Everything You Ever Wanted to Know About Soap Bubbles

Experiments GeekMom


Fabrice Jouvenot, scientific explainer at the French science museum La Cité des Sciences, drives his cycle in Paris’ streets and show “the magic of soap bubbles”.

The video, directed by Roland Cros, is provided by Universcience.tv, the scientific web-tv of the Cité des Sciences and the Palais de la Découverte in Paris. Universcience.tv is charge-free and ad-free… for now, at least.

But let’s talk about bubbles !

Cool things about these videos (not less than 5 Episodes):

  • You don’t need professional material to make these experiments, no complicated installations, everything fits in the bike’s basket.
  • The tone is very educational and casual: after all, he addresses passers-by of all ages and all cultures.

Less cool thing:
I’m afraid that’s in French…

Therefore I need to translate it, especially for you GeekMom readers!

In Episode 1, you’ll learn :

  • What you need to create a big beautiful bubble. Soap? Well, yes, but also two other components. Yes, you got it: water and air.
  • Which soap is the best for bubbles. The purest you can find. As Fabrice says, what you need is soap molecules, not lemon molecules. In France, the purest easily available soap is known as Savon de Marseille. What about American one ? My fellow GeekMoms suggest Green Mountain Soap. What do you think?
  • Why soap washes your laundry. That’s because of the specificities of the Soap Molecule, with its hydrophilic head and hydrophobic tail.

In Episode 2, you’ll learn :

  • Why soap bubbles explode. You have to find the 4 possible reasons. “Because your geekling just punched it” is the easy one. The other ones are more scientific: because of air pressure on the membrane, the larger the bubble, the strongest the pressure; because of gravity that makes the water element slide down the bubble ; and because of evaporation.
  • How you can capture and enclose a bubble, keeping it for days or even weeks! If the box is hermetic enough, you can even freeze the bubble. You’ll only need the neck of a plastic bottle. And be careful, Geekling: punching the hermetic box will ALSO crush the bubble.

In Episode 3, you’ll learn :

  • Why bubbles are so round. That’s because, as everyone on Earth (especially Moms?) they apply the principle of Maupertuis: they always use the least energy and form the smallest possible surface. As Fabrice says : “molecules are less stressed, therefore less tired.”
  • If you or your geeklings are more advanced in physics, you can also speak about the isotropy of space.

In Episode 4, you’ll learn :

  • Where the bubbles’ colours come from. Not from the rainbow, as most people (not only Judy Garland) say.
    Actually, that’s quite difficult to explain in simple words. Let’s say the light bounces twice on the bubble surface (once just outside the surface, once just inside) and the desynchronization between these two moments makes one colour of the spectrum disappear and the opposite be enhanced.
  • So you’ll be able to observe different colours’ stripes if you can keep your bubbles long enough.
munich olympic stadium and its strangely shaped roof
Image: Elcèd77, 2007 (Wikimedia Commons)

In Episode 5, you’ll learn :

  • That Munich Olympic Stadium’s roof looks like the “most economic” form a bubble membrane takes (much more than a picture of Bavarian Alps, as many people say).
  • That we might (or not) create a cubic bubble. Actually, even with the special artifact Fabrice uses, the bubble doesn’t stay cubic. She becomes something like a double pyramid. That’s a Spontaneous Symmetry Breaking, a very useful principle in particle physics, involving the so mysterious Higgs boson. But about that, I’ll speak again later…

If you really need an English-speaking video, you might also watch ‪Time Warp – Discovery Channel – Soap Bubbles Science with Keith Johnson of BubbleArtist.com‬

Far more spectacular. However, a bit less educational, or so I thought. Anyway, Keith Johnson is an amazing Bubble Artist and he offers to come in schools with his show. That is certainly a fantastic experience for our favourite young science students!

But if you wanna teach your kids both Science and French in the same time, you can find Universcience.tv on FacebookTwitterYouTube and Dailymotion. They even propose a video on demand collection.

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