General Science

Mount Everest Summited (1953)

posted Friday, 29 May 2015

Mount Everest was conquered as Edmund Hillary of New Zealand and Tenzing Norgay of Nepal became the first climbers to reach the summit on 29 May 1953.

North Pole discovered? (1909)

posted Monday, 6 April 2015

A team of 5 men lead by American naval engineer Robert Peary arrived at the North Pole on 6 April 1909. This claim is subject to dispute.

Charles Hall separates metallic aluminum from rocks (1889)

posted Thursday, 2 April 2015

Aluminum statue of Charles Martin Hall

US Patent 400,664 was awarded to 26 year old Charles Martin Hall of Ohio on this day in 1889. His "Process of Reducing Aluminium from Its Fluoride Salts by Electrolysis" described a new method for the extraction of aluminum metal from ore. Hall’s process reduced the cost of producing aluminum to one half of one per cent of its former value. All humans should travel to his aluminum statue in Ohio and kiss his aluminum toes in perpetual gratitude.

Columbus returns to Spain (1493)

posted Sunday, 15 March 2015

Columbus returns to Palos de la Frontera, Spain ending his first voyage to America on this day in 1493. The journey lasted 224 days or 7 months and 12 days.

Columbus reaches the Azores (1493)

posted Sunday, 15 February 2015

Columbus and crew arrived at the Portuguese controlled Azores Islands 15 February 1493 on the return leg of his first American voyage. This was the first land they had seen since leaving America 30 days earlier. They would arrive at their home port of Palos de la Frontera, Spain on 15 March 1493.

Robert F. Scott arrives at the South Pole (1912)

posted Sunday, 18 January 2015

English explorer Robert F. Scott and his expedition arrive at the South Pole on 18 January 1912, only to discover that Roald Amundsen had gotten there first. Everyone in the expedition died on the return journey. See my post on Amundsen’s arrival for more info.

Columbus leaves Hispaniola (1493)

posted Friday, 16 January 2015

16 January 1493: Columbus leaves Hispaniola on his first voyage. They will not see land again until they arrive at the Azores on 15 February — 30 days later.

Leap Second Day

posted Saturday, 30 June 2012

Today is longer than yesterday and tomorrow by one second.

The hyperfine transition is the basis of International Atomic Time (TAI). By definition, the outermost electron in an ordinary cesium 133 atom cycles through this transition 9,192,631,770 times in one second.

International Atomic Time (abbreviated TAI after the French Temps Atomique International) began at midnight GMT on the first day of 1958 and has continued advancing forward at the rate of one second every 9,192,631,770 periods of the hyperfine transition in 133Cs. TAI is maintained by the Bureau International des Poids et Mesures (BIPM) in Paris, which periodically averages the time kept by various atomic clocks around the world. The BIPM then disseminates correction factors needed to synchronize these clocks with the master clock in the Observatoire de Paris.

Coordinated Universal Time (abbreviated UTC) is the basis of legal time throughout the world. All local civil times differ from UTC by either a whole number of hours or an odd number of half hours, but never by any other amount. One second of Coordinated Universal Time is the same as one second of International Atomic Time, but UTC and TAI are slightly out of step. TAI marches forward uniformly, while UTC is adjusted from time to time to keep it synchronized with the earth’s rotation.

The earth is not an effective timekeeper. For most of the last two hundred years the mean solar day has been slightly longer than the 86,400 s currently defined by the International System. Universal Time UT, or more specifically UT1, is in effect the mean solar time. It is continuous (i.e. there are no leap seconds) but has a variable rate because of the Earth’s non-uniform rotation period. It is needed for computing the sidereal time, an essential part of pointing a telescope at a celestial source.

When UT1 lags too far behind UTC, a leap second is inserted at the end of the day before January 1 or July 1 as appropriate. When this happens, 23:59:59 is followed by the unusual time of 23:59:60 before turning over to 00:00:00 and starting the next day. In the unlikely event that UT1 were to lead UTC (that is, if the earth’s rate of rotation were to increase) the provision exists for the insertion of a negative leap second. Were this to ever occur, 23:59:58 of one day would be followed by 00:00:00 of the next, skipping 23:59:59 altogether. In any case the absolute difference between UTC and UT1 must never exceed 0.9 s.

Leap Seconds and Cumulative Adjustments to UTC
year month offset   year month offset   year month offset
1971   n/a*   1986   23   2001   32
1972 July 11   1987   23   2002   32
1973 January 12   1988 January 24   2003   32
1974 January 13   1989   24   2004   32
1975 January 14   1990 January 25   2005   32
1976 January 15   1991 January 26   2006 January 33
1977 January 16   1992 July 27   2007   33
1978 January 17   1993 July 28   2008   33
1979 January 18   1994 July 29   2009 January 34
1980 January 19   1995   29   2010   34
1981 July 20   1996 January 30   2011   34
1982 July 21   1997 July 31   2012 July 35
1983 July 22   1998   31   2013   ?
1984   22   1999 January 32   2014   ?
1985 July 23   2000   32   2015   ?
* Adjustments from 1961 to 1971 follow a different, more complicated protocol and were omitted

Are leap seconds even necessary?

  • In seven or eight centuries the difference between TAI and UT1 will be about an hour.
  • By the year 5000, day and night will have reversed; that is, 12 noon will occur in the middle of the night and 12 midnight will synch up with the midday sun.

What would be so wrong with that? Does it really matter what number we assign to a position of the sun in the sky?

In 1582 Pope Gregory XIII managed to extract ten days from the calendar. On 4 October 1582 the Catholic world went to sleep. When they woke up it was 15 October 1582. By 1752 the protestant nation of England and her American colonies also accepted the change. (They needed to add 11 days to catch up.) In 1873 Japan made the switch. (They needed 12 days.) Then Russia in 1917 and China in 1949. (13 days.) The Greek Orthodox Church is possibly the only European agency that has not accepted this change (although the nation of Greece made the switch in 1923).

I think the big thing is that everyone agrees what time (or day) it is. Not that the time is any particular number. Time is a social construct, remember.

Science caught in the Web 2010-02-13

posted Saturday, 13 February 2010

Science caught in the Web 2010-02-06

posted Saturday, 6 February 2010