Ralph J. Coppola --- r_j_coppola<at>hotmail.com

SAS Disclaimer

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Feature

Wow! Here it is --- the 9^th of December! If you observe Christmas, there are only two weeks left for that last minute Christmas shopping. Have you ever wondered what gift to buy for a person who has everything – or – more correctly, for the person who has nothing? Please use the International Gateway to find the office in your country.

What time is it?

The 24-hour clock notation is the most commonly used time notation in the world of today. A few countries, such as the U.S. and Canada still cling to the 12 hour am/pm clock.

ZULU TIME is often, incorrectly, called military time. Actually, ZULU or “Z” refers to one of the various time zones around the globe. The “Z” time zone is centered around Greenwich, UK.

GMT, or Greenwich Mean Time, is a historic term, which, today, is called Universal Time (UT). Universal Time is the local time on the zero meridian which goes through the old Greenwich Observatory, London, UK. The National Physical Laboratory, located in Middlesex, is the current “home” of the British time standard.

Just to make things complicated, the following are some of the various Time Scales that we use to measure time.

UT0 --- precise solar time at the zero meridian (Greenwich).

UT1 --- is UT0 corrected for polar motion.

UT2 --- is UT1 corrected for seasonal variation in the earth's rotation rate. UT2 is often used in astronomy.

UTC --- (Universal Time Co-ordinated) is a time defined by a global collection of atomic clocks. When UTC and UT2 drift apart by more than 0.9 seconds, a leap second is added to UTC.

DUT1 --- is the difference between UTC and UT1 published by USNO rounded to 0.1 second each week.

UTC(USNO) --- is the U.S. reference time published by the US Naval Observatory (USNO).

UTC(GPS) --- GPS time is automatically steered to UTC (USNO) on a daily basis to keep system time within one microsecond of UTC (USNO), (UTC – Leap Seconds = GPS Time).

UTC(NPL) --- UK National Time Scale.

UTC(PTB) --- is the official German reference time signal published by the Physikalisch Technische Bundesanstalt in Braunschweig.

UTC(BIPM) --- is the official time scale that forms the basis for the global coordinated dissemination of standard frequencies and time signals by the Bureau International des Poids et Mesures, Paris.

All these UTC versions do not differ by more than a few nanoseconds. Information about the world time standard UTC (e.g., when will the next leap second be inserted in time, etc.) is available from the 'International Earth Rotation Service' (IERS).

TIA --- (Temps Internationale Atomique) is identical to UTC except that it does not include leap seconds.

Here are a few more time related links:

• More on Time Scales
• Links to Time Sites
• The State of the Art of Amateur Time Keeping
• Precise Time and Frequency for Amateurs
• DIY Time and Frequency Measurements
• Time and Frequency from A to Z
• Time Signals
• Physicists shrink the physical size of atomic clocks.
• A Guide To Metric Time Or Decimalized Time

Wanderings

Build a DIY GPS Based Frequency Standard.

Build an inexpensive DIY External GPS Antenna.

What are antibubbles? Find out with some simple DIY experiments.

• Bill Beaty’s Antibubble Page
• Antibubbles from jtan.com
• Terry's Antibubble Site
• Fluid instabilities in the birth and death of antibubbles
• The Aging of an Antibubble

Also see “The Amateur Scientist” column from the April 1974 issue of Scientific American ---- Curious Bubbles in Which a Gas Encloses a Liquid Instead of the Other Way Around. Along similar lines is the November 1979 column --- Flames in Which Air Is Introduced into a Flammable Gas Rather Than Vice Versa.

If you don’t have access to the back issues of Scientific American and the Amateur Scientist column you can order the complete works on a CD.

Convection in a Box --- These DIY experiments, using smoke, can be performed using a Plexiglas box and a burning stick of incense.

Try some DIY Laser Pointer Holography from Holoworld.Com.

Using a PC and a soundcard-to make a DIY Oscilloscope.

Natural Resources Canada offers near real time and archived geomagnetic data sets from their 12 operational monitoring sites.

The University Of The West Indies Seismic Research Unit.

Java for Astronomy --- by Matt Oltersdorf.

Transits of Venus across the solar disk.

What did they look like? --- Pictures of Famous Physicists.

The Mark-8 Minicomputer --- Some memories of the machine from its designer, Jon Titus.

The Kids Room

Teenangels is a group of young volunteers who are spreading the word about responsible and safe online surfing to other teens and younger kids.

The All Science Fair Projects site contains a collection of Science Fair Projects with Complete Instructions.

Have a look the Experimentals and The Teacher’s Stuff on the Australian Broadcasting Corporation's Science Online site.

Build a simple DIY Vertical Accelerometer.

Build a Glitter Globe.

Physics Lecture Demonstrations from U.C. Berkeley Physics.

Suppliers

Being listed here does not constitute an endorsement by SAS or me of any information, product or service.

Metric and imperial drive mechanical components are available from Stock Drive Products/Sterling Instrument.

On The Lighter Side

Albert Einstein and The World Year of Physics (WYP 2005).

Star Wars.

From The Far Side

Trans-time photography?