General questions about space, Sky Day, Space Day, etc.
From what altitude can we define "space"?
There is no specific border between the Earth's atmosphere and space, but in most cases space is beyond 100 kilometers where air rarely exists.
Why does space look black (dark)?
We can "see" an object as the light hits that object and its reflection reaches our eyes. However, space between the stars is almost a vacuum. In other words, there is nothing to reflect the light except for small dust particles. Thus, the light can go through there, but light can not reflect back from the surrounding area and as a result, space looks dark and black.
What will happen to the human body if you go to space without wearing a space suit.
If a human went out into space without wearing a space suit, since space is almost a vacuum, the liquid in our body and blood will come to a boil, and the functions of various organs in the body will stop, leading to death.
Are there any aliens?
At present, there is no clear answer as there is no scientific or observational proof of aliens. However, there are many scientists who believe in "life in space," and investigations and research are ongoing.
What is "Sky Day"?
Every year, September 20 is "Sky Day" in Japan.
What is "Space Day"?
Every year, September 12 is "Space Day" in Japan.
Starting form ISY, Japan also decided to promote space for the long term and commemorative events for "Space Day" have been held every year since then.