Research in progress

[dreamer_easy]

An overdue thanks for the numerous responses to my biology questions*. I am continuing to investigate the question of the origin of eukaryote tissues. I feel like a doof for not recalling the obvious fact that there are photosynthetic pigments other than chlorophyll. My question should properly have been why green was the most successful colour.

My remarks on the shape of the cosmos have garnered even more comments, leaving me with a fresh question: can the cosmos be described as a three-dimensional manifold embedded in four-space?** Isn't it good we have me around to worry about this sort of thing? I would much rather be pondering this than the source of my next meal, etc.
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* I heard that, you perverts.

** Like the chlorophyll, I ought to know the answer to this, but have forgotten it. I have the vague impression we're living on the three-dimensional surface of a hypersphere.

Comments

[erinbow.livejournal.com]

can the cosmos be described as a three-dimensional manifold embedded in four-space?

Errm, yes, sort of. Probably the most useful model for most day-to-day purposes is the one you use, about the three-d surface of a hypersphere, usually called "spherical space." It would be finite, but unbounded -- no edge. This model, though, does assume a couple of things that aren't properly known, eg:

-how many dimensions our universe has (still an open question when I actually understood this,
which is going on ten years ago.)

-whether the universe is Euclidean ("flat") on a large scale. That changes the sphere part -- we might
also have a similar ellipitcal or cylindrical space (with the two ends of the straight cylinder joined).

-whether the universe is simply connected (like a ball) or multiply connected (like a doughnut).

The Wiki article on this is pretty good: http://en.wikipedia.org/wiki/Shape_of_the_universe

[erinbow.livejournal.com]

(Now, if only I knew where my next meal was coming from....)

[kateorman.livejournal.com]

I love Wikipedia's term "folk physics" (I know the same phenomenon as "armchair physics" :-).