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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) = 5.853470e+50 Planck Length (ℓP).
| Light Year (ly) | Planck Length (ℓP) |
|---|---|
| 0.1 | 5.853470e+49 |
| 0.5 | 2.926735e+50 |
| 1 | 5.853470e+50 |
| 2 | 1.170694e+51 |
| 5 | 2.926735e+51 |
| 10 | 5.853470e+51 |
| 25 | 1.463367e+52 |
| 50 | 2.926735e+52 |
| 100 | 5.853470e+52 |
| 500 | 2.926735e+53 |
| 1000 | 5.853470e+53 |
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 Planck length is the fundamental natural unit of length, approximately 1.616 × 10⁻³⁵ meters, below which the conventional concepts of space may cease to exist.
ℓP = √(ℏG/c³) ≈ 1.616255 × 10⁻³⁵ m.
To convert Planck lengths to meters: multiply by 1.616255 × 10⁻³⁵.
No practical applications — purely theoretical. It represents the scale at which quantum gravity effects become significant.
The Planck length is about 10⁻²⁰ times the diameter of a proton. It's as far below a proton as a proton is below a grain of sand.
Thinking the Planck length is the 'smallest possible length' — it's the scale where our current physics models break down, not a proven minimum.
The Planck length arises from combining the three constants that govern quantum mechanics (ℏ), gravity (G), and relativity (c).



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