I chose this photo because it's different and unexpected (and because it turned out quite decently.)
Regarding yesterday's image. The Rubik's Cube appears to be balancing on one corner because it is (with the help of an Oxo cube and a glob of blu tac.)

Kim. I probably won't use thermometer for T - I have other plans. So just for you I've included the image below. Although it's a nice clear image and shows the mercury well I didn't like that shadow and I just couldn't get excited about the photo as a whole. The answer to the puzzle is given below. Let me know if your hubby was right.
JuzzyDee. Yep. I have plans for Saturday - thank you for asking. This coming Wednesday however is another matter at this stage!
Tombaretto. Good thinking but Quente wasn't the word I was after.
Whalelight. Looks like you got it! Well done. Another name for Mercury is "Quicksilver".