Translator: Tijana Mihajlović Reviewer: Leonardo Silva
Host: Please help me welcome Dr. Angela Des Jardins.
(Cheers)
(Applause)
(Laughter)
(Applause)
When I asked a group of Millennials
to tell me the first thing they thought of with the word "eclipse,"
the most common response was, "Vampire book?"
(Laughter)
Today, I'll share my excitement about eclipses
that involve the Sun, the Earth, and the Moon.
Albert Einstein, one of the greatest scientists that ever lived,
said, "I have no special talent.
I am only passionately curious."
Think about what we could do as humankind
if we're all as passionately curious as Einstein.
My own path of curiosity started right here in Bozeman,
as a four-year-old,
marveling over space images in a book.
Today, in my dream job, working for NASA while getting to live in Bozeman,
my passion is to use space to help others find curiosity.
We have a lot of work to do in this area.
For example, last year,
the National Science Foundation found
that one quarter of the American public thinks
that the Sun goes around the Earth.
Statistically, that means two of the people
at your table right now.
(Laughter)
But don't blame them too much
because the Sun going around the Earth is what their intuition tells them.
They just need a good dose of curiosity.
A fun way I like to explain about the Sun and the Earth,
and why total solar eclipses are so cool
is to have the audience dance with me.
But don't be too worried about being embarrassed in this dance
because I'm going to be laughed at way more than you.
We're going to pretend that we're Earth and north is up.
But Earth north is not straight up;
it rotates in an angle of about 23 degrees or about yoga chair pose.
So please stand up.
I'll tell you when you can sit down again.
(Laughter)
You're Earth.
Imagine our lovely blue orb around your middle.
Now, get in kind of a yoga chair pose,
pointing Earth north with your hands,
which is conveniently the way you're all pointing.
(Laughter)
Now, rotate counterclockwise pointing at the same spot
in the corner the entire time.
Ready?
(Laughter)
Great.
Earth rotating counterclockwise
is why the Sun rises in the east and sets in the west.
Now, let's add to the mix.
Stick out your thumb on this side without smacking your neighbor
and pretend it's the brilliant silvery Moon.
At arm's length, your thumb is actually about the size of the Moon in the sky.
The Sun is over there.
Thank you Sun.
We're Earth and the Moon is opposite.
At this point in its four-week cycle,
the Moon is fully lit up from our perspective.
It's full.
Now, orbit your thumb around counterclockwise and switch hands.
About two weeks after the full moon,
the Moon has orbited around to be between the Sun and Earth,
and is completely dark or new from our perspective.
Remembering that the Moon orbits Earth counterclockwise
when you look up at it in the sky
tells you whether it's waxing or waning.
If the Moon is between the Earth and the Sun every new moon,
why don't we have a total solar eclipse every new moon?
To understand the main reason why,
stick out your thumb and block the Sun's light.
Now tilt your arm up a little.
Does your thumb still block the Sun?
No.
It turns out that the orbit of the Moon around the Earth
is tilted by about 5 degrees.
Therefore, it only happens once in a while
that the Moon is perfectly in line at the time of the new moon.
Everybody, do the eclipse move with me.
Ready?
(Laughter)
Great. Have a seat.
(Laughter)
I love being a geek.
(Laughter)
Even if the Moon is perfectly in line at the new moon,
there's still only a total solar eclipse one third of these times.
This is because the orbit of the Moon is not a perfect circle;
it's an ellipse.
So, two thirds of the time,
the Moon is perfectly in line at the new moon.
It's too far away from Earth to completely block out the Sun.
And an eclipse occurs
where there's still a rim of the Sun around the Moon.
It doesn't get dark, chickens don't go to roost,
and our ancestors didn't think the world was ending.
Only when the Moon is perfectly in line at the new moon
and it is close enough to Earth
do we get a total solar eclipse.
Total solar eclipses are so rare.
We haven't had one in the continental US since 1979.
No wonder the common response about eclipse is, "Vampire book."
But in August 2017 we have once-in-a-lifetime opportunity
to observe a total solar eclipse
that stretches across the US from Oregon to South Carolina.
For those of you who've seen a total solar eclipse,
you know: they are hugely impactful events.
Think about the change in technology
since the last total solar eclipse in 1979:
our ability to share curiosity-inspiring images.
In fact, NASA estimates that the 2017 total solar eclipse
will have a profound impact on over 1 billion people worldwide.
Maybe it will even change the percentage of people
who think the Sun goes around the Earth.
(Laughter)
For those of you who haven't seen a total solar eclipse,
how are you going to observe the total solar eclipse of 2017?
From a mountaintop in Grand Teton?
In a plane over the Nebraska Prairie?
From a beach in South Carolina?
And what will you be passionately curious about?
Thank you.
(Applause)