Introduction to modern astronomy, 2023/2/27

1. Introduction to modern astronomy 3
島袋隼⼠(Hayato Shimabukuro)（云南⼤学、
SWIFAR）
©GETTYIMAGES

2. 2. The history of astronomy
~ From ancient astronomy to Copernicus~

3. The origin of astronomy
•Astronomy is one of the oldest natural sciences. The old people in recorded history made
observations of the night sky
•Babylonians（如巴⽐伦）, Greeks（希腊）, Indians（印度）, Egyptians（埃及）,
Chinese（中国） etc…
•Astronomy in Babylonia. The original stone plate describes
astronomy, and history in B.C. 652- A.D 61 (2500 years ago !)
•It was important for old people to know the motion of stars and the sun for agriculture(农业)
•In this stone plate, there is a description of
aurora.

4. Ancient astronomy
Stonehenge(巨⽯阵) : located on Salisbury Plain in England. It is thought
to be built in BC 3000-1500 (5000-3500 years before !)
•Stonehenge is thought as an early “astronomical observatory(天体观测站)”
- not in the modern sense of observatory
•It may be used to measure the motion of sun, especially summer solstice(夏⾄)

5. Ancient Chinese astronomy
后汉书
客星＝超新星（Supernova）: Explosion of giant star
The supernova appeared suddenly in the sky and then
slowly fade-away

6. Mystery about the record of supernova
•Some record of supernova (SN1054, happened in 1054) is left in Asia (China, Japan, etc).
•Curiously, however, there are few records of SN1054 in the West.
Why??
•We do not know the reason. But, it may be because old western regions are Christian worlds
•The Roman Church at that time thought religion and astronomy were closely related and regarded the sky
(the universe) as "perfect and absolute”.
•Thus, in the Christian world, where astronomy and
religion are tightly connected, recording the change
in the sky (in this case, a supernova explosion) was a
deadly and dangerous act!

7. •However, a paper has recently been published that suggests that the description of SN1054
may be recorded on the coin.
•This is only a hypothesis, and it has not been decided that it is correct, but if true, it is
a brave action.
https://arxiv.org/abs/2206.00392
Do you believe it or not??
Mystery about the record of supernova

8. Question
•Which view of the universe do you believe?
The planets (including earth) orbit the sun. The sun (including other planets) orbit
the earth.

9. •People who live in the 21st century believe “the earth orbits the sun”.
Why do we believe the earth orbits the sun?
•But, why do you believe it? Because everyone
says? You learn it at school?
•It is natural the sun orbits the earth rather
than the earth orbits the sun.
You

10. Why do we believe the earth orbits the sun?
•Some of you may think people before the 16th century
are not smarter than us (living in the 21st century). Thus,
they supported “the sun orbits the earth”.
But, this is incorrect!
•They believed it because it was natural to explain
the behaviors of planets and the sun at that time.
•The reason why they believe “the sun orbits the
earth” and we believe “the earth orbits the sun” is
the same! It is natural for them and us.
We must keep in mind that common sense
can always be updated!

11. Ancient Greek
Geocentric universe (地⼼宇宙)
Suggestion
Aristotle(亚⾥⼠多德)
(BC384-322)
The Earth lay at the center of the universe and all other bodies moved around it.

12. Ancient Greek
Ptolemaic Model
Ptolemy(托勒密)
(AD 83-168)
Ptolemaic model requires a series of no fewer than 80 circles to explain the motion of planets !
The Ptolematic picture of the universe survived for almost 14 centuries until 16th century!!

13. One of the complex motion in the universe is retrograde motion（逆⾏运动）
Motion of planet
To explain retrograde motion, Ptolemaic Model requires many circles !

14. Ptolemaic Model is very complex !!
The universe is simpler!
Copernicus(哥⽩尼)
(1473-1543)
Copernican revolution
At 16th century, a major change has occurred in human’s view of the universe by
Copernicus.
Heliocentric model (⽇⼼模型，太阳中⼼模型)
The earth is not located at center of the universe. The
sun is located in the center and others planets orbit the
sun.

15. Heliocentric model（太阳中⼼模型）
Heliocentric model can explain not only daily and seasonal changes in the heavens, but also
retrograde motion of planets naturally.

16. Explanation for retrograde motion
Let’s consider the location of the earth and Mars. How do we see apparent motion of Mars?

17. Explanation for retrograde motion
＋
=
•We can naturally explain
逆⾏运动 !
•We do not need many circles!
•太阳模型 is simper and better!

18. Still incomplete…
•Copernicus is still influenced by Greek thinking, that is to say, planet’s motion is circle
•To bring his theory into agreement with observations of the night sky, he was forced to
retain the idea of epicyclic motion. Thus, his theory is still complex and incomplete.
•Despite the support of some observation data, his theory was not accepted by his fellow scholars
and public because his theory violates many of religious teachings of the time.
•After Copernicus’s death, Kepler, Galileo Galilei, and Newton developed his theory.
The revolution has just begun….
To be continued…

19. Summary
• Astronomy is one of the oldest science in human history
• At
fi
rst, human thought the earth is located at center and
the sun orbits around the earth.
• Copernicus suggested that the sun is located at center
and the earth orbits around the sun.