system
Given the following post, respond as if you're commenting on Reddit:
human
Questions from a grade 3/4 class!

i have used ELI5 explanations to share simplistic answers to complex questions with my class in the past.  They were excited to hear that there is a place they can ask "Big Questions" and get straight forward answers.  I created a box for them to submit their questions in and told them I would make a post. I am sure many have previously been answered on the site but I am posting the list in its entirety. 

**EDIT:  Thanks so much for all the answers!  I didn't expect so many people to try to answer every question.  The kids will be ecstatic to see these responses.  I will try to limit the number of the questions in the future.**


Below are all the questions they asked, some are substantially easier to answer than others.  

1) Why do we age?

2) What do people see or feel when they die?

3) Why are there girls and boys?

4) How do you make metal?

5) Why do we have different skin hair and eye colour?

6) Why do we need food and water?

7) How do your eyes and body move?

8) Why do we sleep?

9) Why don’t dinosaurs live anymore?

10) How are dreams made?  How do you sleep for so long?

11) How did animals come?

12) Who made up coffee?

13) Did we come from monkeys?

14) How does water have nothing in it?

15) Who made up art?

16) Why do we have eyebrows?

17) How do you make erasers?

18) How big is the universe?

19) Who made up languages for Canada?

20) Why is a doughnut called a doughnut if there’s no nuts in it?

21) Why did the dinosaurs come before people?

22) Why is the universe black?

23) Why do we wear clothes?

24) Why would the sun keep on fire if there is no air?

25) How long until the sun goes supernova?

26) How did Earth get water on it if it came from a fireball?

27) How was the Earth made?

28) Why are there different countries?
gpt
I'll take this one:

>Why would the sun keep on fire if there is no air?

For a long time, people though the sun was just a big ball of fire in the sky. And it's true that the sun is very hot; hot enough to burn almost anything. But actually, the sun doesn't shine because it's on fire. If it did, it would have gone out already, because even the sun isn't big enough to burn for that long. Instead, the sun shines for the same reason that nuclear bombs explode.

What happens in the sun and in nuclear bombs (some of them, anyway) is that it squeezes atoms together. In the sun, the squeezing is from gravity; in nuclear bombs the squeezing is from normal bombs that go off in a circle around the nuclear bomb. Anyway, it squeezes the atoms together enough that they get smashed into a single atom, like if you push two balls of play-dough together. Now, it takes energy to hold something together: like if you had two dogs on leashes it would be hard to keep them from running away from each other, right? Well, it turns out that for some type of atoms (like hydrogen getting smashed into helium) it takes less energy to keep the new big atom together than it did to hold the two old atoms together. So the extra energy comes out of the smashed atom, and one of the ways it comes out is by light. And the light shines out into space and that's why the sun shines. In nuclear bombs the extra energy comes out as an explosion (and also light). Just like a nuclear bomb is bigger than a campfire, there's a lot more energy made from smashing atoms than if the sun was just a big fire, so the sun will keep shining for a very long time.

Bonus:

> How long until the sun goes supernova?

The sun will probably never go supernova, because only really big stars go supernova, and scientists think the sun isn't big enough. However, in about 5 billion years it will turn into a huge red star and swallow the Earth. And then a few billion years later it will turn into a small, cool star and gradually fade out.