Science trivia

First, red has a longer wavelength than the other colours, and blue has a shorter wavelength. Now, if an object that emits light moves away from you, the light it emits will be 'streched out' (i.e.; have a longer wavelength), and so, the light will be 'shifted' towards red. (That doesn't mean it'll be red; it'll just be closer to red than it would be normally.) The same happens with blue shift; except the light is 'squished' rather than streched. So the wavelength is shorter, and the colour shifts towards blue.

Olorin said:
Scientists are loking for dark matter because they want to find a solution for all the mass in the universe which they can't find, right?
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Sort-of. But the reason they need more mass is because galaxies aren't following the rules of gravitation. The outer parts of the galaxies should be moving slower than the inner parts, according to the rules...but they aren't. So, either the rules (equations) are wrong – or there's more matter (or something) out there, that is moving slower, as it nears the (real) edge of the galaxy. And of course, if there is a whole bunch more matter that we can't see, it is possible that there is enough more matter to make the universe flat.
 
Huh? :confused: I think you're misunderstanding.. (although, with my explaination, that isn't surprising. :p)

What I mean was:

If the universe has a LOT of mass, it will eventually stop expanding, and come together into one 'lump'. (Hypothetically, of course. As the sun would have been LONG gone by then, I suspect the Lord will come before any of these things come to pass...but it all has to do with the structure of the universe, so that doesn't really matter for the purposes of the theory.) This is called a 'closed' universe (Sometime a 'Spherical universe'). You have to think of this in four dimentions. Then it makes sense.


If the universe doesn't have enough mass, it'll continue expanding faster and faster, and faster and faster.... This is an 'open' universe.


If it has a certain particular mass, it will continue expanding (I think) at the same rate...? And the 4-D shape of space will be flat.

:D

Edit: Here's a pic of the different kinds:

275px-End_of_universe.jpg
 
How do you get a four dimentional cube? A four dimentional plane is hard to imagine; but so is any other 4-D object. Ever tried to imagine a 4-D sphere? :p
 
Sorry to double post. :eek:

Another thing; it helps to know that time is the fourth dimention. You probably already knew that, but; just to be sure.
 
I know, everything has 4 dimensions - length, width, height, and duration. But still, if space were flat, it would be 2 dimensional, right? So which dimensions would it be missing?
 
From http://en.wikipedia.org/wiki/Flat_universe#Flat_Universe

In a flat universe, all of the local curvature and local geometry is flat. In general it can be described by Euclidean space, however there are some spatial geometries which are flat and bounded in one or more directions. These include, in two dimensions, the cylinder and the torus. Similar spaces in three dimensions also exist.
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In other words, it really has more to do with the distortion of the grid lines (take a look at how the red triangles in the picture are distorted) than the outline. (If that makes sense.) So in a flat universe, two parallel straight lines will never touch; while in a closed universe, they would (like on a globe). And in a open universe, they'd diverge.

:p I don't have all that great an understanding of this my self, not having done that much geometery – and none that's not Euclidean. So if I don't make sense, that's probably why. Read George Gamow's "One Two Three . . . Infinity". It's as good as the reviews say. :D (Though keep in mind that he's not a Christian. :))
 
:p I'll say. Although, just because space is flat overall doesn't mean bits of it don't get distorted; as in a black hole. :D
 
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