The west coast ridge of high pressure is staying put for the next week, leaving us warm, dry, and occasionally sunny. High temperatures will be well above average throughout the next week, and while we may have occasional cloudiness, it’s very unlikely we will see any precipitation for at least another week.

Whale sound

Yesterday, Al asked if sound travels faster in cold air (it doesn’t.) He follows that up with: “Conversely, because water molecules are farther apart in cold water, do sonar waves travel slower?”

Once again, I need to correct something. It might make sense that since ice expands when it freezes, water molecules would get farther apart as it warms. But that’s not the case. Colder water does not have molecules farther apart than warmer. Water does not expand with cooling until after it freezes, so cold water (non-frozen) is denser than warm water. And just like in air, warmer water has molecules that are moving quicker, and therefore warm water transmits sound faster than cold water. So Al’s hypothesis was correct, but for the wrong reason.

sound_velocity_water

Of course, once water freezes and is in a bound matrix, sound then will travel faster through ice than liquid water of any temperature (about twice as fast.)

 

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