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Pop a balloon inside another balloon

Can you inflate a balloon inside a balloon? Of course you can so here's a more challenging problem. Can you pop the inner balloon while leaving the outer one unscathed? Hint: the answer is yes but the problem is how.

Balloon trick

Balloon trick (Source: Ruben Meerman)

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You'll need a clear balloon and a dark, opaque balloon.

Poke the dark balloon into the clear balloon (one way is to stretch the black one over a pencil first.)

Inflate the dark inner balloon first (this takes a bit of extra lung power).

Tie the dark balloon and poke the knot deep into the neck of the clear balloon.

Now inflate the clear balloon and tie a knot.

Congratulations! You have inflated a balloon inside a balloon. Now challenge a friend to pop the dark balloon inside leaving the clear outer balloon unscathed.

When your exasperated friend finally surrenders and begs you to show them how it's done, whip out your trusty magnifying glass and take them outside.

Focus the Sun's rays through the clear balloon to form a small bright spot on the dark balloon and BAM!

You have just popped a balloon inside a balloon!


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What's going on?

Sunlight is electromagnetic energy, which causes matter to get warm. In this case, the matter is latex rubber and it gets so hot that it melts, which causes the dark balloon to pop inside the clear balloon. Amazing!

Mucking around with a magnifying glass might be considered child's play these days but the invention of the lens changed the course of history.

The word lens is derived from 'lenticula', Latin for lentils, because of the similarity in shape between the magnifying glass and those nutritious little legumes. The world's oldest lens is known as the Nimrud Lens or the Layard Lens. It was discovered by Sir Austen Henry Layard in the Assyrian city of Nimrud (in modern Iraq.) It is a small disc of polished rock crystal and is dated to around 750BC - 710BC. It has one plane and one convex side with a focal length of approximately 12 centimetres but its optical qualities are considered to have almost certainly been accidental.

In The Clouds, written circa 423BC by the Greek playwright Aristophanes, Strepsiades and Socrates discuss the "beautiful stone you can see right through" that could be purchased from medicine sellers and used to start fires. It took until 1590, however, for Dutch lens grinders Hans and Zacharias Janssen to discover that combining lenses can massively increase their magnifying power and the microscope was born.

Now scientists could peer into the microscopic world and discover incredible wonders such as how babies are made. Before that, scientists thought men deposited a tiny, fully formed human being called a homunculus into their beloved. The problem was that each homunculus must therefore contain even tinier fully formed people creating the even-tricker-to-explain problem of an infinite regression. Then, while looking through a microscope in 1875, Oskar Hertzwig (1849 - 1922) witnessed the sperm of a sea urchin fertilizing a sea urchin's egg and it was curtains for the now almost comical homunculus theory. Thanks, lenses!

Combined another way, lenses opened our eyes to the wondrous depths of space revealing no angry, bearded, trident-wielding men but, rather, huge clouds of dust and gas and glowing spheres with rotating orbs floating around them in numbers that are simply impossible to comprehend. And not only did this thing we call the Universe not turn out to be static after all, nor even just expanding, rather the whole thing, including space itself, is getting bigger and bigger at an ever accelerating pace. All of these Earth-shattering breakthroughs were made with the power of curved glass.

Even those untroubled by trivial concerns like the ultimate fate of the cosmos and the origins of life benefit from the light bending powers of glass. People who have trouble focusing the world or crosswords onto their retina can now see clearly, right into old age. Before lenses, life was a blur for anyone with a faulty focal faculty. Just imagine how many great books might never have been written. Medicine might never have progressed beyond the 19th century shambles of blood-letting and cameras would not exist so we'd still be paying artists to paint our portraits, all if it wasn't for lenses.

So now, rather than just using your magnifying glass to vaporise ants or set wood on fire, you can pop balloons inside balloons and help your mates appreciate one of the most overlooked inventions of all time.

Tags: physics

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Published 16 December 2013

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