240 B.C.
Eratosthenes
How did they measure the circumference of the Earth?
Eratosthenes
sent a man to Syene from Alexandria on foot to measure the distance between Alexandria and Syene. Thus, Eratosthenes measured the distance between the two cities is 800 km. He multiplied by 800 km to 50 and calculated that the Earth’s circumference is 40,000 km.
What did Eratosthenes discover?
Eratosthenes may have been the first to use the word geography. He invented
a system of longitude and latitude
and made a map of the known world. He also designed a system for finding prime numbers — whole numbers that can only be divided by themselves or by the number 1.
How was radius of Earth discovered?
This means that Eratosthenes estimated the circumference of the Earth to be about 40,000 km. He also knew that the circumference of a circle was equal to 2 times π (3.1415…) times the radius of the circle. (C = 2πr) With this information, Eratosthenes inferred that the Earth’s radius was
6366 km
.
How did Eratosthenes measure the size of the Earth?
On the day the Sun shone on the bottom of the wells in Syene, Eratosthenes measured the Sun’s position in the sky over
Alexandria
. It was seven degrees away from the zenith, meaning Syene must be seven degrees away from Alexandria as measured on the circle that is Earth’s circumference.
What is the exact shape of the earth?
The oblate spheroid, or oblate ellipsoid
, is an ellipsoid of revolution obtained by rotating an ellipse about its shorter axis. It is the regular geometric shape that most nearly approximates the shape of the Earth.
Who discovered the planet Earth?
| PLANET | Earth | MASS | 1.000 | RADIUS | 1.000 | SURFACE GRAVITY (g) | 1.00 |
|---|
What was the greatest work of Eratosthenes?
What is Eratosthenes famous for? Eratosthenes measured Earth’s circumference mathematically using two surface points to make the calculation. He noted that
the Sun’s rays fell vertically at noon
in Syene (now Aswān), Egypt, at the summer solstice.
What were the first Greek dramas called?
The playwright Aeschylus added a second speaking role, called the antagonist, and reduced the chorus from 50 to 12. His play ‘
The Persians
‘, first performed in 472 BC, is the oldest surviving of all Greek plays.
What did Claudius Ptolemy discover?
Ptolemy made contributions to astronomy, mathematics, geography, musical theory, and optics. He compiled a star catalog and the earliest surviving table of a trigonometric function and established mathematically that
an object and its mirror image must make equal angles to a mirror
.
What is Earth’s radius?
According to data taken by 183 high-school classes participating in a World Year of Physics project, “Measure the Earth with Shadows”, the radius of Earth is
6563 km
, compared to the accepted value for the mean radius of 6371 km. Of course, no one is claiming the size of Earth has actually changed.
Who invented radius?
Eratosthenes of Cyrene
(/ɛrəˈtɒsθəniːz/; Greek: Ἐρατοσθένης [eratosthénɛːs]; c. 276 BC – c. 195/194 BC) was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist.
How fast is the Earth spinning?
The earth rotates once every 23 hours, 56 minutes and 4.09053 seconds, called the sidereal period, and its circumference is roughly 40,075 kilometers. Thus, the surface of the earth at the equator moves at a speed of 460 meters per second–or roughly
1,000 miles per hour
.
Who first measured the distance to the sun?
Historically, the first person to measure the distance to the sun was
the Greek astronomer Aristarchus
around the year 250 B.C. He used the phases of the moon to measure the sizes and distances of the sun and moon. During a half moon, the three celestial bodies should form a right angle.
Where did the sun come from?
Formation. The Sun and the rest of the solar system formed from
a giant, rotating cloud of gas and dust called a solar nebula about 4.5 billion years ago
. As the nebula collapsed because of its overwhelming gravity, it spun faster and flattened into a disk.
