Dear Prof: Your Letters
Dear Prof,
I see that conceptual artist Carsten Holler (the man who put slides in the Tate) has a new project on. 24 volunteers will be given goggles that invert their vision to wear for eight days. The idea is that they'll see the world upside down.
At the end of the time they will take their goggles off in front of an audience at the Manchester International Arts Festival in July. I got this from the London Metro, which says "Their sight is expected to return to normal shortly after."
I seem to remember from GSCE physics that if you hold prisms in front of your eyes (inverting your vision) that within a matter of hours the brain will compensate and flip your vision the right way up. If that's true then within a few hours of putting the goggles on the volunteers will actually begin to experience normal vision again. Then on the eighth day, when they take them off they will see things upside down again for a few hours before, once again, the brain compensates and turns it back to normal.
Is this true? And if it is doesn't that kind of ruin his experiment? He should have the people at the show in Manchester put goggles on until their brain flips things the rightway up and then have them take them off again, putting things upside down (for a while). It's making my head spin, please help!
Alistair Spalding, The Real Word
Your Say:
Hmmm... this smells like biology, not physics, to me. Physics says if the image formed on the retina is naturally upside down these goggles would turn it the "right" way up. Whether the brain then compensates I don't know I'm afraid, but I did find out that if you cut out a salamander's eye then re-implant it the wrong way up then its brain doesn't compensate. I don't know if that helps but it appealed to my sense of the macabre.
Anne Pawsey, Null's resident physics boffin
This is a tough one, since vision isn't completely understood. I've heard reports about this type of thing before.
The goggles essentially remove the necessity for the brain to flip images - they do the job instead.
New born babies apparently see everything upside down for the first few days, since they aren't use to vision.
As for why the brain flips the images in the first place: it's easier to coordinate oneself in a world that isn't upside down.
Gavin Hammond, eel expert extraordinaire
When the subjects of Carsten Holler’s experiment put on their flipping glasses they will indeed start to see things the right way up, but not after a couple of hours.
Experiments with this effect show that the brain can take several days to work out that it has been tricked; how quickly it reacts depends on how much of a helping hand it gets from the other senses. The body associates up and down with gravity so the more cues that reinforce the idea of falling or hanging or swinging, the faster the brain will compensate. Humans are also willing to practice so they can speed up the process.
A similar test with chickens wearing suitably smaller glasses that reversed left and right, showed that the chickens never really got the hang of it. They weren’t willing to challenge their observations and match up what they saw with what they knew to be there. The chickens were luckier than the cats that tried the experiment who, presumably due to their built-in lack of co-operation, refused to wear the glasses. They had one eye surgically rotated by 180 degrees for several months.
When the glasses are removed at the end of the experiment (I’m back to Carsten Holler now) the vision will return in a couple of hours. This is probably because the brain remembers all of the cues it has had since birth and rapidly undoes the flipping: it has its own “ctrl – z” if you like.
Mike Leeson, physics guru
And here's a helpful video demonstrating Mike's chicken experiment.
Can you help Alistair?
See answer's from the Null community below. If you think you may have an answer for Alistair, please email [email protected] The Prof is currently huddled in a corner, quivering at the very thought GCSE physics.
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