The truth about toilet swirl (2015) [video]
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Using a graphic showing several thousand kilometre-wide pool with one edge touching a pole is disingenuous. At that scale, yes, you're going to observe Coriolis effect.
Hurricanes don't form within five degrees of the equator -- that provides a useful data point for the lower end of the scale required to see the effect.
Sydney's 34 degrees south, but the velocity delta at 1 metre distance would be dwarfed by various other environmental factors and starting conditions. (Temperature deltas and wind, especially for the outdoor pool, vortices produced by the elbow close to what looks like a 19mm outlet, texture on the PVC liner, etc.)
Plus of course in any dual-pool-emptying experiment, there's a 25% probability of this result.
I'm miffed that a single experiment gets described as 'this is science, dude!'.
A single data point is still a data point and this is still science.
Both presenters are enthusiastic and engaging, undeniably. And yes, this is a data point.
But this isn't science.
Partly because they claim they've 'proved it because we eliminated variables' (3'57"), when they clearly haven't.
Partly because one of the basic tenets of science is repeatability. As I noted above, there's a 1 in 4 chance of getting this result if you assume equal probabilities of clockwise / counter-clockwise. That assumption should be the starting point of any experiment around this effect.
Food colouring should have been put in - for some of the repeated experiments at least - before the valve was open, to confirm the water was in fact still motionless. (Or to show that it wasn't.)
Similarly that little match-stick cross on one of the pools - those should have been present on both pools, probably several of them, spread around the surface (though surface motion is not necessarily indicative of sub-surface movements).
I could go on.
We've had pop science before (Mr Wizard anyone?), and we're just seeing more of it today. Real science is slow, methodical and doesn't infer causality from one experiment. It says, "Maybe x caused y; let's do some more tests." It's the QA person who says "Happy path works. Let's break it and see if we can inject some Javascript."
Bill Nye is a mechanical engineer/comedian/kids host. Tyson is physicists. They're smart, but they're not experts on everything.
Like I said, I like these guys, but I realize it's not science. It's half entertainment/half makes you think. In these videos it's fun, but in the political arena, _science_ presented this way can be weaponized:
From the video description:
"For the record Destin and I repeated the experiment 3-4 times each in each hemisphere and got the same results every time."
'3-4 times' sounds a bit wobbly -- I'm hoping that they meant they repeated it 3 times in one place, 4 in the other.
My other half is a science educator, so I'm also very aware of the problems of getting kids (or even adults) excited about science.
On the other hand, I don't like the pseudo-science cruft the media and our society is full of, and I suspect there's some vague links between misrepresenting what the scientific method actually looks like, and people taking advantage of that growing murkiness.
I'm not questioning the credentials of these guys. Just the validity of this ersatz experiment.
> ... gotten some sensor experts to see if they could quantify the "stillness" of the water, etc.
They did have some archetypal (glasses-wearing) geek do a quick sound bite towards the beginning describing the effect being observed at small scales as 'bunk', but that's all we get from that side of the argument.
Interestingly in the video you can clearly see there's direct sunlight hitting one side of the indoor pool, and parts of the outdoor one. And during the time lapse section of the video, you can see surface debris on the indoor pool swirling around.
If the Coriolis effect worked at this scale, then you'd see consistent circular motion of water in these sized tubs even without emptying.
Given the result was shown on the video there is a 100% probability it would happen for the attempt shown on the video.
I've also never clogged an AU or NZ toilet. Not to say you can't, just that it's much more difficult with their design.
I have also driven across the Equator twice - once in Ecuador[1] and recently in Gabon, West Africa[2].
It's funny to watch the guys standing on the Equator tricking tourists with a swirl of their wrist to supposedly demonstrate this effect.
I thoroughly enjoy watching the stars change as I progress from the Northern Hemisphere to the Southern, and the water direction slowly change.
Television is wonderful.
Take the average Nova or Frontline episode. It's not cheap to produce. Do you think people could afford to put the work into making shows like that if all they could count on was the crumbs that Google threw at them from page views on Youtube?
And even if the funding could be solved, how would you discover this programming? There are very few HN submissions that ever get much notice. And the HN crowd is not nearly big enough to provide enough Youtube eyeballs to actually fund "real" programming.
just lol, they are so excited... I do hope they realise that there was never any debate about the Coriolis effect being real, cos ya know... math. Only debate was that the effect is not strong enough compared to other forces acting on small vortices in fluids, i.e toilets.
Pretty sure there's no debate here, it's not.
http://www.nature.com/nature/journal/v207/n5001/abs/2071084a...
As you can read below, even with extreme care the Coriolis effect can be overwhelmed by very small perturbations such as how the lid is lifted.
http://web.aeromech.usyd.edu.au/history-chapters/C3%20Thermo... ...
> At Tom Fink’s invitation, Professor Lloyd M. Trefethen of Tufts University, USA, spent a short sabbatical in Mechanical Engineering in 1964/65. Already famous for his work on surface tension phenomena, he led us into a repeat of the experiments on the bathtub vortex that had recently been conducted by Ascher Shapiro at MIT. After much careful design, a circular tank of some 2.4m in diameter and 0.4m depth was constructed and installed in one of the subterranean dungeons of the old Peter Nicol Russell building. Carefully designed procedures and their diligent execution resulted in absolutely conclusive results that were published in Nature [Trefethen, et al, 1965). A re-enactment for the local media was a disaster: Bilger and Tanner muffed the removal of the covering baffles creating a great vortex in the water that then went out the wrong way. ‘Scientists baffled’ cried the media. We even made Time magazine!
Actually, Veritasium merged the two videos into one because it is easier to watch on a smartphone. https://www.youtube.com/watch?v=mXaad0rsV38