My friend and I work in a molecular biology lab, with regular access to a -80C lab freezer.  The other researchers' and students' sample tubes/vials are kept in boxes or sealed ziplock bags in the freezer.  Occasionally, after a period of storage, a random ziplock bag will be inflated almost to bursting point.  On speculating why this could be, I suggested that the water droplets in the air that is trapped in the bag will freeze rapidly and hence expand, and the pressure increase causes the bag to inflate.  My friend disagrees, reasoning that expansion of water droplets alone can't possibly account for the huge increase in volume inside the bag.  Who is right or, if neither, what is the correct explanation?

It is a physics fact that a bullet shot and a bullet dropped hit the ground at the same time. If you could shoot a bullet so fast that it went right round the earth and land at your feet, would that take the same time as it takes for a bullet to drop from the same height as the gun? or does the theory rely on a theoretical flat surface?

If I place a block on a conveyer belt moving at 10m/s then place that conveyer belt on another conveyer belt moving at 10m/s in the same direction the block would now be moving at 20m/s. We are always told it is impossible to get things quicker than the speed of light but with enough conveyer belts moving at high enough speeds why would it not be possible to get the block moving this fast? All impracticallities aside

I recently saw a video on the internet of some dolphins playing with bubble rings in their water tank. These rings seemed to be just shaped bubbles but how do they form? and what sustains their peculier shape?

Here is a link to an example of the bubbles:

http://www.boreme.com/boreme/funny-2009/dolphin-bubble-behaviour-p1.php

I walked into my study this afternoon at 2 and saw an odd reflection on the West wall. As my eyes grew accustomed to the darkened room I realised it was no simple relection but an inverted image (IMG_1987) of our garage outside to the East (IMG_1990).

The light was entering the room through a triangular gap in the curtains where a curtain hook had broken (IMG_1989).

It seems a large and irregular gap to create such a clear image. How large can a 'pinhole' be and still create a clear image? What determines this size?

Time has not been around forever. Most scientists believe it was created along with the rest of the universe in the Big Bang, 13.7 billion years ago.

Some physicists like Michael Berry, Thomas Gold, and Steven Hawking have also proposed that time may reverse when the universe begins to contract. Using this as our base grounds, could we go into future or fast forward the time if we could somehow increase the expansion rate of the universe?

Can light go faster, or slower, than light speed? If so, what do we call that speed?