[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.83,0:00:10.42,Default,,0000,0000,0000,,Have you ever noticed something swimming\Nin your field of vision?
Dialogue: 0,0:00:10.45,0:00:14.06,Default,,0000,0000,0000,,It may look like a tiny worm\Nor a transparent blob,
Dialogue: 0,0:00:14.08,0:00:18.05,Default,,0000,0000,0000,,and whenever you try to get\Na closer look, it disappears,
Dialogue: 0,0:00:18.08,0:00:20.76,Default,,0000,0000,0000,,only to reappear\Nas soon as you shift your glance.
Dialogue: 0,0:00:21.73,0:00:23.79,Default,,0000,0000,0000,,But don't go rinsing out your eyes!
Dialogue: 0,0:00:23.82,0:00:26.39,Default,,0000,0000,0000,,What you are seeing is a common phenomenon
Dialogue: 0,0:00:26.42,0:00:27.45,Default,,0000,0000,0000,,known as a floater.
Dialogue: 0,0:00:28.45,0:00:32.59,Default,,0000,0000,0000,,The scientific name for these objects\Nis Muscae volitantes,
Dialogue: 0,0:00:32.62,0:00:34.76,Default,,0000,0000,0000,,Latin for "flying flies,"
Dialogue: 0,0:00:34.78,0:00:37.91,Default,,0000,0000,0000,,and true to their name,\Nthey can be somewhat annoying.
Dialogue: 0,0:00:37.93,0:00:42.04,Default,,0000,0000,0000,,But they're not actually bugs\Nor any kind of external objects at all.
Dialogue: 0,0:00:42.07,0:00:44.33,Default,,0000,0000,0000,,Rather, they exist inside your eyeball.
Dialogue: 0,0:00:45.21,0:00:48.74,Default,,0000,0000,0000,,Floaters may seem to be alive,\Nsince they move and change shape,
Dialogue: 0,0:00:48.77,0:00:50.01,Default,,0000,0000,0000,,but they are not alive.
Dialogue: 0,0:00:50.83,0:00:54.65,Default,,0000,0000,0000,,Floaters are tiny objects\Nthat cast shadows on the retina,
Dialogue: 0,0:00:54.67,0:00:57.23,Default,,0000,0000,0000,,the light-sensitive tissue\Nat the back of your eye.
Dialogue: 0,0:00:58.08,0:00:59.59,Default,,0000,0000,0000,,They might be bits of tissue,
Dialogue: 0,0:00:59.61,0:01:00.72,Default,,0000,0000,0000,,red blood cells,
Dialogue: 0,0:01:00.75,0:01:02.68,Default,,0000,0000,0000,,or clumps of protein.
Dialogue: 0,0:01:02.70,0:01:06.21,Default,,0000,0000,0000,,And because they're suspended\Nwithin the vitreous humor,
Dialogue: 0,0:01:06.23,0:01:09.28,Default,,0000,0000,0000,,the gel-like liquid\Nthat fills the inside of your eye,
Dialogue: 0,0:01:09.30,0:01:11.58,Default,,0000,0000,0000,,floaters drift along\Nwith your eye movements,
Dialogue: 0,0:01:11.60,0:01:14.33,Default,,0000,0000,0000,,and seem to bounce a little\Nwhen your eye stops.
Dialogue: 0,0:01:15.29,0:01:18.53,Default,,0000,0000,0000,,Floaters may be only\Nbarely distinguishable most of the time.
Dialogue: 0,0:01:19.46,0:01:22.71,Default,,0000,0000,0000,,They become more visible\Nthe closer they are to the retina,
Dialogue: 0,0:01:22.74,0:01:26.22,Default,,0000,0000,0000,,just as holding your hand closer\Nto a table with an overhead light
Dialogue: 0,0:01:26.24,0:01:28.73,Default,,0000,0000,0000,,will result in a more\Nsharply defined shadow.
Dialogue: 0,0:01:29.56,0:01:31.58,Default,,0000,0000,0000,,And floaters are particularly noticeable
Dialogue: 0,0:01:31.60,0:01:34.58,Default,,0000,0000,0000,,when you are looking\Nat a uniform bright surface,
Dialogue: 0,0:01:34.61,0:01:36.22,Default,,0000,0000,0000,,like a blank computer screen,
Dialogue: 0,0:01:36.24,0:01:37.45,Default,,0000,0000,0000,,snow,
Dialogue: 0,0:01:37.47,0:01:38.81,Default,,0000,0000,0000,,or a clear sky,
Dialogue: 0,0:01:38.84,0:01:43.08,Default,,0000,0000,0000,,where the consistency of the background\Nmakes them easier to distinguish.
Dialogue: 0,0:01:43.11,0:01:46.76,Default,,0000,0000,0000,,The brighter the light is,\Nthe more your pupil contracts.
Dialogue: 0,0:01:46.78,0:01:50.70,Default,,0000,0000,0000,,This has an effect similar\Nto replacing a large diffuse light fixture
Dialogue: 0,0:01:50.72,0:01:53.02,Default,,0000,0000,0000,,with a single overhead light bulb,
Dialogue: 0,0:01:53.04,0:01:55.32,Default,,0000,0000,0000,,which also makes\Nthe shadow appear clearer.
Dialogue: 0,0:01:56.19,0:01:59.74,Default,,0000,0000,0000,,There is another visual phenomenon\Nthat looks similar to floaters
Dialogue: 0,0:01:59.77,0:02:01.32,Default,,0000,0000,0000,,but is in fact unrelated.
Dialogue: 0,0:02:02.38,0:02:04.76,Default,,0000,0000,0000,,If you've seen tiny dots of light\Ndarting about
Dialogue: 0,0:02:04.78,0:02:06.98,Default,,0000,0000,0000,,when looking at a bright blue sky,
Dialogue: 0,0:02:07.00,0:02:11.10,Default,,0000,0000,0000,,you've experienced what is known\Nas the blue field entoptic phenomenon.
Dialogue: 0,0:02:12.27,0:02:15.14,Default,,0000,0000,0000,,In some ways,\Nthis is the opposite of seeing floaters.
Dialogue: 0,0:02:15.95,0:02:17.58,Default,,0000,0000,0000,,Here, you are not seeing shadows
Dialogue: 0,0:02:17.60,0:02:21.03,Default,,0000,0000,0000,,but little moving windows\Nletting light through to your retina.
Dialogue: 0,0:02:21.98,0:02:24.80,Default,,0000,0000,0000,,The windows are actually caused\Nby white blood cells
Dialogue: 0,0:02:24.82,0:02:27.89,Default,,0000,0000,0000,,moving through the capillaries\Nalong your retina's surface.
Dialogue: 0,0:02:28.70,0:02:32.75,Default,,0000,0000,0000,,These leukocytes can be so large\Nthat they nearly fill a capillary
Dialogue: 0,0:02:32.78,0:02:35.91,Default,,0000,0000,0000,,causing a plasma space\Nto open up in front of them.
Dialogue: 0,0:02:37.13,0:02:39.14,Default,,0000,0000,0000,,Because the space\Nand the white blood cells
Dialogue: 0,0:02:39.17,0:02:41.70,Default,,0000,0000,0000,,are both more transparent to blue light
Dialogue: 0,0:02:41.72,0:02:44.96,Default,,0000,0000,0000,,than the red blood cells\Nnormally present in capillaries,
Dialogue: 0,0:02:44.98,0:02:48.04,Default,,0000,0000,0000,,we see a moving dot of light\Nwherever this happens,
Dialogue: 0,0:02:48.06,0:02:51.92,Default,,0000,0000,0000,,following the paths of your capillaries\Nand moving in time with your pulse.
Dialogue: 0,0:02:52.83,0:02:54.79,Default,,0000,0000,0000,,Under ideal viewing conditions,
Dialogue: 0,0:02:54.81,0:02:58.91,Default,,0000,0000,0000,,you might even see what looks\Nlike a dark tail following the dot.
Dialogue: 0,0:02:58.94,0:03:02.58,Default,,0000,0000,0000,,This is the red blood cells\Nthat have bunched up behind the leukocyte.
Dialogue: 0,0:03:03.43,0:03:07.68,Default,,0000,0000,0000,,Some science museums have an exhibit\Nwhich consists of a screen of blue light,
Dialogue: 0,0:03:07.70,0:03:12.24,Default,,0000,0000,0000,,allowing you to see these blue sky sprites\Nmuch more clearly than you normally would.
Dialogue: 0,0:03:13.20,0:03:16.20,Default,,0000,0000,0000,,While everybody's eyes experience\Nthese sort of effects,
Dialogue: 0,0:03:16.22,0:03:18.80,Default,,0000,0000,0000,,the number and type vary greatly.
Dialogue: 0,0:03:18.82,0:03:20.32,Default,,0000,0000,0000,,In the case of floaters,
Dialogue: 0,0:03:20.34,0:03:23.49,Default,,0000,0000,0000,,they often go unnoticed,\Nas our brain learns to ignore them.
Dialogue: 0,0:03:24.31,0:03:26.34,Default,,0000,0000,0000,,However, abnormally numerous
Dialogue: 0,0:03:26.36,0:03:29.04,Default,,0000,0000,0000,,or large floaters\Nthat interfere with vision
Dialogue: 0,0:03:29.07,0:03:33.66,Default,,0000,0000,0000,,may be a sign of a more serious condition,\Nrequiring immediate medical treatment.
Dialogue: 0,0:03:34.57,0:03:37.60,Default,,0000,0000,0000,,But the majority of the time\Nentoptic phenomena,
Dialogue: 0,0:03:37.62,0:03:40.21,Default,,0000,0000,0000,,such as floaters and blue sky sprites,
Dialogue: 0,0:03:40.23,0:03:43.62,Default,,0000,0000,0000,,are just a gentle reminder\Nthat what we think we see
Dialogue: 0,0:03:43.65,0:03:46.77,Default,,0000,0000,0000,,depends just as much\Non our biology and minds
Dialogue: 0,0:03:46.79,0:03:49.04,Default,,0000,0000,0000,,as it does on the external world.