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Post by Glom on Nov 15, 2005 18:44:46 GMT -4
This may sound silly but I don't think it is. On a bright clear sunny summer day on earth I don't remember seeing a shadow of myself everyday. I never really looked to make sure but I don't recall seeing one. If it was high noon, your shadow might not have been particularly big, but they should be one. Yes. When an object blocks a surface from being directly illuminated by the sun, it will appear darker than neighbouring surface that is directly illuminated by the sun. The darker region is the shadow. There's no way around that. A phase diagram shows the regions of temperature a pressure where a material will be in a certain state. It takes the form of lines, which divide up solid, liquid and gas. Below a certain pressure and temperature, the liquid region disappears and you just get a direct transition between solid and gas. As you can see in the link, when the pressure goes to 0, water will becomes gaseous at any temperature.
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Al Johnston
"Cheer up!" they said, "It could be worse!" So I did, and it was.
Posts: 1,453
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Post by Al Johnston on Nov 15, 2005 18:45:24 GMT -4
Outer space is a vacuum. Earth is not. The vacuum bgins just beyond our atmosphere. What is our atmosphere made of that prevents the vacuum from penetrating it..? I think Moon Man has just demonstrated the futility of trying to explain anything to him...
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Post by scooter on Nov 15, 2005 18:46:34 GMT -4
Hbers cry about the shadows on the moon going this way and that way. My thoughts on the shadows were they shouldn't even exist at all, or at least during the summer moon missions, which is why I was asking. Thanks for the explanation to the other issues everyone. Jason. I don't know anything about space. I asked the water question before on BA and some said water would freeze some said no. While you peeps know the answer I was still not clear on it. I realize you cannot measure a temperature in empty space, but I believed that it would still be hot or cold, just not measurable. New question for 10 points. Outer space is a vacuum. Earth is not. The vacuum begins just beyond our atmosphere. What is our atmosphere made of that prevents the vacuum from penetrating it..? Gents, be gentle, lets get him smart here... Earth has gravity, that pulls on everythin around it, proportional to distance. The atmosphere is tucked in close to Earth, and is held by the gravity. Outside our thin environmental cocoon is...nothing....vaccuum. Where again, for all intents and purposes, there is nothing. Our atmosphere would indeed feel happy rushing into the vaccuum, were it not for the gravity holding it down. (how terribly convenient for us!) These are good questions, Moon Man, and valid ones. Basic, but valid nonetheless. Dave
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Post by Glom on Nov 15, 2005 18:50:36 GMT -4
Outer space is a vacuum. Earth is not. The vacuum begins just beyond our atmosphere. What is our atmosphere made of that prevents the vacuum from penetrating it..? Vacuum is nothing. You should really be asking it the other way round. What prevents our atmosphere from dispersing into the vacuum? The answer is gravity.
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politik
Venus
on a crusade against ignorance
Posts: 83
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Post by politik on Nov 15, 2005 18:54:17 GMT -4
New question for 10 points. Outer space is a vacuum. Earth is not. The vacuum begins just beyond our atmosphere. What is our atmosphere made of that prevents the vacuum from penetrating it..? Nitrogen, Oxygen, and other gases. They are held in place by the gravity of earth. While not intuitive at first, Air does have mass and is affected by gravity.
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Post by Moon Man on Nov 15, 2005 19:02:08 GMT -4
So air it keeping the vacuum out and the vacuum is not keeping the air in our atmosphere..?
Is it air pressure that keeps the vacuum out..?
Why is the atmosphere ceiling at the height it is and not, say, another 100 miles into space before the vacuum begins..?
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politik
Venus
on a crusade against ignorance
Posts: 83
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Post by politik on Nov 15, 2005 19:04:34 GMT -4
Space can only be described as hot or cold in the sense that an object in space can become hot or cold, depending on the proximity to a source of radiation.
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Post by scooter on Nov 15, 2005 19:05:23 GMT -4
Boiling water... I remember the old pics of the "spaceman" in an early generation space suit, in a vaccuum chamber with a flask of boiling water splashing all over. Lower atmospheric density=lower boiling temp of fluids. (varies with the fluid I suspect) Here, up on Pikes Peak (14110 feet), are the famous deep fried donuts. I don't know the boiling temp of veggie oil at that altitude, but it's noticably below 212F.
Dave
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Post by Moon Man on Nov 15, 2005 19:09:29 GMT -4
Hbers cry about the shadows on the moon going this way and that way. My thoughts on the shadows were they shouldn't even exist at all, or at least during the summer moon missions, which is why I was asking. Therefore, since we agree that a shadow on earth would be very short, if at all, in the summer, and since we agree that the sun on the moon and earth shine equally as bright, for the most part, then why are there major shadows on the moon during the summer missions..? I edited and added to this message after you guys had already quoted and provided a response. Can anyone answer it please..?
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politik
Venus
on a crusade against ignorance
Posts: 83
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Post by politik on Nov 15, 2005 19:09:49 GMT -4
Why is the atmosphere ceiling at the height it is and not, say, another 100 miles into space before the vacuum begins..? That question is as complicated in answering why the atmosphere has the composition it does. Earth's atmosphere evolved over a Billion years to what it is today. It wasn't always as thick as it is now, nor was it made of the same gases. You'll have to look that one up to get a complete answer.
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Post by mushiwulf on Nov 15, 2005 19:14:36 GMT -4
Hbers cry about the shadows on the moon going this way and that way. My thoughts on the shadows were they shouldn't even exist at all, or at least during the summer moon missions, which is why I was asking. Therefore, since we agree that a shadow on earth would be very short, if at all, in the summer, and since we agree that the sun on the moon and earth shine equally as bright, for the most part, then why are there major shadows on the moon during the summer missions..? I edited and added to this message after you guys had already quoted and provided a response. Can anyone answer it please..? Shadow is a property of tyhe angle of the sun in the sky. The astronauts landed on the moon with the sun very low to the local horizon. Therefore you get long shadows. It was lunar morning. Try going outside very early or very late. Regardless of season, you will get long shadows.
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Post by scooter on Nov 15, 2005 19:15:00 GMT -4
So air it keeping the vacuum out and the vacuum is not keeping the air in our atmosphere..? Is it air pressure that keeps the vacuum out..? Why is the atmosphere ceiling at the height it is and not, say, another 100 miles into space before the vacuum begins..? Again, it is gravity that keeps the atmosphere on our planet. Now, why the atmosphere is as deep as it is, I am not certain. It does thin out as you climb high from the surface. In fact, the ISS, 200+ miles up, suffers from atmospheric drag, however miniscule. Thus, it requires "reboost" from time to time, be it from shuttle or a Russian craft docked with it. The suns activity affects the very imperceptable upper atmosphere, causing it to grow and decline. This causes headaches for orbital analyists as spacecraft gently change orbits as a result. Dave
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Post by Glom on Nov 15, 2005 19:21:02 GMT -4
So air it keeping the vacuum out and the vacuum is not keeping the air in our atmosphere..? As I say, vacuum is the absence of anything, so you could say in a philosphical way that the prescence of something keeps out of the absence of anything. Gravity keeps the atmosphere here. Officially, space is defined at 62 nautical miles up. The density of the atmosphere drops of exponentially, so even in space, we have some wisps of atmosphere. That's why the space station must be reboosted every so often, because the small wisps, over the months, lower the orbit. There's isn't a definitive point where the atmosphere just terminates.
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Post by Moon Man on Nov 15, 2005 19:22:25 GMT -4
Okay, thanks for the answers to the atmosphere question.
Where is the ozone layer located..? Right outside our atmosphere or further out..? If it is further out is it beyond the height of the space station..?
If it is below the space station our we not creating holes in it by flying through it over and over again..? even if we're only penetrating it for a few seconds each time given the speed the shuttle is doing..?
Also, the ozone layer protects us from harmful rays from the sun, so what protects the spacestation and the astronauts (yeah I know they are inside it and not outside) if there is no ozone layer inbetween the earth and the moon..?
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Post by Glom on Nov 15, 2005 19:25:00 GMT -4
It's in the upper atmosphere somewhere, well within what is legally defined as our atmosphere and where the atmosphere is thick enough to proclude any stable orbits.
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