how does a lizard walk on vertical walls?

Question

One day I was observing a lizard walking on walls as easily as we walk on horizontal surfaces. I got curious to know the physics behind this but I couldn't get to any useful conclusion. I tried to Google it but all the hypothesis like lizards create vacuum while they walk or they secrete some sort of chemical (and few others) were rejected due to some or the other reason, so I thought maybe here I could get some help on the subject.

Answer 1

Kind of hard to answer for sure without knowing exactly what kind of lizard you were looking at, but at least one answer is Van der Waals force, which is a cover term for electrical forces between molecules aside from electrostatic interaction with ions and which can be basically summarized as "neighboring molecules shove each other's electron clouds around, and sometimes that makes them stick". There's an article from 2002 in PNAS called Evidence for van der Waals adhesion in gecko setae which describes experimental evidence for that mechanism. Gecko feet have lots of itsy-bitsy branching hairs called setae on their foot pads which have enough collective surface area to make the Van der Waals force between the gecko foot and pretty much any other surface enough to support their weight.