What do you know today, that you did not yesterday?

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Cerrertonia Sep 2021 2:09pm, 24 Sep 2021 14,793 posts	0 Cerrertonia The atmospheric pressure on Mars is a bit under 1% that of the pressure on Earth. If there was a linear or inverse linear relationship between speed of sound and pressure, you'd expect it to be 100x greater (or smaller). If it was related to the square root of pressure, it would still be 10x greater or smaller. Air pressure has only a small effect on the speed of sound - it effects the adiabatic constant of the gas, but only by a tiny amount. The temperature on Mars is about 200K, the temperature on earth about 290K. The speed of sound is proportional to the square root of the temperature - and that accounts for most of the difference between the two. Looks like NASA has a nice webpage to explain it: grc.nasa.gov In an ideal gas, pressure has zero effect on the speed of sound, because the terms for pressure and density cancel out. And at the temperatures and densities we're talking about for both Mars and Earth, both Carbon Dioxide and Nitrogen behave almost exactly as an ideal gas.
Diogenes Sep 2021 10:09pm, 24 Sep 2021 62,981 posts	0 Diogenes Bruno Brookes lent Bob Harris £130k to buy a flat. The bottom dropped out of the market and Harris couldn’t make the repayments. Brookes started charging £1300 a month interest and eventually took him to court to repossess his assets, including his records. Harris was able to keep his collection as the court judged them tools of his trade.
swittle Sep 2021 9:24am, 25 Sep 2021 79,683 posts	0 swittle [Whispering Bob's a tough old bird :)]
NDWDave Sep 2021 8:28pm, 25 Sep 2021 15,713 posts	0 NDWDave What peely wally means
Night-owl Sep 2021 8:41pm, 25 Sep 2021 37,871 posts	0 Night-owl What peely wally means
Dvorak Sep 2021 8:41pm, 25 Sep 2021 23,503 posts	0 Dvorak [ ]
Night-owl Sep 2021 10:17pm, 25 Sep 2021 37,874 posts	0 Night-owl [Think you Scottish fetchies ought to get together and write a book on Scottish terms would look great with illustrations]
Lip Gloss Sep 2021 10:21pm, 25 Sep 2021 54,843 posts	0 Lip Gloss Fa wiz lookin a wee bit wabbit?
mr d Sep 2021 10:25pm, 25 Sep 2021 5,316 posts	0 mr d That the pledge of allegiance in the USA used to include the Bellamy Salute. Think you can spot why they got rid of it in 1942.
macca 53 Sep 2021 9:25am, 26 Sep 2021 29,143 posts	0 macca 53 😳. Wow, definitely didn’t know that (or that it had a name)