
Scientists are searching for a mirror universe - rfreytag
https://www.nbcnews.com/mach/science/scientists-are-searching-mirror-universe-it-could-be-sitting-right-ncna1023206
======
mikorym
Barring the terrible style of the article, I think the concept of a mirror
universe is not difficult to understand.

If we take our three spacial dimensions, and add another time dimension, then
we can do a reflection at t=0 and this will produce a mirror object of
everything from t>0 at t<0\. (Note that in three dimensions, if we perform a
reflection it is the same as a rotation when we add a fourth dimension,
meaning we can do this "mechanically" if that is worth anything to you.)

This universe at t<0 looks exactly the same as our universe at t>0, except
that you switch chirality (or left and right if you will). Now my toy example
does not have exotic matter (abundance) differences and also cannot comment at
things at the speed of light. In that sense it is Euclidean or perhaps
Newtonian.

But what is interesting is that this toy example gives us a concrete way to
understand right and left. You can choose anything to call left and anything
to call right. But the side at which your heart is of your body will be
switched at t<0\. Additionally, and this is the only part that I find
important or useful, we have actually partitioned things now according to
whether they internally define left and right in the usual way or in the
opposite way. And finally, we can even now say that subatomic particles that
decide to decay as matter or antimatter now self-identify themselves for us
and their choice of chirality determines their position at either x > 0 or -x
< 0.

EDIT: Disclaimer: I am a mathematician, not a physicist.

~~~
nabla9
Physicists have considered two time dimensions, but it seems that 3+1
spacetime is 'priviledged'. Here is a chart showing properties of
n+m-dimensional spacetimes
[https://en.wikipedia.org/wiki/File:Spacetime_dimensionality....](https://en.wikipedia.org/wiki/File:Spacetime_dimensionality.svg)

This article speaks about mirror universe that exists in the same 3+1
dimensional space-time as ours. It's just that the two are transparent to each
other. Only gravity ties them together.

~~~
lukev
If this concept is interesting to you, Greg Egan has written an entire scifi
novel (Dichronauts) set in a 2+2 universe. Weirdness abounds, but quite
rigorous.

~~~
Jach
Was going to highlight that book too. It's also helpful / fun to explore the
articles and visualizations outside the book either before/during/after
reading it.
[https://www.gregegan.net/DICHRONAUTS/DICHRONAUTS.html](https://www.gregegan.net/DICHRONAUTS/DICHRONAUTS.html)

------
kazinator
> _“It’s pretty wacky,” Broussard says of her mind-bending exploration._

The quality level here smacks of 1999 vintage Onion:

[https://www.theonion.com/worlds-top-scientists-ponder-
what-i...](https://www.theonion.com/worlds-top-scientists-ponder-what-if-the-
whole-univers-1819565229)

~~~
zazzlez
Thanks for the link

------
jerf
I was under the impression baryonic matter has been strongly excluded as a
candidate for dark matter, because dark matter does not seem to clump
together; it seems to interact with itself only through gravity as well. So it
can't be any kind of baryonic matter, in a mirror universe or a nearby brane
or anything like that, which is also why the idea of "dark matter life" does
not seem likely; you can't build life out of a material that interacts with
itself only gravitationally.

Although, do free neutrons clump?

Then again, if the neutrons oscillate to "mirror" and then have a high
probability of coming back, presumably an independent probability over time,
that can't be dark matter either since it tunnels back on timeframes even
humans consider short.

Anyhow, on the article's own terms, the connection to dark matter seems
tenuous.

------
arien
This reminds me of 'The Gods Themselves', by Asimov. Doesn't talk about a
mirror universe per se, but a parallel one. It's one of my favourite Asimov
stories outside the Foundation/Robots series.

~~~
AnIdiotOnTheNet
Personally I think it is Asimov's best work, with I Robot not far behind and
Foundation in a distant third. Honestly not sure why people are so enamored of
Foundation.

~~~
Arnavion
I disliked The Gods Themselves when I read it the first time because of all
the freaky alien sex that was described in so much detail. Of course I was a
child at the time.

I liked Foundation because of the series aspect - it was a cool premise and it
was good to have so many books cover it thoroughly. I did find the last bits
that were just to tie it together with the Elijah Bailey stories to be boring.

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nsxwolf
So the mirror universe is where the dark matter we can't find is, and for some
reason it just happens to form halos around where our galaxies are, just to
make their rotations weird. This is a strangely specific mirror universe.

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hsnewman
I just don't get how there can be more than one universe. Multiple dimensions
still would be in the universe.

The definition of THE universe is: "all existing matter and space considered
as a whole; the cosmos".

~~~
xlog
This is a semantic problem, not a physical. Generally, there is no single
definition of the word 'universe' that all physicists ascribe to. When you
have causally disjoint set of spacetimes that may or may not be governed by
the same set of physical laws, some people choose call these multiple
universes.

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ta1234567890
Don't know enough physics to talk about the specifics of this particular
experiment/research. But, it seems to me, that we live in the midst of the
intersection of the "real" world and the mirror one. Similar to Newton's third
law (action/reaction), for anything to exist (or make sense to us), the
complement of that thing needs to exist too. For example, if there was only
one color, there would be no colors, we need for two colors to exist so we can
tell them apart. Things only make sense to us in contrast to what they are
not.

Following the above concept, you could "split up" (conceptually) the
world/universe into explicit complements and you'd have the universe and its
mirror. And this is in fact a very old concept, very well illustrated by the
yin and yang.

~~~
dmitrybrant
According to modern physics, the total energy of our universe is in fact zero,
with matter and radiation contributing to "positive" energy, and gravity and
other quantum effects contributing to "negative" energy. This is actually the
reason we're able to say that our universe could have arisen from nothing,
since only a universe with zero total energy can do that.

Therefore, by Occam's razor, we don't need another "mirror" universe to
balance out this one.

~~~
pgt
I had never considered it like that, but it feels true. Do you have some
reference material for the statement that gravity and quantum effects are
“negative energy”?

~~~
dmitrybrant
It's not difficult to derive why the gravitational potential energy must be
negative.[0]

For the cosmological implications of this fact, there's Lawrence Krauss's book
"A Universe from Nothing", also "The Inflationary Universe" by Alan Guth, and
Stephen Hawking touches on it in "A Brief History of Time."

[0]
[https://en.wikipedia.org/wiki/Gravitational_energy](https://en.wikipedia.org/wiki/Gravitational_energy)

------
mykhamill
Is the time difference between the neutron experiment results due to time
dilation? One of them had the neutrons moving at high speed, I.e. In a
particle beam.

~~~
Jemm
No. Well, sort of. The time difference has to do with how you store free
neutrons. Different conditions suppress, to varying extents, the possible
energy states of the vacuum field.

Just as in the Casimir experiment it was demonstrated that opposed conductive
plates are attracted with a force that results from the suppression of vacuum
energy states between them, so must the decay of the neutron be modulated by
the vacuum field.

If you contrive the storage system to suppress the vacuum energy to a greater
extent, the field will interact less with free neutrons and they will live a
little longer. Likewise, the more possible energy states, the shorter they
live.

This effect is apparent because the free neutron is quite unstable and short-
lived. It is readily affected by the particle-antiparticle pairs that are
always popping into and out of existence in the vacuum.

Protons, which are very stable and last a long time, show the same effect, but
you would be long dead by the time you observed it. So not a practical
experiment.

Why does a radioactive element decay at a particular time? Why is it random?
Why is Schroedinger's cat a superposition of alive/dead with no way of
predicting which one until you observe it and collapse the wave equation?

The answer to all of these is the same. The background state of the universe
is chaotic. It visibly affects things that are unstable, while not having much
effect on things that are stable.

The faster something is moving, the more mass it has. The more mass, the less
it is affected by the vacuum field. This is the mechanism of time dilation.
Increased mass, decreased size, increased density, surrounded by mass, all of
these contrive to suppress the interaction of the vacuum field with an object
by limiting the possible states it can occupy.

The outcome looks to us like order, but it's not. Everything is randomness and
chaos.

Newton's laws are approximations because they apply simple math to chaos.
Likewise, general relativity is a geometric theory applied to a chaotic
universe. It's a good approximation of what we see, but it's only an
approximation. No geometric theory can explain something that is fundamentally
chaotic.

There. Is. No. Meaning.

Sleep well!

------
Udo
I liked the original form of this idea better, when it was hypothesized that
universes are packed into a stack-like structure of membranes, although the
mirror hypothesis has the benefit of being theoretically accessible to
experimentation.

There are a couple of neat effects that fall out of the (mem)brane hypothesis.
For example, it offers a model for why gravity is seemingly so weak compared
to the other forces: because a large part of it leaks out into neighboring
universes. In that case, we'd have a handy explanation for dark matter as
well: it's gravity that leaks _in_ from neighboring universes. This would mean
that stuff clumps together across universes. It could also be an auxiliary
model for black hole formation in certain cases where we have yet to find out
how some black holes could grow very quickly.

If we ever become a K3 civilization we could attempt to send a message across
universes with gravity, or possibly even paint a symbol into the sky using
large masses. Not we know how likely the other universes are to support life
(probably not very).

~~~
magduf
I know Kardashev never proposed a level 4 on his scale, but would a K4
civilization be one that can span parallel universes?

~~~
Udo
I don't know since merely controlling the area is not enough, you'd have to
capture (and use) all the stellar energy that comes out of that region. So K4
could be something like "uses the energy of the entire visible universe", but
that's a shrinking concept over the time scales in question.

It's not a well-defined scale anyway, since you could probably build a
K3-equivalent civilization with only a few star systems using miniature black
holes as reactors; conversely, you could easily be a galaxy-spanning
civilization but only use a fraction of the total stellar output.

The concept of translating into another universe does seem like an appropriate
achievement and next step after K3. Since another universe might have wildly
different basic parameters, classical sci-fi portals and such are probably out
of the question. You'd have to translate the information stored in the brain
into something appropriate that could continue to perform roughly the same
functions on the other side.

------
cliffy
If there is/are mirror universe(s), wouldn't we detect particles coming from
unexplained sources experimentally?

Or is the 'portal' mechanism triggered so rarely that we would probably never
observe it happening naturally?

~~~
dclowd9901
Isn't this reflected in the 10-second discrepency of decay they mention in the
article?

------
jdashg
Despite its timecube-like-energy, I'm reminded of this:
[http://www.januscosmologicalmodel.com](http://www.januscosmologicalmodel.com)

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YayamiOmate
Hmmm how does one store neutrons? Because I highly doubt the bottle...

It seems that in the crucial part the article makes gross oversimplification.
I would imagine storage impacts observed half-life.

~~~
dzmien
With very cold temperatures and magnets. The article had a link to a much
better article in Science Mag [1] with more information about how neutrons are
trapped.

[1]
[https://science.sciencemag.org/content/360/6389/627](https://science.sciencemag.org/content/360/6389/627)

------
fnord77
so could we communicate with this mirror universe using the particles that
cross over?

~~~
Finnucane
If our scientists are trying to inject neutrons into a mirror universe, are
mirror-world scientists trying to inject neutrons into ours? Could we detect
that if they did?

~~~
k_sze
Reminds me of the "Fringe" TV series.

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nullsmack
They can stop searching, we're it.

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rbreve
This means the mirrored universe is looking for us too

~~~
magduf
They might have already found us, and realized that we were the "evil twin"
universe where humans are malevolent, and have decided to avoid all contact
with us.

~~~
tabtab
Does that universe have JavaScript?

------
rjf72
The most intriguing about stories such as this is that our own ignorance on
topics such as e.g. dark matter will, at some point in the future, be
something a fresh grad will look back on with bemusement - how could we not
possibly have managed to discover [x] as it gradually comes to be seen as self
evident? This is long since the case for Newtonian mechanics which are now the
domain of secondary education, and is already starting to become the case for
relativity for those of sufficient education.

It's kind of an interesting thought experiment to try to put yourself in the
mindset of a people before the discovery of something and trying to imagine
how you would have perceived the world and if you yourself might have
conceived of such notions. For instance the idea that all objects fall at the
same rate of speed is something that's oddly enough an extremely recent
discovery. The tale of the apple falling on Newton's head dates to but 350
years ago. We, of today, are separated by then by little more than about 4
lifetimes.

It feels at times that science progresses through 1% genius and 99%
creativity. Newton's gravity is, relative to the times, no more simple or
complex than Einstein's gravity and undoubtedly whatever we may eventually
find to be the source of dark matter. The tricky part is that the universe has
this habit of requiring us to cast aside what we think we know and look
towards paths that seem insane. A feather falls at the same rate of speed as a
bowling ball? Time itself can move differently for people in the same location
based upon their relative velocities? Physical distances can literally
contract or expand again for people in the same location and again based on
their relative velocities? Objects themselves can bend what seems to be
emptiness and, in turn, bend light itself (to say nothing of also having an
impact on time)? These ideas are mostly so difficult to develop not because of
mathematical or technical problems, but because they sound insane. It's really
quite a blessing for the inquisitive and creative that we seem to live in a
universe that prides itself in as being as defiant of intuition as it possibly
can.

~~~
YayamiOmate
I doubt that anything like that will become standard curriculum. Some
conclusions and effects might become common knowglede, but the mechanisms and
theory not.

It would have to be taught in high scholl, and even then not everyone have a
complete high school knowledge. People don't generally know Newtonian
mechanics unless they are physics undergrads or graduates. You need calculus
to get it.

I would argue that Newton's theory was more complex because it required new
math. Einstein didn't. The math was already there, and he managed to incept
his idea without it. Riemannian geometry just simplified description. It's
similar to Maxwell. He had electromagnetism in over 20 equations, then some
lad whose name I forgot, made work and closed it down to four, that again 99
percent or more people don't know, though they govern nearly everything at our
scale. Touch, vision and chemistry is described by them. I can come with only
two things that are part of everyday life, that lie outside. Gravity, in the
part that makes us stick to the planet, and atomic energy, though that's fast
trasformed back to EM domain. Everything else seems to be far away, except for
the fact they make things stable, but we don't harness it.

To me ingenuity and creativity are essentially the same. It's the abilty to
have those insane ideas, perhaps genius is to pick important ones to ponder
upon. I think we agree, that scientific breakthroughs seem to be based on
making up grander picture, where what you physically see is some kind of
special case of generally opposite rules. One of the greatest example is the
idea that movement is generally self sustained, seems crazy here in the
atmosphere, where the 1st theories said, that it requires force and work to
keep going. Something we all experience.

Well, that's a long tought-chain. Hope someone's find it interesting.

~~~
gmueckl
When pondering progress in physics, do not underestimate the role of
technological progress and the impact that has on experimental evidence, which
are at the heart of all grest theories. These would not have been dreamt up
without certain experimental data as the starring point for a new explanation.

Quantum mechanics required the weirdness of the blackbody radiation spectrum
to spring to life. The special theory of relativity is based on the
observation that the Maxwell equations are not Galileo invariant and the
results of their strange Lorentz invariance can be observed. The general
theory of relativity is baed on the realization that despite efforts to
measure a difference, inertial mass and gravitational mass always have the
same value.

It took time for these things to become measurable and to make people go
"hmmm..." and think about nature in new ways. The answers are creative and
genial, but they required starting points. And creating those takes time.

------
nabla9
The article may sound like promotion for some TV-series but this is not
related to experiments done in the Hawkins National Laboratory in the 80s.

As I understand it, this mirror world would be colder than our own and this
would affect nucleosynthesis in the early universe. There would be
significantly more helium and less heavier particles. Because the mirror
universe is connected to our universe trough gravity, we would definitely
notice is dark matter stars and planets would go buy. Our universe would have
more dense points of matter and the mirror universe would have more light gas
clouds circling roughly at the same area as galaxies in our world.

~~~
Causality1
Why do you think any of that? A hotter early universe would produce more
helium, not less, and at the cost of hydrogen, not heavy elements. Not only
were heavy elements effectively not produced by the big bang but even now make
up an utterly insignificant portion of the universe.

~~~
nabla9
Maybe I'm wrong. I'm just referring to what others have said written about
this mirror universe theory. I'm not a particle physicist nor do I have
original ideas about this subject.

Here is a paper from 2000 "The Early Mirror Universe: Inflation, Baryogenesis,
Nucleosynthesis and Dark Matter" [https://arxiv.org/abs/hep-
ph/0008105](https://arxiv.org/abs/hep-ph/0008105)

