It is tempting to think that some materials are always heavier than other materials. For example, someone might say that metal is heavier than air. But it depends on how much of each material there is ...

Scientists have measured the density of liquid iron -- the main component of rocky planet cores -- under conditions similar to Earth's liquid core: 1,000,000 atmospheres and 4,000 degrees Celsius.

Q. This is a U.S. Customs hydrometer for spirits (temperatures 0 to 60 degrees Fahrenheit) with original box. I believe it was used in the bootlegging days. It has been in my family since before I was ...