The bubbles you see in water are air bubbles. they rise to the top then pop when they reach the surface.
When water boils, it turns to a gaseous state (water vapor). The bubbles are simply water vapor bubbles rising from the bottom to the top.
Down, if you hope to heat your pool with it the bubbles (in theory) will heat up from the flat side. As there is more surface area from the bubbled side more heat (energy) will transfer to the water. I've never read any studies myself but I've read differing opinions from people in other posts. Some state the the solar cover actually blocks the sun and less heat is transfered on sunny days and that it is more beneficial to use take the cover off. Personally I find that if you leave the cover on when not using the pool, except when it's raining, the temperature stays the highest. Ensuring the cover is clean and there is no standing water on top of the cover really helps.
I have had several pool covers over the years, blue, blue and black, clear, clear with diamond shaped bubbles. Last year I purchase a "Gold Series" solar cover. It is blue on the top with a reflective good metallic layer that faces down. This cover is by far the best cover I have ever owned. It's high quality but more importantly I have 5-7 more degrees in water temperature then I have ever had. In July I had to take it off the water was so warm. Very pleased.
My answer is, that there are air bubbles in the bottom of it, (WHEN ITS BOILING) Than those air bubbles rise to the top, & That's how hot water bubbles more than cold water.
The water displaces air, which moves to the top. It comes up through the water layer, creating bubbles.
because i told them to do so. ;)
The bubbles in boiling water are steam or vaporized water. The bubbles initially do not reach the surface of the billing fluid as the colder water away from the hot bottom cools the steam turning it back to liquid. WHen all the water is at 100oC the bubbles reach the top.
As I read your question - - - you want to put a solar cover over the filter. If you actually mean can you put the solar cover on the pool surface and run the filter and pump too. BTW, the filter does not move the water, the PUMP moves the water. The pump is the only piece of equipment that you would be used to run th ewater thru the filter. The pump is like the heart of the equipment pad. Then yes you can do both. The solar cover when installed as it should be - on the water - has no signifigence with regard to the filter ( the large tank). The purpose of running the pump either with the cover on or off would be to move or circulate the water. With a solar cover on the surface of the water - only the top two feet of the water is warmed. The rest of the pool remains cooler. Circulating the water would move that warm water and mix it with the cooler water. Think about it.
I have done this with my solar cover without any trouble
the water is evaporating which pulls the water into a gas and the air bubbles take up at that space, come to the top, and dissappear so if its out long enough the bubbles might go away
yes does bubbles at the top of the water are made by spit