Illustration of red blood cells

Illustration of red blood cells (Pixabay)

Detail of painting of red-tailed hawks fighting

Detail of red-tailed hawks from J. J. Audubon's “Birds of America” (Public Domain)

Image of a machine made from Meccano

Image by Les Meloures (CC BY-SA 3.0)

Artistic interpretation of an exploding light

Image by Pablo Carlos Budassi (CC BY-SA 4.0)

Image of man riding a unicycle

One method of getting around • Photo by Steve (CC BY 2.0)

Image of a galaxy cluster

The Coma galaxy cluster • ESA/Hubble (CC BY 4.0)

Image of blobs of Dictyostelium discoideum

Dictyostelium discoideum • Photo by Usman Bashir (CC BY-SA 4.0)

Image of a series of gears attached to a block of concrete

Ganson's "Machine with Concrete" • Photo by Shervinafshar (CC BY-SA 3.0)

Image of a moose

Photo by Zachery Perry on Unsplash

Image of Chickamauga Dam with inset image of Peter Palchinsky

Chickamauga Dam and Peter Palchinsky (Public Domain)