What is the definition of Uphill?

Averagesupernova

Every now and then I will ask someone why it is that water flows towards the equator. Usually they say: "Because it is downhill." Then I go on to explain to them that the earth is bigger around at the equator, like slightly flattened out from an imaginary pressure on each pole. So technically it would be UPHILL since it is farther to center of the earth at the equator than any other point on the planet. Now I don't really know if this is how 'uphill' is defined. Anyway, no one can ever answer why water goes towards the equator. I guess my reason is that centifugal (yeah I know, there's really no such thing ) force from the rotating planet causes the water to go towards the equator. Actually I'd say it also causes the earth to be bigger around the middle too. So anyway, I pulled this on my nephew one time and we got into a discussion about how you actually define "UPHILL".
.
www.dictionary.com defines it as:
.
Adjective
1. Located on high or higher ground: an uphill mine entrance.
2. Going up a hill or slope: an uphill climb.
3. Marked by difficulty or strong resistance; laborious: an uphill election campaign against a popular incumbent.
.
#2 is TOTALLY lame because you can't use the word to define the word.
.
Adverb
1. To or toward higher ground; up a slope.
2. Against adversity; with difficulty: struggling uphill to make ends meet.
.
Noun
An upward slope or incline.
.
And then this:
adj 1: sloping upward [syn: acclivitous, rising] 2: hard to overcome or surmount; "a stiff hike"; "a stiff exam"; "an uphill battle against a popular incumbant" [syn: stiff] n : the upward slope of a hill adv 1: against difficulties; "she was talking uphill" 2: upward on a hill or incline; "this street lay uphill"
.
So anyway, I guess "UP" has to be defined first right? Sooooooo, I went to the same site and looked up "UP". Guess what?
.
Adverb
1. In or to a higher position: looking up.
2. In a direction opposite to the center of the earth or a comparable gravitational center: up from the lunar surface.
.
#2 defines it as I defined it earlier in this post. So, water does indeed flow up hill to the equator. Gravitational center was not on the dictionary site. Not sure how that is to be defined, but in the case of our planet, I would think it would be the same point as the geographic center.
.
I know this thread probably seems pointless, but there are so many in GD these days.
.
Comments welcome!

russ_watters

Water doesn't necessarily flow toward the Equator. The Nile, for example, flows directly away from it.

Also, most coordinate systems use sea level as their reference for height.

zoobyshoe

My first reaction is to question whether it's true or not that rivers flow toward the equator. I grew up in a town in NH that was cut through by a North flowing river.

chroot

Uphill: Any direction in which the gradient of the gravitational potential is positive.

- Warren

Cyrus

They don't, your statement is incorrect. The current goes clockwise in the northern hemisphere, and counter clockwise in the southern hemisphere. The temperature of the water (thus changing the density) is generally warmer at the equator than at the poles, which helps to contribute to the swrilling motion of the currents. The coriolis effect plays a role here too.

Other than that, the water flows from higher to lower gravitational potential energy, while taking the path of least resistance. If the path is relatively flat, it takes on what is known as a meandering path, or oxbow lake, basically a series of s' like a snake would make. The water deposits its load on the inside of the curve, because the water has a slower velocity. Therefore, the load carried by the water settles to the bottom, meanwhile the water on the outside of the curve travels the fastest, and causes more errosion on the outside bank.

Your too focused on nomenclature, and not on whats actually physically happening.

Averagesupernova

Chroot, this is the answer I was looking for. Zooby and Russ, I realize that water doesn't ALWAYS flow towards the equator. But on the average most of the rivers and streams flow towards the equator.

Cyrus, I'm not really sure what you are trying to get at. At first you say my statement of saying that water flowing towards the equator is incorrect. Then you say that water flows from higher gravitational potential energy to lower. Well, for the majority of rivers and streams this is towards the equator. As far as being too focused on nomenclature? If you hadn't noticed, that is what the thread is all about. I know what is actually physically happening. I'm not stupid.

But think about this: How different would our world be if the axis of the earth were tilted so that one pole pointed directly at the sun? There is at least one planet in the solar system that is like this, but I think it is waterless. The cycle water makes in nature as we know it would probably be very much modified.

Cyrus

I see what your saying now, about the equator being further from the center of the earth than at the poles, due to bulging. If the equator is higher than the poles, we should see the water current flow toward the north and South Pole. But I believe the dominating driving force here is coriolis and differential density due to heating. Which is why you get a swirling motion, and not a direct linear flow of water. But none the less, water does not flow towards the equator.

Well, then that pole would melt. One pole is all ice, the other is all permafrost, or permanently frozen ground. Irrespective of which pole you put at the sun, it would melt. The result would be a rise in water levels globally. But your still spinning the earth about the same axis, which means the coriolis effect would not change, and the water would tend to want to still turn clockwise in the northern hemisphere, and counter clockwise in the southern hemisphere. The difference is that now you have always WARM water at the pole facing the sun, and always COLD water at the pole never facing the sun. In fact, all water BELOW the southern hemisphere would always be COLD, because it NEVER saw any direct sunlight. In the southern hemisphere, Coriolis force would dominate the almost entirely cold body of water. In the northern hemisphere, there would be a net flux of warm water moving down towards the equator, as opposed to what we have now, which is a net flux UP from the equator. (But the direction of water movement, i.e. clockwise, would remain the same.)

matthyaouw

Would you like to back this up?

BobG

I don't think your assumption about water flowing towards the equator is valid (at least, if more water does happen to flow towards the equator, I don't think the difference would be enough to be significant).

However, the equator is not necessarily uphill. As chroot said, a positive gravity gradient defines "uphill". That depends on the direction of the force of gravity. As a simple model, people tend to treat the Earth as a perfect sphere, which would result in the force of gravity always pointing towards the center of the Earth. In reality, if there is more mass towards the equator than towards the poles, the force of gravity would not point directly at the center of the Earth. In fact, if the Earth were at least a smooth oblate spheroid, the only locations where the force of gravity would point directly at the center of the Earth would be at the poles and on the equator.

In reality, the Earth's mass distribution doesn't even match a smooth oblate spheroid. You need a more detailed model of the Earth's gravity to determine the exact direction of the force of gravity for any given location.

Geodesy for the Layman

Earth Gravitation Model 1996

One oddity in using WGS-84 as your Earth model is that the highest point on Diego Garcia, an island in the Indian Ocean, is around 50 meters below sea level.

Evo

Water doesn't always flow toward the equator. Period. Rivers will flow from their source to an outlet usually at a lower overall elevation, such as the ocean,a bay, another river, lake, etc...

Globally within the ocean, deep colder water will flow toward the equator, while warm water flows away from the equator.

Here are some links, I'll add or replace if find better ones.

http://earth.usc.edu/~stott/Catalina/Oceans.html

http://www.gomoos.org/datatypes/CURRENTS.html

http://ga.water.usgs.gov/edu/earthrivers.html

Averagesupernova

http://www.worldatlas.com/aatlas/infopage/riversno.htm

http://experts.about.com/q/2135/760283.htm

Evo

Yes that is a list of rivers that run north, away from the equator.

Averagesupernova

I really don't think the argument is that all rivers flow towards the equator. It never has been.

Evo

Perhaps you should re-state your question. You might want to check the sources I referenced about global water movemement.

Cyrus

Now im confused, because your first statement was

Could you restate your question please?

Averagesupernova

Obviously not ALL water flows towards the equator. I didn't think people on this board would take things so literally. I'm referring to streams and rivers. And those mainly in the northern hemisphere because that is what I'm most familiar with. I don't see how coriolis can effect rivers,at least the majority. It is quite obvious to me how ocean currents are formed by coriolis. That is not what is in question.
.
My point still is with what 'uphill' is. The only one who seems to be able to grasp it is chroot, and I totally agree with him. I don't think nor have I EVER thought that water actually will flow uphill by chroots definition. This: was intended as sarcasm. But it seems to be that when most people think of uphill they think of moving farther away from the center of the earth. Most people cannot answer when I ask why most rivers flow south in the northern hemisphere and point out that the earth is 'fatter around the middle'. They understand fully what I'm talking about but have no answer. So can we put the stuff previous to this thread to rest so we can argue about what I've said in THIS thread?

Evo

You didn't bother reading my link did you? Why do I try?

1. Surface Circulation

Solar heating causes water to expand. Near the equator the water is about 8 centimeters higher than in middle latitudes. This causes a very slight slope and water wants to flow down the slope.

Winds blowing on the surface of the ocean push the water. Friction is the coupling between the wind and the water's surface.

A wind blowing for 10 hours across the ocean will cause the surface waters to flow at about 2% of the wind speed.

Water will pile up in the direction the wind is blowing.

Gravity will tend to pull the water down the "hill" or pile of water against the pressure gradient.

But the Coriolis Force intervenes and cause the water to move to the right (in the northern hemisphere) around the mound of water.

These large mounds of water and the flow around them are called Gyres. The produce large circular currents in all the ocean basins.

AND IT'S FULL OF PRETTY PICTURES TOO!!!!

http://earth.usc.edu/~stott/Catalina/Oceans.html