How long does light take to get here?
Every telescope is a time machine. What you see is always what was, by exactly the light travel time.
Almost exactly a from the Sun
500 s is longer than 3 of the 9 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| from the Moon | 1.28 s | 391× | |
| from Mars at closest | 182 s | 2.75× | |
| from the Sun | 499 s | 1× | 8 minutes 19 seconds |
| from Jupiter | 2,600 s | 0.192× | |
| from Neptune | 15,000 s | 1/30 | |
| from Voyager 1 | 80,000 s | 1/160 | About 22 hours |
| from Proxima Centauri | 134,117,046 s | 1/268,234 | |
| from the galactic centre | 820,480,752,000 s | 1/1,640,961,504 | |
| from Andromeda | 80,059,987,224,000 s | 1/160,119,974,448 |
Worth knowing
- The Andromeda galaxy you can see with the naked eye is 2.5 million years old — light that left before Homo erectus existed.
- A radio conversation with Mars has a round trip of between 6 and 44 minutes, which is why rovers must drive themselves.
Frequently asked
How long does sunlight take to reach Earth?
499 seconds — 8 minutes 19 seconds — on average. The photon itself took perhaps 100 000 years to escape the Sun’s interior first.
What is the furthest thing we can see?
The cosmic microwave background, 13.8 billion years old. The most distant individual galaxies observed are around 13.4 billion light-years away in look-back time.