What is the definition of Uphill?

[Evo]

Did I tell you about the time I was five and I was certain toliets operated on electricity? I mean, how else could they flush?

 

[Averagesupernova]

You mean they DON'T?
The above was intended as sarcasm.

 

[Cyrus]

http://home.howstuffworks.com/toilet1.htm

 

[Averagesupernova]

http://home.howstuffworks.com/toilet1.htm

Now THAT was funny cyrus.

 

[Cyrus]

I just wanted you to flush your misconceptions of rivers flowing north down the....err umm...toilet

 

[tribdog]

I remember a list of questions someone (maybe Gokul) posted once. One of the questions was about the Mississippi river flowing up hill and there being a physics reason for doing so. I don't know what the answer was though.

As far as where water flows to I've figured out that any spilled water flows to the spot where I am about to step if I'm wearing socks.

 

[DaveC426913]

If I may...

Perhaps what the OP is asking is...

Why would ANY rivers flow towards the equator, since, as we know from the shape of the Earth, the equator is higher than the poles. Any rivers that flow toward the equator will effectively be climbing uphill, right?

Here is the answer:

Consider what sea level is in these various parts of the Earth. Sea level is the lowest possible point to which water will flow. If sea level near the equator really WERE higher than at the poles - well, logically, the equatorial seas would be bone dry beaches wouldn't they?

But the fact that the Earth is an oblate spheroid also means that its gravitational pull is not distributed evenly. The net effect is that every point on the Earth's surface experiences approximately the same amount of pull. This means that the equator is NOT "downhill" from the North Pole regardless of their relative distances from the geometric centre of the Earth.

All water in the oceans (including the water that the Mississippi flows into) is at the lowest point it can go. The Mississippi flows downhill towards it.

 

[zoobyshoe]

But the fact that the Earth is an oblate spheroid also means that its gravitational pull is not distributed evenly. The net effect is that every point on the Earth's surface experiences approximately the same amount of pull.

I can't follow this. The second sentence seems to be presented as explaining a consequence of the first, but in fact, seems to contradict it. If the pull is not evenly distributed than why would you say every point experiences the same amount of pull?

 

[DaveC426913]

I can't follow this. The second sentence seems to be presented as explaining a consequence of the first, but in fact, seems to contradict it. If the pull is not evenly distributed than why would you say every point experiences the same amount of pull?

The facts that 1] the pull is not distributed spherically AND 2] that the Earth is not spherical, cancel each other out, such that any point on the Earth (at sea level) experiences the same amount of pull, and it is perpendicular to the surface.

Forget rivers for a second. Oceans are simpler. If the Caribbean Sea really *were* uphill from the Arctic ocean, the water would flow out of the Caribbean into the Arctic, leaving the Caribbean bone-dry.

The fact is, sea level EVERYWHERE on the Earth is the lowest point at which water can flow to.

Have a look at the attached pic.

 

[DaveC426913]

Wow, I'm finding this really hard to explain succinctly.

The gravitational pull at any point on the surface of a perfect sphere happens to be exactly in the direction of the centre of the sphere. The line on a plumb bob will point at the physical centre of the sphere.

No so with other objects.

The gravitational pull on the surface of an oblate spheroid is NOT always inline with the physical centre of the object. A plumb bob, if followed through the object will point to different places, depending on where you are standing.

HOWEVER, the plumb bob line will ALWAYS be tangential to the surface where you are standing. That means every point on an oblate spheroid is experienced as horizontal - no sloping effect.

 

[Averagesupernova]

Good luck Dave!