## How do scientists measure the size of Earth?

Scientists aim radio telescopes at distant objects called quasars and measure how long it takes their radio signals to reach Earth. Right click images to download them if they automatically display in your browser.

How was the diameter of Earth measured first?

The Greek philosopher Aristotle (384-322 B.C.) is credited as the first person to try and calculate the size of the Earth by determining its circumference (the length around the equator) He estimated this distance to be 400,000 stades (a stadia is a Greek measurement equaling about 600 feet).

### Who first measured the diameter of the Earth?

Eratosthenes of Cyrene
The first person to determine the size of Earth was Eratosthenes of Cyrene, who produced a surprisingly good measurement using a simple scheme that combined geometrical calculations with physical observations. Eratosthenes was born around 276 B.C., which is now Shahhat, Libya.

How do you measure diameter?

Just divide the circumference by π to find the diameter. For example, if your circle has a circumference of 23 inches, the diameter would be 23/π, or approximately 7.32 inches. If you only know the area of the circle, use the formula diameter = 2 x √(area/π).

#### How did the Greek know that the Earth is spherical?

In the 5th century B.C., Empedocles and Anaxagoras offered arguments for the spherical nature of the Earth. During a lunar eclipse, when the Earth is between the sun and the moon, they identified the shadow of the Earth on the moon. As the shadow moves across the moon it is clearly round.

How did Aristotle calculate the circumference of the earth?

By measuring the length of the shadow in Alexandria at noon on the Summer Solstice when there was no shadow in Syene, he could measure the circumference of the Earth! At Syene: The Sun is directly overhead, no shadows are cast at that moment.

## What tool do you use to measure diameter?

Caliper Gauge: is a measuring tool to measure outside/ inside diameter/ thickness etc.

How did the ancient Greek know that the Earth is spherical?

### What is the real shape of the Earth?

The Earth is an irregularly shaped ellipsoid. While the Earth appears to be round when viewed from the vantage point of space, it is actually closer to an ellipsoid. However, even an ellipsoid does not adequately describe the Earth’s unique and ever-changing shape.