measurement
15 questions tagged measurement — spanning every one of the seven Ws.
Whose Name Is on the Fahrenheit Temperature Scale?
The Fahrenheit scale is named after physicist Daniel Gabriel Fahrenheit, who proposed it in 1724.
Whose Name Is on the Kelvin Temperature Scale?
The kelvin is named after William Thomson, Lord Kelvin, who proposed an absolute temperature scale in 1848.
What is the cosmic distance ladder?
The cosmic distance ladder is a chain of methods astronomers use to measure distances from nearby objects to faraway galaxies. Each step calibrates the next one.
Whose work created the first widely used earthquake magnitude scale?
Charles F. Richter introduced the local magnitude scale in 1935 with Beno Gutenberg. The Richter scale made earthquake sizes easier to compare.
How do earthquake magnitudes differ from earthquake intensity?
Magnitude measures the energy released at the source, while intensity describes the shaking and damage at a specific location. A single earthquake has one magnitude but many different intensities.
How do scientists measure how much rain has fallen?
They use rain gauges, weather radar, and satellites to estimate precipitation. A standard gauge measures collected rain depth in millimeters.
What is the Mercalli intensity scale?
The Mercalli intensity scale describes how strongly an earthquake is felt and how much damage it causes at a specific place. It is different from magnitude, which measures the earthquake’s energy.
What is moment magnitude?
Moment magnitude is the modern scale scientists use to measure earthquake size based on the amount of energy released. It is the standard measure for large earthquakes today.
How do scientists measure the gravitational constant G?
They use sensitive laboratory experiments that compare the tiny attraction between known masses. The value of G is about 6.674 × 10^-11 newton square meters per kilogram squared.
How do scientists distinguish the four fundamental forces in experiments?
They look at how particles interact: charge, range, strength, and what particles are exchanged. Each force leaves a different signature in detectors and calculations.
What is an astronomical unit?
An astronomical unit, or AU, is the average distance from Earth to the Sun. It is about 149.6 million kilometers, or 93 million miles.
What is a sidereal day?
A sidereal day is the time a planet takes to rotate once relative to distant stars. On Earth it is about 23 hours, 56 minutes and 4 seconds.
When was the first atomic clock built?
The first practical atomic clock was built in 1949, using ammonia, and cesium clocks followed soon after.
Whose idea was the method that allowed astronomers to calculate distances to stars from Earth’s motion?
Friedrich Bessel pioneered the first successful stellar parallax measurement method. In 1838 he measured the distance to 61 Cygni.
How do scientists measure the distance to faraway stars?
For nearby stars, astronomers use parallax: the star appears to shift against the background as Earth moves around the Sun. For more distant stars, they use brightness and other methods calibrated from closer measurements.