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So I just bought a globe for my extremely inquisitive soon to be 4-year old son. He knows the very basics of the solar system and knows that we live on planet Earth and also knows the concept of gravity.

While i was explaining to him what the illuminated equator line is he asked me How do people stand below this line? (Look at the globe from a 4 year old's eyes and you will wonder the same)

I explained to him that earth is not as small of a sphere as this globe depicts and almost everywhere it will be relatively flat but then he said there are so many places on this globe at the bottom if you live there earth will be above you and gravity will hold you upside down.

How do I explain it to him?

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    $\begingroup$ Hi, Hanky's son. I'm in Australia, so I'm upside down compared to you. But the Earth still feels like it's below me. $\endgroup$ – PM 2Ring Jan 8 '18 at 2:38
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    $\begingroup$ They're not???? $\endgroup$ – Carl Witthoft Jan 8 '18 at 18:21
  • $\begingroup$ buy them an inflating globe perhaps? $\endgroup$ – George Jan 9 '18 at 13:58
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    $\begingroup$ Everyone knows the Earth is flat and gravity is a hoax ;) $\endgroup$ – barrycarter Jan 9 '18 at 15:34
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    $\begingroup$ They are tilted relative to you. So, I would say your kid has a good sense of relativity. He would be a great astrophysicist in the future. Keep on the good work! $\endgroup$ – Kornpob Bhirombhakdi Dec 22 '18 at 14:34
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Explain that "down" is more or less toward the center of the Earth, and that direction changes with location. (For a four year old, skip the "more or less" part. It's just toward the center of the Earth, period.) The direction of "down" doesn't change much on trips across town, but it does change with larger trips.

If you have taken your son on a long trip (just a few hundred miles or kilometers will do), show your son those two locations on the globe. The direction of "down" at that remote location and the direction where you live point in slightly different directions for a trip of a few hundred miles, vastly different directions for a longer trip. Ask him if he felt tilted sideways at that remote location.

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While i was explaining to him what the illuminated equator line is he asked me How do people stand below this line? (Look at the globe from a 4 year old's eyes and you will wonder the same)

The issue your son sees is that, in his mind, gravity exists around that globe and is always down, because that's what's it's like where he's standing and he expects it (correctly !) to be the same for the model globe. He has no conception of a space without gravity and cannot make the connection.

You need to explain that the Earth is in space, where the gravity is effectively zero and it's the Earth itself that pulls objects on and near it's surface to itself.

For the Earth there is is no other gravity "down", unlike the globe he's being shown.

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The Earth is a very, very big ball just like the one you play with. It's so big you can't even tell you're standing on a ball. The bigger and heavier things are, the more they pull on other things. The Earth pulls everybody standing on it toward its middle so everybody thinks that they are right side up.

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  • $\begingroup$ so everybody thinks that they are right side up. This was very helpful $\endgroup$ – Hanky Panky Jan 10 '18 at 7:29
  • $\begingroup$ Maybe wait a while before telling him that the austral view of the moon looks upside down, compared with the view from the northern hemisphere. $\endgroup$ – John Canon Dec 26 '18 at 23:19
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Sounds like you have a budding astrophysicist on your hands!

I would say this:

"Son, there's something called gravity that kind-of pulls everything to the center of Earth. It's like a magnet, but everywhere you go on Earth it's there. It's in the mountains, in the ocean, even at daycare."

Now present the magnet/paperclip example someone else suggested as a supplement to this explanation. Take the paperclip and let it attract to the magnet from the top. Now flip it over and explain that Earth's gravity works in a similar way.

No need to get technical. I'm sure your future astrophysicist will discern the semantics of this concept at a later date.

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    $\begingroup$ My pleasure! What was I doing at age 4? Hmm... trying to catch ghosts with my proton pack and ecto containment unit! @HankyPanky $\endgroup$ – Chris K Jan 10 '18 at 14:13
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I like the answer by D. H. However re-reading the question and the comment by C. W. it seems possible that yours boy got it right in a way.

Indeed, the people below equator are tilted or upside down with respect to us. This still can be explained as suggested, of course we know.

But the two situations are different.

It comes to me to realize that a sphere and Newton law are not enough to explain why somebody in Australia is not walking on its head. So the fact that we sense up and down plays a crucial role.

Unfortunately it is a mix of physiological psychological factors, I guess.

You should make sure what your son in asking, in other words.

I would say that gravity is at center of Earth. The latter being spherical, gravity is under our feet.

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I'd use a visual here - just tape some Lego people to a basketball, then explain that down is to the center of the basketball, and it only looks to him that there is a "universal down" because he too is standing on a much larger basketball. For someone that young, and for people of any age, a demonstration like that will make more sense than any explanation.

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I would show him a magnet, and the magnet can hold something upside-down. The pull is towards the Earth, just as the pull is towards the magnet. Direction (up down) doesn't really matter only where the Earth is or where the magnet is, relative to the person or paperclip.

SO the person on the "bottom" of the Earth is like the paperclip being held by the magnet above it. He's being pulled by gravity towards the center of the Earth just like everyone else on the Earth. Earth is always down - no matter where you are on the surface.

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    $\begingroup$ Hmmm. Maybe. But magnetic fields are rather different to gravitational fields, and it might be hard to communicate those differences. $\endgroup$ – PM 2Ring Jan 8 '18 at 2:43
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Show him water in outer space. The water doesn't fall down onto the floor.

Show him astronauts flying in outer space, they have no fall up and fall down.

Tell him that we would fall off if there was a bigger planet under the earth, (like a pea on a melon) otherwise we fall towards the mass of the planet. the planet also falls towards it's own center, that's why it's round.

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    $\begingroup$ a bigger planet under the earth Honestly I'm certain that would confuse a child even more (actually I don't even know how to make sense of that). Perhaps in need of a rephrasing ? $\endgroup$ – StephenG Jan 8 '18 at 2:03
  • $\begingroup$ You can draw a picture with some arrows, with one ball, all the arrows go to the center of the ball... with the fall off scenario, a pea on a melon. the arrows near the pea are mostly affected by the melon, so that inhabitants of the football fall off towards the arrows but the melon has radial arrows. $\endgroup$ – com.prehensible Jan 8 '18 at 17:25

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