Dark Knight Bob

This was an arguement hawking had with another of his peers at the time before he came up with his theory (it's late and i forget his name but he was pretty damn famous).

Which camp you want to put yourselves in depends on arbitrary things really. Scientists like to entertain both models but generally stick to working with one or the other in order to get things done.

With an expanding universe that does NOT imply new matter being created. All that is happening in the closed universe is that space is merely expanding.

Ion

Creation of space already satisfies the opposite of 'nothing in', something is in, new space is in, so the universe is an open system by definition and the Second Law of Thermodynamics doesn't apply to the universe because it's an open system.

Scientists are working onto observing new matter being created during the expansion of the universe, not just new space entering the universe.

It's just that this scientific work is new.

Dark Knight Bob

Well you can have virtual particles created out of "borrowed" energy. But the energy has to be given back.

That's the method that is proposed to be similiar to how the big bang came about but considering as the big bang theory states that claiming the laws of the current universe apply "before" the big bang are meaningless then it's not really conclussive whether you can say whether an open or closed system applies before then.

Again that's based around virtual particles and possible implications with string theory. Also I never said new space entering the universe. I said the space itself is expanding. Also note that under this model when we talk about space we are talking about something where an absolute vaccum cannot exist. You have either particles or fields existing and interacting.

All empircal experiments show that you cannot have a true vaccum, and that wouldn't imply an open universe because then the universe wouldn't be universaly able to interact with itself.

Ion

Regarding:

.) "...claiming the laws of the current universe apply "before" the big bang..." is meaningless

yes, it is;

.) "...then it's not really conclussive whether you can say whether an open or closed system applies before then..."

we don't know well the big bang and before;
we know that today, the universe is not subject to the Second Law of Thermodynamics like the opening post wrongly claims, because today the universe is an open system;
we see places being destroyed by humans, yet they rebuild themselves slowly in the universe's open system, they don't decay according to the Second Law of Thermodynamics, the Second Law of Thermodynamics doesn't apply.
When the space is expanding in the universe, new space is in, and something added in a system by definition means that the system is open.
I agree that in the expanding space particles and fields are playing.

So when the universe is expanding:

.) new space,

.) particles,

and

.) fields

are in.

Scientists are working on identifying them, but the universe expanding as of today is definitely an open system.

Dark Knight Bob

That in itself is circular reasoning.


The earth is a locally open system because it is powered by the sun. The fact that things decay and you need to put energy into rebuilding them shows you need to have some form of maintainance. Tell me without the sun to power the earth find me a 100% renewable resource. Even the sun itself is finite.

Get an elastic band. You can stretch it without "new" rubber coming into being.

Again see my above statement. You saying that new energy/matter is created. That's never been observed. Energy has always been observed to be transferred.

You haven't really stated anything that really agrees with empirical evidence.

There are no "new" particles that have been observed spontaneously being created and haven't anihalated themselves as heisenburgs uncertainty predicts they would do. you can only borrow energy/matter you cannot create it.

If you're trying to prove somehow that the laws of thermodynamics are wrong then you are most certainly aren't going to convince anyone in a forum. Scientists in the worlds most powerful particle accelerators with hardons for breaking nature can't do it.

Y.B

But is the universe a closed system of fixed volyme?

Dark Knight Bob

cosmologists don't talk in terms of volume because it's impossible to do any calculations if you've got an infinite universe in effect when you talk about volume you talk about boundaries (which is what you need to know in order to calculate volume). Also it's impossible to tell if the universe is infinite at all so in effect it's impossible to give an answer to that question.

You are asking me how long is a piece of string

The preferance is towards using density because you can have a constant density in an infinite and non-infinte universe and still make calculations.

Ion

Regarding:

.) "...Get an elastic band. You can stretch it without "new" rubber coming into being..."

the elastic band is submitted to an outside force, the band forms an open system;

.) "...There are no "new" particles that have been observed spontaneously being created and haven't anihalated themselves as heisenburgs uncertainty predicts they would do. you can only borrow energy/matter you cannot create it..."

there are fields applying to the distance newly expanded, they are added to the universe;
the addition of fields to a system makes it an open system;
the string theory allows for newly created particles, but this is not tested;
one calculation has the mass of the universe increasing, along with the universe expanding;

.) "...If you're trying to prove somehow that the laws of thermodynamics are wrong then you are most certainly aren't going to convince anyone in a forum..."

where did you get the idea that I try to prove that the laws of thermodynamics are wrong?

the Second Law of Thermodynamics applies correctly to closed systems;
the opening post applies it incorrectly to an open system, the universe, and you don't know.

Y.B

But for the second law of thermodynamics to apply, the system has to be a closed one, with fixed volume (IIRC?).

Are you saying that it's impossible to know whether the second law of thermodynamics applies to the universe?

Dark Knight Bob

ah ok i misunderstood your question. i thought you were asking me to give you a value for the volume of the universe.

with expanding space you can still have a fixed volume because you are talking about frames of referance. if i stretch a ruler and measure something with that ruler within the frame of referance of the ruler it's length hasn't changed.

Therefore by saying the universe is expanding you are not saying anything about the size of the universe changing with regard to it's own frame of referance. merely the objects within it.

The analogy was in referance to how you don't need to have new "stuff" to appear to push things apart. The big bang is supposed to be a point of creation of existance whereby the initial "jolt" was given to the universe.

In euphamistic terms it's where God flicked the switch. everythign after that point had a fixed total energy. The big bang theory does not explain fully what the cause of that intial spark was but that doesn't in itself prove that the universe is open. As what we have today is empircally sound with the 2nd law and hasn't been observed to be any other way.

get me experimental proof that this is happening. until you do none of you other follwing logical premises can be considered.

umm the first posts uses the arguement of a closed system to prove the universe has a begining. I agreed that the universe is a closed system but that that fact in itself does not imply a creator. merely that they've said "closed universe + God"