Weather -- Cloud types, thunderstorms, and tornadoes

This week, we continued our unit on weather and clouds.  First, we went through the different cloud types.

 Cirrus clouds are thin, wispy clouds that are very high up in the sky.  Cumulus clouds are puffy clouds that are pretty low in the sky.  Stratus clouds are flat, layered clouds that are low in the sky.  And cumulonimbus clouds are storm clouds that start low in the sky and quickly grow very tall.  Nimbostratus are flat rain clouds, and stratocumulus are flat but a little puffy.  Alto cumulus are small, puffy clouds higher up than normal cumulus, and cirrocumulus are tiny puffy clouds very high up in the air.  Lastly, cirrostratus are very high layered clouds that basically make a halo around the sun.
Next, we talked about how thunderstorm clouds form and become a thunderstorm.  Basically, warm, moist air rises quickly and forms big puffy clouds (cumulonimbus clouds).  At a certain point, enough water has settled that it starts to rain.  A typical thundercloud has strong winds around it, and often lightning and thunder.  We watched this movie for more information.  So we moved on to the topic of lightning and why it happens. This video was a very good explanation of how lightning happens and the different kinds of lightning.
Next, we moved onto tornadoes.  Tornadoes are something seen primarily in the United States, and specifically the middle section of the US is called Tornado Alley because so many tornadoes form there.

Here's a map of Tornado Alley.  Basically, when warm air from the Gulf of Mexico hits cold air from Canada, thunderclouds form and some of them have a rotation inside the cloud.

That rotation can get very strong, and then it can send down a funnel cloud.  If that funnel cloud touches the ground, it becomes a tornado, and it can cause great damage.  There is a scale of severity of tornadoes, and the highest level is F5, which can smash houses completely.  It can be unpredictable when a tornado will strike, but people recognize when the weather is likely to cause a tornado, which is a tornado watch.  Sirens go off, and people should find a safe place to be, away from windows and as low as possible (and indoors).  A tornado warning is when tornadoes have been seen in the area, so another could form at any moment.
Here is the movie we watched about tornado formation.

Shifting gears -- on to earth science!

This week, we switched over from astronomy to earth science, and before going into what earth is like today, we talked about earth's history.  When it was first formed, it had an atmosphere of helium and hydrogen, like the sun and many of the other planets.  But when something the size of Mars hit it, that atmosphere was blown off (and the moon was created by all the debris that was knocked off).  Then, gases from inside the planet started coming out (from volcanoes mostly) and made a nitrogen-rich atmosphere, which is like what Saturn's moon Triton still has.

Soon, there was life on earth, which was microscopic bacteria-like things in the oceans, and over time, a lot of oxygen was released.  Eventually, there was enough oxygen in the atmosphere for an ozone layer to form.  The sun's ultraviolet radiation hits oxygen molecules and sometimes converts them into ozone, and the thick layer of ozone that surrounds earth protects us from a lot of harmful radiation.  Only when we had this thick ozone layer could life come out of the oceans onto dry land.  Once that happened, all sorts of things happened on earth, including life changing from only microscopic bacteria-like things to a wide variety of living things like plants, animals, fungi, and more.

Thanks to that protective ozone layer, things were pretty good for a while, but then people noticed a problem.  In the 1950s and 1960s, many products were made using something called CFCs, or chloro-fluorocarbons.  These chemicals were used mainly in aerosol spray bottles to get stuff to come out quickly and in refrigerators and air conditioners.  Scientists found in the 1970s that these chemicals were quickly damaging the ozone layer by causing large holes to open up.  People found a way to monitor the thickness of the ozone layer all over the planet, and were alarmed at how large the hole sometimes got.  The biggest hole opens up over the antarctic in the springtime, and it's clear that having a hole in the ozone layer over places where people and other living things try to exist would be really BAD news!!

This picture shows how large the antarctic ozone hole gets

So people got to work worldwide to ban chlorofluorocarbons so that we would stop destroying the ozone layer.  The first international meeting about it was in March 1977, and in September 1987 the Montreal Protocol was created to specify what chemicals needed to be eliminated and how quickly the world would try to accomplish this.  People agreed to work together to make sure we stop destroying ozone and let the ozone layer re-create itself.  CFC production in the US ended in 1996 and worldwide in 2010.  Scientists forecast the antarctic ozone hole will permanently close around 2050.  A global environmental victory!!!

Next, we moved on to talking about clouds and weather.  Specifically, we talked about how clouds form.  Generally, what happens when clouds form is that warm, moist air that is on the ground rises and gets colder.  As the air gets colder, the moisture (water) that's in it begins to collect up.  Colder air doesn't hold water as well, and up high in the air, there is less pressure too.  Both of these things eventually cause the water to come out of the air and form clouds.  Dust in the air starts the whole thing, but clouds are made primarily of water that came out of warm air.  There are many different kinds of clouds, named by people for what they look like.  We'll be talking about this next.

Astronomy Wrap-Up -- Transits, Planets, and Constellations

This week, we started by reviewing the moon phases and what eclipses are.

A lunar eclipse happens when the sun, earth and moon are lined up in a way that causes the earth to block the sun's light from reaching the moon.  So, for a small amount of time, what would have been a full moon instead looks like a new moon, but then the earth's shadow moves and it's a full moon again.  A type of lunar eclipse happened just a few days ago, you can read about it here.

A solar eclipse happens when the moon happens to perfectly line up such that it blocks the suns' light from reaching the earth.  The only reason the moon, which is so tiny, can do this is because it is so close to the earth, just like when you put your thumb close in front of your eye, you can block your view of an entire person.  But if your arm is outstretched, your thumb can only block your view of a small thing.  This picture is a pretty good illustration of what happens.  Here is a site from NASA that details eclipses that have happened and are going to happen.  On November 3, we are going to experience a rare hybrid solar eclipse -- awesome!!

Next, we talked about transits.  A transit is when an object, such as a planet or a moon. crosses in the path of the sun, but the object is too small and/or too close to the sun to actually block out much of the light.  You see (if you looked at the sun, which we humans should never actually do!) a small, black circle move across the sun.  We are the third planet, so the inner two planets do transits once in a while, and here's a picture of a Venus transit from 2004.  Another one happened in 2012, and the next will not be until 2117.  So we who are alive today will never get to see one!  :(  There are Mercury transits too, but since it is so much smaller and closer to the sun, it is an even tinier black circle.

Then, we discussed the three planets in our solar system we hadn't gotten to before:  Saturn, Uranus, and Neptune.

Saturn is the planet most well known for its rings, but actually, Jupiter, Uranus and Neptune all have rings too.  It has seven rings with gaps and divisions, and the rings are thought to be pieces of comets, asteroids, or shattered moons.  A day on Saturn lasts only 10.7 hours, but a year lasts 29 Earth years.  Saturn's atmosphere is hydrogen and helium, and its core is rock, ice, water, and other compounds, with a layer of liquid metallic hydrogen around it.  Saturn has superfast winds and rising heat that make the yellow and gold bands we see on the planet.  Saturn's largest moon, Titan, is larger than Mercury and has a nitrogen atmosphere similar to what Earth's may have been long ago.

Uranus is the planet with the equator at nearly right angles to its orbit, and it rotates in the opposite direction of the other planets.  This may be explained by a past collision with an Earth-sized object.  It looks blue due to methane in its atmosphere, and one year on Neptune lasts 84 Earth years.  Seasons on Neptune last 20 years, and inside the planet is icy water, methane, and ammonia.  Uranus has 27 known moons, and they are mostly named after Shakespearean characters, unlike the moons of the other planets, which are named for Greek mythology characters.  There is a swarm of 8 small satellites that are very crowded, and it is a mystery why they haven't crashed into each other.  Neptune is nearly a twin of Uranus in size and composition.

Neptune is a slightly different shade of blue than Uranus, because of other components than methane in the atmosphere.  A day takes 16 hours, and a year takes 165 Earth years.  There are 13 moons and 6 rings, and only one mission has visited Neptune -- Voyager 2.  Its magnetic field is 27 times stronger than earth's, and it has very strong winds.  Neptune was the first planet found by mathematical calculations before it was actually observed.  Triton is its largest moon, and it is extremely cold.  Icy geysers were seen on this moon, and it is getting closer to the planet every year.  In millions of years, it might break apart and create a bright ring around Neptune.  The atmosphere is getting warmer, and we don't know why.

Constellations are groups of stars that people observe on earth and create a picture out of them.  They are actually moving very slowly across the sky, because we are on the surface of a planet that is rotating.  We can't see the same constellations as people at a different latitude because of what direction into outer space we are facing.  The constellations that cross the same line as where the planets in our solar system are make up the zodiac.  There are twelve zodiac constellations, and a total of 88  constellations that people have defined (created).  The twelve zodiac signs are the horoscope signs, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.  The constellation for your sign is high in the sky at noon during the month of your birth, and people have observed them for centuries.

The Phases of the Moon

We spent the class learning about the phases of the moon.  We started by using a flashlight (for the sun's light), a large rubber ball (for the earth) and a small, white, plastic ball (for the moon) to illustrate exactly why the moon goes through its phases.

As the moon goes around the earth, the part of the moon that the sun lights up appears to change in size.  Actually, it's the part that we can see from earth, since there is always half of the moon illuminated by the sun.  The phases are:

1.  New moon, when we can't see any of the lit part of the moon.
2.  Crescent moon, when we see a sliver of the moon.  Waxing crescent means the part we see will get bigger.
3.  1st quarter, or half moon, when we see half of the moon.
4.  Gibbous, when we see more than half of the moon.  Waxing gibbous means it's still getting bigger.
5.  Full moon, when we see the entire lit side of the moon.
6.  Waning gibbous, when we see more than half the moon, but waning means it's getting smaller.
7.  3rd quarter, another half moon.
8.  Waning crescent, when we see a sliver of the moon, but waning means it's getting smaller.

We watched these two movies to illustrate the concepts:

Then we did an art project about the moon phases, cutting and gluing moon shapes onto our night sky paper.
One last thing we talked about was eclipses:
A lunar eclipse is when the earth perfectly blocks the sun's light from hitting the moon.  A solar eclipse is when the moon perfectly blocks the earth's view of the sun.  Both are somewhat rare because the moon's orbit around the earth is at a different angle than the angle of the earth orbiting the sun.  Only 5 degrees, but because the sun is so large, it's enough to result in eclipses being very uncommon.

A blue moon is when there are two full moons in one month.  It is not very common either.