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I long assumed that the Earth is a "water planet" because water is mostly what you see from a distance. It wasn't until I did the math that I realized that is r
by sfink 2y ago
I long assumed that the Earth is a "water planet" because water is mostly what you see from a distance. It wasn't until I did the math that I realized that is really about wet rocks in space vs dry rocks in space.
Earth isn't made of water, it's just a damp rock. Or a bowling ball that you squirted a dozen times with a spray bottle.
- spencerchubb 2y ago> damp rock lol it's funny when you put it that way
- oorza 2y agoCloser to a bowling ball that picked up a drop of beer from your hands.
- nwiswell 2y agoThis didn't sound right, so I did the math. The volume of all water is 1,386,000,000 km^3, which is then 1.386e+21 liters, or right about the same number of kilograms. The mass of Earth is about 5.972e+24 kg. So the percent fraction by mass is 0.0232%. A "drop" is typically estimated at 1/20th of one mL, which is then 0.05 grams. We can estimate the mass of a small-ish bowling ball at 5kg, or 5000 grams. 0.05 / 5000 * 100 = 0.001%. So it's an order of magnitude shy, but that's still closer than I expected! It's about 1 ml of beer on a bowling ball - a small splash. Or maybe a very large drop.
- silisili 2y agoThanks. This really put it in perspective for me better than the image or other analogies!
- arrowleaf 2y agoYou'd have to use the volume of earth, not the mass. Google tells me that lava is ~3x denser than water.
- rachofsunshine 2y agoLava is not really representative of the Earth as a whole, as it turns out. The mantle (which is the vast majority of Earth's volume) isn't a liquid, it's a squishy deformable solid. Magma that comes from the mantle is only liquid because of the removal of pressure or the addition of water; it wasn't liquid down there. And a lot of lava comes from crustal melting, not mantle material. Earth as a whole has a density about 5.5x that of water.
- ahazred8ta 2y agoThe sphere of water would have a surface gravity of 0.016 g, 1.6% of Earth's gravity, 1/10th of the Moon's gravity.
- lazide 2y agoAlas, the atmosphere it could hold would be insufficient to avoid it all vaporizing.
- nvader 2y agoA dash.
- outop 2y agoThe picture already answers this question. If the earth was a bowling ball the blue sphere would be much bigger than a single drop, maybe slightly bigger than a popping boba, the size of a small grape?
- ars 2y agoEarth isn't even really a "rock", it's mostly a ball of iron. It's a ball of iron covered with rocks (i.e. metal oxides) cover with water (i.e. hydrogen oxide).
- zamadatix 2y agoI don't buy it. Even allowing counting iron as separate from what rocks can be composed of (and using mass instead of volume) you still have 30.1%+15.1%=45.2% of the Earth as oxygen and silicon (which are most certainly part of what makes a rock) at which point you've already disproved the claim Earth is more a ball of iron than a ball of rock. A ball of iron covered with a ball of rocks is a more fair statement though, and I'd agree with that. It's just that center ball isn't most of what makes up the Earth (by any measure).
- ars 2y agohttps://s3-us-west-2.amazonaws.com/courses-images-archive-read-only/wp-content/uploads/sites/567/2015/09/21153205/800px-Earth-crust-cutaway-english.svg_.png https://s3-us-west-2.amazonaws.com/courses-images-archive-re... Everything up to and including the mantle is either iron or has a lot of iron. But to your point the mantle also has a lot of silica. So I guess it depends on your definition of "mostly".
- dredmorbius 2y agoMass is the defining characteristic of a quantity of matter. Given that much of the iron is under far higher compression than the outer layers of silicate rock, this also advantages iron. By mass, iron (32.1%) is still a minority constituent of the Earth. <https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements#Earth https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...>
- Intralexical 2y ago"Squirt with a spray bottle" is a nice euphemism for throwing asteroids at. https://en.wikipedia.org/wiki/Origin_of_water_on_Earth#Asteroids https://en.wikipedia.org/wiki/Origin_of_water_on_Earth#Aster...
- stavros 2y agoThey mean in terms of the ratio of water to rock.
- sfink 2y agoWell, the spray bottle was more to spread the water out into a thin layer as opposed to something like crashing an icy asteroid in at one spot. I have a mental image of a gigantic cosmic being grabbing the Earth, wiping off the wet stuff with a rag, and bowling it at Proxima Centauri.
- noisy_boy 2y agoReminds me of the ending of Men In Black (1997).
- RIMR 2y agoThe ballpark math is easy to do in your head too. The diameter of Earth is 8,000 miles, and the deepest point in the ocean, the Mariana Trench, is only 7 miles deep. It's immediately apparent that the oceans are tiny by comparison to the rest of the mass that is Earth.
- aspectmin 2y agoAn interesting exercise is to do this exact same calculation with the atmosphere.
- jvm___ 2y agoIt's fun to scale down the Earth's depth to a 8 metre long measuring tape on the floor and then having kids guess things lik, how deep is the ocean, how deep is the deepest hole we've ever dug, how high is the atmosphere. Adding in how far of a drive is it to X place or how far of a walk is it, is also fun.
- tejohnso 2y agoNeil DeGrasse Tyson says the earth scaled down to the size of a billiard ball would be smoother than any billiard ball ever made.
- poikroequ 2y agoNot completely accurate, it depends on your definition of smoothness. The Earth scaled down to the size of a billiard ball would have a texture more like sandpaper, certainly not what most people would consider smooth.
- nirav72 2y agoSandpaper also come in different roughness. So in this case maybe a 300-400 grit sandpaper?
- hnburnsy 2y agoThis was analyzed and the results were mixed... https://billiards.colostate.edu/bd_articles/2013/june13.pdf https://billiards.colostate.edu/bd_articles/2013/june13.pdf >So, based on the data, just how smooth is a CB? And how does this smoothness compare to the surface of the Earth? The highest point on earth is Mount Everest, which is about 29,000 feet above sea level; and the lowest point (in the earth’s crust) is Mariana’s Trench, which is about 36,000 feet below sea level. The larger number (36,000 feet) corresponds to about 1700 parts per million (0.17%) as compared to the average radius of the Earth (about 4000 miles). The largest peak or trench for all of the balls I tested was about 3 microns (for the Elephant Practice Ball). This corresponds to about 100 parts per million (0.01%) as compared to the radius of a pool ball (1 1/8 inch). Therefore, it would appear that a pool ball (even the worst one tested) is much smoother than the Earth would be if it were shrunk down to the size of a pool ball. However, the Earth is actually much smoother than the numbers imply over most of its surface. A 1x1 millimeter area on a pool ball (the physical size of the images) corresponds to about a 140x140 mile area on the Earth. Such a small area certainly doesn’t include things like Mount Everest and Mariana’s Trench in the same locale. And in many places, especially places like Louisiana, where I grew up, the Earth’s surface is very flat and smooth over this area size. Therefore, much of the Earth’s surface would be much smoother than a pool ball if it were shrunk down to the same size.
- samstave 2y ago[flagged]
- netsharc 2y ago> Earth isn't made of water, it's just a damp rock. Or a bowling ball that you squirted a dozen times with a spray bottle. Yeah, the image with the oceans being dry is wow-inducing... On further thought, of course it'd be very close a sphere, because gravity forces it to be. A sphere where e.g. a slice of it is water (imagine a clementine with one of its segments being water) would be very wobbly if even possible at all..
- hughesjj 2y agoYup, the mere fact that we can have oceans and continents on a planet means we can only have so much water, lest we become a water world or something more like mars. I do wonder if the OP includes water locked away in rocks though, to my understanding the majority of the water is in the mantle and not even the oceans, but my source is my butt for that one
- jvanderbot 2y agoThere are moons out there that are more like giant snowballs - so much water that it dwarfs even our reserves.
- DaoVeles 2y agoThere was an old sci-fi trope that the reason aliens attack earth is to get at our water. The problem with that was, 1. there are better sources of water (the oort cloud) and 2. they aren't stuck in an gravity well.
- kristianpaul 2y agorock that moves and is hot inside so a magnetic fields generates from its motion and protect us from the sun particles
- hoseja 2y agoIt is quite incredible that there is just enough water for a continuous ocean and also dry land, not either just a couple ponds or a waterworld.
- Kaibeezy 2y agoOceanus's ocean tosses with slow, tall waves, beneath a pale blue sky. The colonists live in tall cities of steel and concrete with buildings sealed against the planet's harsh environment, on platforms floating on the planet-wide ocean. They spend their time pursuing art, leisure, and spiritual fulfilment, while automatic machines take care of their material needs.
- keepamovin 2y agoMars is the same, right? Just the water is locked 20 - 200km beneath the surface from recent discoveries.
- veunes 2y agoThis water is locked away in the form of ice
- veunes 2y agoIt's true that while water covers about 71% of Earth's surface, it's just a thin layer compared to the planet's overall volume.
- zuminator 2y agoEven so, it's still a pretty substantial amount. Larger than Ceres, for example.
- rmbyrro 2y ago> I long assumed Understandably, since, in this case, surface area is more intuitively captured by our brains than volume. Also because we are very small. The amount of water, from our perspective, makes it look like a water planet.