The night sky in science fiction often looks beautiful. Lots of beautiful cosmic nebulae and dust scattered in the sky. But the reality is not that beautiful. Out sky doesn’t look like Star Wars, Star Trek, Guardian of the Galaxy, etc.
When looking at the night sky with the naked eye, we can only see a moon that is so big along with a sprinkling of stars that are even tens of thousands of light-years away. While other objects are too far away so they are too small to be seen directly. But is this 100% true?
Inverse Square Law
If we see lights on at a distance of 2 meters, the lights are 4 times dimmer than at a distance of 1 meter. If we see lights on at a distance of 50 meters, the lights are 2500 times dimmer than at a distance of 1 meter. This is what is called the inverse square law.
The inverse square law does not only occur in the light but also the gravitational and electric forces. We can see the pattern in the formula below.
Angular Width / Angular Diameter
Simply stated, the width of the angle is the size of an object based on how big the object is in our perspective. Consider the following image.
The house seen by the person has an angle of 8°, meaning that the size of the house in his view is 8°. Likewise, the plane above, which has an angle width of 31.5°. The closer an object is, the greater the width of the angle and vice versa. This applies to all objects, from everyday objects such as cars and buildings to extraterrestrial objects such as nebulae and galaxies.
The Sky Is So Desolated
The moon, which is 384,400 km from earth, which we usually see at night, has an angular diameter of about 0.5°. Whereas the nearest spiral galaxy, the Andromeda galaxy, stretches up to 3.12° in the sky.
The only reason we can’t see it with the naked eye is that the light is too dim because the Andromeda galaxy itself is about 2.5 million light-years away. This is by the Inverse Square Law above. Some other objects are as follows.
There are still many objects out there that should make the night sky much more beautiful. The work concept of the universe was determined from the beginning. Great distances make them too dim for us to enjoy its beauty.
If we return to the question of why our night sky is not as beautiful as science fiction, then the answer is that space stretches too wide to make the gems of the sky too dim to appear.
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