The first issue: Galileo Telescope, the world's first astronomical telescope

1609, at the age of 45, Galileo Galilei (1564-1642) senior made the world's first astronomical telescope. Does the name sound a little familiar? Yes, the man who threw two small iron balls at the Leaning Tower of Pisa in his elementary school textbook to experiment. My 26 years old, er...that.... Stop! Let's continue to talk about Galileo senior.

But history has been controversial about whether Galileo really did free-fall experiments. The genius scientist Stephen Hawking unabashedly wrote in "A Brief History of Time", "the story can hardly be true, he just did two small balls rolling down the slope of the experiment". Dampier, a renowned researcher in the history of science, feels that he may have done this experiment, but not on the Leaning Tower of Pisa. Some people also think that this experiment was done by Galileo's students or fabricated by his students. Is there a feeling of being cheated?

After all, the experiment is only recorded in the book "Galileo's life history" written by his students Viviani, the specific is true or false, can only be left to history to judge, just as Newton was not really hit by the falling apple to the head, I am afraid no one can say.

But reality tells us that not all the truth in this world must be revealed to the world, sometimes a good lie can make people feel the beauty of the world. On the contrary, the truth is ugly, after all, the good is what people can easily accept. Ahem, far away, back to the topic.

Although named Galileo telescope, the discovery of the telescope principle is not Galileo himself, but a Dutch spectacle maker Hans Lieberich in 1608 accidentally discovered. In fact, this is not objective enough, there is a historical record is Hans's children one day playing on the windowsill, holding two lenses overlapping, and then closed his eyes through the lens to look into the distance, and suddenly found that the distant scene was drawn closer, thus the discovery. Hans made the telescope below this long, exactly at that time can not be called a telescope.

Later, Galileo learned from a friend's letter to make a telescope method, with less than three months to make the world's first real astronomical telescope. So to be exact, Hans was the first inventor of the telescope, and Galileo was only the first person to use the telescope for astronomical observation.

The telescope has a magnification of 33 times, and it was with this telescope that Galileo discovered that the surface of the moon was uneven and the four moons of Jupiter, and thereafter also discovered a series of groundbreaking results. Since then, the inherent concept of human understanding of the universe began to change, liberating the mind and opening up a new era in the development of astronomy and modern natural science. It is no exaggeration to say that, relying on the telescope, Galileo reached the peak of life, so high!

Here it is still necessary to briefly introduce the working principle of this telescope. It consists of a convex lens (objective lens) and a concave lens (eyepiece), light refraction through the objective lens into a real image at the focal point behind the eyepiece (near the direction of the human eye), the image of the eyepiece is an imaginary image, so the eyepiece refraction into a magnified orthogonal imaginary image. The magnification of the Galilean telescope is equal to the ratio of the focal length of the objective lens to the focal length of the eyepiece. The advantage is that the barrel is short and can become a positive image, the disadvantage is that the field of view is relatively small. You can imagine the excitement of the people 400 years ago when they saw this scene.

As the great philosopher Kant said, "There are only two things in the world that can shake people's hearts: one is the brilliant starry sky overhead; the other is the sublime morality in the heart".