How is a Lizard able to move across the ceiling without falling ?

'Is the box heavy? Should I get it down?', asked my brother Kushagra, with a wry smile. Though younger, he was well built while I was the slender, skeletal one. For good reason, I was given a nickname 'Hanger'; t-shirts just hung down on me. Well that was when I was in 5th standard. I wish someone could call me 'Hanger' today.

'Don't try to be a hero. Will give you a choke-slam, then only will you understand my power. Let mom & dad go, we will have the WWF fight and I will show you who is the boss', standing on a stool, I looked down at Kushagra, my eyes sharp gazing into his with raze. 

'We will see bro, first you try to get the carton down'. 

'Ok. Be quiet. Let me do my work'. Standing on stool, as I pulled the carton from the attic surface, I felt something slithering on my hands. A loud scream followed when I realized that a lizard had jumped out of the carton, onto my hands, and was moving so smoothly towards my shoulders. In all the terror and confusion, I shirked my hands & let go of the terrible monster away from me. But in this hullabaloo, the box fell as well, luckily not over my brother. I too came tumbling down, hurting myself. 

The lizard, meanwhile, slithered across the room, moved up the wall vertically and finally turned upside down to move across the ceiling before finding shelter in the small light opening. 

At that moment, I wondered how did it cling to the wall and not fall down. How can it stick to the ceiling and defy gravity? Let's read to find out.

How is a Lizard able to hang upside down?

Lizards have padded feet. The pads consist of scales which in turn comprise millions of hairs called 'setae'. These hairs completely cover the bottom of the pads of the reptile. Each of the 'seta' contain thousands of thin hair like structure called 'spatulae', that have flat caps at the end. Setae do not stay at right angles to the body; instead are inclined towards horizontal plane. This results in greater surface area. Secondly, they are super flexible, allowing the reptile to move on any curved surface at any angle. These structures together cover large surface area as compared to the size of the lizard.

When a lizard comes in contact with the surface, Van der waals force comes into play; electrons from lizard hair and electrons from wall interact to generate the force. In solitary state, the force is too minute to cause any sort of visible disturbance. However, when these billions of hairs interact, the magnitude of the force increases. This provides the necessary 'stickiness' to the feet, resulting in a fine grip to the lizard. Hence, the lizard is able to cling to walls, speed past the ceiling hanging upside down defying the very laws of gravity.

Nerd Notes:

1. Van der waals force between molecules is distance dependent, and very very feeble
2. There are around 5500 known varieties of Lizards
3. Komodo dragons are one of the largest lizards on earth, reaching a length up to 10 feet

Komodo Dragon

Thanks for reading and keep smiling ! 

- Prakhar