I’wondered this for a while.
Why is it every picture or film I see of Appollo or shuttle mission show no stars in space? And on top of that they keep talking about the ‘blackness’ of space. Shoudn’t they’re be stars?
This subject has been covered in this thread.
Basically, if you can see any large bright body (the moon, earth, etc) in the frame, then the stars were simply washed out.
And space is still quite black, even with all those pesky stars.
O.K., I followed up on your reply, good posts, but not the answer I’m after. They all talk about moon’s, earth’s, mars’s, etc., atmosphere’s ‘diming’ stars glow. If that’s the case, then how does the Hubble telescope work?
As I said in the other thread. The Hubble is not in full daylight on the surface of a reflective object 100% of the time. The appollo astronauts were.
There are two questions here. The first one is, I think, why, if there are trillions of suns in all directions, is space black? Logic would dictate that it be LIGHT. Th reason for that is simply because the light from all those stars just hasn’t reached us yet.
The other one, about why no stars appear on shuttle pictures, is that there is too much ambient light and the stars are washed out. You can photograph stars from the shuttle if the earth, sun and moon are not reflecting towars the camera. But most star photos are time-lapse. That doesn’t work from the shuttle because it’s in low orbit.
tcburnett wrote:
The first one is, I think, why, if there are trillions of suns in all directions, is space black? Logic would dictate that it be LIGHT. Th reason for that is simply because the light from all those stars just hasn’t reached us yet.
no, actually this was an ingenious argument against infinite space. if space truly was infinite, with an infinite number of stars, then every point in the night sky should have a star glowing in it, and we would be perpetually bathed in light.
the reason we can’t see all of these stars is probably kind of due to their light not having reached us, but mainly because space is mostly exactly that: empty space. people, do not underestimate the vastness of the universe!
The “space is big” argument doesn’t work, by itself: If space were unbounded, and had matter uniformly distributed through it, at some scale, then you’d still get a bright sky, unless it’s only a finite age. The basic idea is that no matter which way you look, your line of sight will eventually reach a star. I can offer a more mathematical proof, if you’d prefer.
The “bright sky” thing actually has a name - it’s called Olber’s paradox, and if you believe in the big bang, you don’t have a problem with a dark sky.
O.K… Listen, I’ve followed the other peoples posts, they don’t cover the answer!!
My honey and I were watching ‘For All Mankind’ (One Helluva movie) and the astronauts kept talking about the ‘blackness’ of space. Come on, not one star?
My original post remains: with all the abient light around, how the Hell does Hubble work?
Certainly the Apollo astronauts could see stars. I can recall reading in Lost Moon a description of how the stars could be used to obtain an attitude fix, and how the venting gases obstructed that view (forcing the Apollo 13 astronauts to use the Earth as a reference point). Why did they describe the “blackness of space”? Well, when I’m on a mountaintop in the middle of nowhere on a clear night, I can see a few thousand stars and the Milky Way. But I still usually get a feeling of incredible tininess in the incredible darkness. I can only imagine that astronauts tucked into a little capsule a few thousand miles from any particular body would feel the same thing, only to a much greater magnitude. They could see a lot of stars, but they could also see an awful lot of blackness.
Hubble works because it doesn’t point anywhere near one of the bright objects (Earth, Sun, Moon) when taking images of objects far away. The ambient light doesn’t affect it if that light can’t hit its mirror, and there’s nothing to scatter light towards the mirror (unlike, say, a telescope on Earth).
Exactly as the above poster mentioned. Hubble is focused somewhere. Much of the other light is shaded.
Take for example the Huble Deep Field shots. Hubble “looked” at an area of the sky where there seemed to be nothing, but what it saw was thousands, if not millions, of galaxies. The light from those galaxies is so diffused by the time it reaches us that we can’t see it, but Hubble saw tons of galaxies.
I think you’ve been misled. The earth’s atmosphere doesn’t absorb much lvisible light at all. The major problem with doing astronomy from the ground is that the atmosphere bends light in random directions. If you look over a campfire at a distant object, you will see a shimmering effect, because the blobs of air rising from the fire are hotter than the ambient air, and has a different refractive index. The earth’s atmosphere is usually more stable than that, but still there are pockets of warm or cool air which degrades the image. Even with small amateur telescopes, if you magnify a bright star it will look like a very energetic amoeba.
If you go into other wavelengths (infrared, or ultraviolet and above) then the atmosphere absorbs a significant fraction of the radiation. You do need to use satellites or high-altitude balloons for those wavelengths.
Phillbuck: they didn’t. As they passed the darkside of the moon, not one star could be seen.
That’s my question; how does Hubble work?
It’s not a matter of seeing all the stars out there, it’s a question of ‘why can’t you see any?’
AND…the Apollo astronauts never said they saw a star, only ‘blackness’.
Space may be infinite, but matter sure as hell isn’t. The universe is 30 billion light years across - a number based on the assumed age of 15 billion years. That’s big but finite space, containing a finite amount of matter, and therefor the sky can’t be “full of stars”.
The human eye has a limited “dynamic range” - that is, if something bright is in the field of view, you can’t see anything less than, oh, 1/1000 the brighness. Tonight, turn on the lights in your room, open the curtains, and look at the sky through the window. Do you see any stars? Maybe one or two, but probably not. That’s because the brightly lit things in your room and the reflections off the window are blinding you. The same thing happens to astronauts - the interior of the spaceship is usually well lit, and outside, they often see the earth or moon lit by sunlight, if not the full brightness of the sun itself. But if they turned off the cabin lights, and if the window was facing away from the sun, moon AND earth, they should see a lot of stars. I’m sure they did.
Now, in your room, if you opened the window, you will get rid of a lot of scattered light. Then you may wrap your head in a long tube pointed at the sky, so that your room lights don’t reach your eyes. Now you should see a lot of stars, because you are no longer blinded by stray light. The Hubble works the same way. It is a long tube. It is carefully controlled to make sure it doesn’t point anywhere near the sun. And it doesn’t have a window. It has a mirror, but that’s at the bottom of the tube so no stray light reaches it.
I’m assuming that you meant ambient light there.
In space, there is no ambient light, because there is no ambient air.
Light pollution is a major problem on the earth, because it degrades the star images. It’s basically a problem of outdoor lighting which is reflected by the atmosphere back to the ground.
The Hubble has problems pointing close to bright objects, like the sun, but otherwise there is no ambient light to interfer.
Sounds like scr4 explained pretty well why they might not have seen stars at any given time.
Well, a few quotes from Andrew Chaikin’s A Man on the Moon: The Voyages of the Apollo Astronauts (from which, I believe, HBO’s From the Earth to the Moon was derived):
On entering the shadow after Loss of Signal during the Apollo 8 mission:
“The men were running through the checklist for the burn when suddenly the spacecraft was enveloped by darkness. Anders realized they were deep in the shadow of the moon. As his eyes adapted, he saw that the sky was full of stars, so many he could not recognize constellations. He craned toward the flat glass to look back over his shoulder, where they were headed, and he noticed a distinct arc beyond which there were no stars at all, only blackness. All at once he was hit with the eerie realization that this hole in the stars was the moon.”
From just before firing to enter Lunar orbit during Apollo 11:
“Armstrong, Aldrin, and Collins had not seen the moon on the way out, but according to the flight plan they were supposed to take some pictures of it a few hours before braking into lunar orbit. As they finished breakfast, a sudden darkness came around them, and for the first time in the flight the sky was full of stars, too many to count, each with a steady gemlike brilliance. They had flown into the lunar shadow.”
From just before the burn to return to a free-return trajectory during Apollo 13:
“Before they could fire the engine, however, they would first have to align Aquarius’s navigation platform with the skies, and one glance out the window told them that would be all but impossible. The sky was filled with particles of debris from the explosion–in a cloud that observers later estimated to be 20 miles across–that caught the sunlight and shone like real stars.”
That wasn’t in the lunar shadow, I know, but sets up for a later passage:
“Nearly three hours later, Apollo 13 flew into the moon’s shadow. Outside, where the sky was suddenly filled with stars, the men could see dark silhouettes which they realized were debris from their explosion.”
(sorry for any typos)
So, it seems that when they were not in the glare of one bright object or another, stars were quite visible. How this confusion came up I don’t know, but I suspect there was a slip of context somewhere along the line.
First we make the assumption that “Our” rules of physics apply throughout the entire infinite universe. We also tend to assume that light travels at a maximum speed. It also seems right as several have suggested that space could appear white rather than dark. However, if many of the white bodies are moving AWAY at greater than light speed would this explain why they can’t all be seen. I’ll let you decide what point I was trying to make, I lost track after the word First!