Omelette Elementary School Why is the night sky pitch black?

We can see that the night sky is full of stars, so why can't the light from all the stars add up to light up the night sky? The German physicist Olbers asked the conundrum in 1823: if the universe was infinitely large and full of stars or galaxies, the night sky should be bright.

However, this is not the case.

Astronomers have been trying for years to explain what is known as the "Olbers paradox." One explanation is that dust between stars or galaxies blocks the light emitted by distant stars, making the night sky appear pitch black.

But in reality, the dust warms up when exposed to light, becoming as bright as the light source. Another explanation is that the redshift of distant galaxies turns light from visible to invisible, infrared. If this explanation is true, then the shorter wavelength of ultraviolet light should also be moved to the visible range, which did not happen.

Scientists are currently interpreting the "Olbers paradox" in two ways. First, even though the universe is infinitely large, it is not infinitely old. This is very important because light travels at a finite speed of about 300,000 kilometers per second.

The farther away a star is from us, the longer it will take for the light it emits to reach us. Second, since the time it takes for the light from stars at different distances to reach the Earth varies, it is never possible to see the light from stars at different distances at the same time. Either the light from the farthest star has not yet reached Earth, or the light from distant stars has been consumed by neighboring objects in the long process of reaching Earth, so that the night sky appears pitch black.

You must know that in the Milky Way, if there is no sun, it is dark, and the day is divided into day and night, the sun illuminates this half of the planet during the day, and at night the sun illuminates the other half of the planet. So there is no sunlight from the sun at night.

And then there are the stars.

The stars shine by the light of the sun. So the stars themselves are not bright, so why is the night sky pitch black?

First of all, what's in the night sky: the stars and the moon. The light of the moon is far stronger than that of the stars. However, it is not that his light is strong, but that the moon is close to us.

Just like the day, in fact, there are stars during the day, but why can't we see it?

The reason is just as you might think: the sun shines brighter than the stars.

That should make sense.

Don't forget to give points!

At night, because the Earth has its back to the Sun when the Earth rotates!

In addition, everything in the world does not shine!

The sky is dark at night for two reasons. One is that the stars in the universe are too far away from the Earth, and the light that can reach the Earth is also the light emitted by stars years ago, or even billions of years ago, when these stars may have long since died. As the universe continues to expand, the light from some of the more distant stars will never reach the Earth, because the light dies before it reaches the Earth.

That is to say, the light that can reach the earth is limited and will not illuminate the earth. The second reason is that the stars are too far away from the earth, and the light that hits the earth is too weak, just like using a candle to illuminate a building, the light intensity is too weak. Therefore, the sky is destined to be dark at night.

Because the earth is turned to the other side, the sun is stationary, and the earth is moving, and the sun's illumination is limited, because the light cannot move, it can only shine on one side of the earth, so the other side is pitch black, so when we see stars shining in the sky, because the light of other small stars is very weak, it is too far away from the earth.

The sun emits visible light because the earth rotates, and the side of the earth facing the sun, visible light can reach the earth, that is, during the day. When the Earth faces planets such as Mars, some planets don't even emit light because these planets don't emit bright light. There is no light or very weak light, which we call night.

Because the sky is silently mourning for the dead in Wenchuan!!

According to Maxwell's equations, it can be solved that c=sqr(u0eo), that is, the speed of light c is independent of the object's reference frame, from which Einstein deduced the theory of the invariance of the speed of light, that is, c is the same in any reference frame. From the special theory of relativity v=v1 sqr(1-(u c) 2), bringing u=c in, we can see that the denominator is 0, which is not true.

In addition, the speed of light of a single object cannot be the speed of light, but imagine illuminating the moon with a laser, as long as the angular velocity is large enough, the spot speed can exceed the speed of light, but this is no longer a single object.

Fake, basically fake, you can see "All Tang Poems", as for the whole Tang Dynasty poems uploaded on the Internet now are not included, as for whether Li Bai wrote it It can be seen from the ten-point rhyme and artistic conception that the level is too secondary, if such a few limerick poems can be circulated for more than a thousand years, then Chinese culture will be blind.

Fake, there is a modifier that is specifically designed to modify the poem.

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No, this is a pseudo-scientific view of previous antiquity.

1. For thousands of years, human beings have been very interested in the land in which they live. In ancient China, there was a saying that "the sky is round and the earth is round", the West Asians believed that the earth was a hemisphere floating on the ocean, the ancient Greeks originally imagined it as a flat disk, and so on. In the 6th century B.C., the ancient Greek mathematician Pythagoras first proposed the concept of the earth.

Around the 3rd century BC, Eratosthenes, a scientist living in Alexandria, established the concept of the earth using geometric methods. In the 2nd century AD, the Greek geographer Ptolemy also described the earth as a sphere in his Almagama astronomy. These are all important achievements of human understanding of the earth, but they are only some mathematical inferences and theoretical arguments.

2. During the Renaissance, humanists discovered these doctrines of ancient Greece, and many people at that time already believed that the earth was round, and explorers who opened up new routes had this belief. 1519 In 1522, the fleet of Magellan the Portuguese completed the first circumnavigation of the world in the history of mankind, which proved to all mankind with irrefutable facts that the earth is round. This is of great significance to the development of science and mankind's understanding of the universe.

Both of these are important and indispensable, and if you stick to them, you will definitely lose weight.

You can eat less and eat more often, pay attention to exercise, so that the scientific ** will be more effective, if you are worried about the lack of nutrition**, you can drink some Dutch milk skim milk, I am like this**, the nutrition of this milk can meet the needs of the body.

It can be carried out by exercising**Ah, and you should also pay attention to the light diet, usually drink some Dutch milk skim milk, and the nutrition is still low in fat.