Historians discuss astronomer Johannes Kepler in this BBC4 radio broadcast.
As most of you will already know, and much to our disappointment, the Schiaparelli probe failed to land successfully on Mars last Wednesday. The plan was that when it entered the Martian atmosphere, the spacecraft would immediately begin to slow down to 1700 km/h as a result of the friction caused by the atmosphere hitting its heat-shield. When it reached this speed, and was 11 km above the Martian surface, a parachute would open for two minutes to slow it down to 240 km/h. The parachute would then be jettisoned to get it out of the way, allowing thrusters to fire like the brakes on an aeroplane. The spacecraft would then touch down on the planet’s surface at a gentle 10 km/h.
Image from ESA
Unfortunately, what appears to have happened is that the parachute only opened for a few seconds and so failed to slow the spacecraft down. The spacecraft will have crashed into the surface at thousands of…
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The June solstice will fall on June 20 or June 21 this year, depending on where you are in the world. It is the longest day in the northern hemisphere and the day when the Sun is at its highest in the midday sky (see note). The origin of the word solstice is from the Latin words sol, which means Sun, and sistere, to stand still, because around the time of the solstice the Sun stops getting higher, appears to stand still at the same height for a few days, and then gets lower in the midday sky.
The graph below show the maximum height, or elevation, of the Sun, measured in degrees above the horizon, during the month of June. The graph is for a place 50 degrees in latitude North, roughly the same latitude as the southern tip of the British Isles. It shows how the elevation of the Sun changes around the solstice.
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The Seasons of the Moon [The duration of summer and winter on the moon, and the climate zones of the lunar globe] Est autem circulus aliquis inter polos intcrmedius, viccm gerens nostri aequatoris …
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For King Narai, who enjoyed diplomatic ties with the “Sun King,” Louis XIV of France, the “new astronomy” taught by French Jesuit missionaries had important uses for time-keeping and map-making. (Louis XIV himself, after ordering France to be accurately measured with the latest astronomical techniques, grumbled that his astronomers had lost more of his territory than his generals.)
After hearing from visiting French missionaries about the Observatory at Beijing, which had been refitted by Jesuit astronomers for the emperor of China, Narai ordered an observatory built on the grounds of his palace at Lopburi (the ruins of which can be seen today) … It was equipped with the latest European technology, and in 1685, under the guidance of French astronomers, King Narai watched through a telescope an eclipse of the moon.
On April 30, 1688, King Narai had his first chance to observe an eclipse of the sun at Lopburi, but it would also be his last. A Thai court painting … shows a Thai nobleman named Phetracha watching the eclipse projected on a screen while crouched on his elbows and knees in the style of the court. Phetracha resented the king’s friendships with foreigners, and may have feared that the king might convert to Christianity …
According to legend, a fortune teller had warned Phetracha to watch for a sign from heaven that he would become king, and it seems he took the eclipse as a premonition of his ascension: Just days later, he deposed Narai, crowned himself king, and either executed or ordered foreigners out of the kingdom.
For the solar eclipse on Aug. 18, 1868, King Mongkut invited foreign astronomers and important guests to the village of Wa Ko, near the southern port of Prachuap Khiri Khan, which his astronomical calculations had determined would be the best site for scientific observations of the event. Steamships ferried workers and supplies from the capital to build an observatory and residences for hundreds of guests and dignitaries, including almost the entire Thai court, senior French and British diplomats, and a French-led astronomical team.
Mongkut’s predications of the exact timing of the eclipse would be proof of his efforts to reform the Siamese calendar and astronomy — and his rebuke to his court astronomers. According to a report from a French diplomat who was present, the king proudly reported that the French astronomers had confirmed that his predictions were of greater accuracy than their own, says historian Thongchai Winichakul in his book “Siam Mapped”. But for King Mongkut, as for King Narai, this first solar eclipse would also be his last; like many who journeyed to Wa Ko, Mongkut caught malaria and died in Bangkok a few weeks later.
On 6 June 2012, a transit of Venus occurred. This rare astronomical event, when Venus passes directly in front of the Sun, and appears as a large black dot on its surface slowly moving from one side to the other in about 3 hours, has only happened eight times since the invention of the telescope (ref 1). This post talks about the transit of Venus and why it has been so important to the development of astronomy.
The 2012 transit of Venus – Image from NASA. Venus is the large dot on the top left of the Sun’s surface.
Why transits of Venus are so rare.
The Earth takes slightly longer than 365 days, 365.256 days to be precise, to complete one orbit of the Sun. Venus, which is both closer to Sun and moves faster in its orbit, takes 224.701 days to complete one orbit. The point in time when Venus is closest to the Earth and…
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