THE SOLAR SYSTEM
From the blazing Sun at the center to icy worlds at the edge — our solar system is a 4.5 billion year old neighbourhood full of wild, totally different worlds.
A giant ball of nuclear fusion 1.3 million times the size of Earth. Watch how the Sun was born 4.6 billion years ago and how it powers every living thing on our planet with light and heat.
Closest to the Sun but NOT the hottest planet. No atmosphere to trap heat — so it roasts at 430°C by day and freezes at -180°C at night.
The hottest planet — hotter than Mercury despite being twice as far from the Sun. A runaway greenhouse effect cooked it alive billions of years ago. Earth's climate warning!
The only known planet with liquid water on its surface, a protective magnetic field, an oxygen atmosphere, and billions of living things. Why Earth is the lucky one.
Mars is red because its surface is covered in rust. It has the tallest volcano in the solar system and ancient river valleys — evidence it was once wet and warm.
A cloud of gas and dust collapsed under gravity. The centre became the Sun; the rest clumped into planets. The birth story of our cosmic neighbourhood.
The asteroid belt contains millions of rocky objects — the remains of a planet that never formed because Jupiter's gravity kept disrupting it.
A donut-shaped region beyond Neptune containing thousands of icy bodies including Pluto and Eris. The source of most short-period comets.
A vast spherical shell of icy bodies surrounds the solar system at up to 2 light-years distance. Long-period comets like Hale-Bopp come from here.
Planets are constantly falling toward the Sun — but moving sideways fast enough that they keep missing it. The elegant balance that creates a stable orbit.
Planets orbit in ellipses, not circles. They move faster when closer to the Sun and slower when farther. Kepler worked this out 100 years before Newton explained why.
The Sun constantly fires a stream of charged particles into space. Earth's magnetic field deflects most of it — but some enters at the poles and creates the Aurora.
Massive explosions on the Sun can send billions of tonnes of plasma toward Earth. In 1989 a solar storm knocked out Quebec's power grid for 9 hours.
Seasons aren't caused by distance from the Sun — Earth's tilted axis means different hemispheres receive more sunlight at different times of year.
The Moon's gravity pulls Earth's oceans — creating a bulge on the side facing the Moon and another bulge on the opposite side. How tides rise and fall twice daily.
Earth spins once every 24 hours. The side facing the Sun has day; the side away has night. Why the Sun rises in the east — always, everywhere on Earth.
Jupiter is so big it could fit 1,300 Earths inside. The Sun could fit 1,000 Jupiters. The scale of the solar system is so extreme our brains can't really grasp it.
The four inner planets are rocky with solid surfaces. The four outer planets are giants of gas and ice with no solid ground to stand on. Why the divide exists.
Uranus was found by accident in 1781. Neptune was predicted mathematically before anyone looked for it. Pluto was found by a 23-year-old farm boy in 1930.
GAS GIANTS & OUTER WORLDS
So massive it contains more material than all other planets combined. Jupiter acts as the solar system's vacuum cleaner, pulling in asteroids that would hit Earth.
A storm bigger than Earth has been raging on Jupiter for at least 350 years. And it's slowly shrinking. What's happening inside this ancient planetary hurricane?
Saturn's iconic rings are made of billions of ice chunks and rocks. They're 282,000 km wide — yet only 10 to 100 metres thick. How did they form? And why are they disappearing?
Uranus spins on its axis tilted nearly 98 degrees. One pole faces the Sun for 42 years straight. The strangest rotation in the solar system — and nobody knows why.
The windiest planet — storms reaching 2,100 km/h. Deep inside, pressure may squeeze carbon into actual diamonds that rain down through the atmosphere.
In 2006 Pluto was demoted from planet status. Meet the five confirmed dwarf planets — and understand the debate that still divides astronomers.
Saturn has a hexagonal storm at its north pole the size of two Earths. It's so light it would float in water. The most visually stunning planet in the solar system.
Jupiter's magnetic field is the largest structure in the solar system — extending millions of kilometres. It creates radiation belts deadly to spacecraft.
Uranus and Neptune are "ice giants" — different from gas giants. Their interiors contain icy materials under crushing pressure. Only Voyager 2 has visited both.
Triton orbits Neptune backwards — captured from the Kuiper Belt. Tidal forces are slowly decelerating it; in 3.6 billion years it will spiral in and be destroyed.
Titan is the only moon with a thick atmosphere and liquid on its surface. The liquid is methane, not water — but it rains, pools in lakes, and flows in rivers.
Saturn isn't the only ringed planet. Jupiter, Uranus, and Neptune all have rings — just much fainter. Why rings form and why Saturn's are so spectacularly visible.
Io is the most volcanically active body in the solar system. Jupiter's tidal forces flex the moon like a stress ball — generating enough heat to keep the interior molten.
Deep inside Jupiter, hydrogen is squeezed so hard it becomes metallic — conducting electricity. The extreme interiors of gas giants are unlike anything on Earth.
Jupiter and Saturn may have formed closer to the Sun then migrated outward — disrupting the solar system and scattering asteroids. The Grand Tack hypothesis.
MOONS, ASTEROIDS & SMALL BODIES
Our Moon was formed when a Mars-sized object smashed into Earth 4.5 billion years ago. It controls our tides, stabilises our axis, and may have made life possible.
Io is covered in active volcanoes. Europa has a vast ocean under its ice — possibly harbouring life. Ganymede is larger than Mercury. Jupiter's moons are worlds.
Millions of rocky leftovers from the solar system's formation. Some contain more gold and platinum than humanity has ever mined. And some are on a collision course with Earth.
Ancient travellers from the outer solar system. Their tails always point away from the Sun — not behind them. Halley's Comet has been recorded for over 2,000 years.
A total solar eclipse is one of the most spectacular events in nature. It's only possible because the Moon and Sun appear exactly the same size in our sky.
Europa has more liquid water than all of Earth's oceans — hidden under a crust of ice. One of the best candidates for life in our own solar system.
The Moon doesn't change shape — we see different amounts of its lit face as it orbits Earth. The 29.5-day cycle that drives calendars and animal behaviour.
In 2013 a 20-metre meteor exploded over Chelyabinsk, Russia, injuring 1,500 people. NASA tracks thousands of near-Earth objects and plans how to deflect them.
Every year about 50,000 meteorites fall to Earth. Most land in the ocean or remote areas. Some contain material older than the solar system — 4.6 billion years old.
The rings are made of 99% water ice. Cassini spacecraft flew through the gap between the rings and Saturn. Shepherd moons use gravity to keep ring edges sharp.
Geysers of water ice shoot 500 km into space from Saturn's moon Enceladus. Beneath its icy surface is a warm salty ocean — one of our best hopes for finding life.
In 2022 NASA deliberately crashed a spacecraft into an asteroid at 22,500 km/h — and successfully changed its orbit. The first test of planetary defence technology.
Saturn has 146 confirmed moons. Jupiter has 95. Earth has 1. Mars has 2 tiny captured asteroids. How moons form, how they're counted, and why outer planets have so many.
In 2006 Pluto was reclassified as a dwarf planet — and many people were outraged. The New Horizons flyby in 2015 revealed a surprisingly active, complex world.
Shooting stars are grains of space dust burning up 80 km above your head. Every August the Perseid shower produces 100 meteors per hour — all from one comet's trail.
STARS & NIGHT SKY
Every star is a giant ball of hydrogen fusing into helium. The energy released travels for millions of years before bursting out as light. How stars shine.
Blue stars are the hottest (30,000°C). Red stars are the coolest (3,000°C). Our Sun is yellow-white. How to read a star's temperature from its colour.
Ancient peoples drew pictures between the stars to navigate and tell stories. 88 official constellations cover the entire sky — each one a window into ancient culture.
Our galaxy is a barred spiral 100,000 light-years across. Our solar system sits on a minor arm, two-thirds from the centre. We've never seen it from outside.
When a massive star dies, it explodes with the energy of a billion suns. The explosion forges heavy elements like gold and iron — and scatters them to form new planets.
Stars don't actually twinkle — their light shimmers as it passes through Earth's turbulent atmosphere. From space, stars shine steadily. Why planets don't twinkle.
Stars are born in nebulae, spend billions of years fusing hydrogen, then die in ways that depend on their mass. Our Sun will become a red giant and swallow Earth in 5 billion years.
Polaris sits almost directly above Earth's North Pole — so it barely moves in the sky. Sailors used it to navigate for thousands of years. How to find it tonight.
The nearest star beyond our Sun is Proxima Centauri — 4.2 light-years away. Even at the speed of light it would take 4.2 years to reach. How astronomers measure star distances.
When our Sun runs out of hydrogen it will expand to swallow Mercury and Venus. Then it will shed its outer layers and leave behind a slowly cooling white dwarf.
A neutron star packs more mass than the Sun into a sphere 20 km wide. A teaspoon of its material weighs 10 million tonnes. Some spin 700 times per second.
More than half of all stars are in binary or multi-star systems. Two stars orbit each other. Some are so close they exchange material — occasionally triggering explosions.
There are an estimated 2 trillion galaxies in the observable universe. Spiral galaxies like ours, giant ellipticals, and irregular dwarfs. How they form and merge.
Andromeda is the most distant object visible to the naked eye. It's heading toward us at 110 km/s and will collide with the Milky Way in 4.5 billion years.
The Pillars of Creation are columns of gas and dust where new stars are forming. Nebulae are the stellar nurseries where material collapses under gravity to light up.
Charged particles from the Sun spiral into Earth's atmosphere near the poles. Their collisions with gas molecules produce curtains of green, red, and purple light.
Galaxies spin too fast — they should fly apart by Newton's laws. Some invisible substance is providing extra gravity. We call it dark matter, but we don't know what it is.
Different constellations are visible in different seasons and hemispheres. Orion dominates winter skies in the north. Scorpius the summer. A beginner's guide to the night sky.
If UY Scuti replaced our Sun, it would extend beyond Jupiter's orbit. The largest known stars are so enormous they're unstable — shedding mass and slowly disintegrating.
Stars are often born in clusters from the same nebula. The Pleiades is an open cluster 440 light-years away. Globular clusters contain hundreds of thousands of ancient stars.
Massive stars burn bright but die young — just millions of years. Small red dwarfs burn so slowly they'll outlive the universe. Our Sun has about 5 billion years left.
If the universe is infinite and full of stars, why isn't the night sky blazing bright? The answer involves the finite age of the universe and the expansion of space.
Some stars pulse in brightness on a regular cycle. Cepheid variables are used as "standard candles" — their cycle reveals their true brightness, and thus their distance.
How do astronomers measure billions of light-years? A series of overlapping methods — each one calibrated against the previous — builds a ladder out to the edge of the universe.
You don't need a telescope to start stargazing. The Moon, Jupiter, and the Milky Way are all visible with the naked eye. A beginner's guide to getting started tonight.
SPACE EXPLORATION
Eight years after Kennedy's promise, 600 million people watched Neil Armstrong step onto the Moon. How NASA pulled off the most audacious mission in human history.
Mars is our next-door neighbour and our biggest space dream. From the first flyby in 1965 to the Perseverance rover today — here's the epic story of Mars exploration.
The size of a football field, orbiting at 28,000 km/h. Humans have lived there continuously since 2000. What life is really like when up and down no longer exist.
Car-sized robots driving across an alien planet, drilling rock samples, and flying the first helicopter on another world. The robots exploring Mars so humans don't have to — yet.
The largest space telescope ever built showed us galaxies from 300 million years after the Big Bang. Its first images rewrote what we thought we knew about the early universe.
Launched 47 years ago on a 5-year mission — still transmitting from 23 billion kilometres away. Voyager 1 is humanity's farthest-reaching achievement.
On 12 April 1961, Yuri Gagarin became the first human in space. His single orbit lasted 108 minutes. He was 27 years old. The world changed forever that morning.
Sputnik in 1957 shocked America. Seven satellites, four dogs, two men, one Moon landing — the 12-year race between superpowers that pushed humans into space.
For every action there's an equal and opposite reaction. Hot gas shoots out the bottom, the rocket goes up. How multi-stage rockets shed mass to reach orbital velocity.
A satellite is just an object moving sideways so fast it keeps missing the Earth as it falls. There are over 7,000 operational satellites — enabling GPS, weather, and internet.
No fridge, no convection oven, no refrigerator. Food must be shelf-stable for months, nutritious, and crumb-free — floating crumbs clog equipment and eyes.
In microgravity, muscles waste and bones thin. Fluid shifts to the head making faces puffy. Astronauts exercise 2 hours daily just to stay healthy enough to walk on return.
A spacesuit is a personal spacecraft. It maintains pressure, provides oxygen, regulates temperature from -160°C to 120°C, and shields against micrometeoroids.
Hubble's famous first images were blurry — a polishing error in its mirror. Astronauts flew up to fit corrective lenses in 1993. Then it became the most important telescope ever.
SpaceX made rockets reusable — landing boosters back on their launchpads. This reduced launch costs by 90%. The privatisation of space that is reshaping the industry.
17 Apollo missions. 6 successful Moon landings. 12 humans walked on the Moon. Apollo 13 nearly ended in disaster. The complete story of humanity's greatest adventure.
The journey takes 7 months. Mars has no breathable air, intense radiation, and temperatures of -60°C. How humanity plans to send humans there — and keep them alive.
Voyager carries a gold-plated record containing music, greetings in 55 languages, and sounds of Earth. A message in a bottle thrown into the cosmic ocean.
Over 27,000 pieces of debris orbit Earth at 28,000 km/h. A paint fleck at that speed hits with the force of a bullet. The growing problem that threatens all future spaceflight.
NASA's Artemis programme aims to return humans to the Moon by 2026. China has landed rovers on the Moon's far side. The new geopolitical competition in space is accelerating.
Spacewalks take hours of preparation. Astronauts wear gloves so thick they can barely grip — yet must perform delicate repairs on billion-dollar equipment in complete silence.
A telescope collects more light than your eye can. Reflecting telescopes use mirrors; refractors use lenses. Why bigger aperture always beats higher magnification.
Mars's atmosphere is 95% CO₂ and only 1% the pressure of Earth's. A global dust storm in 2018 killed the Opportunity rover by blocking sunlight to its solar panels.
The Moon has water ice at its poles. Future bases could mine it for drinking water and rocket fuel. But radiation levels are 200× higher than Earth — an enormous challenge.
Radio telescopes detect invisible signals from pulsars, galaxies, and the cosmic microwave background. Some signals are so regular they were initially thought to be alien.
EXOPLANETS & ALIEN LIFE
Over 5,500 planets orbiting other stars — some covered in lava, some raining glass sideways, some with two suns. The universe is overflowing with worlds unlike our own.
With 2 trillion galaxies each containing hundreds of billions of stars, the odds say life should exist elsewhere. Why haven't we found it — and where should we look?
Since 1960 scientists have pointed radio telescopes at the sky listening for signals. In 1977 they detected something extraordinary — and never heard it again.
The universe is 13.8 billion years old. Alien civilisations should have had time to spread everywhere. So why is the sky completely silent? The most unsettling question in science.
The Kepler space telescope found thousands of planets by watching for tiny dips in starlight as planets cross in front of their stars. A method that changed astronomy forever.
The habitable zone is the region around a star where liquid water could exist on a planet's surface. Thousands of planets sit in their star's habitable zone.
Bacteria thrive in boiling acid vents. Tardigrades survive in the vacuum of space. Life on Earth exists in every extreme — expanding where else it might exist.
Frank Drake devised an equation in 1961 to estimate how many communicating alien civilisations exist. Each variable is debated. The answers range from 1 to millions.
Oxygen in an atmosphere would be a strong biosignature — it's too reactive to stay there without constant biological replenishment. James Webb can already detect this.
When the first exoplanets were discovered, they were giant Jupiter-sized planets orbiting closer than Mercury. Their existence overturned all theories of planetary formation.
An astronomer monitoring radio signals saw something so significant he wrote "Wow!" next to the printout. Lasted 72 seconds. Never repeated. Still unexplained.
Two moons in our own solar system have subsurface oceans with the right chemistry for life. NASA's Europa Clipper mission launched in 2024 to investigate.
Proxima Centauri b orbits our nearest stellar neighbour in the habitable zone. It's the closest possible world we could ever reach. Whether it has an atmosphere is unknown.
Seven rocky Earth-sized planets orbit a single red dwarf star 40 light-years away. Three are in the habitable zone. The most exciting planetary system ever discovered.
Mars could theoretically be terraformed — its atmosphere thickened, its ice melted. It would take thousands of years. Whether it should be done is a profound ethical question.
BIG SPACE QUESTIONS
A place where gravity is so strong that nothing — not even light — can escape. How black holes form, how big they get, and what would happen if you fell into one.
The observable universe is 93 billion light-years wide — but the actual universe could be infinite. Numbers so large that even scientists struggle to comprehend them.
Three leading theories for the end of everything. The most likely — Heat Death — means the universe slowly fades into cold, dark, perfect stillness. Trillions of years from now.
The nearest star is 4.2 light-years away. At our fastest spacecraft speed that's 75,000 years of travel. The science of interstellar travel — what's possible and what isn't.
Our physics breaks down at the moment of the Big Bang. The concept of "before" may not even exist. The honest answer — and the wildest theories that try to fill the void.
It would take 8 minutes before we even knew. Then Earth would fly off into space in a straight line. A step-by-step countdown of exactly what would happen — and when.
13.8 billion years ago, all matter and energy exploded from a single point. The evidence: the universe is still expanding, and the Big Bang's afterglow still fills the sky.
The universe is not just expanding — it's expanding faster and faster. Something is pushing it apart. We call it dark energy. It makes up 68% of everything but nobody knows what it is.
Einstein's relativity allows time dilation — clocks on fast spacecraft run slower. Travelling forward in time is physically possible. Backward is much more controversial.
General relativity allows for wormholes — tunnels connecting distant regions of spacetime. Whether they could be stable, large enough, or traversable is deeply uncertain.
Three different theories in physics independently suggest parallel universes might exist. The many-worlds interpretation of quantum mechanics says every quantum event forks reality.
Even "empty" space is filled with quantum fluctuations — virtual particles popping in and out of existence. Space is not nothing; it has energy, structure, and geometry.
Edwin Hubble noticed in 1929 that galaxies were moving away — the farther, the faster. The cosmic microwave background radiation is the relic heat from the Big Bang itself.
A solar eclipse happens when the Moon blocks the Sun. A lunar eclipse when Earth's shadow falls on the Moon. The perfect coincidence of size and distance that makes totality possible.
The observable universe has a horizon — beyond it, light hasn't had time to reach us. But the actual universe may extend infinitely. How cosmologists try to measure its shape.
Cosmic inflation may have produced an infinite number of bubble universes, each with different physics. Our universe's constants are so perfectly tuned for life — maybe we won the lottery.
Evolution responds to environment. Aliens on a high-gravity world would be short and squat. On a low-oxygen world, enormous and slow-moving. The science of speculative biology.
In 5 billion years our Sun will exhaust its hydrogen, expand into a red giant swallowing Earth, then shed its outer layers as a planetary nebula, leaving a white dwarf behind.
By measuring the universe's expansion rate and working backwards, and by studying the oldest stars and the CMB temperature, cosmologists pinned the universe's age to 13.8 billion years.
A magnetar's magnetic field is a quadrillion times stronger than Earth's. A quasar outshines an entire galaxy. The most violent, hot, and strange objects physics allows.
AMAZING SPACE FACTS
Saturn is the least dense planet — less dense than water. If you had a bathtub big enough, it would float. The extraordinary lightness of a planet made mostly of hydrogen.
Deep inside Neptune and Uranus, pressures are so extreme that carbon atoms are squeezed into diamonds. In 2017 scientists recreated this in a lab. It actually works.
Venus takes 243 Earth days to rotate once — but only 225 days to orbit the Sun. Its day is literally longer than its year. The strangest timekeeping in the solar system.
Every second, the Sun converts 4 million tonnes of mass into energy via E=mc². It has been doing this for 4.6 billion years — and has enough fuel for another 5 billion.
Sound needs a medium to travel through. Space is a vacuum. No matter how massive the explosion, there is no sound in space. The Hitchhiker's Guide was almost right.
Without wind or rain, nothing erodes on the Moon. Neil Armstrong's footprints are still there — exactly as he left them in 1969. They will remain for millions of years.
HD 189733b rains molten glass sideways at 8,700 km/h. The "glass" is actually tiny silicate particles in its atmosphere. The most terrifying weather in the known universe.
Water ice exists on the Moon, Mars, comets, asteroids, Europa, Enceladus, and in giant clouds between stars. Water is not special to Earth — it's the universe's most common liquid.
Einstein predicted that gravity slows time. Near a black hole, a clock ticks measurably slower than one far away. This isn't science fiction — GPS satellites must correct for it.
Olympus Mons on Mars is 21 km tall — nearly 3 times Everest — and 600 km wide. It's so wide you couldn't see the edges from the top because they'd be below the horizon.
When a massive star collapses, conservation of angular momentum spins the resulting neutron star to incredible speeds. Some spin 716 times per second — and are incredibly precise clocks.
Every carbon atom in your body was forged in a star. The calcium in your bones came from a supernova explosion billions of years ago. You are literally made of the universe.
The Boomerang Nebula, 5,000 light-years away, is −272°C — colder than the cosmic background radiation and the coldest known natural place in the universe.
The Big Bang didn't happen at a point in space — it happened everywhere at once. The universe is expanding from every point simultaneously. There is no edge and no centre.
Saturn floats. The Moon is drifting away. Space smells like burnt steak. Pluto hasn't completed an orbit since its discovery. All true. The most jaw-dropping facts in the cosmos.