Question about space/time theory

[jkoenig00]

My understanding of space/time is that objects influence the gravitational pull around them similar to placing an object on a flat flexible surface. However, I was recently learning about "gravitational lensing." It seems that this effect is happening in three dimensions. So shouldn't there be a third dimension to space/time?

[notFritzArgelander]

Spacetime as in Special Relativity (which is flat) and General Relativity (which is curved) is 4 dimensional always.

What you may have seen is an oversimplified toy model in 2 dimensions, the infamous "rubber sheet" model. It is not intended to be a full and true representation of what is happening in the theory, it's just like a set of training wheels for learning to ride a bike.

One other thing.... in General Relativity there is no "gravitational pull". Rather the masses (and energies) in the system curve spacetime and then spacetime tells the bodies how to move, by following the straightest possible path in that spacetime.