1 00:00:04,801 --> 00:00:10,734 [dramatic percussion music] 2 00:00:18,834 --> 00:00:20,767 - HEY, WELCOME TO "NASA LAUNCHPAD." 3 00:00:20,767 --> 00:00:22,667 I'M YOUR HOST, AUDREY STAPLES. 4 00:00:22,667 --> 00:00:25,067 YOU MIGHT HAVE HEARD THE SAYING THAT OPPOSITES ATTRACT. 5 00:00:25,067 --> 00:00:27,601 AND, YOU KNOW, THAT'S TRUE IN A LOT OF CASES, 6 00:00:27,601 --> 00:00:29,968 LIKE IN SOME BAD ROMANTIC COMEDIES 7 00:00:29,968 --> 00:00:33,434 OR WHEN YOU BRING A PAIR OF MAGNETS CLOSE TO EACH OTHER. 8 00:00:33,434 --> 00:00:36,467 NORTH AND SOUTH POLES WILL SNAP TOGETHER. 9 00:00:36,467 --> 00:00:38,868 BUT SOMETIMES, LIKE WITH WATER, 10 00:00:38,868 --> 00:00:41,567 MOLECULES OF THE SAME SUBSTANCE ATTRACT. 11 00:00:41,567 --> 00:00:42,667 WONDER WHY? 12 00:00:42,667 --> 00:00:44,367 YOU'LL GET A BETTER PICTURE OF WHY 13 00:00:44,367 --> 00:00:46,133 WHEN YOU GET THE CHANCE TO SEE WATER 14 00:00:46,133 --> 00:00:48,167 SOMEPLACE OTHER THAN EARTH, 15 00:00:48,167 --> 00:00:50,334 LIKE ON THE INTERNATIONAL SPACE STATION, 16 00:00:50,334 --> 00:00:52,601 COMMONLY REFERRED TO AS THE ISS, 17 00:00:52,601 --> 00:00:55,400 WHERE WATER APPEARS TO BE NEARLY WEIGHTLESS. 18 00:00:55,400 --> 00:00:58,601 HERE'S CANADIAN SPACE AGENCY ASTRONAUT BOB THIRSK 19 00:00:58,601 --> 00:01:00,000 ON THE ISS 20 00:01:00,000 --> 00:01:03,167 WITH A CLOSER LOOK AT WATER AND THIS SPECIAL PROPERTY. 21 00:01:03,167 --> 00:01:04,667 - THE INTERMOLECULAR FORCES 22 00:01:04,667 --> 00:01:06,834 CAUSE WATER TO BE ATTRACTED TO ITSELF, 23 00:01:06,834 --> 00:01:08,801 WHICH IS CALLED COHESION. 24 00:01:08,801 --> 00:01:12,367 FOR EXAMPLE, HERE ARE TWO SPHERES OF WATER. 25 00:01:12,367 --> 00:01:15,267 WHEN THE SPHERES ARE SEVERAL CENTIMETERS APART, 26 00:01:15,267 --> 00:01:17,667 THERE'S NO ATTRACTIVE FORCES BETWEEN THEM. 27 00:01:17,667 --> 00:01:25,033 BUT WHEN I BRING THEM CLOSE ENOUGH TOGETHER TO ATTRACT, 28 00:01:25,033 --> 00:01:27,834 THEY MERGE THROUGH THEIR ATTRACTIVE FORCES. 29 00:01:27,834 --> 00:01:30,200 - SO YOU PROBABLY ALREADY KNOW 30 00:01:30,200 --> 00:01:32,434 THAT WATER MOLECULES ARE ATTRACTED 31 00:01:32,434 --> 00:01:34,133 TO OTHER WATER MOLECULES, 32 00:01:34,133 --> 00:01:36,133 AND THAT'S CALLED COHESION. 33 00:01:36,133 --> 00:01:38,534 WELL, THESE SAME COHESIVE FORCES 34 00:01:38,534 --> 00:01:41,234 ARE RESPONSIBLE FOR SURFACE TENSION. 35 00:01:41,234 --> 00:01:43,901 SURFACE TENSION IS THE PROPERTY OF A LIQUID 36 00:01:43,901 --> 00:01:47,100 THAT MAKES IT BEAD UP WHEN IT DRIPS ON A SURFACE, 37 00:01:47,100 --> 00:01:49,601 LIKE A LEAF OR YOUR SKIN OR A COIN. 38 00:01:49,601 --> 00:01:52,067 WATER'S SURFACE TENSION IS PRETTY STRONG. 39 00:01:52,067 --> 00:01:53,334 YOU CAN CHECK IT OUT 40 00:01:53,334 --> 00:01:56,033 WITH AN EYEDROPPER OF WATER AND A PENNY. 41 00:01:56,033 --> 00:01:57,534 TAKE A CLOSER LOOK. 42 00:01:57,534 --> 00:02:00,167 SEE WHAT HAPPENS WHEN YOU SQUEEZE THE WATER OUT 43 00:02:00,167 --> 00:02:03,200 ONTO THE PENNY, ONE DROP AT A TIME. 44 00:02:03,200 --> 00:02:04,901 HOW MANY DROPS DO YOU THINK 45 00:02:04,901 --> 00:02:07,400 YOU CAN GENTLY SQUEEZE ONTO THE PENNY 46 00:02:07,400 --> 00:02:10,567 BEFORE THE WATER SPILLS OVER THE SIDE OF THE PENNY? 47 00:02:10,567 --> 00:02:13,033 I BET IT'LL BE MORE THAN YOU EXPECTED. 48 00:02:13,033 --> 00:02:15,934 SURFACE TENSION IS WHAT ALLOWS THE WATER DROPS 49 00:02:15,934 --> 00:02:17,300 TO CLING TOGETHER, 50 00:02:17,300 --> 00:02:20,234 FORMING THAT DOME OR BULGE AT THE TOP. 51 00:02:20,234 --> 00:02:22,234 YOU CAN SEE THAT WATER'S SURFACE TENSION 52 00:02:22,234 --> 00:02:23,767 IS PRETTY STRONG. 53 00:02:23,767 --> 00:02:26,234 YOU CAN ALSO SEE THE COHESION OF THE WATER 54 00:02:26,234 --> 00:02:28,033 AS IT STUCK TO ITSELF. 55 00:02:28,033 --> 00:02:30,334 BUT THE WATER DID SOMETHING ELSE AS WELL: 56 00:02:30,334 --> 00:02:31,934 IT STUCK TO THE PENNY TOO. 57 00:02:31,934 --> 00:02:33,100 WHY WAS THAT? 58 00:02:33,100 --> 00:02:34,767 HERE'S BOB AGAIN TO EXPLAIN 59 00:02:34,767 --> 00:02:36,534 AND TO SHOW HOW IT WORKS IN SPACE. 60 00:02:36,534 --> 00:02:38,834 - INTERMOLECULAR FORCES CAN ALSO CAUSE WATER 61 00:02:38,834 --> 00:02:41,200 TO BE ATTRACTED TO OTHER MATERIALS. 62 00:02:41,200 --> 00:02:43,367 THIS IS CALLED ADHESION. 63 00:02:43,367 --> 00:02:46,968 FOR EXAMPLE, WATER CAN STICK TO A STRAW. 64 00:02:54,267 --> 00:02:58,000 WHEN I MOVE THE STRAW CLOSE TO THE SPHERE, 65 00:02:58,000 --> 00:02:59,868 THE WATER STICKS. 66 00:03:05,801 --> 00:03:07,968 WATER STICKS TO MANY OTHER MATERIALS AS WELL. 67 00:03:07,968 --> 00:03:09,534 THINK ABOUT ALL THE THINGS ON EARTH 68 00:03:09,534 --> 00:03:11,601 THAT YOU SEE LITTLE WATER DROPS ON: 69 00:03:11,601 --> 00:03:14,033 WINDOWS, TREE LEAVES, 70 00:03:14,033 --> 00:03:15,567 EVEN YOUR OWN SKIN. 71 00:03:15,567 --> 00:03:17,801 LET ME SHOW YOU WITH MY HAND. 72 00:03:17,801 --> 00:03:20,734 THE MOLECULES ON MY SKIN WILL PULL HARD ENOUGH 73 00:03:20,734 --> 00:03:22,200 TO MAKE THE WATER STICK. 74 00:03:22,200 --> 00:03:24,000 THE WATER TRIES TO FIND A BALANCE 75 00:03:24,000 --> 00:03:26,868 BETWEEN THE COHESION WITH THE WATER 76 00:03:26,868 --> 00:03:29,834 AND THE ADHESION TO MY HAND. 77 00:03:29,834 --> 00:03:35,100 EVENTUALLY IT SETTLES ON AN UNUSUAL SHAPE 78 00:03:35,100 --> 00:03:38,501 THAT FILLS THE SPACE BETWEEN MY FINGERS. 79 00:03:38,501 --> 00:03:42,968 IF I CONTINUE BY ADDING WATER, 80 00:03:42,968 --> 00:03:46,033 I CAN EVENTUALLY BUILD AN ENTIRE GLOVE OF WATER 81 00:03:46,033 --> 00:03:48,734 THAT WILL STAY FIXED TO MY HAND. 82 00:03:52,167 --> 00:03:56,501 IT STICKS TO MY HAND BY INTERMOLECULAR FORCES. 83 00:03:56,501 --> 00:03:58,467 HOW COOL IS THAT? 84 00:03:58,467 --> 00:04:00,767 - YOU KNOW, IF IT WEREN'T FOR GRAVITY, 85 00:04:00,767 --> 00:04:04,300 SUBTLE FORCES LIKE SURFACE TENSION, COHESION, 86 00:04:04,300 --> 00:04:07,534 AND ADHESION MIGHT HAVE A LOT BIGGER IMPACT 87 00:04:07,534 --> 00:04:09,601 ON OUR EVERYDAY LIVES ON EARTH. 88 00:04:09,601 --> 00:04:12,667 WOULD WE STILL USE BOWLS, SPOONS, AND CUPS? 89 00:04:12,667 --> 00:04:14,367 OR WOULD WE COME UP WITH NEW TOOLS 90 00:04:14,367 --> 00:04:16,200 THAT WOULD MAKE OUR LIVES EASIER? 91 00:04:16,200 --> 00:04:18,400 WELL, THAT'S SOMETHING TO THINK ABOUT 92 00:04:18,400 --> 00:04:22,434 AS WE PLAN TO EXPLORE PLACES LIKE THE MOON, MARS, AND BEYOND. 93 00:04:22,434 --> 00:04:23,534 THAT'S IT FOR NOW. 94 00:04:23,534 --> 00:04:24,901 I'M AUDREY STAPLES, 95 00:04:24,901 --> 00:04:27,167 AND WE'LL CATCH YOU NEXT TIME ON "NASA LAUNCHPAD."