1 00:00:19,986 --> 00:00:23,690 DEAN: HEY THERE STAR GAZERS. 2 00:00:23,790 --> 00:00:26,526 I'M DEAN REGAS, ASTRONOMER FOR THE CINCINNATI OBSERVATORY. 3 00:00:26,626 --> 00:00:28,695 JAMES: AND I'M JAMES ALBURY, DIRECTOR OF THE KIKA 4 00:00:28,795 --> 00:00:31,197 SILVA PLA PLANETARIUM IN GAINESVILLE, FLORIDA. 5 00:00:31,297 --> 00:00:33,767 WE'RE HERE TO HELP YOU FIND YOUR WAY AROUND THE SKY TONIGHT. 6 00:00:33,867 --> 00:00:36,970 DEAN: THE WINTER SOLSTICE IS THURSDAY DECEMBER 21ST 7 00:00:37,070 --> 00:00:40,006 AND SUN WORSHIPPERS CAN FINALLY REJOICE! 8 00:00:40,106 --> 00:00:44,444 THIS IS THE TIME WHEN THE NORTHERN HEMISPHERE EXPERIENCES THE SHORTEST DAYS AND LONGEST 9 00:00:44,544 --> 00:00:45,445 NIGHTS. 10 00:00:45,545 --> 00:00:46,846 JAMES: WAIT A SECOND, REJOICE? 11 00:00:46,946 --> 00:00:48,114 ON THE SHORTEST DAY? 12 00:00:48,214 --> 00:00:49,616 WHAT'S TO CELEBRATE? 13 00:00:49,716 --> 00:00:50,850 SOUND LIKE LOTS OF DARKNESS. 14 00:00:50,950 --> 00:00:53,753 DEAN: WELL, EVERY DAY AFTER DECEMBER 21ST, THE SUN 15 00:00:53,853 --> 00:00:57,223 WILL GET HIGHER IN THE SKY AND STAY UP LONGER ABOVE THE HORIZON. 16 00:00:57,323 --> 00:01:00,827 THE SUN WILL STOP ITS SOUTHWARD MIGRATION AND START HEADING NORTH AGAIN. 17 00:01:00,927 --> 00:01:03,229 JAMES: I WISH IT WOULD HURRY UP ALREADY, IT'S FREEZING 18 00:01:03,329 --> 00:01:04,431 OUT HERE! 19 00:01:04,531 --> 00:01:06,499 DEAN: LET'S SHOW YOU THE REASON FOR THE SEASONS 20 00:01:06,599 --> 00:01:09,269 JAMES: THE CHANGING SEASONS ARE CAUSED BY ONE THING 21 00:01:09,369 --> 00:01:12,439 - THE 23 AND A HALF DEGREE TILT OF THE EARTH. 22 00:01:12,539 --> 00:01:16,443 AS OUR PLANET ROTATES DAILY ON ITS AXIS, WE ALSO REVOLVE AROUND THE SUN. 23 00:01:16,543 --> 00:01:21,581 BUT OUR ROTATIONAL AXIS IS TILTED COMPARED TO OUR ORBIT AROUND THE SUN, AND WE ALWAYS 24 00:01:21,681 --> 00:01:22,949 KEEP THIS SLANTED VIEW. 25 00:01:23,049 --> 00:01:25,452 DEAN: WHEN WE, IN THE NORTHERN HEMISPHERE, ARE TILTED 26 00:01:25,552 --> 00:01:29,823 MOST DIRECTLY TOWARD THE SUN WE SOAK UP SOLAR ENERGY TO THE MAX. 27 00:01:29,923 --> 00:01:33,793 THAT DAY IS CALLED THE SUMMER SOLSTICE AND IT OCCURRED ON JUNE 21ST THIS YEAR. 28 00:01:33,893 --> 00:01:38,798 AT THIS POINT THE SUN'S RAYS SHINE MOST DIRECTLY ON THE NORTHERN HEMISPHERE. 29 00:01:38,898 --> 00:01:42,168 WE GET MORE ENERGY PER SQUARE INCH, AND THUS IT'S HOTTER. 30 00:01:42,268 --> 00:01:44,771 JAMES: NOW THE OPPOSITE OCCURS WHEN THE EARTH SWINGS 31 00:01:44,871 --> 00:01:46,739 AROUND TO THE OPPOSITE SIDE OF THE SUN. 32 00:01:46,840 --> 00:01:50,376 HERE, WE, IN THE NORTHERN HEMISPHERE, ARE TILTED AWAY FROM THE SUN. 33 00:01:50,477 --> 00:01:54,781 THE SUN'S RAYS FEEBLY STRIKE US AT A LOW ANGLE SPREADING OUT THE SAME ENERGY OVER 34 00:01:54,881 --> 00:01:56,216 A LARGER AREA. 35 00:01:56,316 --> 00:01:58,852 EACH SQUARE INCH GETS A LOT LESS ENERGY THAN IN SUMMER. 36 00:01:58,952 --> 00:02:02,689 WE CALL THIS THE WINTER SOLSTICE AND THAT OCCURS ON DECEMBER 21ST THIS YEAR. 37 00:02:02,789 --> 00:02:06,059 DEAN: THE SUN'S OUTPUT IS THE SAME ALL YEAR-ROUND. 38 00:02:06,159 --> 00:02:10,396 BUT THE DIFFERENCE IN OUR SEASONS IS HOW MUCH OF THAT ENERGY WE SOAK UP. 39 00:02:10,497 --> 00:02:14,467 IT HAS NOTHING TO DO WITH HOW CLOSE OR FAR WE ARE FROM THE SUN. 40 00:02:14,567 --> 00:02:19,405 WE'RE CLOSEST TO THE SUN EVERY YEAR IN JANUARY AND FARTHEST FROM THE SUN IN JULY. 41 00:02:19,506 --> 00:02:22,075 SO THE DISTANCE DOESN T CAUSE THE DIFFERENCE IN THE SEASONS 42 00:02:22,175 --> 00:02:24,544 HEY JAMES, ARE YOU STAYING COOL? 43 00:02:24,644 --> 00:02:26,079 JAMES: THE SUN 44 00:02:26,179 --> 00:02:27,180 IS BLASTING OFF MY HAIR! 45 00:02:27,280 --> 00:02:29,082 DEAN: OH YOU'RE DOING GREAT. 46 00:02:29,182 --> 00:02:33,019 NOW LET'S SEE HOW OUR TILT AFFECTS THE VIEW FROM DOWN ON EARTH. 47 00:02:33,119 --> 00:02:34,988 DEAN: SORRY ABOUT YOUR HAIR. 48 00:02:35,088 --> 00:02:36,222 JAMES: IT'S OKAY. 49 00:02:36,322 --> 00:02:37,223 IT'LL GROW BACK. 50 00:02:37,323 --> 00:02:38,424 DEAN: HA! 51 00:02:38,525 --> 00:02:40,627 JAMES: ANYWAY, WE HAVE OUR SKIES SET TO DECEMBER 52 00:02:40,727 --> 00:02:43,229 21ST JUST BEFORE SUNRISE. 53 00:02:43,329 --> 00:02:48,201 LET'S TRACE THE PATH THAT THE SUN TAKES ACROSS THE SKY ON THIS, THE SHORTEST DAY OF THE YEAR. 54 00:02:48,301 --> 00:02:52,138 THE SUN WILL RISE SOUTH OF EAST, AND REACH ITS HIGHEST POINT IN THE SOUTHERN SKY 55 00:02:52,238 --> 00:02:53,339 AROUND NOON. 56 00:02:53,439 --> 00:02:55,241 THEN THE SUN WILL SET SOUTH OF WEST. 57 00:02:55,341 --> 00:02:58,344 DEAN: FOR MOST OF THE COUNTRY YOU'LL GET ABOUT 9-10 58 00:02:58,444 --> 00:03:00,180 HOURS OF DAYLIGHT ON THIS DAY. 59 00:03:00,280 --> 00:03:03,683 THAT ALSO MEANS YOU'LL GET 14-15 HOURS OF DARKNESS! 60 00:03:03,783 --> 00:03:07,020 JAMES: LET'S COMPARE THIS TO THE SPRING EQUINOX - NEXT 61 00:03:07,120 --> 00:03:09,088 YEAR IT WILL BE ON MARCH 20TH. 62 00:03:09,189 --> 00:03:12,492 NOW LET'S TRACE THE PATHWAY THAT THE SUN TAKES ON THIS DAY. 63 00:03:12,592 --> 00:03:14,494 THE SUN WILL RISE DUE EAST 64 00:03:14,594 --> 00:03:16,329 REACH ITS HIGHEST POINT ABOVE THE SOUTHERN HORIZON 65 00:03:16,429 --> 00:03:18,298 AND THEN SET DUE WEST. 66 00:03:18,398 --> 00:03:20,800 DEAN: NOTICE HOW THE SUN WENT HIGHER IN THE SKY 67 00:03:20,900 --> 00:03:22,035 THAN IT DID IN DECEMBER. 68 00:03:22,135 --> 00:03:24,871 THE HIGHER THE SUN, THE MORE DIRECT ENERGY WE GET. 69 00:03:24,971 --> 00:03:27,106 JAMES: AND LOOK AT HOW MUCH LONGER THE SUN WAS IN 70 00:03:27,207 --> 00:03:28,208 THE SKY! 71 00:03:28,308 --> 00:03:30,610 12 HOURS OF DAYLIGHT, AND 12 HOURS OF DARKNESS. 72 00:03:30,710 --> 00:03:31,611 EQUAL DAY, EQUAL NIGHT. 73 00:03:31,711 --> 00:03:33,947 THATS WHY THEY CALL IT THE EQUINOX. 74 00:03:34,047 --> 00:03:36,482 DEAN: WHAT ABOUT THE SUMMER SOLSTICE? 75 00:03:36,583 --> 00:03:42,388 NOW OUR SKY IS SET TO JUNE 21ST, AND WE CAN WATCH THE SUN RISE NORTH OF EAST 76 00:03:42,488 --> 00:03:44,090 GO VERY HIGH IN THE SOUTH 77 00:03:44,190 --> 00:03:45,458 AND SET NORTH OF WEST. 78 00:03:45,558 --> 00:03:48,027 JAMES: THE SUN WENT HIGHER STILL IN THE SKY. 79 00:03:48,127 --> 00:03:53,700 AND THE HOURS OF DAYLIGHT REACH A WHOPPING 14-15 HOURS FOR MOST OF THE U.S WITH ONLY 80 00:03:53,800 --> 00:03:55,201 9-10 HOURS OF DARKNESS. 81 00:03:55,301 --> 00:03:57,870 DEAN: AND ALL OF THIS IS CAUSED BY THE 23 AND 82 00:03:57,971 --> 00:03:59,939 A HALF DEGREE TILT OF THE EARTH. 83 00:04:00,039 --> 00:04:04,110 DEAN: SO ON DECEMBER 21ST WATCH THIS EXTREME SOUTHERLY 84 00:04:04,210 --> 00:04:05,378 SUNSET. 85 00:04:05,478 --> 00:04:06,946 JAMES: AND IN SIX MORE MONTHS IT WILL REACH THE OTHER 86 00:04:07,046 --> 00:04:10,717 EXTREME: NORTHERNMOST SUNSET ON THE SUMMER SOLSTICE ON JUNE 21ST. 87 00:04:10,817 --> 00:04:13,586 DEAN: SOAK UP THE SOLSTICE SUN - BECAUSE THE LONGER 88 00:04:13,686 --> 00:04:16,656 DAYS ARE RETURNING AND SUMMER IS COMING SLOWLY 89 00:04:16,756 --> 00:04:20,756 BOTH: KEEP LOOKING UP!