Royal Institution Christmas Lectures 2010

Why elephants can't dance

We are all familiar with watching ants labouring for hours on a hot sunny day lifting crumbs or dragging bits of leaf back to their ant hill – but have you ever wondered how hard it is for them?

They are often carrying 300 times their own weight, which is impressive when you consider that the world's strongest man can only lift three or four times his own weight. Are the materials that make up ant muscles much better than ours, or are we just not trying hard enough?

Other weird effects of size come to light once you start delving into the subject. The amount of sleep that mammals need is in proportion to their size, and all animals have the same number of heartbeats but mice use them up quicker than elephants. Mark tells the story of the material science of animal size, how we have pieced together some of the physical rules that govern the strength, life span and dance moves of animals.

Lesson 1: Does size matter when falling?

Suitable for: 11–16

Curriculum and learning links: Adaptation and evolution, forces and gravity

Learning objectives:

• Investigate how volume and surface area affect falling objects.
• Explain why smaller objects have a higher surface area to volume ratio.

Lesson 2: The science of keeping warm

Suitable for: 11–14

Curriculum and learning links: Heat transfers, adaptation and evolution

Learning objectives:

• State that a smaller animal has a proportionately larger surface area.
• Describe the evolutionary adaptations that small and large animals possess to help them keep warm and cool down, respectively.
• Calculate the volume and surface area of different cylinders and hence calculate the surface area to volume ratio.

Lesson 3: How can geckos climb up windows?

Suitable for: 11–16

Curriculum and learning links: Adaptation and evolution, forces and friction

Learning objectives:

• Investigate the relationship between surface area and friction.
• Explain why giant geckos wouldn’t be able to climb up walls.