Transit of Venus

[Seshmeister]

http://new.transitofvenus.org/images/stories/107.jpg


http://www.transitofvenus.org

What is a transit of Venus?

When Venus passes directly between earth and the sun, we see the distant planet as a small dot gliding slowly across the face of the sun. Historically, this rare alignment is how we measured the size of our solar system.

This alignment is rare, coming in pairs that are eight years apart but separated by over a century. The last transit of Venus was a thrilling sight in 2004. After June 2012, the next event occurs in 2117.

From the FAQ "Why is a transit of Venus so rare?":

Transits of Venus have a strange pattern of frequency. A transit will not have happened for about 121 ½ years (prior to 2004, the last one was 1882). Then there will be one transit (such as the one in 2004) followed by another transit of Venus eight years later (in the year 2012). Then there will be a span of about 105 ½ years before the next pair of transits occur, again separated by eight years. Then the pattern repeats (121 ½ , 8, 105 ½ , 8).

Transit of Venus pairs since the invention of the telescope:
1631 (not witnessed) & 1639
1761 & 1769
1874 & 1882
2004 & 2012
If Venus and the earth orbited the sun in the same plane as the sun, transits would happen frequently. However, the orbit of Venus is inclined to the orbit of earth, so when Venus passes between the sun and the earth every 1.6 years, Venus usually is a little bit above or a little bit below the sun, invisible in the sun’s glare.

A similar thing happens with our moon. Every month the moon passes between the sun and the earth, yet we do not see a solar eclipse every month. That’s because the moon’s orbit is also slightly inclined to earth’s orbit, so the new moon is usually a little above or a little below the sun. The transit of Venus is essentially an annular eclipse of the sun by Venus.

See the paper plate activity at http://analyzer.depaul.edu/paperplate/Transit%20of%20Venus/transit_frequency.htm for a model that shows the transit frequency visually.



When is it?

The next transit of Venus occurs June 5 or 6, 2012, depending on your location. Observers in North America see it the evening of June 5. This will be the last transit of Venus to occur in your lifetime.

What should I do?

Mark your calendar. Plan your observing location and eye safety. Tell friends. Download and support the ToV phone app. Enjoy the rare sight!

[Seshmeister]

http://www.classicalastronomy.com/news/anmviewer.asp?a=57&z=23

I don't think most people know just how fucking clever people were hundreds of years ago and how they could measure accurately the solar system.



The First Transit

The 1639 transit of Venus was observed by Jeremiah Horrox of England. Horrox was a Christian clergyman, and distinguished himself as scientific observer at a very young age. Being only 20 years old in 1639, Horrox recorded the first observation of a Venus Transit. Horrox set up an telescope system for projecting the Sun's image onto a piece of paper.

Many believe that Horrox may have become one of the great scientists. But he died less than two years later, in 1641, at the tender age of 22. Nonetheless, his first observation and very precise measurement of the Venus transit has earned Jeremiah Horrox a distinigushed place in astronomy history. On June 8, 2004, many observers were at Horrox's former home, to observe the Venus transit from the site of the original observation.

Horrox understood in 1639 that the transit of Venus could be used to actually measure the distance from the Earth to the Sun. It may be surprising to people in our high tech age of space travel, but the size and scale of the solar system were known centuries ago, using the simple geometrical methods known to the ancient Greeks.


Measuring the Solar System

In the 1500s, Mikolaj Kopernik showed that his Sun-centered model of the universe enabled the distances between the Sun and the planets could be discovered using the simplest trigonometry formula. It's a common fact of observation that Venus, at it's "maximum elongation," is about 46 degrees from the Sun in the evening sky. Kopernik reasoned that, if Venus orbited the Sun and not the Earth, a right triangle could be formed between Venus, the Earth and the Sun.

Kopernik supposed the Earth was at an unknown distance from the Sun -- an "astronomical unit." A triangle could be formed where the astronomical unit is the "hypotenuse" (or long side) of the triangle, and the distance from Venus to the Sun would form the opposite side from the angle of 46 degrees. So the distance from Venus to the Sun would correspond to the sine of 46 degrees, which is simply the Venus-Sun distance divided by the Earth-Sun distance.

So since the sine of 46 degrees is 0.72, Kopernik reasoned that Venus was at a distance from the Sun of about 0.72 astronomical units. Kopernik used similar techniques to discover that Mercury was about 0.38 astronomical units and that Mars was 1.5 astronomical units. The problem was, there was no way to measure the amount of the astronomical unit, since you couldn't stretch a ruler from the Earth to the Sun.

The solution was to measure the "parallax" of the Sun. Parallax had been used in Classical Astronomy since ancient times to measure celestial distances. In 100 A.D., the Greek astronomer Claudius Ptolemy used parallax to show that the Moon was 60 Earth radiuses away from our world, which is about 240,000 miles or 400,000 kilometers in modern measurement. This distance was known in Ancient Rome, and throughout the Middle Ages, and is still the correct value known today. This ancient number appears in all our modern textbooks, and was accurate enough to fly nine manned Apollo missions to the Moon and back in the 1960s and 70s.

The word "parallax" is derived from a Greek word that means "to alternate." It is related to the word "parallage" translated as "variableness" in James 1:17:

"Every good gift and every perfect gift is from above, and cometh down from the Father of lights, in whom is no variableness, neither shadow of turning."

According to Webster's, parallax is "the apparent displacement or the difference in apparent direction of an object as seen from two different points not on a straight line with the object." To observe the principle of parallax, hold up your thumb, close one eye, and observe the objects in the background. Now close the other eye and do the same. Notice that your thumb seems to be in a different place compared to the background as you look from eye to eye.

This principle is used in astronomy to measure the relative differences in position between the closer solar system bodies and the more distant background stars. The parallax of the Moon was measured in Ptolemy's time by measuring the Moon's position compared to the background stars, as seen from different places on the Earth. Slight parallax differences were observed between these different locations. From there, simple geometrical methods were used to resolve these parallax differences into the distance from the Earth to the Moon. And this same method was used to find the parallaxes of the other planets.


A Method for Measurement

Even though the parallaxes of the planets could be measured, it was impossible to measure the parallax of the Sun, since the brightness of the Sun cloaked all the background stars. For this reason, there was no way to learn the value of the astronomical unit, which was the key to unlocking the distances of the solar system.

But many decades after the death of Horrox, a method of indirectly measuring the parallax of the Sun was outlined by the great astronomer Edmund Halley, friend of Isaac Newton and famed discoverer of Halley's Comet. Halley suggested that Venus transits could be used to measure the Sun's parallax and discover the distance of the Earth to the Sun.

In 1716, Halley proposed a method for utilizing the Venus transits of 1761 and 1769. Due to parallax differences, the body of Venus would enter and exit at different places along the face of the Sun as seen from different places in the world. And since the Sun's face is curved, the times of transit would vary by latitude on the Earth. So all that was needed was for an observer to measure the times of the "contacts," when Venus's edge touched the Sun's edge, thereby yielding the total time of transit at a location of known latitude. Halley wrote:

"There remains, therefore, Venus's transit over the Sun's disc, whose parallax, being 4 times greater than that of the Sun, will cause very sensible differences between the times in which Venus shall seem to pass over the Sun's disc in different parts of our Earth. From these differences, duly observed, the Sun's parallax may be determined, even to a small part of a second of time;"

Halley died in 1742, nearly 20 years before the transit of 1761. But the transits of 1761 and 1769 were measured by several sets of observers. One such team in 1761 was Charles Mason and Jeremiah Dixon of England. Two years after observing the transit of Venus, in 1763, these astronomers were summoned to America to settle a boundary dispute between the Pennsylvania and Maryland colonies. Using celestial observations, these partners made a survey to establish the boundary between these colonies. This survey line is still known as "The Mason-Dixon Line" to this day, and is the traditional border between "The North" and "The South" in the USA.


Venus and Captain James Cook

The transit of 1769 was observed by Captain James Cook of the H.M.S. Endeavor. Cook travelled to Tahiti in the South Pacific to observe that transit. As Cook wrote in his journal:

"Saturday 3rd June. This day prov'd as favourable to our purpose as we could wish, not a Clowd was to be seen the whole day and the Air was perfectly clear, so that we had every advantage we could desire in Observing the whole of the passage of the Planet Venus over the Sun's disk:"

Cook called the beach from which this observation was made "Point Venus" in honor of the Venus transit. And this beach in Tahiti is still called by this name to this day. After the transit observation, Cook continued with his true mission, to discover the "Terra Australis Incognita" -- the Unknown Southern Continent.

In the process, Cook explored the coast of New Zealand, which he determined to be a pair of large islands. Along the way, Cook gave names to all the places he stopped. In "Bay of Plenty," he found many useful provisions for his ship, while in "Poverty Bay" he found nothing of use. Other places, such as "Hawke's Bay" and "Mount Egmont," were named after various English aristocrats. One place Cook named "Mercury Bay," since a transit of Mercury was observed at this location. These places are known by these same names to this day.

Cook also explored the eastern coast of Australia, and dropped a lot of names there as well. In one place, Cook's naturalists discovered a great number of new plant species, and this place was thus named "Botany Bay." In later voyages, Cook discovered Hawaii, which he renamed "The Sandwich Islands," after the Earl of Sandwich. But this is one of Cook's names that has not stuck!


Finding the Astronomical Unit

Various difficulties were encountered by various transit observers in 1761 and 1769. But when that transit pair had passed, enough parallax data was collected to enable astronomers to place the value of the astronomical unit in the range of 92-96 million miles. This is very close to the modern value of about 93 million miles (149 kilometers).

With this knowledge, the immense scale of the solar system could be known for the first time. This was a fine piece of Classical Astronomy, performed using only the ancient geometry of Euclid and the simplest mechanical instruments. But the thinkers in previous "low tech" generations needed to rely their wits and not lean on technology, as our generation does so very much today.

Another transit pair was observed in 1874 and 1882. With the improvements in instruments and a larger collection of scientific data, the value of the astronomical unit was reduced to 93 million miles, which was the number that many of us adults read in our textbooks when we were kids.

Of course, with such precision at their fingertips, the astronomers of 1882 knew that the next transit would be in the distant, futuristic year of 2004. William Harkness was the director of the U.S. Naval Observatory in 1882. Looking ahead to our generation, here is what Mr. Harkness wrote in that year:

"We are now on the eve of the second transit of a pair, after which there will be no other till the twenty-first century of our era has dawned upon the Earth, and the June flowers are blooming in 2004. When the last transit season occurred the intellectual world was awakening from the slumber of ages, and that wondrous scientific activity which has led to our present advanced knowledge was just beginning. What will be the state of science when the next transit season arrives God only knows. Not even our children's children will live to take part in the astronomy of that day. As for ourselves, we have to do with the present ... "

The June flowers of 2004 are still blooming in our garden, and perhaps yours as well. By his own admission, Mr. Harkness would have had no idea that by this time, space probes would have explored the solar system, and that men themselves would have trodden the face of the Moon. He would not have known that science would have unlocked the secrets of the atom, and the terrible powers that lay within. Mr. Harkness would no doubt be impressed that I could mention him in a message that would be sent "telegraphically" to families in every continent on the globe.

Mr. Harkness would have been stunned to know that we've been able bounce radar signals off of Venus and the other planets. Using this method, we can now measure the millions of miles in the astronomical unit to a precise number, accurate to within a hundred feet! This is a mind-boggling bit of micro-precision, still another wonder of our machine era. And extending this precision, we can now plot the movements of the Earth, Moon and planets to similar accuracy.

Mr. Harkness surely knew that we will have another transit on June 6, 2012. He might have known that the next transit pair after that would be on December 11, 2117 and December 8, 2125. But he might not have known that the 2117 transit would begin at 7:02 PM, Eastern Standard Time, on the evening of December 10. And Mr. Harkness probably was not aware that every transit from 60 A.D. to 3956 A.D. would be known with similar precision, and collected into a book that anyone could purchase for a modest price.

In Mr. Harkness's day, many intellectuals had an abiding faith in science. Many free-thinkers in that generation believed that human wisdom would eventually displace religion, that faith in Jesus Christ would give way to the concrete certainties of Science. Instead, we have seen that Science has become the new "opiate of the masses." Technology has reduced us to a culture of button-pushers. With a calculator in hand, why remember how to do long division?

At one time, many Christians had wondered whether science was the new Tower of Babel, a new attempt for Man to enthrone himself over God. But perhaps the scientific culture instead only offers Man bondage under the Machine? Where will our descendents be by the beginning of the next transit season? When the December snows begin to fly in 2117, when the children of our homeschooled children are great-grandparents (should the LORD tarry), let us hope that there will still be some who can count to ten without the help of a computer!

[katina]

I didn´t know it, thank you for share it.

There is a excelent site automatically calculates your local circumstances based on your internet connection, you can also change your location:

http://transitofvenus.nl/wp/where-when/local-transit-times/

[Seshmeister]

Thanks.

Typical that I get it at 5:30 am, I'm not getting much luck with these things. I bet it's cloudy too.

[Kristy]

When is it?
[/b]
The next transit of Venus occurs June 5 or 6, 2012, depending on your location. Observers in North America see it the evening of June 5. This will be the last transit of Venus to occur in your lifetime.

What should Kristy do?

Mark your calendar. Plan your observing location and eye safety. Tell friends. Download and support the ToV phone app. Enjoy the rare sight!

Oh boy golly!

[katina]

Thanks.

Typical that I get it at 5:30 am, I'm not getting much luck with these things. I bet it's cloudy too.

You need some luck and a clear sky for astronomical observation. I travelled to Scotland a few times for holidays, and I was very lucky to watch the Total Moon Eclipse in January 21 2000 , I was near the Cairngorms in a terrible Winter, what a view!!!

[Seshmeister]

Wow I really liked Buenos Aires although I was working and didn't get much time to be a tourist.

10 Hours to go before this starts - should be able to watch it at http://events.slooh.com/

[katina]

Wow I really liked Buenos Aires although I was working and didn't get much time to be a tourist.

10 Hours to go before this starts - should be able to watch it at http://events.slooh.com/

I guess I will not be able to watch it from Buenos Aires, it´s a pity because we are having a very clear sky now.
Thank you for the link, it will be an incredible spectacle, we will not be alive to watch the Transit of Venus next time in 2117!

Let me know, if you travel to Buenos Aires again.

[Seshmeister]

A day on Venus is longer than a year.

Birthday parties must be mad.

[katina]

Great link Sesh. :thumb:
It´s almost midnight here and I´m watching the transit of Venus!!!

[Nitro Express]

It's overcast and rainy here so I didn't see it. I was glad I kept my old welding helmut because I could see the lunar eclipse we just had. The new self dimming welding helmets wont dim looking at the sun but they will if you just look at a light bulb. I don't know why that is but they are useless for viewing eclipses.

[katina]

it´s rainy there and you didn´t see it?
What a bad luck, you still can watch it: http://events.slooh.com/

[Seshmeister]

Rain here too and I miss another thing.

Worst was the total solar eclipse in 1999 which was completely cloudy, it just went dark.

Next one here is in 2090...

[vandeleur]

Dude with stuff like that we're always gonna be screwed by shitty weather/visibility the only time we managed to buck the trend was when we watched the Leonids in nov 1999 , it said was to cloudy to see anything , and it was in land ,but we went to the coast and the cloud cover seemed to break over the sea .it was weird were we we're we could see all along the coast and the cloud stuck to the land like a curtain but was clear over the sea and the Leonids were spectacular .

[Seshmeister]

The local astronomy society give up in April each year because it gets too light at night this far north. Between that, the light from the city and the rain this has to be one of the shittiest places for astronomy.

[ashstralia]

i set up my little vixen 80mm refractor and took a couple of pics; only 'cause it's the last time we'll see a venus transit.

the aussie media have been banging on all week about how it was capt. cook's journey to tahiti in the 1760's which led to the discovery of 'terra australis', but in fact the dutch had been on the west coast a couple of hundred years earlier.

[vandeleur]

ash u gonna post the pics ?

[vandeleur]

some decent pics on the bbc news website , pics people have sent in http://www.bbc.co.uk/news/in-pictures-18336717

[ashstralia]

ash u gonna post the pics ?

tbh mate they're pretty underwhelming. much better ones here.

[Seshmeister]

i set up my little vixen 80mm refractor and took a couple of pics; only 'cause it's the last time we'll see a venus transit.

the aussie media have been banging on all week about how it was capt. cook's journey to tahiti in the 1760's which led to the discovery of 'terra australis', but in fact the dutch had been on the west coast a couple of hundred years earlier.

Yeah but they just smoked a couple of joints, fucked a few aborigines and wandered off - we created a massive prison island 'Escape From New York' style. :)

[ashstralia]

what's this 'we' business? :)

[katina]

Rain here too and I miss another thing.

Worst was the total solar eclipse in 1999 which was completely cloudy, it just went dark.

Next one here is in 2090...

It´s a matter of luck.
I was lucky only two times with astronomical observations. One was very funny, at least for me, I apologize in advance for my english......

I mentioned before I was very lucky to watch the total Moon Eclipse on January 2000.

I was on holidays at Craigendarroch Lodge, Ballater, Scotland, with my buddy, no chance to go outdoors because of the winter storm and snow. At night he opened a Lochnagar Single Malt (we visited the distillery a couple of days before), and began to drink....I only drink white spirits (vodka, gin, white tequila)....after a couple of hours he said: we are in the Highlands, come on give it a try!.
O.K. I drank 2 glasses....and I went to bed thinking I was going to have a headache in the morning.

The bed was in front of a large window, and because of the spirit I fell asleep in a awkward position, upright with my head hanging out off the mattress, at some point, the neck pain made me open my eyes .........in front of me was a huge Full Moon and a clear sky, it was funny because of my position upside down, the Moon was the same as I watch from the Southern Hemisphere, and I didn´t move.

But suddenly and slowly, the Moon began to be covered from one side....Holly Shit!!! I am totally drunk, I am allucinating!! but I was mesmerized and I watched it until the moon was totally covered and dissapeared into darkness......and I fell asleep.

In the morning I had a headache, I told my buddy that I would never drink a Single Malt in my life again, I didn´t tell him of my strange nightmare because I was a little embarrassed, and while having breakfast and reading the newspaper I saw the title "Total Moon Eclipse", so I began to laugh very loud and pointing to the newspaper and the photo, I told my buddy " I watched the Eclipse"!!!!
I couldn´t stop laughing, my buddy was astonished, he loves astronomy, and asked me "why you didn´t wake me up???" I answered, that I thought I was drunk and allucinating because of the Lochnagar Single Malt!!!

It was just luck, but I am eternally greatfull to Lochnagar Distillery, I laugh each time I recall the amazing Full Moon Eclipse of January 2000!!! :)

[ZahZoo]

what's this 'we' business? :)

Beside being the Carl Sagan of the Roth Army... Sesh still believes the British Empire owns/rules most of the world... Including Venus...

[Hardrock69]

http://news.yahoo.com/blogs/lookout/nasa-provides-rare-images-transit-venus-144840865.html

[Seshmeister]

what's this 'we' business? :)

The wind up just didn't seem to sound right without it... :)

[ashstralia]

:biggrin:

[IceCreamBlondie]

Thanks for the pics, interesting.

[Hardrock69]

Cool video. Dig technology!

[katina]

Thanks for sharing the Transit of Venus. :)

[Seshmeister]

The strange thing was how close Venus looks to the sun in a lot of the pictures when it is 67 million miles away from it.

[private parts]

The strange thing was how close Venus looks to the sun in a lot of the pictures when it is 67 million miles away from it.

This will give some perspective on planetary distance.

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[katina]

This will give some perspective on planetary distance.

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Wow!!! Very illustrative, thanks.

I had an off topic question.....The background music is Sergio Leone????

[katina]

http://i.dailymail.co.uk/i/pix/2012/06/06/article-2155140-1378CE8A000005DC-421_964x483.jpg

[katina]

Sorry, I don´t know why the photo is so big, the entire Transit of Venus.
You will need sunglasses......

[ashstralia]

ok here's my pic for posterity..