Imagine taking a sheet and stretching it out so it formed a totally flat, four-sided plane; and placing an assortment of marbles of different sizes and weights upon this sheet. If the surface in question was totally solid and non-elastic, like a table top; the results of this exercise would be obvious - all of the marbles, regardless of their size and weight, would all remain exactly where you left them.
However, because we are dealing with a sheet that has been made to provide a flat surface; something interesting happens. The heaviest marbles on the sheet, through their increased weight; would cause the surface of the sheet to sag in places - creating areas of a higher gradient than the flat sheet surrounding them.
The smaller marbles, unable through their weight to create a secure place on the surface of the sheet to maintain their own position; would begin to roll towards the heavier marbles on the sheet and collect around them. They would gravitate towards the heavier marbles.
Perhaps gravity works in a similar way.
Perhaps the fabric of space time stretches in a similar fashion to the fabric of the sheet, only in this case it would be necessary to imagine the effect of the marble's weight on this fabric being exerted not on a single flat plane, but in a sphere of influence.
If time slows down when travelling at the speed of light; because black holes are essentially the opposite of light, when objects are attracted by a black hole could the opposite happen - and could time appear to be speeding up? If this was the case, it could be said that there was a gradient with regards to the length of time the closer you got to the black hole.
Even objects that were travelling at a constant speed measurable in kilometres per second, would in fact be accelerating towards it - because the actual length of a second would be decreasing. Light being drawn into the black hole would be doing the impossible - travelling faster than the speed of light - and yet not so, because it would still be travelling at its maximum speed per second. Only the scale of those seconds would be gradually reduced.
Perhaps the same phenomenon occurs, though on a greatly reduced scale in comparison to a black hole; around anything that possesses sufficient mass to cause such a gradient.
Now returning to the marbles arrayed on the sheet, lighter marbles collecting around those heavy enough to create an indentation in the sheets surface - let us add a second set of objects to this scenario. Imagine taking a number of helium balloons, of various size and degrees of buoyancy; and placing them under the sheet.
In some places, the lifting effect of the balloons would be sufficient to push upwards on the fabric of the sheet with enough force that they would cause its surface to lift upwards. Marbles that weren't heavy enough to retain their position on the sheet, would be pushed away from these uplifted areas caused by the balloons. The balloons would have the opposite effect - pushing the marbles away instead of attracting them.
Perhaps light can be likened to those helium balloons and the effect they exert on the fabric of the sheet, and in turn the fabric of space time. We know that solar sails are capable of being accelerated using the push generated by light alone, so perhaps a similar phenomenon is occurring. Perhaps light is also capable of creating an amount of gradient in space time, but in the opposite fashion of a black hole.