Newton also said that "gravity" was an attracting force that existed between objects. 

Newton's 3D cosmology worked just fine in calculating the geometry of our solar system until other astronomer/mathematicians discovered that the transmission of light was not instantaneous. These other astronomer/mathematicians determined that light was "very fast" but not instantaneous. This discovery about light speed threw a monkey wrench into Newton's celestial mechanics as applied outside of our solar system. 

In Albert Einstein's universe there are four dimensions: length, breadth, width and time. For Einstein, stationary objects in space occupy three dimensions but these three dimensions are not constants. 
Einstein called the three dimensions (length, breadth and width) "Space" and considered "Time" as a forth dimension that is not just a passive measuring device but interacts dynamically with the other three. 
Einstein determined that all four components (length, breadth, width and time) of his cosmology were variable depending upon velocity*. 

*This is a curious conclusion because if time is variable depending upon velocity then how does one measure 'velocity' which, typically, is 'time dependent'?  

Einstein determined that the speed of light was a constant and unaffected by time. But how can one determine the speed of light when time is variable?  

Then Stephen Hawking says "then what happens to the velocity of light when time stops in a blackhole"? 

Einstein's cosmology is phenomenal because it means that time / space and material objects are not fixed quantities, but rather, they are only temporarily fixed quantities. They become variable and their structural mechanics start to rearrange when you introduce movement. 

Einstein needed a constant in order to be able to measure the shifting of the structure of time / space / matter / velocity.  He determined that the constant he required was the maximum speed of light, which is, the velocity of light when it is unencumbered by matter and traveling through  uncompressed space with zero gravity (i.e. a pure vacuum).

Einstein also said (implied) that there are two types of "space": Traditional "space" which is empty, and a solid entity called "mass". 

In traditional geometry a three dimensional object is thought to occupy space and this analysis works fine for measuring a stationary object.  However, once the object starts moving it is no longer in a 3 dimensional Newtonian universe and but enters the Einsteinian cosmology of "The Fourth Dimension", as once an object starts moving it no longer 'occupies' space but 'displaces' it.  

Displacement Theory of Gravity© Gravity is described as an "apparent" attracting force that exists between all objects that have mass.  Gravity is produced by the compression/expansion of space around and between objects that, in reality, do not occupy space but, rather, displace it.   The immediate space surrounding an object is expanded and the space between objects (distance) in space is compressed. Thus "gravity" is a "push / pull" force that only seems like an exclusively attracting force that is actually a compressing force also. It follows (to me anyway) that our measurement of the speed of light is inaccurate (insufficient) because we are measuring light speed in compressed space. Light appears to travel slower through compressed space which is why, according to Stephen Hawking, a space ship navigating through the event horizon of a black hole would appear, to a distant observer, as stopped while the occupants of the space ship would experience velocity.  The space near a black hole is highly compressed, light velocity remains the same  (Pi x 100,000,000 or 314,159,265.4 meters per second ) however from the perspective of a distant observer light speed only appears to be slowing because of the compression of  space. footnote: Space immediately surrounding an object is  sretched.  Space between objects is compressed.

It is at this juncture that Stephen Hawking enters the playing field. Hawking's credentials are as impressive as Albert Einstein's and Isaac Newton's. Stephen determines that there is a theoretical place in the universe that contains huge quantities of matter that have attained "infinite density" (a teaspoon full is estimated to weigh hundreds of tons).  Stephen calls these warped vortices "black holes" because light cannot escape from the black hole's massive gravitational influence. 

It is theorized that the escape velocity (the speed necessary to break free of a gravitational influence) for a black hole exceeds the speed of light.  Since light speed is the maximum speed limit in the universe (Einstein) then it seems that once you are in a black hole there is no escape (unless you can find a way to go faster than light and then presumably go back in time and avoid entering the blackhole in the first place).

Einstein claims that material objects approaching light speed would begin to expand their mass exponentially.  As a result of the expansion there would be an infinite resistance to any increase in velocity.  (Note: This is not a 'bug on the windshield' scenario, this is the vacuum of space which offers no resistance to motion). Einstein's theory established "light speed" as the maximum speed limit in the universe and also raises the possibility that a blackhole is only a handful of matter traveling at near light speed.

So, the question is, "If light cannot be stopped (Einstein), and if light is trapped inside of a black hole (Hawking) where time and velocity have stopped then what is it that happens to the velocity of light without the presence of time? In other words, how do you measure "light speed" without having time as a part of the equation? 

It is at this juncture (paradox) that Einstein and Hawking part company. If light stops in a black hole (Hawking) then time must stop also (Einstein interpreted). 

Conclusion?:  If black holes exist then a pure black hole would be virtually invisible because its only interaction with external space would be a massive warp in the space/time continuum.  A black hole could only be detected by observing light seeming to be bent and slowed down as it passed by the event horizon (outer envelope) of the black hole. 

Another interpretation (my own) is that if blackholes are actually massive accumulations of highly compressed matter, and not just a handful of matter whose mass is expanding exponentially (sub-light velocity) then what happens in a black hole is that hydrogen produces helium...  then combustion... and then millions of years later the combustion reaches the surface of the blackhole which is then transformed into a star. 
See also, The Pixie Dust Theory of Blackholes ©

What does all of this mean?  

It indicates that the universe, as we know it, is a vast vortex of energy.

It indicates that matter is stored energy (E=MC²) that experiences temporal distortions depending upon velocity. 

It suggests also ("As above, So below") that light seeking release from the confines of matter is the quantum essence of 'Metaphysics' (and the New Testament). If what it is that happens in a blackhole (a precursor to the birth of a star) the 'blackhole of self' is mirrored in the cosmos and then the transubstantiation of hydrogen into helium is a metaphor for spiritual enlightenment and ultimate liberation from the temporal realm of weight, mass, matter and time.