In physics, spacetime is any mathematical model which fuses the three dimensions of space and the one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why different observers perceive where and when events occur differently.
Answer:
what time you thinking. about coming down to take a break and ok I will get to?. that was a right answer?
The fourth dimension is technically time. the fourth dimension that you are talking about is actually impossible to comprehend.
That's a weird graph, but judging from the units the acceleration is the slope of the graph.
a = (0.8 - 0.3)/(0.16 - 0.055) = 4.76 m/s²