Hey, Vsauce. Michael here. But you are
actually right there. Well, at least
the camera is. Mirrors are amazing.
In fact, the word "mirror" comes from Latin "mirari",
meaning "to wonder at, to admire."
It's also where we get the word miracle. Mirror-
-acle. Like when mirrors face each other and transform a toilet room
into infinity. I love this kind of stuff.
But what if instead of a rectangular prism,
the room was a sphere, mirrored
all the way around? What would it look like?
What would you see floating around in such a room? The first question we should
ask involves
the light source. If you were in this room using a flashlight and you turned the
flashlight off,
would the light keep bouncing around off of the mirrored walls,
illuminating the room until your body absorbed all of it?
Or if you left the flashlight on, would light continue
bouncing around, building up, getting brighter and brighter until you lost
your vision and cooked?
Probably not. Every time light
hits a mirror and reflects off, a tiny tiny amount
is absorbed. Even if your mirror spherical room was the size of a
giant stadium and its walls reflected
99.99% of light
on each reflection, light speed is just too fast,
meaning that the reflections will happen rapidly, a little bit of light being lost
each time.
The room will go dark in a fraction of a fraction of a second. To you and me,
it would seem instantaneous. As for what it would look like,
let's pretend you begin with your face up against a wall of
the sphere and float backward toward and past the centre.
At first, you would see your face quite clearly.
The surrounding reflections would be very distorted. As you moved away,
at a certain point your face would cease to shrink away in appear smaller
in mirror and instead would grow larger and become magnified
until you reach the center at which point your face would fill
your field of view. As you continued on past the center, your image would flip
upside down and continue receding away.
It would look a bit like this. But don't get too enamoured
with your reflection because mirrors don't show you
as you really are.
Have you ever wondered why you liked the way you look in a
mirror but don't like how you look in photographs or
video? It might be because of the
mere-exposure effect. You prefer what you are used to
and most mirrors you look into don't show
the real you, the you that other people in cameras
see. Instead, a mirror shows you a reversed
version of yourself and you've become more comfortable with that version
of you. A version of you that is flipped left to right.
Mirrors reverse along axes perpendicular to their surfaces,
like left and right. They don't also flip things upside down, they don't also
reverse up and down because those directions
are parallel to the surface of the mirror. When it comes to the way you and
other people look,
the difference can be startling. NPR pointed out that Abraham Lincoln
looked like
this. Mirrored he would have looked like
this. Now to us, something seems noticeably strange about it but it is
the Lincoln
Lincoln would have preferred. It's what he saw every day
in the mirror. But here's something really cool.
You can take a flexible mirror and
unreverse its image by folding the mirror
into a cylindrical shape. Take a look at this.
Here I am with a reflective material and there
is the camera with some text taped underneath, as you can see everything is
flipped left to right. But as I fold the sheet into a cylindrical shape
the image separates, revealing an unreversed
version. It becomes a true mirror.
Finally, here is one last piece
of every day mirror trickery. When you look into a mirror,
how big is your reflection, your image
on the surface of the mirror to you? Surely,
it depends on how far away you are from the mirror. But it doesn't.
When you look into a mirror your reflection on the surface of that mirror
is
always the exact same size. In fact, it is always
about half of your actual size. This is because
when light reflects off a mirror, it comes in
and reflects back out at the same angle, which means that
in order to reach your eyes at the top of your body,
light from your feet at the bottom must hit the mirror
halfway between the two. The triangles you form
with a mirror are similar, regardless of
where you stand. You can demonstrate this effect by
outlining the size of your own head as it appears on the surface of a mirror
using a bar of soap. Now, because you aren't here
let's pretend that this phone is your head and its camera
is your eye. We begin up close. The camera looks
really big from this perspective. Let me just
carefully trace around the outside, so we can compare later.
Good, good, good. Okay. Now, I'm going to pull away from the mirror. Clearly
the phone is smaller, right? Well,
if I reach out and once again carefully trace the edges.
There we go. I will find that I have drawn a
rectangle that is the exact same size.
Your image on the surface of a mirror
from your own perspective is always the same size, whether you are a few
centimeters away from the mirror
or a few kilometres away. Your image on the surface of a mirror in fact is
always half your actual size.
Okay, enough about light returning to our eyes. What about light
that never returns?
Could we use a telescope to resolve individual
aliens on a planet light years away? Well, over on Vsauce3,
Jake investigates this question with Star Wars.
And my friend Rusty investigates the potential for Star Wars
becoming real in his episode of Science Friction. And
Vsauce2 has a brand new lüt all about cool
Star Wars stuff. Check them all out.
And as always,
thanks for watching.