The sky is everything that lies above the surface of the Earth, including the atmosphere and outer space.
In the field of astronomy, the sky is also called the celestial sphere. This is an abstract sphere, concentric to the Earth, on which the Sun, Moon, planets, and stars appear to be drifting. The celestial sphere is conventionally divided into designated areas called constellations.
Usually, the term sky informally refers to a perspective from the Earth's surface; however, the meaning and usage can vary. An observer on the surface of the Earth can see a small part of the sky, which resembles a dome (sometimes called the sky bowl) appearing flatter during the day than at night. In some cases, such as in discussing the weather, the sky refers to only the lower, denser layers of the atmosphere.
The daytime sky appears blue because air molecules scatter shorter wavelengths of sunlight more than longer ones (redder light). The night sky appears to be a mostly dark surface or region spangled with stars. The Sun and sometimes the Moon are visible in the daytime sky unless obscured by clouds. At night, the Moon, planets, and stars are similarly visible in the sky.
Some of the natural phenomena seen in the sky are clouds, rainbows, and aurorae. Lightning and precipitation are also visible in the sky. Certain birds and insects, as well as human inventions like aircraft and kites, can fly in the sky. Due to human activities, smog during the day and light pollution during the night are often seen above large cities.
(a) What is the acceleration of two falling sky divers (mass 110.0 kg including parachute) when the upward force of air resistance is equal to one-fourth of their weight?
(b) After popping open the parachute, the divers descend leisurely to the ground at constant speed. What now is the force...
The everyday sky is blue, though it can be noticed there are different hues depending on how high or low you look. Towards the horizon, the sky becomes much lighter, and looking low enough it appears white. What is the reason for this?
Would you please tell me how long a starlight can reach my eyes ?
I have heard that a star might have already gone dead although I can still see it shining bright above...That is correct, right ?
And another question is as to why I see the star shine with different colors, while it obviously...
This is a new launch plaform idea to assist Nasa in meeting it's extra-planetary goals.
It seems that a large helium-supported platform in the upper atmosphere could save a lot of launch energy and pollution.
The platform might be quite large, perhaps 0.5 to 2 km in diameter, and could be...
I was reading some article about some scientists who were able to 'read' some sort of cosmic background radiation and determine the size, shape, and age of the universe or whatever. How do they take these radiation readings and create an 'image' or understanding of the universe?
I woke up at 4:30 PST (San Diego) and couldn't go back to sleep so I decided to take my telescope out and finally check out Saturn, the Orion Nebula, and Mars again. They looked awesome through the 8" telescope and I wish I was able to take pictures. Then around 5:30 I saw a really bright object...
On a clear day, the sky appears to be more blue toward zenith than it does towards the horizon. why?
I thought it was because the atmosphere is denser higher up than it is at the Earth's surface but a friend told me "the temp of the upper atmosphere is higher than its at the Earth's urface and...
"In addition to the usual fare that comes with a thunderstorm, many on the city’s Northeast Side witnessed an unusual dark circle in the sky, which turned out to be a ring of smoke that a weather official said emanated from an 'explosion caused by lightning'"...
Not quite sure where this post should go so I'm putting it here.
My wife and I were walking the dog the other night and looking toward scorpio we saw a flash of light and then a very broad "vapor trail" like a glowing stripe crossed upwards across the sky. We walked on further and about five...
[SOLVED] Why is the sky blue using avogardo's number?
This question was brought up in a physics class, and was never answered for me.
I was wondering if anyone here can tell me, given avogadro's number, why is the sky blue? (including all the messy equations if possible).
I believe...
Saturn sets before it gets dark and Jupiter right after. I've already seen the cluster in Hercules and the Andromeda galaxy. What else can I look for? Light pollution in my area is moderate, but nothing horrible. I'm using an 8" Meade Starfinder. Thanks!
Einstein proved wrong about blue sky!
In 1911 Einstein published an explanation of why the sky is blue
based on analysis of Rayleigh scattering by nitrogen and oxygen molecules.
His analysis was sufficiently detailed and accurate that it was used to provide an independent measurement of the...
This spring was a good time to spot the direction that
our little fleet of galaxies---the Local Group---is traveling in the sky.
I calculated this for myself about 10 years back and recently had it confirmed when someone gave an arXiv reference
http://www.arxiv.org/abs/astro-ph/0210165
in...