What Is Gravity? — Reading Comprehension

Gravity is a fundamental force that acts throughout the universe. Every object with mass experiences gravity, from tiny grains of sand to massive planets and stars. This force pulls objects toward each other and influences the structure and behavior of everything in the cosmos. Without gravity, there would be no planets, stars, or galaxies, and life as we know it would not exist.

The Universal Force of Attraction
The scientist Isaac Newton first described gravity as a universal force of attraction between all objects with mass. According to Newton’s law of universal gravitation, every object attracts every other object in the universe. The strength of this force depends on two main factors: the mass of the objects and the distance between them. The greater the mass, the stronger the gravity. For example, Earth’s gravity is much stronger than the Moon’s because Earth is more massive. Distance also matters—a force called the inverse square law means that if you double the distance between two objects, the gravitational force becomes one-fourth as strong.

Gravity in Action: Everyday Life and the Universe
Gravity affects us in everyday ways. It holds us on the ground and gives us weight. It also explains why objects fall toward the Earth when dropped. The Moon’s gravity is about one-sixth as strong as Earth’s, so astronauts can jump much higher there. The Sun’s gravity is so strong that it keeps the entire solar system—planets, comets, and asteroids—in their orbits. Planets stay in orbit because they move forward fast enough that, although the Sun’s gravity pulls them inward, they do not fall straight in. Instead, they travel in curved paths around the Sun. This balance of gravitational pull and forward motion creates orbits.

Modern Understanding: Einstein and Curved Spacetime
Albert Einstein expanded our understanding of gravity with his theory of general relativity. He explained that gravity is not just a force but a bending, or curvature, of spacetime caused by mass. Massive objects like stars and planets create dents in the fabric of spacetime, and other objects move along these curves. This idea has been confirmed by many experiments, such as observing how light bends near the Sun during an eclipse. While Newton’s law works well for most everyday situations, Einstein’s theory is needed to explain extreme cases, like black holes and the motion of planets close to the Sun.

Gravity connects the entire universe, from tiny particles to enormous galaxies. It shapes the structure of the cosmos and the motions of everything within it. Scientists continue to study gravity to answer deep questions about the universe’s origin and future.

Interesting Fact: The International Space Station orbits Earth because it is moving fast enough that its fall toward Earth matches the curve of the planet’s surface, creating a state of continuous free-fall—what we call "microgravity."

What is gravity?

According to the passage, why does Earth’s gravity feel stronger than the Moon’s?

What happens to the gravitational force if the distance between two objects doubles?

What does the term "spacetime" mean in the passage?

Why do astronauts jump higher on the Moon than on Earth?

What keeps planets in orbit around the Sun?

Which scientist explained gravity as the curvature of spacetime?

True or False: Gravity only acts on Earth and not in space.

True or False: The International Space Station is in continuous free-fall around Earth, which is called microgravity.

What is the main reason scientists continue to study gravity?