Expert: Ed - 3/27/2012

Question
QUESTION: We know that negative energy exists but in extremely small quantities. If negative energy exists, then negative mass should also exist according to the mass-energy equivalence (E=mc²). Density is equal to the mass of an object divided by its volume. If an object (most likely particle) has a negative mass (although it is very unlikely), a negative density can exist. The vacuum of space has no density (the value of the density is zero) so light travels at 299,792,458 m/s (this speed limit may have been broken by neutrinos). If a medium has a negative density, can light travel faster than 299,792,458 m/s?

ANSWER: Shivam, you probably already know more than I do, about this.  One thing that came up when I tried to investigate negative mass is the Casimir effect.  There are lectures about this on Youtube:

http://www.youtube.com/watch?v=lPzlv6cvs8A

Look at some of the associated videos, but watch out for science fiction.

Also, there was an old book by Kip Thorne that I think talked about this.
http://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/dp/0393312763

I can't find my copy.  I was hoping to find it in the library before today, and answer your question, but I haven't had time.  

See if this gets you started.  Ask me again in a few days, if you want, and I hope I will be able to answer by then.

-Ed

---------- FOLLOW-UP ----------

QUESTION: we know that our universe comes from big bag and it till expanding means we can think it like spherical shape outer part of this sphere is only space now think in this infinity space only one universe i think that it is not possible so may be there is happening more then one big bang at a time!!! so is it possible?

Answer
Shivam, I think the idea of the expanding universe is that all of spacetime is expanding.  It isn't expanding within a larger space.  All of space is within the universe.  There can't be more than one Big Bang happening within the same universe.

However, there is the theory of baby universes!  Stephen Hawking explains it better than I would.
http://www.ralentz.com/old/astro/hawking-2.html

Keep looking up,
-Ed