To give Allancw (Allan Weisbecker) all the credit he is due
, I do think there is a common problem when people who have little imagination, and little ability to think beyond their narrow, limited experience here on Earth, try to imagine what being on the lunar surface would be like.
As earth-bound critters, we are used to *always* seeing blue (or grey) skies in daytime (and no stars), and then dark skies at night. And of course we are also used to *only* seeing stars after dusk, when the sky is dark or at least dark
ening.
Cloud cover permitting, of course..So, a
simplistic response - lacking in any thought whatsoever - is to ignorantly believe that a black sky without clouds must mean you will see stars.
There are two things that might help the person who just doesn't 'get it'... (are you listening, Allan Weisbecker?). The first is to somehow develop an imagination and the ability to think laterally -
in a way that isn't biased towards a particular desired outcome - and to put in a little work to properly research the topic, perhaps run a few simple experiments, and to think
all the issues through
carefully.
The second thing that helps many of us understand
immediately, is simple - an interest (and a little experience) in night photography...
You see, Allan, if you had done any night time photography (I mean beyond relying on Auto settings..), then you would know that to get stars to appear in any image, you need to have a long exposure/open aperture. You would also know that the exposure time would typically be at least a few seconds or more (given a reasonable aperture setting and using ISO 100 film or sensitivity setting).
Nothing like that which is used for daytime/sunlit scenes.
From that very simple observation, you would realise that those exposure settings *tell* you that these are very, very faint objects.
How faint? Well, starlight is generally less than 0.002 Lux. (Yes, I know that isn't an exact figure for how bright a single star might be, but I'm trying to keep this simple for simple minds....) To put that into context, here's what some other light levels are:
0.3–1.0 lux - moonlight
50-80 lux - typical well-lit room
100-300 lux - heavily overcast day
320–500 lux - typical office lighting
400-500 lux - dawn/dusk just before/after sun is visible
1,000 lux - typical overcast day
1,500 lux - sports stadium (strongly lit for televised sports)
10,000–25,000 lux - daylight (indirect sunlight)
30,000–130,000 lux - daylight (direct sunlight)
(from memory and verifiable from various sources including Wiki)Now
at any given time our eye can manage to see a ratio of about 100:1 between the brightest and darkest objects in its field of view (fov). There is some debate over the actual range and some claim up to 1,000:1, so let's accept that highest figure.
You can check this against the numbers above, and you will see it is being pretty generous - I defy anyone to be inside a brightly lit office and look out of a window (no going up to the window and shielding your eyes!) onto a scene lit only by moonlight and see details (or stars, for that matter..). Good luck with that.... Certainly, it is absolutely clear that there is no way whatsoever that an eye that is exposed to daylight, can possibly resolve a star - that is a ratio of many
millions to 1, not thousands, even using the most conservative figures.
Now, the eye *can*, if given time, adapt itself so that the range is effectively shifted up or down. So at night, you eye slowly adapts to the dim light.. But of course if you are then exposed to very bright light, even if it is in your peripheral vision, the eye has to shift back into 'bright' mode and the dim stuff will vanish.
So.. and this part is ONLY for those with imagination and lateral thinking and the ability to follow logic... what was the situation on the Moon?Bright sun in the sky (just a tad brighter than here on Earth as no atmosphere to scatter some of it..) - 130,000 Lux...
The entire ground, from horizon to horizon, 180 degrees, brightly sunlit. - 30,000 Lux
The LM, the other astronaut, and any hills/mountains, all brightly sunlit. - 30,000 Lux
The astronaut's own arms and hands, and the inner edges of his helmet, all brightly sunlit. - 30,000 Lux
Scattered light from the dust and scratches and refelections and refractions of the visor. - difficult to guess at..
And then, up in the sky, lots of stars, but all down near
0.002 lux.
Now IF an astronaut was as ignorant as the OP, and thought that it would be worthwhile to try some star viewing (for Deity knows what reason), they would have to:
- find some deeply shadowed area
- in a bulky and pretty rigid spacesuit, bend his back and tilt his helmet upwards, well away from the Sun and from *anything* that might throw any indirect light at his eyes
- wait for about a minute before he would have any hope of seeing *any* stars
- or wait for about 7-10 minutes before he would be able to perceive a decent starfield..
Now by doing all that, he might (after the ten minutes), begin to see something approaching what he might see
from any country location on Earth. How much would that ten minutes cost, and why would he bother?
And then he would have to look down to the scene he was *supposed* to be working in, on a very tightly controlled schedule, and where everything is brightly sunlit. He would be dazzled for several seconds, running the risk of a fall.
(Is it any wonder that Allan isn't in the space program in an advisory role?)What should embarrass Allan Weisbecker is his astonishing lack of imagination, his lack of ability to think about what that environment was really like. Did he somehow forget that it is an alien environment? Does he honestly believe that dark sky equals seeing stars, with no need to consider the issues properly?
When was the last time that any of us ever stood on a landscape that stretched from horizon to horizon and was all brightly lit by the Sun, and yet when we glance up at the sky away from that Sun we see it is not light blue, but black? I, and I suspect most of the others who read this forum can indeed imagine/visualise what that might be like. But some folks (Hi, Allan) just cannot conceive what that would be like, nor can they be bothered to actually think about the logistics of trying (stupidly) to get a better view of the stars than even a casual glance upwards on a moonless night on Earth would give. Some folks cannot conceive of the cost of such an exercise, in terms of time and the risk as their eyes re-adapted to the sunlit scene.
Some folks just want to support their own (daft) conspiracy agenda, right Allan?
PS - A note for purists: yes, I've taken some liberties by mixing light levels with light outputs - if you can come up with a better way without this becoming incredibly complex, please have at it!