Don't waste resources on such nonsense any longer because there is nothing called spacetime in nature, not to mention the existence of its singularities. Einstein's relativity is totally wrong because our physical time is absolute and independent of the 3D physical space. He made a fatal mistake in his special relativity. He assumed that the speed of light should be the same relative to all inertial reference frames, which requires the change of the definition of space and time. But he never verified that the newly defined time was still the time measured with physical clocks. This leads to many mathematicians and theoretical physicists believe that time is like a playdough which can be freely compressed/stretched to fit their fantacies. Actually our physical time measured with physical clocks is stiff and absolute, which won't change with the change of the definition of the space and time. Einstein's newly defined relativistic time is no longer our physical time, but a mathematical variable without physical meaning, which can be easily verified as follows:
We know physical time T has a relationship with the relativistic time t in Einstein's special relativity: T = tf/k where f is the relativistic frequency of the clock and k is a calibration constant, that is, a clock uses the change of the status of a physical process to indirectly measure time. Now We would like to use the behavior of our physical time in Lorentz Transformation to demonstrate that the relativistic time t defined by Lorentz Transformation is no longer our physical time T.
If you have a clock (clock 1) with you and watch my clock (clock 2) in motion and both clocks are set to be synchronized to show the same physical time T relative to your inertial reference frame, you will see your clock time: T1 = tf1/k1 = T and my clock time: T2 = tf2/k2 = T, where t is the relativistic time of your reference frame, f1 and f2 are the relativistic frequencies of clock 1 and clock 2 respectively, k1 and k2 are calibration constants of the clocks. The two events (Clock1, T1=T, x1=0, y1=0, z1=0, t1=t) and (Clock2, T2=T, x2=vt, y2=0, z2=0, t2=t) are simultaneous measured with both relativistic time t and clock time T in your reference frame. When these two clocks are observed by me in the moving inertial reference frame, according to special relativity, we can use Lorentz Transformation to get the events in my frame (x', y', z', t'): (clock1, T1', x1'=-vt1', y1'=0, z1'=0, t1'=t/γ) and (clock2, T2', x2'=0, y2'=0, z2'=0, t2'=γt), where T1' = t1'f1'/k1 = (t/γ)(γf1)/k1 = tf1/k1 = T1 = T and T2' = t2'f2'/k2 = (γt)(f2/γ)/k2 = tf2/k2 = T2 = T, where γ = 1/sqrt(1-v^2/c^2). That is, no matter observed from which inertial reference frame, the events are still simultaneous measured with physical time T i.e. the two clocks are always synchronized measured with physical time T, but not synchronized measured with relativistic time t'. Therefore, our physical time and the relativistic time behave differently in Lorentz Transformation and thus they are not the same thing. The change of the reference frame only makes changes of the relativistic time from t to t' and the relativistic frequency from f to f', which cancel each other in the formula: T = tf/k to make the physical time T unchanged i.e. our physical time is still absolute in special relativity. Therefore, based on the artificial relativistic time, special relativity is wrong, so is general relativity. For more details, please check:
https://www.researchgate.net/publication/297527784_Challenge_to_the_Special_Theory_of_Relativity