Concepts from science and nature are filled with our language's common phrases , idioms and spoken expressions. The unbelieving expression "Well, I'll be a monkey's uncle" has its origin in bitter disbelief over Darwin's writings on evolution. These colourful expressions bring spice  to our language. Yet certain well-used phrases from science are just plain wrong! Some are obvious, yet we use them anyhow. For example, a person who acutely shakes her head and says " A watched pot never boils" while you are waiting second after tiring second for test results to arrive or job offers to come in knows that if she sat down and watched a pot containing water on a stove over high heat for long enough, the water will eventually boil. However, a few phrases have less obvious scientific inaccuracies. Here are a few for you to consider. Once in a blue moon: This poetic phrase refers to something that occurs extremely rarely. A blue moon is the term commonly used for a second full moon that occasionally appears in a single month of our solar-based calendars. The problem with the phrase, however, is that blue moons are not so rare. They happen every few years at least, and can even happen within months of each other when the 29.5-day lunar cycle puts the full moon at the beginning of any month but February. The usage of "blue moon" as the second full moon in a month dates back to a 1937 Marine Farmer's Almanac . But before that, blue moons meant something slightly different. Typically, 12 full moons occur from winter solstice to the next winter solstice, but occasionally a fourth full moon in a season could be observed . In such a case, one of the four full moons in that season was known as "blue" Where there's smoke, there's fire: The phrase means that if something looks wrong, it likely is wrong. But let's step back. Do you always have to have fire if you see smoke? Answering that first requires defining 'fire" , Merriam--Webster's first definition of fire is " the phenomenon of combustion manifested in light, flame and heat". Combustion is the chemical reaction that occurs when fuel is burned in the presence of oxygen---denying a fire any of these three things will stop the fire; attempting to start a fire without any one of the three things will be impossible. In complete combustion---what occurs when you light a gas stove--- the fire produces no smoke. However, when most materials are burned, they have incomplete combustion, which means that the fire isn't able to completely burn all of the fuel . Smoke, then, can be considered to be a product of pyrolysis   rather than of fire itself. You're probably thinking---so what? To get the smoke, a fire needed to be present at some point, right? Not always. Diamonds are forever: Thanks to the DeBeers slogan , decorating your honey's neck, wrists and fingers with diamonds means true and timeless love. Of course, no object that you can hold in your hand can last forever. But diamonds have a special reason for being incapable of timelessness. Without the extreme pressures of the deep Earth where they formed, a diamond will slowly turn back into graphite , which is why the older a diamond is, the more inclusions it's likely to have. What common phrases _ when viewed under the microscope of science? Are you curious about the hidden knowledge of some " big" phrases ? Or perhaps you have the ability to uncover the secret of some unscientific phrases? Let us know! According to the passage, the blue moon   _  .
appears at the beginning of a month gains its modern meaning before 1937 presents itself quite frequently sometimes can never be seen by people in February