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The Earth moved (ExH). Consider a transformation of the sphere that consists of moving each point by shifting its longitude by \(30^{\circ}\) to the west and by increasing its latitude by squeezing points upward away from the south pole and toward the north pole. This process keeps the north and south poles fixed and spirals points upward toward the north pole and away from the south pole. Describe the movement of the equator under the first two iterations of this process. What points are fixed under this transformation?

Short Answer

Expert verified
Equator points shift west by 60° after two iterations; poles are fixed.

Step by step solution

01

Understanding the Transformation

In the given task, we are transforming the sphere by shifting the longitude of each point by \(30^{\circ}\) to the west. Additionally, latitude is modified by squeezing points towards the north pole and away from the south pole. This means that longitudes decrease by \(30^{\circ}\), while latitudes are shifted upwardly with respect to their current positions.
02

First Iteration of Equator Movement

For the first iteration, assume a point on the equator, where latitude is \(0^{\circ}\). Shifting longitude by \(30^{\circ}\) to the west: If a point starts at \(\lambda^{\circ}\) East, after transformation, it moves to \((\lambda - 30)^{\circ}\). Since the latitude squeezing has the least effect at the equator, the latitude remains approximately unchanged at \(0^{\circ}\).
03

Second Iteration of Equator Movement

For the second iteration, take the newly shifted point from the first iteration \((\lambda - 30)^{\circ}, 0^{\circ}\). Again, apply a \(30^{\circ}\) western shift in longitude resulting in \((\lambda - 60)^{\circ}, 0^{\circ}\). The latitude squeeze is still negligible at the equator, so the latitude stays near \(0^{\circ}\).
04

Identifying Fixed Points

Points are fixed under this transformation if their longitude and latitude remain unchanged after transformation. The poles (north and south) are fixed because they are explicitly stated in the problem to remain unaltered. Any other point would experience a shift in either longitude or latitude, so only the poles are fixed.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Longitude Adjustment
Longitude adjustment is an important part of spherical transformations. When completing this transformation, we adjust the longitude by moving each point to the west by \(30^{\circ}\). This means that if a point is initially positioned at \(\lambda^{\circ}\) East, after applying the longitude adjustment, the point will shift to \((\lambda - 30)^{\circ}\) East.
  • The process involves subtracting \(30^{\circ}\) from the original longitude of any point on the sphere.
  • This westward adjustment results in a clockwise movement when viewed from above the North Pole.
Longitude adjustment is particularly notable at the equator since the latitude remains largely unchanged during this transformation. Utilizing this principle, we can predict the new placement of any longitude line on the sphere. This transformation can cause cyclical changes if applied multiple times.
By understanding longitude adjustments, it becomes easier to see how points are relocated around the globe during complex transformations.
Latitude Modification
Latitude modification occurs when we adjust the position of points on the sphere vertically, in this case, squeezing them upwards towards the North Pole. This significant aspect of spherical transformations affects how points are positioned along the north-south axis.
  • Latitude modification involves altering the latitude of each point away from the South Pole and towards the North.
  • The modification is more pronounced as one moves away from the equator, given the nature of squeezing towards the poles.
While this transformation shifts points vertically, it is subtle near the equator where the effect on latitude is less apparent. Consequently, the equatorial line remains almost in its original horizontal position even after transformations.
However, as points near higher latitudes, this modification becomes more evident, vertically compressing the southern hemisphere and slightly expanding the northern hemisphere.
Fixed Points Analysis
In the analysis of fixed points within spherical transformations, we focus on identifying points that remain unchanged even after applying the transformation laws. In this specific transformation, fixed points are those with unchanged longitude and latitude.
  • The most obvious fixed points here are the North and South Poles, given that the problem specifies them as invariant.
  • For any other point on the sphere, either the longitude or latitude transformation would alter its position. Thus, only the poles maintain their original coordinates.
Fixed points allow us to identify stability in transformations, offering important insights into symmetrical balance and static points on the sphere. The knowledge of fixed points is crucial in analyzing how transformations impact a spherical body and in predicting the outcome of sequential transformations.

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Most popular questions from this chapter

Periodic attraction (S). Again consider the transformation that takes any point \(x\) in the interval \([0,1]\) to \((1+\sqrt{5}) x(1-x)\). As you saw in the previous Mindscape, the number \(1 / 2\) is a periodic point of period 2 , meaning that it returns to itself after the process has been repeated twice. Compute 10 future values of the point \(0.48\) under repeated applications of this process. Do these points get closer to the repeated values of \(1 / 2\), or do they get farther away?

Root repeater. Find a calculator with a square root key. Start with \(0.999\) and press the square root key over and over. What happens to the values? Do you eventually get 1 ? Do the experiment again. This time keep track of how many times you press the square root key to get an answer of 1. Now try starting with \(0.9999\). How many times did you need to press the square root key to get 1 ?

Where to? Using the transformation \(y=3.5 x(1\) \(-x\) ), calculate the first 30 values starting from \(0.437\) and from \(0.438\). Do the results stay fairly close to each other, or do they become quite different?

Does this thing come with a warranty? If you use two different calculators to do the same calculations, are you guaranteed to always get exactly the same answer? Explain your answer.

Two step. Consider the transformation that takes any point \(\mathrm{x}\) in the interval \([0,1]\) to \((1+\sqrt{5}) x(1-x)\). Compute the future values of \(1 / 2\) under repeated applications of this process.

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