00:00You know, those fluffy cumulus clouds you see in the sky weigh as much as a Boeing 747
00:07or 100 elephants.
00:08Hey, if you don't believe me, let's do the math!
00:12Scientists figured out that the density of water inside a cumulus cloud is around a half
00:16a gram per cubic meter.
00:19Clouds come in all sizes, but an average cloud of this type is shaped somewhat like a cube
00:24and has a volume of 1 billion cubic meters.
00:28When you multiply it by density, you get an impressive result of slightly over a million
00:33pounds.
00:34And, in case you were wondering, this giant stays afloat because its density is lower
00:39than that of the air surrounding it.
00:43Giraffes are 30 times more likely to get struck by lightning than you are.
00:47There were 5 official fatal cases involving giraffes and lightning between 1996 and 2010.
00:54Perhaps since their population worldwide is just around 140,000 during that period,
01:00the fatality rate is rather high per thousand of giraffes per year.
01:04Lightning bolts love tall objects, so giraffes are unfortunately an easy hit.
01:10But scientists think they might've learned to deal with it and seek shelter during a
01:13thunderstorm or move quickly to thickly vegetated areas.
01:19The oldest animals on Earth are glass sponges.
01:22They can live up to 15,000 years.
01:26Scientists found the oldest glass sponge in the Ross Sea, a part of Antarctica.
01:30In another part of the world, the East China Sea, scientists found the skeleton of a glass
01:35sponge that lived for about 11,000 years.
01:39These sponges might've been around during the last ice age.
01:42They lived their whole lives stuck to hard surfaces, filtering water to snack on bacteria
01:47and plankton.
01:51So our Earth is spinning more slowly now, which means our days are getting a bit longer
01:55over time.
01:56Long ago, I wasn't around then, a day on Earth was only about 19 hours, but then it grew
02:02to 24, mostly because the Moon's gravity pulls on Earth and slows it down.
02:08Different extreme things go on in nature that can change the speed of Earth's spin in the
02:12short term.
02:14An earthquake in Chile in 2010 may have made our day a little bit shorter, according to
02:20scientists.
02:21But by 2020, the days have been getting longer again.
02:26Scientists still can't decide if water is actually wet or not.
02:30Some of them say water isn't wet itself, but it can make other things wet when it sticks
02:34to them.
02:35Others think water is wet because it's a liquid and has moisture.
02:39Water can feel wet because it cools your skin as it evaporates.
02:43How wet something is depends on two forces.
02:47Cohesive forces that keep water droplets together and adhesive forces that make water stick
02:52to things.
02:53Water doesn't stick well to waterproof fabrics, and they stay dry because cohesive forces
02:58are stronger in that case.
03:01Guess what?
03:02There is no map of the world that would be 100% accurate unless it's life-sized.
03:08Our planet is round and paper is flat, duh!
03:11Back in the 16th century, Gerardus Macator designed a cylindrical map projection that
03:16is still used and named after him.
03:18This concept is good for navigation because the north is always up, but the top and bottom
03:23parts get stretched out.
03:25So Greenland looks 14 times larger than it really is, and Alaska is the size of Brazil.
03:32Around 4 billion years ago, Earth's atmosphere was very different from what we know and love.
03:38But volcanoes saved the day.
03:40Tons of them were erupting all over the place, spewing out carbon dioxide.
03:45This gas filled the sky and made up most of the atmosphere.
03:49Tiny early plants used that carbon dioxide to grow by photosynthesis and give out oxygen.
03:55One of the theories says that the steam from all the volcanoes cooled down and turned into
04:00water and gave us the oceans.
04:02It took about 2 billion years for enough oxygen to fill the air so that animals could live
04:07and breathe here.
04:10Now if for some reason you ever decided to stack all the world's germs and bacteria
04:15on top of each other, they would stretch for 10 billion light-years.
04:19But you wouldn't even see this threat because it would be about 75 times thinner than a
04:25human hair.
04:26If you wrap this long line of bacteria around our galaxy, the Milky Way, it would circle
04:31around it more than 20,000 times.
04:34Ooh, my brain!
04:38It turns out there's rust on the Moon, and it may have traveled all the way from Earth
04:42to get there.
04:43Now rust usually needs oxygen and water to form, and the Moon has almost none of either.
04:49But when this celestial body passes through a part of space called Earth's magnetotail,
04:55oxygen from Earth can reach it with solar winds.
04:58This oxygen may have combined with tiny amounts of water and iron on the Moon's surface to
05:02create rust.
05:06Now even a tiny asteroid can knock our planet out of its orbit, but don't worry, you probably
05:11won't even notice any difference.
05:14The effect of an impact will depend on many things, like how strong the space rock is,
05:19how fast it's going, and what kind of ground it hits.
05:22Most of the time, when space rocks hit Earth, they break apart or turn to gas before they
05:27reach the ground.
05:28But big ones, like the one that wiped out the dinosaurs, can cause huge problems, like
05:33big waves, earthquakes, and even change the weather.
05:38The Earth isn't solid like a rock on the inside, but more like squishy clay because of the
05:43very high heat and pressure deep underground.
05:46This squishiness allows the mantle to move very slowly over millions of years, and that's
05:51why we get earthquakes, volcanic eruptions, and the shifting of continents.
05:57During the last ice age, huge heavy glaciers sat on top of Earth's surface, pressing down
06:02on the squishy mantle underneath.
06:04This made the mantle sink a bit.
06:06When the ice melted, the mantle started pushing back up, and the land began to rise again.
06:12Even today, in places like Canada, Greenland, and Scandinavia, the land is still rising
06:17because of this.
06:20Our planet is covered with cosmic dust.
06:23About 5,000 tons of it reach the surface of Earth every year.
06:28This interstellar substance is smaller than a grain of sand and often even thinner than
06:32a human hair.
06:34Scientists go all the way to the middle of Antarctica, where it barely snows.
06:38And the snow is super clean to spot those particles.
06:41Most of this dust comes from comets.
06:45If you're an introvert, Greenland is the ideal place for you.
06:49It is the least densely populated area in the world, with only 0.1 person per square
06:54mile.
06:55Well, I've never actually seen a tenth of a person.
06:58Anyway, most of Greenland is covered in ice, so people live mainly along the west coast.
07:03Oh, and by the way, it's been inhabited for over 4,500 years, so it must not be that
07:09bad after all.
07:12Guess what?
07:13The ground you walk on is actually recycled.
07:16First, hot melted rock from magma comes to the surface and cools down to become solid
07:22rock.
07:23Thanks to tectonic forces, the rock gets pushed up to the surface.
07:27Over time, wind, rain, and other forces break pieces of the rock off.
07:31They get carried away and eventually settle down in layers.
07:35These layers get squished together, forming sedimentary rocks like sandstone.
07:40Sometimes if these sedimentary rocks get pushed deep under the Earth's surface, the heat
07:44and pressure cook them into a new type of rock called metamorphic rock.
07:49A long time ago, life on Earth might've been purple instead of green.
07:54A molecular biologist from the University of Maryland thinks that the very first microbes
07:59used a special molecule to capture sunlight that made them look purple.
08:04Today, plants are green because they use chlorophyll to absorb sunlight and turn it into energy.
08:09But before chlorophyll existed, retinol molecules did the same job.
08:14It soaked up green light from the sun and reflected red and purple light, which made
08:18the microbes look violet.
08:20And like little tiny grapes.
08:22Really.
08:23That's it for today!
08:27So hey, if you pacified your curiosity, then give the video a like and share it with your
08:31friends!
08:32Or if you want more, just click on these videos and stay on the Bright Side!
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