tag

#cosmology

9 reading cards on “cosmology”, in chronological order. Part of the full archive.

  1. The Cepheid variable V1 in the Andromeda Galaxy, imaged by the Hubble Space Telescope — the same star Edwin Hubble identified in 1923 to prove that spiral nebulae lie beyond the Milky Way.
    2026-05-26

    The Cepheids

    How a pulsating star became the ruler of the universe.

    Some stars do not shine steadily. They swell and contract on a clockwork rhythm — and the rhythm itself, it turns out, tells us how far away they are.
  2. Webb's First Deep Field — galaxy cluster SMACS 0723 imaged by the James Webb Space Telescope, with thousands of galaxies including faint, gravitationally lensed objects from the early universe
    2026-05-08

    Fossil Light

    Astronomy is the only science that cannot observe the present.

    Every photon that reaches a telescope is news from a moment that has already ended. The further the source, the older the news — and the more the universe in front of us is no longer there.
  3. Flammarion engraving of a man peering beyond the celestial sphere
    2026-05-07

    A Thought Experiment from the Middle Ages

    When medieval astronomers reached for the edge of everything.

    Aristotle insisted the universe ended somewhere. His medieval inheritors tried to imagine reaching past that end — and the question reshaped physics.
  4. Galileo demonstrates his telescope to the Doge, as imagined by Giuseppe Bertini
    2026-05-07

    The Great Revolution

    How Kepler and Galileo dismantled fourteen centuries of cosmic certainty.

    Two men, working in different countries with different tools, finished what Copernicus had only begun. Within a single year — 1609 — the heavens stopped being a closed sphere and became something measurable.
  5. An artistic representation of weighing a galaxy
    2026-05-07

    How Much Does a Galaxy Weigh?

    The question is poorly posed — and the answer is stranger than the question.

    There is no scale large enough to weigh a galaxy. The methods we have invented instead reveal that most of the answer is something we cannot see.
  6. Hubble image of the spiral galaxy NGC 5584 used for Cepheid distance calibration
    2026-05-07

    The Cosmic Distance Ladder

    Measuring the universe — one rung at a time.

    Astronomy began as the art of estimating how far things are. The trick is that no single method works at every scale — so we built a ladder.
  7. Panoramic view of the Milky Way from ESO's Paranal Observatory
    2026-05-07

    The Mystery of the Milky Way

    Mapping a city from inside a foggy window.

    We have always lived inside the Galaxy, never outside it. Drawing its map has been like sketching a metropolis from a single window — and the picture is still unfinished.
  8. Detail of Thorvaldsen's Copernicus Monument in front the Polish Academy of Sciences on Warsaw's Krakowskie Przedmieście.
    2026-05-07

    The Legacy of Copernicus

    Five centuries of demotion — from the centre of creation to the periphery of a spiral arm.

    For fourteen centuries the Earth sat at the centre of everything. The book that displaced it was printed the year its author died — and what it began still has not finished.
  9. Hubble high-definition panoramic mosaic of the Andromeda Galaxy showing over 100 million resolved stars
    2026-05-06

    The Andromeda Galaxy

    The nearest thing to a mirror the Milky Way has.

    The brightest object beyond the Milky Way visible to the unaided eye looks like a smudge of light. It is also the only galaxy heading our way — and we have an appointment.