Tricksy liquids

September 1, 2015 8:31 PM

Youtuber brusspup (previously 1, 2) has some cool science tricks you can do with liquids.

Another favorite: T-rex illusion. Stick around for the reveal.

posted by Quietgal (14 comments total)

The T-rex illusion is really astounding (presumably not experienced by schizophrenics).
posted by jamjam at 9:01 PM on September 1, 2015 [1 favorite]

Awesome!!! The demos kept getting more fascinating...the Leidenfrost Effect is particularly interesting, I looked for more info and found this video, researchers working with water flowing uphill.
posted by lemonade at 9:53 PM on September 1, 2015 [2 favorites]

Youtuber Julius Sumner Miller has some cool science tricks you can do with gases.
posted by neuron at 11:04 PM on September 1, 2015

I used to have the T-rex DRAGON on a shelf at work. And you can too! (pdf)
And it's awesome that JSM is on Youtube (after shuffling off ~30 years ago).
posted by quinndexter at 1:08 AM on September 2, 2015 [3 favorites]

It's been a long time since I took fluid mechanics in college but I think the last one where the dye is rotated back to its starting position is a demonstration of the fundamental differences between laminar and turbulent flow. The corn syrup has a high enough viscosity, and the shearing of the rotation is slow and regular enough to keep everything in the laminar regime, making it reversible. As soon as you get turbulence, the flow becomes chaotic and non-reversible, so it wouldn't be repeatable under other conditions. Turbulence also tends to waste energy so you generally want to avoid it when designing something. This kind of stuff comes into play a lot, not just for designing propellers for boats which is the obvious one, but for things like turbine blades (which are all over the place, e.g. electrical generators used at power plants), internal combustion engines, valves, etc. I wish I could remember more of that class because it was very interesting (but also very difficult), but it's been too long.
posted by Rhomboid at 1:14 AM on September 2, 2015 [3 favorites]

Really the one that uses a bottle of water to ignite paper is less of a "cool science trick you can do with liquids" and more of a "cool science trick you can do with your nieces and nephews while mom and dad are busy elsewhere."
posted by logicpunk at 1:34 AM on September 2, 2015 [2 favorites]

Thank you for this post. I will be regaining the title of coolest uncle shortly.
posted by klarck at 6:32 AM on September 2, 2015

The dragon (not T-Rex) was created in honor of Martin Gardiner. I got it from (IIRC) Puzzles magazine.
posted by IAmBroom at 10:07 AM on September 2, 2015

I don't understand the no leak magic bag one. What's the trick?
posted by Just this guy, y'know at 3:06 PM on September 2, 2015

I would guess the very tip of the pencil pierces the plastic, and the remainder stretches the hole open, which means it's too tight to leak.
posted by RobotHero at 5:21 PM on September 2, 2015 [1 favorite]

Yep, just the opposite of the trick where you put scotch tape on a blown-up balloon, and then you can pierce it with a pin without it exploding.
posted by IAmBroom at 6:32 PM on September 2, 2015

OK, jamjam, I'll bite - why would schizophrenics not perceive the T-rex/dragon illusion?
posted by Quietgal at 8:10 AM on September 5, 2015

Sorry Quietgal, your comment got pushed down on my Recent Activity page before I had a chance to see it and I didn't notice it 'til this morning.

I'd say the T-Rex illusion is a version of the face illusion, in which most people see a mask of a face as convex even when it's concave, but schizophrenics mostly see it as it is:

SCHIZOPHRENIA SUFFERERS AREN’T fooled by an optical illusion known as the “hollow mask” that the rest of us fall for because connections between the sensory and conceptual areas of their brains might be on the fritz.

In the hollow mask illusion, viewers perceive a concave face (like the back side of a hollow mask) as a normal convex face. The illusion exploits our brain’s strategy for making sense of the visual world: uniting what it actually sees — known as bottom-up processing — with what it expects to see based on prior experience — known as top-down processing.

"Our top-down processing holds memories, like stock models," explains Danai Dima of Hannover Medical University, in Germany, co-author of a study in NeuroImage. "All the models in our head have a face coming out, so whenever we see a face, of course if has to come out."

This powerful expectation overrides visual cues, like shadows and depth information, that indicate anything to the contrary.

But patients with schizophrenia are undeterred by implausibility: They see the hollow face for what it is. About seven out of 1000 Americans suffer from the disease, which is characterized by hallucinations, delusions, and poor planning. Some psychologists believe this dissociation from reality may result from an imbalance between bottom-up and top-down processing — a hypothesis ripe for testing using the hollow mask illusion.
...

posted by jamjam at 2:56 PM on September 7, 2015 [1 favorite]

Ah, that's interesting. Thanks, jamjam!
posted by Quietgal at 4:45 PM on September 12, 2015 [1 favorite]