The edge of the universe

Morbert

krd wrote: »

We do not know that.

Yes we do.

If you limit your frame of reference to the early universe, which is visible through the cosmic background radiation - clearly visible. Then the universe is finite.

But there's nothing to conclude that space is not infinite nothingness.



Path integrals - when you have a hammer.


I have an idea that the nothingness (I won't call it the vacuum) may have it's own uncertainty principle. Something that allows it to have an infinite number of dimensions but at the same time none. And something that allows it to expand at an infinite rate, and simultaneously contract at an infinite rate. Which sounds contradictory but it might be possible because it's not there. I've been thinking about this. If those two principles are correct, then it might be possible for the nothingness to have an infinite number of universes like our own - and universes with completely different rules and dimensions. But because of a strange kind of relativity - something that allows contradictory infinities - those universes would seem dimensionless to the nothingness.

If the nothingness is expanding an an infinite rate, then the universes are shrinking relative to it at an infinite rate. If the nothingness is shrinking at an infinite rate, then a Doppler like effect makes the universes dimensionless. There wouldn't be a foam, the empty space would always appear completely empty. Even if you could escape one of the universes you wouldn't notice any difference - all your rules and dimensions are allowed. Your chances of seeing or entering one of the other universes would be infinitely small. And I think, if you could enter one, your rules and dimensions would be preserved but you may be forbidden from viewing or experiencing the dimensions and rules of that universe.

You don't need Hawking's idea of a universe bubbling up and tunnelling its' way to a bigger space. It just doesn't need to.

If the same kind of thing is happening in the vacuums in our universe, you can forget about using anything like Planck's constant - or any of our constants to estimate what might be there. You're not going to see a foam either - the chances of seeing anything may be infinitely small, and we may have nothing in our dimensions that can interact with the dimensions of those things.

This is a hodge-podge.

krd

Morbert wrote: »

Yes we do.

How?

Do you have to start with the axiom, that before the big bang there was no space or time. Something like a religious creation myth.

This is a hodge-podge.

It's the popular science section, so I'm allowed do a Hodge Podge.

Morbert

krd wrote: »

How?

Do you have to start with the axiom, that before the big bang there was no space or time. Something like a religious creation myth.

"Before the big bang" is already a problematic statement. Before the big bang is currently as well-defined as "north of the north pole". Instead, we say that the big bang is a topological phenomenon of spacetime, rather than a local event in spacetime.

mooliki

krd wrote: »

No, it isn't a philosophical meandering.

You're in the same frame of reference as the cat. In your frame of reference the cat always remains the same size.

And you've got the idea wrong - the cat can never be infinitely big.

Of course it can never be infinitely big, it doesn't exist. I wasn't actually trying to suggest some sort of cat analogy, simply trying to point out how devoid of scientific reasoning that kind of statement is. Obviously I failed. Carry on.

krd

mooliki wrote: »

Of course it can never be infinitely big, it doesn't exist. I wasn't actually trying to suggest some sort of cat analogy, simply trying to point out how devoid of scientific reasoning that kind of statement is.

What's wrong with the cat analogy? I could have said the cat was neither infinitely big nor infinitely small but in a superposition of states.

What's unscientific about cats?

Justin1982

Damn funny thread.

Shape of the universe and the supposed "edge" of the universe are difficult things to get ones head around.

Noone so far has given a correct description of the shape of the universe that General Relativity and experiment so far seems to indicate.

Incorrect Version that permeates popular science:
Universe exploded from a singular point and expanded out from that point at the speed of light and the edge of the universe is now ~14 billion light years away from us here on earth.........This is false!

Correct Version:
When the universe came into existence via the Big Bang theory (still not 100% proven), the universe was infinite. Its the space between each point in universe that has been expanding the last ~14 billion years.
There is no real edge to the universe. The "edge" is basically due to a limit of our knowledge of the infinite universe. From any point in the universe, the farthest you can see is as far as light has already travelled since the big bang. But as time roles forward, so does the edge. As in we are receiving more and more light from further and further away. You can never actually reach the edge of the universe. Closest we can get to the edge of the universe (even if we travelled close to the speed of light) is ~14 Billion light years away from it.
So for example there is probably some galaxies forming 20 billion light years away from us right now. But we cant see them now as the universe has only been around for 14 billion years. But if we wait around on our planet earth for the next 6 billion years, then our universe will eventually be 14 billion years old and the light from the 20 billion year old galaxy will then finally reach us and we can see it.
This is all presuming that the universe is flat. Experiment seems to indicate that universe is flat so far.
I read something something about the universe having to be flat theoretically as if it wasnt perfectly flat now then back when the universe was less than a second old then it wouldnt have been able to expand to form as we see it. As in if it is non flat now then it would be non flat to the same extent when the universe came into being. This would result in the universe expanding much too rapidly or collapsing straight away.
Inflation adds more to the story but I wont confuse you.

Want to understand then read Simon Singhs book "Big Bang". Best explanation of universe I've come across.

krd

Justin1982 wrote: »

Damn funny thread.

Shape of the universe and the supposed "edge" of the universe are difficult things to get ones head around.

It depends on what you think the universe is.

A good book. Lawrence Krauss A Universe from Nothing: Why There Is Something Rather than Nothing. Though I have to give it a better read - I don't own a copy.

Before Lemaître and Hubble, the milky way was considered to be the universe. Even Einstein said something to Lemaître along the lines of "Your math is correct, but your physics is abominable."

The idea of the steady state universe didn't die until Penzias and Wilson finally put a nail through it in 1964.

Krauss's thesis, which I believe is the conventionally accepted one at this point in time, is that our universe, all the stellar material from the big bang, was formed by a quantum fluctuation of empty space. Krauss says in his book, that space could be filled with universes like our own.

So if the universe is something where something can happen - then the entire universe is endless. And it's mostly endless nothingness.

Incorrect Version that permeates popular science:
Universe exploded from a singular point and expanded out from that point at the speed of light and the edge of the universe is now ~14 billion light years away from us here on earth.........This is false!

You know there are several Yellow Submarine type explanations of the shape of the Universe. One, that I think is attributed to Einstein, is that if you walk any direction in the Universe you'll eventually come back to the same point - I don't know whether that's due to gravity bending space, and looping you back to where you started or if it's like Nietzsche eternal return. Other definitions I've heard, material can travel in whatever direction it's travelling in and never come back to the same point.

A thing about popular science writing, is you're going to see ideas that are known to be wrong for a long time - and you'll see them especially garbled. Like writings on black holes. The most common misconception you'll see written about black holes, is that if you were approaching one, you wouldn't see it. But according to Einstein you'll see gravitational lensing - space being bent around the hole - and according to Hawking, you'll see a lot of light. A giant spinning black hole would probably be the most spectacular sight in the universe. Centre astral objects we can see, appear to be that.

In popular writing you'll see stuff like, as you approach a black hole you wouldn't see anything, and then you'll get turned into spaghetti, but you won't notice this as you'll be frozen infinitely in time. Or you'll see something like, a black hole is an infinitely tiny point in space with no radius.

Black holes are wonderfully mind bending. Like Hawking's photons. Can they be entangled if one is behind the black hole horizon and the other isn't. What about superposition and black holes.