Question

I heard some people saying that the universe was flat. Does anyone has something to say ? I want to understand.

Answer 1

Friedman and Lemaître (they are astrophysicians) showed that there are only three
possible geometries for a space-time in four dimensions which
the spatial curvature is constant.
If this curvature is positive, it obtains a kind of three-dimensional sphere.
This curvature can be rather negative. This leads to an open universe (or hyperbolic) whose form, reduced to two dimensions, evokes a saddle.
Between the two, the curvature may be null. It is said that the Universe is flat.

Answer 2

The results of observations of Boomerang (balloon) and Planck/COBE satellites shows that the universe is flat like an hyper-cake.
But that does not mean that the universe is flat like a disk volume is infinite!

Answer 3

To better understand, we can take for example the fact to draw a line on the surface of the Earth, in fact this line is a curve because it follows the sphere that forms on the planet. For the universe, if it is flat, a straight line will be a real straight line !

Answer 4

for the sentence "But that does not mean that the universe is flat like a disk volume is infinite!" it's rather "But that does not mean that the universe is flat like a disk, BECAUSE ITS volume is infinite!"

Answer 5

Like an hyper-cake ? (Nom nom nom)
Well, this is really hard to conceptualize. But by intuition, it sounds right. I mean, I should read more about it to understand it better.
By the way, thanks a lot, you really are my hero. (YAY)

Answer 6

Here are the three possible different curvatures

Answer 7

i didn't get the straight line thing.. :-/

if you draw a straight line along the curvature of the earth.. indeed it forms a circle.. (almost).. and you say the universe sees it to be flat!..

if thats the case.. that means somehow we are able to counter that flatness?!

Answer 8

I think he meant that if you draw a line into the void of the universe, the line will be straight. For the flatness thing, you should read some articles about it.

Answer 9

can you suggest me any brilliant article that suggest what people mean when they say universe is flat?!.. a way to understand?? cause the moment i hear this.. all i understand is universe is definitely not like a piece of paper.. so anything?!

Answer 10

Most scientists support this theory of flatness of the universe. Indeed, the ballon Boomerang (1998) observed the Cosmic microwave background radiation to a small region of the sky (in the order of 3°).

The measurements showed that the temperature fluctuations in the sky formed the main spots of about 1 ° wide.

However, the apparent size of these spots depends on the route that followed the fossil light before reaching us. And this path itself depends on the geometry of space !

Answer 11

First, our great friend Wiki : http://en.wikipedia.org/wiki/Shape_of_the_Universe#Flat_universe
This Nature article : http://www.nature.com/nature/journal/v404/n6781/full/404955a0.html
Some datas : http://www.universetoday.com/37029/flat-universe/#gsc.tab=0
Some other answers : http://wiki.answers.com/Q/Why_is_our_universe_flat

I'm drowning under the informations. This is sooo interesting. You can find some other things by typing "flat universe" in Google or Google Scholar.

Answer 12

yea but my problem is this..

for example closed universe.. which means its like a sphere in 3 dimensions.. that doesn't make any sense.. you need higher spacial dimensions to have something like that.. and we know we don't have higher spacial dimensions!

Answer 13

For more information about The BOOMERanG experiment (Balloon Observations Of Millimetric Extragalactic Radiation ANd Geophysics)
http://en.wikipedia.org/wiki/BOOMERanG_experiment

Answer 14

@Mashy maybe we're not living in a closed universe. For the question of higher dimensions, maybe we have but we don't understand them yet.

Answer 15

@Mashy If we live in a kind of three-dimensional sphere (this is no longer the surface is curved, as in the classic case of a sphere, but the volume itself). The volume of the universe is finite but without boundary then, like the surface of a sphere is finite without having limits: an ant who travels can still walk straight ahead without stopping.

Answer 16

yea i get the analogy.. but i am saying this.. its possible to have a sphere finite area but unbounded walk forever thing.. only because you HAVE a higher dimension.. else you wouldn't be able to

similarly if you want the universe to be curved.. you need a higher dimension.. and higher spacial dimension.. so how can you just take an analogy.. and say it works at lower dimensions .. so it might as well work here.. without first speculating whether or not we got higher dimensions?

Answer 17

Some quite simple articles by the BBc : http://www.bbc.co.uk/news/science-environment-11810553 and http://news.bbc.co.uk/2/hi/science/nature/727073.stm

Answer 18

Maybe the universe is not flat, and we can not be really sure ! But for now all measurements seems in line with the theory of flatness

Answer 19

Maybe we have.. but don't you think.. instead of trying to think what is the shape of the universe.. we must focus on trying to find the higher dimensions first?!? since all the math is based on the fact that we DO have higher dimsesions?!?

i mean tomo if we finally find out that we do not have.. somehow if we proved it.. then all the theory gone to the dogs.. or maybe there are higher dimensions and they totally different than the ones lower.. which for example maynot allow such curvatures of space..

all m saying is.. that these theories are only based on math.. and analogies.. why not focus on first trying to find out whether whatever we ASSUME (higher dimensions).. are they really and physically present or not?!

Answer 20

Well, that's an amazing ambition and it would resolve so much problems and avoid so much mental tortures if we find out that those higher dimensions reallyy exist. What a relief it would be. So you're right, we should prove that first. If you have any idea, I'm in.

Answer 21

lol.. its just a thought.. i have no expertise what so ever to even begin :P

Answer 22

@Mashy I agree with you, it's a possible fact.
I think for the moment only the math and analogies can be used to construct a standard model of cosmology, scientists need it because they want to explain all phenomena that are accelerating the expansion of the universe ... And at this time it seems to work well !

Answer 23

We have a lot of work to do guys, so let's get started at our own scale :)

Answer 24

@BuFu
but what if its all wrong.. the math might be working.. but we have got it all horibbly wrong? :P.. all i mean to say .. everything is based on certain fundamental assumpstions.. and we should not take those assumptions for granted!..

Answer 25

Sure, we should'nt, but if we don't make hypothesis and test them (that implies take those fundamental assumptions, that basically are only hypothesis, for granted at least for a short time), we can't find anything new. I believe that it's the nature of research and science : trust, try, fail, create something new, try again, trust maybe. We have time and all is about trying and find something new and try again.
Well, @BuFu, don't you agree ?

Answer 26

when you go fishing.. whats the point in thinking about how you gonna eat your fish.. (assuming that you have a fish).. and not catch a fish at all? :P.. first spend time to catch the fish.. then think about eating! ..

Answer 27

@MagaliH I agree !
@Mashy we can not compare fishing to cosmology ! the study of the universe request of the observation and modeling, we can not really do much else!

Answer 28

@Mashy You're absolutely right, but go tell to scientists that they have to focus on the begining ! Once someone thought that he found something new, even if it's completly false, a lot of people will run to answer this question even if the basis are not even stable. If a guy says "hey, I know how to cook this fish !", nobody really cares if he caught a fish or not, some guys will test his hypothesis, see if it's right or wrong and most of them will never try to catch a fish again, because this question does not interest them at all. But on the same river bank, some other guys will try to get some fish at the same time.

Answer 29

hmm yea i get it :).. see.. MagaliH actually proved that fishing is similar to cosmology :D.. lol nice!

Answer 30

Maga is smarter than me :)

Answer 31

technically m smarter.. check out my smartscore :D lol

Answer 32

I'm pretty sure if you look at the side of black hole, it's could look like the side of a piece of paper, but look into it, and it would appear to be vastly deep. Anyone have anything on this?

Answer 33

true.. but what about it?! :P.. what are you trying to say using that fact?

Answer 34

@pasolinifan So black holes now ? Well, I will search for answers but I don't garantee anything.

Answer 35

@pasolinifan Here are some links to begin with black holes : http://www.thenakedscientists.com/forum/index.php?topic=37541.0
http://cosmoquest.org/forum/showthread.php?68289-The-shape-of-a-black-hole
http://www.technologyreview.com/view/418032/black-holes-can-form-rings-helices-and-even-saturn-shapes/
A video and some other informations : http://www.space.com/18494-black-holes-magnetic-fields-spin.html