I had ridden my bicycle along the Alameda Creek trail to the foot of the SF Bay. I was lying down on a bench resting and staring up at the clouds at 3:15pm when I suddenly spied a small, round, whitish object moving about 2-3 times the speed of an airliner. It was less than a mile east of my position. The object was spherical with a dull white color with no lights to be seen. There were clouds overhead (see photo) and I could see that the object was definitely lower than the clouds as I could clearly see it as it passed under them. If I had not seen the object as I was staring up then I probably would have never seen it. Since there were no lights and it was a dull white I really had to try hard to follow it's flight pattern in the bright mid day sun. I considered taking out my phone for a picture but realized it was too high for a good photo and if I looked down at my phone, I would probably not be able to follow the object. The object was flying in a straight line from south to north less than a mile east of my position. (see photo) I lost sight of it maybe 10 miles north over Hayward or San Leandro. It moved about 2-3 times faster than an incoming airliner but it appeared a lot smaller. I would say that from my vantage point, the object was about 1/5 the size of an average jetliner. It had a roundish shape, no lights, no sounds, I watched it for maybe a minute as it flew in a straight south-north line and disappeared out of my site. I noted the time was 3:15pm. A few weeks earlier I spotted a similar looking object, on a similar course at a similar speed at 9:15pm. It stayed at a steady altitude and a straight line, was lower than the cloud cover and was flying right over the busy SF Bay airport traffic on it's way up the eastern shore of the SF Bay.