epistemology, science, kinds of knowledge, methodology
Of the base units of the International System of Units (SI) only two concern movement in a direction: the units of length (metre) and duration (second). The candela measures luminous intensity in a direction without regard for movement. Derived units of movement include speed and velocity (metres per second), force (newton), pressure (pascal), energy (joule), […]
The first clocks were the cycles of daily life, notably the diurnal cycle of light and dark. These continued apparently without end and so provided a measure of change, of ceaseless movement and return. Since ancient times the day has been divided into 24 hours, and since medieval times an hour has been divided into
To convert a length of space into a corresponding length of time requires a conversion factor. For physical reality that conversion factor is the speed of light: r = ct, where r is a spatial displacement, t is a temporal displacement, and c is the conversion factor. For a mode of transportation the conversion factor
I’m made the point that if we’re asked how far away a place is, we can answer in units of space or time. If we’re talking about stable places such as on land, the distance will not change but the length of time depends on a characteristic speed. In that case the length of time
In order to understand anything we need to have good definitions. Otherwise the words we use will lead us astray — which is what has happened with the word “time”. I have a copy of the McGraw Hill Dictionary of Physics, Third Edition. Here is its definition of time: The dimension of the physical universe
“How far is it to X from Y?” That everyday question can be answered either by a distance or a duration with a mode of travel (e.g., walking, driving, flying). The interchangeability of a length of space and a length of time leads to two simple conclusions: (1) time has as many dimensions as space
A simple way to look at the world is to assume that space and time are absolute: the locations, the distances, the durations, speeds, and so forth as measured by one person are the same for everyone. That is, if my automobile speedometer shows 50 mph (80 kph), then the police with a laser gun
Because of the symmetry of space and time, the laws of physics should be symmetric in space and time, or at least show their symmetry. Granted, one must either use the speed (change in position per unit of time) or the pace (change in time per unit of length). But other than such choices, the
Diachronic, 1857, from Greek dia “throughout” + khronos “time” means something happening over time, particularly the historical development of something such as a language through time. Synchronic, 1775, means “occurring at the same time,” from Late Latin synchronus “simultaneous,” means the analysis of something such as a language over a wide area at a point
Here is a roundup of various instruments and methods for measuring space and time that may be stopped or continued indefinitely: A bematist (from ancient Greek βῆμα bema ‘pace’) was a specialist in ancient Greece who was trained to measure distance by counting their steps. An odometer for measuring distance was first described by Vitruvius
