I often catch myself thinking about the great things that humanity could do if we all worked together. And while it’s nice to think about things like stopping hunger or working for world peace, it’s more fun to think about sneezing. If all of humanity faced the same direction and sneezed at once, how fast could we push a sailboat?

From physics we know that momentum has to be conserved. As an upper bound, let’s assume all of the momentum from the sneezed air gets transferred to the boat. Our lungs can hold about 500 cm

^{3}of air and air has a density of 1.2 kg/m^{3}, meaning that the total mass of a sneeze is given by,mass = (density) · (volume)

= (1.2 kg/m

^{3}) · (500 cm^{3})= 0.6 g.

According to Wikipedia, sneeze speeds lie between 75 km/hr and 1045 km/hr, so I’ll assume an average sneeze speed of 200 km/hr. The world population is 6.7×10

^{9 }people sneezing. From this info, we can compute the total momentum of sneezed air,momentum = (number of sneezes) · (mass per sneeze) · (speed)

= (6.7×10

^{9}sneezes) · (0.6 g) · (200 km/hr)= 2.2×10

^{8}kg m/s.We’ll assume that all this momentum is transferred to the ship.

For our model ship, we’ll consider the fully rigged tall ship Bounty II, which has been featured in numerous films including

*Mutiny on the Bounty, Treasure Island*, and*Pirates of the Caribbean*. It is listed at 412 tons = 3.7×10^{5 }kg. From this we can estimate an upper bound for the total speed it would gain by the entire world sneezing on it,speed = (momentum) / (mass)

= (2.2×10

^{8}kg m/s) / (3.7×10^{5 }kg)= 600 m/s.

This formula also does not take into account the magnitude of my neice's sneezes.

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