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To convert ly to km: multiply by 9.461 × 10¹². To convert ly to parsecs: multiply by 0.3066.
1 ly = 9.4607 × 10¹⁵ m = 63,241 AU = 0.3066 pc ≈ 9.461 trillion km.
For example, 1 Light Year (ly) = 9.460700e+27 Picometer (pm).
| Light Year (ly) | Picometer (pm) |
|---|---|
| 0.1 | 9.460700e+26 |
| 0.5 | 4.730350e+27 |
| 1 | 9.460700e+27 |
| 2 | 1.892140e+28 |
| 5 | 4.730350e+28 |
| 10 | 9.460700e+28 |
| 25 | 2.365175e+29 |
| 50 | 4.730350e+29 |
| 100 | 9.460700e+29 |
| 500 | 4.730350e+30 |
| 1000 | 9.460700e+30 |
The light-year is the distance that light travels in one Julian year (365.25 days) in a vacuum, approximately 9.461 × 10¹⁵ meters.
1 ly = 9.4607 × 10¹⁵ m = 63,241 AU = 0.3066 pc ≈ 9.461 trillion km.
To convert ly to km: multiply by 9.461 × 10¹². To convert ly to parsecs: multiply by 0.3066.
Expressing distances to stars: Proxima Centauri ≈ 4.24 ly, Sirius ≈ 8.6 ly, Vega ≈ 25 ly.
When you see a star 100 light-years away, you're seeing it as it was 100 years ago — you're literally looking into the past.
Thinking a light-year is a unit of time — it's a unit of distance! It's how far light travels in one year.
Light speed = ~300,000 km/s. In one year, light covers ~9.46 trillion km. That distance is one light-year.
The picometer is a unit of length equal to 10⁻¹² meters, or one trillionth of a meter.
1 pm = 10⁻¹² m = 0.01 Å = 1,000 fm. One nanometer equals 1,000 picometers.
To convert pm to meters: multiply by 10⁻¹². To convert pm to angstroms: divide by 100.
Expressing covalent bond lengths (e.g., C–C bond ≈ 154 pm), atomic radii, and crystal lattice spacings.
The hydrogen atom has a radius of about 53 pm (the Bohr radius), while a carbon-carbon single bond is about 154 pm long.
Mixing up picometers and nanometers — remember 1 nm = 1,000 pm. Some sources still use the deprecated angstrom.
Think of pm as the natural unit for atoms: most atomic radii fall between 30 pm and 300 pm.



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