Why the sky is dark at night?

Answer 1

Because when it is night where you are, you are facing away from the sun, therefore light from the sun does not reach you.

Answer 2

Because the "sky" does not receive enough light to be seen.

In the day, the air molecules refract enough light from the sun to become visible (the air refracts blue light much more efficiently than red light). That is why the sky is blue during the day, and bright enough so that we do not see stars.

After sunset, the air above you is still lit. In fact, until the sun gets 6 degrees below the horizon, there is enough light to go on about our business as if it were day. That period is called civil twilight.

When the sun gets to 12 degrees below the horizon, the sky is still giving off light (from the higher layers: e.g., stratosphere) and, for example, the horizon is still --barely -- visible. But it is dark enough to stars to be visible. This is the period during which navigators could use their sextants to observe the altitude of stars above the horizon. This period is called Nautical Twilight.

Although barely percetible, there is still some light coming from the sky until the sun reaches 18 degrees below the horizon. Astronomers have to wait that long if they want the sky to be dark enough for astrophotography. That last period is called Astronomical Twilight. After that, the sky is dark because it does not get enough light from the rest of the universe (the reason for that is Olber's paradox already covered by Campelp2002).

By symmetry, the same thing occurs in the morning: Astronomical, Nautical and Civil dawn, then sunrise.

Sometimes, when the Full Moon is very bright, the sky is (barely) visible. It refracts some of the light received from the Moon. It is certainly enough to show on astro-photographs. That is why astronomers who specialise in "deep-sky objects" like faint galaxies, do not appreciate the Full Moon.

Answer 3

The sky is not dark because the Earth rotates around the sun. The sky is dark because the earth rotates around it's own axis, causing the sky to be dark when we are not facing the sun.

Answer 4

Because the sky (per se) is always dark, and the Sun is away from our side of the Earth. The sky is only light when the Sun is on our side of the Earth. In outer space it is always dark

Answer 5

There is always some light. When the earth moves around the sun, it causes seasons like summer and winter. As the earth rotates, the sun apears to rise and set. I have never seen it so dark outside that you can not see your hand. I have been in dark rooms. And there is some light there also. After you are there for a while, you can see tiny pin holes of light sometimes.

Answer 6

The Earth is a huge spinning ball of dirt, rock, metals, and water with various molten materials in its central core. We,
the human residents on the surface of the Earth go around and around as the Earth spins, but do not notice the sensation of movement physically. Visually we can see other objects move relative to our position, however. The Sun (our source of heat and light) sits at the center of our Solar System. As the Earth spins around and around, residents of various places on Earth see the Sun for a while, until the spinning rotation of the Earth places them on the side of the Earth's Ball Shape away from the Sun. When that happens, the rays from the Sun are blocked by the Earth itself, and this is what we call "night." Those residents experiencing "night"
continue to do so until the Earth's spinning movement brings them on around to where the Sun's rays begin hitting them again. At that point they are on the side of the Earth that is facing the Sun for a while. We call that "Daytime." In general terms, we have, therefore, twelve hours of daytime, and twelve hours of nightime.

However, the Earth does not spin with its axis exactly straight up and down relative to the Sun. The Earth's axis is tilted about 23.5 degrees to its eliptical orbit around the Sun. That means that depending upon where on the surface of the Earth you reside, you may get more than 12 hours of daylight each day, or less than that. Toward the extreme ends of the Earth (North Pole and South Pole) you may, in fact, have extended days or extended nights which might last for several months at a time.

Coming full circle in this answer, then, the Sun provides most of our basic light illumination, and heat. Some illumination comes from star light and moon light. On clear nights when there is no cloud cover, illumination from the Moon and stars might make it possible to see fairly well in the dark. Darkness is the absence of light from all of these various sources. Darkness suggests we are on the side of the Earth facing away from the Sun, and probably some extensive cloud cover which blocks light from the stars and reflected light from the Moon from reaching our eyes.

Regards,
Zah

Reference: ASTRONOMY, by Mark A Garlick, Firefly Books, Weldon Owen Inc.2004, Printed in China.

Answer 7

That is Olbers' paradox. If there are an infinite number of stars in an infinitely large universe, the whole sky should be as bright as the Sun. The modern explanation is that the universe is not infinite. See the source.

Answer 8

The sky is dark at night because the earth is roatatiing around the sun. When it is dark, the earth is on the backside of the sun where no light is visible, hense, making it dark. Where it may be dark where you live, it is bright oustide on the other side of the wrold where the sun is facing it.

Answer 9

the side of the earth facing the sun during the day is turned away at night...no light, hence dark sky...

Answer 10

b coz sun is facing the other side of the earth