While on field trip with astronomy class, sighted noiseless craft flying at a very high rate of speed while performing erratic flight

Tonight at about 20:00 hrs PST, My girlfriend and I joined our astronomy class in a somewhat remote area of the Oakland hills for the purpose of conducting some stargazing using binoculars. At about 20:30 some of our classmates noticed what appeared at first like a satellite in the sky.  My attention was drawn in the direction of the object and  I began to observe the object through my binoculars thinking as well that we were looking at a satellite. It was travelling at a high rate of speed . At first it did not raise any suspicion because that is what one expects from a satellite. But very soon this changed due to the fact that it was tracing a somewhat erratic flightpath as it crossed the sky from about where  sagitarius was at that time of the night (which was at a relatively low angle)up to the region in the sky where the constellation andromeda was located.  I would say that it accomplished this  in about 25 seconds max. A strobing light sometimes emitted from this object which appeared to be at such a distance that not even my 10*50mm binoculars could resolve some discernable shape.  Additionally, the object emitted a greenish light. The object made no sound of any kind.  Now as it reached andromeda, it suddenly made a tight turn and at that moment I noticed that a second object came into view.  It appeared to be racing to meet the 1st object and as it gained on the first object, I noticed that they both began to decelerate at a very steady rate until both were flying at the same speed.  Suddenly the first object began to rapidly accelerate and as this occured, the angular distance between the two increased and at that point I could only follow one of the objects.  I continued following what I identify as the first object as it headed due north now when suddenly the second object closed in on the first as it came into my field of view in the binoculars.  About 2 seconds passed when abruptly I noticed that a third object had now come into my field of view.  The 3 then continued on this norhterly course together until they disappeared behind a hill and I could follow them no more.
 Now I want to say a few things regarding this "potential" sighting. Firstlly, I have been fascinated with aircraft all of my life since I can remember being alive.  I go to airshows several times a year and have seen many different types of military aircraft in action. Military aircraft are to my knowledge very noisy vehicles.  The vehicles that I witnessed this night made absolutely no sound whatsoever. Secondly to bolster my 1st point, I would like to state that the objects accelerated rapidly at least twice that I can remember and not once was there any sound nor the appearance of the prominent flame that I could associate with that which is emitted when jet aircraft engage their afterburners in order to command the  impresive rate of acceleration that these vehicles displayed.  Thirdly, we live in the San Francisco   Bay area.  It is very active with air traffic given the two major airports which are  located so close in proximity from one another (literally right across the bay from one another)  The notion that the military would conduct such risky maneuvers in such an area of the sky that is already rife with civilian air traffic is in my opinion not viable unless one is willing to accept that the military does not take the issue of civilian air traffic safety seriously.  If we are to then accept that maybe these objects were military jets flying well above the civilian air traffic corridor, let us say perhaps above 20,000 feet, then these jets would have had to fly at the speed of sound at the very least in order to cover the aforementioned area of the sky  and they would have surely generated a sonic boom.  But as  I say, not a peep eminated from these vehicles.  conversely, if they had been flying at a lower altitude which is the only other explanation that could explain the large sky coverage executed by these vehicles in short a short period of time, then surely, unless these are military jets with a sophisticated new propulsion technology, they would have definitely made a lot of noise.
 I cannot definitely say that what I saw were craft from another world, but they sure did not behave in any way that I could attribute to modern military jet aircraft.  If you have any feed back for me regarding this event i.e. any new propulsion technologies that you may have heard of, please drop me a line.