What is Gravity? 7 Fascinating Insights into the Force That Shapes the Universe

Gravity is one of the most fundamental forces in the universe — a silent architect that shapes galaxies, anchors planets, and gives weight to everything we know. From an apple falling to Earth to the orbit of the Moon and the bending of light around stars, gravity is everywhere. But what is gravity, really? How does it work, and why is it so crucial to understanding the universe?

In this comprehensive guide, we explore what is gravity in depth — from its historical origins and scientific explanations to its role in modern physics, astronomy, and everyday life.

READ: What Is an Electric Field?

The Meaning and Definition of Gravity

Gravity is the natural force of attraction between all objects that have mass. Every particle in the universe pulls every other particle toward itself with a force that depends on their masses and the distance between them.

In simpler terms, gravity is what causes an apple to fall from a tree, what keeps the Moon orbiting the Earth, and what keeps our feet firmly on the ground.

According to Sir Isaac Newton, gravity is a universal force acting between all matter. He proposed that every mass attracts every other mass through a force directly proportional to their product and inversely proportional to the square of the distance between them.

Newton’s Law of Universal Gravitation:

Where:

• ( F ) = gravitational force
• ( G ) = gravitational constant
• ( m₁ ) and ( m₂ ) = masses of the two objects
• ( r ) = distance between their centers

This simple formula became the cornerstone of classical mechanics, helping scientists explain planetary motion and the behavior of falling objects.

The Story Behind the Discovery of Gravity

The Apple Story: Newton’s Inspiration

Legend has it that Sir Isaac Newton began pondering what is gravity after observing an apple fall from a tree in 1665. He wondered why the apple fell straight down instead of sideways or upward. This question led him to the realization that the same force pulling the apple to the ground might also be responsible for the motion of the Moon and the planets.

Einstein’s Revolution: General Relativity

Centuries later, Albert Einstein offered a groundbreaking new understanding of what is gravity with his Theory of General Relativity (1915). Einstein proposed that gravity is not a force, as Newton described, but rather a curvature of spacetime caused by massive objects.

In Einstein’s view, objects like Earth bend the fabric of spacetime around them, and this curvature directs the motion of other bodies. Imagine placing a heavy ball on a stretched rubber sheet — smaller balls placed nearby will roll toward it because the sheet curves.

This theory not only redefined what is gravity but also predicted phenomena like gravitational waves and black holes — concepts proven true through modern astronomical observations.

The Science Behind Gravity

Gravitational Force and Acceleration

On Earth, gravity gives everything weight. The acceleration due to gravity on our planet’s surface is approximately 9.8 m/s². This means that any freely falling object increases its velocity by 9.8 meters per second every second (ignoring air resistance).

Universal Gravitational Constant

The gravitational constant (G) is a key part of understanding what is gravity in quantitative terms. It has a value of approximately:

This incredibly small number reflects how weak gravity is compared to other fundamental forces — for example, the electromagnetic force is vastly stronger.

The Role of Gravity in the Universe

Gravity and Planetary Motion

Gravity keeps the planets in their orbits around the Sun. The balance between the Sun’s gravitational pull and the planets’ inertia prevents them from flying off into space.

Gravity and Stars

Gravity plays a crucial role in the formation and life cycle of stars. Clouds of gas and dust collapse under their own gravity to form stars, and when stars die, gravity can cause them to collapse into white dwarfs, neutron stars, or even black holes.

Gravity and Galaxies

Galaxies themselves are massive structures held together by gravity. Dark matter, an invisible form of matter that interacts only gravitationally, is believed to be the primary glue that holds galaxies and galaxy clusters together.

The Effects of Gravity on Earth

Gravity and Tides

The gravitational pull of the Moon (and to a lesser extent, the Sun) causes tides in Earth’s oceans. When the Moon is directly overhead or on the opposite side of Earth, its gravity pulls the water, creating high and low tides.

Gravity and Time

Einstein’s theory also showed that gravity affects time. The stronger the gravitational field, the slower time passes — a phenomenon known as gravitational time dilation. This has been confirmed using extremely precise atomic clocks on Earth and in orbit.

Gravity in Everyday Life

From walking and running to the way airplanes fly, gravity influences nearly every physical action we take. Without it, life as we know it would be impossible — no atmosphere, no oceans, and no stable surface to stand on.

Comparing Theories of Gravity

Theory	Main Concept	Scientist	Year
Newton’s Law	Force between masses	Isaac Newton	1687
Einstein’s Relativity	Curvature of spacetime	Albert Einstein	1915
Quantum Gravity (Emerging)	Gravity as quantum phenomenon	Ongoing	21st Century

Modern physics is still searching for a unified theory that connects quantum mechanics with general relativity — something that could finally explain what is gravity at the smallest and largest scales.

Gravity VS Electromagnetism

1. Gravity Is Extremely Weak Compared to Magnetic Force

Although gravity acts between all masses, it’s astonishingly weak compared to other fundamental forces.

Here’s how weak it is:

• The gravitational attraction between two people standing next to each other is practically zero — far weaker than the force it takes to lift a strand of hair.
• The magnetic force between two small magnets can easily overpower gravity.

To give perspective: the Earth’s gravity is strong enough to hold oceans and the atmosphere, yet a tiny refrigerator magnet can lift a paperclip against the entire gravitational pull of Earth!

This happens because gravity’s strength depends on mass, while magnetism can be much stronger even on a small scale.

2. Gravity Only Attracts — Magnetism Can Attract or Repel

Gravity is always attractive. There’s no such thing as “negative mass” that repels other matter.
Magnetism, on the other hand, comes from electric charges in motion and has two poles — north and south.

• Like poles repel each other.
• Opposite poles attract.

So, magnetic force has both push and pull, while gravity only pulls.

3. Masses Are Too Small to Create Noticeable Gravity

Even though every object attracts every other object, the force is proportional to their masses.

The equation for gravitational force is:

Here, (G = 6.674 × 10^-11), a tiny number. That means unless at least one of the masses (like Earth) is enormous, the resulting force is negligible.

For example:

• Two 1 kg objects, 1 meter apart, attract each other with only 6.67 × 10⁻¹¹ newtons — basically nothing.
  That’s why you don’t feel objects “sticking” to you gravitationally.

4. Magnetic Force Comes from Charge, Not Mass

Magnetism arises from electrons in motion — spinning or orbiting around atoms. That’s why only certain materials (like iron, nickel, cobalt) can be magnetic: their electrons align in a specific way.

Gravity, however, depends only on mass and distance. Every atom contributes to gravity, but since the gravitational constant is so small, it takes an entire planet to make the effect noticeable.

5. Electromagnetic Forces Can Cancel; Gravity Cannot

Most objects are electrically neutral — they have equal positive and negative charges, so their magnetic effects cancel out.
But gravity never cancels, because there’s no opposite “gravitational charge.” That’s why gravity dominates at large scales (planets, stars, galaxies), even though it’s weak individually.

In Short:

Gravity doesn’t make everyday objects stick together because:

• It’s much weaker than magnetic or electric forces.
• It depends on mass, not charge or magnetic properties.
• The masses of ordinary objects are too small to produce noticeable attraction.

Yet, on cosmic scales, gravity becomes the ruling force, shaping galaxies, stars, and the universe itself.

READ: How Do Magnets Work?

Why the Moon Doesn’t Stick to the Earth Like a Magnet

1. The Moon Is Constantly Moving

The key reason the Moon doesn’t crash into Earth is motion.
The Moon is traveling sideways (around Earth) at approximately 1 kilometer per second.

So while Earth’s gravity is constantly pulling the Moon inward, the Moon’s sideways velocity keeps it moving forward. The result? It falls toward Earth continuously but never actually hits it — it keeps missing.

That’s what an orbit really is: a perfect balance between gravitational pull and forward motion.

In simple terms:
Gravity pulls the Moon in; motion carries it around.

2. Gravity Isn’t Like Magnetism

Gravity and magnetism might both cause attraction, but they work in completely different ways:

Feature	Gravity	Magnetism
Depends on	Mass	Electric charge & motion of electrons
Always attracts?	Yes	No (can attract or repel)
Acts between	All matter	Magnetic materials only
Can be blocked?	No	Yes (by non-magnetic materials)

So the Moon doesn’t “stick” to Earth because gravity isn’t a sticky force — it’s a curving, pulling influence that acts across space, not a surface-level attachment like magnetism.

3. There’s a Perfect Balance of Forces

If the Moon were moving any slower, Earth’s gravity would pull it in — and it would eventually crash.
If it were moving any faster, it would escape Earth’s gravity completely.

Right now, the balance between the Moon’s speed and Earth’s gravitational pull keeps it in a stable orbit about 384,400 km away.

4. Gravity Doesn’t Work Like a “Snap-On” Force

Magnetism acts strongly only over small distances and can make things physically touch or stick.
Gravity, by contrast, acts over huge distances but with very gentle strength.
Even though Earth’s gravity is strong enough to hold the Moon in orbit, it’s not strong enough to pull it straight down, because the Moon’s motion resists that pull perfectly.

5. You Can Think of It Like This

Imagine swinging a ball tied to a string around your head:

• The string tension is like gravity — always pulling inward.
• The ball’s motion keeps it circling instead of falling in.

If you cut the string, the ball flies away — just like the Moon would if gravity suddenly stopped acting.

In Summary:

The Moon doesn’t stick to the Earth like a magnet because:

1. It’s moving fast enough sideways to stay in orbit.
2. Gravity isn’t a contact or “sticky” force — it bends motion, not stops it.
3. There’s a delicate balance between the Moon’s inertia (motion) and Earth’s gravity.

So instead of colliding, the Earth and Moon are locked in an elegant gravitational dance, circling endlessly through space.

Gravity in Different Educational Syllabi

O-Level Physics

Students at the O-level learn what is gravity primarily through Newtonian physics. The syllabus typically includes:

• Definition of gravity as a force of attraction
• Weight and mass relationship: ( W = mg )
• Gravitational field strength (9.8 N/kg)
• Simple calculations involving gravitational force

A-Level Physics

At the A-level, the concept deepens to include:

• Newton’s law of gravitation
• Gravitational potential and potential energy
• Gravitational field strength in planetary contexts
• Orbital motion and satellite calculations

AP Physics

The Advanced Placement (AP) Physics curriculum includes:

• Universal law of gravitation and applications
• Relationship between gravitational and centripetal force
• Gravitational potential energy
• Understanding satellite motion and escape velocity

IB Physics

In the International Baccalaureate (IB) program, what is gravity is explored conceptually and mathematically through:

• Newton’s laws and gravitational field equations
• Potential and field diagrams
• Orbital mechanics
• Relativistic effects and modern research in gravity

Modern Research and Discoveries in Gravity

Gravitational Waves

In 2015, scientists at LIGO (Laser Interferometer Gravitational-Wave Observatory) directly detected gravitational waves for the first time — ripples in spacetime caused by massive cosmic events like black hole mergers.

This discovery was one of the greatest confirmations of Einstein’s theory and opened a new way to study the universe through gravitational astronomy.

Quantum Gravity and String Theory

Physicists are working to reconcile quantum mechanics with general relativity. Theories like string theory and loop quantum gravity attempt to describe gravity in terms of quantum particles — possibly gravitons, hypothetical carriers of the gravitational force.

Gravity and Dark Energy

Recent cosmological studies suggest that gravity might interact with dark energy, a mysterious force causing the accelerated expansion of the universe. Understanding this relationship could answer one of science’s biggest questions: What is gravity’s ultimate nature?

The Importance of Gravity

Gravity is much more than just a force; it’s the framework of the cosmos. Without gravity:

• The Earth wouldn’t have an atmosphere.
• The Sun wouldn’t hold its planets.
• Galaxies wouldn’t exist.
• Even light would travel differently.

In essence, gravity is the cosmic glue that holds everything together — the architect of space and time.

The Future of Gravity Research

Scientists continue to push the boundaries of what we know about gravity through experiments and observations:

• Space missions studying gravitational fields of other planets
• Quantum gravity simulations
• Black hole imaging projects
• Experiments with antimatter and microgravity in orbit

Each discovery brings us closer to a complete understanding of what is gravity and its fundamental role in shaping reality.

FAQs

What is gravity in simple terms?

Gravity is the force that pulls everything with mass toward everything else. It keeps us on the ground and makes planets orbit stars.

Who discovered gravity?

Sir Isaac Newton is credited with formulating the law of universal gravitation, though the concept existed earlier in basic forms.

What is the acceleration due to gravity on Earth?

It’s approximately 9.8 m/s², meaning any freely falling object increases speed by about 9.8 meters per second every second.

What is the difference between weight and mass?

Mass is the amount of matter in an object, while weight is the gravitational force acting on that mass. On Earth, weight = mass × 9.8 N/kg.

How did Einstein change our understanding of gravity?

Einstein’s general theory of relativity explained gravity not as a force but as a curvature of spacetime caused by massive objects.

Does gravity exist in space?

Yes. Gravity exists everywhere — even in outer space. Astronauts experience microgravity because they are in continuous free fall around Earth.

What is gravitational potential energy?

It’s the energy an object possesses due to its position in a gravitational field. The higher the object, the more potential energy it has.

Can gravity be shielded or blocked?

No. Unlike electromagnetic forces, gravity cannot be shielded or blocked by any material. It acts universally across space.

What are gravitational waves?

They are ripples in spacetime caused by massive cosmic events, such as colliding black holes or neutron stars.

Why is gravity important for life on Earth?

Gravity keeps the atmosphere, oceans, and living beings anchored. Without it, Earth couldn’t sustain life.