're in right now. Maybe it occupies the same location still.
In the future we might discover a way to access that other thing (after all it might be right under our noses). Maybe we would find an entirely new set of fundamentals at work in the "other thing".
That would also be an example of breaking through the wall and pigging out on the food in the next room.

I rest my case, your honor.

p.s. maybe when we learn how to move around in the "other thing" that will put you time travellers back in business too. Who's to say.
Of course, if you poke a hole in the wall and the other room is composed of anti-matter, both rooms will instantly tranform into energy and destroy everything :-) That would always be a philsophical problem with having any sort of physical connection between two areas with significantly different physics. What happens where they touch?

The whole matter/energy thing (e=mc^2) is pretty interesting. The amount of energy in a tiny bit of matter is immense. Matter is to energy what crack is to cocaine, except infinitely more. Its super-condensed matter. When you get energy by burning stuff (wood, chemicals, hydrocarbons), we only convert a tiny fraction of a single percent of the mass to energy. Even a hydrogen explosion (nuclear fussion), the most powerful conversion process we can create, is still less than a percent if I'm remembering my numbers correctly. And even with converting less than a percent of small amount of matter (I assume its still duterium, but I got kicked out of the secret nuclear weapons club) it makes a huge boom.

Matter/anti-matter anhilation is one way (the only way we know of?) to achieve complete conversion of matter to energy, but their ain't much anti-matter around to play with. It is believed that an equal amount of it was created in the big bang as regular matter, but a slight asymmetry in the process created a little more matter. What we see around us today is that little bit that was left over, a very small percentage of what was originally created, most of which 'went up in smoke' very quickly in matter/anti-matter destruction.
Hot damn, it just occurred to me. Maybe those "saucers' so many of us are seeing are moving between our thing and "the other thing".
In the simplest of terms what was the big bang?
Is the currently accepted theory that the universe expanded out so far that it then did an about face and started to contract? And when it contracted back down to the size of a pea it blew up and started expanding again?

Also what is the evidence for the existence of "anti-matter" (and is there a way to explain it so that the guy pictured to the left can understand)?
Bob,

AFAIK the big bang is simply the best theory that fits the facts. The facts are that everything on a super-galactic scale appears to be rushing away from everything else. So we say our universe is expanding. By looking at how fast things appear to be accelerating, or not, we can try to guess whether the universe will stop and re-contract. I read something recently that one group is saying that the universe appears to be very balanced, so that it will keep slowing down and just barely come to a standstill like 15 trillion years from now, when all of the energy is pretty much gone and chemical reactions can't even happen. Why would that be? It's almost like it was made that way. Spooky.

So I didn't really answer your question. I guess it was a huge explosion from a super-condensed state, where matter and energy condensed out. Where did it come from? Will we ever know? Maybe it just happened. Maybe it popped in from another dimension. Will it keep cycling, or has it done that 'forever'? It's hard to imagine that these are all even knowable.

Antimatter I understand a little better. It was predicted in the 20s I think based on a sign uncertainty in a physics relation on particle properties. Basically no one could think of a reason for particles like electrons (normally negative charge) to exist but not positrons (exactly like electrons but with + charge). So they went looking for them in nuclear reactions, and sure enough they came out. The evidence came from looking at particle tracks. Particle physicists can get a lot of info from the swirls particles make when they are created in a high-speed collision. Mass, energy, and charge are all pretty easy to come up with. Charge is real easy since you see which direction the swirls go. So they saw tracks that were identical to the electrons but going the wrong way.

Many more bits of evidence have piled up. Certain radioactive nuclei emit positrons. They are so easy to detect and interact with matter in unique ways that they are a great probe. People get "PET" scans of their brains - Positron Emission Tomography, by being injected with a solution containing these radioisotopes. You can see a particular energy spike when positrons hit matter, and it's energy fits perfectly with the E=mc^2 relation, when m=mass of electron+mass of positron. Pretty cool.

It's pretty hard to get bigger pieces of antimatter, though. I know some antiprotons have been made, and anti-atoms, I think. But just a few, not even a tiny little drop or crystal.

M
Thanks, Moore. As I'm sure I don't have to tell you by now my understanding of some of these things can be compared to yours and Dean's in this way. It's like the size of a grain of sand compared to a sphere that's 15 billion light years in radius?
But I'm starting to get fascinated so will begin to try to get that grain of sand up to at least Earth size.

One thing that keeps throwing me for a loop though. It all started with this super condensed thing that went bang. And now it's expanded to an incomprehensibly larger size. But what did it expand into? Where it expanded, what was there before?
If the answer is that the question is not valid because it doesn't take into account a "4th dimension" then I'm having great difficulty with that. The Earth and Solar System and that video projector above my head and you and Dean occupy a 3-dimensional space. Before any of these things existed what was in that space?

Bob
On the super-condensed thing... Something that most people don't realize is that there is very little there there. We are almost completely empty space, even the most dense materials are. Mostly we are electrical fields, not matter (in terms of size I mean, not weight, the weight is all from matter, which in turn is just energy.)

Anyway, the point being that atoms themselves are almost completely empty. The nucleus of an atom, where something like 99.999% of the 'matter' in an atom is, is 100,000 times smaller than the electron shell that surrounds it. And its those electron shells that make up the size of an atom, and where they hook to each other. So an atom is like a grain of sand inside a transparent globe the size of New York. All of the weight is in that grain of sand, and the transparent globe would be unbelieveable thin when blown to that size. In the middle is nothing but electric charges between the positively charged nucleus and the negatively charged electron shell, basically just empty space.

So, right off the bat, if you can strip off the electrons (which isn't terribly hard to do), you can reduce the size of an object by 100,000 times, which is a huge reduction. Neutron stars are one of the most spectacular examples of this. The gravity of the parent star isn't strong enough to create a black hole, but its strong enough to crush the electrons into the nucleus which then bind with the protons and become neutrons.

So, along with the neutrons that were already there, you end up with a ball the size of a small planet, completely composed of neutrons, and now 100,000 times denser ('stuff' per size unit, e.g. per spoonful or whatever) than the original stuff in the star. The gravity is so intense that even though it is the size of a small planet, and usually rotating very fast, if you could survive the gravity, you could reach out and put your fingers on it, because it would be atomically smooth. It won't have a mountain bigger than at atom anywhere on the surface.

The reason that such neutron stars don't collapse is something called 'degeneracy pressure', which is caused by the constant motion of all atomic particles if they are above absolute zero (and they would be very much above absolute zero in a neutron star because of the pressure induced heat.) They always are zooming around like crazy, and will fight like mad from being pushed together and stopped from zinging around.

But, with sufficient force (like that of a very large collapsing star) you can overcome that degeneracy pressure and crush the matter even further. The neutrons and protons (nucleons) in the necleus are themselves made up of quarks, which are held together by the strong nuclear force (represented by force carrying particles called gluons), and are again mostly empty space. And they themselves are in the end just pure energy.

A black hole has sufficient gravity to crush the matter all the way down to its constituent energy (more or less, if any physics majors are reading, don't sue me, we aren't doing this for money), and hence it can reduce all of the mass of that parent star that didn't get blown off in the super nova that caused the black hole (and that's still a LOT of matter), down to effectively a dimensionless point, i.e. not of this 3D universe in any way that we picture such things. The 'black hole' itself is not this 'singularity' (as its called), but just the point at which light cannot escape. Its not a physical boundary, just a point of no return. No one knows what the singularity would 'look like', assuming that term has any meaning at all and it probably doesn't in this case. Time and space are both infinitely warped in such areas, so it would be a place wierder than anything we've ever thought of.

Anyway, the point of that whole ramble is that its not so wierd to think of all of whats out there now as having come from effectively a dimensionless point. Of course, it *is* wierd, but not wierd in the sense that, despite what most people think, matter can be squished down almost infinitely, because matter is nothing but energy.
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But I'm starting to get fascinated so will begin to try to get that grain of sand up to at least Earth size.

Go buy "Coming of Age in the Universe", by Timothy Ferris. I've mentioned it a copule times here, and I can't recommend it enough. For you it would be perfect, because it skims over the entire history of science and the characters who made it happen. So it gives you the big picture, from which you can swoop down into those areas that you find interesting.
Okay, time out for just a moment.

You all should be aware that a thread is running on the audio forum which has over ten thousand hits and over 400 posts. It started as a discussion of whether ridiculously expensive speaker wires provide improvement worth the money. And then meandered around the whole question of elaborate audio tweaks. QQQ posted this today...

http://www.avsforum.com/avs-vb/showt...38#post1298938
That's all basically mumbo jumbo. I'll bet anyone \$1000 that they could not reliably pick out any of those tweaks in a double blind test on any system that they want to use. And in fact, I really don't have to, because well respected folks have already run such tests and proven that its all just silliness.
You should go in there and tell em that, Dean. Somebody needs to pound some sense into them.
I've been there and done that. Its a thankless job that just increases my stress level, without any benefit to me and without doing much to enlighten them.
From Scientific American How to Build a Time Machine
I wouldn't buy tickets yet 8-) Now, back during the dot com boom, you could have opened up timetravel.com, went public, and cashed out a millionaire before anyone bothered to read that version 1.0 wouldn't come out for ten thousand years.
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Originally posted by RobertWood
You should go in there and tell em that, Dean. Somebody needs to pound some sense into them.

Bob,

I tried too. That thread depresses me. Compared to seeing the edges of the universe or proving antimatter's existence, evaluating cables is child's play if not easier. But a lot of otherwise educated people would rather just bury their heads in the sand. If you visit some quack audio shops you will see some of the things pictured in QQQ's post. There's one near where I live. What's laughable is that they worry about any change to the sound with cables touching the floor, but then the speakers are audibly resonating with the loose floorboards, in an unpleasant way! I'm by no means an audiophile, by the way, I just like to see these things first hand before I judge.

I actually bought a book because of that thread. "Why people beleive weird things". I just started reading it, looks good. Hopefully it will restore some of my hope in humanity.

M
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