Millennium Prize

Does the direction water rotates down the drain depend on which hemisphere you're in? Debunking the Coriolis effect in your sink

Retrieved on: 
Monday, July 10, 2023
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A presenter will position three buckets of water – one in the Northern Hemisphere, one in the Southern Hemisphere, and one directly on the equator – and let the water drain out.

Key Points: 
  • A presenter will position three buckets of water – one in the Northern Hemisphere, one in the Southern Hemisphere, and one directly on the equator – and let the water drain out.
  • Tourists are shown that, as the water drains, the water in the northern bucket rotates in one direction, the water in the southern bucket rotates in the other direction, and the water at the equator doesn’t rotate at all.
  • The demonstrator might claim that this strange phenomenon is governed by physics, that it’s an example of the Coriolis effect.

The math behind the phenomenon

    • Roughly, the Navier-Stokes equations relate the change of fluid velocity – how the fluid moves – to the forces acting on the fluid, subject to a few physical constraints.
    • For example, the equations assume that the overall amount of fluid in the system doesn’t change over time.
    • Although there is no known complete solution to Navier-Stokes equations, meteorologists and physical oceanographers can still obtain useful partial solutions.

What happens in your sink?

    • The Rossby number compares the dynamics of the fluid with the Earth’s rotation rate, taking into account how big the system is and how fast it’s moving.
    • A small Rossby number indicates that the Coriolis force has a strong effect on the system, while a large Rossby number signifies that the Coriolis force has a negligible effect.
    • So even though the way water swirls down the drain may be consistent, that isn’t due to the Coriolis effect.

So what did the tourists see?

    • Given the size of the system, physical oceanographers can comfortably conclude that the Coriolis force is not responsible for what the tourists see in those buckets or bowls.
    • Although physical oceanographers can’t deny what the tourists see, we know that the magic trick isn’t due to the Coriolis effect at such a small scale.

Inaugural VinFuture Prize Award Ceremony - Celebrating 4 Scientific Innovations for Humanity

Retrieved on: 
Monday, December 20, 2021
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Prize winners will be announced at the inaugural VinFuture Prize Award Ceremony to be held on January 20, 2022 at the Hanoi Opera House and the VinFuture Sci-tech Week during January 18-21, 2022 in Hanoi.

Key Points: 
  • Prize winners will be announced at the inaugural VinFuture Prize Award Ceremony to be held on January 20, 2022 at the Hanoi Opera House and the VinFuture Sci-tech Week during January 18-21, 2022 in Hanoi.
  • The award ceremony will be held on the evening of January 20, 2022 to honor the winners of the inaugural VinFuture Prize, including the VinFuture Grand Prize and 03 Special Prizes for female innovators, innovators from the developing countries, and innovators with outstanding achievements in emerging fields.
  • As part of the Award Ceremony event series, VinFuture will organize a sci-tech week for the scientific community, and business and start-up leaders in industry and technology.
  • A total of four prizes are awarded by the VinFuture Prize Foundation every year, consisting of the VinFuture Grand Prize valued at US$3 million - one of the largest ever annual prizes globally.