Here you’ll find brief reports of the talks we’ve heard at Society meetings. In these we try to include any web links or other pointers to further information that were provided by the speaker at the meeting. If you were at one of our meetings and would like to correct or expand the report relating to it then please use the Society’s contact form.
In November we scheduled an extra meeting “It’s About Time” presented by Professor Donald Kurtz. Don Kurtz is Professor of Astrophysics at the University of Central Lancashire. His research is in asteroseismology and magnetic stars and he teaches the undergraduate introductory astrophysics course, as well as other courses.
Don’s opening question was “What is time? Is there a past and a future or just a continuously moving instantaneous time?” Rather than enter into a theological or scientific debate about this question, he presented a very interesting, entertaining and, occasionally historically provocative, talk about the measurement of time through the ages, including the surprising scientific variability of it even in modern times. Some of the themes explained were:
As we know, measurement of time today is commonly expressed in terms of seconds, minutes, hours, days, weeks, months and years. However:
Days: We could use Solar days or Sidereal days. When does a day begin? Civil (Midnight); Astronomical (Noon); Swahili (Sunrise), Jewish Sabbath (Sunset). What is the length of a day? There are 86,400 seconds in a day. However, the length of a day is not constant throughout the year. It is affected both by the Moon (monthly effects plus long term tidal locking effect between the Earth and Moon slowing rotation of the Earth around its axis over time), our path around the Sun (being non-circular), effect of seasons (weather/winds and ocean/land tidal friction varying the rotation of the Earth at the millisecond scale). ‘Leap seconds’ are used to keep the correct UTC time of day close to the mean solar time.
Days of the week: These have varied from 5 to 10 days historically and by culture. The Romans used 8 days. Our current 7 day week pre-dates the Old Testament. This was based upon “7 Planets”. However, those were not the planets as we understand them today because the modern solar system was not understood. Instead they were the “7 Wanderers” in the sky, namely Mercury, Venus, (not Earth which wasn’t known as a planet), Mars, Jupiter, Saturn, the Sun and the Moon! Each day was named after one of the “Gods” i.e. Saturn’s day, Sun’s day, Moon’s day, Tiu’s day, Woden’s day, Thor’s day, Freya’s day.
Months: Keeping time with the Moon is awkward but not as awkward as the Roman Republican Calendar which originally had 10 named months followed by a 2 month gap (January / February)!
The Year: Sidereal vs Tropical (solar) year. Impact of Precession over thousands of years.
Don also gave us a historical tour through the history of calendars through the ages up to the modern calendar we commonly use today. This isn’t repeated in this meeting report. However, one example you may recognise is the Julian Calendar introduced by Julius Caesar in 46BC to more closely approximate the Tropical (solar) year. It had a regular year of 365.25 days divided into 12 months with alternating 30 / 31 day durations (apart from February), with a leap day every 4 years. The month of Quintillis was renamed to Julius upon the death of Julius Caesar and given 31 days duration. Subsequently the month of Sextillis was assigned to Julius’ successor Augustus following his death and of course it also had to have 31 days. The transition from the Julian calendar to the Gregorian calendar, again to more closely approximate the Tropical (solar) year, started in 1582 in Italy, Spain and Portugal but took until 1752 to be adopted by other previously Julian calendar countries, including England and Scotland in September of that year.
Don showed us that the calendar has a many interesting and sometimes provocative stories to it and we certainly know more about those than we did before.
A talk by Greg Smye-Rumsby. The planet Uranus is named after the Greek god Ouranos, meaning ‘sky’ or ‘heaven’. It is the coldest of the planets, an ice giant with a tumbling orbit which takes 84 years to orbit the … Continue reading
Roy Easto from Croydon Astronomical Society led a QI type quiz with two teams of two ‘volunteered’ from the membership. This was a change from our usual Christmas Quiz when everyone participates, but the teams played their parts sportingly and … Continue reading
Chris Lintott was unable to visit us as he was on La Palma, so Tony Sizer stepped into the gap at short notice, and gave us an informative and entertaining talk entitled Violent Universe. The Universe is not as benign … Continue reading
At our April meeting Andrew Norton of the Open University spoke to us about Finding Exoplanets. The idea of exoplanets has been around for a long time, but it is only in more recent years that they have been identified … Continue reading
The subject of March’s OAS meeting was The Antikythera Mechanism and the Mechanical Universe and it was presented by Professor Mike Edmunds. He started his talk with a brief history of its discovery. In 1901/2 a hoard of magnificent objects … Continue reading
Our November meeting was addressed by Jack Carlyle, a PhD student at MSSL, who gave us an entertaining and informative talk on how they observe the Sun. With the help of some amazing animations, including one of a collapsing sun, … Continue reading
Our May meeting was addressed by Alec Boksenberg, who gave us a lively talk about The Intergalactic Medium and Other Things. This was a very interesting and wide ranging talk including evidence that dark matter must exist. He said that … Continue reading
Our April meeting was addressed by Paul Money, who gave us a lively talk about his favourite Images of the Universe volume 1. He introduced 10 images and gave an interesting insight into each one. These included diverse topics such … Continue reading
Our October meeting was addressed by Andrew Coates (Mullard Space Science Laboratory), who gave us a talk about ExoMars. Miriam writes: This was a very informative talk about exploration of Mars, and how MSSL is working on an instrument called … Continue reading
Our October meeting was addressed by Brendan Owens (Royal Observatory, Greenwich), who gave us a talk with the title Solar Secrets: Understanding our Star, the Sun. Miriam writes: We were given a whistle-stop tour of the Sun covering sun spots, … Continue reading
Our August meeting was addressed by Alan Aylward (UCL), who gave us a talk with the title Colouring the Sky. Miriam writes: We had an eventful start to this meeting as were locked out at BEECHE! Fortunately Carole was able … Continue reading