Hey Crazies.
I’ve been thinking, there’s an idea we haven’t given enough thought.
Inertia.
We defined it in a previous video.
An object’s ability to resist changes in motion.
But then Question Clone got involved.
What does that really mean?
And, well, I just can’t help but answer the guy’s questions.
First, let’s get some perspective with a little history.
Even though real science started with Galileo, the story of motion starts much much earlier.
Back when exact dates are a little hazy, there was this guy named Aristotle
in Ancient Greece. and he had some very bad ideas.
Introducing Aristotle Clone.
The natural state of all things is to be at rest.
If you impart motion to a book, does it not stop of its own accord?
Get! Get out! Shoe!
How dare you! Do you know who I am?!
You’re just a clone of Aristotle.
Anyway, I know I’ve said this before but I’ll repeat it as many times as it takes.
Aristotle was almost always wrong.
But his ideas sounded pretty believable, so humans were convinced he was right for
about 2000 years.
Fast forward to Galileo.
Real science began when Galileo started doing experiments.
You know, actually testing our ideas before claiming them as fact.
Galileo discovered something very important: Relativity.
No no no, not the Einsteinian relativity, just basic relativity.
We did a whole video on it as part of a series, but here’s the too long don’t watch version:
Steady motion in a straight line for one observer could easily be no motion for another observer.
Therefore, they are the same type of motion: Inertial Motion.
Inertial, as in Inertia, as in Inert-sha. Eh?
Root words for the win!
The point is, when Aristotle said this:
The natural state of all things is to be at rest.
He should have also included steady motion in a straight line,
because that’s indistinguishable from being at rest.
And this brings us to Newton and the Principia Mathematica.
I have a copy of this somewhere.
Ah! Here it is.
Let's read, shall we?
Law 1: Every body perseveres in its state of being at rest or of moving uniformly straight forward.
Newton’s first law of motion actually defines inertia.
It’s a tendency things have to stay still or keep steadily moving
like this,
or like this,
or even this,
If you want to know what that car video is all about,
go check it out on my friend Jesse’s channel.
He works out the math behind it too.
But didn’t that car just stop?
Yeah, because there’s this pesky thing on Earth called friction.
Without the friction, it would have just gone on forever.
The point I’m trying to make here is that inertia is not a force.
I repeat, inertia is not a force!
When you take all the forces away, inertia is what remains.
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