Category
😹
FunTranscript
00:00 Of all two trillion galaxies in the observable universe, the Milky Way, our home, is humanity's
00:07 most important one.
00:08 Spanning roughly 100,000 light years in diameter, it holds between 100 and 400 billion stars,
00:16 including our own sun.
00:17 But some scientists think there could actually be many more stars than meets the eye, and
00:23 that there's a lot more going on in, or should we say parallel to, the Milky Way than
00:29 we currently think.
00:31 This is Unveiled, and today we're answering the extraordinary question; is the Milky Way
00:35 hiding a parallel universe?
00:38 Do you need the big questions answered?
00:40 Are you constantly curious?
00:42 Then why not subscribe to Unveiled for more clips like this one?
00:45 And ring the bell for more thought-provoking content!
00:48 On a clear, moonless night, somewhere where the view is entirely untainted by light pollution,
00:54 the vibrant Milky Way can be seen trailing across the sky.
00:58 In some places on Earth, its shine dominates between horizons, wrapping around the planet
01:03 like a giant, cosmic ring.
01:05 Its name reflects its appearance, and it has forever been one of the most prominent objects
01:10 visible at night; a must-see spectacle for any citizen of Earth.
01:15 For as long as humans have existed, we've curiously pondered the nature of our place
01:19 in space, and of our home galaxy.
01:22 Modern astronomy has given us an abundance of knowledge about the Milky Way, from its
01:26 size and mass, to its rotation period, thickness, and luminosity.
01:31 For example, we know the sun takes approximately between 225 and 250 million years to do an
01:38 entire lap around the galactic centre.
01:41 But regardless, there still remains so much we don't know about our own celestial neighbourhood.
01:46 And just recently, scientists may have landed on something pretty massive.
01:50 They've started to look into an entirely new form of star, a type that might also be
01:56 scattered all across the sky.
01:58 While such stars may be in abundance throughout the universe, though, they're also almost
02:03 completely invisible.
02:04 They're called mirror stars, and are actually a fairly common prediction of certain dark
02:09 matter models.
02:11 New science increasingly hypothesises that these stars are indeed physical, that they
02:15 do exist, and then that the Milky Way is home to countless numbers of them.
02:20 Which brings up some questions right away.
02:22 Like, isn't dark matter notorious for being impossible for humans to detect?
02:27 How is it, then, that mirror stars, dependent on dark matter, are suddenly thought to be
02:32 everywhere?
02:33 How can the galaxy be full of them?
02:34 And is it possible to prove that they exist if they do?
02:37 Surely such objects could only ever be theoretical.
02:41 But astronomers are increasingly confident that they have cracked the secret behind them,
02:45 and therefore believe that they're within reach of detecting mirror stars beyond any
02:50 doubt at all.
02:51 When they do, it could spell a monumental paradigm change in our understanding of the
02:55 cosmos.
02:56 But, first, let's set the scene for some context.
02:59 For a while now, dark matter's existence in general has been considered definite, but
03:04 we still know little about its origin or composition.
03:07 This is because one of the key problems is that we've only ever observed it indirectly,
03:12 via its gravitational interactions with regular matter.
03:15 In general, while dark matter doesn't interact in any way that's visible to the eye, its
03:20 domination of the universe is evident in the motion and movements of large-scale structures.
03:25 For example, one of the first hints toward dark matter came from analysis of galaxy rotation
03:30 curves.
03:31 It was previously hypothesised that galaxies would rotate slower on their edges than in
03:36 the centre, but measurements said otherwise.
03:39 They showed rotation to be constant regardless of where you are in the galaxy.
03:44 This then is indicative of a great deal of invisible matter; dark matter, spread evenly
03:50 across the galaxy.
03:52 Further observation went on to find that 27% of the entire cosmos is composed of dark matter,
03:58 with only 5% being regular matter.
04:01 This is now old news, but when it was first understood, it was… pretty shocking.
04:07 And many different ideas on exactly how it works have been put forward since, none of
04:11 which solve dark matter completely.
04:14 That last part might soon be about to change, however, with an emerging crowd favouring
04:18 what's known as the Atomic Dark Matter Model, or ADM.
04:23 While most previous theories hypothesised dark matter to derive from one singular particle
04:27 - with that particle behaving unlike anything else in the standard model - ADM effectively
04:33 believes in a second standard model, populated by dark particles, with a dark electromagnetism
04:40 equivalent, complete with a dark photon.
04:43 In short, if it does exist, then this is very literally "new physics".
04:48 Like opening a favourite book, but realising that there's an entire, crucial chapter
04:53 that you've never read before.
04:55 Or even that there's an entire second half that you never even noticed.
04:59 What's more, many of the principles at play here have seemingly been predicted by and
05:04 via other mysteries relating to the standard model.
05:07 For example, much of the speculative "Mirror Twin Higgs" cosmology also suggests a whole
05:13 dark section.
05:14 There are then further, again quite speculative, musings around the possibility for dark matter
05:20 electrons, protons and neutrons specifically… and all potentially staging not just gravitational
05:26 interactions, but nuclear, too.
05:29 Until now, such ideas have felt a little… loose.
05:33 But things seemingly get significantly more interesting with ADM in particular, since
05:38 it's a model which allows for atomically bound states - i.e. for systems bound together
05:43 with fundamental particles.
05:45 If true, and in short, this would mean that dark matter can bunch or collapse to form
05:50 larger objects, much like we know the atoms of regular matter already do.
05:55 Which brings us back to mirror stars, arguably the most interesting and dramatic predicted
06:01 dark matter objects of all.
06:03 At their simplest, these are literally stars created out of dark matter.
06:08 It's then thought that they emit dark photons from their energetic centres, akin to regular
06:14 stars.
06:15 And, at this still quite early stage, one of the best things about them is that researchers
06:19 do think we can realistically hope to observe them.
06:23 Because it's thought that mirror stars capture tiny quantities of regular matter as well,
06:28 which then sinks down to their core.
06:31 This is comparable to the sun capturing dark matter, which is an idea that's actually
06:35 quite common in various cosmological theories.
06:38 Clearly, a star is a sizeable prospect.
06:41 Even in the vastness of the universe, stars are massive enough to attract and warrant
06:45 attention.
06:46 Here then, they might finally offer a route or gateway that's substantial enough to
06:51 uncover the mystery of dark matter.
06:54 Scientists believe that the captured regular matter in such objects will accumulate over
06:59 time, turning into what have come to be known as "nuggets".
07:03 Small pieces of detectable material indicative of a wider truth.
07:07 These nuggets, if they do form, should be heated within the core of a mirror star, which
07:12 should lead to electromagnetic radiation that's relatively simple to detect.
07:17 If the theories prove sound, then mirror stars should ultimately serve as emerging beacons,
07:23 ready to light our way to full disclosure on dark matter.
07:27 Unfortunately, while it all works on paper, it's thought that mirror star nugget emissions
07:32 will be extremely faint.
07:33 It's not as though now we suspect that they're there, we'll just start spotting
07:37 them all over the place.
07:38 However, the science is moving quickly.
07:41 Towards the end of 2023, a Canadian team led by Isabella Armstrong submitted a paper detailing
07:47 what these emissions would look like, again revealing, theoretically, that they'd send
07:51 off dim signals since they're much redder and fainter than regular stars.
07:56 It's perhaps a little vague right now, but thanks to work like this, the path is certainly
08:00 open today for telescopes to search for these signals directly… and to finally give some
08:06 proper insight into the true nature of that otherwise mostly unknown 27% of the universe.
08:12 Currently, one issue is that there's an abundance of dim objects we do already know
08:16 about in the cosmos.
08:18 From white dwarfs to planetary nebulae, there are endless standard matter astrophysical
08:23 phenomena that could be mistaken for our dark universe nuggets.
08:27 Thankfully, cosmologists have already devised and suggested methods to distinguish between
08:32 nuggets and regular matter sources.
08:34 It is a very tricky skill to master, but it seemingly is possible.
08:39 Nevertheless, even the mere suggestion of mirror stars is huge news.
08:43 For one, it means that sky surveys might now be able to add dark matter to their observations
08:48 list.
08:49 Other methods of detection could result from that, and the route to unveiling the mystery
08:53 of matter will be lit brighter than ever before.
08:57 More broadly, mirror stars represent our first look at what some have already dubbed an entire
09:03 mirror universe.
09:04 As the underlying mechanics of the phenomenon are still unknown, this still counts as mostly
09:09 speculation.
09:10 However, it's an idea that bears similarities to many more physical theories on the potential
09:15 for parallel worlds.
09:16 In this case, it could be that an entirely alien plane of reality has actually always
09:21 existed all around us… it's just that we've never even begun to understand that
09:26 it's there.
09:27 From here, there are all kinds of follow-on questions.
09:30 If there is a mirror universe, then is there mirror life there?
09:34 Would such a place simply be another version of our own universe, except with the fundamental
09:39 particles reversed?
09:40 Or would there be more and less predictable differences between there and here?
09:45 Let us know what you think in the comments.
09:47 Socrates once reputedly said, "The more I know, the more I realize I know nothing."
09:54 And now there's a strong chance that the discovery of mirror stars will trigger many
09:59 more new questions than solve old ones.
10:01 It could potentially cause an entire re-evaluation of the Standard Model.
10:06 But that's how the Milky Way could be hiding a parallel universe.
10:11 The universe is 13.8 billion years old.
10:15 Modern humans have walked Earth for only the last 300,000 years of that.
10:18 So, what could've happened in the long stretch of time between the Big Bang and the emergence
10:23 of Homo sapiens on this planet?
10:25 There's a lot that we know, and a lot that we don't… but some theories bridge the
10:29 gap in more unusual ways than others.
10:32 This is Unveiled, and today we're answering the extraordinary question; are there ancient
10:36 humans living in the Milky Way?
10:38 Are you a fiend for facts?
10:40 Are you constantly curious?
10:42 Then why not subscribe to Unveiled for more clips like this one?
10:45 And ring the bell for more fascinating content!
10:47 A headline-making study in June 2020 claimed that there could be dozens of alien civilizations
10:53 living in our galaxy, the Milky Way.
10:55 36 was the most often-cited figure, although the upper estimate went past 200.
11:00 That's 200 individual alien societies reportedly living on our doorstep… in cosmological
11:06 terms.
11:07 But, let's be clear; there's so far zero actual proof that there are any alien civilizations
11:12 out there.
11:13 The general scientific consensus is that there must be, but we've so far found nothing
11:17 by way of hard, irrefutable evidence.
11:20 The Fermi Paradox continues to plague our search for extraterrestrial life.
11:24 The 2020 study, though, was inspired by various projections and predictions, including the
11:29 Drake Equation.
11:30 Its claim of 36 neighbouring alien groups has since been debated and disputed.
11:35 We ourselves released a video, and there's a link at the end of this episode.
11:39 But say there are other bands of living beings… and say they really are not so far away from
11:43 us… then what are they doing there?
11:46 Some theories, most notably the Zoo Hypothesis, argue that nearby, superior alien groups are
11:51 busy watching and possibly experimenting on us.
11:54 Others, like the Dark Forest Theory, suggest that any alien society trying to survive will
11:59 wisely remain as quiet and undetectable as they possibly can.
12:04 There are, though, some more unconventional theories to suggest that if there are aliens
12:07 out there, they might not be all that different from us at all.
12:11 One study, published in December 2020 by researchers at Caltech, aimed to map the potential for
12:16 life in the Milky Way more precisely than ever before.
12:20 Paying close attention to the probability that life will - and does eventually self-annihilate
12:24 - as well as the likelihood of the emergence of life, of abiogenesis, in the first place,
12:29 it delivered some interesting results.
12:31 It found that life was most likely in the Milky Way around eight billion years after
12:36 it formed, and around 13,000 light-years from the galactic centre.
12:40 Considering that we appeared more than 13.5 billion years after galaxy formation, and
12:44 that we're now 25,000 light-years from the galactic centre, this would suggest that humans
12:49 are doing quite well for themselves.
12:51 According to the study, we're here far too late, in completely the wrong place, and are
12:55 therefore way past the peak of life in this galaxy.
12:59 And yet, we're surviving.
13:00 Well done, us!
13:02 But what do these conclusions infer about the rest of life in the Milky Way?
13:05 One takeaway is that, if the study rings true, there should be a band of space almost halfway
13:10 between us and the heart of the galaxy - 13,000 light-years from the centre - wherein life
13:15 is much more likely to exist than anywhere else.
13:18 But another is that most life in this galaxy should've emerged more than 5.5 billion
13:23 years before we did.
13:24 And if that's true, then what happened to it?
13:27 The short answer is, it killed itself off.
13:30 The Caltech study highlights the key role self-annihilation likely plays in how far
13:34 any civilization can reasonably spread.
13:37 Away from the study, the general idea is that all life dies before it gets big enough to
13:41 be noticed.
13:42 The slightly frightening assumption, then, is that the same thing will happen to human
13:46 beings.
13:47 That we'll only ever get so far before we destroy ourselves from within.
13:51 But still, if even just one such civilization did manage to survive, then they would certainly
13:56 be considered ancient to our lowly minds.
13:59 Ancient human history barely goes back five and a half thousand years, but now we're
14:03 imagining life that's five and a half billion years old.
14:07 Not that such a hypothetical lifeform should ever automatically be billed as ancient human…
14:12 even if we could prove that it exists.
14:14 The chances of anything else separately evolving to be even slightly recognisably similar to
14:19 us are… extremely low.
14:21 The aliens we see in movies and read about in books are all too often humanoid in nature,
14:26 with eyes and hands and heads and some kind of audio language… but, in reality, they'd
14:32 probably look nothing like us, and according to some theories, might not even be carbon-based.
14:37 The picture gets a little stranger, though, when ideas on panspermia get thrown into the
14:42 mix.
14:43 Subscribers to various ancient alien theories argue that biological material could've
14:46 been distributed all across the universe in the time since its inception; that we think
14:51 we're rare on Earth, but that actually we're just one of countless locations that life
14:55 has reached.
14:56 And this is what panspermia amounts to; the spreading of life throughout the cosmos, usually
15:01 via space dust, asteroids and colliding planets.
15:05 Directed panspermia, though, brings a degree of agency to the table; the idea now being
15:09 that life is deliberately spread to other worlds by advanced, travelling alien species.
15:14 Again, there's little by way of credible, mainstream science to suggest that this is
15:19 what actually happened here on Earth.
15:21 But with such a long time gap to fill between the start of this planet and the start of
15:24 humankind on this planet, fringe theories abound that ancient humans either seeded here
15:29 or arrived and settled here millions or billions of years ago.
15:34 In this version of life, the universe and everything, it's as though we're a colony
15:38 established in the distant past by an older, more advanced version of ourselves.
15:43 Through the lens of the Caltech study, we might imagine that those older, superior humans
15:47 had emerged long ago, out of the optimum region for life in the Milky Way, thirteen thousand
15:52 light-years away from the galactic centre, and twelve thousand light-years away from
15:55 us.
15:56 They then brought their human civilization here before carrying on their merry way into
16:01 the rest of the galaxy.
16:02 But one final consideration for today's question is; what if we aren't the product
16:06 of panspermia, but we're actually the ones facilitating it?
16:10 Another popular fringe theory is that life did originate on Earth, but the history of
16:14 human evolution isn't what we generally think of it as.
16:18 Instead of the earliest hominins emerging around nine million years ago, and modern
16:22 humans about three hundred thousand years ago, some claim that there were humans before
16:26 this… and that they became advanced enough to leave Earth forever.
16:30 Importantly, there is, again, precious little scientific or historical evidence that this
16:35 really is the case.
16:36 It's an idea, an unsubstantiated theory, but one that's captured the imagination
16:41 of many a science fiction writer before now.
16:43 Again, it allows us to imagine that the Milky Way is actually full of life, perhaps both
16:48 boasting far more than just the thirty-six civilizations suggested by the June 2020 study.
16:54 Only in this version of events, many of those could be our ancestors.
16:57 It's just that they started on Earth and then set off to the stars, just as we're
17:01 trying to do today.
17:03 The biggest argument against this line of thinking, however, is that it assumes that
17:07 Earth is basically the centre of everything.
17:09 That's despite the overwhelming statistical likelihood that it isn't.
17:13 If either panspermia theory is true - that we were spread by others, or that we started
17:17 on Earth and are now spreading elsewhere - it's much more likely the first one.
17:22 To bring in the Caltech study one final time, even had humans somehow instantly appeared
17:26 on this planet at the moment that Earth was born - an obvious impossibility - then they'd
17:31 still be only 4.5 billion years old.
17:34 Which would still place us as arriving later than the optimum time for life in the Milky
17:38 Way, eight billion years after it formed.
17:41 The idea becomes marginally more palatable if we imagine that humans didn't start on
17:45 Earth, but were seeded here instead by other humans.
17:48 Then, theoretically, we'd have so much more time to play with across the history of the
17:53 universe.
17:54 Our story could be pushed further back, to a time before Earth and a time within Caltech's
17:59 optimum parameters.
18:00 And it can be pushed further forward, because we're no longer confined to just one world.
18:06 Earth becomes just one of many that we might have visited in the past, or in the future.
18:10 And suddenly, the rest of the Milky Way is our playground.
18:14 But ultimately, all of those stipulations require us to make some gigantic leaps in
18:18 our understanding of why we're here, what it takes for us to survive, and how significant
18:23 we really are in the universe.
18:25 More and more scientists are growing to accept that alien life must exist somewhere in space…
18:31 but human life?
18:32 Perhaps we'll only believe that when we see it.
18:35 What do you think?
18:36 Is there anything we missed?
18:37 Let us know in the comments, check out these other clips from Unveiled, and make sure you
18:40 subscribe and ring the bell for our latest content.
18:43 (electronic music)