Re: Could a human walk on Titan's surface?

From: Chris L Peterson (clp_at_alumni.caltech.edu)
Date: 01/20/05 

Date: Thu, 20 Jan 2005 22:20:23 GMT

On 20 Jan 2005 13:25:02 -0800, "Axel" <ritesh_laud@hotmail.com> wrote:

>> Saturn, and therefore Titan, are about 10 astronomical units away
>from the Sun. They
>> therefore get about 1 percent of the light that the Earth does.
>
>I've often wondered how a very small percentage of broad daylight (like
>1%) could still be some thousands of times brighter than a night
>illuminated by a full Moon. Just today it occurred to me that the
>constriction of our pupils in daylight gives us a very false sense of
>how bright the day really is. We've all experienced walking out of the
>eye doctor's office after having our pupils dilated. That's how bright
>the sun really is, *painfully bright*.
>
>Out on Titan, our pupils would simply dilate appropriately in that
>dimmer "daylight" to let us see better. They would probably still not
>dilate to the full 6-7 mm that they do at night; if they did, even the
>relatively small amount of sunlight at that distance could be painful!
>Cheers,
>Ritesh

Most of our ability to deal with varying brightness comes from the retina, not
the pupil. In most people, the full range of pupil size only accommodates a
factor of about 10 in brightness- not even 3 magnitudes. People with problems
that cause permanently dilated pupils actually don't have any major problems
with full sunlight.

BTW, the numbers Brian is talking about are absolute- that is, he isn't talking
about perceived brightness, but actual brightness as it would be measured with a
light meter.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

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