Bitcoin discussion, page-51

I won't touch the stuff either...I can't make sense of it - just the volatility alone scares the crap out of me.

For someone that knows all about it though...can you help me understand this please...

A single bitcoin is currently circa USD$72,000.
If I was interested in buying one but I only had say, USD$18,000 to "invest" does that mean I would own 1 quarter of the bitcoin?
Do I have to wait for someone who wants to sell a quarter of his bitcoin?
If so, how do I know who owns the other 3 quarters?
If I sell my 1 quarter of a bitcoin, do I need the permission of the other holders of the same bitcoin?
If it is possible to divide that 1 bitcoin into many thousands of "investment pieces" - then where is the benefit of holding whole bitcoins?
Given there is a total of 21 million bitcoins, why not have 1 big bitcoin and cut bits off it in denominations that people can buy?

I have plenty of other questions but let's leave it there. As I said - the whole bitcoin thing doesn't make sense.