questions

[sharad]

1. Recently I read that gravitation might be an entropy driven force.
Howeve,r since gravity tends to bring objects together it tries to
reduce the number of objects. Won't this reduce entropy?
2. When we say the universe is expanding, is it creating space it
expands into or is it simply expanding into empty space already
present?

[Tanmay Shankar]

About the second question,
They frequently use the "Balloon With spots" Analogy to describe the expansion.
The idea is that the spots all stay teh same size, but they all get further away from each other.
A proffersor in RSI had said that that analogy was incorrect,
since the balloon is expanding into space,
but the Universe is all the space there is, It doesnt expand into anything.

[sharad]

does it mean that space is getting created?

[Amogh Jalihal]

but that has to mean that space is created in the place of something right...its really counterintutive...and so difficult to understand

[Tanmay Shankar]

Yeah, It is hard to imagine as a physical phenomenon.

[Venkataraman Balakrishnan]

Yes, it means that space-time itself is being "created".

And yes, it APPERARS to be "counter-intuitive", "unphysical", etc.  I could add more adjectives, such as "weird", "bizarre", and so on.

As I was trying to explain in my lecture right at the start of SP-2010, our so-called "intuition" is nothing but the hard-wiring in our brains that enables us to deal  with, and manipulate,  everyday objects and phenomena in what I called the macroscopic "world of middle dimensions". That doesn't mean that one UNDERSTANDS that world, either---to do that, you need careful experimentation and mathematical analysis, leading to the quantitative  science called Newtonian or classical mechanics.

Incidentally, I don't see why the inverse square law of gravitation is any more "physically understandable" than, say, the general relativistic idea that matter causes the space-time around it to get curved or "warped".  They are both statements that require mathematics to express them, although the first might be  expressed rather more easily than the second (in the sense that the mathematics required is simpler). That does NOT  make it any more "intutive" or "physical"  than the second. 
 

So you must get rid of this notion that everything has a simple, MECHANISTIC, explanation. You must also learn to distinguish between a "mechanistic" explanation and a PHYSICAL explanation.  The equations of electromagnetism do NOT have any exact mechanical analogues, and yet electric and magnetic fields are just as physical and real as anything else.

As I repeatedly emphasize, physics has become a reasonably mature subject over the past 400 years or so. This means that its explanations have become both deep and refined to such an extent that  they can only be expressed precisely in mathematical language. That's how nature happens to be, and (remarkably enough) Galileo himself recognized this very early in the day.

V. Balakrishnan