I am taking this month off, and while I'm gone,
five other YouTube creators have lined up some brilliant guest videos for you.
We start with science presenter, Steve Mould.
And when he told me the title of this video I thought,
“No, I can't.”
And then I was wrong.
So: be nice, be kind; Steve, take it away!
You have a super power that you’re probably not aware of,
the ability to hear temperature, or at least,
the ability to discern between hot and cold water just using your sense of hearing
and this is something we can test.
So, I’m going to pour hot and cold water from these identical jugs
into these identical mugs
and it’s your job to figure out which is which.
And I’m going to blur the screen as well
because there may be some visual cues that would tip you off,
one way or the other.
Okay, here we go.
It should have been quite easy to tell which was which.
Feel free to pause the video and leave a comment with your guess, if you like,
but here’s the answer: the first pour was cold and the second pour was hot.
And the reason they sound different is because of the fact
that the water is viscous -- or thick, if you like,
and the viscosity of water goes down when you heat it.
This is something that’s easier to see with a liquid like honey.
So, warm honey is more runny than cold honey,
whereas, with water, it’s less visually apparent.
But when you pour water,
the way it splashes into a cup is affected by the viscosity.
And this change in the splashing of the water changes the sound that it makes
because of various complex fluid dynamic reasons.
What’s really interesting is this is knowledge you already had
due to a lifetime of hearing cold drinks and hot drinks being made.
And like many things, this is something that you knew intuitively,
even though it wasn’t something you were aware of consciously.
Go subscribe to Steve Mould’s channel!
I would recommend his video on a self-pouring liquid as being a good place to start.
Next time, the tale of an engineering disaster.