🌍 GRAVITATIONAL PULL
PAGE 1 OF 5 — WHAT IS GRAVITY?
NEWTON'S GREAT INSIGHT
EVERY MASS ATTRACTS EVERY OTHER MASS
In 1687, Isaac Newton published one of the greatest ideas in the history of science. Every object with mass pulls every other object with mass toward it. The bigger the mass, the stronger the pull. The closer together, the stronger the pull. This invisible force is gravity. The same force that pulls an apple off a tree also keeps the Moon locked in orbit around Earth, and Earth in orbit around the Sun. It is universal — it works everywhere in the universe.
📐 NEWTON'S LAW OF UNIVERSAL GRAVITATION
F = G × (m₁ × m₂) / r² — Force increases with mass, decreases with distance squared
PULL!
GRAVITATIONAL FIELD
🌍 Field lines point toward centre
→ Stronger near the surface
→ Earth: 9.8 m/s² acceleration
→ Stronger near the surface
→ Earth: 9.8 m/s² acceleration
MASS vs WEIGHT
⚖️ Mass = amount of matter (constant)
🌕 Weight = mass × gravity (changes)
🚀 Moon weight = 1/6 of Earth weight
🌕 Weight = mass × gravity (changes)
🚀 Moon weight = 1/6 of Earth weight
PAGE 2 OF 5 — GRAVITY IN SPACE
GRAVITY RULES THE COSMOS
THE MOON NEVER STOPS FALLING
The Moon does not float around Earth by accident — it is constantly falling toward Earth. But because it is also moving sideways at just the right speed, it keeps missing Earth and instead traces a curved orbit. This is what an orbit truly is: a constant state of free fall where you keep missing the ground. The same principle applies to every satellite, every planet, and every star. Gravity is the architect of every orbit in the universe.
ORBIT!
🛰️ ORBITS
🛰️ Orbit = constant free fall
→ Moving sideways fast enough
🌍 Always curves toward Earth
→ Moving sideways fast enough
🌍 Always curves toward Earth
🌊 TIDES
🌕 Moon's gravity pulls oceans
🌊 Near Moon = high tide
↔️ Two bulges — two high tides daily
🌊 Near Moon = high tide
↔️ Two bulges — two high tides daily
🚀 MICROGRAVITY
🧑🚀 ISS astronauts float — not weightless
→ In free fall around Earth
🌍 Gravity still strong at ISS altitude
→ In free fall around Earth
🌍 Gravity still strong at ISS altitude
PAGE 3 OF 5 — FREE FALL & GALILEO'S EXPERIMENT
TERMINAL VELOCITY
🪂 Air resistance increases with speed
⚖️ When drag = gravity → constant speed
💨 Skydiver: ~200 km/h terminal velocity
⚖️ When drag = gravity → constant speed
💨 Skydiver: ~200 km/h terminal velocity
PROJECTILE MOTION
➡️ Horizontal velocity stays constant
⬇️ Vertical: gravity pulls at 9.8 m/s²
🎯 Combined path = parabola
⬇️ Vertical: gravity pulls at 9.8 m/s²
🎯 Combined path = parabola
GALILEO'S DISCOVERY
ALL OBJECTS FALL EQUALLY FAST
Around 1589, Galileo Galilei conducted one of history's most famous experiments at the Leaning Tower of Pisa. He dropped two balls of different masses — a heavy cannonball and a light musket ball — at the same time. They hit the ground simultaneously. This disproved Aristotle's 2,000-year-old belief that heavier objects fall faster. In a vacuum, a feather and a hammer fall at exactly the same rate. Gravity accelerates all objects equally: 9.8 metres per second per second on Earth.
🎯 GRAVITATIONAL ACCELERATION
g = 9.8 m/s² on Earth — the same for all objects regardless of mass
EQUAL!
PAGE 4 OF 5 — EXTREME GRAVITY: BLACK HOLES
WHERE GRAVITY WINS EVERYTHING
NOT EVEN LIGHT CAN ESCAPE
A black hole forms when a massive star collapses under its own gravity. The result is a region of space where gravity is so intense that nothing — not even light — can escape once it crosses the event horizon. Einstein's General Theory of Relativity tells us that gravity is not really a force, but a curvature of space-time caused by mass. A black hole warps space-time so severely that all paths lead inward. Time runs slower near a black hole — a real, measurable effect called gravitational time dilation.
WARP!
🕳️ EVENT HORIZON
🕳️ Event horizon = point of no return
→ Escape velocity exceeds speed of light
🌑 Nothing escapes — not even photons
→ Escape velocity exceeds speed of light
🌑 Nothing escapes — not even photons
⏱️ TIME DILATION
⏱️ Strong gravity slows time down
🛰️ GPS satellites need time corrections
🌑 Near black hole: time nearly stops
🛰️ GPS satellites need time corrections
🌑 Near black hole: time nearly stops
🚀 ESCAPE VELOCITY
🚀 Earth escape velocity: 11.2 km/s
🌕 Moon escape velocity: 2.4 km/s
🕳️ Black hole: exceeds speed of light
🌕 Moon escape velocity: 2.4 km/s
🕳️ Black hole: exceeds speed of light
PAGE 5 OF 5 — GRAVITY ACROSS THE UNIVERSE
THE FORCE THAT SHAPES EVERYTHING
GRAVITY BUILT THE UNIVERSE
Without gravity, the universe would be a cold, dark, formless cloud of hydrogen gas. Gravity pulled that gas together into stars, stars forged the heavier elements, stars exploded and those elements formed planets, and planets formed the conditions for life. Every galaxy, every star system, every moon is a product of gravity. In 2015, LIGO detected gravitational waves — ripples in the fabric of space-time produced by two black holes colliding 1.3 billion light-years away. Gravity connects us to the furthest reaches of the cosmos.
🌊 GRAVITATIONAL WAVES
First detected 14 September 2015 by LIGO — proving Einstein's 1916 prediction correct
COSMOS!
🌌 DARK MATTER
🌌 Galaxies spin faster than expected
→ Invisible mass must provide extra gravity
❓ Dark matter = 27% of universe
→ Invisible mass must provide extra gravity
❓ Dark matter = 27% of universe
💡 WHAT YOU LEARNED
🌍 KEY FACTS
F = G × m₁m₂ / r². All objects fall at 9.8 m/s² on Earth. Orbits are constant free fall. Black holes warp space-time completely. Gravity built the entire universe.
✅ Gravity acts on all mass
✅ Weight = mass × g
✅ Orbit = sideways + falling
✅ Einstein: gravity curves space-time
✅ Weight = mass × g
✅ Orbit = sideways + falling
✅ Einstein: gravity curves space-time
🧠 QUIZ TIME!
GRAVITATIONAL PULL · 5 QUESTIONS
QUESTION 01
According to Newton's Law of Universal Gravitation, what happens to gravitational force if you double the distance between two objects?
QUESTION 02
What is the difference between mass and weight?
QUESTION 03
What did Galileo's Tower of Pisa experiment prove about gravity?
QUESTION 04
Why do astronauts appear to float inside the International Space Station?
QUESTION 05
What is a black hole's event horizon?
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