112 réponses à ce sujet

[Amatoxin]

Yep, I did say the Universe was finite. It's very weird. It relates a lot to relativity and the fact that the Universe doesn't really have just three dimensions. It's really hard to explain, and I don't really understand it myself, but if you were to fly off into space, eventually you'd come back to where you were in the first place. The best way to think about it is to imagine we're on the surface of a sphere - say on Earth, if you were to keep flying west, eventually you'd get back to where you came from, from the east of where you came from..



Because of this, the Universe can have a finite size (like the Earth) but not have an actual edge.

[GreedIsNoException]

Captain Cornhole wrote...

StarWrecker wrote...

Yep, I did say the Universe was finite. It's very weird. It relates a lot to relativity and the fact that the Universe doesn't really have just three dimensions. It's really hard to explain, and I don't really understand it myself, but if you were to fly off into space, eventually you'd come back to where you were in the first place. The best way to think about it is to imagine we're on the surface of a sphere - say on Earth, if you were to keep flying west, eventually you'd get back to where you came from, from the east of where you came from..

Because of this, the Universe can have a finite size (like the Earth) but not have an actual edge.

Three Deminsions being X,Y, and Z axis, among others; correct?  Talk about shape later, cause that is really neat stuff there.  So if say your just flying around in circles or doughnuts, still would'nt the finite universe still have a edge none the less.  You might go along the edge comeing back to where you came, but still it just feels like there has to be something beyond the edge.  I can't wrap my head around that.

Sigh, you too smart.


In addition before heading off to bed...


Jupitor, a gas giant.   Now I always thought planets like Jupitor and "Bespin" had land mass somewhere down there below.  Yet, apperently I just learned they have no landmass.  Because gas giants are failed stars they have all the certain elements (hydrogen, one of them I think) and a very dense core of those elements, it's just that they failed to ignite correct?   Elaboration would help. ))))))

There is something "beyond" what we like to call the future. But only because you travelled millions of light years that when you get back it would mean travelling to either the "future" or  even possible the past.

[Amatoxin]

Captain Cornhole wrote...
Three Deminsions being X,Y, and Z axis, among others; correct?  Talk about shape later, cause that is really neat stuff there.  So if say your just flying around in circles or doughnuts, still would'nt the finite universe still have a edge none the less.  You might go along the edge comeing back to where you came, but still it just feels like there has to be something beyond the edge.  I can't wrap my head around that.

Yeah, I mean X, Y and Z. The universe isn't 3 dimensional, it's at least 4 - but that only shows on really large distance scales like across the entire universe. Imagine us being on the 3-dimensional surface of a 4-dimensional sphere - much like flat land is a 2-dimensional surface of a 3-dimensional sphere.

It's really hard to comprehend, I admit.

Captain Cornhole wrote...
Jupitor, a gas giant.   Now I always thought planets like Jupitor and "Bespin" had land mass somewhere down there below.  Yet, apperently I just learned they have no landmass.  Because gas giants are failed stars they have all the certain elements (hydrogen, one of them I think) and a very dense core of those elements, it's just that they failed to ignite correct?   Elaboration would help. ))))))

Yes, gas giants are just big balls of gas. Not really failed stars, as they're nowhere near big enough, just very large clumps of what stars are made of. What happens at the centre is that there's so much gas around them, the pressure increases, giving you liquid and solid hydrogen at the middle.

For a star to ignite, it needs to be many times the size of Jupiter. The pressure at the middle needs to be enough to cause enough heat for nuclear fusion to happen - which is a huge amount of pressure.  Jupiter is around 0.000955 times the mass of the sun, and the smallest stars are 0.075 times the mass of the sun. Below about 0.075 solar masses, there's not enough pressure for fusion, and you just get a big ball of gas... admittedly one that is WAY bigger than Jupiter.

[Feraele]

Lamiea wrote...

Captain Cornhole wrote...
Well intelectual debate as in as far as intectual gets on these forums.  Cause lets admit it, most of us do not have a MD is Quantum Psysics.

Yes, that is true... Mainly because it is extremely hard to get a Medicinæ Doctor (id est Doctor of Medicine, also known as a MD) in a non-medical field of study - is Philosophiæ Doctor (id est Doctor of Philosophy, also known as a PhD) or  the term you wanted? Also, I do not know of this " Quantum Psysics" you speak of, could you have meant "Quantum Physics" instead? Still, good luck in your debate Sir/Madam MD of Psysics.

Maybe he "was" talking about Quantum Psychics...   Or Fortune-tellers perhaps?   

Get yer Tarot Reading here!! 

[Amatoxin]

If anyone's curious, here's a neat image I found on Wikipedia that lets you understand just how huge stars are compared to Jupiter. And how spectacularly large the biggest star ever found, VY Canis Majoris, is:

[Feraele]

So earth would be a dust mote in comparison to Canis Majoris..hah

[Amatoxin]

Yup. That star's radius is 229,000 times the radius of earth. That's 2100 solar radii, 2,923,200,000 kilometres or 1,816,267,995 miles in radius. (numbers from Wikipedia)

[AngryFrozenWater]

StarWrecker wrote...

Yep, I did say the Universe was finite. It's very weird. It relates a lot to relativity and the fact that the Universe doesn't really have just three dimensions. It's really hard to explain, and I don't really understand it myself, but if you were to fly off into space, eventually you'd come back to where you were in the first place. The best way to think about it is to imagine we're on the surface of a sphere - say on Earth, if you were to keep flying west, eventually you'd get back to where you came from, from the east of where you came from..

Because of this, the Universe can have a finite size (like the Earth) but not have an actual edge.

There is little evidence to support those ideas. It turns out the curvature of space is within 1% flat Euclidian. That supports the inflation model of the big bang. It would also support the idea that the universe is infinite in size, because (space expansion is accelerating) it is likely to expand forever. NASA's Wilkinson Microwave Anisotropy Probe backs that up with data. Until cosmologists come up with something better, I'll stick with that.

Modifié par AngryFrozenWater, 04 avril 2010 - 09:54 .

[Amatoxin]

There is one flaw with your idea - space is flat... in the absence of gravity. Although this doesn't impose sufficient curvature for the universe to collapse in on itself, it is enough for the universe to have no sharply defined edge.



And space is not infinite by any means. If space was infinite, there would be an infinite amount of mass as the universe is on the whole homogeneous and isotropic. The anisotropy detected by WMAP can mostly be attributed to quantum fluctuations in the sphere of last scattering. (in layman's terms, the universe used to be so hot that light couldn't pass through it - eventually it cooled to the point where light could pass, and this is where the Big Bang's afterglow comes from - it's called the sphere of last scattering). How do we know there is not an infinite amount of mass? If there was, there would be an infinite amount of stars, and we could not see any blackness in space. (I forget the name of the thought experiment).



The fact that space expands at a sufficient rate that you could fly in one direction and never come back is not evidence that it is infinite. Over time, the volume of space will tend towards infinity, but this does not mean that at any point in time it will have an infinite volume.



And when you think about it, space with an edge is a completely stupid idea.



I apologise for what I said earlier about the universe having closed curvature - ie like being a 4-dimensional sphere - it was the thought experiment used when I did 3rd-year cosmology and it is misleading.

[AngryFrozenWater]

No. If the universe has a curvature (any shape will do) then there must be a source that shapes it that way. As far as we know matter is distributed evenly everywhere we measure it. No other source (like a point source, string or brane) has been found to make it any other shape than flat. Gravity does play a role in the flat model, though. Gravity causes the early matter after the big bang to form lumps, and with sufficient attraction these form other forms of matter, and large enough lumps of matter form stars eventually and in the end galaxies. That's the role of gravity in that model. It doesn't shape space into a non-flat curvature, instead it is one of the pillars to the creation of our universe as we observe it.

Modifié par AngryFrozenWater, 04 avril 2010 - 11:27 .

[Captain Crash]

I think the confusion here is what people struggle to picture. There is no curvature or edge or anything tangible by that means. It makes it more confusing by throwing words like that in as you try to create an image or concept which doesn't exist.



Space expands in itself, as a result if you start off at one location and keep travelling eventually you will end up back at your original position.



Its difficult to imagine I know, but that because humans cant accept a mental image of something without defined boundaries. The universe doesn't have this. (Very Simply) Space is created by the objects within it interacting.

[AngryFrozenWater]

Captain Crash wrote...

Space expands in itself, as a result if you start off at one location and keep travelling eventually you will end up back at your original position.

If that was true then there was a curvature.

Invited for dinner. TTYL.

[Amatoxin]

AngryFrozenWater wrote...

If that was true then there was a curvature.

And the expansion of space stretches space itself, imposing a curvature - you are moving gravitational fields around relative to each other.

Captain Cornhole wrote...

Now playing Devil's advocate again, (weather you belive the Universe was created by God or via Big Bang) it has'nt been around forever and light travels slow compared to the vast size of the Universe. So during the 14 Billion Years (I think that is the right figure) it is entirely possible the light from other Galaxies and what have you just simply put might not have reached us yet.

If the Universe was created at some point, and is expanding, then it can't have an infinite size or an infinite mass. We proved that the Universe once was extremely hot and dense from the afterglow of the Big Bang, and we can see the effects of its expansion in that galaxies further away from us are travelling away from us faster.



The idea that if it was infinitely big and infinitely massive we wouldn't see any blackness was one of the first nails in the coffin of the idea of an eternal, infinite universe.

[Pacifien]

I don't have anything to add to the discussion, but I've been using it to further my own understanding of all things dark in the universe. So my purpose is to describe what I think I know to see if anyone wants to clarify, correct, or expand.

Dark Flow
So I've been reading about cosmic microwave background and started to see references to dark flow, just to add to dark matter and dark energy. Rather than a uniform form of movement to galaxies in three dimensions, evidence then demonstrates that some force has been acting on an entire cluster of galaxies, pulling them in a very particular direction. This has apparently been observed to 2.5 billion light years, suggesting this force is acting on the clusters from a distance even further than that. And it's an unknown dark flow.

Flat Universe
So references to a flat universe are confusing given my standard understanding of the definition of "flat." As far as I can tell, to say the universe is flat is to say that the geometry is uniform across three dimensions, there are no peaks and valleys. In which case, I'd think the evidence of dark flow would throw a kink in that perception.

[Captain Crash]

Well I was writing a detailed response but then I realised I was getting nowhere fast.

Debating theory....  Theory can be debated endlessly. Hence this thread will go on for pages and get pretty much nowhere. Yes the answers here are well constructed but every new post is throwing in a different ideology.

Modifié par Captain Crash, 04 avril 2010 - 05:04 .

[Amatoxin]

Captain Cornhole wrote...
That actually makes alot of sence.  You are very smart.  So have you put that Degree, to good use?  Working at any scientific places?

Now every time I watch TV they claim the universe is infinite, in a ratio sort of thing how many scientists out there belive the universe is infinite as to those who oppose? 



Also what type of shape would the finite Universe shape?   I read a book one time (very out of date btw)  and the author suggested that the X,Y and Z Axis form a sphere shaped Universe.  But in combination with the constant flow of time it forms a cylinder.  Thus our Universe haveing at least 4 plus demensions.  Which seems entirely possible.  

Then the author when on to suggest that there are areas in our Universe that get a little skettchy (comaperedto the Universal standard of 4 demensions ( X,Y,Z and Time); with a possible 5th in said skettchy area.  And there where the areas become fuzzy it might be possible to cross over into parallel Universes that have say 5.

I don't think I described it well, but what's your opinion on that?

Well, the overall shape of the Universe is still a matter of debate, as you saw with that little discussion earlier about the analogies that I used. Something that is quite flat in the absence of matter, that has no edges, no centre, and is constantly expanding... it's very hard to understand.

There will be areas in  the universe where space has some very odd geometry. Around black holes, for instance, space will become infinitely curved at the middle (hence how you see those pictures with a big cone that goes into nothing to represent a black hole), and there are many varieties of weird object out there.

As for what I'm doing with my degree... more study at university actually. I'm doing research on lightning at the moment.

[Onyx Jaguar]

If I find out how why your body fails to keep up the healing process as we age I think I could be around long enough to do proper studies proving/disproving all of those steps.



Also that would probably be the next step for humanity.

[ModerateOsprey]

Onyx Jaguar wrote...

If I find out how why your body fails to keep up the healing process as we age I think I could be around long enough to do proper studies proving/disproving all of those steps.

Also that would probably be the next step for humanity.

I have posted this in a number of science threads.

There is a chap here in England researching exactly that.

His name is Aubrey de Grey. His statement to draw attention to his research is, 'The first human to live for 1000 years is alive today'. Wikipedia link here if you wanna follow up:

http://en.wikipedia..../Aubrey_de_Grey

Modifié par ModerateOsprey, 06 avril 2010 - 12:55 .

[GreedIsNoException]

What is the next step for humanity?

Contamination turning us into devolution. You see our ancestors and their work, their science with primitive tecnology and this and aliens pop into people's mind.



The Nazca lines, the Egyption pyramids, Greek astronomy, the calender by the Mayans, the rockets in most ancient cultures.... it leads to many questions and no aliens to prove it.

[ModerateOsprey]

GreedIsNoException wrote...

What is the next step for humanity?
Contamination turning us into devolution. You see our ancestors and their work, their science with primitive tecnology and this and aliens pop into people's mind.

The Nazca lines, the Egyption pyramids, Greek astronomy, the calender by the Mayans, the rockets in most ancient cultures.... it leads to many questions and no aliens to prove it.

IMO, space exploration is the next step - no brainer. We need the minerals and the 'rare earth' elements if humanity is to survive with our current rate of technological progression. 90% of the world's resources of rare-earth minerals are controlled by the Chinese, who will, without a doubt, be working on an extensive space programme, as is India.