Flatland

Yeah but the balloon analogy does it pretty poorly. From the layman's perspective the balloon is still expanding a way from a "center." If you explain that our Universe should only be thought of as the surface of this expanding balloon then you might as well explain what a hypersphere is otherwise the analogy wouldn't make sense to a layman. In other words, go into more detail.

Close. The balloon analogy is intended to show that a 2D surface does not have an edge or a center, but can still expand.

 

Unfortunately, we see the balloon expanding in 3D space. There isn't any equivalent for the way the universe expands. However, someone has suggested that you can view the radius of the balloon (the fourth dimension) as time and so you see the surface expanding as it moves through time. That is close the the way the universe is described in general relativity.

A finite but unbounded Universe can be thought of as the surface of a hypersphere. I don't understand why that analogy is never used.

There are some forms of cancer that can be cured (at certain stages). There are many people who have been cured of cancer. AIDS, like diabetes, can be treated but not cured.

<br />I think those people misunderstand.  Anytime we inhale smoke, it is carcinogenic.  This is true of cigarettes,

So why do people who use chewing tobacco get cancer if it's the smoke that causes cancer?  There is no smoke in chewing tobacco.

I hope we discover life on Mars soon....

It looks like you are talking about parallel universes in regards to the "many worlds" interpretation of Quantum Mechanics. The butterfly effect has nothing to do with it. The reason there are other you's has nothing to do with probability. Rather it has to do with the "splitting" of one universe into many universes when a measurement is made. Check these links out:

http://science.howst...l-universe2.htm

http://en.wikipedia...._interpretation

If you do not know what (if any) substructure to quarks exists, what indicates that a quark cannot be divided in half?

The same reason that a proton or neutron can't be divided in half? The argument here is not whether or not quarks have substructures but that "half a quark" makes absolutely no sense whatsoever.

Why? It is not so ludicrous to suspect that there is substructure to quarks.

Perhaps but it's most certainty not "half a quark." The point here is that matter is not infinitely divisible.

half a quark

I really really hope you are joking.