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Testing If You Can Blow Your Own Sail
Learning Stats
CEFR Level
Difficulty
Subtitles (388 segments)
I'm about to plug in this fan to test whether blowing on this sail
will move the boat forward.
And then I'm traveling 4000 miles to the equator
where I'm actually standing in both the northern and southern hemispheres,
because this line here is the equator, and I'm here to investigate
whether or not this demo for tourists is a scam.
Basically, they pour water in this basin and on the north side of the equator,
it seems to swirl and drain counterclockwise,
but just a few feet away in the southern hemisphere.
The water seems to drain in the exact opposite direction.
It's sort of like how you also might have heard
toilets flush in opposite directions on different sides of the equator.
And we're here to uncover the truth.
But I'm not stopping there because today we're going to investigate
six other physics and engineering puzzles using simple demonstrations as we go.
Because our goal by the end of this video is for you
not just to know the right answers, but more importantly
for you to understand and why they're the right answers.
To kick things off.
Speaking of Hemispheres
did you know the moon in the sky
looks like this in the Northern hemisphere, like in Canada.
But it looks like this in the southern hemisphere, like in Australia.
It's upside down!
And while that is a fun fact, it's even more fun to understand why.
And this is why
As we all know, the Earth is...
a sphere.
So if you were Superman standing at the North Pole
in the Northern hemisphere, you'd look like this.
But if you were
Thor standing in the southern hemisphere in Antarctica, you'd look like this.
Now, of course, the moon over here orbits around the earth
like this, and I'm going to add an arrow to it to help us with orientation.
And so to the Superman at the North Pole
That arrow would point up, but from the perspective of Thor at the South Pole
That arrow would point down from his perspective.
And now I know what you're thinking.
If all that's true, then which way would the arrow point?
If you're Spiderman, standing here at the equator.
Well, according to our model here, it should be sideways
and sure enough, here in Ecuador, at the equator.
I'm happy to report that the moon does, in fact, appear to be sideways
For fun fact two of seven.
If you just stick
two pins into some cardboard like this and then connect them with a string
and trace it out, you get my favorite geometric shape...
an ellipse!
But there's something really special about these two pinholes.
They're called the focus points.
And any straight line you shoot out in any direction from one of the points
will bounce off the wall of the Ellipse and always hit the other focus point.
And here's proof because I've got a laser pointer
at one focused point, a ball of wax at the other,
and a mirrored surface all along the interior wall.
And now you can see, no matter which way I point the laser,
it always bounces off and lights up the wax.
But here's the really cool part.
If you build an actual full sized room
in the shape of an ellipse and then you stand at one focus point,
you can hear even the faintest whisper from anyone
standing at the other focus point, even hundreds of feet away,
because all the sound waves bounce right back to your ears
in fact,
this actual ellipse shaped room was built by John Quincy Adams
in the US Capitol building.
And legend has it, he was a master at anticipating the moves
of his opponents, plotting against him on the opposite side of the large hall.
And now that you know the physics involved,
it should come as no surprise that John Quincy Adams
conveniently placed his desk right on top of this leftmost focus point.
Next up at number three,
everyone knows when you slam
on the accelerator pedal in a car, the stuff in slides backwards.
And then when you slam on the brakes, the stuff inside just keeps moving
forward, including you, by the way
which is why we were seatbelts.
So then why the heck when I'm driving to the birthday party
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