Why Is The Earth Round?

[anthony]

A typical sarcastic answer to something unknown can typically be a question like, "why is the earth round" or "if a tree falls in the forest and nobody is around, does it make a sound?" These type of sarcastic questions I love... so I went searching for the answer to one of my favourites... Why is the earth round? Which many people cannot answer.

So here is the answer from a physicist.

Why is the Earth round (planets and the sun, too)?

It's the gravity, of course.

Imagine Earth were liquid--consisting, say, only of water. Gravity would of course pull that water towards the center, and if any could flow closer to the center, it would do so.

Therefore, if such an Earth were not a sphere--if some points were higher than the average--their water would quickly flow down. Water would also flow into any valley deeper than the average and fill it up. The final shape MUST be a sphere. Only then does every point on the surface have the same distance from the center.

Gas planets like Jupiter, Saturn, Uranus and Neptune behave the same way, since gas flows like a fluid. The Sun is gas, too, so it must be spherical. But Earth? The Moon? Why should a planet composed of solid rock have the same shape as one composed of water?

Because, dear friend, once you descend a few hundred miles (or kilometers), rocks flow like a fluid, too. A rock 300 miles underground bears the weight of a 300-mile layer of rock, and under such pressure even solid material will gradually yield, more so because of the intense heat there. Hence the rocky Earth is close to a sphere.

Mountains may stick up 30000 feet, but not much more, otherwise the ground will slowly sink under their weight. Olympus Mons on Mars can reach 80000, but the weaker gravity of Mars makes it possible. Asteroids 100 miles across may still be potato-shaped (not enough gravity to give the outer layers enough weight), but by the time you reach 300 miles, round is the rule.

Round ... but not always completely round. Earth bulges a little at the equator, because rotation flings matter outwards, weakening gravity there by a fraction of 1%. Jupiter spins faster than Earth--just under 10 hours--and bulges much more: telescope pictures of Jupiter show it visibly fatter at the equator. And our Moon--why do you think it always presents the same face to the Earth? Yes, it is lightly longer in that direction, and the pull on the part sticking out towards Earth keeps it aligned that way.

 

[Nicolette]

As you can see....we have very boring lives...so much so that Anthony needs to ponder such questions :poke:It all started with a conversation...."I'm bored" and we end up Googling why the earth is round.:rolleyes:

 

[Claire]

You 2 need to get out more....!

and how do sharks know they 'aren't found in these waters'?

 

[Irton Pike]

this is all good intertesting stuff. Why would anyone find this boring?

 

[Irton Pike]

Why is the sky blue?

 

[2quilt]

Why do businesses get no customers for a while, then get a rush of customers in waves?
What do you add to powdered water to reconstitute it?
What day does Easter fall on in 2009?
Why can't you heard cats?

 

[cragger65]

Why do some peoples's feet smell like Parmasan cheese?

Sorry, couldn't resist ;P

 

[cragger65]

If I'm remembering correctly the reason the sky is blue is that the atmosphere filters out other light band frequencies (which is why life can survive here on Earth, btw). At a different angle of refraction, the red and yellow light band frequencies come through (sunrise and sunset).

 

[anthony]

Why is the sky blue?

Another goodie....

Why Is The Sky Blue?

Short Version

It is because blue light from the sun strikes the air molecules and scatters and our eyes perceive it as blue.

Long Version

Transmitted light (from the sun, light bulbs, fire, etc) is made up of a spectrum of colors. The longest wavelengths of light are on the red end of the spectrum and the shortest wavelengths are on the blue/violet end of the spectrum.

When transmitted light such as sunlight enters our atmosphere it collides with the oxygen and nitrogen atoms. The color with the shorter wavelength is scattered more by this collision. Because violet and blue are the shortest wavelengths the sky appears to be violet / blue. But because our eyes are more sensitive to blue light than they are violet light, we perceive the sky as blue.

Our eyes contain thousand of rods and cones, which are the receptors for light. Whenever one of the 3 Stooges pokes you in the eye you see a giant blue spot. This is because the blue receptors have been activated. Blue is one of the primary colors and thus more easily activated and seen by our eyes.

 

[Robyn]

My personal favorites:

Which came first, the chicken or the egg? People can debate that one for hours on end!

How much wood could a woodchuck chuck if a woodchuck could chuck wood?

Hugz!
Robyn

 

[Seeking_Nirvana]

That is interesting because those questions always posed to be riddles instead of sarcasm to me. I guess we all perceive things differently.

That story reminds me of an allegory. Maybe it's just me, but I see a lot of metaphors in it. I have to wonder what that story is 'really' about, and how the frustration (solid material yields due to heated rocks) or the need to vent is causing PTSD symptoms to flair up.

Maybe you knew the answer to this question, but your subconscious mind felt the need to expose it here to entertain us?

Thanks for that little epic. I never ventured to find out why the world is round.
Tammy

 

[Irton Pike]

Why don't we fall through the floor?