The bullet thing.

[kpax]

i am sure...i think, that this surface of the balloon must be 3d. According to measurements made by WMAP, and other probes, the value of the curvature K is very close to zero. It appears flat over a very large scale, but may have a small curvature on the biggest of scale...

the problem of trying to envisage this, is that the human brain is trying to think in a 4d way...how can a surface have 3dimensions? unfortunately th human brain has been incorrectly engineered, and cannot even imagine a 4th dimension...

So when the astrophysicists suggest that the Universe is a certain number of light years in diametre where are those measurements taken from. Are the measurements made like measuring the diametre of a spherical object like the Earth? If we are on the skin of a huge balloon where one cannot hardly notice the curvature, the inside of such a curvature must be as irrelavant as the outside of it then?

[narrowbandpaul]

the measurements are made as if the universe was a 3d sphere surrounding us at the centre...not the actual case, but thats the analogy i think

[kpax]

the measurements are made as if the universe was a 3d sphere surrounding us at the centre...not the actual case, but thats the analogy i think

This seems barmy, we see from our view that the Universe is 3-d in shape, we measure it as such but the Human eye is actually wrong and the Universe is flat!

Someone seems to have lost the plot IMHO.

[narrowbandpaul]

it is 3 dimensional and flat...if thats possible

[Paxo]

It's 'mathematically' flat, we just see it in 3 dimensions, go back to very early on in this post with the analogy of the fly on the balloon, it's all a matter of perspective, and an indication of just how small and insignificant we probably are in the whole scheme of things.

Steve..

[kpax]

I'm sure that it may be mathematically flat, but to observers it is 3-d. I'm sure someone if they tried could come up with a mathematical equation that my house it flat too. However, since I bear witness to the fact I can walk in every given direction in my house and also I can see the Universe is also in 3-d I think I'll stick with what I see and witness myself and they can keep their maths.

[Paxo]

Well that's your perogative kpax, but we have come a very, very, very long way round for you to totally dispell the evidence that has been put before you by many people.

Steve..

[kpax]

Well that's your perogative kpax, but we have come a very, very, very long way round for you to totally dispell the evidence that has been put before you by many people.

Steve..

But you havn't shown me any evidence. There is evidence that the Universe is 3 dimensional because we can see it is. You can set off in the space shuttle from any position around the Earth and keep going in that direction indefinately. The mathematics that have been spoken about suggest that no matter which direction i'm heading in once I leave the confines of the galaxy it will be 2 dimensional in true terms.

If this mathematical proposition is correct, then the hubble constant I take it must also be 2 dimensional and space is only expanding within those dimensions?

kpax

[Paxo]

kpax,

Paul and I have gone to great lengths to answer the many questions you have asked and have provided much evidence (such as WMAP, matter time lines etc), it would appear that you are not prepared tp accept any of this, that is you perogative, though these theories are widely accepted by the scientific community, although at times we might not have explained very well

You are right, you look through your telescope, you see a 3d structured world, and we all agree that it is real and that it does exist (though one thing to remember, when you are looking through your telescope, you are looking back in time so the spatial relationships between the objects aren't necessarily 'real'i.e look at a distance galaxy, it's not actually there at this moment in time (though it was when the photons you are collecting left the object x million years ago)). You are failing to distinguish between the universe and the observable universe.

Now where you appear to be struggling is that the size of the universe beyond what you are capable of seeing is vast, it's form and structure is a difficult concept, and by its very nature impossible to annotate for you, your not alone with this, these are some difficult concepts, and you would not be out of place questioning the world you see, but please do not say we have shown no evidence when we clearly have to all of your questions.

I will say, if you get a chance to read Hawking's the Universe in a nutshell, it does break some of these principles down into relatively digestible chunks. You said in an eralier topic that you are a keen amateur, what are your sources of information, what is your background ?

Try this web resource fron Cornell, it tries to explain in simple terms:

http://curious.astro.cornell.edu/question.php?number=171

And this one asks why the universe is flat when we live in 3D

http://curious.astro.cornell.edu/question.php?number=714

A qoute from this:

"when we say the universe is flat it is not in the same sense that a piece of paper is flat, but rather means that the geometry of the universe is such that parallel lines will never cross, the angles in a triangle will always add up to 180 degress, and the corners of cubes will always make right angles. We call this kind of geometry (the kind you learned in school) Euclidean geometry. "

Steve..

[dogfish]

Getting back to 'Inflation' for a mo, I've always been worried that this doesn't merit the 'theory' tag that Steve gave it. From my perspective, i.e. a limited understanding of these things, it looks like a fudge, very like Einstein's constant. A theory that fits the facts, post hoc if you will. For an idea to be a theory, it needs to make verifiable predictions. Does 'Inflation theory' do this?

I'd love to know.

Martin

[narrowbandpaul]

i am not too hot on inflation, but it solves more than just the problem of the smoothness of vastly separate regions. To me a theory is just an explanation for why things are the way they are. Most of the time it can be tested experimaentally, and has predictions that can be tested. Just because a theory doesnt make predictions, doesnt mean its wrong.

Inflation is a theory that says just after the universe was created, it underwent a period of hyperexpansion. From this it sort of predicts that the big bang did produce everything that we see today.

I probably havent explain this very well, but inflation is the mechanism, and the prediction is the smoothness in the CMBR, among other things.

Paul

[dogfish]

Paul,

I know what you're saying, but it still doesn't make it a good theory. What if there was a competing theory that proposed another 'mechanism', explained all the things that inflation does, but also made no novel and testable predictions? How would you decide between them? You couldn't and you'd be stuck with two.

Martin

[Paxo]

Inflation theory was proposed during the 80's to 'polyfiller' some of the gaps left by the big bang theory. A lot of the empirical evidence arises from WMAP, and at present it's the best fit we have, but there is every likelihood that something better will come along as you say Martin, that's how science works, and it is commonplace in cosmology that competing theories exist together until overiding evidence sways one way rather than the other (one that immediately comes to mind is the steady-state and big bang compeying theories). After all we have had a development of theories through Newton, Einstein, Hawking, and as far as we can see at the moment, we don't know what some of the questions are to ask to be able to find out the answers we need.

Some useful texts can be found at:

http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html

Steve..

[kpax]

Don't get me wrong Steve, I'm not ungrateful for the time yourself and Paul have put into these threads explaining these very concepts. I'm very thankful.

Just don't understand it thats all.

kpax