the earth

Magnetic Compass and Maps

  • The aviation industry relies heavily on navigation tools and methods.

Understanding Latitude and Longitude

  • Discussed how to find latitude and longitude of a point/city on the Earth's surface.
  • Studied mathematical methods to estimate distance between two points on a global map using latitude and longitude.
  • Question raised: Is it enough to know latitude and longitude to navigate around the Earth? The answer is NO.
  • Need to explore processes available to find destinations for flights, especially 100 years ago before satellite technology.

The Magnetic Compass

  • The magnetic compass is an instrument that shows directions almost anywhere on Earth.
  • It utilizes Earth’s magnetic properties to display directions, functioning day and night.
  • Benefits from magnetic field lines produced by Earth.
  • To understand how it functions, we must study the Earth's rotation around its axis.

Earth's Rotation and Geographic Poles

True North and True South
  • Earth rotates on its axis once every 24 hours, from West to East.
  • This axis creates two points on Earth known as the Geographic Poles: True North and True South.

Visual Evidence of Earth's Rotation

  • Images taken in darkness with long exposure show that the sky rotates around a central point above our heads.
  • This supports the evidence of Earth’s rotation about an axis that runs through Polaris (the Northern Star).

Radius of Rotation and Latitude

  • The radius of rotation varies at different latitudes on Earth.
Radius Calculation Formula

  • The radius of rotation (R) can be calculated using the formula:
    R=REimesextcos(heta)R = R_E imes ext{cos}( heta)

    • Where
      • $R_E$ = radius of the Earth
      • $ heta$ = latitude

  • This shows that every point on Earth travels a different physical distance daily due to variations in the radius of rotation.

  • Daily distance traveled $P$ is given by:
    P=2extπimesRP = 2 ext{π} imes R

  • Example given: Calculate the distance traveled in Calgary over a 24-hour period and calculate speed.

Speed of Rotation

  • Speed of rotation varies with latitude, as Earth rotates from West to East, viewed as counterclockwise from the North Pole.
  • Different latitudes have differing speeds:
    • 90° N: 0 km/hr
    • 30° N: 1100 km/hr
    • 0°: 1670 km/hr
    • 30° S: 1100 km/hr
    • 90° S: 0 km/hr

Consequences of Fast Rotation

  • The molten magma within Earth’s interior spins quickly around Earth’s axis, generating magnetic field lines.
  • These field lines would disappear if Earth stopped spinning.

Earth's Magnetic Field Lines

  • Magnetic field lines surrounding Earth are closer together at the poles, resulting in a stronger magnetic field.
    • Closer, denser field lines at the poles create stronger magnetism.
  • Earth's magnetic field serves as a shield, protecting from harmful solar wind particles that are charged and emitted by the Sun.
  • Some particles trapped in the magnetic field glow as they move through the atmosphere to form lights known as Auroras.

Auroras

  • The glowing light phenomena, such as Auroras (Northern Lights), occur when solar particles are trapped by Earth's magnetic field.
  • The glow is more visible at the poles because of the stronger magnetic fields in those regions.
  • Example given: Observations of Auroras in Calgary.

Magnetic Compass Mechanics

  • A magnetic compass aligns itself with local magnetic field lines around Earth, indicating that Earth behaves similarly to a bar magnet.
  • Magnet Bar's Description:
    • A magnet bar is a metallic piece with two poles: North (N) and South (S).
    • Iron filings can graphically illustrate the pattern of magnetic field lines surrounding the magnet bar.

Similarity of Earth's Magnetic Field to a Bar Magnet

  • The magnetic field surrounding Earth operates similarly to that around a bar magnet, suggesting a large magnet inside Earth affecting the magnetic compass's behavior.
  • Magnetic poles do not align with the axis of Earth’s rotation, causing discrepancies between Geographic and Magnetic poles.

Magnet Movement

  • Magnetic poles are not static; they depend on the rotation of the molten core of Earth related to electromagnetic activity.
  • The current position of the Magnetic North Pole is north of Canada, amid the Arctic Sea, and it continually shifts north and west.

Magnetic Compass Directionality

  • A compass needle aligns with magnetic field lines, indicating magnetic poles' directions distinctly on the Earth's surface.
  • There’s a differing directional orientation between geographic North and magnetic North, creating a local angular difference termed "Magnetic Declination."
Magnetic Declination
  • Declination angle is defined as the angular difference between local magnetic north and true geographic north.
  • Declinations can be either east or west, or in some areas, there may be no notable declination.
Positive and Negative Declination
  • If magnetic north is east of geographic north, it's positive; if west, it's negative.

Magentic Declination Figures

  • A map demonstrates varying declination effects globally with noted projections.
  • Agonic line (zero declination line) described as running from magnetic north along the west of Hudson Bay and extending to the middle of Mexico.
  • Declination effects can vary with time since magnetic north and south poles are in constant motion.

Practical Applications of Magnetic Compass in Aviation

  • Summary of magnetic compass use in aviation for runway labeling:
    • Each runway’s ends labeled based on compass readings (numbers obtained by dropping the zeros).
    • As pilots approach landing, they refer to their compass readings, which may shift over time due to magnetic north’s drifting effects.
    • Example given of YYC runway numbers indicating directional readings.

Importance of Wind Orientation for Runways

  • Importance of a headwind for aircraft during takeoff and landing, enhancing upward lift and reducing rolling distance.
  • Orientation of runways is crucial based on the prevailing wind direction for safety and efficiency.

Runway Design Considerations

  • Aviation professionals assess historical wind data for optimal runway placement and ensure safety in takeoff and landing dynamics.
  • All factors, including historical data analytics, are essential for runway designs, with students expected to collect and analyze weather data for their assigned cities.

Frequency Distributions and Statistical Measurements

  • Tasks include constructing frequency distribution for wind gust data and examining conclusions from these statistical readings.
  • Activity shows construction of histograms and its importance in visual data representation.

Exceedance Graphs

  • Specialized graphs plotted to evaluate days of exceeding certain wind speed or precipitation amounts.
  • Typical tasks to analyze statistical weather data for cities and submit findings for evaluations.

CONCLUSIONS ON NAVIGATION AND MAGNETIC COMPASS

  • The magnetic compass remains a critical navigational tool that integrates various scientific principles. Understanding its workings and the Earth's magnetic properties provides valuable insights into safe navigation and effective aviation operations.

ADDITIONAL ANALYSIS AND EXERCISES

  • Exercises on estimating distances between major cities and calculating impacts of geographical coordinates (latitude and longitude) on navigation.
  • Students encouraged to engage in practical class activities, rounding off their understanding of weather impacts, magnetic declination, and compass usage in aviation aviation.