Sphaeropteris medullaris
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Sphaeropteris medullaris, synonym Cyathea medullaris, commonly known as mamaku or black tree fern, is a large tree fern up to 20 m tall with a trunk up to 20 cm diameter at breast height. It is distri
Cyathea medullaris
Illustration of Sphaeropteris medullaris by William Jackson Hooker (1862)
Sphaeropteris medullaris can colonise areas of disturbed forests
The black trunk with characteristic hexagonal stipe bases seen here from this specimen from RBGE, Edinburgh
Non-Newtonian fluid
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In physical chemistry and fluid mechanics, a non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity; that is, it has variable viscosity dependent on stress. In particular, the v
Sphaeropteris medullaris
…Sphaeropteris excelsa, with both species growing as much as 50 cm (20 in) a year. The tree produces a red mucilage when the trunk is cut, which is a non-Newtonian fluid. The species was first described by German botanist Johann Jakob Bernhardi in 1801 as Sphaeropteris medullaris. The species epithet medullaris means…
Paint is a non-Newtonian fluid. A flat surface covered with white paint is oriented vertically (before taking the picture the flat surface was horizontal, placed on a table). The fluid starts dripping down the surface but, because of its non-Newtonian nature, it is subjected to stress due to the gravitational acceleration. Therefore, instead of slipping along the surface, it forms very large and very dense droplets with limited dripping.
Demonstration of a non-Newtonian fluid at Universum in Mexico City
Oobleck on a subwoofer. Applying force to oobleck, by sound waves in this case, makes the non-Newtonian fluid thicken.
Slime flows under low stresses but breaks under higher stresses