What if everything you know is only your imagination?
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00:00 (music)
00:11 If a tree falls in the forest,
00:13 and no one is around to hear it,
00:16 does it make a sound?
00:18 According to quantum theorists,
00:21 that tree might not even exist
00:23 until it's observed.
00:26 So is our world just an illusion?
00:31 Why do some physicists believe that
00:34 physical matter isn't real?
00:37 What scientific experiments
00:39 have changed our view of reality?
00:43 And could everything we see
00:46 just be a hallucination?
00:49 This is WHAT IF,
00:51 and here's what would happen
00:52 if the world is only your illusion.
00:58 The great philosopher René Descartes
01:01 came to the profound conclusion that,
01:03 "I think, therefore I am."
01:06 He was searching for a universal truth
01:08 that couldn't be disputed.
01:10 And the act of thinking was
01:12 undeniable proof of his existence.
01:16 Yet our understanding of existence
01:18 and reality are still evolving.
01:21 In the worlds of quantum physics
01:23 and neuroscience,
01:25 there are different theories about
01:27 what reality is.
01:30 So what is reality?
01:33 If we dive deep into the quantum realm,
01:37 matter is made up of subatomic particles.
01:40 These particles,
01:41 including protons, neutrons, and electrons,
01:44 are in a state of flux
01:46 until they're observed.
01:48 In fact, at the quantum level,
01:50 they may not even look like particles at all.
01:53 You could think of them
01:54 as a cloud of probabilities.
01:57 This concept is known as superposition,
01:59 meaning a particle exists
02:01 in several possible positions
02:03 until they are measured.
02:06 The idea of superposition
02:08 was famously observed
02:09 in the double-slit experiment
02:11 by physicist Thomas Young in 1801.
02:15 When we shine a beam of light
02:16 through one slit,
02:18 it produces a predictable line of light.
02:20 But when another slit is added,
02:23 something kind of spooky happens.
02:26 Instead of two lines of light,
02:28 we see several.
02:30 The photons seem to act like a wave,
02:33 as if they were rippling through the slits
02:35 and bouncing off each other
02:37 in different directions.
02:39 This interference pattern
02:40 led scientists to believe that
02:42 matter could act as both particles and waves.
02:47 That was a profound idea
02:49 that changed the world of physics forever.
02:52 So if things only exist
02:55 when they're observed,
02:57 would black holes still exist
02:59 if we hadn't measured their X-rays?
03:02 Some physicists, like Max Tegmark,
03:04 believe that black holes
03:06 and everything we perceive to be real
03:08 is simply mathematical information.
03:11 This idea is known as information realism.
03:16 In the world of philosophy,
03:18 this idea of reality
03:19 being a product of our observation
03:22 is known as phenomenalism.
03:24 It states that anything we experience
03:27 is simply sensory data in our minds,
03:30 as if life itself is virtual reality,
03:34 without the silly glasses.
03:36 If scientists were able to send signals
03:39 to a living brain in a vat,
03:41 simulating all the senses,
03:43 could we trick the brain
03:44 to believe it's in a human body somewhere
03:47 and experiencing reality?
03:49 Maybe we could reprogram our ideas
03:52 at the neural level.
03:53 Just imagine being able to fly
03:55 anywhere you want,
03:57 drive fancy cars,
03:58 dodge bullets,
03:59 and live forever.
04:01 Your pleasure,
04:02 your achievements,
04:03 and your level of success
04:05 would only be limited
04:06 by your ability to imagine them.
04:09 Some cognitive neuroscientists,
04:11 including Professor Anil Seth,
04:13 suggest that our brains
04:15 are hallucinating reality all the time.
04:18 Have you ever had a dream
04:18 that felt so real
04:20 that you jolted awake,
04:21 feeling disoriented?
04:23 Like that one night
04:24 when I thought I was stuck
04:25 in a "How to Survive" episode.
04:27 Eugh.
04:29 Well, our nightmares
04:31 and our perceptions of reality
04:33 are both processed
04:34 in our brain's visual cortex.
04:37 This is why it can be hard
04:38 to tell the difference between them,
04:41 even though we can't exactly be sure
04:43 what is real.
04:45 With rapid advancements
04:46 in the world of physics and neuroscience,
04:49 we're getting closer to understanding
04:51 the complexities of reality.
04:54 Maybe we'll crack the code someday.
04:57 Speaking of coding,
04:58 could it be possible
04:59 that we're just characters
05:01 in some sort of computer simulation?
05:04 I mean, video game graphics
05:06 are looking pretty real these days.
05:09 On that note,
05:10 computer,
05:11 load "What If" sequence.
05:14 "Okay, Peter,
05:16 that's a story
05:18 for another
05:19 What If."
05:21 ♪♪
05:29 (upbeat music)