LateLight
A planetarium's late-night show. Start on the crown of the dome and scroll. Every step is ten times further out, until the light arriving is two and a half million years old.
One step back.
The planetarium, its roof, the lamps in the car park and the street outside. You are the dot in the middle of the dome, and you stay there all the way out.
- The frame
- 100 m
- Light crosses it in
- 0.33 µs
Three more, and the town is lamps.
Every street is a line of sodium light. The dome is in there, under the centre of the square, and it is already too small to see.
- The frame
- 10 km
- Light crosses it in
- 33 µs
Seven steps from the dome: the Earth.
It is night on this side. The Sun is behind the planet, lighting a thin edge of tomorrow morning.
- Diameter
- 12,742 km
- Light across it
- 42 ms
The Moon's whole orbit in one frame.
Moonlight is sunlight that left the Sun eight minutes ago and bounced. From the Moon to the dome it takes another 1.3 seconds.
- Earth to Moon
- 384,400 km
- Light
- 1.3 s
The Sun is not in the middle.
We are, because this is the frame around the dome. Mercury, Venus, Earth and Mars circle the Sun, 150 million km from where you started.
- Sun to Earth
- 150 million km
- Light
- 8.3 min
Jupiter, Saturn, Uranus, Neptune.
Neptune is 4.5 billion km from the Sun. Sunlight takes four hours to reach it, and Neptune's reflected light takes four more to come back to the dome.
- Sun to Neptune
- 4.5 billion km
- Light
- 4.2 h
A whole light-year, and still only us.
The frame is now 9.5 trillion km wide, the distance light goes in a year. Nothing we have ever launched has crossed it. Voyager 1, the farthest, is less than one light-day out.
- One light-year
- 9.46 trillion km
- Voyager 1
- under 1 light-day
The nearest star is four years away.
Proxima Centauri's light takes 4.2 years to reach the dome. Sirius, the brightest star in our night, takes 8.6. When you look at it tonight, you see it as it was 8.6 years ago.
- Proxima Centauri
- 4.2 light-years
- Sirius
- 8.6 light-years
Our galaxy, with us inside it.
About 100,000 light-years across. The Sun is 26,000 light-years from the centre, out in one of the arms, and the dome is still the dot in the middle of the frame.
- Across
- 100,000 light-years
- Sun to the centre
- 26,000 light-years
Andromeda's light is 2.5 million years old.
It is the farthest thing you can see with your own eyes, and the late show ends here, ten million light-years wide. The light leaving Andromeda tonight arrives in the year 2,500,000. The show is on sooner than that.
- Andromeda
- 2.5 million light-years
- Its light is
- 2.5 million years old