What is the effect of a super massive black hole on space time?

Answer 1

The effects of all massive objects on spacetime would be similar, the degree of effect being largely determined by the mass of the object since the latter would dictate the strength of the gravitational field it generates. In the case of the most massive black holes, the supermassive ones identified in many galactic nuclei, the effects would be greatest.

The nature of the effect itself could be most adequately described by the general theory of relativity; which states that gravitational fields affect the local curvature of spacetime; the greater the mass, the greater the curvature. Effects predicted by general relativity have been proven experimentally including redshifting, time dilation, and gravitational lensing. Oft-quoted thought experiments are cited in which, if a distant observer were able to see for example a clock being thrown into a supermassive black hole, the observer would note light from the clock becoming dimmer and redder, and the clock itself would appear to run more and more slowly as it approached the event horizon, at which point time would seem to a distant observer to have stopped entirely.