Name: You Are Not Where You Think You Are
Uploaded: 2022-04-08T23:36:01.000Z
Duration: 9 min 55 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Look around you. Where are you? Where is this  place you are occupying? Somewhere in a room,  

maybe in a city on a continent on a planet  orbiting a star in a galaxy among billions.  

Modal verbs - B1

But… where is all of that? While  this may feel like a daft question,  

it turns out that the concept of an absolute  position is something humans made up.

In a nutshell, the universe is a big  bag of space that has things in it.  

If someone removed all these things, the  stars and planets and black holes and dust,  

there would just be empty space left.  In empty space, the concept of having  

a position loses all meaning. Empty  space is uniform, the same everywhere.

The space we occupy is not like a stage under  our feet. We can't mark specific points,  

or staple something to spacetime as an  anchor. Without things there is no position.  

We are really ever only at a position  in relation to something else.  

Which also means that things we take for granted,  like up and down are actually relative too.

Ok, let us fill the universe up with things again  

and try to find out where you are,  right now. Relative to everything else.

Let us start this video at a familiar place  and then get increasingly weird. From your  

perspective the world is seemingly flat and you  can move in 3 dimensions. It's what physicists  

call a 'frame of reference' - the perspective  you have of the universe and how you see things  

moving around you. Where your up and down  is. Your frame of reference is correct.  

For you – but not for the rest of the universe.

Around 5 kilometers from you, where the horizon  begins, the ground noticeably curves away from  

you. If you could see through the ground,  you'd see people from below or sideways.  

But they don't fall 'down' off the planet  because gravity doesn't actually pull them down.  

'Down' is an illusion of your reference frame. To  earth's reference frame, gravity just pulls in.

But for humans there is an up and down because  within our frame of reference that just makes  

sense. Which is also why we think that the planet  itself has an up and down, north and south. And  

we made our maps accordingly. But an observer  looking at the solar system might disagree.  

Our maps make sense to us because we are  used to them, not because they are correct.

Ok. So this is step one – your position  on what feels like a flat surface but  

is actually a sphere. But this sphere is  always moving, never staying in one position.  

Earth is orbiting a star, the sun  at the center of the solar system.

While we usually imagine this as pretty orderly,  

someone looking at us from the outside  would see something pretty messy.  

To see this more clearly we'll exaggerate  all these movements, this is not to scale.

First of all, our orbit really is an ellipse,  so we spend half the year sinking a little  

bit closer to the sun speeding up, and half  the year rising up a bit and slowing down.  

And the ellipsis itself changes  its shape every 100,000 years too.

And in another cycle of 112,000 years, the  ellipse itself is drifting – which at least  

creates a beautiful shape. In the end, we  get an orbital path that looks like a wobbly  

circle with wavy edges. And it gets worse, as  the moon now starts to screw things up too.

As the moon is a pretty massive thing, it pulls on  earth. Both objects orbit their common center of  

gravity, that lies around 4700 km off to the  side of Earth's core. In practice this means  

that as the moon orbits earth, it is jerking  earth around a bit, enough to make it jiggle.

Ok so you are standing on the  surface of a rotating planet,  

that is jiggling around the sun in an  elliptical orbit that changes a bit every year.

But who's to say the earth is right? From  

the perspective of the sun the plane  of the solar system is arbitrary,  

it's defined as the plane the earth orbits in  because that is convenient for us. In reality  

the other planets are just a little  bit inclined with respect to our plane.  

From their point of view, we're the  ones with a slightly bent orbit.

But this is not it – far from it! The solar system  as a whole is orbiting the center of the milky  

way galaxy. If we look at the milky way, we can  clearly make out a galactic plane in which the  

solar system orbits the center every 230 million  years. But of course it is not that simple.

First of all, the plane of the solar system  is not aligned with the plane of the galaxy.  

Nothing really is – just like the planets in the  solar system orbit the sun on their own planes, so  

do all the stars orbiting the galactic center. The  solar system as a whole is tilted about 60 degrees  

towards the galactic plane, speeding through  space at almost a million kilometers per hour.

Someone in the center of the galaxy would see  the orbits of the planets moving through space  

in a helix shape, which you can  imagine as a corkscrew motion,  

on the tilted plane of the solar system,  relative to the plane of the galaxy.

This orientation in space means that sometimes the  

planets are sort of in front of the sun  as it orbits around the galactic core.  

Let us just look at this for a moment  – there is a strange and eerie beauty  

abouthow our planets and the sun move through  space. Do you feel a bit dizzy? It gets worse.

This is still not the whole story because the  mass of the galactic disk is constantly pulling on  

the solar system too. Like a drunk dolphin, we're  diving down and shooting up hundreds of lightyears  

through the galactic plane, ten times every  orbit, along arcs thousands of light years long.  

We haven't mapped this motion out  completely, as it takes the solar  

system tens of millions of years to go up and  back once; and, well, humanity is not that old.

Let's look at your relative  position again. On a planet,  

tilted towards the sun, jiggled around by  the moon. In a solar system tilted towards  

the galactic plane, moving forward in a helical  shape, diving up and down through the plane.

Hm. But where is “up” in a galaxy? At this point  the frame of reference becomes a bit arbitrary  

and pointless because of the nature of the  universe at this scale. The Milky way is  

part of a galaxy group that appears to be part of  greater structures like the Laniakea Supercluster,  

which itself is part of the gigantic Pisces–Cetus  Supercluster Complex and finally a galactic  

filament that spans hundreds of millions of  lightyears in all directions and orientations.

Someone looking right at us from that far  away will only see the End of Greatness.  

All stuff appears homogeneous, the same  everywhere. Just like with empty space,  

when everything looks the same, who's to say  anyone's view is better than anyone else's?

We have reached the end of our  little exercise in cosmic humility.  

Let us make the journey backwards again. From  the indescribably large, to the really large,  

to our galactic home, to our galaxy, to the solar  system diving up and down through the milky way,  

to the jiggle of existence. And finally,  back to you, right now, watching this video.

If this is all a bit much, don't feel bad.  The scale of the universe is brain crushing  

and trying to keep track of how everything is  oriented or decide where the best up and down is,  

is hard. But it doesn't really matter.  Because it doesn't change where you are.  

You're already in the best spot you could possibly  be – right here, right now. For all you care  

nothing can stop you from being right at  the center of your own little universe.

Perspective really is everything. That is true  for the universe we all inhabit, but even more  

so within your personal universe. The way your  life will unfold also depends on what you consider  

possible. Take us at Kurzgesagt: our passion is  to spark curiosity for science and make videos for  

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And we are doing this with Shopify, who  also were so kind as to sponsor this  

video – which delighted us because we have  been using their platform for years now.  

Shopify is an e-commerce platform that  allows you to start and grow your business.  

And by starting a business, we really do mean  from scratch: if you want to sell your handmade  

ceramic mugs out of your bedroom today, you can.  But not just that – if you want to scale your  

one-man show to a sizeable team, then Shopify  has the tools to support you on your journey.  

Now you just have to get started: go to  shopify.com/kurzgesagt to get a free 14 day trial.