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[Putnam]

We don't. The term "exotic matter" basically means "stuff that works mathematically but probably doesn't actually exist", like stuff with negative mass (required for alcubierre drives).

[alway]

Though negative energy (or mass, since they're the same thing) is required in pretty large quantities to explain the acceleration of universal expansion, so it's not entirely outside the realm of current theory, it's just in the gaps that aren't well defined.


IN unrelated stuff, this article was interesting:
Anyway, this article is pretty interesting: http://www.engadget.com/2014/06/04/cortana-microsoft-windows-phone/
It's about Microsoft's "Cortana" personal assistant for windows phone (and likely soon coming to their other platforms, from the rumors I've heard). Apparently they've decided to give the system a much more evident persona and make it much more relatable than the others out there, to the point where it's a major objective for the project.
It will certainly be interesting to see how this project evolves over time. From the aforementioned rumors, this Cortana system (running on the same general "Satori" knowledge engine as bing) will be integrated much more fully into their operating systems, supposedly to the point where you could ideally do anything you wanted simply through the Cortana system, as it would be able to search through all sorts of contextual information on your pc and figure out what you meant when stating something like 'print my boarding pass' and would then be able to go into the file system, locate the files necessary, and print them. Apparently the current phone version already has some features of that sort of information aggregation, but adapting that to a desktop could dramatically change the way most people interact with their computers.

[ChairmanPoo]

I'm betting on it being little more than bonzibuddy with breasts tbh

[Reelya]

That reminded me, not sure you guy saw this:

http://www.pbs.org/wgbh/nova/next/physics/collapsing-4-d-star-could-have-spawned-universe/
http://www.popsci.com.au/science/the-big-bang-may-not-have-spawned-the-universe-after-all,380309

Basically, some researchers modelled a 5D universe, that is general relativity in a universe with 4 spatial dimensions and one time dimension. And they looked at a "star" that has 4 spatial dimensions, and what would happen if it went supernova, with the core collapsing into a black hole. Well, a 3D black hole has a 2D event horizon, and it turns out that extends upwards or downwards in dimension (kinda obvious really). This collapsing 4D star model has a 3D event horizon, and it spews out excess material in a supernova:

In our Universe, a black hole is bounded by a spherical surface called an event horizon. Whereas in ordinary three-dimensional space it takes a two-dimensional object (a surface) to create a boundary inside a black hole, in the bulk universe the event horizon of a 4D black hole would be a 3D object — a shape called a hypersphere. When Afshordi’s team modelled the death of a 4D star, they found that the ejected material would form a 3D brane surrounding that 3D event horizon, and slowly expand.

So, you have this 4D star, it explodes and collapses, and what's left outside it's hypersphere event horizon is a slowly expanding 3D spacetime bubble containing matter, which looks like a good match for our 3D expanding universe. Pretty interesting stuff.

[Reelya]

Well, taking over as far as a lower-dimensional object can take over a higher-dimensional space. It's like a line saying "I'm totally taking over this plane" or a plane saying "I'm going to completely fill up this space". That just ain't happening. No matter how you slice it the lower-dimensional object always takes an infinitesimal (i.e. a fraction which is equal to zero for all intents and purposes) proportion of the higher dimension.

[Putnam]

The surface of the Earth is two-dimensional, but you wouldn't say the Earth is not taking up space. Same with an event horizon; its surface is two-dimensional (or three, in the case of a 4-spatial-dimensional universe), but that 2/3-dimensional surface still encompasses a certain amount of volume/4-content.

It's not so much a line saying "I'm totally taking over this plane" as much as a circle saying the same thing, given that the circle is actually just a one-dimensional set of points (which it is; the single dimension can be measured in radians, even).

[LordSlowpoke]

The surface of the Earth is two-dimensional

explain how

[Dutchling]

The surface of the Earth is two-dimensional

explain how

In mathematics, specifically, in topology, a surface is a two-dimensional, topological manifold.

[Putnam]

The surface of the Earth is two-dimensional

explain how

...The same way the surface of any 3-dimensional object is 2-dimensional? I mean, we even use the term surface area which is measured in meters².

[LordSlowpoke]

The surface of the Earth is two-dimensional

explain how

In mathematics, specifically, in topology, a surface is a two-dimensional, topological manifold.

The surface of the Earth is two-dimensional

explain how

...The same way the surface of any 3-dimensional object is 2-dimensional? I mean, we even use the term surface area which is measured in meters².

we're ignoring curvature then

carry on gents

[Putnam]

No we aren't. Read the first sentence of the Wikipedia article and you'll see that we aren't.

[Sergarr]

Curvy objects do not automatically have more dimensions attached to them. 

[Reelya]

The "earth" as a 3D body takes up space.

But not the 2D surface. You can prove that by breaking up space into little cubes, and working out how many of those cubes contain part of the surface, as an approximation of the volume of the surface. Then, calculate the limit of that, as you let the size of the cubes approach zero. The answer is that the proportion of cubes containing part of the surface approaches zero.

In other words, it approaches a limit where there are an infinite number of non-surface cubes for each surface cube. hence at the limit the surface has zero volume.

[10ebbor10]

A much simpler description of a 2D body is that each location of said body can be described using 2 coordinates.

In case of the Earth, this a spherical coordinate system Link*

*Yes, I know the Earth isn't a sphere, but the system still works (kinda).

[Reelya]

An oblate spheroid can still be navigated by two coordinates, you just interpret them differently.