We measure change. Time is the dimension of change.
Without change there is no time. And change is reference frame specific.
But, specifically in spacetime, we measure changing position, aka Motion.
Tag Spacetime
What is the relationship between time and space? I recently read a book which was based on spirituality wherein an author says time and space are not different as they are interdependent (when it’s spring in Europe, it’s winter in Australia.)
The relationship is that both are dimensions.
Dimensions is a very misused word. A dimension is a mathematical model that calibrates, measures and indexes an aspect of reality using standard units. Dimensions are abstract overlays that quantity underlying reality for us.
So, in the context of Space and Time, Space is the dimension of position and relative position. The xyx-axis allows us to define a position (in space), and relative positions distance. But its a static dimension until we introduce Time, the dimension of change.
So space, measured in say miles, gives us the quantification of the change of relative position. And Time, in say units of hours, gives us the rate of change (hence time is the dimension of change).
Ergo MPH – Miles (space) Per Hour (time)
So merge the dimension of [relative] position (Space) with the dimension of change (Time) and you get Spacetime, the dimension of changing position…aka motion.
So Time and Space are not interdependent. But Space is static without Time.
Is time thought of as a literal physical dimension (90 degrees perpendicular to our own) or is it something else entirely?
Something else entirely. The ‘fourth dimension’ right-angle thing is a hopeless attempt to interpret spacetime.
Dimensions are (abstract) measurement frameworks. Space (in the context of dimension) measures relative position, for convenience, in 3 right-angles vectors (height, depth, width or xyz-axis).
Time is the dimension of change, i.e. it’s how we measure change rate. For example we measure change in position (aka Motion) in miles PER HOUR. The per hour bit is time calibrating change.
The problem arises because too many physicists don’t seem to understand what ‘dimensions’ are, and don’t understand what Space and Time are within the context of dimension. Hence they really don’t understand what Spacetime is…the dimension changing position i.e. motion.
I get asked lots of questions about Time and related things. Here are some of the questions, and my answers, I hope they are of interest.
If space is absolute no matter the frame of reference but time is relative based on the frame of reference of the observer, should quantum superposition be interpreted as a particle in 2 or more places/states in time simultaneously instead of space?
Is space absolute?
Space, the word, has different meanings depending on context.
When you talk about Space and Time together you are talking in the context of dimensions.
Dimensions are abstract frameworks / models, formulated in standard units, that we overlay an aspect of reality in order to calibrate and index that particular reality.
[There are many many dimensions, many aspects of reality, that are calibrated in standard units. Dimensions of weight, mass, density, radioactivity, heat, colour, brightness, sound volume, tone, pitch etc etc.]
All dimensions are relative. And all dimensions are abstract ( eg the dimension of temperature is abstract, heat the underlying reality). And all dimensions must be, obviously, reference-frame specific.
Space (in the context of dimensions) is the dimension of relative position. The XYZ axis, the three sub-dimensions (vectors) of height, breadth and depth, simply determine relative position. And we calibrate in units of, say, miles, or centimetres etc.
And Time is the dimension of change. We calibrate change (rate) in units if time, as in xxxx PER HOUR. The ‘per hour’ or ‘per second’ etc is the calibration of change.
So Time is always used in conjuncture with another dimension to give that other dimension a ‘rate’ of change.
So, Space is the dimension of (relative) position. Time is the dimension of change. Merge the two and you get SpaceTime the dimension of changing position aka Motion.
Spacetime is the dimension of (constant) motion. [‘Constant’ motion (eg miles per hour) because dimensions are reference frame specific…for changing motion (acceleration) we need spacetime-time (miles per hour per hour) and for increasing acceleration its spacetime-time-time (eg miles per hour per hour per hour) etc]
