But it’s kind of fluid… your brain only identifies ‘Up’ relatively to how you know gravity works. And yes, the image on your retina is projected upside, but as it’s always been this way, your brain has wired itself up so everything is correct.
On the international space station all the directions are correct, so new astronauts get really confused + lost, until their brains catch up & start thinking in full 3D!
People have also done experiments where they’ve given people glasses with mirrors in them to invert everything. Even after a short while, your brains adapt and start understanding how to deal with it!
A similar question, is why when you look in a mirror is Left-Right reversed, but not Up-Down? Even when you tilt your head?
Yes, exactly what Jarvist said! Our brains are amazing and can adapt to a lot. Your eyes just detect light but your brain processes all the information super super fast and sorts it out so that it makes sense. You can trick your brain, like the experiment Jarvist mentioned where people were given glasses to wear with mirrors that flipped everything round, after a while when they realised that they had to move in the same different direction everytime, the brain started processing it differently so that they could function normally.
You can do a quick trial of how your brain processes vision yourself – there are lots of optical illusions out there to try, see if your brain finds the tricks in there yourself! Here’s a quick one to get you started:
“Acocdrnig to an elgnsih unviesitry sutdy the oredr of letetrs in a wrod dosen’t mttaer, the olny thnig thta’s iopmrantt is that the frsit and lsat ltteer of eevry word is in the crcreot ptoision. The rset can be jmbueld and one is stlil able to raed the txet wiohtut dclftfuiiy.”
Even though the letters are jumbled, you can still read and understand it, right? But make sure you DO NOT do the trick above in class, especially English lessons, I’m sure your teachers will not think that it is a valid neuroscience experiment!