Column: Doctor's Casebook with Dr Keith Souter

Christmas Day is, of course, a special birthday celebration.

You may not know it, but Sir Isaac Newton was also born on Christmas Day, in the year 1642.

It was actually during an outbreak of the Plague in 1665 when he came up with the theory of gravity.

Cambridge University was closed because of the Plague, so Newton went to his home in Woolsthorpe Manor where the famous falling apple set his mind working, thinking about the force that had caused it.

This was gravity.

Along with his theory of universal gravity Newton gave us so many other great discoveries.

He would theorise, experiment, then often find that he was limited by the technology that was then available.

For example, in his mathematical work he had to invent differential calculus in order to be able to progress further.

He was also intensely interested in alchemy and esoteric studies.

Indeed, you may have seen in the recent news that a collection of his unpublished, partially burned notes were sold just last week for £380,000.

They contained some of his calculations to unlock the mysteries of the mathematics and the measurements that were used by the Egyptians to construct the Great Pyramid of Egypt.

Every Christmas I try to come up with an experiment to try.

This one is not a Newtonian one, but the family might find it fun.

Get an empty milk bottle and wash the bottle top.

Bend the bottle top in half so that it can slip easily into the neck of the bottle.

If you don’t have a milk bottle, then another type of wide necked bottle will do instead.

Rather than a cap, cut some silver foil to the shape of the cap and bend it.

Now, lay the bottle on its side and put the bent top just in the rim of the bottle mouth.

With it in that position, then issue a challenge to anyone to blow the cap in to the bottle.

You will find that they will not be able to do it!

Each time they make an attempt, the cap will be blown out of the bottle.

The explanation is that by blowing on the cap you blow air into the bottle – and this increase in pressure forces the bottle top out!