Astronomy deep dive
The watchface shows the sky right now. But the sky changes over time—at scales far beyond human lifetimes. These visualizations let you see what the watchface would show across thousands, millions, and billions of years.
Axial precession
Earth's axis wobbles like a spinning top. The North Celestial Pole traces a circle around the North Ecliptic Pole, completing one full circuit every ~26,000 years.
Why it matters
- •Polaris won't always be the North Star
- •In ~12,000 years, Vega will be the pole star
- •The zodiac signs drift against the calendar (why "Age of Aquarius")
What changes on the watchface
- •The starfield rotates relative to the ecliptic
- •Different stars become circumpolar
- •The Milky Way's position in the sky shifts
Stellar proper motion
Stars are not fixed—they move through the galaxy. Over 200,000 years, constellations dissolve and reform. The Big Dipper becomes unrecognizable. Stars enter and leave the naked-eye visibility threshold.
Why it matters
- •The "fixed stars" are only fixed on human timescales
- •Our constellations are temporary patterns
- •The Sun itself is moving through the galaxy at ~220 km/s
What changes on the watchface
- •Star positions drift
- •Stars brighten as they approach, dim as they recede
- •Familiar asterisms slowly distort
Andromeda approaching
The Andromeda galaxy is approaching the Milky Way. Currently 2.5 million light-years away, it will collide with us in ~4.5 billion years. The Milky Way rotates multiple times before impact—one galactic year takes ~225 million years.
What's shown
- •Andromeda's apparent size grows as distance shrinks
- •The Milky Way band rotates (Sun orbiting the galactic center)
- •Andromeda's position wobbles due to parallax from Sun's orbit
Why it matters
- •Our galaxy is not isolated—it's falling toward its neighbor
- •Individual stars won't collide (too much empty space)
- •The Sun will likely survive, possibly flung to a different orbit
Technical notes
Data sources
- Star positions: HYG database
- Planetary positions: Approximated, verified against astronomy-engine
- Precession model: Standard IAU precession formula
- Proper motion: Individual stellar velocities from catalog data
What's simplified
- Precession visualization ignores nutation (short-term wobble)
- Proper motion doesn't account for radial velocity perfectly
- Andromeda approach uses simplified gravitational model