distorted. The pixels you are watching have been

time displaced. They've been mapped onto a gradient

and the darker the region they're mapped to, the further behind

they lag. The effect is really fun but it's certainly

not realistic. Or is it?

Many, many popular digital cameras suffer from lag induced distortion,

like what you just saw, though much,

much more subtle. Usually completely

unnoticeable. It's called a rolling shutter.

Instead of snapping a full exposure at once

they quickly scan strips of each frame. It's

usually undetectable. But when the subject changes faster than the camera

scans,

you get the famous geloey wobbly rolling shutter effect. Really fast

things, like vibrating guitar strings and airplane propellers,

are famous victims, but people can be too. Luke Mandel submitted this photo

to Boing Boing[.net]. His camera scans left to right and, in this instance,

managed to capture a blink, eyes closed

when the scan began and then open in the reflection scanned a fraction

of a second later. But the rolling shutter effect

is not just a neat curiosity. It represents

a fundamental and inescapable distortion that

affects everything we see. Rolling shutter

or not. First things first, let's talk about distortions.

A hallucination is a distortion of reality

when there is no apparent stimulus. If you are merely

misinterpreting an actual stimulus, that is an illusion.

But some distortions occur before our sense organs

and minds get in the way. They are called

optical phenomena. They are not the result of sensation or perception gone wrong.

Instead, optical phenomena are distortions caused by the mere properties of light

and matter

in and of themselves. If you look up at the sky

and see a giant vivid drinking gourd,

you are hallucinating. But if you see a flat

two-dimensional connect-the-dots Big Dipper, you are seeing

an illusion. It's an illusion because those dots merely

appear to be on the same plain, like holes poked in the dark roof of the sky.

In reality, those dots are stars

lightyears apart from one another in three dimensions.

As Celestron's brilliant free real-time 3D visualization of space

shows, from different perspectives, besides our own,

they look a lot less like a dipper or plough.

In fact, all constellations and asterisms

are geocentric illusions. From a wider perspective

their outlines point inward,

to the single lowly point in space

that gave them their names. But you can't blame us.

I mean, Earth is the only perspective any human has ever had.

And even Voyager 1, the most distant man-made object,

is still not even close to being far enough away for the constellations to look

even remotely different than they do here on Earth.

It's also not our fault, our eyes' and brains'

fault, that distant, distant stars weren't included

in our early cosmic connect-the-dot game.

Sure, our eyesight could be better,

but optical phenomena are also to blame.

If it weren't for red shifting and the inverse square law and light extinction,

distant things could be seen in all their glory.

The night sky would look phenomenal. Many structures

up there are huge. They're just

too dim for their hugeness to be appreciated.

When we see Hubble Telescope images of distant objects, like the Helix Nebula,

it's easy to think that, without a telescope to zoom in,

the object must just be a tiny point in the sky.

But in reality, even though the Helix Nebula is

700 light years away, it's

3 lightyears across. If we could make the Helix Nebula

less dim, if our eyes could take a

really long exposure of it, we would see the Helix Nebula

as it really is - nearly 70% the apparent diameter

of our Moon. This is a serious picture. That is how large

the Helix Nebula would appear in the night sky from Earth

if it just wasn't so dim. Our Moon is

tiny in the sky, by the way. It's easy to think of the moon as this huge

baseball-sized thing up there in the sky, but that's an illusion.

Try this the next time you see the Moon. Grab a sheet of notebook paper

and you will notice that the angular diameter of the Moon

is the same size as a hole punched in a sheet of notebook paper held

in arms-length away. Seriously, try it sometime. It shows just how

cute and tiny our little moon is. The Orion Nebula

would appear even larger, if we saw all of its light.

And the Andromeda Galaxy? Just

a smudge in the sky to our eyes. But if our eyes were better at collecting

dim light, we would see Andromeda's true extent

in our sky. Of course, our

night sky doesn't look like that. Distant objects

are dimmer, that's a bummer. But light still wins when it comes to speed.

Light travels at the fastest speed. In fact, in a vacuum, light travels

300,000 kilometres a second.

That's fast.

But not really. I mean, not compared to how far apart

things are in the universe. Sydney, Australia

is 1/14th of a light second away from London.

But the Andromeda Galaxy is

2,500,000 light years away from London.

To put that in perspective let's take a light speed journey from London

to Sydney. It would look like this... Ready?

Three, two, one, go!

Nice! Alright, alright. Here's the Andromeda Galaxy.

Okay, now, relativistic effects aside, let's take a look at what it would look

like to travel toward the Andromeda Galaxy

at the speed of light. Are you ready? Alright.

Three, two, one, go!

Yeah. I mean, seriously, it's

pretty lame. Even at the speed of light,

the fastest speed possible, a year from now

we won't even be a millionth of the way there.

That's how far away

Andromeda is. It's almost sad

in a way. But this brings us back to the rolling shutter effect.

The Andromeda Galaxy is huge. It's more than a hundred thousand light years across

and our view of it is tilted.

Which means that, on the plain we view it in, light from the back

represents what Andromeda looked like thousands and thousands of years before

what light from the front represents.

Changes in its appearance reach us sooner from the front

than from the back. Andromeda is rotating, spinning at hundreds of kilometers per

second in some places.

Now, a lag between light coming from near

and far points on a spinning object, results

in a skewed image. The rolling shutter effect on a cosmic scale

applied to, say, a chessboard, seeing the front

ahead of the back is pretty trippy and dramatic.

So, does that mean we see

wobbly, funhouse mirror, rolling shutter effect versions of Andromeda

and other distant galaxies? Well, technically

yeah, but the distortion is negligible. It may as well be

ignored. Why? Well,

the speeds used in these visualizations are not

to scale. On average, yes, matter within galaxies

orbits the galactic center at hundreds of kilometers per second

but galaxies are so huge it takes them

hundreds of millions of years to complete just one

rotation. In other words, the lag between light

reaching you from near and far points on a galaxy,

is nothing compared to how much time it takes

matter in the galaxy to travel that same distance.

In the case of Andromeda, if you insisted

on seeing Andromeda as it really is,

that is, corrected for any lag caused by the fact that the speed of light is

finite, the most extreme points on the Galaxy

would only need to be adjusted by about a 10,000th of

the width of any image. In this case, less than a pixel.

So, it's not a big deal. But it's not a nothing deal.

It's real. In fact, everything we look at is,

in some way, distorted by the fact that the speed of light

is finite. Your own feet are about

5 to 6 light nano seconds away from your eyes, which means when you look at your feet

you are seeing where they were 5 to 6

nano seconds ago. 5 to 6 nanoseconds in the past.

Of course, a delay that brief is pretty much undetectable

but it is calculate-able. If it makes you feel

a little sad to know that even with the sharpest mind

or the best instruments, appearances still depend on

where you are. That optical phenomena insure

appearances are always relative(?) Don't feel bad.

We call the people closest to us our relatives.

We're really just a family, a big family

of reference frames that, like a family, don't always agree

but do have plenty of cool things to look at.

I'd like to thank my editor, Guy, for help with the

rolling shutter effect in this video.

And I'd like to thank you, because, as always

thanks for watching.

Oh, here's something cool.

I will be at YouTube Fan Fest with HP

in India very very soon. Check the description for more info. If you can

make it,

I hope to see you there.