Ever wondered why we cannot fly like Superman and other superheros? In this article, we explore together the secrets of gravity, Newton’s three laws, and how the laws of physics keep our bodies from flying. We will know how birds fly with ease while we stay grounded, and how humans made up for it through the invention of planes, balloons, and rockets.
Gravity: The Invisible Hand That Pulls Us to Earth
Gravity is an invisible force that pulls everything toward Earth. When we jump, we rise for a moment, but gravity immediately pulls us back down. The scientist Isaac Newton discovered this force when he observed an apple falling from a tree in the 17th century, inspiring him to formulate the law of universal gravitation, which states that: "every object with mass attracts every other object with mass. The force of this attraction is directly proportional to the product of their masses and inversely proportional to the square of the distance between them". Consequently:
- Any object with mass has gravity, but we mainly notice the gravitational pull of very large objects—like planet Earth—which pulls us much more strongly than a nearby book or chair. Gravity decreases as we move farther from an object, but it never disappears completely.
- Gravity affects an object’s weight, but its mass (the amount of matter it contains) remains the same everywhere.
For example, the Moon’s mass is about one-sixth of Earth’s mass. Consequently, its gravitational force is much weaker than Earth’s. Therefore, astronauts can jump much higher on the Moon—their weight there is only one-sixth of what it is on Earth.
Gravity is measured by the acceleration of a freely falling object, which is approximately 9.8 m/s² on Earth and only 1.6 m/s² on the Moon. In the past, scientists measured gravity using a pendulum; today, they use precise instruments such as gravimeters or satellites.
Newton explained three fundamental laws that govern all motion in the universe, known as Newton’s laws of motion:
- Law of Inertia: If a body is at rest or moving, it will remain at rest or keep moving unless it is acted upon by an external force. This means that if we could take off into the air, we would keep flying unless another force stopped us (such as gravity or air resistance).
- Force = Mass × Acceleration: To rise into the air quickly, you need a very large force, because the human body is much heavier compared to birds or insects.
- For every action, there is an equal and opposite reaction: This law helps explain why birds can fly while we cannot. Birds push the air downward with their wings; in turn, the air pushes them upward. Unlike our bodies, birds are designed to fly. They possess hollow, lightweight bones, powerful muscles, and wings to lift them up, which gives them enough force to resist gravity.
What is the importance of gravity in our lives?
- Keeping us grounded: Without gravity, we would all float aimlessly. Every step we take depends on Earth’s gravitational force, which keeps us firmly attached to its surface.
- Shaping the solar system: Gravity is the universe’s master architect; it keeps planets in orbit around stars, holds moons around planets, and keeps galaxies intact. Without it, the universe would be nothing more than randomly scattered atoms.
- Foundation of life on Earth: gravity maintains our Planet's atmosphere, trapping oxygen, nitrogen, and water vapor necessary for life.
- Gravity also affects weather patterns and the growth of plants and animals.
- The Moon’s gravitational pull influences the seas on Earth, causing tides.
How did humans achieve the dream of flying?
Humans invented ways to resist gravity in order to fly, such as airplanes, hot air balloons, and rockets. These vehicles rely on powerful engines and aerodynamic designs that help them rise. Children can also use the laws of motion to create flying toys, such as kites, and understand how air and gravity affect their movement. This understanding would allow them to become “physics heroes” even if they cannot fly like superheroes.
References
britannica.com
britannica.com/science
canva.com
spaceplace.nasa.gov