Eratosthenes

## How did Ptolemy 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.

## Who among the old Greek philosophers scientists was the first to measure the circumference of Earth?

philosopher Aristotle

12,742 km

## What is true 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.

## WHO estimated that circumference of the earth is 5000 Yojanas?

Posidonius is supposed to have measured the angular elevation of Canopus at Alexandria and determined that the angle was 1/48 of circle. He used a distance from Alexandria to Rhodes, 5000 stadia, and so he computed the Earth’s circumference in stadia as 48 times 5000 = 240,000.

40,075 km

## How long would it take to drive from the Sun to Earth?

(WKBN) – Have you ever wanted to know how far the sun is from the earth? Here are some fun facts about the distance to the sun: On average, the sun is 93 million miles from the earth. It would take 1,430,769 hours to drive there at 65 miles per hour.

5.972 × 10^24 kg

around 415 hours

## What if Earth stopped spinning?

If the Earth stopped spinning suddenly, the atmosphere would still be in motion with the Earth’s original 1100 mile per hour rotation speed at the equator. This means rocks, topsoil, trees, buildings, your pet dog, and so on, would be swept away into the atmosphere.

## Is the Earth rotating faster?

The Earth spun faster than normal last year, according to scientists. In fact, the Earth broke the record 28 times in 2020. And it’s still spinning faster. While Earth is, on average, pretty reliable and takes 86,400 seconds to rotate around its axis, it’s not perfect.

## Why don’t we feel the earth spinning?

Bottom line: We don’t feel Earth rotating on its axis because Earth spins steadily – and moves at a constant rate in orbit around the sun – carrying you as a passenger right along with it.

## Can a plane fly faster than the Earth rotates?

At the equator, the Earth spins about twice as fast as a commercial jet can fly. That rate slows the closer you get to the poles, but regardless, it’s always going to be faster than a plane.

## Why do we not fall off the earth?

Gravity always pulls you towards the middle of the object. So for the Earth, which is shaped like a ball, the force of gravity pulls you to the centre from every point on the ground. That’s why, no matter where you stand on the Earth, you always feel like the ground is at the bottom and the sky is up.

## Can you fall off the moon?

Although you can jump very high on the moon, you’ll be happy to know that there’s no need to worry about jumping all the way off into space. In fact, you’d need to be going very fast – more than 2 kilometres per second – to escape from the moon’s surface.

Antarctica

## How do we stay on Earth?

Gravity. Fortunately for us, Earth’s gravity is strong enough to hold onto its atmosphere. Mars, for example, is less than half Earth’s size and around one-tenth Earth’s mass. Less mass means less gravitational pull.

## Why do we have an atmosphere?

And that’s a good thing because our atmosphere protects life on Earth in many ways. It absorbs harmful ultraviolet radiation from the sun, helps keep Earth’s surface warm via the greenhouse effect, and reduces temperature extremes between day and night. Yay atmosphere! It keeps Earth livable.

## What is Earth’s atmosphere made of?

The air in Earth’s atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen. Air also has small amounts of lots of other gases, too, such as carbon dioxide, neon, and hydrogen.

## Why do we live on Earth?

What makes the Earth habitable? It is the right distance from the Sun, it is protected from harmful solar radiation by its magnetic field, it is kept warm by an insulating atmosphere, and it has the right chemical ingredients for life, including water and carbon.

## Is Earth losing atmosphere?

A pair of researchers from Toho University and NASA Nexus for Exoplanet System Science has found evidence, via simulation, that Earth will lose its oxygen-rich atmosphere in approximately 1 billion years.

## Why did Mars lose its atmosphere?

NASA pointed out that Mars had a thick atmosphere shortly after it was formed, and most of the composite in its atmosphere was carbon dioxide. However, due to the lack of magnetic field protection, the majority of the Martian atmosphere was destroyed by the strong solar wind, and escaped to space (Carlisle, 2015).

## Is Venus losing its atmosphere?

Due to the lack of the intrinsic magnetic field on Venus, the solar wind penetrates relatively deep into the planetary exosphere and causes substantial atmosphere loss.

## Can Earth lose its magnetic field?

The direction and intensity of the dipole change over time. Over the last two centuries the dipole strength has been decreasing at a rate of about 6.3% per century. At this rate of decrease, the field would be negligible in about 1600 years.

## What would happen if Earth lost its magnetic field?

If Earth lost its magnetic field, there would be no magnetosphere – and no line of defense, even from weaker solar storms. Our power grids would be more vulnerable than ever, and even our computers and other electronics could suffer damage if a solar storm struck.