Feet to Light-seconds (ft to ls)
1 foot equals 1.016703362×10⁻⁹ light-seconds (rounded).
How to convert feet to light-seconds
To convert feet to light-seconds, multiply the number of feet by 1.016703362×10⁻⁹. The factor is rounded to 10 significant digits. To go the other way, multiply light-seconds by 983,571,056.4 (rounded).
light-seconds = feet × 1.016703362×10⁻⁹
Example: 10 feet = 1.016703362×10⁻⁸ light-seconds.
About these units
Foot (ft)
12 inches. Defined as exactly 0.3048 meters. Still the standard unit for height, altitude in aviation and room dimensions in the US and UK.
Human anatomy supplied the idea: an adult foot is roughly 15 percent of body height. Ancient cultures turned that into standards, but not the same one. The Greek pous was about 302 mm, the standard Roman pes about 295.7 mm, and a Harappan foot of about 335 mm has been reported from the Indus Valley. Historically, a foot fell somewhere between about 250 and 335 mm. Charlemagne tried to standardize units around 790 with little lasting success, and in 1593 English law fixed the statute mile at 5,280 feet.
The modern foot dates from the 1959 International Yard and Pound Agreement, which defined the yard as exactly 0.9144 meter and so the foot as exactly 0.3048 meter; the UK adopted it on 1 January 1964. The US survey foot, defined in 1893 as 1200/3937 meter, was deprecated on 31 December 2022. Feet remain in everyday use for height and rooms in the US, and ISO shipping containers are defined in them. Aviation altitudes use them too: flight level 330 means 33,000 feet.
1 foot = 0.3048 meters (exactly).
Sources: Wikipedia: Foot (unit); Wikipedia: Mile; NIST Guide to the SI, Appendix B.8: conversion factors
Light-second (ls)
The distance light travels in a vacuum in one second: 299,792,458 meters. The Moon is about 1.28 light-seconds from Earth.
Because the speed of light is now fixed at 299,792,458 meters per second, a light-second is exactly that many meters, with no uncertainty at all. Astronomers and radio engineers treat it as a convenient yardstick for distances that are small on the scale of the solar system but large on the scale of a laboratory. The abbreviation ls appears in tables of astronomical units, and it is not an official SI unit.
The Moon is the standard example: its average distance from Earth is about 1.282 light-seconds, which is why a radio exchange with a lunar mission has a noticeable round-trip lag of roughly two and a half seconds. The Earth's mean diameter is only about 0.0425 light-seconds, while the Sun's diameter is about 4.643. One astronomical unit is about 499 light-seconds. Sixty light-seconds make a light-minute, 3,600 make a light-hour, and 31,557,600 make a light-year, based on the Julian year.
1 light-second = 299,792,458 meters (exactly).
Sources: Wikipedia: Light-second; Wikipedia: Light-minute
Related conversions
- Light-seconds to feet (reverse)
- Feet to meters
- Feet to kilometers
- Feet to centimeters
- Feet to millimeters
- Feet to inches
- Feet to yards
- Feet to miles
- Feet to micrometers
- Feet to nanometers
- Feet to nautical miles
- Feet to pixels (CSS)
- Feet to light-years
- Meters to light-seconds
- Kilometers to light-seconds
- Centimeters to light-seconds
- Millimeters to light-seconds
- Inches to light-seconds
- Yards to light-seconds
- Miles to light-seconds
See all length units.