Monday, 29 April 2013
A spacetime map?
The notion of a spacetime map emerged within my mind as I was reading page 42 of the Scientific American of June 2010 article, 'Is time an illusion?' p.41-47, by Craig Callender.
"Physicists, artists and graph makers of all kinds routinely depict time as another dimension of space, creating a unified spacetime-shown here as a three-dimensional block in which a ball bounces off a wall. Relativity theory holds that spacetime can be sliced up in various ways. But not all are equally sensible."
Spacetime that can be sliced up in various ways. Time only another additional dimension to the other three familiar of space, a map routinely drawn by reducing the height dimension to zero, effectively out of the three space dimensions only considering two of them in order to construct the map, a two-dimensional map. And as nothing prohibits what dimensions to choose in order to construct a map, a map is constructed by reducing any out of the three spatial dimensions to zero.
"The usual way takes slices of space at successive moments of time, creating a movie of the ball's motion. Each frame leads to the next, according to the familiar laws of physics."
Slices of space while considering all four dimensions of spacetime available, zeroing not only one but two out of the four spacetime dimensions. Zeroing one of space and the time dimension. The slices of space taken at successive moments of time but nevertheless at zero time. Frame-by-frame that altogether make up a movie, a mapping of an event unfolding, according to the laws of physics.
"An alternative considers slices not from past to future but from left to right. Each slice is part space, part time. To the left of the wall, the ball appears in two positions; on the right, it does not appear at all. If this slicing seems strange, it should: it makes the laws of physics very unwieldy."
..not the zeroing of time but one of the dimensions of space, a two-dimensional map out of time and one of space dimension
..the event looked from another perspective augmenting insights triggering imagination
Maps, slices of space and maps slices of spacetime. Maps constructed by choosing at will two out of the four now dimensions, as long as it produces our familiar two-dimensional arrangements.. at will
Objects and events. Spacetime maps for mapping events? Simultaneity being absolute, observer-independent? Events being observer-independent?
"No matter when or where an event occurs, classical physics assumes that you can objectively say whether it happens before, after or simultaneously with any other event in the universe. Time therefore provides a complete ordering of all the events in the world. Simultaneity is absolute-an observer-independent fact. Furthermore, time must be continuous so that we can define velocity and acceleration."
playing with words dragging along the concepts they are attached to, forcing in their way new conceptions to appear, to create new notions in my mind