On a beach, beyond the reach of the tide, two fairly large rocks have been sitting together, not quite touching, for generations of people. One rock is a dark greeny charcoal colour. The other rock looks like red marble. Neither rock is actually a rock however. Both are aliens from other planets, other galaxies. Both are from different places though they have ended up in the same place. Both are timeless. Their lives stretching out far beyond that of even the rocks the resemble.
None of the people who play and sun tan and swim on that beach have ever noticed anything odd about the rocks. Some of them have even sat on one or the other of the rocks and watched sunsets and tides. No one expected there was anything to the rocks, beyond being solid matter.
One day the rocks left the beach. They just took flight and moved to another location. The only thing they left was a still wet indentation in the sandy beach. Years later someone noticed the rocks were missing. They had a photo of the beach when the rocks were still there. But couldn’t remember seeing any rocks there for ever so long.
What things are there around you which you might not really notice, even though they are not small in size or significance?