[thedoc (OP)]

Chris Markley asked the Naked Scientists:

Hello Naked Scientists,

When I lay down, my feet appear farther away from me compared to when I am standing up.  I wear contacts during the day and glasses during the evening.  Could this be a product of my corrective eyewear or a manifestation of my brain due to different visual reference points? 

Thank you.

Chris Markley

[thedoc (OP)]

We posed this question to Dr Rebecca Lawson from the University of Liverpool...

It seems unlikely that any effects of glasses or lenses would differ depending on whether you are standing or lying down.  We do seem to overestimate vertical distances particularly if we’re on top of a cliff looking down it.  We overestimate and think that the height of the cliff is greater than if we were at the base of the same cliff looking upwards and in fact, agoraphobics seem particularly prone to this overestimation.  However, this effect goes in the opposite direction.  So really, I don't have a good account of why Chris’s feet seem further away when he is lying down than standing, but I think that his question really nicely shows of the complexity of human distance estimation.  Perhaps surprisingly, we still don't fully understand how we judge the size and distance of objects.

[RD]

If you are short-sighted everything looks smaller / further-away when wearing glasses ...



[ similar to the perspective distortion seen when using a wide-angle lens in photography ]

[Geezer]

I was thinking it's the same as the optical illusion that makes the Moon look a lot bigger when it's close to the horizon, except that it seems to be the other way around!

[MikeS]

Quote
"When I lay down, my feet appear farther away from me compared to when I am standing up."

Without gravity compressing your spine your feet are further away from you when laying down but probably not enough to see the difference.

[RD]

I was thinking it's the same as the optical illusion that makes the Moon look a lot bigger when it's close to the horizon, except that it seems to be the other way around!

That could be the answer, depending on how busy the carpet is ...

In the case of the Moon illusion, objects in the vicinity of the horizon moon (that is, objects on or near the horizon) exhibit a fine detail that makes the Moon appear larger, while the zenith moon is surrounded by large expanses of empty sky that make it appear smaller.

https://en.wikipedia.org/wiki/Moon_illusion#Relative_size_hypothesis


Or alternatively an optical illusion caused by striped pyjamas   []