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August 20, 2024 7 mins

On this day in 1977, a NASA rocket launched the Voyager 2 space probe from Cape Canaveral, Florida.

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Speaker 1 (00:00):
This Day in History Class is a production of iHeartRadio.
Hello and Welcome to This Day in History Class, a
show that rockets through history one day at a time.
I'm Gabeluesier, and in this episode we're talking about the
early days of the Voyager space program. NASA's first attempt

(00:23):
to explore the far reaches of our Solar System and beyond.
The day was August twentieth, nineteen seventy seven, a NASA
rocket launched the Voyager two space probe from Cape Canaveral, Florida.
Despite its name, Voyager two was actually the first of

(00:47):
two probes to be launched that year on a so
called Grand Tour of the outer planets. Its twin spacecraft
would launch about two weeks later, on September fifth, and
because that one was scheduled to reach Jueupiter and Saturn
before Voyager two, it was given the designation Voyager one.
Both probes were meant to take advantage of a rare

(01:09):
alignment of the Solar System's outer planets that only occurs
once every one hundred and seventy six years. The alignment
allowed both probes to swing from one planet to the
next using a new technique called a gravity assist. Voyager
one's trajectory put it squarely in the path of Jupiter

(01:30):
and Saturn, while Voyager two's route would allow it to
pay a visit to all four outer planets, Jupiter and Saturn,
as well as Uranus and Neptune. It would take more
than a decade for Voyager two to complete its grand
tour of the outermost planets, but when it finally did,
it became the first and so far the only spacecraft

(01:52):
to have done so. As you've probably gathered, the primary
goal of the Voyager program was to explore the out
Solar System and gather information and photographs of its most
distant and least understood planets. The mission proved remarkably successful
on that front, providing NASA's scientists with detailed measurements and

(02:13):
close up views of each of the four outer planets.
The probes took hundreds of detailed snapshots of everything from
the icy moons of Jupiter to the famous rings of Saturn.
They also discovered evidence of active geysers and volcanoes on
some of the planet's moons, and because of the two
probe approach, they were able to capture planetary changes over time,

(02:37):
such as fluctuations, and the size and shape of Jupiter's
Great Red Spot. In addition, Voyager two made several key
observations in nineteen eighty six, when it became the first
spacecraft to visit the ice giant Uranus. It turned out
that the planet had rings of its own, as well
as ten more moons than was previously thought, and a

(03:00):
curiously tilted magnetic field that was of full fifty five
degrees off the planet's axis. Lastly, Voyager two provided our
closest look yet at the farthest planet in our Solar System.
The probe reached its closest point to Neptune in late
August of nineteen eighty nine, skimming about three thousand miles

(03:21):
above the planet's atmosphere. During that approach, Voyager two identified
five new moons as well as the presence of rings,
confirming that all four of the outer planets have them.
The probe's primary mission was exploration, but they also had
a secondary goal to serve as ambassadors of Earth should

(03:43):
they happen to cross paths with an extraterrestrial life form.
To that end, both Voyager one and Voyager two were
outfitted with a kind of introductory time capsule, a gold
plated copper disc containing a wealth of information about Earth
and its inhabitant. Those identical twelve inch phonograph records were

(04:06):
titled Sounds of Earth, and they featured a collection of
audio recordings that were meant to be representative of human
civilization and the planet as a whole. The selections were
carefully chosen by famous astronomers Carl Sagan and Frank Drake
in cooperation with a panel of historians, artists, folklorists, and musicologists.

(04:28):
The contents they settled on included spoken greetings in fifty
five languages, twelve minutes of nature sounds such as the
noise of wind waves, thunder birds, and other animals, recorded
messages from President Jimmy Carter and other world leaders, and
about ninety minutes of music from a variety of different

(04:49):
eras and cultures. Each record also included over one hundred
analog and coded images, as well as symbolic inscriptions detailing
the probes origins and how to play the disc. To
help with that last part, the record was accompanied by
a cartridge and needle, all of which were sealed up

(05:09):
together in a protective aluminum jacket, which was attached to
the hull of each craft. There's a lot that would
have to go right for an alien to actually find
and play Humanity's message, and of course the chances of
that happening between Earth and Neptune are slim to none.
So it's a good thing that the journey of the
Voyager probes didn't stop at the edge of our Solar System.

(05:33):
In August twenty twelve, Voyager one became the first man
made object to cross the boundary into interstellar space. Then
in November twenty eighteen, Voyager two became the second. Both
probes are now traveling well outside our Solar System, cruising
through empty space in the Milky Way. As of twenty

(05:55):
twenty four, Voyager one is fifteen point two billion miles
from and Voyager two is twelve point seven billion miles away.
Because the probe's power sources are plutonium based, they're actually
still transmitting data back to Earth at the time of recording,
but that won't always be the case. NASA estimates that

(06:16):
both craft have enough fuel and power to keep their
instruments running through at least twenty twenty six, but at
some point after that their transmissions will cease. However, that
still won't be the end of the road for the
Voyager twins. Thanks to their inertia and momentum, they'll keep
right on sailing through the galaxy long after they've run

(06:38):
out of juice. In fact, unless the probes collide with something,
they'll pretty much keep going forever, and in about forty
thousand years they'll make a close approach to another planetary system.
When that happens, there's an off chance that something or
someone will interrupt their journey, and if they do, hopefully

(06:59):
they'll work out out how to play the Golden record
and not think we're too silly for sending it. I'm gay,
Blues Gay, and hopefully you now know a little more
about history today than you did yesterday. If you'd like
to keep up with the show, you can follow us

(07:19):
on Twitter, Facebook, and Instagram at TDI HC Show, and
if you have any comments or suggestions, feel free to
send them my way by writing to this Day at
iHeartMedia dot com. Thanks to kazb Bias for producing the show,
and thanks to you for listening. I'll see you back
here again tomorrow for another day in History Class

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