Why Do We Fall? The Truth About Gravity (That Textbooks Totally Miss)

Introduction — The Mystery of Falling

What goes up, always comes down. Dropped a pen accidentally while writing, it falls down. Try to jump as high as you can, you come back down. An apple detaching from its branch falls toward the Earth — the most famous example that made Newton think about why things always come down.

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Falling feels obvious, but the truth behind it is anything but simple. Why do we or anything fall down? Is gravity a pulling force dragging us down, or is it the shape of space itself guiding motion? What if I tell you that gravity doesn't pull us, but rather space-time guides us to the ground!

This mystery has fascinated scientists for centuries — and the answers have reshaped our understanding of the universe.

What is Gravity?

Growing up, we always heard and learn the Newtonian definition of gravity, and that goes:

Gravity is a force of attraction exerted by an object with mass on any other object with mass.

What does it mean? According to Newton, gravity is an invisible force, with which every object pulls every other object with a certain strength. This strength depends on the mass of the bodies and distance between them. Simple, easy, elegant, and predictive.

But Einstein came and gave us a new perspective towards gravity. He said that mass and energy bend the fabric of space-time itself, and objects simply follow its curve.

So which definition we must agree upon? Newton's or Einstein's. Before coming to the answer, let's go back and see what their thought process regarding the concept of gravity was.

Is Gravity a Force or Curvature of Spacetime?

The textbook story of Newton always started with the red apple that fell on Newton's head and suddenly he got the idea. Well... that doesn't happen really. But it was fun way to remember who discovered the idea of gravity. 

Newton pictured an invisible string that pulls the planets. But Einstein reimagined it as a stage that bends under weight. 

Okay, lets imagine it Einstein's way: place a bowling ball on a trampoline. This bends the trampoline downwards due to its weight. Now, keep some marbles around the bowling ball. 

What happens? The marble starts rolling towards the bowling ball. Not because they are pulled by the ball, but due to the curvature of the trampoline surface. They are simply following the straightest possible path available.

This shifts the Newton's view of gravity as a force to geometry or curvature of space-time. It was revolutionary which explains Mercury’s orbit quirks and predicting phenomena like black holes and gravitational waves.

How Does Gravity Work?

Newton's Gravitation Law

Newton unified the heavens and Earth under one law: universal gravitation, predicting orbits and tides with accuracy. He gave us a precise and beautifully simple equation: 

This formula tells us about the gravitational force between two objects depends on their masses and the distance between them.

• Double the mass? Double the force.
• Double the distance? The force becomes four times weaker.

For the first time, humanity held a single law that explained both the fall of an apple and the motion of the planets. Hence, Newton's universal law of gravitation ruled science for more than 200 years. 

Yet, Newton knew there was something about his theory that didn't quite add up. He knew he hadn't explained everything with his theory. He once wrote, “That one body may act upon another at a distance through a vacuum… is to me so great an absurdity.”

He observed two serious problems which were not solved with the help of his theory.

• Instant action at a distance: Gravity seemed to work instantly — a spooky pull across empty space with no time delay.
• Mercury's strange orbit: Mercury refused to obey Newton’s perfect equations, its orbit wobbling just enough to hint at a deeper law.

Einstein's Space-Time Curve

Einstein replaced this “force” with curved spacetime, and changes what we thought about gravity till now.

Albert Einstein, in his Special Theory of Relativity, found that space and time were interwoven into a

single continuum, which he called space-time.

Later, as he was working out the equations for his General Theory of Relativity, Einstein realized that massive objects create a distortion in the space-time curve. And he used this to describe gravity as a space-time curve caused by mass and energy.

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With this view, a few things got explained with a new perspective:

• Earth doesn’t orbit the Sun because it’s tugged. Earth orbits because the Sun bends spacetime, and Earth follows that bend in the fabric of space and time.
• The Moon moves in that curve - not because it’s pulled, but because that’s the straightest path in warped space
• We fall because we’re following those curves too

Einstein's insight solved the mercury orbit problem also. But the final answer to “how” gravity works still remains one of physics’ deepest quests.

Fun fact: Can Gravity Bends Light?

In 1919: during a solar eclipse, starlight passing near the Sun was observed to bend, exactly as Einstein predicted, revealing gravity's grip in even massless light. This is called gravitational lensing.

Gravity on Earth: Why It Differs by Location

Gravity isn't uniform everywhere. Why? Because Earth is not a perfect sphere, but an oblate spheroid. It flattens at the poles, and bulges at the equator. This leads to the variation of distance of the Earth surface from its center. As a result, the acceleration due to gravity also varies, accordingly.

Let's assume you go to North pole to see the Northern Lights or Aurora Borealis, there you might feel slightly heavier than usual. But if you visit a country on the equator, you'd feel slightly lighter. Hike up the Mount Everest, and gravity weakens a bit with altitude. Even underground density shift can cause subtle variations in the gravity. NASA and Harvard scientists map these differences to study Earth’s interior and even monitor groundwater. 

Gravity in Space

We often see astronauts in real life or movies floating around in space. Does this mean there is no gravity in space? No, there is gravity in space. If so, then how astronauts float like they were not pulled down to something.

There is a term called "zero gravity". But as it sounds, doesn't there is absolute zero gravity. It actually refers to a state of weightlessness — a near-complete absence of weight. Not complete absence of gravity. The more accurate term for zero gravity would be "microgravity" — a very low presence of gravity. Interestingly though, ISS astronauts float not because gravity disappears, but because they are in continuous free fall around the Earth, in the space-time curve really.

Harvard studies the gravitational dynamics which play an important role in keeping the planets and the Moon orbiting, binds the galaxies, and even the expansion of cosmos. Far from absent, gravity is actually the invisible glue of the universe.

Gravity in Everyday Life

We often take gravity for granted, yet it quietly runs the show around us:

• Your weight is just Earth’s mass pulling you by curving spacetime beneath your feet.
• Tides go up and down due to the Moon pulling unevenly on our oceans.
• GPS in your phone only functions because Einstein's time-dilation adjustments are implemented — otherwise, it would be off by kilometers every day.
• Elevators and airplanes make you feel heavier or lighter as gravity combines with acceleration. Hence, you feel something in your gut.
• Stars and galaxies are here because gravity collected clouds of gas and kept them together.
• Black holes are gravity pushed to its craziest limit, holding back even light. 

It's ironic, really, that gravity is the weakest of all the forces — and yet, it's the one that carves out the universe.

Beyond Einstein — Where Textbooks Fall Short

Einstein changed how we see the universe, but even his theory isn’t the final word.

Black holes and Singularities

At a black hole’s heart, Einstein’s equations predict singularities — regions where spacetime bends infinitely. At singularities, physics simply stops working and we don't really know what happens there.

The Quantum Puzzle

General relativity rules the cosmos, while quantum mechanics governs the microscopic. Yet, when you 

try to make them work together, they clash. A unified theory of gravity and quantum mechanics is still missing.

Dark Matter and Dark Energy

Galaxies rotate too fast; the universe expands too quickly. Gravity alone can’t explain it. Scientists suspect invisible “dark matter” and “dark energy” which make up about 95% of the cosmos — which remains unexplored.

Conclusion

• Newton showed gravity as a universal force, binding apples and planets.
• Einstein revealed it as the bending of spacetime, shaping stars and black holes.
• Modern physics still struggles — gravity won’t fit neatly with quantum theory.
• Dark matter & dark energy hint that the story of gravity isn’t finished.

What’s beautiful is that both Newton’s and Einstein’s views remain true in their own ways — one guiding engineer, the other guiding astronomers. Together, they remind us that gravity is not just a “force,” but the invisible architect of the universe: shaping stars, galaxies, and even the flow of time itself.

So, the next time you drop a pen or watch an apple fall, remember — you’re witnessing the same mystery that connects us to black holes, galaxies, and the fate of the cosmos.

FAQ

What is G-Force?

Gravity is usually measured in G-force. A G-force of 1g is measured to be the standard gravity on Earth.

How Much Gravity Can a Human Withstand?

Normally, a human can withstand around G-force of 5g for a prolonged period, while trained fighter pilots endure up to 9g with special suits; beyond that, blood flow fails. 

Further Reading:

• What Would Happen If Gravity Stopped for 5 Seconds? - To see just how important gravity is, imagine if it disappeared for even five seconds.
• How Airplanes Fly: The Physics of Lift, Thrust, Drag, and Weight Explained - Gravity is also one of the four fundamental forces airplanes must overcome to fly.