Monday, June 22, 2009

Corrections (Yours)

Every once in a while, I get a vague sense of unease when I use a link, usually because something seems just a little "off." That was the case when I used the "visual perception" link last week, mostly because the author seemed like a bit of a breathless self-promotor.

Well, chalk one up for the spidey sense. From Phil B:
I'm a vision scientist, and I'd like to point out that the thing is almost entirely factually incorrect.

I could pick it apart, but the best proof comes if you simply close one eye. That completely removes all information that could be gleaned from your eyes being separated in your head (called 'stereopsis'). Everything looks the same size, no? This is because stereopsis is one small part of what we use to judge depth. Cues that come from just one eye, for example, how much space the image occupies on your retina, are the main cues used to perceive depth. It is true that things that are perceived as further away do feel like they must be bigger, but our brains sum up the information from all those other cues of perceived depth so that how apart a person's eyes are has very little impact on how far away things look and hence how big they look.

Phil should write his own articles, because that was an extremely clear explanation.

Also, from Brendon Dusel, in reference to the article about the first man in space:
Just a correction, despite that local news station's story to the contrary, he was not the first man in space by most definitions. According to the wikipedia article, he jumped out approximately 18.32 miles above the earth. The international definition of space is 62 miles, while the US designates an astronaut any human that travels over 50 miles above sea level. Interestingly, some fighter pilots have earned this distinction:x-15 Wikipedia link.

Still the highest ever skydive, though, and a heckuva jump.

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