“Random encounters with the unusual” is a repository for the oddities that me and Mrs J have encountered on our travels, which we find interesting or amusing in some way. Have a look, maybe you will find something interesting or amusing herein.

Tuesday, 21 October 2014

The Home of Halley

The house shown below is on New College Lane in Oxford and is adorned by a small wooden plaque which reads: Edmond Halley Savilian Professor of Geometry 1703 - 1742 lived and had his observatory in this house.

It seems that the English astronomer and mathematician Edmond Halley (1656-1742) spent a significant period of his life in Oxford, firstly as a student at Oxford University and latterly as a professor.  Halley is most famously known for calculating the orbit of the comet that was named after him.

Halley spent some of his career calculating the orbits of 24 comets that had been observed between 1337 and 1698. During these calculations he postulated that three of the observed comets which appeared in 1531, 1607, and 1682 were likely to be the same object returning to the solar system time and again. Based on his calculations Halley postulated that the comet would return in 1758 and on the 25 December 1758 (16 years after Halley’s death) the comet did return. The comet was posthumously named after Halley.

Halley’s Comet is known as a “short period comet” and is the only comet of this type to be visible from Earth with the naked eye. Halley’s Comet is also the only known short period comet that can appear twice within a human lifetime, as its periodicity is around the 75 year mark. Because Halley’s Comet is visible to the naked eye its appearance over the Earth has often been recorded within human history.

The first confirmed historical account of Halley’s Comet dates from 240 BC when its appearance was recorded in a Chinese chronicle. Babylonian records from 164 BC and 87 BC also record visits by the comet. Chinese astronomers recorded the comet’s visit to Earth in 12 BC, and some propose that this visit may have inspired the biblical story of the Star of Bethlehem, as the appearance of the comet was only a few years distant from when Jesus is believed to have been born (circa 7 to 2 years BC).  The comet continued to be observed and recorded over the years and the next most notable appearance was in 1066 when the comet was most famously recorded in the Bayeux Tapestry which chronicled the Battle of Hastings and the death of King Harold II of England.

Calculating the return of the comet was not Halley’s only accomplishment, during his illustrious career he is also known for a number of other achievements. Between 1676 and 1678 Halley recorded the celestial longitudes and latitudes of 341 stars in the southern hemisphere. In 1691, Halley built a diving bell, and with five companions he dived to a depth of 18m in the River Thames where they are reported to have remained for over 90 minutes. Halley further refined his diving bell design and was eventually able to execute dives of up to 4 hours in duration. Halley also pioneered a basic model of a magnetic compass, and established the link between barometric pressure and height above sea level.

Not all of Halley’s work and theories were sound however. Halley was a “hollow-Earther” and in 1692 he proposed the idea that the Earth was hollow and comprised of an outer shell that was 800km thick with two further inner shells and a core at the centre. He proposed that each shell was separated by an atmosphere and that each shell had its own magnetic poles and that they all rotated at different speeds (potentially explaining anomalous compass readings). In Halley’s model of the Earth each shell had its own atmosphere, and he proposed that it was the escape of this gas that caused the Aurora Borealis. Halley also suggest that each shell was illuminated and may also possibly harbour life.

In 1694 Halley proposed that the biblical story of Noah's flood might be an early account of the result of a comet impacting the Earth. This was an idea that was not well received by The Royal Society!

1720 saw Halley participating in the first known attempt to scientifically date Stonehenge. The working assumption being that Stonehenge had been laid out using a magnetic compass and extant magnetic records where used to try to calculate a construction date. Based on this method the earliest proposed date for the construction of Stonehenge was estimated as 460 BC, which as we know today is somewhat wrong, with the current accepted date being somewhere between 3,000 and 2,000 years BC.

So next time you visit Oxford look out for Halley's house, and if you happen to still be alive in 2061 keep an eye on the sky, you may get to see his comet!

New College Lane, Oxford.

The house where Halley lived. 

The memorial to Halley's time in residence.

New College Lane also features this interesting foot bridge that was erected in 1914 to link two buildings of Hertford College. Some say that this bridge is reminiscent of the Venetian Bridge of Sighs

Pictures, Oxfordshire (October 2014).

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