Before we begin, pause this video and go to
your kitchen and find the sharpest knife you
can.
Knives can be very sharp.
But what is the sharpest knife possible?
Let's start by seeing what makes a sharp blade,
sharp in the first place.
It all has to do with the cutting edge of
the blade - I probably didn't have to tell
you that.
What makes a knife sharp is the width of this
final edge.
The wider it is, the duller the knife.
The funny thing about this is that what you
think is the cutting edge actucally isn't.
If the blade is sharp enough, you won't be
able to see it at all.
You don't believe me?
The smallest thing that humans can see is
roughly 1/10th of a millimeter.
The cutting edge of this blade is 50 times
smaller.
If you put a red blood cell on it, it would
look humongous.
That's how narrow the tip has to be for a
knife to be sharp.
And while you're sitting there looking at
your knife and thinking how sharp it is, you
can go and try to find this thing - a razor
blade.
The width of the cutting edge of a very sharp
knife is aroud 2,5 micrometers or 2500 nanometers.
On the other hand, razor blade has that edge
narrowed down to 30 nanometers.
80 times more.
Or less?!
If we were to magnify the razor a couple dozen
times, we would see something like this.
Now, we think that this is the cutting edge.
But, let's magnify it a bit more.
This is a cutting edge, right?
No!
THIS is a cutting edge.
This is what makes a razor so sharp.
We can't conceive something on that scale.
That edge is 3000 times smaller than the width
of the human hair.
HIV virus is 3 times bigger.
You actually can't see that edge even with
the help of the optical microscope because
they only go down to 200nm.
I never would've imagined that something so
simple as a knife, can powerfully blow me
away.
Thanks for watching and continue expanding
upon your curiosities.
I'll see you next time.
