Why Do Trees Lose Leaves in the Winter?

Super question, Mikey!  I know everyone has seen it.  Leaves on trees turn yellow, orange, red or brown and then they fall off in fall or winter.  Let’s find out why!

In the spring and summer, leaves are very busy.  They will take in sunlight and turn it into energy (en – er – jee) so the plant can grow.  Leaves use chlorophyll (klor – a – fill) to do this, and chlorophyll is green.  All spring and summer, the leaves are green because there is a lot of strong sunlight.  The leaves make a lot of chlorophyll.  People have made something that can turn sunlight into energy.  They are called solar panels.

solar panels suns energy

After summer is over, the sunlight is weaker and the day’s become shorter.  There is less sunlight for the leaves, so they make less chlorophyll.  The green goes away, and now we can see the other colors that are in the leaves.  Did you know the yellow, orange, red, and brown are always in the leaves?  It’s just covered by the green chlorophyll!  But why do the leaves need to fall off?

poor chlorophyll

Let’s take a look at the 3 main reasons:

  1. Losing leaves in the winter helps trees save water.  Trees that don’t lose their leaves lose a lot of water in the winter, because it is usually pretty dry.  These trees are called evergreens.  Evergreens have different reasons for keeping their leaves.  Trees that lose their leaves are called deciduous. (de – sid – joo – us)
  2. Deciduous trees can grow new leaves in the spring.  In the winter, deciduous trees have no leaves.  They don’t need to protect the leaves, or heal the leaves if something bad happens to the tree.  New leaves will come back in the spring anyway.
  3. Deciduous trees don’t need to worry about animals.  Animals (insects too!) still need to find food to eat in the winter.  Many times, they will eat evergreen plants because they are more healthy and easier to find.

deciduous trees are babies


Why is the Earth Green and Blue?

Here we go! It’s time for Serious Question #11!  This one comes from Lucy.  Some people call her Lucy 7 or Juicy Lucy.   Right now, it doesn’t matter, because all I know is that she gave me a great question!

I’m going to answer this question about looking at the Earth from space.  So… let’s start with this great picture of the Earth from space.  How many colors can you see?

how many colors on earth

1 Blue – That’s the water.  Water covers most of the Earth.  Really, 70.8% of the whole Earth is covered in water.  After that, almost all of that water is salt water, so we can’t drink it.  97.5% of all that water is undrinkable.

2 Green – That’s the plants.  Trees, grass, flowers, vegetable plants, and fruit trees are all green.  That’s because plants have something special called chlorophyll (klor – a – fill). Chlorophyll is why plants are green and it helps plants take sunlight and turn it into energy(en – er – jee)

. 3 Light Blue – Maybe it’s hard to see, but that’s also water.  Is that cheating?  But this is different, because it’s light blue!  It looks light blue because that water is shallow.  Shallow is the opposite of deep.  The sand under that water is very close to the top, so it looks light blue.

4 & 7 White – I count white twice, because it comes from different things.  One is clouds.  You can see clouds cover A LOT of the Earth, all the time.  The other is snow and ice.  You can find snow and ice at the tops of some mountains (like #7) and also at the North Pole and South Pole.

5 Brown – There is a lot of brown on mountains that don’t have snow.  Some areas are very dry but they are not deserts.  They can look brown too, because of the dirt and maybe dead plants.

6 Yellow (or light brown) – This is the desert.  Some of the deserts look yellow, and some look tan (tan = light brown).  Deserts that look yellow are covered in sand.  They are very dry and usually don’t have many plants or animals.

8 Gray – Think about clouds again.  Are they all white?  Are they white all the time?  Nope.  Sometimes clouds can be very dark and gray when it is raining or there is a storm.

earth at night colors

9 Dark Blue or Black – The water at night! Is this cheating again?  Sorry…

10 Yellow – From space, we can see a lot of big cities.  It is very easy to see these places at night because of the lights that are turned on all the time.

So I can count 10 colors on the Earth from space.  How many can you find?  Why is it that color?

How Did People Make Books?

Serious Question #12 comes from George! He always asks such good questions, but I finally got around to writing about one of them.  Thanks, George!  Let’s get down to books!

A long time ago, people needed a way to write down their ideas.  They also needed a way to send those ideas to other people.  Before people started making books, they would write things down on stones, wood, bone, bamboo, animal skins and tree bark. Bark is the brown, outside part of a tree.  4500 years ago, people in Egypt (ee – jipt) made something new and better to write on.  They invented papyrus (puh – pie – rus).   Papyrus is made from a plant, and it looks a lot like paper, but it is not as thin as paper.

papyrus plant

2500 years ago, Cai Lun started making paper in China.  Paper was thinner than papyrus, so more papers could be put together in one place.  Cai Lun did not make books yet, though.  The next step to books was 2300 years ago in India.  People in India started putting things together, and then putting hard boards on the front and back to protect the pages.  Today, we call those boards the cover of the book.

gute block letters

The last step to books like today was the from Germany.  About 500 years ago, a man named Gutenberg (goo – tin  -berg) made a machine that could make a lot of books very quickly.  The machine was called the printing press.  Before the printing press, people had to write each book by hand.  This took an extremely long time!  Writers could only write a few pages every day. So the printing press helped people make books more quickly.  The printing press could print 3,600 pages every day!  It used small letters on blocks.  The letters would be dipped into black ink, and then pressed onto white paper.  Add a cover, and you have a book!


read some books

Why is Mars Red?

A long time ago, Tom asked me this question.  I gave Tom an answer in class, but now I’m getting around to writing about it.  Remember, when people talk about space, planets, and stars, we need to use a lot of guesses.  Let’s go get red!

Mars is a planet in our solar system.  There are 8 planets going around the sun and Mars is the fourth one, right after Earth.  The core of our planet, Earth, is made of a metal called iron (I – ern).  Core means the ball in the very middle of a planet.  Sometimes, this metal is found on top of the Earth too.  Many things like bicycles, cars, buildings, and ships are made of iron.  Just like Earth, Mars has a core made of iron too.

robots learn mars

When iron touches oxygen (ox – ijen), it starts to change.  It turns into a thing called iron oxide. (ock – side)  The easy, normal name we use for iron oxide is rust.  There is oxygen in the air and water.  After iron starts to rust, it will change from dark gray to red or orange.  So now we know that Mars looks red because it is covered in rust.  But why is there so much rust on Mars?

alittle rusty bike

The rust on Mars is actually just a very thin layer on top.  In most places, the rust is only about 1 cm thick.  The wind on Mars blows this rust dust around the whole planet.  Volcanoes on Mars are much bigger than volcanoes on Earth.  Some astronomers think that these huge volcanoes pulled a lot of iron from the core and blow it out onto the top of Mars.  Then, the iron changed into rust to give Mars the red color.  Some astronomers think Mars had water on it a long time ago, and maybe air, so the iron changed to rust with the oxygen in the water or air.

rust here Mars


Why did America Have a Civil War?

Great question, Jay!  A long, long time ago, I was in a class that was all about this question.  Today, I’ll try and share two main reasons for the Civil War.

pick cotton

A Civil War is when two parts of the same country fight against each other.  In America in 1861, the South started fighting with the North.  The South had a lot of big farms called plantations (plan – tay – shun).  They grew a lot of cotton on these plantations.  Cotton is white, and people make clothes with it.  The problem with cotton, is that it takes a lot of people to grow it and pick it.  Too many people.  So farmers in the South had slaves.  Slaves are people that work for somebody for no money, but they don’t want to.  Most of the slaves were from Africa.

CW map north south

The South said they needed slaves to work on the plantations, and the North thought that having slaves was wrong.  The people who had plantations and slaves were called masters.  The masters in the South thought the North would try to free the slaves.  Free the slaves means to let them go away from the plantations.  Then, the South started the Civil War.  11 states left the United States of America (USA) and started the Confederate States of America (CSA).  A whole new country!

not slave not master lincoln quote

After 4 years of fighting, it was the North that was the winner of the Civil War.  The South was part of the USA again.  Abraham Lincoln was the president (He’s on the penny!) and he ended slavery. (slay – ver – ee)  But remember, I said there were two reasons!  The first one, the North thought that people like slaves should be free.  And two, the South thought each state should be free to make their own rules.


  • The North wanted people like slaves to be free.
  • The South thought that the USA can’t tell each state what to do.
  • The South left the USA and started the CSA.
  • The North won the war, and brought the South back to the USA.
  • The end.

How Hot is Lava? Hotter than the Sun?

Hey Little Nerds! Welcome back for Serious Question #8.  I heard a great question from Ethan on Friday night, so here we go!  Ethan asked, “How hot is lava? Is it hotter than the sun?”

lava not tomato juice

First, let’s talk about lava.  When ice melts, it becomes water.  When rocks melt, they become magma.  When magma comes out of the Earth, it gets called lava.  Melted rocks are very, very hot.  Of course!  But how hot is lava?  Lava can be up to 1200° C.  That’s… really, really hot.  Let’s take a look at some numbers:

  • Water freezes at C.
  • Your body is around 37° C.
  • A wood fire is about 260° C.
  • Lava is 1200° C. WOW!

How does lava get that hot?  In the middle of the Earth, melted rocks are called magma. After magma comes out of the Earth, then it is called lava The inside of the Earth is made of 3 main parts.  The core is the middle of the Earth.  After the core is the mantle.  We live on the crust.  That’s the outside part of the Earth.  Magma is in the bottom of the mantle, and pushes up to the top of the mantle.

earth layers

But let’s get back to Ethan’s second question.  Is lava hotter than the sun?  If you look back, you will see lava is 1200° C.  I know that I said that is really, really hot… but the sun is much, much hotter.

  • If you could stand on the sun, it would be 5500° C.
  • Outside of the sun, it’s even hotter.  2,000,000° C. (this part is called the corona)
  • The middle of the sun is CRAZY hot.  15,000,000° C.

Fifteen Million Degrees.

So, Ethan.  Lava is hot, but… no.  Lava is not hotter than the sun.

you win said the lava

Why Are There So Many Stars?

I got another good one from Jenny!  She asked, “Why are there so many stars?”  My answer is coming very quickly this time: I don’t know!  So I’m going to try and answer a different question instead:  How many stars are out there?  Most of the numbers in this answer are guesses.  It’s pretty close to Jenny’s question, so let’s see how it goes!

We are going to start very close to home this time, and get bigger and bigger.  First, your house.  It’s probably pretty big! But, what about Hangzhou?  That’s a lot bigger than your house.  Then, China.  Again, that’s a whole lot bigger.  Then Asia.  Then the Earth.  Then the Solar System (so-ler sis-tem).  The Solar System is our sun and the 8 planets around it.  Earth is just one of those planets.  So that’s extremely big, right?

usa from space moms house

Wrong.  It’s still a tiny, tiny part.  Outside of our Solar System, we are part of a galaxy (gal-ax-ee).  The name of our galaxy is Milky Way.  After that, our galaxy is part of the universe (you-ni-vers).  The universe is everything that we know about.  EVERYTHING.  Some astronomers (ass-tron-a-mer) think that there is still more after the universe, but we just don’t know about it and can’t see it yet.  Astronomers are people who study space.

milky way

Now let’s get to the numbers! I bet you know how many stars are in our Solar System, right?  Yep, one.  The sun is a star.  In just our galaxy, the Milky Way, some astronomers guess that there are 100,000,000,000  stars.  100 billion.  Insane.  And other astronomers think there are more.  But we aren’t finished yet.  The Milky Way has a crazy number of stars, but there are also a crazy number of other galaxies in the universe.

Wow.  Those astronomers really like big numbers.  They think there are maybe 10,000,000,000,000 galaxies out there.  Ten trillion galaxies.  So if we put these two silly numbers together… we get a guess of about…

100,000,000,000,000,000,000,000,000,000 stars

…in our universe.  I didn’t even know how to say that number, but I looked it up. It’s 100 octillion.  How many can you count?  Good luck!

count stars give up