Is the universe finite or infinite?

Castiel · 22 Feb 2011 at 21:43

Mr Jack said:
No, it isn't. We know, for as close to a fact as we can get, that this is wrong. In fact, it's happening right now all around you and, indeed, in you.

So how is it happening right now all around me and in me?

Something from nothing?

SlyReaper · 22 Feb 2011 at 22:10

You know how sometimes you come across a thread which asks a question? A question you can answer, or can at least give a meaningful input to? But the discussion is populated by people who don't know what they're talking about. People who post provably wrong information with that unshakeable confidence borne of ignorance. And your own well-reasoned post is drowned out by a cacophony of wrong information.

This is one of those threads.

But in case the vanishingly unlikely event happens that someone actually reads this, here goes.

The universe is not expanding into anything. Imagine a road that extends infinitely in both directions. There are dots along this road spaced 1 meter apart. Now if you stretch this road out to be twice as long, it hasn't expanded into anything, but the dots are now 2 meters apart. Infinity: it does not work how you think it works.

Also, we can see much further into space than 13 billion light years. We can see objects approximately 45 billion light years away. The reason for this, despite the universe itself only being 13 billion years old, is that the speed of light is only a local speed limit. Spacetime itself is expanding, and this allows two objects billions of light years apart to move away from each other at more than 3*10^8 m/s.

explicit4u · 22 Feb 2011 at 22:16

SlyReaper said:
The universe is not expanding into anything. Imagine a road that extends infinitely in both directions. There are dots along this road spaced 1 meter apart. Now if you stretch this road out to be twice as long, it hasn't expanded into anything, but the dots are now 2 meters apart. Infinity: it does not work how you think it works.

What? The road goes infinity in each direction, how can you make it twice as long as infinity?

My head hurts

Castiel · 22 Feb 2011 at 22:32

explicit4u said:
What? The road goes infinity in each direction, how can you make it twice as long as infinity?

My head hurts

A better analogy is to imagine a room, in the room is furniture etc...

Now there is nothing other than that room, the dimensions inside the room are changing, the space between the furniture is getting greater, however the furniture isn't actually moving and the Room isn't getting bigger.

Simply put only the internal dimensions are changing.

It is called "The Metric Expansion of Space"

Mr Jack · 23 Feb 2011 at 09:20

Castiel said:
So how is it happening right now all around me and in me?

Time and energy are a Heisenburg couplet, which results in the constant creation - and immediate destruction - of particle/anti-particle pairs. It goes on everywhere, all the time, and has measurable effects.

Bulldog14 · 23 Feb 2011 at 09:26

It is infinite in the sense that it is expanding faster than our ability to measure the expansion. We can therefore not determine a "boundry" making it seemingly infinite. It is finite in the sense that it started at a point and expanded outward from there. A leading outer "edge" is therefore inevitable, making it finite.

What is beyond the edge is in my opinion a simple lack of phsyical law. It can be seen as a void, but it is even less than that. As the universe expands outward it simply creates an area where physics as we understand them can operate. In time matter can coalesce in these areas and form galaxy/stars/planets/creatures and what have you not. Nothing can exist in the void as there is no law to govern even simple things like atomic cohesion. I suspect that if one was projected into the void you would instantly disintegrate at the quantum level (or lower).

Castiel · 23 Feb 2011 at 09:43

Mr Jack said:
Time and energy are a Heisenburg couplet, which results in the constant creation - and immediate destruction - of particle/anti-particle pairs. It goes on everywhere, all the time, and has measurable effects.

That is not something from nothing however.

http://en.wikipedia.org/wiki/Antiparticle

http://en.wikipedia.org/wiki/Matter_creation

http://en.wikipedia.org/wiki/Pair_production

http://en.wikipedia.org/wiki/Vacuum_energy

http://en.wikipedia.org/wiki/Dark_matter

It is conversion rather than true creation out of nothing.

It is a common mistake to assume that "nothing" to a layman is the same as "nothing" to a Physicist. Spontaneous particle/antiparticle creation/annihilation in a vacuum is not "something from nothing" it is driven theoretically by Vacuum Energy or in other words "something"

flibbage0 · 23 Feb 2011 at 09:45

The Dread Pirate · 23 Feb 2011 at 09:48

Apparantly observation of the universe shortens it's lifespan so until I get £1,000,000,000,000 I'm going to keep my eyes open with matchsticks!

[FnG]magnolia · 23 Feb 2011 at 09:55

SlyReaper said:
You know how sometimes you come across a thread which asks a question? A question you can answer, or can at least give a meaningful input to? But the discussion is populated by people who don't know what they're talking about. People who post provably wrong information with that unshakeable confidence borne of ignorance. And your own well-reasoned post is drowned out by a cacophony of wrong information.

This is one of those threads.

But in case the vanishingly unlikely event happens that someone actually reads this, here goes.

The universe is not expanding into anything. Imagine a road that extends infinitely in both directions. There are dots along this road spaced 1 meter apart. Now if you stretch this road out to be twice as long, it hasn't expanded into anything, but the dots are now 2 meters apart. Infinity: it does not work how you think it works.

Also, we can see much further into space than 13 billion light years. We can see objects approximately 45 billion light years away. The reason for this, despite the universe itself only being 13 billion years old, is that the speed of light is only a local speed limit. Spacetime itself is expanding, and this allows two objects billions of light years apart to move away from each other at more than 3*10^8 m/s.

I read it but I didn't understand it. I am a Bear of Very Little Brain and long words bother me

RomanNose · 23 Feb 2011 at 09:56

Lol this thread is what happens when you cross It with mind blowing physics, a whole lot of people who have no flipping clue what is going on.
Stay low, stay low my friends, A level physics does not qualify you to understand what the bleeding hell is going on.

K1LLSW1TCH · 23 Feb 2011 at 09:57

Isn't the Big Bang a porno?

mrk · 23 Feb 2011 at 10:03

Most people seem to be under the impression that The (our) Universe is the only Universe

It's seeming to be more and more likely that Einstein/Hawking's Multiverse theories probably are correct

*Goes back to watching Fringe*

p4radox · 23 Feb 2011 at 10:15

[FnG]magnolia;18525948 said:
Ah, I love it when GD solves problems that have baffled scientists for such a long time!

Join us next week for GD talks about stuff it knows nothing about : mavity - what's that all about then, eh?

Try "Time does not exist" for even more frsutration.

http://forums.overclockers.co.uk/showthread.php?t=18226258

Mr Jack · 23 Feb 2011 at 10:52

Castiel said:
That is not something from nothing however.

It is.

It is a common mistake to assume that "nothing" to a layman is the same as "nothing" to a Physicist. Spontaneous particle/antiparticle creation/annihilation in a vacuum is not "something from nothing" it is driven theoretically by Vacuum Energy or in other words "something"

You've got that backwards. Vacuum energy is not the cause of quantum fluctuations, quantum fluctuations are the cause of vacuum energy.

Castiel · 23 Feb 2011 at 11:08

Mr Jack said:
It is.

You've got that backwards. Vacuum energy is not the cause of quantum fluctuations, quantum fluctuations are the cause of vacuum energy.

Well, its not. You are talking about virtual particles which do not contradict the conservation laws.

Virtual particles are viewed as the quanta that describe fields of the basic force interactions, which cannot be described in terms of real particles. Examples of these are static force fields, such as a simple electric or magnetic field, or any field that exists without excitations that result in its carrying information from place to place. Virtual photons are also a major component of antenna near field phenomena and induction fields, which have only very short-range effects, that do not radiate through space with the same range-properties as do electromagnetic wave photons. For example, the energy carried from one winding of a transformer to another, in quantum terms, is carried by virtual photons, not real photons

http://en.wikipedia.org/wiki/Virtual_particles

http://en.wikipedia.org/wiki/Vacuum_polarization

According to quantum field theory, the ground state of a theory with interacting particles is not simply empty space. Rather, it contains short-lived "virtual" particle-antiparticle pairs which are created out of the vacuum and then annihilate each other.

Vacuum is not empty space. It is simply not "something from nothing" You are confusing spontaneous production of mass particles/antiparticles from virtual particles with there being "absolute nothing" which is simply not the case, it is "borrowed energy" not "created energy"

hawking said:
There are something like ten million million million million million million million million million million million million million million (1 with eighty [five] zeroes after it) particles in the region of the universe that we can observe. Where did they all come from? The answer is that, in quantum theory, particles can be created out of energy in the form of particle/antiparticle pairs. But that just raises the question of where the energy came from. The answer is that the total energy of the universe is exactly zero. The matter in the universe is made out of positive energy. However, the matter is all attracting itself by mavity. Two pieces of matter that are close to each other have less energy than the same two pieces a long way apart, because you have to expend energy to separate them against the gravitational force that is pulling them together. Thus, in a sense, the gravitational field has negative energy. In the case of a universe that is approximately uniform in space, one can show that this negative gravitational energy exactly cancels the positive energy represented by the matter. So the total energy of the universe is zero. (Hawking, 1988.)

In short, in the Universe there is no such thing as "nothing" virtual particles are created due to energy held in the changes in the topology of spacetime, or the gravitational field.

http://www.phys.ncku.edu.tw/mirrors/physicsfaq/Quantum/virtual_particles.html

[FnG]magnolia · 23 Feb 2011 at 11:19

p4radox said:
Try "Time does not exist" for even more frsutration.

http://forums.overclockers.co.uk/showthread.php?t=18226258

I'm so used to these threads, it's passed from frustration to mild surprise that anyone even bothers anymore. We could cut it down to a one-response post by asking : "Are you published - YES/NO?"

Not very entertaining, mind, but it would rid us of the armchair scientists who, seemingly, solve all of the problems that no one else could