Riddle: Julie is going on an extended trip for three weeks. She lives in a remote area where there are frequent electrical power outages which can last up to three or four days. Julie has quite a bit of food in her freezer which would go bad if it thawed and then re-froze. She does have digital clock and a VCR which would flash 12:00 if the power went out. Unfortunately the clock and VCR flash even if the power only goes out for a few seconds. What can Julie do so that when she returns home she will be able to determine whether the power was out long enough to thaw her food? Asking a neighbor whether the power was out, isn't a reliable option because the nearest house is half a mile away, and one house may have power, while another house may have no power. She won?t be able to have a neighbor check on her house every day, and has no one to house sit.
Answer: One thing Julie could do is freeze a tray of ice-cubes, and turn the tray of ice upside down in her freezer. When she comes home, she should check the tray. If the ice cubes are still in the tray, the food is safe to eat. If the trays are empty, it's time to clean out the freezer. She will have to make a judgment call if the ice-cubes are only slightly thawed.