11. Home and Wandering
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286 Terms
What is a compass?
A device that indicates direction, most commonly using a magnetic needle.
What type of compass is most common today?
The magnetic compass.
What did ancient Greeks know about magnetism?
They knew about lodestone but did not know it aligned with north.
Which civilisation first used magnetized lodestone for navigation?
The ancient Chinese.
What were early Chinese magnetic compasses originally used for?
Spiritual purposes and later navigation by miners.
How did the compass spread to Europe?
Through trade routes.
Why was the compass important during the 15th century?
It made long-distance sea travel and exploration much easier.
Does a magnetic compass point to geographic north?
No, it points toward magnetic north, which differs from geographic north.
Why did compass users need to adjust readings?
Because magnetic north and geographic north are different.
What problem did metal ships create for compasses?
Magnetic metals could interfere with compass readings.
What devices were placed on ships to correct compass interference?
Kelvin spheres and Flinders bars.
How did the compass contribute to the Age of Exploration?
It allowed Europeans to navigate oceans more reliably and explore further.
What is a gyrocompass?
An electrically powered spinning device that aligns with Earth’s rotation axis to find true north.
Why is a gyrocompass more accurate than a magnetic compass?
It points to the geographic North Pole and is unaffected by magnetic interference.
Where are gyrocompasses especially useful?
On ships.
How does a solar compass work?
It uses the Sun’s shadow and position to determine directions.
Why can the Sun be used for navigation?
The Sun rises in the east and sets in the west.
How can an analogue watch be used as a solar compass?
By pointing the hour hand toward the Sun and finding the North-South line between the hour hand and 12 o’clock.
How does the solar compass method differ between hemispheres?
In the Northern Hemisphere, north is closer to the direction opposite the Sun; in the Southern Hemisphere, north is closer to the Sun.
What are GPS receivers?
Satellite-based devices that determine location using latitude, longitude, and altitude.
How accurate are normal GPS receivers?
About 6 metres or better with advanced technology.
What is SuperGPS?
A technology that can measure location accuracy down to around 10 centimetres.
What are star compasses?
Navigation systems that use constellations to guide direction.
Which cultures traditionally use star compasses?
Polynesian and Hawaiian navigators.
What are ephemerides?
Printed astronomical tables showing the daily positions of the Sun, Moon, planets, and stars.
How were ephemerides used in navigation?
They helped sailors calculate latitude and longitude using tools like sextants.
What is an astrolabe?
An ancient instrument used to measure the altitude of celestial objects for navigation.
Where was the astrolabe invented?
Hellenistic Greece.
Who developed the astrolabe further?
Muslim scholars.
How did astrolabes help sailors?
They measured the Sun’s altitude to determine latitude.
What other purposes did astrolabes have?
Predicting star positions and telling time.
Why was the astrolabe replaced by the sextant?
It was less accurate, especially on rough seas.
What was the mariner’s astrolabe?
A simplified, heavier version designed for stability on ships.
What is a sextant?
A navigation instrument that measures angles between celestial objects and the horizon.
Why was the sextant better than the astrolabe?
Its mirrors improved accuracy and allowed sailors to avoid looking directly at the Sun.
Could sextants measure longitude?
Yes, using lunar distances or chronometer methods.
What are log tables?
Mathematical tables using logarithms to simplify calculations.
Who invented logarithms?
John Napier around 1614.
How did log tables help navigation?
They reduced complex multiplication and division into simpler addition and subtraction.
What is a magnetic compass based on?
A magnetized needle aligning with Earth’s magnetic field.
How did early magnetic compasses work?
A needle floated on wood or cork in water.
How did later magnetic compasses improve?
The needle was mounted on a card showing cardinal directions.
When did magnetic compasses spread widely to Europe and the Arab world?
Around the 12th–13th centuries.
Which explorers used magnetic compasses?
Explorers such as Vasco da Gama and Christopher Columbus.
What are the advantages of magnetic compasses?
They are simple, reliable, and require no power.
What adjustments do magnetic compasses require?
Adjustments for magnetic variation and ship interference.
What is a chip log?
A device used to estimate the speed of a ship through water.
How did sailors use chip logs?
They counted knots passing through water over a set time.
Where did the unit “knots” come from?
The knots tied at regular intervals on the chip log rope.
What is latitude?
The north-south position of a point on Earth.
How was latitude traditionally measured?
Using the Sun or Polaris with instruments like sextants or astrolabes.
What is longitude?
The east-west position of a point on Earth based on the Prime Meridian.
Where is the Prime Meridian located?
Greenwich, England.
What is a chronometer?
A precise portable marine clock used to determine longitude.
What problem did the chronometer solve?
The longitude problem faced by sailors.
How does a chronometer determine longitude?
By comparing local ship time with Greenwich time.
How much time difference equals 1° of longitude?
4 minutes.
Who invented the first practical marine chronometers?
John Harrison.
When did John Harrison develop practical chronometers?
From the 1730s to the 1770s.
How accurate were Harrison’s chronometers?
About 5 seconds over several months at sea.
What is magnetoreception?
The ability to sense Earth’s magnetic field for navigation.
Which animals use magnetoreception?
Birds, turtles, salmon, bees, sharks, and whales.
How might animals detect magnetic fields?
Through cryptochrome proteins or iron-based sensors.
What is cryptochrome?
A light-sensitive protein involved in detecting magnetic fields and regulating biological processes.
How do birds use cryptochrome?
They may perceive Earth’s magnetic field as visual patterns or colours.
Why is human magnetoreception considered uncertain?
Humans are thought to have lost most of this ability.
How do human electromagnetic waves affect animals?
They can interfere with magnetoreception and disrupt migration.
What is olfactory navigation?
The idea that animals navigate using smells.
How does Papi’s mosaic model explain pigeon navigation?
Pigeons create a map based on environmental odour patterns.
What is Wallraff’s gradient theory?
The idea that pigeons use large-scale atmospheric smell gradients for navigation.
Is olfactory navigation fully proven?
No, evidence remains insufficient.
What is echolocation?
Navigation using sound waves and echoes to detect surroundings.
Which animals use echolocation?
Bats, dolphins, whales, and some birds.
How does constant frequency (CF) echolocation work?
It uses steady calls to detect movement through Doppler shifts.
Where is CF echolocation useful?
In cluttered environments such as dense forests.
How does frequency modulation (FM) echolocation work?
It rapidly changes pitch to measure distance and object size.
Which echolocation method is used by most bats?
Frequency modulation (FM).
What is Zugunruhe?
A German term meaning migratory restlessness.
What does Zugunruhe show about birds?
Migration is a strong built-in instinct.
What causes Zugunruhe in birds?
Changes in temperature, day length, and hormones.
How is Zugunruhe used metaphorically?
To describe human restlessness or a desire for change.
What is sunlight polarisation navigation?
A method where animals use patterns of polarised light in the sky to navigate.
Which animals detect polarised sunlight?
Insects and birds.
How does Rayleigh scattering create a blue sky?
Shorter blue wavelengths scatter more than longer red wavelengths.
What affects the degree of sunlight polarisation?
The angle of the Sun relative to the observer.
What is spatial memory?
The ability to remember and use information about locations and directions.
What is a cognitive map?
A mental representation of an environment.
Who coined the term “cognitive map”?
Psychologist Edward Tolman in the 1940s.
Where is spatial memory mainly stored in the brain?
The hippocampus.
What is working spatial memory?
Short-term memory for locations, such as remembering where you placed your phone.
What is long-term spatial memory?
Long-lasting knowledge of locations, such as knowing a city layout.
How do dung beetles navigate at night?
They use the Milky Way as a celestial reference point.
Who studied dung beetle navigation?
Eric Warrant.
What did experiments show about dung beetles?
They roll straighter under starry skies than under cloudy or starless skies.
What navigation cues do dung beetles use during the day?
The Sun or Moon’s polarisation patterns.
What are indigo buntings?
Small migratory songbirds that navigate using the night sky.
What did Stephen Emlen discover about indigo buntings?
They use stars as their primary compass during migration.
What were Stephen Emlen’s experiments in 1967?
Planetarium experiments testing how buntings orient using artificial skies.
What did indigo buntings learn during early life?
They learn celestial navigation from observing stars near the Pole Star.
What do indigo buntings rely on for long-distance migration?
Almost entirely on stars.