WEBVTT

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[dramatic percussion music]

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- HI, WELCOME
TO "NASA LAUNCHPAD."

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I'M YOUR HOST, AUDREY STAPLES.

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QUESTION: WHICH DOESN'T BELONG
IN THIS LIST?

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OCEAN WAVES,
SOUND WAVES,

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MICROWAVES,
SEISMIC WAVES,

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RADIO WAVES,
ELECTROMAGNETIC WAVES.

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YEAH, TRICK QUESTION.

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THEY ALL FIT IN THE LIST,
BECAUSE THEY'RE ALL WAVES.

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OKAY, MAYBE THE IMAGE
OF THE MICROWAVE DOESN'T FIT.

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BUT MICROWAVES,
AS WELL AS RADIO WAVES,

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ARE PART
OF THE ELECTROMAGNETIC SPECTRUM.

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WHY ARE WAVES SO IMPORTANT?

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WELL, SURFING'S PRETTY BORING
WITHOUT THEM.

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AND THINK ABOUT IT:

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NO SOUND WAVES?
NO SOUND.

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NO LIGHT WAVES?

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YOU COULDN'T SEE ANYTHING.

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NO MICROWAVES?

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DON'T WANT TO GO THERE.

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BUT JUST WHAT IS A WAVE ANYWAY?

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WAVES ARE DISTURBANCES

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THAT TRANSFER ENERGY
FROM PLACE TO PLACE.

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MANY WAVES REQUIRE SOMETHING
TO TRAVEL THROUGH.

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WATER WAVES TRAVEL
ALONG THE SURFACE OF WATER,

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AND SOUND WAVES TRAVEL
THROUGH THE AIR.

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WE CAN EVEN MAKE A WAVE
TRAVEL ALONG A ROPE.

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TRY THIS.

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LOOK WHAT HAPPENS WHEN I TIE
THIS ROPE TO THE DOORKNOB

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AND THEN MOVE IT UP AND DOWN
QUICKLY.

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WHATEVER THE WAVE
IS TRAVELING THROUGH

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IS CALLED THE MEDIUM.

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GASES, SUCH AS AIR;

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LIQUIDS, SUCH AS WATER;

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AND SOLIDS, LIKE OUR ROPE,

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CAN ALL ACT AS MEDIUMS.

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ANY WAVE THAT NEEDS A MEDIUM
IS CALLED A MECHANICAL WAVE.

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THE AMAZING THING ABOUT WAVES

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IS THAT ALTHOUGH THEY TRAVEL
THROUGH THE MEDIUM,

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THEY DON'T CARRY THE MEDIUM
WITH THEM.

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SO WHAT CAUSES WAVES?

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SIMPLE: WAVES ARE CREATED
WHEN ANY SOURCE OF ENERGY

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CAUSES A MEDIUM TO VIBRATE,

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OR MOVE BACK AND FORTH
OR UP AND DOWN REPEATEDLY.

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MOVING OBJECTS HAVE ENERGY.

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THAT ENERGY IS TRANSFERRED
TO THE NEAREST MEDIUM,

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AND SUDDENLY YOU HAVE A WAVE.

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THE WAVE WE CREATED
WITH THE ROPE

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IS A TRANSVERSE WAVE,

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THE SAME KIND OF WAVES FOUND
IN THE ELECTROMAGNETIC SPECTRUM.

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AS A TRANSVERSE WAVE
MOVES IN ONE DIRECTION,

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THE PARTICLES OF THE MEDIUM

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MOVE ACROSS THE DIRECTION
OF THE WAVE

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AT A RIGHT ANGLE.

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SOME PARTS OF THE WAVE
ARE HIGH, CALLED CRESTS,

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AND SOME PARTS OF THE WAVE
ARE LOW, CALLED TROUGHS.

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THE MEASURABLE DISTANCE
FROM ONE CREST TO ANOTHER

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IS THE WAVELENGTH.

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LET'S WATCH CANADIAN SPACE
AGENCY ASTRONAUT BOB THIRSK

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ON THE INTERNATIONAL
SPACE STATION

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AS HE DEMOS
A DIFFERENT KIND OF WAVE,

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A LONGITUDINAL WAVE.

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- LET'S LOOK AT THE SPEED
OF A WAVE

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AND HOW TENSION AFFECTS IT.

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SO I'LL PULL THIS SLINKY
ABOUT TEN CENTIMETERS APART--

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NOT VERY TENSE--

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AND RELEASE IT.

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SEE HOW FAST THE WAVE
IS MOVING?

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BRISK BUT NOT TOO FAST.

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LET'S TRY THAT AGAIN.

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HERE WE GO.

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OKAY, NOW LET ME STRETCH IT OUT
A LITTLE BIT MORE

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AND PUT SOME TENSION
ONTO THE SLINKY.

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AND WATCH THE SPEED NOW.

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SEE THE PULSE WAVE MOVE?

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QUITE A BIT FASTER.

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LET'S TRY THAT AGAIN.

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SLOW...

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AND FAST.

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THE TENSION AFFECTS
THE SPEED OF THE WAVE.

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LET'S LOOK AT THE REFLECTION
OF A WAVE.

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I'LL PULL THE SLINKY APART.

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AND WHEN I RELEASE IT
WITH THIS HAND HERE,

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I WANT YOU TO WATCH
HOW THE WAVE TRAVELS DOWN,

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STOPS AT THE REFLECTED--
AT THE FIXED END,

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AND THEN REFLECTS BACK
IN THE OPPOSITE DIRECTION.

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HERE WE GO.

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SEE HOW THAT--HOW IT REFLECTS
BACK AND FORTH?

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TRY IT AGAIN.

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I'LL HOLD THIS HAND FIXED,

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LET GO OF THE SLINKY,

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AND YOU CAN SEE HOW IT REFLECTS
BACK OFF THE FIXED END

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AND BACK TO THE INITIATING END.

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- HOW DID THOSE WAVES COMPARE

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TO THE WAVES WE CREATED
WITH ROPE?

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LONGITUDINAL WAVES
MOVE THE PARTICLES OF THE MEDIUM

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PARALLEL TO THE DIRECTION
THE WAVE IS TRAVELING.

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THE COILS IN THE SPRING
MOVE BACK AND FORTH

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IN THE SAME DIRECTION
AS THE WAVE TRAVELS.

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THE PARTS WHERE THE WAVES
ARE CLOSE TOGETHER

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ARE CALLED COMPRESSIONS.

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THE PARTS WHERE THE COILS
ARE SPREAD OUT

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ARE CALLED RAREFACTIONS.

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AFTER THE WAVE PASSES,
EACH PART OF THE SPRING

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RETURNS TO THE POSITION
WHERE IT STARTED.

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- STANDING WAVES ARE WAVES

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THAT DON'T APPEAR
TO MOVE AT ALL.

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AND IN FACT,
THE NODAL POINT STAYS FIXED.

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LET'S TRY--SEE IF WE CAN GET
A ONE-NODE STANDING WAVE

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GOING HERE.

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YEAH, THERE WE GO.

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THAT ONE'S PRETTY EASY.

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SO THE NODAL POINTS
ARE AT THE FIXED ENDS

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OF THE SLINKY.

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- SURFACE WAVES,
LIKE THOSE THAT OCCUR

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AT THE SURFACE OF THE OCEAN,
WHERE WATER AND AIR MEET,

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ARE COMBINATIONS OF TRANSVERSE
AND LONGITUDINAL WAVES.

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THE WATER MOVES UP AND DOWN,
LIKE OUR ROPE,

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BUT THE WATER
ALSO MOVES BACK AND FORTH

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LIKE THE COILS IN THE SPRING.

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UNLIKE THE COILS, THOUGH,
THE WATER DOES NOT COMPRESS.

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INSTEAD THE UP-AND-DOWN
AND BACK-AND-FORTH MOVEMENTS

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COMBINE TO MAKE THE PARTICLES
OF WATER MOVE IN A CIRCLE,

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CREATING THE CIRCULAR MOTION
OF SURFACE WAVES.

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YOU COULD TRY
THESE SAME DEMONSTRATIONS

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IN YOUR CLASSROOM OR AT HOME

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TO HELP YOU LEARN MORE
ABOUT WAVES,

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BUT WHY WOULD ASTRONAUTS

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ON BOARD THE INTERNATIONAL
SPACE STATION

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NEED TO UNDERSTAND MORE
ABOUT WAVES?

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IN THE MICROGRAVITY ENVIRONMENT
OF THE ISS,

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TINY VIBRATIONS OR DISTURBANCES,

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EVEN THOSE CAUSED
BY CREW EXERCISE,

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CAN UPSET SENSITIVE
SCIENCE EXPERIMENTS.

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SPECIAL SHOCK ABSORBERS,

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SUCH AS THE ACTIVE RACK
ISOLATION SYSTEM,

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ACT AS A BUFFER
BETWEEN THE EXPERIMENT

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AND THE VIBRATIONS.

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OTHER EQUIPMENT
ON BOARD THE ISS

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COLLECTS DATA
AND MEASURES VIBRATIONS

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SO FUTURE HARDWARE DEVELOPERS
CAN DESIGN EQUIPMENT

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TO OPERATE MORE EFFICIENTLY
IN THE MICROGRAVITY LABORATORY.

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NOW, THAT WOULD BE A COOL JOB:

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DESIGNING A SHOCK ABSORBER
USED IN SPACE.

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THAT'S IT FOR NOW.
I'M AUDREY STAPLES.

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CATCH YOU NEXT TIME
ON "NASA LAUNCHPAD."