Field
Astronomy & Cosmology
The universe at large scale — how stars live and forge the elements, how we find other worlds, and how space itself is expanding.
19 articles · 38 widgets
Dark Energy: Why the Universe Speeds Up
Dark energy makes up about 68% of the universe and drives its accelerating expansion — a pressure of space itself, opposite in effect to gravitating dark matter.
Orbital Mechanics: The Art of Falling Sideways
Why astronauts float despite full-strength gravity, why reaching orbit means going sideways not up, and why a higher orbit is a slower one.
The Moon: Phases, Faces, and Eclipses
Why lunar phases come from the geometry of the sunlit half we see, why there is no permanently dark side, and why eclipses are rare shadow events.
Comets and Asteroids: The Solar System's Leftovers
Why asteroids are rocky and comets are icy, how a comet grows a coma and tails as its ices sublime, and why a comet's tail always points away from the Sun.
The Hertzsprung–Russell Diagram: Mapping the Stars
The Hertzsprung–Russell diagram plots stellar luminosity against surface temperature, revealing the main sequence, giants, and white dwarfs — and the tracks stars trace as they evolve.
The Sun: A Nuclear Furnace, Not a Fire
The Sun runs on nuclear fusion, not combustion, converting mass to energy — and that energy takes roughly 100,000 years to escape the core before reaching Earth.
The Expanding Universe
Distant galaxies recede faster the farther they are, yet there is no centre and no edge. Run the picture backward and you arrive at a hot dense beginning whose afterglow still fills the sky at 2.725 K.
Telescopes: Gathering Light, Resolving Detail
Why a telescope's real job is gathering light and resolving detail — set by aperture area and diffraction — while magnification is cheap, swappable, and often useless.
Black Holes
How escape velocity reaching the speed of light defines an event horizon, why the Sun would be 3 km across, and what a black hole would — and would not — do to Earth.
Tidal Forces: Why the Moon Raises Two Bulges
Why the Moon raises two ocean bulges (not one), why its weaker pull beats the Sun's, and how the same 1/r³ stretch locks moons and shatters them at the Roche limit.
How We Find Other Worlds
Exoplanets are found not by their light but by the shadow they cast and the tug they exert — a periodic dip in starlight and a Doppler wobble in the star's spectrum.
Where the Elements Come From
The calcium in your bones and the iron in your blood were built by nuclear fusion in stellar cores — a ladder that climbs to iron and then can climb no further.
Gravitational Waves
How accelerating masses shake spacetime, why the resulting strain is only ~10⁻²¹, and how LIGO's laser interferometers detect a ripple that stretches a 4 km arm by less than a thousandth of a proton's width.
The Life Cycle of Stars
How a collapsing cloud of gas becomes a star, why its mass decides everything — including the surprising fact that the biggest stars die youngest — and how it ends.
The Cosmic Distance Ladder
Distance is not something a telescope sees directly. From nearby stars to the edge of the observable universe, every distance is built on a ladder — geometric parallax, then standard candles, then redshift — where each rung borrows its calibration from the one beneath it.
The Cosmic Microwave Background
Point a radio antenna at any patch of empty sky and you pick up the afterglow of the hot dense beginning — a near-perfect 2.725 K blackbody, redshifted from a 3000 K glow, whose faint ripples are the seeds of every galaxy.
Galaxies and Dark Matter
Vera Rubin's flat rotation curves, gravitational lensing, and the Bullet Cluster all point to the same conclusion: galaxies are embedded in vast halos of unseen mass that gravitates but does not shine.
How the Solar System Formed
How a collapsing cloud of gas and dust spun itself into a flat disk 4.6 billion years ago, why the Sun holds almost all the mass, and how the frost line split the planets into small rocky worlds and distant giants.
Neutron Stars and Pulsars
How a dying massive star leaves behind a ~20 km ball as dense as an atomic nucleus, why it spins so fast, and how its sweeping radio beam makes a pulsar tick with clock-like regularity.