The universe around us

for us ordinary people, the vast universe is almost immeasurable. For astronomers, it is not only necessary but also possible to accurately map the celestial bodies in the universe. The unit of measurement used in astronomy is "light years", that is, the distance traveled by light in a year. The speed of light is about 3, kilometers per second, and a light year is about 9.7 trillion kilometers. The diameter of the Milky Way is about 1, light years. There are other galaxies outside the Milky Way, which are billions of light years away. The newly invented quasar is located at the edge of the universe that we can observe at present, about 1 billion to 2 billion light years away from the earth, and it is the farthest celestial body known so far.

it's hard to imagine such a long distance. To measure the distance between other planets or nearby stars in the solar system, the parallax calculation method discovered by the ancient Greeks can be used. Parallax refers to the included angle formed by two lines of sight when viewing the same object from two viewing positions. In astronomy, the way to measure parallax is to form a triangle between two observation points and the observed celestial body, know the length of the connecting line (that is, the baseline) of the two observation points, and then measure the orientation of the celestial body (that is, the vertex angle of the triangle) from these two observation points, so as to find out the distance between the celestial body and the earth. The longer the baseline, the more accurate the result will be. Usually, when measuring the distance of celestial bodies close to the earth, such as the moon, the radius of the earth can be used as the baseline, and the measured parallax is called "Sunday parallax". If we want to measure the distance of celestial bodies outside the solar system, we usually take the distance between the earth and the sun as the baseline, and the measured parallax is called "annual parallax". It is very accurate to measure celestial bodies within 8.6 light-years by this parallax method, and it can also be generally accurate to measure celestial bodies as far as 1 light-years. If it helps you, please adopt it.