Gravity can be expressed, as far as I can tell, as a warping of space-time.
This warping apparently propagates at c and only asymptotically approaches flatness based upon the distance from the gravity well. In other words, all of space-time is warped by ALL matter and energy in the Universe.
But, I could be wrong.
Moderating
I don’t think we need to rehash the nearly infinite previous discussion on this subject here. Let’s stick to the OP.
Colibri
General Questions Moderator
And then I confused the issue by bringing up finite infinitesimals in the form of Robinson’s hyperreals, where the notation “0.000 … 1” is still undefined but the concept of “A number strictly less than every positive real number and strictly greater than zero” is given a rigorous definition.
So, in the real numbers, 0.999… = 1 and (0.999… - 1) = 0. In other systems of numbers, however, it’s possible to give a logically consistent definition to “a number that is infinitesimally less than 1” and do perfectly good math on that foundation.
However, in physics, magnitudes (the kinds of values we’re talking about here) are always expressed as real numbers, so all of this is rather academic.
To me, this brings up the question of what is ‘noticeable’, if there’s nothing else in the universe. No, the specks probably wouldn’t be a millimeter, (or a fraction of their diameter) closer in 100 years, but who says that 100 years is a significant period of time for such a universe.
Eventually the attraction between them will have an effect. 
I decided to check out just how much force would be exerted between 2 paperclips placed 4 light years apart. I’m a little rusty so I’ll show my work in case anybody sees something glaringly obvious that I missed.
For the force of gravity I used the equation F=(G * m1 *m2) / d2
for the mass I used 0.001 kilograms, the size of a large paperclip, and the distance I used 3.78*10^16 meters.
This gave me a total gravitational force between the 2 objects of 4.45*10^-50 Newtons.
Next I plugged this into F=ma to find the acceleration of one of the paperclips. Total acceleration is 4.45*10^-47 m/s^2
At that rate of acceleration I calculated how much the paperclip would move in 100 billion years, approximately the total lifespan of the universe using the equation d= (a * t^2) / 2. I used 3.16*10^18 seconds.
So, total distance moved on one paperclip over the lifespan of the universe is: 2.21 * 10^-10 meters. This translates to just a little over 200 hydrogen atoms distance.
So, yes, there is gravitational attraction at that distance but even over the lifespan of the universe it won’t make any difference.
According to newtonian gravity and general relativity…continuum mechanics…gravity has an inverse square geometry dropping off to infinity.
Do EM, strong and weak nuclear forces with known quantum mechanical geometries of force strength, drop off to zero at a finite range?
No theory predicts any of the fundamental forces falling off to zero at any finite range. In fact, the raw color force (of which the effective strong force is only a higher-order residual) is believed to remain constant at large ranges, not diminishing at all. The weak force and the residual strong force, however, approach zero very rapidly, for any macroscopic distance.
In regards to the specks at each end of an otherwise empty universe, I have read that our universe is expanding away from the point of the big bang at an ever increasing rate. Wouldn’t gravity’s infinite reach ultimately slow the rate of expansion, eventually causing all matter in the universe to reverse direction and meet once again at the point of origin? Is there a conflict between the theory of the infinite reach of gravity and the observation that the speed of the big bang expansion is increasing?
well one of the main reasons we know that we live in a 3 (spatial) dimension universe is that stable orbits can exist - if humans (and the planets and…) existed in 4D then gravity would be marginally stronger - and stable orbits couldn’t exist
Density (as well as pressure) acts decelerates t expansion i.e. the denser the and it’s possible that the rate slows down so much it becomes negative (i.e. the Universe re-collapses), on the other hand it may only decelerate it so that it approaches some non-negative constant rate as the density approaches zero. And that’s not even considering dark energy.
There’s no conflict between expansion and gravity: expansion comes from general relativity which is a gravitational theory, however it’s not really correct to think of it as gravitational force pulling against expansion (though it is often stated that way) as general relativity doesn’t model gravity as a force and the way that density acts against expansion doesn’t have a Newtonian limit in which it can be approximated as a force.
After reading this first sentence, I was expecting you to tell us what happened when you got 2 paperclips and placed them 4 light years apart. 
I believe that one of the current issues in cosmology today is the observation that the expansion of the universe is* not *slowing down, as one would expect from the effects of gravity, but is, instead, increasing (!) - contrary to what used to be common sense. This has supported the idea of dark matter and dark energy and has caused some degree of upheaval in the field. Clearly, some of those here who know this topic well can weigh in, but I think I have the right notion.
Basically, if ordinary gravity acting on ordinary matter were all that was at play in the Universe, the expansion would indeed be slowing down. It might eventually reverse, or if it’s going fast enough you might get an escape speed-like phenomenon where it asymptotically approaches some speed. But either way, it should be slowing down.
It isn’t. The logical conclusion is that there’s something other than ordinary gravity or ordinary matter at play. It can be described in terms of either, but the current trend among cosmologists is to describe it in terms of a sort of “stuff” that isn’t ordinary matter, called “dark energy”. In fact, this mysterious dark energy stuff appears to make up over 70% of all of the stuff in the Universe.
Our experiences tells us that the space between objects, if neither object is moving relative to one another, is finite and unchanging. However, on the very large scale of the universe we have learned that new space is constantly being created between these 2 objects and gives the appearance that the 2 objects are moving away from each other. The further away the object is the more space is being created and the faster it appears to be moving away (detectable to us as a redshift). In our own universe the galaxies we see furthest away from us appear to be receeding at a very large percentage of the speed of light! But locally they’re not moving anywhere near that fast, and neither are we. It’s just the expansion happening between us that makes it appear that way which is why this doesn’t violate relativity. In fact, there is an edge to the universe beyond which we will never be able to see. Galaxies that may very well exist there are moving (from our point of view) faster than the speed of light away from us so we’ll never see them.
In fact the furthest objects we see in the observable Universe are in fact receding away from us faster than the speed of light (up to just over 3 times the speed of light in the favoured Lambda-CDM concordance model of the Universe). In fact there are even objects in the observable Universe which were receding from us faster than c when the light we currently see from them was emitted!
Incidentally, this is the answer to the OP - the gravity of an object cannot reach past the visible edge of the universe. So that’s how far it can reach.
What about the super earths?
What about them? They’re bigger than our planet, but they’re still pretty small compared to gas giant planets (or stars, or star clusters, or galaxies…).
What about yo’ mama?
Yo mama’s so fat, her gravitational pull extends infinitely at the speed of light.
Yo mama so fat she attracts galaxies in every dimension!