I really don’t know why Esther Inglis-Arkell thinks that she is qualified to write about science, the examples I have seen so far show very clearly that she should spend her time doing something else. After her Cantor debacle she now screws up the history of the black drop effect. Let us examine her offering on the science fiction website io9 for accuracy.
We can see Venus pass in front of the sun once every one hundred and twenty years.
Actually it’s twice in one hundred and thirty years. In intervals of approximately one hundred and twenty and then eight years
Ever since it’s been observed, a strange thing has been happening.
Horrocks the first to observe a Venus transit in 1639 did not record the black drop effect.
Instead of appearing as a dark circle moving across the sun, Venus formed a tear drop shape that slowly oozed onto the solar disc. It took three hundred years for scientists to understand the Black Drop Effect.
It’s actually still contested as to whether we can explain it or not.
In 1769, James Cook was in Tahiti, trying his best to set up telescopes.
No mention of Charles Green the actual astronomer of the expedition or Joseph Banks who also took part in the observations.
His trip over was partially sponsored by the Royal Academy, for no lesser purpose than laying out the solar system itself.
They got the expedition organised real quick considering that the Royal Academy was only founded in 1768. Maybe she meant the Royal Academy of Music but they were first established in 1822. Perhaps she meant the French Royal Academy of Science? Oops Cook was English wasn’t he. The expedition to Tahiti to observe the transit of Venus was organised by the Royal Society and paid for by the British Government.
People knew, roughly, the order of the known planets, but they had no way to know the actual mileage involved. How far were the planets from the sun?
People knew the order of the known planets exactly. They also knew the size of the planetary obits relative to the size of the Earth’s orbit around the Sun. If one could determine the latter then one could automatically determine the size of all the other orbits.
One way of finding out was taking a look at how fast a planet crossed a known distance, like how fast Venus moved from on side of the sun to the other.
You actually need to determine the transit duration from two different points on the Earth in order to then, using parallax and trigonometry, determine the distance not of the planet, as half implied here, but of the Sun.
The problem was, a ‘transit of Venus,’ when Venus passes between the sun and the earth, happened rarely. An eight year period saw two of them, and then there were no more for another 120 years. The astronomers needed to make the most of their chances.
Didn’t she just tell us that there is only one transit in one hundred and twenty years?
Cook observed the transit, and made a drawing of it in his journal. Oddly, the journal showed not a black circle passing in front of a bright one, but a transit that looked like a drop of water falling from a surface. The black spot had a wide base for too long a time, as if it were water coalescing into a drop. Then it tapered off into a tail, and broke free, moving as a circle across the sun.
The black drop effect was well known to Cook, Banks and Green before they made their observations as it had been observed and recorded by many astronomers during the 1761 Venus transit.
This has been observed regularly since then. The Black Drop Effect has puzzled astronomers for centuries, and only recently have two astronomers figured it out.
Actually many observers in 2004 saw no black drop and as already stated the explanation reported by Inglis-Arkell is still not accepted by all astronomers.
I’m curious what subject Ms Inglis-Arkell will choose next to display her extensive ignorance.