I trust the results because of what was shown.
It's the basic's that matter in this, because here you have two objects attracting to one another without any external influences, such as electricity, wind, etc. Basically anything
but the hope of gravity. The smaller objects moving simultaneously towards the larger, "sister" objects without said influences is a HIGH indicator of the force we call gravity.
Here's the other reason why I trust it to be gravity.
The objects are not magnetic. If they were, they would have been attracted to the larger objects nearly instantaneously, based on the nature of the 4 natural forces in the Universe:
http://library.thinkquest.org/27930/forces.htmElectromagnetism is stronger than gravity. If you take a toy magnet (one of those cheap ones) and hold a paper clip to it, the paper clip sticks to the magnet, and does not fall to the ground. This demonstrates how weak of a force gravity is.
That said, if the sphere's were magnetic, they would have been attracted to each other nearly right away. They cannot exhibit weak or strong nuclear force (the forces [don't ask me how or what, I do not know, nor are they overly important to prove or disprove gravity] that hold atomic nuclei and atoms together) due to the scale of the objects, so the only other "logical and obvious" choice is gravity. Which accounts for the amount of time it takes for the smaller sphere's to be directly next to the larger sphere's, because it is still a weak force.
I'm sure that performing the same experiment with the same size "small" sphere's and a pair of much larger sphere's would exhibit the same result's at a slightly faster pace. Which also shows that the earth has to be very massive to hold all of us to it in RE.
Although the experiment does not explain "how" it works, it does very well show that gravity indeed does exist and behaves very much as we have described it since Newton first coined the notion about gravity.
UA cannot be applied here, and it can also be strongly dismissed as the reason and mechanism for gravity on earth. Because otherwise, you would need to apply the UA to the objects in the experiment and I don't think anyone here knows how to do that.