Land Ho

so, many years ago when pirates ruled the seven seas, they sailed in old boats with little maps or navigation equipment.
They were exploring new waters, and often did not know when an island would pop up out of nowhere.

So, thay had a crows nest.
this would allow one or two people to sight land that was further away, being able to see further by having a height advantage. Us REers think that this is due to the curvature of the earth. I have heard that all you FEers have explained the horizon as light refraction/diffusion.. but that doesnt necesarily explain how the light would refract less from the crows nest. Unless possibly the atmosphere is slightly thinner a mere 100 ft or so off the deck?

discuss how being 100 ft higher than your crewmates allows you to see treasure island before it reaches the ground-level horizon. On a flat earth, negligable height upwards should not affect horizon, should it?

Yeah. The air is less dense up there. And the way the light refracts combined with air pollution and the perspective of the observer makes the land invisible when you're too close to the water.

Oh wait, no. No flat Earth explanation makes sense. Good luck getting a decent response.

The light bends up away from the water level to the observer in the crow's nest.

Seeing farther from my house top than the sidewalk, doesn't mean that I'm seeing past the curvature of the earth. It's a perspective effect.

Seeing farther from my house top than the sidewalk, doesn't mean that I'm seeing past the curvature of the earth. It's a perspective effect.

You FE'ers have a pretty funny concept of perspective.

As you change the height of your vantage point the visual horizon moves.

Perspective doesn't prevent you seeing things, it only makes them appear smaller.

You know this, right?

If an objects visual angle is smaller than the eyes ability to discern it, it will most certainly prevent you from seeing it.

You know this, right?

As you change the height of your vantage point the visual horizon moves.

Rowbothian perspective has been disproven.

Quote from: goldstein on October 13, 2008, 11:42:30 AM

Perspective doesn't prevent you seeing things, it only makes them appear smaller.

You know this, right?

If an objects visual angle is smaller than the eyes ability to discern it, it will most certainly prevent you from seeing it.

You know this, right?

People at the waterline are the same distance away as the people in the crow's nest, so this shouldn't matter.

You know this, right?

I have heard several different explanations for the horizon from FEers:

1)perspective(objects same distance away, so it cant be this)
2)bendy light(light bends, ok... why up? by how much? wheres the formula?)
3)Rowbothian's stuff(one "scientist." has yet to be exstensively tested)
4)diffusion/refraction/pollution(places with less water/pollution experience identical horizons)

so which poor explanation is it?
or is it a combination of disproven theories and bad inferences that causes objects to dissappear on the horizon?

When you change your height to a high altitude you are creating entirely new perspective lines with different angles in respect to the earth's surface. Your new perspective lines are broader in relation to the earth than they were at ground level.

Therefore at a high altitude receding bodies will take longer to reach the shallow area where the angles are less than one minute of a degree, where the vanishing point occurs, and where all bodies disappear.

This is why a half sunken ship can be restored by going to the top of a high building, and why an observer can see farther by increasing his altitude.

When you change your height to a high altitude you are creating entirely new perspective lines with different angles in respect to the earth's surface. Your new perspective lines are broader in relation to the earth than they were at ground level.

Therefore at a high altitude receding bodies will take longer to reach the shallow area where the angles are less than one minute of a degree, where the vanishing point occurs, and where all bodies disappear.

This is why a half sunken ship can be restored by going to the top of a high building, and why an observer can see farther by increasing his altitude.

... I am not entirely sure what part of that i understand...
care drawing a diagram?

imagine a 100ft wall, on the horizon.
a person on the ground can only see the top 50ft.
whereas a person 100ft in the air can see the whole thing.

they are looking at the same thing, a line of sight the same length can be drawn from either person to the wall. Also, I do not know what you mean by "broader" perspective lines.

lastly: what is this shallow area? i have been asking horizon questions for weeks and have not heard of this.

they are looking at the same thing, a line of sight the same length can be drawn from either person to the wall. Also, I do not know what you mean by "broader" perspective lines.

On the sinking ship, Dr. Rowbotham describes a mechanism by which the hull is hidden by the angular limits of the human eye - the ship will appear to intersect with the vanishing point and become lost to human perception as the hull's increasingly shallow path creates a tangent beyond the resolving power of the human eye. The ship's hull gets so close to the surface of the water as it recedes that they appear to merge together. Where bodies get so close together that they appear to merge to human eyesight is called the Vanishing Point. The Vanishing Point is created when the perspective lines are angled less than one minute of a degree. Hence, this effectively places the vanishing point a finite distance away from the observer.

Usually it is taught in art schools that the vanishing point is an infinite distance away from the observer, as so:



However, since man cannot perceive infinity due to human limitations, the perspective lines are modified and placed a finite distance away from the observer as so:



This finite distance to the vanishing point is what allows ships to shrink into horizon and disappear as their hulls intersect with the vanishing point from the bottom up. As the boat recedes into the distance its hull is gradually and perceptively appearing closer and closer to the surface of the sea. At a far off point the hull of the ship is so close to the sea's surface that it is impossible for the observer to tell ocean from hull. From the limits of the human eye, the two appear merged.

While the sails of the ship may still be visible while the hull is perceptively merged, it's only a matter of time before it too shrink into the vanishing point which rests on the surface of the sea and becomes indiscernible from the surface.

When the observer goes to a higher altitude suddenly the perspective lines of the viewer in relation to the earth are wider and broader, which means it will take longer for bodies to intersect the Vanishing Point.

Here's a test anyone can perform. In a 3D video game is it easier to see far away bodies at a high altitude, or is easier to see them at ground level?

When you increase your altitude you have changed your perspective lines, and it takes bodies longer to reach your horizon.

Here's a test anyone can perform. In a 3D video game is it easier to see far away bodies at a high altitude, or is easier to see them at ground level?

When you increase your altitude you have changed your perspective lines, and it takes bodies longer to reach your horizon.

uhm i tend to disagree on that. most games have a limited distance of view due to performance reasons . if you´re going to a higher altitude things will vanish because the distance becomes bigger.

Tom, give it up, Rowbothian perspective has been disproven. Your "perspective lines " explanation makes no sense.

On the sinking ship, Dr. Rowbotham describes a mechanism by which the hull is hidden by the angular limits of the human eye - the ship will appear to intersect with the vanishing point and become lost to human perception as the hull's increasingly shallow path creates a tangent beyond the resolving power of the human eye.

Exactly the same argument can be used to show that the sails would merge into the sky at about the same time.

Seondly, here is an image of the oil platform Thunder Horse:



As you can see, the oil rig is nowhere near the limits of angular resloution, yet the legs are still hidden.



Another explanation is needed. If you fail to provide one, we're going to have to declare win for RE.

The light bends up away from the water level to the observer in the crow's nest.

4)diffusion/refraction/pollution

exactly

Sphere_MAN have you ever measured the horizon at different places? Its not the same. At the ocean you cannot see as far as you can in the alps.

Also, what proof do you have that the oil rig isn't photoshopped?

When you increase your altitude you have changed your perspective lines, and it takes bodies longer to reach your horizon.

For the N^th time, On a FE, bodies never reach the Horizon, they only ever approach it.  The higher you are, the more slowly they approach it.