木曜日は、マリーのはてな日記/Marie the Scientist
Why is Venus hotter than Mercury?」
Why is Venus hotter than Mercury?
Today at school, I learned about the 8 planets that go around the sun.
Mercury is closest to the sun.
Then Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
My teacher, Ms.Sato, told us about them.
“Earth’s average temperature on land under the sea is 15 degrees celsius.
The temperature of planets closer to the sun is much higher.
The planet closest to the sun, Mercury, is about 170 degrees.
Venus, the second planet, is about 460 degrees.”
“Wow, that’s hot.”
“We are lucky we live on Earth, aren’t we?
And I hear the chyme.
See you all next time.”
The class was really interesting.
But I had a question for my teacher.
“Ms. Sato, you said Mercury is 170 degrees and Venus is 460 degrees.
Why is Venus hotter than Mercury?”
“Good question, Marie.
Mercury is closer to the sun than Venus.
So you may imagine Mercury is hotter.
The key is their atmospheres.”
“What is an atmosphere?”
“It’s the air around the planet.
If there is an atmosphere, the planet will be able to keep the heat from the sun.
The atmosphere of Venus is really thick so the heat from the sun doesn’t escape from the planet easily.
On the other hand, Mercury doesn’t have an atmosphere so sunlight hits Mercury during the day and makes it really hot.
But when the sunlight is gone the temperature drops quickly.
Mercury can get us cold as -180 degrees.”
So Mercury is a planet without any clothes.”
Also, 96.5% of Venus’ atmosphere is carbon dioxide or CO2.
If there is lots of CO2 in the atmosphere, a planet keeps the heat better.”
“So, Venus is wearing a very thick coat.
That’s why it gets so hot.”
“That’s the right image.
Earth also has an atmosphere.
But it’s only about 0.04% CO2.
So heat can get away easily.
Our atmosphere keeps earth from getting too hot or too cold for humans.
Marie, do you know about global warming?”
“Earth is becoming hotter, right?”
“Yes, there is more and more CO2 in Earth’s atmosphere now.
There are several reasons such as burning coal to make electricity or using gasoline-powered cars.
If we continue to add CO2 to our atmosphere, Earth will get hotter and hotter.”
“Then, what will happen?
“Well, ice from North Pole and South Pole will melt and become water.
More water in oceans means less land for us to live on.
And there will be many more serious changes.”
“So, when I see Venus in the night sky, I always think about being good to our earth.”
“I’ll think about it, too.”
How can I make less CO2 go into the air?
Oh, I know.
I will tell Dad to buy an electric car.