a flat universe?

[Cadmus]

I know you weren't mocking me, I just don't like to leave loose ends open.

I have never mocked you.

 

The book I got the info from is called "The Matter Myth" by Paul Davies and John Gribbin. On the specific page 122 of that book, it states "The big bang was the abrupt creation of the Universe from literally nothing: no space, no time, no matter". To me this imples there was nothing before the big bang.

I think that your interpretation is too strong. First of all, all of this is speculation, no matter how educated. Therefore, at best I think that you should consider that it implies that "it is currently believed that ...". Second of all, I think that what they mean is the abrupt creation of the universe as we know it today. I find it difficult to believe that they want their readers to take it from them that it is absolutely certain that nothing existed before the Big Bang. Pre Big Bang era is outside of the consideration of most scientists, due to the (fairly) complete lack of evidence. Therefore, I think that they ignored any such era, if it exists, rather than explicitly denying any such existence.

 

On specific page 120 of that book, it also states "Space itself, and time were created, like matter, in the big bang; there was no "outside" into which the explosion occurred." To me, it implies there is nothing more than what the big bang created.

Again, I think that they are referring to the universe as science is able to study it now.

[Bettina]

I have never mocked you.

 

I think that your interpretation is too strong. First of all' date=' all of this is speculation, no matter how educated. Therefore, at best I think that you should consider that it implies that "it is currently believed that ...". Second of all, I think that what they mean is the abrupt creation of the universe as we know it today. I find it difficult to believe that they want their readers to take it from them that it is absolutely certain that nothing existed before the Big Bang. Pre Big Bang era is outside of the consideration of most scientists, due to the (fairly) complete lack of evidence. Therefore, I think that they ignored any such era, if it exists, rather than explicitly denying any such existence.

 

Again, I think that they are referring to the universe as science is able to study it now.[/quote']

 

So what your saying is you don't like the way I presented my statement as if you feel I should always end with "as science is able to study it now"

 

If I'm talking about cosmology in a cosmology group, is it wrong to assume that the reader would already know this? If not, then tell me what I need to say. I want to learn.

 

Bettina

[Martin]

I hope this is right' date=' if not, please correct my thinking.

 

When we speak of the Universe, we can speak two different ways.

 

1. The universe is the entire area that happened as the result of the big bang that we are capable of seeing.

 

2. The universe is the entire area that happened as the result of the big bang and includes what we see and what we are yet incapable of seeing but nevertheless must be there.

 

There is no universe outside of what the big bang created.

 

So if you draw a sphere (or flat piece of paper if your a flatlander) and say that is what the big bang created, then that is our universe.

 

Bettina[/quote']

 

1.if General Relativity is your machine (for modeling time-evolution of universe) and you run it backwards in time then it breaks down at a certain point called the "classical bigbang singularity"

 

2. if you then improve the machine by quantizing it, so that it becomes a quantized Gen Rel, then you can run it backwards in time past the classical singularity, which is now the "bigbang ex-singularity"

 

3. now what does it look like right before the ex-singularity? it is beginning to look more and more like the inside of a black hole.

the model reveals a prior contraction and a bounce or reversal from collapse to expansion----a maxium allowable density having been reached.

 

 

this is all to be understood as qualified by saying ASIATSIN "as science is able to study it now" because of course that's the context of our talks here in this forum. this aint no philosophy/religion club.

 

so the universe, to continue your definition, is what issued from the big bang (including parts of that which we can infer even if we havent seen them)

 

and what you say is quite acceptable, except that the universe also includes whatever we can infer went INTO the big bang

[Martin]

someone reading this (bettina or other) might want a source link

so here is a 6 page technical paper

http://arxiv.org/abs/astro-ph/0309478

go there and click on PDF

much of it is in words----it is far from being all math symbols!

 

since this 2003 paper appeared there have been many more papers dealing with conditions just prior to the classical singularity, and investigating the cause of inflation

 

the closest thing to a popular book about this development in cosmology is the articles by Rudi Vaas in a German science magazine similar in readership to SciAm (but not SciAm). These Rudi Vaas popular articles have been translated. I gave a link to one earlier: "the inverted Big Bang"

[crzykllrghst]

If' date=' by the word 'universe' we mean everything with inertial mass, and everything without inertial mass, then the universe cannot have a shape.

 

Saying everything without inertial mass, is a fancy way of referring to the vacuum. 'Space' cannot be spherical, it cannot be cylindrical, it cannot be a cube.

 

Regards[/quote']

I think i understand what your saying, "how can nothing(vacuum) be something

[crzykllrghst]

I think i understand what your saying, "how can nothing(vacuum) be something

What I think I'm getting at is the universe cannot have a shape

[Martin]

 

...You asked to be corrected' date=' and I did. This is not correct. It is not correct to use the Big Bang as the absolute delimiter of the universe. The easiest way to improve on this is to replace each instance of "universe" in your wording with "known universe".[/quote']

 

I think you are out of line in your use of words, Cadmus. I have never known anyone to use words like you------among scientists. If you include philosophers and Mormon missionaries etc. all bets are off.

 

But really, it is like you never took an ordinary college astronomy class.

 

what Bettina says is universe is pretty much what the prof in Astro 10 would say!

 

He never had to say "known" universe. it was just simply the universe.

 

then there is a region of the universe from which light has reached us and that is called the OBSERVABLE region.

 

but the whole thing, which is what the LambdaCDM model models, and what the Friedmann equations are used to study----this whole thing, which we can infer so beautifully much about----but about which we are still testing our ideas----this whole thing is called, by ordinary astronomers, the UNIVERSE

 

it just aint called the "known" universe

 

so I think you are giving Bettina really poor advice, and that you Cadmus are using words in a kind of idiosyncratic and maybe "philosophically correct" way.

 

Well if you are going to try to correct Bettina from saying universe, then you have your work cut out because you have a whole SFN bunch of people you need to correct and make them say "known"

because (I dont know) maybe you want to leave room for something called the Unknown, or the Great Turkey, or some other thing, which you consider might be Outside the regular universe

Well anyway it looks like you will have to try and reform how everybody talks. It will be fun watching. Please start by trying correct me. good luck

[Johnny5]

I think i understand what your saying, "how can nothing(vacuum) be something

 

I'm not trying to say that, but that would follow from this line of thought.

 

I would say this though for sure:

 

You cannot push on a vacuum, and accelerate yourself.

 

I guess we could do it mathematically too, using Newton's second law.

 

You are about to push the vacuum.

 

Your inertial mass is M, and any acceleration you recieve is a.

 

There is a buoy a few meters off to your left, with a blinking light. And no forces are acting on the buoy, and it's at rest relative to you.

 

Here's what you are going to do, you are going to try to kick space, and make yourself move away from the buoy.

 

Let the inertial mass of the space which you kick really equal zero.

 

The force you exert on it, will equal the force it exerts on you, by Newton's third law.

 

The force on it, will be equal to its mass, times the acceleration you give it.

 

Since its inertial mass is zero, the net force you exert on it, is equal to zero.

 

Therefore you have this:

 

[math] 0 = M a [/math]

 

Where M is your inertial mass, and a is any acceleration you recieve (relative to the buoy) by kicking the vacuum as hard as you can. Your inertial mass is nonzero, so you can divide both sides of the equation above by M, and you get this:

 

[math] 0 = a [/math]

 

So you cannot push off the vacuum, it is nothing. I wasn't trying to say that, but in a sense it follows from what I did say.

[Bettina]

Thank you Martin for the PDF's. I will be reading those in bed tonight.

Martin....I don't mind being corrected like Cadmus did. So, no fighting please.

 

Your all ok with me....

 

Bettina

[crzykllrghst]

I'm not trying to say that' date=' but that would follow from this line of thought.

 

I would say this though for sure:

 

You cannot push on a vacuum, and accelerate yourself.

 

I guess we could do it mathematically too, using Newton's second law.

 

You are about to push the vacuum.

 

Your inertial mass is M, and any acceleration you recieve is a.

 

There is a buoy a few meters off to your left, with a blinking light. And no forces are acting on the buoy, and it's at rest relative to you.

 

Here's what you are going to do, you are going to try to kick space, and make yourself move away from the buoy.

 

Let the inertial mass of the space which you kick really equal zero.

 

The force you exert on it, will equal the force it exerts on you, by Newton's third law.

 

The force on it, will be equal to its mass, times the acceleration you give it.

 

Since its inertial mass is zero, the net force you exert on it, is equal to zero.

 

Therefore you have this:

 

[math'] 0 = M a [/math]

 

Where M is your inertial mass, and a is any acceleration you recieve (relative to the buoy) by kicking the vacuum as hard as you can. Your inertial mass is nonzero, so you can divide both sides of the equation above by M, and you get this:

 

[math] 0 = a [/math]

 

So you cannot push off the vacuum, it is nothing. I wasn't trying to say that, but in a sense it follows from what I did say.

Once again i'm 3rd year HS student, so i'm trying to piece this together, but that make a lot more sense thank you

I like the way you put it