The Andromeda Paradox - When is "Now"? [11:09]

--> YouTube-Generated Transcript <--
0:00 · recalibrate okay synchronization in
0:02 · three
0:03 · two one synchronization completely when
0:06 · is now arya and i now both agree on when
0:10 · now is but what about you and me as i'm
0:13 · filming this
0:14 · episode my present is technically your
0:16 · past and your present moment
0:18 · is technically in my future if i was
0:21 · there next to you
0:23 · right now we'd of course both agree
0:26 · on what now is don't don't touch me and
0:28 · it would be after some excruciatingly
0:30 · painful
0:31 · small talk i'm bringing up these
0:32 · differences because my question for you
0:34 · today is
0:35 · does the universe at large have a now
0:40 · okay nothing or is the present moment
0:42 · just a matter
0:43 · of perception now okay let's recalibrate
0:47 · again jesus
0:49 · now entering the facility in 1989 the
0:53 · legendary physicist robert penrose
0:55 · presented a paradox to the public
0:58 · he said consider two nerds very
1:00 · interested in the goings ons in the
1:02 · galaxy nearest our own
1:04 · andromeda and one day these two nerds
1:06 · are walking past each other on the
1:08 · street
1:08 · and they say hello nerd friend i would
1:10 · like to query you as to what is
1:11 · happening
1:12 · right now in the present of andromeda if
1:14 · they had amazing telescopes and didn't
1:16 · have to wait 2.5 million years for the
1:18 · light information to get to them
1:19 · the moving nerd looks at andromeda and
1:23 · says
1:24 · hark stationary brethren i see aliens
1:27 · and their elder councils debating
1:29 · whether or not to invade earth right now
1:31 · who voice but
1:34 · the stationary nerd looks at andromeda
1:36 · and says
1:37 · nary you fool they have already
1:40 · deliberated and their alien fleet is
1:42 · on the way right now to shoot laser
1:44 · beams at our faces
1:46 · the paradox here is that it is
1:48 · theoretically possible
1:49 · for these two nerds to disagree for one
1:51 · nerd to apparently see into the
1:54 · future of the other but how can two
1:57 · simultaneous observations of the present
1:59 · be different
2:01 · well to explain that i need to get
2:04 · changed arya
2:05 · activate carl sagan mode
2:09 · how should we define now how do we
2:12 · suss out what is truly simultaneous well
2:15 · to figure that out from scratch we must
2:17 · first consider the universe not just at
2:19 · one time
2:20 · but at all times i didn't have a
2:22 · turtleneck shut up suppose
2:24 · that we have a camera a camera of the
2:26 · imagination as carl
2:28 · might have and this camera allows us to
2:30 · magically take a
2:31 · snapshot of the entire universe inside
2:34 · of this snapshot in all of
2:36 · three-dimensional space
2:38 · everything should be simultaneous for
2:40 · example me
2:41 · talking to you a student on the other
2:43 · side of the world doing their homework
2:45 · and
2:45 · blurpon from the artemis cluster who's a
2:47 · good friend of mine hashing grebos
2:49 · all day like he usually does they are
2:52 · delicious
2:53 · now if we were to keep taking snapshots
2:56 · eventually would have this
2:57 · abstracted view of all of space and time
3:00 · that we could
3:01 · look at and piece together now many
3:03 · science communicators call this the
3:05 · universal
3:06 · loaf of space-time but that sounds weird
3:08 · and stupid it makes you think of bread
3:10 · i'm hungry you shouldn't be eating as
3:11 · many carbs as you are shut up
3:13 · i'm going to call this totally time
3:16 · every moment that the universe has had
3:19 · is having
3:21 · or will have in this higher dimensional
3:24 · view of t'tala time
3:25 · all time and all events really do exist
3:29 · there's a snapshot where everything is
3:30 · simultaneous for you your present
3:32 · but the past here isn't just a memory
3:35 · and the future
3:36 · isn't uncertain it's all there every
3:39 · single point in time
3:40 · equally as valid as your present it all
3:43 · happens now you might be thinking then
3:45 · if this eternalist view of the universe
3:47 · is true
3:48 · why do all slices as we define them have
3:51 · to look like this
3:52 · why doesn't a snapshot of the universe
3:54 · look like this or
3:55 · even this well that's a good question
3:58 · deactivate carl sagan mode different
4:02 · nows is the very heart of the andromeda
4:05 · paradox a paradox that may be impervious
4:08 · to common sense
4:09 · but not to einstein's theory of
4:12 · relativity oh come on
4:14 · what is what is going on with you today
4:19 · fun fact the andromeda galaxy is on a
4:21 · collision course with the milky way it's
4:24 · a fun fact because that's more than four
4:25 · billion years out and you are definitely
4:27 · not going to make it but whether we're
4:29 · here or not the milky way and andromeda
4:31 · are going to crash together however when
4:34 · this happens it's not going to be the
4:36 · cosmic calamity that you may expect you
4:38 · see space is big
4:40 · it's vast it's bigger than fast we don't
4:42 · have words to describe
4:43 · just how big space is and how large the
4:46 · distance between
4:47 · individual stars are so when you have
4:50 · andromeda with literally trillions of
4:52 · stars moving at 100 kilometers per
4:54 · second towards the milky way when they
4:56 · finally interact
4:57 · there's unlikely to be a single solar
5:01 · collision not one if we were still
5:04 · around
5:04 · in the solar system we probably wouldn't
5:06 · even notice this event
5:08 · happening as a wise man once said
5:12 · whoa now as we explained in our episode
5:17 · about the spaceships paradox
5:18 · how you move through space
5:20 · relativistically speaking can affect how
5:22 · you move
5:23 · through time more specifically if you
5:25 · move really fast through space approach
5:28 · the speed of light
5:29 · you move less in time this
5:32 · fact brings us back to our view of total
5:35 · time
5:35 · and now we should track our two
5:37 · andromeda interested nerds
5:39 · again in total time we will consider
5:42 · moving from left to right as moving from
5:44 · the past to the future
5:46 · so we have our stationary nerd and our
5:48 · moving nerd
5:49 · let's watch what happens as time evolves
5:52 · time presses onward and for our
5:54 · stationary nerd
5:55 · now should look like our slices from
5:57 · before this is their plane of
6:00 · simultaneity where everything in this
6:02 · slice can be considered to be happening
6:04 · at the same time for our moving nerd
6:07 · however who is moving through space and
6:09 · therefore moving through less
6:10 · time their plane can't be moving in the
6:13 · same way
6:13 · can it it must be angled
6:17 · without getting into too much college
6:19 · level physics here the plane of
6:21 · simultaneity
6:22 · must be angled for moving observers
6:24 · because of the nature
6:25 · of the speed of light from both theory
6:27 · and experiment we know that the speed of
6:29 · light remains
6:30 · the same no matter the reference frame
6:33 · for this to be true for moving observers
6:36 · who could look at something and disagree
6:37 · on the speed of it
6:39 · time and space must then shift to
6:42 · accommodate
6:43 · this universal speed limit and how much
6:45 · time and space
6:46 · shifts depends on just how quickly
6:48 · you're going how close you're getting
6:50 · to the speed of light if we go back to
6:52 · our paradox then
6:54 · we can observe that the plane of
6:56 · simultaneity
6:57 · for the moving nerd actually includes a
7:00 · present
7:01 · view of andromeda that is in the past
7:04 · of the stationary nerd two apparently
7:08 · simultaneous observations except one
7:11 · sees
7:11 · aliens and the other sees an alien
7:14 · invasion
7:15 · mbd and we can even calculate the size
7:18 · of this shifting effect
7:20 · but to show you how i must escape to the
7:23 · one place that hasn't been corrupted by
7:25 · capitalism
7:28 · space
7:31 · i'm tim curry from command and conquer
7:35 · andromeda is what astronomers call very
7:37 · far away
7:38 · 2.5 million light years away in fact and
7:41 · so in our view of totality
7:43 · andromeda will also be very far away
7:46 · from our
7:46 · nerds now when you walk past someone on
7:49 · the street
7:50 · your space-time shifting will hardly be
7:53 · anything because when you're walking
7:54 · you're not even close to the speed of
7:56 · light
7:57 · but if your plane angle of simultaneity
8:00 · changes just
8:00 · fractions of a degree it can really add
8:03 · up
8:03 · somewhere really far away like andromeda
8:06 · which is 24 million
8:08 · quadrillion meters away so if we use an
8:11 · equation
8:12 · oh like this one which takes into
8:14 · account time dilation we plug in how far
8:17 · andromeda is away from earth
8:19 · we can see that if you're just walking
8:21 · past someone else at one
8:23 · foot per second which is hardly even a
8:25 · stroll your view of the present
8:27 · in andromeda could differ by as much as
8:29 · a full earth day
8:31 · and if one nerd was going as fast as i
8:33 · am in this awesome spaceship
8:35 · admit it their view of the present
8:37 · moment in a galaxy far away
8:40 · could differ by literally years and
8:43 · kyle i hear you asking in this tone of
8:44 · voice why is there an equation floating
8:47 · in outer space
8:48 · who cares arya take us in
8:53 · the differences between the nows of
8:55 · different observers is called the
8:56 · relativity
8:57 · of simultaneity and it solves the
8:59 · andromeda paradox
9:01 · because of the immutable speed of light
9:03 · two relatively moving observers will
9:05 · never actually agree
9:07 · on what the present moment is they can't
9:10 · this isn't a paradox it's two equally
9:13 · valid assessments of the present moment
9:16 · from different perspectives and because
9:18 · of this
9:19 · it doesn't really make any physical
9:20 · sense in the first place to talk about
9:22 · the now of you and something very far
9:25 · away because of the speed of light and
9:27 · how information
9:28 · travels so when is now well that depends
9:32 · on who you ask until next time
9:37 · now exiting the facility thank you so
9:40 · much to the very nerdy staff at the
9:42 · facility for their direct and
9:43 · substantial support in the creation
9:45 · of this video today i especially want to
9:47 · recognize research assistant solomon de
9:49 · berry
9:50 · and visiting scholar jack akers private
9:53 · eye
9:53 · if you want to join the facility if you
9:54 · want to get on the staff and join the
9:56 · nearly 1200 nerds who
9:57 · every day are coming up with episode
9:59 · ideas for me talking to me in the
10:01 · discord having their own
10:02 · game nights dnd games trivia nights and
10:06 · commander league and radio stations and
10:08 · all the other perks
10:09 · you can go to patreon.com kyle hill
10:12 · right now and get on the staff and if
10:13 · you support the facility just enough you
10:15 · get your name on
10:16 · aria here each and every week and as you
10:18 · can see there's literally hundreds of
10:19 · you so i don't know how i'm gonna
10:21 · pass the look i'm not gonna sugarcoat it
10:23 · this
10:24 · stuff is hard to understand and when i
10:26 · was re-wrapping my mind up around all
10:28 · this uh relativity stuff
10:29 · some videos by my colleague minute
10:31 · physics were very very helpful who did
10:33 · an entire course on relativity and
10:35 · simultaneity and all that stuff
10:36 · so i'd recommend those videos oh still
10:39 · so much more i hope nothing weird
10:41 · happens when i leave
10:45 · just your friendly neighborhood ti-89
10:47 · here remember to shut off your
10:49 · calculator when you're not using it to
10:51 · save battery even though the batteries
10:53 · decrease
10:53 · by just about one percent a month
10:57 · i still would might appreciate it thank
10:59 · you and thanks for watching
11:03 · i'm so i'm so glad nothing weird
11:05 · happened thanks for watching

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--> YouTube-Generated Transcript <--
0:00	·	recalibrate okay synchronization in
0:02	·	three
0:03	·	two one synchronization completely when
0:06	·	is now arya and i now both agree on when
0:10	·	now is but what about you and me as i'm
0:13	·	filming this
0:14	·	episode my present is technically your
0:16	·	past and your present moment
0:18	·	is technically in my future if i was
0:21	·	there next to you
0:23	·	right now we'd of course both agree
0:26	·	on what now is don't don't touch me and
0:28	·	it would be after some excruciatingly
0:30	·	painful
0:31	·	small talk i'm bringing up these
0:32	·	differences because my question for you
0:34	·	today is
0:35	·	does the universe at large have a now
0:40	·	okay nothing or is the present moment
0:42	·	just a matter
0:43	·	of perception now okay let's recalibrate
0:47	·	again jesus
0:49	·	now entering the facility in 1989 the
0:53	·	legendary physicist robert penrose
0:55	·	presented a paradox to the public
0:58	·	he said consider two nerds very
1:00	·	interested in the goings ons in the
1:02	·	galaxy nearest our own
1:04	·	andromeda and one day these two nerds
1:06	·	are walking past each other on the
1:08	·	street
1:08	·	and they say hello nerd friend i would
1:10	·	like to query you as to what is
1:11	·	happening
1:12	·	right now in the present of andromeda if
1:14	·	they had amazing telescopes and didn't
1:16	·	have to wait 2.5 million years for the
1:18	·	light information to get to them
1:19	·	the moving nerd looks at andromeda and
1:23	·	says
1:24	·	hark stationary brethren i see aliens
1:27	·	and their elder councils debating
1:29	·	whether or not to invade earth right now
1:31	·	who voice but
1:34	·	the stationary nerd looks at andromeda
1:36	·	and says
1:37	·	nary you fool they have already
1:40	·	deliberated and their alien fleet is
1:42	·	on the way right now to shoot laser
1:44	·	beams at our faces
1:46	·	the paradox here is that it is
1:48	·	theoretically possible
1:49	·	for these two nerds to disagree for one
1:51	·	nerd to apparently see into the
1:54	·	future of the other but how can two
1:57	·	simultaneous observations of the present
1:59	·	be different
2:01	·	well to explain that i need to get
2:04	·	changed arya
2:05	·	activate carl sagan mode
2:09	·	how should we define now how do we
2:12	·	suss out what is truly simultaneous well
2:15	·	to figure that out from scratch we must
2:17	·	first consider the universe not just at
2:19	·	one time
2:20	·	but at all times i didn't have a
2:22	·	turtleneck shut up suppose
2:24	·	that we have a camera a camera of the
2:26	·	imagination as carl
2:28	·	might have and this camera allows us to
2:30	·	magically take a
2:31	·	snapshot of the entire universe inside
2:34	·	of this snapshot in all of
2:36	·	three-dimensional space
2:38	·	everything should be simultaneous for
2:40	·	example me
2:41	·	talking to you a student on the other
2:43	·	side of the world doing their homework
2:45	·	and
2:45	·	blurpon from the artemis cluster who's a
2:47	·	good friend of mine hashing grebos
2:49	·	all day like he usually does they are
2:52	·	delicious
2:53	·	now if we were to keep taking snapshots
2:56	·	eventually would have this
2:57	·	abstracted view of all of space and time
3:00	·	that we could
3:01	·	look at and piece together now many
3:03	·	science communicators call this the
3:05	·	universal
3:06	·	loaf of space-time but that sounds weird
3:08	·	and stupid it makes you think of bread
3:10	·	i'm hungry you shouldn't be eating as
3:11	·	many carbs as you are shut up
3:13	·	i'm going to call this totally time
3:16	·	every moment that the universe has had
3:19	·	is having
3:21	·	or will have in this higher dimensional
3:24	·	view of t'tala time
3:25	·	all time and all events really do exist
3:29	·	there's a snapshot where everything is
3:30	·	simultaneous for you your present
3:32	·	but the past here isn't just a memory
3:35	·	and the future
3:36	·	isn't uncertain it's all there every
3:39	·	single point in time
3:40	·	equally as valid as your present it all
3:43	·	happens now you might be thinking then
3:45	·	if this eternalist view of the universe
3:47	·	is true
3:48	·	why do all slices as we define them have
3:51	·	to look like this
3:52	·	why doesn't a snapshot of the universe
3:54	·	look like this or
3:55	·	even this well that's a good question
3:58	·	deactivate carl sagan mode different
4:02	·	nows is the very heart of the andromeda
4:05	·	paradox a paradox that may be impervious
4:08	·	to common sense
4:09	·	but not to einstein's theory of
4:12	·	relativity oh come on
4:14	·	what is what is going on with you today
4:19	·	fun fact the andromeda galaxy is on a
4:21	·	collision course with the milky way it's
4:24	·	a fun fact because that's more than four
4:25	·	billion years out and you are definitely
4:27	·	not going to make it but whether we're
4:29	·	here or not the milky way and andromeda
4:31	·	are going to crash together however when
4:34	·	this happens it's not going to be the
4:36	·	cosmic calamity that you may expect you
4:38	·	see space is big
4:40	·	it's vast it's bigger than fast we don't
4:42	·	have words to describe
4:43	·	just how big space is and how large the
4:46	·	distance between
4:47	·	individual stars are so when you have
4:50	·	andromeda with literally trillions of
4:52	·	stars moving at 100 kilometers per
4:54	·	second towards the milky way when they
4:56	·	finally interact
4:57	·	there's unlikely to be a single solar
5:01	·	collision not one if we were still
5:04	·	around
5:04	·	in the solar system we probably wouldn't
5:06	·	even notice this event
5:08	·	happening as a wise man once said
5:12	·	whoa now as we explained in our episode
5:17	·	about the spaceships paradox
5:18	·	how you move through space
5:20	·	relativistically speaking can affect how
5:22	·	you move
5:23	·	through time more specifically if you
5:25	·	move really fast through space approach
5:28	·	the speed of light
5:29	·	you move less in time this
5:32	·	fact brings us back to our view of total
5:35	·	time
5:35	·	and now we should track our two
5:37	·	andromeda interested nerds
5:39	·	again in total time we will consider
5:42	·	moving from left to right as moving from
5:44	·	the past to the future
5:46	·	so we have our stationary nerd and our
5:48	·	moving nerd
5:49	·	let's watch what happens as time evolves
5:52	·	time presses onward and for our
5:54	·	stationary nerd
5:55	·	now should look like our slices from
5:57	·	before this is their plane of
6:00	·	simultaneity where everything in this
6:02	·	slice can be considered to be happening
6:04	·	at the same time for our moving nerd
6:07	·	however who is moving through space and
6:09	·	therefore moving through less
6:10	·	time their plane can't be moving in the
6:13	·	same way
6:13	·	can it it must be angled
6:17	·	without getting into too much college
6:19	·	level physics here the plane of
6:21	·	simultaneity
6:22	·	must be angled for moving observers
6:24	·	because of the nature
6:25	·	of the speed of light from both theory
6:27	·	and experiment we know that the speed of
6:29	·	light remains
6:30	·	the same no matter the reference frame
6:33	·	for this to be true for moving observers
6:36	·	who could look at something and disagree
6:37	·	on the speed of it
6:39	·	time and space must then shift to
6:42	·	accommodate
6:43	·	this universal speed limit and how much
6:45	·	time and space
6:46	·	shifts depends on just how quickly
6:48	·	you're going how close you're getting
6:50	·	to the speed of light if we go back to
6:52	·	our paradox then
6:54	·	we can observe that the plane of
6:56	·	simultaneity
6:57	·	for the moving nerd actually includes a
7:00	·	present
7:01	·	view of andromeda that is in the past
7:04	·	of the stationary nerd two apparently
7:08	·	simultaneous observations except one
7:11	·	sees
7:11	·	aliens and the other sees an alien
7:14	·	invasion
7:15	·	mbd and we can even calculate the size
7:18	·	of this shifting effect
7:20	·	but to show you how i must escape to the
7:23	·	one place that hasn't been corrupted by
7:25	·	capitalism
7:28	·	space
7:31	·	i'm tim curry from command and conquer
7:35	·	andromeda is what astronomers call very
7:37	·	far away
7:38	·	2.5 million light years away in fact and
7:41	·	so in our view of totality
7:43	·	andromeda will also be very far away
7:46	·	from our
7:46	·	nerds now when you walk past someone on
7:49	·	the street
7:50	·	your space-time shifting will hardly be
7:53	·	anything because when you're walking
7:54	·	you're not even close to the speed of
7:56	·	light
7:57	·	but if your plane angle of simultaneity
8:00	·	changes just
8:00	·	fractions of a degree it can really add
8:03	·	up
8:03	·	somewhere really far away like andromeda
8:06	·	which is 24 million
8:08	·	quadrillion meters away so if we use an
8:11	·	equation
8:12	·	oh like this one which takes into
8:14	·	account time dilation we plug in how far
8:17	·	andromeda is away from earth
8:19	·	we can see that if you're just walking
8:21	·	past someone else at one
8:23	·	foot per second which is hardly even a
8:25	·	stroll your view of the present
8:27	·	in andromeda could differ by as much as
8:29	·	a full earth day
8:31	·	and if one nerd was going as fast as i
8:33	·	am in this awesome spaceship
8:35	·	admit it their view of the present
8:37	·	moment in a galaxy far away
8:40	·	could differ by literally years and
8:43	·	kyle i hear you asking in this tone of
8:44	·	voice why is there an equation floating
8:47	·	in outer space
8:48	·	who cares arya take us in
8:53	·	the differences between the nows of
8:55	·	different observers is called the
8:56	·	relativity
8:57	·	of simultaneity and it solves the
8:59	·	andromeda paradox
9:01	·	because of the immutable speed of light
9:03	·	two relatively moving observers will
9:05	·	never actually agree
9:07	·	on what the present moment is they can't
9:10	·	this isn't a paradox it's two equally
9:13	·	valid assessments of the present moment
9:16	·	from different perspectives and because
9:18	·	of this
9:19	·	it doesn't really make any physical
9:20	·	sense in the first place to talk about
9:22	·	the now of you and something very far
9:25	·	away because of the speed of light and
9:27	·	how information
9:28	·	travels so when is now well that depends
9:32	·	on who you ask until next time
9:37	·	now exiting the facility thank you so
9:40	·	much to the very nerdy staff at the
9:42	·	facility for their direct and
9:43	·	substantial support in the creation
9:45	·	of this video today i especially want to
9:47	·	recognize research assistant solomon de
9:49	·	berry
9:50	·	and visiting scholar jack akers private
9:53	·	eye
9:53	·	if you want to join the facility if you
9:54	·	want to get on the staff and join the
9:56	·	nearly 1200 nerds who
9:57	·	every day are coming up with episode
9:59	·	ideas for me talking to me in the
10:01	·	discord having their own
10:02	·	game nights dnd games trivia nights and
10:06	·	commander league and radio stations and
10:08	·	all the other perks
10:09	·	you can go to patreon.com kyle hill
10:12	·	right now and get on the staff and if
10:13	·	you support the facility just enough you
10:15	·	get your name on
10:16	·	aria here each and every week and as you
10:18	·	can see there's literally hundreds of
10:19	·	you so i don't know how i'm gonna
10:21	·	pass the look i'm not gonna sugarcoat it
10:23	·	this
10:24	·	stuff is hard to understand and when i
10:26	·	was re-wrapping my mind up around all
10:28	·	this uh relativity stuff
10:29	·	some videos by my colleague minute
10:31	·	physics were very very helpful who did
10:33	·	an entire course on relativity and
10:35	·	simultaneity and all that stuff
10:36	·	so i'd recommend those videos oh still
10:39	·	so much more i hope nothing weird
10:41	·	happens when i leave
10:45	·	just your friendly neighborhood ti-89
10:47	·	here remember to shut off your
10:49	·	calculator when you're not using it to
10:51	·	save battery even though the batteries
10:53	·	decrease
10:53	·	by just about one percent a month
10:57	·	i still would might appreciate it thank
10:59	·	you and thanks for watching
11:03	·	i'm so i'm so glad nothing weird
11:05	·	happened thanks for watching