Earth's Shape
At first glance, the ground seems flat, but photos from space, like the famous “Blue Marble” image by the Apollo 17 shuttle, show it to be round.
Ancient Greeks figured this out long before space travel. They observed Earth's curved shadow on the Moon during a lunar eclipse, proving its shape.
Galileo’s observations confirmed that planets orbit the Sun and are spherical, suggesting Earth, as a planet, is also spherical.
You can also see this by watching a ship sail over the horizon. The bottom of the ship disappears before the top, something that wouldn’t happen if the Earth were flat.
Earth is an oblate spheroid that is slightly flattened at the poles.
The equator divides Earth into the northern and southern hemispheres, with the northern hemisphere including North America and Europe and the southern hemisphere including South America and Australia.
The prime meridian, which is 0 degrees longitude, and the international date line, the 180 degress meridian, divide the world into the Eastern and Western Hemispheres, including Asia and the Americas, respectively.
Earth’s Shape
Earth may look flat from where we stand, but it is actually an oblate spheroid—meaning it is mostly round but slightly flattened at the poles and bulging at the equator. Scientists have gathered evidence for centuries, from astronomical observations to satellite images, to prove Earth's shape.
The Earth's shape is essential for comprehending the planet's past, present, and future. For example, by studying the Earth's changing shape, scientists can gain insights into the movement of tectonic plates and the evolution of continents over geological timescales. Additionally, monitoring changes in the Earth's shape can help scientists track the melting of glaciers and ice sheets, which is crucial for understanding the impacts of climate change.
Science and Engineering Practices (SEP): Developing and Using Models
Scientists use models to study and explain Earth's shape. Early astronomers used shadow experiments and star observations to conclude that the Earth is round. Today, 3D models, satellite images, and computer simulations prove Earth’s actual shape. Scientists also use mathematical models to calculate Earth's curvature and gravitational effects. These models help predict planetary motion, navigation, and even climate patterns.
Activity Ideas:
- Exploring Early Earth Models – Recreate historical experiments, such as measuring shadows at different locations, to understand how early astronomers concluded that the Earth is round. Discuss how ancient observations of lunar eclipses and star positions supported this idea.
- Using 3D Models and Globes – Compare a globe to flat maps to see how Earth's round shape affects representations of continents and distances. Analyze satellite images to observe Earth's actual shape and discuss why it is slightly flattened at the poles.
Crosscutting Concepts (CCC): Patterns
Patterns in nature help scientists understand Earth's shape and how it influences different systems.
- Pattern: The way ships disappear over the horizon suggests a curved surface.
- Example: As a ship sails away, the bottom disappears before the top, following Earth’s curvature.
- Pattern: Shadows cast during eclipses and at different latitudes show Earth's spherical shape.
- Example: The ancient Greek scientist Eratosthenes calculated the Earth’s circumference by measuring shadow angles in two cities.
- Pattern: Gravity pulls objects toward Earth’s center, shaping the planet into a sphere over time.
- Example: Unlike small asteroids with irregular shapes, planets, and large moons are rounded by their own gravity.
At first glance, the ground seems flat, but photos from space, like the famous “Blue Marble” image by the Apollo 17 shuttle, show it to be round.
Ancient Greeks figured this out long before space travel. They observed Earth's curved shadow on the Moon during a lunar eclipse, proving its shape.
Galileo’s observations confirmed that planets orbit the Sun and are spherical, suggesting Earth, as a planet, is also spherical.
You can also see this by watching a ship sail over the horizon. The bottom of the ship disappears before the top, something that wouldn’t happen if the Earth were flat.
Earth is an oblate spheroid that is slightly flattened at the poles.
The equator divides Earth into the northern and southern hemispheres, with the northern hemisphere including North America and Europe and the southern hemisphere including South America and Australia.
The prime meridian, which is 0 degrees longitude, and the international date line, the 180 degress meridian, divide the world into the Eastern and Western Hemispheres, including Asia and the Americas, respectively.
At first glance, the ground seems flat, but photos from space, like the famous “Blue Marble” image by the Apollo 17 shuttle, show it to be round.
Ancient Greeks figured this out long before space travel. They observed Earth's curved shadow on the Moon during a lunar eclipse, proving its shape.
Galileo’s observations confirmed that planets orbit the Sun and are spherical, suggesting Earth, as a planet, is also spherical.
You can also see this by watching a ship sail over the horizon. The bottom of the ship disappears before the top, something that wouldn’t happen if the Earth were flat.
Earth is an oblate spheroid that is slightly flattened at the poles.
The equator divides Earth into the northern and southern hemispheres, with the northern hemisphere including North America and Europe and the southern hemisphere including South America and Australia.
The prime meridian, which is 0 degrees longitude, and the international date line, the 180 degress meridian, divide the world into the Eastern and Western Hemispheres, including Asia and the Americas, respectively.
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