Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Edge of the Universe

OK, black holes are tricky, say you were at the centre of the earth and were travelling outwards, you would one day get to outer space and no longer be in or on earth.

Your example has nothing to do with your original premise. You might as well have said that if you lock yourself into the bathroom you need to open the door to get out.

You might want to reread your original post.

in that context, what were you saying? I don't understand your black - hole example.

You indicated in your original post that a finite universe has an edge, a barrier.

My point was that the volume inside of a black hold is also finite ... but there is no edge or barrier.

That which is outside is outside ... but you can go in one direction forever and never do other than loop back upon yourself.

There is no reason to believe the universe, as a whole, should be any different.

I'm sorry if this was covered(6 pages is a bit beyond my attention span atm) but when people are asking about "what was there before there was everything?" I ask you this. Is it possible that all things always were, and the idea of non-existence came about by our quest of curiosity to explore the unknown? In the the universe all things happen as they should happen, unlike human behavior or a crappy program. So the notion of something being wrong, or incorrect also would not occur in the universe. It wouldn't be too large of a leap to transition over to the idea that non-existence only exists in our minds, because when we eat food it is no longer there to be eaten. Although to a universal logic, the food still exists within your body, not caring for what purpose it had once served, continually existing as it had before. The idea of change is something the universe does not understand.

yeah, you've literally died before. your infant you is blowing in the wind. i've said this before but you may not come across it. so, sorry to those that have.

DA, could you do a diagram or something. By your statement on looping I assume you are talking about walking (impossible, I know) on the surface in an apparent straight line till you reach your original point like Christopher Columbus. Or did you mean that you could send a rocket off into space but the immense gravity would draw you back in, in some kind of loop?

Pick up a copy of one of Briane Greene's books such as "The Elegant Universe" and read it: No math required.

If you are anywhere in a black hole, or perhaps our universe, and you travel at any speed you wish in a straight line, you will never encounter a barrier or edge.

One can travel an infinite distance in a finite space.

well duh. But you will (if you are travelling faster than light) escape the black hole and drift away for ever into nothingness. (assuming the black hole is the only thing in the universe)
That's what I was thinking of when I was talking about an edge.

Rob wrote:
"you will (if you are travelling faster than light) escape the black hole"

And if you are an invisible purple rhinoceros you can redefine pi as 3.0 and it will work.

"and you travel at any speed you wish in a straight line"

"(x-1)/[(x-2)(x-3)]."
= -4x + 4 with remainder 2
How is this equal to 0??

I think you reduced the problem incorrectly. Try to solve for x again. also, the expression reduces to zero when x = 1. It is undefined when x = +2 or +3.

Just focusing on the main question :
What is an Edge ?
Is it the boundary condition ?
Or is it something which gives a sense of End or start?

Take for a Moment our Own Earth.. now do we know where is the Edge?

Good morning. Have you folks had a chance to read Maldacena's article in the November issue of Scientific American on "the illusion of gravity"? It has me thinking over the past few weeks and seemed relevant to a few points you were discussing.
In particular I found the point about the thickness of a string at the holographic boundry (without gravity) being the equivalent of the location of the particle in the '3D middle' (with gravity) mentally consuming.

I have also picked up a book called 'The Mind's I, Fantasies and reflections on self and soul' by DR Hofstadter and DC Dennett. It is an interesting compendium of writings on what consciouness might be and I found the excerpts from Richard Dawkins' 'The Selfish Gene' very interesting. Helped me pick up some new thoughts.

Glad to have found the site.

Read it and I like it. It just might be crazy enough.

I don't get how gravity works when there is a vacum (outer-space) between the two bodies of mass that attract eachother. Can someone please explain.

Your concept of the vacuum is faulty: There is no such thing.

The "vacuum" is seething with virtual particles. You'll find no place in the universe, of which we are aware, where a true vacuum exists. The vacuum containing nothing is a purely theoretical construct with no physical reality.

I suggest you hit google.com and look up:
"Casimir Force"

Good morning all. I would like to try my hand at replying to Rob's Christmas message:

I don't get how gravity works when there is a vacum (outer-space) between the two bodies of mass that attract eachother. Can someone please explain.

I saw DA's reply and I believe this answer is correct. However, it will do me some good to try and refresh my notions of gravity in a more general sense.

According to the things I've read, the classic basic answer is that the force we call gravity is attributable to the warping of spacetime around massive objects, like a planet. The force you feel is actually due to the curvature. I believe the force of gravity is inversly propotional to the square of the distance between the two objects.

The somewhat simplified metaphor I keep in my head is the way water wraps around any object (that sinks) when you toss it into an aquarium. The 'warping' of the water is like the warping of spacetime around a massive object.

I can appreciate the classic bed-sheet or trampoline analogy but the aquarium works better for me because it completely surronds the object, whereas the bed sheet is two-dimensional.

Rob, to be honest I do not know if when physicists speak of the universe being flat they really do mean like a bed sheet or this is only a simplified analogy that is used for explanation. I do know there is constant debate about the shape of the universe and I try to take in as much as I can about the various arguements (positive curvature = spherical, negative curvature = modified saddle).

As DA alluded to, this flatness on a large scale may hide a very different view when the physics of the small comes into play. There are theories which suggest virtual particles poppping in and out of existence and all of this contributing to a seething bath of uncalculable variability at the quantum scale. So far, the two have not been able to meet. But this is the Gordian knot for a certain group of physicists and lay people who like to think about these things.

My personal belief is, like with M-theory, someone with special vision and talent (like Wheeler) will come along and show us how the big and the small are really the same thing and we have just been looking at them as different, assuming they are different. The math takes the theorists in different, somewhat opposing directions. My hope is an optimistic one that the two are the same and we just need some mathematical vision to look at gravity the correct way.

Please see my original post and reference that Scientific American article for someone who might answer you more in depth.

The answer is waiting.

Sorry, Rob, I got up on the soapbox there for a minute. My first paragraph is hopefully helpful.

mark

Rob,

I just remembered something else that may be helpful. If you have time to read Hyperspace by Michio Kaku, this may help.

Being a conceptual thinker myself, his analogies, pictures and descriptions were invaluable in helping me understand some of the mathematically rigorous concepts.

Happy holidays,

mark