
Exotic Physics Phenomenon Involving Time Reversal Observed for First Time - lelf
https://scitechdaily.com/exotic-physics-phenomenon-involving-time-reversal-observed-for-first-time/
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BurningFrog
Maybe it can be observed even earlier as technology develops :)

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nprateem
They actually discovered it next year :-D

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hnick
Not for long!

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qeternity
Noob here: this doesn’t actually mean that time was reversed, rather that this
phenomenon was effectively created in reverse order no?

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empath75
I’m not a physicist, but in general, Abelian means that operations in an
algebra commute, while Non Abelian means that they don’t, which is to say that
Abelian means that a+b=b+a

To give a non mathematical example of a non-Abelian algebra, think of a
Rubik’s cube where moves are the ‘numbers’ and composition of moves is the
operation.

If you turn the right face clock wise and then turn the top face counter
clockwise, that does not produce the same state as turning the top face
counter clockwise and the turning the right face clockwise (try it out if you
have one handy). Solving the cube in general requires exploiting this property
by using what are called commutators, which are performing a move and then
another move and then reversing the second move and reversing the first move.
If it were Abelian, then that would leave you in the place where you started —
which is to say you reversed time — but the state will actually have changed
where the first and second move manipulated the same pieces — which makes it
non Abelian and breaks ‘time symmetry’

So in this case, think of some physical operation that changes the state of
the object somehow as being the same as a Rubik’s cube move, and assuming the
operations have an inverse, that performing a commutator where you do one
operation and then another and then invert the second and then the first, that
leaves you in a new state, which would not be the case if it were time
invariant.

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solinent
Great explanation, small nitpick: in mathematics, if you leave a person's name
uncapitalized it's actually a sign of respect. So we usually use the
uncapitalized abelian to refer to groups which commute.

edit: This is done consistently, and I think abelian is one of the few
examples. I've never seen it capitalized before, which is why I made this
post.

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leereeves
I agree that "abelian" is often uncapitalized, but if that's a sign of
respect, why is Gaussian (Gaussian elimination, Gaussian distribution,
Gaussian process, etc) almost always capitalized? Or Hilbert space, Poisson
distribution, Bernoulli trial, Cartesian coordinates, Euclidean distance?

It seems to me that Abelian goes uncapitalized because few people know about
Niels Henrik Abel, and it should properly be capitalized.

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magicalhippo
Found this interesting MathOverflow question with some interesting possible
answers. Not sure if it clears it up much, but the difference between English
and French capitalization rules seems to me like it might have something to do
with some of it.

[https://mathoverflow.net/questions/44946/why-is-abelian-
infr...](https://mathoverflow.net/questions/44946/why-is-abelian-infrequently-
capitalized)

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sidcool
I have always struggled with understanding time in the context of the
universe. Why would the universe care for our conception of time?

It obviously cares, because time slows down at high speeds and in
gravitational dilation. I can't wrap my mind around it.

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danbruc
Our conception of time is just totally wrong, or at least this is true for
99.9 % of all humans and that is certainly an underestimate. Something like
THE time does not exist, we are just all living together in a small bubble in
the universe, all of us experiencing more or less the same gravitational
field, all of us moving together at more or less the same speed as Earth moves
through space, and that is what makes it look like there is THE time. But
actually time is more like counting the calories you burn as you walk through
the world, it is specific to you and the path you take. There is a great
lecture »The Physics and Philosophy of Time« by Carlo Rovelli [1] aimed at the
general public that does a good job pointing out how wrong we are.

[1]
[https://www.youtube.com/watch?v=-6rWqJhDv7M](https://www.youtube.com/watch?v=-6rWqJhDv7M)

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dkarbayev
If the time does not exist, such measure as speed wouldn’t make any sense,
would it?

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elteto
But it doesn't make sense. OP is saying that there is no absolute measure of
time, it depends on the frame of reference of the observer. Therefore there is
also no absolute measure of speed.

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dhimes
Correct. A fly on the seat of your car travels 0 m/s with respect to the car
and to you, but travels, say, 30 m/s with respect to the road. Speed (and
velocity, for that matter) always needs a reference to be meaningful.

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leereeves
arXiv link:
[https://arxiv.org/abs/1906.03369](https://arxiv.org/abs/1906.03369)

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imvetri
Playing a video in reverse is time reversal.

I'm sorry, I cannot really appreciate anything that plays with time and space.
These are metrics to measure. I'm really not sure we can apply any thought
process to imagine time reversal.

We can only imagine time reversal but that exists only in the mind not outside
the head.

Another anology I would like to use "I have 100 litre of water, and I found a
way to double it, compress it while keeping the mass volume unchanged".

That's how anything with space / time reversal / space wrap travelling machine
all sounds!.

Stop encouraging these kind of flawed theories.

Spacetime is a unit, I cannot stand researchers providing theoritical proof
that spacetime is flexible etc etc.

If I have a graph sheet with me and If I stick one edge to another edge
drawing on the graph remains the same!

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not_a_cop75
Clickbait, but thanks for playing.

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jjtheblunt
Would time reversal violate the law of thermodynamics about entropy never
decreasing?

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namirez
Probably not! The 2nd law of thermodynamics is a statistical law describing
the interactions of many particles, so it doesn't necessarily apply to
microscopic scales.

[https://www.newscientist.com/article/dn2572-second-law-of-
th...](https://www.newscientist.com/article/dn2572-second-law-of-
thermodynamics-broken/)

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saul_goodman
"To produce the effect, the researchers use photon polarization. Then, they
produced two different kinds of time-reversal breaking. They used fiber optics
to produce two types of gauge fields that affected the geometric phases of the
optical waves, first by sending them through a crystal biased by powerful
magnetic fields, and second by modulating them with time-varying electrical
signals, both of which break the time-reversal symmetry. They were then able
to produce interference patterns that revealed the differences in how the
light was affected when sent through the fiber-optic system in opposite
directions, clockwise or counterclockwise..."

Lordy, I with these folks would speak english, but no, whats really important
is saying things in a way only others in your field can comprehend. You can
actually comprehend papers written even just 50 years ago because they written
to be understood, not to confuse the granting body.

TL;DR: they setup a laser interferometer and twiddled the light in different
ways through each path, the resulting interference pattern was evidence of the
effect claimed.

On one path they polarized the light by running it through an LCD (a "crystal
biased by powerful magnetic fields"). On the other path I'm less sure what
they mean by "time-varying electrical signals", probably just means they were
effectively pulsing it on and off. And somehow, by running each path through
opposing winds of a fiber optic system they think they are getting results
indicating "time reversal". I'll have to take them on their word on that,
that's where I know less about the subject matter.

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fourthark
I prefer accurate reporting that I don't understand, to the usual
oversimplified and overhyped nonsense that usually passes as science
reporting.

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comboy
Not sure if it's the first time, we still seem to have a lot to learn about
how time and causality works:
[https://www.youtube.com/watch?v=8ORLN_KwAgs](https://www.youtube.com/watch?v=8ORLN_KwAgs)

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maitredusoi
at least !!!!

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bpaddock
There are lot of examples, studies and experiment on retro causality in the
field of Parapsychology. So this is not at all 'the first'.

"Time-reversed human experience: Experimental evidence and implications" by
Dean Radin is one that happens to be laying on my desk right now.

A new book by by Theresa Cheung and Julia Mossbridge, "The Premonition Code"
gets into some of the science. Ms. Mossbridge has published several papers and
a few YouTube Videos about 'Time'.

The field of Parapsychology generally gets dismissed to easily. The top people
know they will get criticized, so they tend to design their experiments and
statistics to standards higher than most if not all fields of study. If
Parapsychologist presented the data that was given as 'Proof' of the Higgs
boson, as shown by a small statistical bump in the data, they would have
gotten their ass handed to them had they presented the same data has proof of
any of their experiments.

Optical Phase Conjugation is also interesting in that it involves apparent
negative time. Let you do things like a see through frosted glass. True Hacker
material...

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gameswithgo
is the james randi prize still available? that frosted glass trick would be an
easy million dollars

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lpellis
Unfortunately not, ended a few years ago and the money was repurposed I assume
for other ventures. I guess its hard to keep that price going, you need
skilled people (like Randi) that knows the usual tricks.

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bpaddock
You also need to have objective people, unlike Randi.

One lady did keep passing all of his tests, all day long, so they keep
fiddling with the test to "improve it". Until the lady was completely
exhausted and failed the test. Guess which test result they used?

After this no one took Randi seriously, so no one with skill bothered.

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SketchySeaBeast
Do you have a link for that? That's very much different from how I understand
the tests were undertaken, so I'd be very interested in reading about it.

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SuoDuanDao
Not familiar with that story, but here's a scientist's response to one of
Randi's rebuttals.

[https://www.sheldrake.org/reactions/james-randi-a-
conjurer-a...](https://www.sheldrake.org/reactions/james-randi-a-conjurer-
attempts-to-debunk-research-on-animals)

Randi's the worst kind of enemy science can have, someone who violates every
principle of scientific inquiry for the sake of his own dogma, while claiming
to care about the integrity of science.

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SketchySeaBeast
You're claiming that a professional magician is a bad scientist? He's an
entertainer and not a trained scientist.

Here's a statement from Randi about the dog ESP:

“I over-stated my case for doubting the reality of dog ESP based on the small
amount of data I obtained,” he wrote. “It was rash and improper of me to do
so. I apologise sincerely.”[1]

Sounds like he's willing to revisit his initial claims. Has there been further
evidence of dog esp that you're aware of?

[1] [https://www.telegraph.co.uk/culture/film/film-
news/11270453/...](https://www.telegraph.co.uk/culture/film/film-
news/11270453/James-Randi-debunking-the-king-of-the-debunkers.html)

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SuoDuanDao
>"I apologize sincerely"

As sincerely as when he said he'd replicated the experiment no doubt. And if
he isn't capable of reproducing an experiment, what the frack was the prize
supposedly for? I don't think he'd be capable of sincerity if he tried.

As for your other question, I saw a response Sheldrake posted about someone
else's rebuttal stating that if the rebuttal's raw data were analysed the way
his data was, it would have led to the same conclusion. That the attempt at
replication looked at the first time the dog went to the window, rather than
the average time it spent at the window. Don't have a link right now though.

Dog ESP is a pretty niche experiment though, I just brought it up because it's
one of the more egregious lies Randi was caught in. If you're interested in
psi data, there are much larger datasets with experiments into ganzfeld and
skin conductivity precognition.

