Sun from space.

Main Question or Discussion Point

Hey! Some time ago i saw this video:

And, although i'm a comp sci guy and did studied physics on the first two years, i could say i have almost none knowledge of physics, i mean, real knowledge, not just how to make my guy jump on a 3D game. I wonder if this guy is just wrong or, possible, actively lying? All i can think points to the fact that i would see(the sun) as a very bright white and then go blind. I decide to send this, and sound stupid, because after i stumble on this one, i learned that there is a lot of people out there saying such a thing about light(some of them people with master degree) and about what we could see, etc... So, besides the fact he is wrong, in my mind, is he really all 100% wrong ?

Marcos Amaro.

Last edited by a moderator:

Related Other Physics Topics News on Phys.org
russ_watters
Mentor
Welcome to PF!

You're right, he's wrong. About pretty much everything he says. If it weren't so mean, I'd suggest to him that he point the laser into his eye and then re-state his claim. I'm not sure if he qualifies as a liar/crackpot or what, but if he does we'll delete the link to avoid giving him free advertising.

Khashishi
The last 5 seconds or so, he says, "I don't care if anyone believes me; I'm just a crackpot." and laughs. I sort of think this is some elaborate joke.

I don't get what the person in the clip is ranting about - it's messed up. By his logic, light from matches and lightbulbs would not be directly visible :uhh:. And if he pointed that laser pointer to his own eyes, he would see it. And he also seems to propose that light from stars are not visible in outer space :uhh:.

(I saw russ_watters had already replied while I was looking for NASA pictures.)

The Sun appears as white; The Space Shuttle Endeavour's robotic arm hovers over Earth's horizon, with the Sun in the background (NASA):

EDIT: NASA image link & description: http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001097.html
"View of the Remote Manipulator System (RMS) end effector over an Earth limb with a solar starburst pattern behind it."

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-001097.jpg

Last edited:
There does often appear to be a lack of stars in images from space which also include the Earth, moon, Shuttle, ISS etc. Like in your photo above DennisN.

Do you believe that this is a relative intensity phenomenon?

There does often appear to be a lack of stars in images from space which also include the Earth, moon, Shuttle, ISS etc. Like in your photo above DennisN.

Do you believe that this is a relative intensity phenomenon?
I guess it's because of camera exposure reasons. I am searching for more good pictures regarding this (and I'm also trying to find the original NASA link to the picture above). I also know there are people on this forum who knows more about space photography than me .

Last edited:
Drakkith
Staff Emeritus
There does often appear to be a lack of stars in images from space which also include the Earth, moon, Shuttle, ISS etc. Like in your photo above DennisN.

Do you believe that this is a relative intensity phenomenon?
Taking a picture of something in space that is lit by the Sun is like taking a picture of your car at noon in summer. It's REALLY bright. So bright that:

1. The exposure is very short. So short that light from the stars would almost be buried in the inherent noise from the sensor, even if you just pointed it at deep space.

2. The addition of very bright objects throws light all over the picture because of diffraction, aberrations, reflections in lens elements, and a plethora of other reasons. This all adds up to increase the background noise even more, further burying what little starlight there was in the first place. Just look at those spikes in the above picture! Not to mention the "cloud" of light around the Sun. It falls off as you get further away from the Sun, but it doesn't just stop.

Every light sensor has a "dynamic range". That range is the ratio of intensity (or brightness) of the brightest and the dimmest picture element it can capture at the same time. The very best DSLR cameras have the dynamic range at about 15 "f-stops", which means the ratio is 2 to power 15, or about 30 thousand.

The Sun's apparent magnitude is -26.74; and the brightest star visible from the Earth is Sirius, at -1.46; which means $2.5 \log_{10} r = 26.74 - 1.46 = 25.28$, where $r$ is the ratio of the brightness, giving $r \approx 10^{10}$, which is a lot greater than $2^{15}$.

When the Sun is in the picture, no camera can possibly see any star.

This looks like stars to me (but there's of course no Sun in the picture):

Source 1: http://spaceflight.nasa.gov/gallery/images/station/crew-6/html/iss006e18372.html
Source 2: http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS006&roll=E&frame=18372&QueryResultsFile=1048138731408.tsv

The Aurora Borealis or “northern lights” and the Manicouagan Impact Crater reservoir (foreground) in Quebec, Canada, were featured in this photograph taken by astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, on board the International Space Station (ISS).

And also:

ISS Science Officer Don Pettit said:
You catch an occasional meteor while looking down. You see stars and planets and our galaxy on edge.
Source: http://spaceflight.nasa.gov/station/crew/exp6/spacechronicles9.html

I should also add that even if a camera can capture about 30K brightness ratio, that does not mean it can be seen in that way after capture. Our image displays, such as computer screens or paper photos, have much lesser dynamic ranges, so reproducing images with both bright and faint objects is even more difficult than capturing them.

There does often appear to be a lack of stars in images from space which also include the Earth, moon, Shuttle, ISS etc. Like in your photo above DennisN.

Do you believe that this is a relative intensity phenomenon?
Probably, also, you can't see stars on most/all unmodified smartphone cameras (maybe on some Nokias) I don't know what they have up there but it is probably not too much better with night vision.

Drakkith
Staff Emeritus