[Eli5]:What’s the exact difference between time and space?
In: 2
A few simple differences:
Time only flows in on direction its unidirectional whereas space is omnidirectional, you can go in any direction. (At least until you enter a black holes event horizon then time and space switch roles.)
Your progress through time is not up to you. You always move through time.
These differences are enough to not say 4D spacetime but rather 3+1D spacetime.
But its better to think of space and time as the two parts of a whole.
Time is one dimension. Its what’s shown on your clock. We can only move in one direction through time.
Space is made up of 3 dimensions (like x,y,z). You can move around in all directions in it and you measure it with a ruler.
Together, anything that happens, be that me sitting here typing this, or a firework going off, or whatever, any event is described with those 4 dimensions: (x, y, z, t). You might even say “I went to the store on X street at 3:00pm”, thats describing the event of you going to the store with a position in space (X street) and a time (3:00pm)
In physics you hear “spacetime” because of the above. We plot events in that 4d coordinate system that consists of “space” and “time”. Hence “spacetime”.
It would be better if you gave context for your question.
Intuitively speaking, space measures where events happen. Time measures when events happen.
Speaking in physics (the tag you gave this question) space has three dimensions while time only has one. Space and time have different signs (+++- signature for the Minkowski metric used to model spacetime). You can actually view time’s relation to space under this metric as identical to the imaginary number’s relation to the real numbers. Note that physics (GR) is a mathematical theory and doesn’t really try to understand the nature of time directly, only for using time as an index to measure the universe.
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