Across the Universe

Outward through the cosmos — from the life and death of a single star to the elements it forges, the worlds around others, the extremes of gravity, and the expansion of everything.

19 articles

1
Astronomy & Cosmology10 min
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.
2
Astronomy & Cosmology10 min
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.
3
Astronomy & Cosmology10 min
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.
4
Astronomy & Cosmology10 min
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.
5
Astronomy & Cosmology10 min
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.
6
Astronomy & Cosmology10 min
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.
7
Astronomy & Cosmology10 min
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.
8
Astronomy & Cosmology10 min
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.
9
Astronomy & Cosmology10 min
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.
10
Astronomy & Cosmology9 min
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.
11
Astronomy & Cosmology10 min
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.
12
Astronomy & Cosmology10 min
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.
13
Astronomy & Cosmology10 min
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.
14
Astronomy & Cosmology10 min
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.
15
Astronomy & Cosmology10 min
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.
16
Astronomy & Cosmology10 min
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.
17
Astronomy & Cosmology10 min
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.
18
Astronomy & Cosmology10 min
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.
19
Astronomy & Cosmology10 min
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.