The Riddles Thread

[GoodSarmatian]

Incorrect.

I hadn't heard that answer ever before, but I don't thinks it's correct in any case. Since gravitational attraction follows the inverse square relation to distance, the moon would weigh more the closer it was to earth.

The idea was that on the moon, the moon's gravitational field is strongest but since the moon is far away from the earth, earth's gravity doesn't effect it as much. But because earth's gravity still has some effect on the moon the moon qualifies as 'on earth'.

 

[peter grimes]

@ Peter. A helium balloon.

Correct, Sir!

 

[Mise]

Incorrect.

I hadn't heard that answer ever before, but I don't thinks it's correct in any case. Since gravitational attraction follows the inverse square relation to distance, the moon would weigh more the closer it was to earth.

The weighing scale? EDIT: Dammit!

 

[classical_hero]

Don't forget that weight doesn't equal mass. While in colloquial usage they are the same, but it is highly scientifically inaccurate.

 

[Phrossack]

A BEET!

An onion, actually. Close enough.

The translated original, from the 10th-century Book of Exeter written in Old English:

"I am a wondrous creature: to women a thing of joyful expectation, to close-lying companions serviceable. I harm no city-dweller excepting my slayer alone. My stem is erect and tall—I stand up in bed—and whiskery somewhere down below. Sometimes a countryman's quite comely daughter will venture, bumptious girl, to get a grip on me. She assaults my red self and seizes my head and clenches me in a cramped place. She will soon feel the effect of her encounter with me, this curl-locked woman who squeezes me. Her eye will be wet."

 

[onejayhawk]

Correct, Sir!

Any balloon or anything else, so long as the buoyancy in air is sufficient. The classic illustration is a feather, though that is problematic.

No one tried mine.

J

 

[Kaitzilla]

Right, so maybe this is better suited for H&J, or the Forum Games, or something, but those places are dead compared to OT, and OT needs more fun threads anyway.

Rules: Write your own riddle. Or copy one down, but if it's easily Googled, then there's no challenge. Everyone else tries to guess the answer. Whoever gets it right gets to pose the next riddle.

I wrote one of my own, but it's pretty obvious, so I think I'll go with an old classic, the words modified a bit so it isn't as easy to Google. Wait for others to guess if you are already familiar with the riddle and its answer.


"I am a wonderful thing; many love to have me inside. I stand tall, erect in bed, and am hairy below. Sometimes a fine woman grabs me by my reddish head and gets to work on me. Part of her body becomes wet. What am I?"

Tomato plant in the window

 

[Kaitzilla]

Incorrect.

I hadn't heard that answer ever before, but I don't thinks it's correct in any case. Since gravitational attraction follows the inverse square relation to distance, the moon would weigh more the closer it was to earth.

That inverse square law always bugged me.

Gravity at the center of Earth is 0 if you think about it.
Yet it is 9.81m/s^2 on the surface, and a bit weaker on top of Mt. Everest.

So at what depth is gravity strongest on earth?

 

[classical_hero]

Any balloon or anything else, so long as the buoyancy in air is sufficient. The classic illustration is a feather, though that is problematic.

No one tried mine.

J

It needs to be something that is lighter than air on earth, since the Moon has no atmosphere and thus not air to be lighter than.

 

[Borachio]

What is the difference between a pickpocket and a peeping tom?

J

You can pick a pocket but you can't pick a tom?

No. That's not it. That doesn't make any sense.

What's the answer?

Is it one of those where if I say "I don't know" you say "Well, I won't ever send you to buy a packet of cigarettes, then"?

 

[hobbsyoyo]

That inverse square law always bugged me.

Gravity at the center of Earth is 0 if you think about it.
Yet it is 9.81m/s^2 on the surface, and a bit weaker on top of Mt. Everest.

So at what depth is gravity strongest on earth?

The Earth isn't a perfect sphere so the gravity wouldn't be zero at the center. Even if it were a perfect sphere, you would essentially have to be a point mass at the very center to experience zero gravity. Anything else than a point mass would have differential forces acting on it, i.e. not zero gravity.

The idea was that on the moon, the moon's gravitational field is strongest but since the moon is far away from the earth, earth's gravity doesn't effect it as much. But because earth's gravity still has some effect on the moon the moon qualifies as 'on earth'.

No, I don't really think it qualifies as 'on earth'. The best you can say is that it's part of the Earth-Moon system which does have a gravitational barycenter within the Earth.

Fun fact, the barycenter of the Pluto-Charon system is outside either body:

Link to video.
It's hard to tell but you can see that Pluto and Charon both orbit a point outside of either body.

 

[Borachio]

But hang on, there's nowhere in the Universe which isn't subject to gravity. I thought that was how it worked: rather mysteriously, acting with "infinite" range.

 

[hobbsyoyo]

True story

 

[Perfection]

@ Peter. A helium balloon.

Unfortunately it would pop

It needs to be something that is lighter than air on earth, since the Moon has no atmosphere and thus not air to be lighter than.

Technically it can be up to 19% denser than air.

 

[Steph]

I made a very nice historical riddle some years ago, but if I post it again you could just use the search function on this forum, and you'd find the answer...

 

[Phrossack]

I made a very nice historical riddle some years ago, but if I post it again you could just use the search function on this forum, and you'd find the answer...

Modify the wording a little.

 

[Steph]

Any balloon or anything else, so long as the buoyancy in air is sufficient. The classic illustration is a feather, though that is problematic.
J

What? Weight is the product of the mass and the local gravity.
The mass of the balloon is the same on Earth or on the Moon.
The local gravity is lower on the Moon.
So the weight is also lower. buoyancy in air is irrelevent.

This answer works only if you are speaking about apparent weight, not the standard definition of weight

 

[Perfection]

That inverse square law always bugged me.

Gravity at the center of Earth is 0 if you think about it.
Yet it is 9.81m/s^2 on the surface, and a bit weaker on top of Mt. Everest.

So at what depth is gravity strongest on earth?

The inverse square law applies to point sources. An imaginary small dot of infinite density.

Planets aren't that way, the part of a planet closer to you pulls harder per unit weight then parts farther away. However by quirk of mathematics any spherically symmetrical object will follow the inverse square law outside it's surface.

But what about inside the Earth?

There's another quirk that helps.

Imagine you're in the center of a planet sized hollow sphere. Gravity from all the parts of the surface pulls on you equally so you experience no net force. What happens if you move closer the surface? You'll experience stronger gravity from the area of the surface ahead of you but a larger percentage of the planet's mass is behind you. So which part wins? The answer is, it still cancels! You will experience no gravity no matter where you are within the sphere.

So for an arbitrary point inside a spherically symmetrical object the gravity of anything above it cancels and the gravity of anything below it follows the inverse square law. So as you descend you have a tradeoff of canceled gravity from the stuff above you versus increasing gravity from the stuff below.

On Earth the depth where that tradeoff is maximized is at the discontuity where there happens to be very little mass above you and a lot of mass Below. That discontuity is the boundary between the lithosphere and the troposphere. Which is better known as the surface.

 

[Perfection]

What weighs more on the moon than it does on earth?

Suitable attire.

 

[Steph]

No gravity anywhere inside the Sphere? It seems you don't really know what you are talking about...
There is gravity inside Earth. This is very easy to prove.

Go in a deep mine. Jump. Are you floating in the air, or getting back down to the ground?