h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A9043959 - The History of the Transit of Venus

Thanks Gnomon
I'm onto this and will post again when I've finished.

First para:

The reason a transit doesn't occur every six months is because Venus will not be between the Earth and the Sun each corresponding time. In order for a transit to occur, both planets need to be lined-up exactly. Line-ups occur because..

Links added

Changed: Disinterested Parties --> Uninterested Parties

and

which is where Horrocks lived and made the first recording of a Venus transit-->
which is where Horrocks had lived and had made the first recording of a Venus transit


Removed "Pity poor Guillaume le Gentil (see below)"

That's all I have time for tonight, I'll tackle the restructure next time I'm online.

Thanks again for the feedback, much appreciated

OK, I've had a go at restructuring, and added a pile of links.

The restructuring is good, Annie. It hangs together a lot better now.

I skipped over the figures on my first reading of this. But now I'm, troubled by this:

"Line-ups occur because the period of Venus' orbit around the Sun is almost 8/13ths (243/395) that of Earth's orbitIn simple terms, 13 Venusian years equals eight Earth years."

This looks as if you (or the original author) have put 395 instead of 365 for the number of days in the year, but 243 is in fact 8/13 of 395. So maybe I'm missing something. In fact, this whole bit is a bit mystifying:

The pattern repeats every 243 years, and this will continue until 2846, when a new pattern will be formed.

Is that your work, Annie, or was it in the original? Do you understand it and can explain it better, or should I research it and provide a better explanation?

"This can have important adverse effects on career choices and earning potential," -- I think this is a very callous way of looking at the tragedy of blindness. It may not be meant that way, but that's the way it sounds.

There's a guide entry on Roman Catholicism A533828 which you can use instead of that external link.

You need to put a title tag on the "Protestant" link.

Selsy, Sussex --> Selsey, Sussex

so I guess I could see the transit then --> so I guess I could see the transit, then

G

OK I've had another go - the original entry is here: A2662247
I found the maths elsewhere but it totally confused me, even though I *did* check the math, I completely missed the 395/365 confusion
I've rewritten it omitting that and adding Venus' orbit (year) to try and simplify things.

The pattern still repeats every 243 years, so I've left that in.

I've changed the Roman Catholic link to the EG one, and also added an EG link to Dublinon second look-through (how come you missed that?)

I found a better "Protestant" link on the BBC London website and linked to that.

Got the typo and the comma.

224/365 - it seems both figures were wrong but at least it's right now. Is it alright to leave it at that, because sometimes the science stuff makes people's eyes glaze overand I want this entry read because as you said, it's interesting and I know people who watched it who aren't scientists or even understood the mechanics of the transit, they just watched it because it was happening, a phenomena like the total eclipse.

Meant to post thisThis is the bit I've rewritten:

The reason a transit doesn't occur every six months is because Venus will not be between the Earth and the Sun each corresponding time. In order for a transit to occur, both planets need to be lined-up exactly. Line-ups occur because the period of Venus' orbit around the Sun (its year) is shorter than the Earth's (224.7 days compared to 365). Venus transits occur in pairs with an intervening gap of eight years, with intervals between the most recent transits of 121.5 and 105.5 years.

Sometimes we can observe only one transit because after eight years Venus avoids a second transit by a short distance. This happened in the 14th Century and it will happen in December 3089. Overlooking these exceedingly rare events, we can confidently say that Venus transits reoccur in two pairs every 243 years (121.5 + 8 + 105.5 +8 = 243).

<<.."most individuals who sustain eclipse-related eye injuries are children and young adults. This can have important adverse effects on career choices and earning potential," -- I think this is a very callous way of looking at the tragedy of blindness. It may not be meant that way, but that's the way it sounds.>>

I know. I balked at that, but on other PR threads I'm being accused of using emotive phrases.

Rewritten:
Since it has been shown that most individuals who sustain eclipse-related eye injuries are children and young adults, it is therefore a preventable tragedy. Therefore please teach young children to take care of their eyes to avoid any more tragedies.

Which I hope is non-callous and non-emotive.

Although I'm trying to think of a different word to prevent the repetition of "tragedy" in consecutive sentences.

That's better. The maths makes more sense now. I don't quite understand why it repeats every 243 years, but I'm not worried. I can accept that it does.

The phrasing about children hurting their eyes is better now as well. I remember there was a child who watched the 1999 solar eclipse through a specially modified telescope in an observatory, which had been "made safe". Due to some mistake, the child was blinded. Don't put that into the entry, though, without a better reference than my word.

That's shocking!
Thanks, and I think I have enough info on the safety aspect, especially with Mina's link.

I understand the maths of the 243 years repeat, but not why, but if it reads ok, our job is done.

Are you saying you think this is ready now?

I'll have to give it another read through before I could say that.

Hi,

As promised, I have some suggestions (I had to redo the list I had done before, since you have made many excellent changes since the last time I read this Entry.) but take 'em with a grain of salt, the version you have now is quite good.

Here come my

"The Transit of Venus is a type of eclipse" Perhaps mention here that in contrast to sun-moon eclipses this venus-sun eclipse is barely noticeable, because venus appears only as a small dot passing the solar disk, and this is not enough to turn day into night.

"due to the tilt of Venus' orbit." rather: due to the tilt between the Earth's and Venus' orbits.

"Sometimes we can observe only one transit because after eight years Venus avoids a second transit by a short distance." Sometimes only one of the transit pairs can be observed, because Venus may pass slightly above or under the solar disk on the second turn.

Move the warning to under "Safety First" (reads better).

Under "Safety First" add: "Some of the availiable amateur telescopes come with apropriate filters for observation of the sun. These can be installed in front of the ocular lens. However, one should be sure to read all instructions through thoroughly and seek advice of more experienced colleagues whenever possible."

The whole Copernicus passage can be severely thinned out in my opinion, since right now it reads like: Copernicus could've witnessed it, but we don't know. See what I mean? Also, Copernicus, and other astronomers of the time did not use telescopes. The observations were all made "bare eyed" - It is very improbable that he thought about looking for the venus passage by staring into the sun.

"Copernicus returned to his pastime of observing the planets after a gap of several years, in 1518." While it is true that Copernicus was not primarily an astronomer, I don't think his astronomy can be safely called a pasttime. In my opinion 1518 is a coincidence.

The "alchemy, magic and witchcraft." passage can be thinned out and made into a footnote, IMO

"The 1639 Transit" (and the following) How did they all observe it? Using a pinhole?

Time for an comment - The sections pretty well outline the history of the transit observations.

"The Venus transit of 2012 will be visible in its entirety from Hawaii, Australia, the Pacific Ocean and eastern Asia, so," add: for those living in the western hemisphere the advice is to start saving now.

Phew.



HELL

Why the Western hemisphere? It will be visible over much of western hemisphere and some of the eastern hemisphere. Surely, it should be "for those of you on the other side of the world, start saving now".

Changed
"for those living in the western hemisphere the advice is to start saving now"
to
"for those of you on the other side of the world, start saving now"

"The 1639 Transit" (and the following) How did they all observe it? Using a pinhole?
I have moved the picture which was earlier in the text, down to the Horrocks section:
http://star.arm.ac.uk/venustransit/exhibit/fig11.html - that is how it was viewed and also added that in the text.

<>
Removed as I go into that in detail in my Horrocks entry.

Moved the warning to under "Safety First".

Under "Safety First" added: "Some of the available amateur telescopes come with appropriate filters for observation of the Sun. These can be installed in front of the ocular lens. However, make sure you read all the instructions through thoroughly and seek the advice of more experienced astronomers whenever possible."

Changed:
"Sometimes we can observe only one transit because after eight years Venus avoids a second transit by a short distance."
to
Sometimes only one of the transit pairs can be observed, because Venus may pass slightly above or under the solar disc on the second turn.

Changed:
"due to the tilt of Venus' orbit."
to
"due to the tilt between the Earth's and Venus' orbits"

<<"The Transit of Venus is a type of eclipse" Perhaps mention here that in contrast to sun-moon eclipses this venus-sun eclipse is barely noticeable, because venus appears only as a small dot passing the solar disk, and this is not enough to turn day into night.>>
Put this as footnote one:
In contrast to Sun-Moon eclipses, this Venus-Sun eclipse is barely noticeable, because Venus appears only as a small black dot on the Sun, and this is not enough to turn day into night. (removed the next sentence about Venus being a small black dot on the Sun)

I was trying to think of a different word to prevent the repetition of "tragedy" in consecutive sentences. I came up with:
Since it has been shown that most individuals who sustain eclipse-related eye injuries are children and young adults, it is a preventable tragedy. Therefore please teach young children to take care of their eyes to avoid any more horrific injuries.


I have pared down the Copernicus section as requested to one paragraph, as it's my only chance to talk about the 1518 and 1526 transits. Copernicus is The Man in my eyes and I'd like to leave him in.
<>
I think the opposite, it's too much of a coincidence that he stopped observing the planets years before the Venus eclipse, then started again that year. I think he knew, and he got on with other things while waiting for it.
<>
I don't think he was staring at the Sun, but I do think he found a safe way to project, or maybe just found a way to deflect the image.

Thank you very much for taking the time to review the entry and post your comments, Dr Hell.
Phew indeed

I've added a section on Early Sun-watching. Got a bit distracted talking about the ancient Egyptians and Biblical stories, if it's too much it can be removed.

I like the passage about early sun observations, however, in the way it is written right now it detracts from the main topic of this Entry... Maybe a lighter version would be OK. Allow me to suggest the following :

Since the dawn of time, mankind has been fascinated by the heavenly bodies in the sky, their movements and mysteries. There were astronomers described in the Bible, you may recall the three Magi (wise men) and a certain Christmas story. Long before that, the ancient Egyptians worshipped the Sun as a god (Re-Herakhte), as did the Incas, Aztecs, and a whole bunch of other ancient civilizations. Solar eclipses, obviously, were not considered to be a good sign.

Soon enough people started to realize the usefulness of astronomical observations (think of navigation) and to understand the mathematics that described the orbits of planetsThe Maias, for example, had astonishingly accurate tables describing the orbit of Marcury. From the planetary orbit model it is just a small mental leap that leads to the question whether it is possible to observe a planet passing in front of the solar disk.

------

What do you think? (I know I have butchered your bit quite a lot, and removed all the Isis part - IMO not important here - and the sun-spot observation - IMO also not really relevant here.

Dr. Hell

OK I've done that, but I'd like to leave in the little bit about Brother John, because it shows that as early as 1128, people were studying the Sun safely.

Fair point.

Dr. H

Has anyone else got any comments? I'm happy with this entry as it stands.

I'll try and have a look at it over this weekend, Annie.

Thanks very much Gnomon, have a good weekend