On A Forgotten Island: CR4 Challenge (03/18/08)

Indeed we are the centre of the world, see the horizon stretches all the way around us no matter which way we look.

It is possible that they see the waves coming in from all directions comfirming their theory. If the ocean wind was light and the day hot, you would have air rising over the island and the apparent breezes effectly being toward the shore on all sides. This would crate the effect of waves coming in evenly on all sides. But there would be almost no waves farther out away from the island.

Exactly, and a nice graphic too.

There is a possibility of two or possibly three wave trains caused by a shift in wind direction and current. But in a steady state this is it.

what did they see when they got to the top of the mountain-more water!

That's a good one!!!

http://www.hindu.com/thehindu/seta/2002/02/14/stories/2002021400210600.htm

I'm guessing a change in colour denoting a shelf causing refraction.

I think the principle is right, but it needn't be a shelf - a slope would do as well. Essentially, the phase velocity of the waves is greater in deeper water, so the waves will indeed be refracted so their fronts run close to parallel to the shoreline when they break. Other than under Rick Lee's conditions, more careful observation would show that they are not truly perpendicular to the shore. If J & T stand as near the water as possible you check the time that the waves break at the furthest points they can see to left and right there will still be an observable time difference. This will be much clearer if they can still see the breaking waves from a high point in the centre of the island. Things may not be too clear further out to sea, where there could be several families of waves running in different directions.

Is it possible that the waves hitting the beach are reflected from a seawall, coral reef or some other physical barrier? That's the only way I can imagine waves being propagated from all sides at the same time.

A semi active volcano. With hot air always rising, there is constant on shore breeze causing incoming wave action on all sides of the island.

In fact, what they see is two things...

1. Their island isn't round, but somewhat eroded on one side and somewhat less eroded on the other. This occurs because the prevailing winds/currents cause more wave activity on one side of the island than the other.
2. They see that the wave action on their island is far from uniform from all directions. while waves crash on one side, wave action is a lot less on the opposite side. And is a far better place to launch and land their dugout canoe.

Wiki-wacky-woo!!!

Rising and falling tide reacting with the Island shelf? Assisted by the surface currents as outlined in post #2.

Regards JD.

What did they see?

Depending on how high the mountain was, it could have been colder, if shrouded in fog/cloud, they don't see much, tomorrow, the prevailing winds may be different, so the waves may hit the Island differently, so discerning that there is something else out there (over the edge) from day to day, they will still be center of their "world"..

Or, they look down upon their village, and see that their world is so much more comfortable that the "Great Unknown" and that Juanas' wife isn't really doing the chores she is supposed to be doing, they forget what they were up there for, and watch what she is really doing below :D

Just throwing an idea out there...

Did they not just see an icy landscape and lots of penguins, polar bears etc (depending on which pole they were at).

*Awaits a torrent of replies reasoning why they could not have been at a pole*

"Did they not just see an icy landscape and lots of penguins, polar bears etc (depending on which pole they were at)."

Kev,

Better review High School Geography. There is no land at the North Pole, let alone a mountain, just miles and miles of flat ice floes.

Technically, you could call Antarctica (the continent on which the South Pole is located) an "island" in the same way that Australia is an island (although I am not sure if there is a mountain at its very center) but I think it would take a very, very, very long time for two people to walk around its perimeter! Besides which, there are no native Antarcticans, only teams of visiting scientists and their support staffs, as well as a few crazy tourists.

No, no, no...

They actually saw the rest of the survivors of Oceanic flight 815, a few beach dwellings, a ship in the middle of the island, a settlement of basic houses, a burning submarine, a couple of polar bears (???) and a plume of mysterious black smoke.

Well, so much for "untouched by modern society"!

It's one thing to interject levity, quite another to ignore the information given in the question. Doesn't anyone play by the rules anymore?

But didn't find the hatch!!!

Natives on a forgotten island, untouched by modern society with waves all around? Its not just the center of the world, to them thier island would be the center of the universe! To me it would be paradise, nirvana, heaven on earth. I'd just need my quiver of surf boards.

BobD is dead on, but what they saw from the top would be a lesser wave energy hitting the leeward side of the island due to the refraction of the swell energy in the shallower near shore waters. They probably deduced that they were just off center. They also likely pinpointed the island's best point break.

"Juanas and Thoman are natives on a forgotten island somewhere in the ocean untouched by modern society. One day while out for a walk around the perimeter of the island Thoman deduces their island must be at the center of the world. As they walk together around the island he shows Juanas that the waves are always crashing into shore from every side. Juanas, not being easily convinced, said lets climb the island mountain and look at the waves. What did they see when they got to the top of the mountain."

When they got to the top of the mountain they found a wise old medicine man sitting in a lotus-like position mumbling some words, mantra-like, over and over under his breath, unaware of their presence. Thinking that this guru must have the answer to their question, indeed, to all their questions, they creep closer, reverently and respectfully, to await the seer's inevitable pause in his reflections, so that they might beseech him to provide them with the ultimate truth of their existence on the island.

Coming ever closer, they begin to hear what the old man is mumbling......

"....Chicken or egg? Chicken or egg? Chicken or egg?........"

Thoman was right - they were at the center of their world - and at the top of the mountain they were on top of their world. I wonder if they realize how lucky they are not to be touched by modern socierty?

What they would have seen is a relatively calm sea further out to sea but incoming radial waves closer to shore as a result of adiabatic uplift from the heat of the island generating sea breezes. If they wait until evening, they would see a similar wave pattern but in reverse, the waves would be radiating out away from the island as a result of the sea breezes generated as cooler air leaves the island, pulled seaward by the ascending air over the now relatively warmer sea water.

Bob Holt, Belleville, Ontario, Geographer and sailor.

As they walk to the top of the island they should see the waves coming in from a prevalent direction. The waves will continue on as the curve of the island recedes on each side which allows the wave to lap in a perpendicular mode from each side; they should meet at the opposite side and cross somewhat to create a wave on this side also.

At the top of the mountain they see another island that is just beyond the horizon when they are at the beach. They also see waves approaching the other island.

Kris, Kris, Kris... How can you say such things? Let's review:

"They didn't see anything." First, this is not possible. From the top of the mountain, when they looked down they at least saw all of their island and some of the surrounding water. The question is, what ELSE did they see?

"On their planet, the land mass takes up all of one hemisphere and the mountain wasn't big enough to see the shore." On their planet? There is nothing in the question that implies they are on any other planet than Earth. Even their names are Earth-like rather than some Alien-sounding names. "And since they walked around their island "one day" and saw "that the waves are always crashing into shore from every side", they must have completed their journey in a reasonable time, on foot, which implies that the island is rather small. And if the mountain wasn't big enough to see the shore, why would they choose to go up it, hoping to observe more of their world than they could see from the shore? It is implied, therefore, that they believed they could easily survey the entire island from the top of the mountain, so it had to be sufficiently large to see the shore.

"To make matters worse, they didn't know if they were on island in an ocean, or on a landmass with a lake." This one I would give to you, if the darn text didn't say, "on a forgotten island somewhere in the ocean". So it is pretty clear that even if they didn't know it, they were on an island in an ocean.

"If Juanas and Thoman are at the 'centre of the world', it must be the scene depicted in the film 'Journey to the Centre of the Earth'."

Now, wait a minute. If I am an island native, "untouched by modern civilization", I have no idea that the earth is round. I would assume it is flat, since the ocean and much of the land (except for the one mountain and a possibly a few foothills) appears to be flat. After all, even up to Columbus' day, most Europeans (and many others of course) believed that the Earth was flat, and if you sailed too far, you would fall off its edge. Therefore if all I know is my small island, and it is surrounded by water, I could easily believe it was at the center of my flat world! Your reference is to a film based on the notion that the earth is roughly spherical and that by descending through a hole (or in this case, a volcano and a system of connected caves and passageways) you could arrive at a point in the approximate center of that sphere. There is nothing in their knowledge base or physical observations that would make our islanders think that were possible, let alone true.

Nothing in the question to say they are on this Earth either. Kris just hypothesised some constraints which meant they would see nothing relevant. It's one of the standard tricks people use on CR4 to trivialise questions - though to be fair I've never noticed Kris use it until after someone had presented a more-or-less satisfactory answer.

Even suppose the world has a diameter of 50-miles, and the mountain is 1-mile high, the diameter of the (roundish) island only has to be 15-miles and they would still not see the sea. That's probably a couple of earth-days walk to inspect the shoreline - quite long enough for the wind to shift...

Astronomers on Kris's island would probably have worked out that the island was (aproximately) a hemisphere.

OK, I'll bite. If I accept the hypothesis that they are not on Earth, can we at least agree that these are humans or humanoids? It sounds like they walk, and talk, and think like humans anyway.

Given the above, you had better redo your calculations. How many planets with Earth-like conditions that can support human or humanoid life (without some sort of artificial life support, after all these are primitive natives, "untouched by modern society") with a planetary diameter of only 50 miles? Unless there is a super-dense core, which would probably present other problems to human/humanoid life, there would not be enough gravity to maintain a breathable atmosphere, let alone a hydrosphere, or allow these poor creatures to "walk around" the island. Try several thousands of miles at least, and I bet you will get very different answers.

The premise is ludicrous. I think my "medicine man" scenario is much more plausible!

Since they are the first iteration of life, they probably wouldn't have had time to devise a concept of a spherical globe. It can be assumed that they know nothing of te world since they are still wondering about the waves surrounding their island. It took how long for all of the civilizations of the world to determine the Earth was round? Gallieo is spinning in his grave hearing your remarks (though I'm not sure if he is following the magnetic tendencies of Earth).

:P

Damn it, they'd still be fornicating on the hill...it's much more enjoyable

It is intuitively obvious, to the most casual observer, that they are inescapably caught in the (twilight zone)... Figuratively speaking, of course...

Being untouched by modern society, why would they ever formulate the possibility that they were not the center of creation?

As I vaguely recall, the curvature of the earth limits horizontal vision to about 14 miles. So, at sea level, they would see from sea level, nothing but water, outwards, for a radial distance of some 14 miles in all horizontal directions. The height of the mountain is not provided, so the width of the additional radial distance is not quantifiable with the given information. However, the fact that the water waves ebb and flow uniformly would tend to suggest that their island is really within a very large lake that is not subject to major currents that occur in open oceans. Thus, if the mountain were tall enough, the two natives might see the boundaries of their "world Lake"... Then, if history is any guide, they would resort to some sort of a struggle to determine which one would become the controllor, and which one would become the controllee. Prematurely, one would die from anyone of several causes, and the other would expire shortly thereafter, therby forfeiting their island paradise back to the control of the non-human residents, allowing the island to return to a previous state of ecological balance, to await the next evolutionary mutation to produce a new, and less narcistisic, top predator... Until the first real estate developers arrive, and then the neighborhood will really go downhill...

OK. So far, we've come up with a bunch of stuff the two could see from atop their mountain - another island, varying wave patterns, and their island wasn't round. So what the heck is the answer you had in mind...

Tell us or we'll hunt you down like the dog you are!!!

I know what they saw at the top of the mountain - a map! It fell out of an airplane that flew over the island at an altitude high enough so that they could not see or hear it! They thought the map was a message from the gods...

Yeahhhhhh. right!!!!

The names and info given sort of hint at Tristan da Cunha, not that that leaves me any the wiser.

Zee isle of a love!

Are we still waiting on a final/correct answer, or did I just overlook it?

Its getting boring .......!

I think CR4 is just a little slow putting it up today.

We will just have to be a little patient!

Too bad there is not a means of notifiying partipants when the answer is put up, in the same way that new postings are announced by e-mail.

I could not agree more.....

I do not agree with the answer. The real waves are nothing but up and down mothion of the water. It is something like, if we move the other end of the rope tied to some object, up and down. The waves of rope are similar to waves in sea, we see. No actual lateral motion is there. Thus away of shore are the waves of no lateral movement

The motion of water at the edge, we see, is local motion due to wind pressure from all sides, thus waves are always towards sea shore. Besides the waves generated due to high tide effect are bound to be towards shore as water rises from all sides.

The answer given may be simplistic, but aspects of your rejection are also incorrect.

If the surface rises, the water has to come from somewhere. That requires lateral movement of the water. If the wave were infinitely deep, the lateral velocity could theoretically be zero. But actually the waves you see on water are surface waves, with most of the motion in the region near the surface. This includes a good illustration. (In shallow regions the lateral movement becomes more pronounced, of course)

WEAK, very weak, in fact it was so week it was nearly a fortnight!!!!

Has any one disproved they indeed where not at the center of the earth !!!! Just because a few waves have strange affect, does not negate the possibility of them being at the location...

You should know that the Earth has a few centres - Washington, London, Tokyo, New York... to the best of my knowledge, none of these are "on a forgotten island somewhere in the ocean untouched by modern society" (though in some cases we may wish it were so).

There are many many centres on the earth. All Self centred persons have these certres, which move with them.