Beakman explains what adhesion and surface tension are while making DIY bubbles. Then using a rubber band, he shows that the soap film will stick to any edge inside of the rubber band regardless of shape. If you remove the rubber band, then the molecules will stick together in their smallest shape which is a sphere. Then a man demonstrates that there can be square "bubbles" and rainbow shaped "bubbles."

Charlie talks about surface tension in water and why it makes drops of water try to be spherical and puddles attempt to become circles. He also talks about optimization theory and how it applies to matching organ donors with people who need organs.

Galileo explains to his student that, if two balls are dropped at the same height, they will both hit the ground at the same time, regardless of their weight.

Mr. Seaver begins teaching the class a lesson on gravity out of the textbook. He is especially confused by the book's claim that a coin and a feather will fall at exactly the same speed. After Luke challenges him to prove it, he tests the claim.

The students and Ms. Frizzle travel to Mercury, the first planet in our solar system, and learn that they weigh less because there is less gravity on the planet. They enjoy bouncing around with less gravity, and a few students take part in a contest to see who can jump higher.