>> From the Library of Congress in Washington, D.C.
[ Background sounds ]
>> Jennifer Harbster: So I'm Jennifer Harbster.
I'm a Research and Reference Specialist for the Science,
Technology and Business Division here at the Library of Congress.
I'd like to welcome you to today's program --
a rare astronomical event, the "Transit of Venus."
This program is the third in a series of programs in 2012
that is presented through a partnership between my division
and NASA's Goddard Spaceflight Center.
And I believe this is our sixth year partnering with NASA.
Our speaker today, Sten Odenwald, is an astrophysicist at Goddard
and Senior Scientist with ADNET Systems, Inc.
He received his Bachelor's degree in astronomy from UC- Berkeley
and his Master's and doctoral degrees
in Astronomy from Harvard University.
Stan remembers the moment when his sense of wonder for the stars began.
He was ten years old, and his father pointed to the three stars
in the Belt of Orion, and said,
"Look how bright the Three Wise Men are tonight."
As a result, astronomy books replaced his rock collection,
he became a fan of the science fiction television series
"Outer Limits," and he built his first telescope These days Sten
investigates star formation, galaxy evolution, and the nature
of cosmic infrared background,
and he is currently studying the historical impact on humans
of space weather, such as solar storms.
A vigorous promoter of science education, Sten is the director
of Space Math, a program that develops K through 12 math problems,
featuring discoveries from across NASA.
He shares his love of astronomy with the world
with his award-wining Astronomy Cafe and Space Weather websites,
as well as appearing in National Geographic television specials
and Discovery Channel's "Naked Science" show.
And he's not naked, I have to say.
Sten also takes time to lend a helping hand to librarians.
For example, several years ago he helped me with a page
on the Northern Lights for our Everyday Mysteries website.
In 2004, he spoke at the library about the transit of Venus,
and assisted the Music Division
with their web-based performing arts encyclopedia entry
for John Philip Sousa's "Transit of Venus" march.
We are happy to have Dr. Odenwald back to the Library to talk with us
about this rarest of planetary alignments.
The Transit of Venus comes in pairs, eight years apart,
but separated by more than a century.
This year the transit will be visible
in North America the evening of June 5.
The previous transit, of course, was in 2004.
After this lecture, I hope all of you will mark your calendars
so you will not miss this rare astronomical event,
because we will not see another transit of Venus in our lifetime.
The next transit will take place in 2117 and 2125.
And now, please join me in welcoming Dr. Sten Odenwald back
to the Library of Congress.   [ Applause ]
>> Dr. Odenwald: Thank you very much.
It's nice to be back here eight years later.
I think most stars tend to have a shorter re-invitation period
than eight years, but I'm grateful for the eight-year period;
that's works well, and that it's cosmically inspired.
That's kind of cool, too.   Well, it all starts with Galileo.
We're going to get to the transit momentarily, but talk a little bit
about technology and how the transit idea was even discovered
in the first place.
As we know, Galileo invented the telescope,
and used it to basically study Jupiter and the planets,
and also the sun and sun spots, things like that.
You can't imagine what 1609 must have been like.
Galileo sort of invents this new technology.
The general public had no concept of being able to view things
at a distance using a telescope to magnify images,
and so they didn't really have any understanding
of how to use the technology.
The original attempts were actually confusing.
The first attempt was probably illegal in most countries,
and the other one is definitely inappropriate use
of the telescope to view the Pope.   So it was a confused period,
but eventually they got things straightened out.
And Galileo observed Venus, discovered that it had phases,
looked at Jupiter and discovered it had moons.
So that sort of begins our telescopic study of Venus
and since then, NASA with its spacecraft has done even better.
Of course, we can send spacecraft there
and take first-hand observations of what Venus looks like.
We can also use radar to look at the surface of Venus,
which you cannot see because of its very thick atmosphere.
So we've learned a lot about Venus.
I'm not quite sure why we have feedback going on here.
>> Jennifer's just gone to see if somebody can --
>> Dr. Odenwald: And the other partner in the transit of Venus
if of course the Sun, and many of us don't intentionally look at the Sun,
and those times that we do it's usually
because we have a total solar eclipse and we're lucky enough to be
in a location where you can actually see that.
And when you see the Moon in front of the Sun during a total eclipse,
you then see the beautiful corona of the Sun,
which we now know has great connections
with space weather, as we call it.   Transit of Venus looks like this.
This is the 2004 transit, observed telescopically from the ground,
and that's largely what you're going to be seeing this June 5
at 6:03 p.m. when you yourself make the observation using
safety glasses.
I didn't have these glasses available right now
because they're being shipped, and when I get them,
I'll bring about 200 of them here to the Library.
They'll be in the Adams Building Science and Tech Reading Room,
and you can pick up your own personal safe viewing glasses
for the transit.
Your next challenge is to find someplace here on Capitol Hill
where you have a clear view of the Western sky at sunset,
because the transit is going to happen
about two hours before sunset, so it's going to be kind of midway
down the Western sky, and the transit will continue
through sunset and end at midnight.
But of course, you won't be seeing it after sunset.
The cool thing, is, though, we have a number of parties around the world
who are going to be broadcasting the transit on the web.
So soon as you're finished viewing it personally
and getting those photons of light, you can then go online
and see the whole thing, plus narration in three
or four different languages.
The transit happens because the planet Venus gets
between Earth and the Sun.
It does that normally, because the orbit of Venus is inside the orbit
of the Earth, so technically you should have many occurrences
where that happens.
But the problem is that the orbit of Venus is tilted relative
to the Earth, so there are only two places in Earth's orbit
where you're going to have the possibility for transits,
and that's when as you see in this picture,
Venus is at that so-called node point.
If that node point is between the Earth and the Sun,
then you have the opportunity for seeing a transit of Venus.
So that's something about the geometry.
Here is a NASA Satellite -- actually a NOAA Satellite view
of the transit of 2004.
You can see Venus scooting across the lower portion of the image.
That was the nice thing about 2004, is we had a number
of satellites viewing the Sun as part of their research.
So we got these interesting views of the transit in different wavelengths
of light from X-ray through the optical, and that's something
that previous observers have never really had access to.
Here's a close-up of Venus, the sort of disk Venus seen
against the photosphere of the Sun.
When the transit happened back in 2004, the Sun was just coming
down from sunspot maximum.
That means that there were a declining number of sunspots
on the face of the Sun and the Sun was
on its way towards its minimum state,
where there's not a whole lot of activity.
So pictures that you see of the transit of 2004,
you typically will see a face of the Sun that looks kind of bland,
like there's not much going on.
This time, however, we are within a year of sunspot maximum,
so this transit is going to be really quite exciting to watch,
because you'll have this very sharp black disk of Venus
against a very active photosphere with probably many,
many sunspots large and small.
So it'll be kind of artistically a very interesting event.
The geometry is sort of this way, that basically --
here's the 2004 transit as an example.
As viewed from the Earth, the planet Venus moves from Roman number I
to Roman numeral IV along its transit path,
and that takes typically about 5 and a half to 6 hours.
So once the transit starts and we start observing it at 6 o'clock here
in Washington on the 5th, it'll take about 6 hours,
so it'll complete roughly around midnight or a tad after.
And that's why you will sometimes see the transit referred
to as June 5th and 6th, because the ending of the transit happens
like 1 a.m. sort of in the morning of June 6th.
Are we the first?
How far back in time can we go and see people
that have observed the transit?
Probably there is some suggestion from archeological evidence
and inscriptions on tombs, that around the time of Montezuma
when there was a transit in 1520, he may have been able to see it,
because all you have to do is look at the Sun around sunset
when you have the atmosphere kind of blocking a lot of the bright light
from the Sun, and you will be able to see the disk of Venus at sunset.
Any other time and you'll be blinded.
But at sunset, if the transit happens at sunset,
there's enough atmospheric extinction
that you don't need safety glasses and you can actually see it.
In fact, Chinese astronomers routinely observed very large
sunspots on the Sun using just this method.
They wait for sunset or just after sunrise, and they look at the disk
of the Sun to see if there were blemishes.
1631, that was the first transit in sort
of the modern post-Montezuma era, if you will.
It was predicted by Kepler but was not visible in Europe.
So that's a shame, and in 1631 we didn't have a lot
of scientific stations spread around the world,
and not very good communication techniques.
So once Kepler predicts something it takes like months for the word
to get to the other side of the world.
By that time the transit is over.
1639, interesting first transit that is pretty well documented.
Jeremiah Horrocks of England.   He was a minister, church minister.
He was recalculating the previous astronomical tables, and discovered
that people had miscalculated the orbit of Venus by just a little bit.
And when he did it correctly, he found that there should be a transit
of Venus visible from England in 1639.
And sure enough, he got out there and observed this darn thing
with basically projecting the image of the Sun onto a screen
and then watching for the dot.
Unfortunately, he was -- he had sort of things that he had to do
in the church, and so he only got to watch the first hour or two
of the transit, and then he had to go off
to minister to his congregation.
And by the time he came back, it was done.
You know, the frustrating thing is, here's this guy
who has made this prediction and gone out there
and made this discovery of this thing happening,
just like the prediction.
And you would think that in the history of humanity,
he would be given sole credit for this wonderful happenstance -- wow!
It's really him that did this!
Uhn-uhn. It turns out he did the observation, but then,
just because this other person was interested in the Sun, too,
and looking at sunspots, Mr. William Crabtree, three towns over,
observed the thing at exactly the same time.
He was not as well dressed, but it's like this frustrating thing,
and we see this many times in science,
that here's this great person that makes this discovery and you think
that he'd be credited with the whole nine yards.
Nope, there's somebody out there in a little neighborhood that you sort
of have to share the credit -- which is fine.
Everybody likes to share -- we're adults.
So anyway, the reason why transits were so interesting is
that Johannes Kepler, he had constructed mathematically,
a very precise model for the Solar System,
where he knew what the distances between the planets were compared
to the distance of the Earth from the Sun.
Using that as one unit, Mercury was .35 units away from the Sun,
Jupiter was about .69, Earth was 1.0, Mars was 1.6,
Jupiter was 5.2 and so on.
He knew those numbers very precisely.
But until you know the distance between the Earth and the Sun
in kilometers, you don't know how big the whole shebang is.
So that was what people were really anxious to get a handle on,
and until they could do that,
all they could do is basically do a proportionate model
of the Solar System, and really not know how big the whole thing was.
And so it turned out that a Scottish astronomer, Gregory,
and an English astronomer, Halley sometime later on --
Gregory came up with this idea that well, hey, we know the distance
between the Earth and Venus in terms of the scale thing.
It's about .3 in these units.
If we wait for Venus to pass in front of the Sun and measure
that whole process, from two observers in different parts
of the Earth, they can use basically this parallax method to figure
out how far away Venus is from the Earth in miles.
And about 50 years later, Halley essentially, with this idea,
codified it, worked out the rigorous mathematics,
and because he had a reputation, compliments of Halley's Comet --
he was not named after Halley's Comet;
it went the other way, of course.
But he had the international acumen to really pull this off.
Gregory, not so much.
So it became known as Halley's method even though it's the
Halley-Gregory method.
So anyway, here is the run of transits from 1639 to 2004.
We've got basically 122-1/2 years coming up here,
and we've got eight years and 105.5 years.
Those three time scales have to do with the details of the orbit
of the Earth and Venus, and where the nodes are
and all those particulars.
The interesting thing about that eight-year period is
that if you work out where Venus is, every 580 days,
you discover that you can draw a perfect pentagram
within the orbit of the Earth.
So you're often going to see the transit of Venus linked
to pentagrams and pentacles and Satanic kind of things,
because whoa, the numbers work out
and it's a perfect shape in terms of timing.
So anyway, moving on, the 1761 transit, here we start.
Instead of observed by only a couple of people,
this one was observed by 176 people.
So we're starting to get popular here -- including Mikhail Lomonosov,
who was an astronomer in Moscow,
who basically noticed something really interesting about Venus
as it moved on and off the disk of the Sun; that in those moment
as it was making the transition, the whole back side of Venus,
the other part of the black circle of Venus, lit up just a little bit
in terms, like a little luminous arch.
And he interpreted that to mean that Venus had an atmosphere.
And that in fact is 100 percent correct.
So we discovered that Venus has an atmosphere
through the transit of 1761.
Also, there was some considerable but muted public reaction
of the transit, usually as the butt of jokes
in fashionable French newspapers.
But anyway, I won't tell you what the joke is here.
I don't even understand it.
And in fact, that's the interesting thing.
Over the period of 2 or 300 years, humor changes,
and it's like, why was this funny?
What is the sight gag going on in here?
I have no idea.   Anyway, 1769 we have Captain Cook.
By now, French, British and even American astronomers were really
keen on looking at transits in order
to better determine what the distance between Earth and Venus
and therefore the Earth and the Sun was.
So here we have the Cook expedition to Tahiti to set
up a scientific station as far away from Britain as he could get.
Probably a political statement at the time, too,
at the time -- I don't know.
But the idea is you get as far apart as you can so that as viewed
from those two different places, the path of Venus
across the Sun shifts by a measurable amount.
And that shift that you see against the Sun is related geometrically
to how far apart the observers are here.
And then, by just working out a simple proportion,
you then work out what the distance to Venus is.
It's a very clean thing.
Surveyors use that technique on Earth all the time as part
of their tricks of the trade.
So anyway, here's Captain Cook, doing his voyage.
Also, at that time we had many precise measurements made.
Timekeeping was crucial among these observers in far-flung locations,
because the only thing you could do is to time when Venus started
and ended its transit in order to establish what
that cord was on the Sun.
And so they had to somehow coordinate timekeeping
in one location on the Earth with timekeeping in another place.
And in 1769, that was big science and engineering.
That was huge, bringing a clock from one place to another,
and synchronizing them to within literally seconds of accuracy.
Hard thing to do.
The next transit -- well, interesting,
in 1857 there was an interesting article
about when the next transit should happen,
and somehow somebody mangled their interview with the astronomer.
And the newspaper sort of placed a correction --
New York Times placed a correction as to
when the next one would happen, and that was sort
of a definitive correction on the earlier error.
1874, December 8.
Photography was just getting started.
There were huge numbers of photographs
that were taken of this transit.
Congress allocated $75,000 for international expeditions hosted by
and run by American astronomers to go out to these far-flung places
and to make these measurements and to stand toe-to-toe
with the British -- to basically show that yes,
we Americans can do just as competent and accurate astronomy
as anybody else, because we were still proving ourselves
at that point.
Now, $75,000 back then is like what, 2 trillion dollars now?
I don't know what the conversion is, but it's huge.
We're talking tens of millions of dollars, I would think,
in terms of the resources that were expended.
And Congress sort of wrote this check out, and Benjamin Franklin,
sort of was highly supportive of this,
and in fact he promoted an astronomer into the British Journal
of Science, sort of co-sponsored him to publish his work on the transit.
Benjamin Franklin was really bit on this transit,
and he was very influential at this time.
So scientists got $75,000, couple of ships, all the limes they can eat
on the voyage, and off they went.
And so the 1874 transit, rather the transit at that time, they were able
to collect all this information together and come up with a number
of 91 million miles for the distance between the Earth and the Sun,
which is really cool, because the previous number was
like 60 million miles, and the pervious number before
that was 15 million miles.
So now we had a pretty definitive measurement of what
that distance was, and so therefore,
with Kepler's scale model we can now multiply that number
against all these others and figure out,
how many miles is it, really, to Jupiter?
Of course, when it was announced that there would be a transit
in 1882, this met up with some interesting discussion --
not very pleasant.
Proctor was an astronomer and a populizer, and he made the claim,
correctly, that there would be a transit in 1882.
This was not greeted very well.
Let the astronomers gratify their perverted tastes by having transits
in their own houses, but let them understand
that the government will not lend itself to open,
shameless astronomical junket.
You guys had already gotten $75,000 from us, and now what,
you want to get $100,000 this time?   What is this?
How long is this going to keep going?
How long are you going to keep inventing transits
and coming to us for money?   Well, this will be the last time.
Yeah, yeah.   But there were other sort
of perspectives too, from the 1882 transit.
The New York Times and people were op editing about this,
with lavish praise, that this is just such cool stuff, you know.
The simple, everyday person can sort of get out there,
and with smoked glass, look at the transit and realize
that there were a bunch
of scientists elsewhere doing the same thing, and they're coming
up with numbers that tell you how big the universe is.
And they were just sort of harmonizing and resonating
on this whole cosmic connection here going on.
It's really cool to see.
And so 1882, everybody was out there with their smoked glass.
Ten percent of the population went blind, of course,
but this worked out pretty well.   There were also pictures taken.
The pictures that had been taken for the 1874 transit,
really had the right idea.
But the problem was that when they brought these plates back
and started analyzing, they realized that they hadn't properly controlled
for the actual orientation of the photograph
at the time of the observation.
So they couldn't measure where the horizontal plane was in these photos
for each photo that was taken.   And that's huge.
That's a huge problem, because then you don't know really what the
orientation of the Sun is, and you don't know exactly how the position
of Venus on the Sun in one time relates to another time.
So what they did for 1882 is
that they took even more photographic plates,
these glass plates that they developed on site with chemicals,
they scored the bottom of the plate with a tiny channel,
and they filled it with a drop of mercury.
And so when the plate was held perfectly level with the ground,
the mercury would fill the entire channel
and give you an actual line on the photograph.
Simple technology.
It took all of ten seconds to score the plate and put the mercury.
Of course, mercury poisoning was a problem,
but we don't know the graduate students that died
from that little thing there.
Graduate students are sort of the unsung heroes of a lot of things.
You never hear about them, for the most part.
We are legion.
Anyway, of course, the newspapers loved the transit, too,
so they took a lot of liberties.
There was actually an inscription around the disk
of the Sun there about, feeling uncomfortable
that so many people are now looking at me from the Earth,
and I'm feeling embarrassed and all this.
Again, humor doesn't translate too well.
Transit of Venus march, 1883, the year after the transit.
Sousa was commissioned to write a march for the passing of Henry.
He was a physicist, much loved, worked in electromagneticism
and magnets and generators and inductors and things like that.
Well, he died, and so he was a mason, and so Sousa was a mason.
And so he was asked to write, commissioned a march
for the ceremony, the burial of Henry.
So he did, and it's the Transit of Venus march.
Because at the time that Henry was buried, or at the time
of this inauguration, there was an interesting conjunction going
on in the sky that involved Venus.
It would be in the daytime so nobody would see it, but Sousa knew
about it, and of course the astronomers
that were masons also knew about it.   So it was kind of a cosmic thing.
It was still Venus's theme, but now, it was the march.
And let me see if I can play this for you.
Interesting story here.
Myself and Susan Claremont and Loras Schissel were sort of looking
through records of music for things that had to do with Venus,
and we found this unplayed Transit of Venus march.
It was the score written for instruments in 1882 --
not for modern instruments.
So my mission gave Loras money, commissioned him
to transcribe this into modern instruments.
And so he played it with his band, which is well-known in this area.
And so since then it's now become popular for schools
to play the Transit of Venus march.
And here's one that's actually quite amusing:
[ Music ]   >> This goes on for six hours.
[ Music ]   >> But it's cute.
All right, so anyway, if you go to YouTube -- yes, yes, thank you --
YouTube, can play this yourself, and have a great time with it.
I just found it really amusing.
And this wasn't the end of it, either, because there were a number
of other things that came out of that transit as well, music-wise --
the Gallop and all sorts of things.   Not a huge repertoire.
Nobody's going to put these into a book that's going to have more
than maybe 20 pages, but it's kind of fun.
This transit 1882 really captured a lot of peoples' attention.
And if you want to see more about the holdings that Library
of Congress has, you can visit this website,
which is part of the Encyclopedia of Music,
and you can see all the resources that were found as a result.
Really kind of fun.   Things never change.
"The prospect of a Democratic victory is extremely alarming
to Republican politicians, and they become more desperate
as prospects brighten, but it has had no more to do
with the depression of business than with the last total eclipse
of the Sun or with the transit of Venus."
So there. We get all things mixed together
into one sort of interesting plot.
And here's another one, Senator Plumb -- yes, that's a real person.
"You might as well speculate about the next transit of Venus
to guess whether Indian territory will sometime be divided
and made two distinct territorial governments," so forth and so on.
So you know, people use it as a kind of an expression
for at least a period of time.   We don't do that anymore.
That's a shame.
Anyway, so the astronomical unit went from about 5 million miles
to 92.7, thanks to the transits of Venus.
Modern technology lets us do really clever things,
like bounce radar pulses off of planets and asteroids,
which we know distances too in Kepler's model,
and come up with an astronomical unit that's good to half a mile,
which is what NASA needs in order to navigate around the Solar System,
and that's really kind of a cool connection to NASA.
William Harkness at the U.S. Naval Observatory came
up with this sort of famous comment.
"There will be no other transits of Venus till the twenty-first century
of our era has dawned upon the earth,
and the June flowers are blooming in 2004," and so forth.
And that's all true, but nobody said anything about cicadas.
When the transit of Venus did dawn again in 2004, we had cicadas.
Brood 10 reared its head and 2004 will always go
down in our history locally as the year
of the cicadas and transit Venus.
We did -- NASA did some web casts of the 2004 transit.
Over 50 million viewers viewed this thing.
I was in Greece in Athens at the Observatory there,
working with Isabel Hawkins, another astronomer, and we narrated a number
of hours of the transit, coming up with all sorts of anecdotes
and quips and things, and literally pulling it out of thin air
for all this time on the air.
It's like gosh, I can't think of anything funny to say
about this thing anymore.
It also turned out that the European Southern Observatory,
together with another organization in Europe, had the VT-2004 Project.
They had 2,763 participants and a thousand school classes,
and they combined their observations over this global study area,
to come up with an astronomical unit that was good to about 11,000 miles.
This was 5 times higher accuracy than what Harkness
and others did back in 1882.
The adopted value is different from what the students came up with,
by only about the diameter of the Earth.
So that's amazing.
We're going to do this again for 2012,
but instead of having 1,000 classes and 2,700 participants,
we're probably going to have closer to about a million participants
in several thousand different locations.
So what else can you do with a transit?
You can measure it or you can observe it,
so that splits the world into two parties.
And so we do the best we can.   Here's the 2004 transit, seen
by the NASA TRACE Satellite, at least the end of it.
We also have the Swedish Solar Telescope
in the Canary Islands observing the last part of the transit,
the disk of Venus and so forth.
And we have the GOES-12 Satellite, Earth study satellite, in the X-ray.
You can see the disk of Venus passing across the bottom part.
All those bright yellow areas are sunspots and active regions
where we have flaring activity and intense magnetic fields.
And this was a time when the Sun was coming
down from its maximum activity period.
If we do this image again in 2012 in a month, that image is just going
to be completely filled with these yellow-white areas of activity
and flares, and you might even actually have trouble seeing these.
Interesting, if you measure the brightness of the Sun,
the power that it generates in a square meter on the Earth,
which we use for solar energy, every time you have sunspots you get dips
in the light, and that really big dip comes
from a rather large sunspot group.   But if you look at the far right,
you see this very, very tiny little line.
Well, that's the transit of Venus.
That's when Venus entered the disk of the Sun and left,
and you don't even see it compared to the noise
of all these dark sunspots, but you can measure it,
and that's the testament to our science and technology,
that we can measure the brightness of the Sun
and actually see the transit of Venus.
It turns out that that very same technique is used
by NASA's Kepler Satellite, to discover now well
over 2,000 transiting planets around other stars.
Same kind of an idea.
You have a planet that goes in front of the star,
the light from the star dims a little bit, and you can measure just
by knowing the diameter of the star and the diameter of the planet,
or the brightness dip, what the diameter of the planet is.
So that's why we're coming
up with all these Jupiter-sized exoplanets and Earth-sized ones.
We're using exactly this technique, which you can seek
with the transit of Venus.
Here are some other pictures that came
from 2004, interesting pictures.
There's also a beer that was commissioned.
I have three bottles remaining of that brew.
Eight-year-old beer.
I'm not too anxious to sample it, but I'll give it a try,
and then have my stomach pumped, no doubt.
The people in the jet, basically didn't see anything happening
at all, right?
I mean, they're seeing a horizon of the Earth and everything else
down there, and they look up and they see blue skies.
Just our perspective puts the jet in the same area as Venus and the Sun.
Kind of funny.   Then, of course, we're going
to have the usual screaming multitudes with their glasses.
For 2012, we have a little bit of a different transit.
The transit happens on the upper or northern part of the disk of the Sun
that time, and we still have the interest in the first two moments
when Venus goes onto the disk and the last two
when it goes off the disk of the Sun.
And the timing of those things gives you basically what the length
of that cord is, which then allows you to compare
that against the length of the cord measured by another observer.
And then the distance between those two gives you the parallax,
as they call it, which is then related
to how far apart observers are on the Earth, and then you can figure
out what the distance to Venus is pretty easily.
Our particular on details for us, it starts on June 5th, a Tuesday,
at 6:03 p.m. So everybody is in the middle of rush hour traffic.
And it ends at sunset.
So we get to see the first two hours of transit, when Venus goes
from not being on the Sun to then being firmly on the Sun.
The transit ends a little bit after midnight --
actually 1:30 or so a.m. That's why you will see the transit referred
to as June 6th, because it overlaps the two days.
Again, NASA is planning a lot of activities that are going
to surround the transit of Venus.
We've already developed a website over the last year with a lot
of resources, historical and otherwise.
Also, we're going to have a webcast from Hawaii, live webcast,
which will be very exciting, even more capably done
than the first one 8 years ago, because we now know how to do it.
Of course, we now don't have to do it again for another 120 years,
so the learning curve then starts all over the next time around,
because nobody's going to go back and look at how we did it this time.
They're going to create something new.
We have okay, the webcast going on.
That starts a little bit before 6 p.m. our time here in Washington.
So if you go online to this website, you can connect
up with the video stream for this.
And that'll run through the entire transit
into the early hours of the morning.
We know that many museums are planning sleepover events for kids.
Of course, it comes on June 5th,
which is sort of around the time many schools graduate by then,
so it's kind of a different event.
The transit in 2004 was also like that as well,
but we know from that experience that that didn't prevent tens
of thousands, hundreds of thousands of kids streaming to local museums
to have overnight sleepovers to watch that event.
And of course, we're on Facebook and we're
on Twitter, and we are on YouTube.
We have a number of YouTube programs to talk about;
the history of the transit, and those sorts of particulars.
And the map is filling up with locations where you'll be able
to view it firsthand or through museum activities.
Now, of course, there is an app to that.
You can download a free app for timing the transit of Venus,
created by Steven Van Roode,
and basically what you do is you just stand there
and when you see Venus just touching the Sun, you click it,
and when you see it on the other side, you click it as well
and those numbers are going to get recorded and used
in a global measurement of the transit of Venus,
the distance thing again.
So that's where we get our millions of people involved.
We'll at least have millions of people using apps.
Hopefully that will translate into interesting science results.
And of course, if you missed the transit this time, well,
you're kind of out of luck.
The next one is in 2117, so just add 120 years to your current age,
and that's where you'll be.
And add that to your grandchildren's age,
and that's where they'll be, too.
So basically, nobody currently alive will probably be alive
for that transit, either, except maybe children possibly.
Our kids might possibly make it that long,
with a lot of medication and things like that.
So that basically rounds it out.
So if you have any questions, or if you'd just like to chat.
In the back?   >> Where will you be on June 5th?
>> You know, actually, I don't know.   >> Repeat the question.
>> I'm sorry; where am I going to be on June 5th?
First of all, on that Saturday I'm going to be in Boulder,
giving a class on space weather, and then I'm coming back on Sunday.
And then on Monday, we have our daughter, Stacia's graduation,
and so then on Tuesday -- so I'm not traveling to Hawaii in any of this.
There's no alternate universe where I'm going
to Hawaii to be with colleagues.
So I'm probably going to be in the Washington area.
I don't know, I might even be down here at the Library of Congress
with you guys with the glasses.
That's something that I didn't do last time because I was in Greece.
This time, I might just come to the Library here, and we can figure
out what a good place to view it is.
I don't know if the cafeteria would be open at that time.
That might give us a good view.
We'll figure it out; there's time.   A question in the front?
>> Is anybody doing -- using spec [inaudible]?
>> No. it turns out that you know, once upon a time
that was an interesting thing to do from the Earth,
but now that we have spacecraft that have gone there, have cleaner data
on the composition of the Venarian atmosphere, we don't need something
as crude as the transit to give us that.
And also, the atmosphere of Venus at our distance, is just a very,
very thin, little breadth of whatever around the disk of Venus,
I mean, if you think about it.
So you really can't really observe the atmosphere very easily
from the Earth.
You really have to get close up to do that.
Yeah?
>> In terms of the parallax measurement,
is it the time difference depending on the different locations
at the onset and the completion,
or is it the angle difference that is significant?
>> It's -- one is actually related to the other.
Okay, here's how we can do this.
If you were to sort of look at me with one eye closed --
if you're looking at me right now from this side of the auditorium,
you're seeing me against this screen lined up with one
of these columns in one perspective.
Those of you over here are seeing me lined
up with the American flag over here.
That angular distance that you see me shifting back and forth here
in degrees, is related to how far apart you guys are sitting
in rows and meters.
So if you're sitting at the North Pole of the Earth,
and you're sitting at the South Pole of the Earth looking at Venus,
I'm shifting basically up and down, because north and south is this way,
and so on the face of the Sun,
the disk of Venus is shifting up and down this way.
So that distance that you see Venus shift, is measured in degrees,
but that's related to the distance in kilometers that I am
between the North and the South Pole and my perspective.
So it's a matter of basically similar tryings
that you can then work out with the distances between Venus
and the Earth, using that angle information
and the actual physical distance between the baseline positions.
So now, where does the timing come in?
Well, the thing is that it's easy to find the distance between two lines
when you draw them on the Sun.
It's a little bit harder, just looking at the disk of Venus
at one moment and the disk at the other, because you have
to time your measurements to be identical in time.
Otherwise, Venus will be over here or over here.
So if you just measure the lines,
then you've got the complete information,
and you can use multiple measurements of where Venus is
in time and draw a line through that very precisely.
But that means you have to know pretty accurately to within less
than a minute, when the transit started and when it ended,
because that gives you a unique angular distance on that cord.
You compare that angular distance
against some other observer's measurement,
and see that they're different because of this parallax shift.
The cord up here is a little bit bigger in length than the cord
down here, closer to the curve of the Sun.
So you basically use that, and it's all related back to a proportion.
But you have to measure those times very accurately,
because that helps you discriminate the distances
between those two cords.
If you don't do that timing well enough, the cords look
like they're essentially the same length, and the process collapses.
So that's why timing is very important.
And basically all you need from one location is the answer for,
what was the length of the cord that was measured?
You don't need the actual number or the time,
because once you get the angle or distance, that's all you need.
So it's easy to compare one observer's number
against somebody else's number, because you no longer have
to worry about time information.
You're now talking strictly about what the length
of the cord was, and that's all you need.
So it's a much simpler kind of data to work with --
very long answer, short question.
That's how scientists work sometimes.
Yeah?
>> I have a question about the astronomical unit.
That's the distance between Earth and the Sun, right?
>> He had a question about the astronomical unit.
Yes?
>> Since the Sun and the Earth are not in a circular orbit,
do you have some reference for?   >> Exactly right.
The orbits are slightly elliptical,
so the astronomical unit is an established average value
that is used to define that orbit.
It's not exactly the semi-major axis of that ellipse;
it's not the semi-minor axis, but it's a number that you get
that you can then convert into one or the other of those two.
So it's -- you don't have to make multiple measurements
of the Earth-Sun distance to get the math to work out correctly;
you just need this one number, which is the average.
And you can measure an average very precisely from lots of data.
>> Could you explain the astronomical underpinning
as to why the transit is only visible during the Solstice,
and also why it goes from winter to summer?
>> Well, that's -- why is it only during the Solstices,
which is basically December and June,
and why do we have this flipping?
It's all about the timing of Venus and the orbit.
It's a timing issue.
It's nothing really more profound than that,
that you have two nodes defined in the orbit.
Those nodes usually line up with the Solstices, but not always,
because they're rotating,
because the orbits are rotating very slowly in time.
That's why the particular dates change.
Its last transit was on June 6 or June 8; this time it's on June 5.
Other transits will have different dates,
as the orbits change a little bit.
It's where this nodal line is, and that's the important thing,
and then everything else is about when does Venus get
to that nodal point at the same time that Earth is also on that line?
And when you work out what those things are,
then you have basically two places where that can happen,
either in December or in June.
And you also get -- for instance, the 8 -year period is pretty easy
to work out, because the time between Venus being
in the same orientation relative to the Earth and the Sun,
that's called the synodic period, and that's about 580 days.
If you multiply basically 580 days times 5,
and multiply 8 years times 365, you get the same number of days.
So that's why 8 Earth years gives you 5
of these synodic points along the orbit, which is this pentagon thing.
Now, the rotation of that pentagon is then what determines this 115,
120- year period, and that's more complicated to explain.
And I don't really have a good intuitive way
of describing that to you.
The 8-year period is easy; the 120-year, and 105 is hard.
Yeah?
>> Do you know if the National Observatory is doing anything
for it?   >> The U.S. Naval Observatory?
I think Homeland Security has pretty much put the kibosh on anything,
other than viewing for Congress and the Presidents and families.
I can't imagine U.S. Naval Observatory being open
to the public, and I don't think they are, actually.
If anybody here knows more about that.
>> They used to have an open house.   >> I know they did.
>> Is that no longer?   >> I don't think it is.
I think the Homeland Security issue has become just huge,
because it's the Vice President's backyard.
Other questions?
>> Is Air and Space going to have something?
>> Yeah. I think most places around here will have some kind
of a program or viewing, and the amateurs in this area,
amateur astronomers in this area are extremely active.
They got one more shot to get this right, and it's another 105 years.
They got it really right the last time,
but this time, it's the grand deploy.
Plus, I think daisies will be very popular.
That's a subtle comment about Bill Harkness's comment
about daisies blooming in 2004 for the next transit.
Yeah?
>> My question is not about Venus, but I'm from Indonesia.
When I was in Indonesia, when I looked at the moon, I thought,
how did they come up with the moon having a face,
because in Indonesia it looks different.
And when I came here, I looked at the moon and it's full moon,
and I thought, right, I see the eyes,
I see the nose, I see the mouth.
And in Indonesia, I went back to Indonesia, and it's not there.
I don't know whether it's my mind or what.
It's different.   >> Now, correct me if I'm wrong.
Indonesia is -- much of Indonesia, is that not south of the equator?
>> It's right --
>> All right, so you have this problem
with the moon maybe being upside down.
>> Yeah it's really funny.
In Indonesia it's an old woman carrying wood,
nothing with the face at all.
And I thought, is it just me or what?
Nobody ever said anything.
>> Yeah, I've looked at the moon countless times as an astronomer,
and I don't get it, either.
And the only thing I can think of is it must be medication or drugs,
or the quality of the water.   It's got to be something like that.
Because I'm a fairly imaginative person, but I look at the moon
and I basically see -- yeah?   >> For those of us traveling,
what parts of the world will this be visible?
>> Gosh, it's going to be visible anywhere -- anywhere from Japan,
Hawaii, western United States, Eastern United States, Europe.
I think there's only a sliver between Eastern Europe maybe
and India, or whatever, where they don't get to see much of it.
There are many of these maps online you can go to.
But we're pretty good.
Actually, Pacific -- the Atlantic Ocean is a bad area,
because the transit will basically happen
after local sunset, so you won't see it.
You just have to go two more time zones to the east,
and the transit happens after sunset,
and that continues on for 8, 9, 10 hours.
So yeah, we get it this time.
Last time Europe and Asia and everybody else got
to see a really good transit.
>> Oh, so 2004 we couldn't see it here?
>> Let me see...
we saw only I think about the last hour of it or something,
because we were on sort of the other edge.
And then you went to the middle United States,
and they wouldn't see it, because it happened
after sunset or whatever it was.
It's a little bit complicated, but we've worked that out.
You can just go online and see these maps.
If you're in Washington, you're going to be fine.
If you're on the west coast, you'll be fine, too.
If you're in Europe, you won't be quite so fine.
Much better food, though.   Yeah?
>> There is an annual eclipse of the Sun that's kind of a warm effect.
Venus must have a warm effect.   >> That's right.
that's exactly right.   Uh-huh?
>> You said you were [inaudible].   How will we know when they arrive?
>> I think I'm going to be getting the shipment this Friday,
so I would think by sometime earlier next week I'll be able
to bring the glasses in here.
>> We'll have them in the Science and Business Reading Room,
so you can call the Science Reference Desk.
Probably that would be the best to make sure that they're there,
rather than just stopping in next week.
And we have bookmarks out front that have our phone number.
They can contact us directly.   >> How are we doing on time?
>> [Inaudible].   >> Okay. All right.
One more minute to go.
>> Does it matter that longitude for example, here in our time zone,
is there a point as to how far south or north you would be
that would impact directly?
>> Yeah, if you're -- for instance if you are located on the East Coast
of the United States and you go down in longitude too far,
you will be in that zone where you won't be able to see it.
So the zone probably goes into Brazil.
By the time you get that far south,
you'll also be in the embargoed zone.
But if you're on for instance, the West Coast of the United States,
you have to go quite far down through South America's latitude
in order to get into that.
So it's different; depends on where you are.
In fact, at the longitude of Hawaii, you can view the transit all the way
up in Fairbanks and I think all the way
down practically into Antarctica.   It's that huge.
Okay, well, thank you so much for coming.
[ Applause ]
>> As soon as I decide whether I'll be here on the 12th,
I hope to see you, if we can sort of figure out how to coordinate that,
on 6 o'clock June 5th Tuesday,
and you'll have your glasses ready to go.
Thank you.
>> This has been a presentation of the Library of Congress.