Tag: gravity

JFM China Symposia: Beijing

Video highlights from the third and final stop of the JFM China Symposia in Beijing. We were hosted by Tsinghua University with further speakers from Peking University, Xidian University, Beihang University and the Chinese Academy of Sciences.

Ke-Qing Xia describes how water in the ocean travels the entire globe over the course of 1000 years

 

Colm Caulfield explains how to the shape of a hanging chain is related to turbulence

 

Charles Meneveau discusses wind energy and its future as the current cheapest form of energy in the US

 

Photo: Christian Steiness

 

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Can you pee on the moon?

Question

If, in some miraculous way, one were able to pee standing on the surface of the Moon, what kind of arc would it create?

Answer

Dr Chris Messenger from the University of Glasgow was on hand to help me with Michael’s question…

  • The moon’s gravity is 16% of that on Earth, which means the pee will travel in a straighter arc and about 2.5 times further
  • In a uniform gravitational field objects travel in a parabolic arc – sort of a ‘u-shape’
  • On the moon, the atmosphere is so thin that the pee would follow a very accurate parabola, as can be seen with the dust thrown up by the lunar rover
  • The low atmospheric pressure on the moon would immediately boil the pee which would then fall to the surface as steam
  • Despite the low temperature of the moon (as low as -170 degrees Celsius), the pressure reduces the boiling point of water so dramatically that your pee would boil way below body temperature of 37 degrees Celsius, which is why it immediately turns to steam
  • The freezing temperature of water on the moon also occurs in the same range as the boiling point, which means that the steam molecules will then freeze into yellow ice crystals

You can listen to the full version of Question of the Week with the Naked Scientists here.

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Equations Stripped: Newton’s Law of Gravity

I strip back some of the most important equations in maths so that everyone can understand…

Newton’s Law of Gravity not only explained why apples fall to the ground, it also laid the foundations for modern-day physics by using equations to describe the world around us.

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