Post on 27-Mar-2015
transcript
Time and TideWait for Gnomon
ByRoger BaileyNASS 2006 Vancouver
Newcomer’s Tide Questions
• Tides are caused by the gravitational attraction of the sun and moon but….
• Why are there sometimes two tides a day?• Why are tides really high and low twice a
month?• Why are the really low tides in the middle of the
night in the winter and midday in summer?• Is there better information available than the
newspaper tide tables?• Can sundial science answer the “Whys”
WHY?
Sundial Science: What Can You Learn from a Stick & Shadow
• Daily cycle of sun– Sunrise, sunset, noon– Time, Hours, Longitude
• Yearly cycle of Sun– Solstices, Equinox– Date, Declination,
Latitude
• Monthly lunar cycle– Lunar Day ~25 hours– Phases, eclipses,
obliquity – Saros cycle ~18 years
Tides?
Moon Dials
• A sundial can be used as a moondial– When the moon is full– 12 noon for the full moon is 12 midnight– Adding ~ 48 minutes for each day past full– Subtracting ~48 minutes for each day
before full moon (actually 48 +/-7)• Full moon declination ~ opposite sun
+/-• Exactly opposite for lunar eclipse• Exactly equal for solar eclipse
Moon Madness: SML 1999
• Proposed dual frequency harmonic sinusoidal tidal sensing correction system for a Moondial
• Daily tidal variation dampened
• Monthly tidal changes adjusted moondial hour angles
WellDampenedLevel Sensing
Tidal Sea
Patents Applied for: R. Bailey, R. Goldberg, H. Robinson
Aluna: Tidal Powered Moon Clock
• “Imagine a breathtaking sculpture that combines cutting edge design and technology with an ancient knowledge of the Earth's natural rhythms.”
• “A monumental timepiece for the planet, a beacon for a sustainable future, reconnecting people with the Moon and tides”.
http://www.alunatime.org/
Proposed for UK & Australia
Aluna Time
• Wax & Wane ring – 29.5 day lunar cycle
• Moon’s position, – rise & set– Lunar time
• Tidal Ebb & Flow– Aluna’s heartbeat– 12:25 cycle– 2:1 synchronicity with
Lunar time http://www.alunatime.org/
Simplistic tide clock concept based on two high/low per dayDoes not show phase, latitude, or declination effects
Tides: Vancouver Aug 16-23
NewSun = Moon In Phase
One Low / Day AM Solar
http://waterlevels.gc.ca
High (Spring) Tides
Sun and Moon Effects
New Moon
Full Moon
Tides: Vancouver Aug 24-31
NewSun = MoonOut of Phase
Two WeakLows / Day
http://waterlevels.gc.ca
Sun and Moon Effects
Quarter Moon
Quarter Moon
Low (Neap) Tides
Tides: Vancouver Sept 4-11
FullOne Low / Day Two Lows / Day
http://waterlevels.gc.ca
Harmonic Analysis: Equation of Time
• Sum of periodic changes to solar day
• Sum of obliquity and eccentricity effects
• Obliquity: – tilt of earths axis
• Eccentricity:– elliptical orbit
http://www.analemma.com
Harmonic Analysis: Tides
• Sum of waves of different amplitudes and periods
– Sun: 24 hr day. 12 hr tides, Noon & Midnight 1 year, Solstice, Equinox, Declination
– Moon: 24:48 hr day, 12.5 hr tides, monthly 29.5 day orbit, Phases, Declination Eclipses, Ecliptic, obliquity, Saros
– RC resonance: velocity, volume, frequency – Phase shifts,Time delays, Shallow vs deep,
funnel effects
Tide Tables: Hydrographic Surveys
• Click on http://waterlevels.gc.ca and follow the links, maps etc for your location
• US Data: NOAA • National Oceanographic and Atmospheric
Agency http://tidesonline.nos.noaa.gov/geographic.html
• UK Data: UKHO Admiralty Easy Tide http://easytide.ukho.gov.uk/ $
NOAA Tide Graphic
Computing Tides on your PC
• Windows Tide and Current prediction program http://wxtide32.com/
• Install the free shareware on your PC• Set up your preferences like your location• It also includes locations for currents• Based on NOAA Harmonic Analysis
models and factors from world wide public sources
• Problems with use of UK harmonic factors and UKHO copyrights
Typical WXTides32 Screen
Now
DaytimeNight
High Tides during day?
Full Moon
Latitude & Season Declination Effects
Summer
Phase shift to high tides at night!Tides lag behind gravity and water takes time to flow
Solstice Tides: Summer
Negative Tides: Mid-day
New
Solar and Lunar Declination highDay (SUN) dominant
Sun and MoonIn phase
http://waterlevels.gc.ca
Latitude & Season Declination Effects
Highest Tides at night for our northern latitude
Full Moon Winter
Phase shift to daytime high tides!Tides lag behind gravity and water takes time to flow
Solstice Tides: Winter 2006
NewSolar and LunarDeclination low, in phaseNight (MOON) dominant
Negative Tides: Mid-night
http://waterlevels.gc.ca
Solstice Tides: Winter 2007
Solar Declination low, Lunar highOpposite but in phaseNight (MOON) dominant
Negative Tides: Mid-night
Full
http://waterlevels.gc.ca
Time and Tide Wait for Gnomon
• Sundial (Stick and Shadow) science is useful for understanding tides
• Tides are caused by the harmonics of solar and lunar cycles
• Sundials show solar cycles, time of day, day of year, seasons and harmonics
• Moondials show lunar cycles• Latitude and declination are important
for shadows and tides
Shadows and Tides
Time and TideWait for Gnomon
ByRoger BaileyNASS 2006 Vancouver