top | item 33656864

(no title)

rikkipitt | 3 years ago

The way I remember Earth's approximate mass is the fact it's 10 times Avogadro's number in kg.

My physics teacher always had a great way of drilling in these tidbits.

discuss

order

opwieurposiu|3 years ago

Yes and the circumference of the earth is about 40 million meters. This is because a meter was originally supposed to be 1/10E6 the distance from the equator to the north pole through Paris.

Someone|3 years ago

Nitpick: 1/10⁷, not 1/10⁶. They picked the power of ten that gave a reasonably-sized unit of length.

They also made things complex by then picking a unit of mass that’s inconsistent with that: a gram isn’t the mass of 1m³ of water, but of 1/10⁶ m³ of water (a cubic meter is 10³ liters, and a liter of water weighs 10³ grams)

Centimeter-gram-second (https://en.wikipedia.org/wiki/Centimetre–gram–second_system_...) really is superior in that sense (but of course, that’s relative to the arbitrary choice of using water to convert between mass and volume, and from that, length)

mncharity|3 years ago

> The way I remember Earth's approximate mass is

For me, it's: Earth is a blue marble - in "Mega-view" (Mm zoomed to mm) - with a diameter of a baker's dozen Megameters. The volume of a ball is one half of its enclosing box, so that's ~(1E7)^3 or 1E21 m^3. Earth is rock (3 Mg/m^3) and iron (8 Mg/m^3) and averages 5 Mg/m^3. Or just bracket it - water,lead,gold is ~ 1,10,20 Mg/m^3). Giving an Earth mass of 5E24 kg. Actual value 6E24 kg. Brackets of water and lead give 1E24 to 11E24 kg.

> a great way of drilling in these tidbits

For me it's: Arm-sized, hand-sized, fingernail-sized, and "tiny"-sized, are 1000, 100, 10, and 1 mm. Zooming these by 1000^n gives scale-model "views". Mega-view with planet balls, kilo-view with cities in your palm, meter-view with buildings in hand, micro-view with red blood cell M&M's (yum), nano-view with virus balls (chewy shell, stringy inside), pico-view with H2O bumpy basketballs, femto-view with nuclei marbles. It's easier to remember how big things are, once they're toy-sized, and you've handled and played with them.

Just something I crafted years back. Resulting videos didn't seem to user test well. I was set to dust it off, doing rapid iterative development over gorilla street usability testing... in Spring 2020. Ah well.

vitiral|3 years ago

Take ten moles of earth, fire, wind and water. What do you have? Captain planet!

zem|3 years ago

nice. filing it alongside the pi * 10^7 seconds in a year