I could not think of anything more abstract than...

TIME

Click on a photo to enlarge

This is a composite image. I have shot the hourglass myself.
Nikon D3s Nikkor 50mm 1.4G @ f/5.6 1/100 iso 640

And added these images to the composition after gray-scale conversion.

Source

You probably will not be able to see the clouds very well :) Source

Source

MonoMad Photographic Contest
@brumest/monomad-photographic-contest-week-4-topic-abstract-please-read-the-rules

Follow me @bescouted if you liked it :)

Cheers,
David