Understanding furlongs to astronomical units Conversion
The furlong (fur) is a traditional imperial unit of length equal to 660 feet or one-eighth of a mile, still used in horse racing and older land measurement. The astronomical unit (au) is the mean Earth-Sun distance, about 149.6 million kilometers, used to describe distances within the Solar System. Converting between them is mostly an illustrative exercise in scale, showing how vast astronomical distances are compared with a terrestrial length.
Conversion Formula
To convert furlongs to astronomical units, multiply by this factor:
Step-by-Step Example
Convert 25 furlongs to astronomical units.
How to Convert furlongs to astronomical units
Scale a terrestrial furlong down to Solar-System distances with one multiplication.
- Take the furlong value: Note how many furlongs you want to convert.
- Multiply by the factor: Use 1.344725 × 10⁻⁹, the number of astronomical units in a furlong.
- Express in scientific notation: The result will be a very small number, best written with a power of ten.
- Worked result: 25 fur × 1.344725 × 10⁻⁹ = 3.36181 × 10⁻⁸ au.
furlongs to astronomical units conversion table
| furlongs (fur) | astronomical units (au) |
|---|---|
| 0 | 0 |
| 1 | 1.344725e-9 |
| 2 | 2.68945e-9 |
| 3 | 4.034175e-9 |
| 4 | 5.3789e-9 |
| 5 | 6.723625e-9 |
| 6 | 8.06835e-9 |
| 7 | 9.413075e-9 |
| 8 | 1.07578e-8 |
| 9 | 1.210253e-8 |
| 10 | 1.344725e-8 |
| 15 | 2.017088e-8 |
| 20 | 2.68945e-8 |
| 25 | 3.361813e-8 |
| 30 | 4.034175e-8 |
| 40 | 5.3789e-8 |
| 50 | 6.723625e-8 |
| 60 | 8.06835e-8 |
| 70 | 9.413075e-8 |
| 80 | 1.07578e-7 |
| 90 | 1.210253e-7 |
| 100 | 1.344725e-7 |
| 150 | 2.017088e-7 |
| 200 | 2.68945e-7 |
| 250 | 3.361813e-7 |
| 300 | 4.034175e-7 |
| 400 | 5.3789e-7 |
| 500 | 6.723625e-7 |
| 600 | 8.06835e-7 |
| 700 | 9.413075e-7 |
| 800 | 0.00000107578 |
| 900 | 0.000001210253 |
| 1000 | 0.000001344725 |
| 2000 | 0.00000268945 |
| 3000 | 0.000004034175 |
| 4000 | 0.0000053789 |
| 5000 | 0.000006723625 |
| 10000 | 0.00001344725 |
| 25000 | 0.00003361813 |
| 50000 | 0.00006723625 |
| 100000 | 0.0001344725 |
| 250000 | 0.0003361813 |
| 500000 | 0.0006723625 |
| 1000000 | 0.001344725 |
What is the furlong?
The furlong (fur) is a unit of length in the imperial and US customary systems, equal to one-eighth of a mile, most commonly used today in horse racing.
Definition
One furlong equals 660 feet, or 220 yards, or 40 rods, or 10 chains.
Eight furlongs make one statute mile. This value uses the international foot; the US survey furlong is larger by a factor of 1200/1199.
Origin and History
The name comes from Old English "furh" (furrow) and "lang" (long), meaning the length of a furrow in a ploughed open field. In the medieval English system, a furlong was the distance a team of oxen could plough before resting, standardized as the long side of a one-acre strip (one furlong by one chain). It became a fundamental unit of the English land-measurement system.
Law and Notable Facts
The furlong survives chiefly in horse racing, where race distances are quoted in furlongs (for example, a "six-furlong sprint"). It is also preserved in the definition of the acre and the mile. The whimsical furlong–firkin–fortnight (FFF) system uses it as an example of an intentionally impractical unit of length.
Real-World Examples and Conversions
- 1 furlong = 220 yd = 660 ft = 201.168 m.
- 8 furlongs = 1 statute mile.
- 1 furlong = 10 chains = 40 rods.
- The Kentucky Derby is run over 10 furlongs (1.25 miles).
What is the astronomical unit?
The astronomical unit (au) is a unit of length used in astronomy to express distances within the Solar System, roughly the mean distance between Earth and the Sun.
Definition
The astronomical unit is defined as exactly 149,597,870,700 metres.
Since 2012 this is a fixed conventional value adopted by the International Astronomical Union (IAU), replacing the earlier definition based on the Gaussian gravitational constant. Related astronomical units build on it: 1 light-year ≈ 63,241 au and 1 parsec ≈ 206,265 au.
Origin and History
The concept dates to antiquity as astronomers sought the Earth–Sun distance to scale the Solar System. Early estimates were crude; the 1761 and 1769 transits of Venus allowed the first reasonably accurate measurements. For most of the 20th century the au was defined dynamically via Kepler's third law and the Gaussian constant. In 2012 the IAU redefined it as a fixed number of metres to eliminate its dependence on the changing measured value of the heliocentric gravitational constant.
Law and Notable Facts
The au is accepted for use with the SI, with the symbol "au" recommended by the IAU and BIPM (older texts use "AU" or "ua"). Light travels one astronomical unit in about 499 seconds, or roughly 8.3 minutes—the reason sunlight reaching Earth is always about 8 minutes old.
Real-World Examples and Conversions
- Earth orbits the Sun at 1 au (about 149.6 million km).
- Neptune orbits at roughly 30 au from the Sun.
- The Voyager 1 spacecraft is over 160 au away as of the 2020s.
- 1 au ≈ 92.956 million miles ≈ 499 light-seconds.
Frequently Asked Questions
How many astronomical units is one furlong?
One furlong equals about 1.344725 × 10⁻⁹ astronomical units, an extremely tiny fraction because an au is roughly 149.6 million kilometers.
How many furlongs make up one astronomical unit?
About 743,646,500 furlongs span a single astronomical unit, reflecting the enormous gap between terrestrial and Solar-System scales.
Why is this conversion so lopsided?
An astronomical unit is the Earth-Sun distance, while a furlong is only 201.168 meters, so it takes hundreds of millions of furlongs to cover just one au.
Would anyone use furlongs in astronomy?
Not in practice; astronomers use au, light-years, and parsecs. Converting furlongs to au is chiefly educational, illustrating how imperial units break down at cosmic scale.
What is 100 furlongs in astronomical units?
100 furlongs equal about 1.344725 × 10⁻⁷ au, still far less than a millionth of the Earth-Sun distance.
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Complete furlongs conversion table
| Unit | Result |
|---|---|
| Nanometers (nm) | 201168000000 nm |
| Micrometers (μm) | 201168000 μm |
| Millimeters (mm) | 201168 mm |
| Centimeters (cm) | 20116.8 cm |
| Decimeters (dm) | 2011.68 dm |
| Meters (m) | 201.168 m |
| Kilometers (km) | 0.201168 km |
| light-years (ly) | 2.126347e-14 ly |
| astronomical units (au) | 1.344725e-9 au |
| parsecs (pc) | 6.519411e-15 pc |
| ångströms (angstrom) | 2011680000000 angstrom |
| Mils (mil) | 7920000 mil |
| Inches (in) | 7920 in |
| Yards (yd) | 220 yd |
| US Survey Feet (ft-us) | 659.9987 ft-us |
| Feet (ft) | 660 ft |
| Fathoms (fathom) | 110 fathom |
| Miles (mi) | 0.125 mi |
| Nautical Miles (nMi) | 0.108622 nMi |
| chains (ch) | 10 ch |
| rods (rd) | 40 rd |
| hands (hh) | 1980 hh |