Transit of Venus Live@Q


Uploaded by QuestaconNSTC on 07.06.2012

Transcript:
Welcome to the Transit of Venus – a tale
of discovery and science. Are we excited?
[Audience say “Yeah” and cheers and applauds]
Thank you.
I’m joined on stage by two guests. The first is
Susannah Helman from the National Library of Australia.
And also Paul Floyd, who’s a local
astronomy educator from here at Canberra.
And we also have a couple of presenters watching via video
conference, who will speak to you all in just a moment.
Firstly, Paul Brunton from the Mitchell Library, part
of the State Library of New South Wales; hi, Paul.
(Paul Brunton) Hi.
Hello. And also Scott and Sarah from
the Museum of New Zealand, that’s
Te Papa Tongarewa over in Wellington; hi Scott, hi Sarah.
(Scott and Sarah) Kia ora (Presenter) Kia ora.
And later we’ll also chat with Carlos Bacigalupo, and he is on the
HMB Endeavour replica as we speak, on their way to Lord Howe Island.
He’s from the Sydney Observatory, and he’s the astronomer
on that ship, so we’ll cross to him soon to say hello.
Now I think to start us all off I will introduce
you again to Paul Floyd. Come on up, Paul.
Paul’s going to tell us what the transit is, and
why it’s so important to us. Thank you, Paul.
Alright. Thank you. OK, the transit of Venus is
basically the planet Venus going in front of the sun.
It’s very rare. It happens only twice every 240 years.
Only ever been seen six times since 1639, so
very, very unusual, and it’s happening next Wednesday,
so if you’re lucky enough, you have prepared
some safe viewing equipment, you can actually watch
it between quarter past eight and quarter to three.
Now the reason why it’s rare is quite interesting
and quite unusual, and I need a volunteer to help
me set up a solar system. Now, Annette, do you want
to choose, or you’re going to be our volunteer?
Sure, who have we got?
Hello, what’s your name? (Andel) Andel.
(Presenter) Andel? (Andel) Yeah.
I’ll get you to hold onto this.
Paul’s going to help you out with that.
(Paul) Alright, now just I’ll hold it for a second.
Now, what I’m going to
get Andel to do, and I’ll just hold it and do some pointing,
what we’ve virtually got is Andel’s going to be the sun, we’ve got a
model of Venus and its orbit, so the green hoop’s Venus’s orbit.
Now, there’s a couple of reasons why the
transit is so rare. First of all it’s got
to do with the difference between Venus
and the Earth zipping around the sun.
Think of Venus as a super fast racing car, and we’re
a fairly fast racing car, but not quite as fast.
So if I’m going to get Andel to hold Venus
in its orbit, nice and straight like that.
And basically if we imagine Venus zipping
around the sun every 225 days, the Earth,
and everyone in the audience who is going
to be the Earth, you’re looking at Venus.
I might actually tilt so we don’t see a transit,
so Venus is not going in front of the sun.
Basically... actually let’s just go back there.
For you and the audience to actually see the transit,
Venus basically has to be in the right spot in its orbit.
Now because we’re zipping around at different
speeds, that only happens every 550 days.
There’s a catch though; Venus’s orbit’s
actually tilted at three degrees.
So most of the time when Venus is actually in a line with
the Earth it’s actually either above or below the sun.
And so that’s why transits are quite rare.
So if you miss the one next week, you’ve
got to wait til 2117 to see a transit. So hopefully we’ll have clear weather.
Alright, thank you Andel.
How about a clap for Andel?
[Presenter and audience applaud]
OK. So back during Cook’s voyage, the voyage of 1769, when they
were observing the transit, what were they hoping to achieve?
Yeah. Well, we take it for granted that
we actually know that the sun is about
150 million kilometres away, what’s called an astronomical unit; basically
back then they didn’t, and they wanted to know how far it was away.
So astronomers were quite clever, and
they worked out that if we can work out
actually how far – or start again – how
quickly Venus is travelling in its orbit,
and we can time that, they can compare the observations between different
points on the Earth’s surface and then work out how far Venus is away, and
then they do a skip and work out how far away the sun is from the earth.
So basically it was an unknown at that time,
working out how far away the sun was.
OK. So they could use those calculations
then to figure how big our solar system is?
Yeah. That’s right, yep.
Excellent. Well we’ve got a couple of other
guests here today who are going to talk
more about the voyage. Let’s thank Paul for
now, and we’ll cross over to Susannah.
[Presenter and audience applaud]
OK, so Susannah Helman is from the National Library of
Australia, and tell us what you’ve got over there about Cook.
OK. Well just recently, just last October, we opened our new Treasures
Gallery, which has material relating to Cook’s three voyages, and so
I’ll just link to a video now that was made last week of our new Treasures
Gallery, and you’ll see Nat Williams, our Director of Exhibitions.
(Nat Williams) Welcome to the National Library of Australia, and
our new Treasures Gallery, which opened about eight months ago.
[Background music begins playing]
In the case behind me are three remarkable documents.
The first is Cook’s Endeavour journal, the central document,
which is 750 odd pages long, his
longhand written account of his voyaging
and his experiences. On the left hand
side here is the additional instructions,
or so called secret instructions which were given to Captain Cook.
Or Lieutenant Cook as he was at the time, by the Admiralty, which
was the primary overarching body that controlled the Navy.
And on the right hand side here we have in a smaller document,
very beautifully handwritten, what’s called Lord Morton’s hints.
Lord Morton was the President of the Royal Society, and he gives
these hints to Cook, Banks, Solander, and others, that voyaged
on the Endeavour; he’s basically saying if you venture beyond
– he was aware that the idea was to go out, see the transit
of Venus, but then voyage further to possibly identify the Great
South Land – if you encounter native peoples, treat them with
kindness, don’t surprise them, by all means engage with them,
but don’t usurp their land without obtaining their permission.
Now Captain Cook and crew, 94 people, are to progress to Tahiti, which
had been discovered by Wallis two years earlier, on the Dolphin,
and go to the point that Wallis had identified, Matavai Bay,
subsequently named by Cook Point Venus,
to observe the transit of Venus.
But having felt that the transit of Venus was possibly not the
success that it might have been, he could have gone home.
I mean his instructions, the secret instructions,
were essentially followed to the letter.
He also had the problem of the difficulty of a
southward passage home at that time of year, so he
decided that he would go via the East Indies, which
meant that he would have to go to the north.
So in doing that he progresses to the west, and finds of course Australia.
Here in the Treasures Gallery, in telling
the story of Cook, we have obviously
behind me this extraordinary painting by Carter of the death of Cook.
We also have the earliest known portrait of Cook in oil, in 1771.
We also have things like his desk,
which was carried from ship to ship, and he would
have written the journal, the Endeavour journal, on.
And artefacts that were connected with it, his fork, his walking
stick, a box of instruments that he used on board ship.
And a variety of paintings which also tell the story,
or some of the moments of the second and third voyages.
Nat makes a really important point I think in there, in terms of how
important the transit of Venus was to Australia, because it’s basically because
of that journey that he took that he was
able to map the east coast of Australia,
which is pretty important to the way that, I guess, we saw it back then.
But Susannah, reading the journal, that’s a pretty personal
thing – I’m not allowed to read my sister’s diary.
What sort of things can we learn about Cook from reading it?
Definitely. Well basically the journal,
which is now just in one volume,
when Cook actually wrote it, it was in quite a number of different
small booklets, like you might have with your exercise books.
Basically the journal shows that he was someone who didn’t use flowery
language, he was very to the point, he was really meticulous, we know
that he was a man of science, and it’s really because of his chart
making, his map making skills that he was chosen for this voyage.
So from this journal we really can see the man, and how he experienced it.
The particular entry for the transit of Venus
day is actually really quite short, which
you would expect from a man who’s been at sea.
He hadn’t had a lot of education, he
had educated himself in science, but he’d
been at sea for years. And I’ll just read
out a little bit, and you’ll get a really
good sense of it, of how he experienced it.
“This day proved as favourable to our purpose as we could wish, not
a cloud 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 disc.”
So you really get a great sense that it was fantastic weather
on the day of the transit of Venus, and equally he’s
just as brief when he says why it all didn't work as well
could be hoped. And I’ll just read out that sentence too.
“We differed from one another in observing the times
of the contacts, much more than could be expected.”
So that was really, here you have in this
page of the journal everything in a nutshell.
OK, so we’re talking about, so they thought that
their observations of the transit was a failure,
and one of the reasons is because –
actually Paul could probably help us out with this one.
There was many people looking at the transit at one time, is that right?
Yep.
And their observations differ. I think he’s referring
to John Gore’s observations in that journal passage?
Yep. They actually had a number, well apparently three
observing sites set up, and essentially they needed to have
the observations accurate to ideally the nearest second,
which was quite remarkable for back then given how poor
time keeping equipment was, so essentially the problem is
that the observations differed by up to 15 or 20 seconds,
and from a scientific point of view, trying to measure the
accuracy, or the distance to the sun, that didn’t work.
Two possible reasons; one was the – well three
– clocks weren’t very good, the second one
was the telescopes weren’t particularly good,
and the other one is the black drop effect.
Ah!
And basically what they had to do for the observations to be accurate, they
actually were looking at when Venus moved
in front of the disc of the sun, and they
had to get that exact second, and what they discovered is the black disc of Venus
seemed to actually merge with the outer blackness of space surrounding the sun.
OK. We’ve got a demonstration that will help everyone to understand kind
of what was going on with this black drop effect.
So what I’m going to get
everybody to do, so here in the
theatre and also anybody watching by
video conference, you can do it at home
too, is everyone put out their hand.
And we’re going to use our thumb and our forefinger, and if you
put that out towards a light source, so perhaps for everyone
here in the theatre put it up towards the screen or the light,
and gradually move your thumb and forefinger close together.
Now what you’ll eventually see is it’ll seem
like they’re touching before they actually are.
So there’s a slight moment there where there’s
something what they call a ligament, so there’s a
slight black, kind of maybe it looks like a shadow,
maybe it just looks like you’ve got a little
extra teardrop coming out of your thumb, and it
makes it appear that it’s touching when it isn’t.
Now what was really important, as Paul said, was
that they knew the precise moment when Venus
touched, or crossed the very edge of the sun,
and also when it left, out on the opposite way.
So that made it really hard for them to see. Thanks.
Yep.
OK. Well Susannah mentioned that the entry in the journal was really short.
Cook’s entry about the transit of Venus, but we have somebody over at the
Mitchell Library, which is part of the State Library in New South Wales,
Paul Brunton, and Paul, I believe you’ve got
some more written observations of Cook.
Can you tell us about what you have in your collection there?
(Paul Brunton) What we have in the collection is the actual
observations of the transit of Venus that Cook took, and I
think you can see that on your screen now, or it’s coming up.
You see how he’s observing the different phases of the
transit as Venus touches the sun, and then touches the rim of the
sun, or seems to touch the rim of the sun, and moves across then.
So we have there, you can see it’s headed Transit of,
then the sign for Venus, Saturday, June the 3rd, 1769.
And on the other page he continues, and you
can just see at the end his signature,
James Cook – very strong signature,
very clear signature. And in a way this
document is the very beginning of the
settlement of Australia, because as we’ve
heard the observation of the transit led
directly to the settlement in Australia.
Although it took a while, and it was by no means certain,
Cook showed his greatness in having followed all his
orders, having observed the transit, and then having sailed
south to see whether there was any Great South Land,
and having concluded that there wasn’t, it was thought that
there had to be a Great South Land, otherwise the world
would tip over, because there was a huge land mass in
the north, there must be a huge land mass in the south.
So he sailed south, he’d shown there was no Great South Land,
he'd proven that New Zealand was two islands, it was not part of a
Great South Land, and he could have gone home.
But he didn’t go home.
He’d finished all his orders, and what made him great was that
he went the extra mile, because he knew now that if he sailed west,
sooner or later he had to meet the eastern extremity of that great
land mass the Dutch had discovered which they called New Holland,
which was basically Western Australia. And that’s what he did.
And so he sails west, charts the east coast of Australia.
That in itself may not have led
to the settlement in Australia, but on board
was Joseph Banks, a young man who was going on
his grand trip around the world, and he was the
man who recommended that the east coast of
Australia be the place where the convicts were sent.
And so that is what happened in 1788.
So there was a number of what if’s of history, if you like. It was by no means
certain they could even observe the transit from Tahiti, because they didn’t know
about Tahiti until just before they needed to leave.
So if Tahiti had not been
discovered in time, they may not have been
able to observe it even in the South Seas.
And finally, this is his sword.
This is what’s called his dress sword. He would have worn this
when he was presented to the King after the Endeavour voyage.
So it was a ceremonial sword that naval people wore on official
occasions, ceremonies, parades, and of course meeting the King.
Well we might take the time now to cross to New Zealand.
So it’s the Museum of New Zealand in Wellington, Ta Papa Tongarewa,
and we have Scott and Sarah, who I think are going to talk to
us a little bit about Cook’s maps. What have you got, Scotty?
(Scott) We do have a bit of stuff about some of Captain
Cook’s maps, because like Susannah – Susannah?
– yes, Susannah said earlier, he had some really good
skills at making maps, he was a very extraordinary
map maker, and we’ve got some of the maps that he
made over 200 years ago, and we can kind of compare
those to the maps that we’ve got today, and we can
see just how accurate and precise those maps were.
But before we do that, it kind of ties in
nicely to the last question from Ballarat,
and we’ve actually got a copy of Abel Tasman’s maps, so we can kind of see
what was missing, and then we can kind of see the gaps that Cook filled in.
So what we’re going to do is we’re going
to have a look at that map to start with.
And you can see from this map.
So you can see the bits of Australia that
were already mapped by Abel Tasman, and
like Paul mentioned, that whole east coast
was missing, and so nothing was known,
they didn’t know how far across the coast was, or how big the land was.
So you can kind of see the gaps that were there,
and Cook went ahead and filled those gaps.
So the first country he got to – and Sarah’s
going to help change these images over for
us – the first country he got to, or the
first land that he came to, was New Zealand.
And that’s a very modern map of New Zealand, so that’s the
shape of New Zealand that we know it to look like today.
You can see two islands and clearly not a huge continental land mass,
so it wasn’t the great southern continent that they were looking for.
But we’ve now got Cook’s map over the top – I’ll just zoom
out a little bit so we can see the whole thing – and you
can see the map that Cook made nearly 250 years ago is
almost as accurate as the current maps that we’ve got today.
So if Sarah can take that one away again very quickly, you can
see very, very precise, and very close to what we see today.
And we’re going to have a look at one more map he made of New Zealand,
before we go over and have a look at his maps of Australia.
So we’ve just gone a little bit closer now on the
north island of New Zealand, so I’ll zoom back in.
And you can see very kind of clearly mapped,
and you probably can’t read the names,
that they’re quite small, but what’s also
very interesting is that a lot of the
names that Captain Cook gave these places
are still the names that we use today.
So for instance you probably can’t see – I
could probably zoom in a little bit more.
And down here you can read Hawke Bay over here, Bay of Plenty of up here.
And we’re going to put a new map up.
And you can see the same shape of the coastline; the same
names still being used today, as it comes into focus.
So the same Bay here, Hawke Bay here, and Bay of Plenty up there.
So very, very accurate, and we’re still using
the same place names that Cook used today.
I understand that you have in your collection
a cannon from the Endeavour, is that right?
Yes, now that’s correct, a cannon that we have in our collection
here in New Zealand, and it was a gift from Australia to Te Papa.
We also have a cannon here in Canberra which
is held at the National Museum of Australia,
and we’ve got a little video.
We went over there last week to have a look at the Cook
collection at the National Museum, and we
had a chat with Michelle Heatherington.
So how about we have a look at that video and
see what they have there in their collection.
(Michelle Heatherington) Hello. I’m Michelle Heatherington.
I’m a Senior Curator at the National Museum
of Australia, and I’m here talking to you about
the Cook collection that the National Museum has.
One of the most beautiful objects, as far as I’m
concerned, in the collection is John Gore’s telescope.
Now this is a telescope that he used to observe the
transit of Venus from the Island of Moorea in 1769.
Now other beautiful things in this case include the plane table frame.
The plane table frame was used during Cook’s voyage to observe
the transit of Venus, and of course was of great use when he was
circumnavigating New Zealand and plotting
the coast, the east coast of Australia.
After Cook had observed the transit of Venus, he had a few
other things he had to do for the Royal Navy and the Royal Society.
Then he decided that he would come home.
They’re getting low on
stores, they’ve been out for three years, and on the night of June
the 11th, disaster – they strike the reef at 11 o’clock at night.
Cook had already gone to bed, and there’s
an account in one of the journals
that he appeared on the deck in his
underwear and began to direct operations.
They had to man the pumps, they began to throw all the heavy
things overboard, including six huge cannon, and they managed
finally to winch themselves off the rock after 23 hours, they put a
bandage under the ship, made out of a sail which they’d filled with sheep
dung and other disgusting material from onboard ship, and then they
limped into coast. It took them nearly a week with a leaking ship.
Now the cannons were known to be there,
because of course Cook plotted their
position, as well as the anchor that he
had to cut loose, because of course it’s
Government property, he’s going to have to go back and get it perhaps.
And so people knew they were there, but
nobody could find it until 199 years later.
So one of the things that made Cook so famous in his
own day were his maps, they really were superb,
and they were being used over a century or more later.
Now in this case there is a beautiful
pair of embroidered map samplers, and in the 18th
Century, girls who went to school were often
required to learn both geography and needlework, and
these two tasks are combined in the map samplers.
One of the students has used a map based
on Cook’s three voyages, and with her
needle she has carefully followed his route across the seas, and I find it a
wonderful object because of course the girls
were not allowed to go to sea at the time.
And here is a girl following in his path, in the only way she can.
So one of the things that Michelle spoke
about was this plane table frame.
It’s actually a collapsible frame,
a wooden frame that you stick around like a
platform, so it becomes a portable
table, and that frame has numbers on it,
so measurements, so that it helps you to make accurate maps. So that was
really important to Cook being able to make those beautiful maps that he did.
We have our astronomer on the HMB Endeavour right now. He’s called in.
We’re going to cross to him now. Carlos, where abouts are you?
(Carlos) Hello. Good afternoon everyone, I’m in the HMB Endeavour.
We’re about five miles off the shore.
We’re pretty much in front of Dee Why right now, so that I
can see still Sydney in the distance. We’re not too far.
Carlos, can you tell us what you’re aiming to achieve on this voyage?
Well actually the Endeavour, right now we are
learning how it use to be, the experience of
sailing in a square rig sailing ship.
It’s a great experience, it’s a very hands-on experience,
so not long ago, about two hours ago, I was
about 20 metres hanging from a mast, while
having helicopters filming us, so it’s been
a very glamorous exit from Sydney Harbour.
You yourself were hanging from the mast of the Endeavour?
That’s right. Me and many other people with the same
experience than I have, which is zero until yesterday.
So you’re on the boat as the official astronomer
for the Sydney Observatory, but it’s pretty
important to know everybody on that boat has
to also do some other work, is that the case?
That’s right. That’s right. This is officially a cargo ship, so
it can’t just take passengers, only a very few number of passengers.
And the rest of us have to act as crew,
so we have to be trained properly
and do crew work, which includes literally
climbing to the top of the mast,
and setting the sails free and these kind of activities, which are a lot of
fun, and a lot more challenging than what they look like from a distance.
So you’re going to be observing the transit
of Venus next week on the 6th of June.
Can you tell us a little bit about that; what
you’ll be doing with those observations?
Yes, we have set up a telescope that’s going to be connected
to a camera, and that’s going to be feeding live over
the internet, and that’s going to become a bit of a backup
plan for any other place in the world that may have
cloudy skies, and would like to take that feed.
That’s organised by the Sydney Observatory and the Maritime
Museum, and that’s like a secondary option for somebody
trying to observe it, and unluckily might not be able to.
And next to that we’re going to have a telescope
set up with a solar filter, and we’re going to
use that for direct observation, we are going to
allow all members that are going to be in the
area to look through a telescope and in a safe
way, and be able to see the planet entering the
disc of the sun, and basically crossing it over
the six hour period that the transit lies.
So you can see the transit of Venus on the internet.
Yes.
So Carlos is involved in a project, they’ll be filming it using a special
solar filter if I heard correctly, and we’re going to talk about viewing the
transit safely in a little while, but it’s a good point for everyone to
know that you can actually observe this over the internet if you need to.
It’s tov. anmm – Australian National Maritime Museum - .gov. au.
We all know not to look directly at the sun, and there are a few
reasons for that, the main one being that you can hurt yourself.
The UV radiation could damage your eyes, it’s oh,
electrical signals going to your brain get interrupted.
[The audience and the Presenter laugh]
Don’t be like the three blind mice.
And we’ve got a quick demonstration now to show you how you
can view the transit of Venus without looking at the sun.
And Paul’s going to run us through that.
Shall we stand up and have a look over here, Paul?
Yeah, sure. What I’ve got set up here is something
that you can rush out; Go to your local shop.
This was bought from a discount retailer for $50, and
basically it’s a telescope to actually project image of the
sun, so you under no circumstances actually look through
the telescope at the sun, and if you’re a school teacher
you’re going to have to make sure that if you set this
up in your school that the telescope is actually always
supervised, because you always have at least one person who
actually tries to look through the telescope.
It’s happened.
Alright. Very easy to make this whole process safe.
You can’t actually see from the camera angle – first of all
there’s no finder scope on the telescope.
Instead, what I’ve got is I’ve got a piece of cardboard which I’ve
put on the front as a sunshade. Now you’re observing
is simple as, once the eye piece is in pointing at the
sun, and with the telescope in the right spot you actually
end up with a lovely image of the disc of the sun.
On the day next week, you actually see Venus travel, and
unlike the charts where it goes across the bottom, because
it’s a refractor telescope and inverts the image, Venus
will actually travel across the top, as seen here.
Now a little tip for you to save you actually looking, or save you from the
need to look through the telescope to find the sun, I’ve actually got at
the front a little hole, and basically what you end up, if we have a look
at the flipchart I’ve got here, there’s
actually two images of the sun.
So this is the hole you’re talking about here, you put in the cardboard?
Yep, uh-huh.
And that reflects, so that’s what this blurry patch is?
Yep. So with the real sun, it will actually be a nice sharp dot.
So basically you can actually look for that dot on your white
piece of paper, and that’ll show you that you’ve got the telescope
in the right spot, and then it’s a case of just wiggling the
telescope around until you see the proper image, or the disc of the sun.
And the transit will be very easily visible as a black dot
going across – I should say, sorry, a black disc, a tiny little
black disc going across from one side to the other of the sun.
I’m going to have to wrap everything up.
I’d like to say thank you to everybody for watching today, the
schools here in our live audience, those joining us
by video conference, thank you for your wonderful
questions; everyone watching on the live internet
stream, thank you for tuning in. I’d also like to
take the time to thank our guests, Susannah from the
National Library. Yeah, let’s give them a hand.
[Presenter and the audience applaud]
Michelle at the National Museum; The Mitchell Library, Paul
Brunton, thank you so much; Scott and Sarah from Te Papa.
[Presenter and the audience applaud]
Also thank you to Carlos – he can’t hear us right now, but Carlos
from the Sydney Observatory and the National Maritime Museum.
[Audience applauds]
Thank you. And don’t forget you can tune into our other
Live@Q events by watching our live stream, you can
also find out what events are coming up by having a look
at our website, and that’s www.questacon.edu.au/live.
And if you’ve got any questions from
today’s event that we didn’t get a chance
to answer, please send us an email. Again, that’s liveatquestacon.edu.au,
and we’ll try our best to get them to the
people who know the answers, or we’ll
have a bash at them ourselves as well. So thank you all for coming along.
Before you all leave, everybody here in the audience, we have some
gifts for you, and there’s somebody at the front door – Phil – Phil
Hoare’s written a book about the transit, so if you get a chance
to chat with him, please do that, and he’ll hand you some posters.
Everybody else, thank you so much again for
watching, and give yourselves a clap and wave.