Scientists Break the Direction of Time Down To the Cellular Level In Mind-Bending Study (vice.com) 73
A new study looks at interactions between microscopic neurons in salamanders to understand how the "arrow of time" is biologically generated. Motherboard reports: The second law of thermodynamics says that everything tends to move from order to disorder, a process known as entropy that defines the arrow of time. A stronger arrow of time means it would be harder for a system to go back to a more ordered state. "Everything that we perceive as a difference between the past and the future stems fundamentally from that one principle about the universe," said Christopher Lynn, the lead author of the study. Lynn said that his motivation for the study was "to understand how the arrows of time we see in life" fit into this larger idea of entropy on the scale of the entire universe.
Using previously done research on salamanders, Lynne and colleagues at City University of New York and Princeton examined how the arrow of time is represented in interactions between the amphibians' neurons in response to watching a movie. Their research is soon to be published in the journal Physical Review Letters. On one hand, it's somewhat obvious that an arrow of time would be biologically produced. "To be alive, almost, you have to have an arrow of time because you develop from a baby to an adult, and you're constantly moving and taking in stimuli," Lynne said. Indeed, entropy here is irreversible -- you cannot go back. What the team found was anything but intuitive, however.
Lynne and colleagues looked at a separate 2015 study where researchers had salamanders watch two different movies. One depicted a scene of fish swimming around, similar to what a salamander might experience in everyday life. As in the real world, the video had a clear arrow of time -- that is, if you watched it in reverse, it would look different than if you played it forwards. The other video contained only a gray screen with a black, horizontal bar in the middle of the screen, which moved quickly up and down in a random, jittery way. This video didn't have an obvious arrow of time. A major question for the researchers was if they could pick out signs of "local irreversibility" in interactions between small groups of retinal neurons in response to this stimulus. Would interactions with irreversibility -- they would look different if played in reverse, having an "arrow of time" -- present in simpler or more complex interactions between neurons? "You can go look at a system and you can ask: are the more complicated interactions strongly producing the arrow of time, or is it the simpler dynamics?" said Lynn.
The researchers found that the interactions between simple pairs of neurons primarily determined the arrow of time, no matter which movie the salamanders watched. In fact, the authors found a stronger arrow of time for the neurons when salamanders watched the video with the gray screen and black bar -- in other words, the video without an arrow of time in its content elicited a greater arrow of time in the neurons. "We naively thought that if the stimulus has a stronger arrow of time, that would show up on your retina," said Lynn. "But it was the opposite. So that's why it was surprising to us." While the researchers can't say for sure why this is, Lynn said that it might be because salamanders are more used to seeing something like the fish movie, and processing the more artificial movie took greater energy. In a more disordered system, which would have a greater arrow of time, more energy is consumed. "Being alive will still define an arrow of time," Lynne said, no matter the stimulus.
Using previously done research on salamanders, Lynne and colleagues at City University of New York and Princeton examined how the arrow of time is represented in interactions between the amphibians' neurons in response to watching a movie. Their research is soon to be published in the journal Physical Review Letters. On one hand, it's somewhat obvious that an arrow of time would be biologically produced. "To be alive, almost, you have to have an arrow of time because you develop from a baby to an adult, and you're constantly moving and taking in stimuli," Lynne said. Indeed, entropy here is irreversible -- you cannot go back. What the team found was anything but intuitive, however.
Lynne and colleagues looked at a separate 2015 study where researchers had salamanders watch two different movies. One depicted a scene of fish swimming around, similar to what a salamander might experience in everyday life. As in the real world, the video had a clear arrow of time -- that is, if you watched it in reverse, it would look different than if you played it forwards. The other video contained only a gray screen with a black, horizontal bar in the middle of the screen, which moved quickly up and down in a random, jittery way. This video didn't have an obvious arrow of time. A major question for the researchers was if they could pick out signs of "local irreversibility" in interactions between small groups of retinal neurons in response to this stimulus. Would interactions with irreversibility -- they would look different if played in reverse, having an "arrow of time" -- present in simpler or more complex interactions between neurons? "You can go look at a system and you can ask: are the more complicated interactions strongly producing the arrow of time, or is it the simpler dynamics?" said Lynn.
The researchers found that the interactions between simple pairs of neurons primarily determined the arrow of time, no matter which movie the salamanders watched. In fact, the authors found a stronger arrow of time for the neurons when salamanders watched the video with the gray screen and black bar -- in other words, the video without an arrow of time in its content elicited a greater arrow of time in the neurons. "We naively thought that if the stimulus has a stronger arrow of time, that would show up on your retina," said Lynn. "But it was the opposite. So that's why it was surprising to us." While the researchers can't say for sure why this is, Lynn said that it might be because salamanders are more used to seeing something like the fish movie, and processing the more artificial movie took greater energy. In a more disordered system, which would have a greater arrow of time, more energy is consumed. "Being alive will still define an arrow of time," Lynne said, no matter the stimulus.
Skipping TFS/A ... (Score:1)
Scientists Break the Direction of Time Down To the Cellular Level
LTE or 5G -- or that AT&T 5G E?
[ Oooo is it T-Mobile's 9G [gsmarena.com]? :-) ]
Wen.. (Score:3)
'I know that time was made for men, not the other way round. I have learned how to shape it and bend it. I know how to make a moment last for ever, because it already has. And I can teach these skills even to you, Clodpool. I have heard the heartbeat of the universe. I know the answers to many questions. Ask me.'
The apprentice gave him a bleary look. It was too early in the morning for it to be early in the morning. That was the only thing that he currently knew for sure. 'Er ... what does master want for breakfast?' he said.
Wen looked down from their camp and across the snowfields and purple mountains to the golden daylight creating the world, and mused upon certain aspects of humanity. 'Ah,' he said. 'One of the difficult ones.'
Re:Wen.. (Score:5, Interesting)
Inverse entropy is interesting, but at best just an intellectual curiosity. [smbc-comics.com] It could never be practical.
Re: (Score:2)
definitions.
our very definition of time is flawed.
but it is to easy to measure inertial vectors using a variable called
time
Re: (Score:2)
our very definition of time is flawed.
Well what definition of time do you think we are using, and what definition do you prefer?
Re: Wen.. (Score:2, Interesting)
I think they are referring to special relativity, the idea that the passage of "time" is constant. While the general understanding is time is only not constant this way at high speeds or involving large masses, it does beg a question if there are other ways this constant passage of time breaks down.
For instance, Light travels as a set speed and for all intensive purposes cannot be slowed down, right? Yet we have ultraslow light which is achieved by using a BEC. They even stopped light in these which I only
Re: (Score:2)
For instance, Light travels as a set speed and for all intensive purposes cannot be slowed down, right?
Wrong. Light travels at a set speed through a particular medium. Change the medium, change the speed. This is what refraction is -- bending light by changing the speed by changing the medium it travels through.
Re: (Score:2)
Light travels at c, period. It only slows down when there's no direct path available to it. If the photons have to bounce around between atoms in a medium, then of course they will appear to slow down. They are not slowing down at all; they're just taking longer paths.
Re: (Score:2)
When a photon strikes an atom within a transparent medium, it is absorbed and then an identical photon is re-emitted after a short delay. Because of conservation of momentum, its direction is the same as before. Between atoms, the photon still travels at c but because of the delays, it'll appear as if it's moving slower. The path of the photon (or a series of identical photons) in a medium like glass is still more or less a straight line, otherwise you wouldn't perceive the glass as being clear.
Re: Wen.. (Score:2)
The whole comment chain still doesn't explain how researchers have stopped light. More to the point they say they are interacting with the light, so if it's stuck in a medium waiting to be Re-emitted, how are they doing that.. Again the medium would need to approach infinite density for this outcome given these explanations.
However, in my reading, I don't see how long the light was stopped. Sufficient density and reducing that time of re-emitting the particle, should give apparent lack of motion but there w
Re: (Score:2)
This might help explain:
https://www.extremetech.com/extreme/162289-light-stopped-completely-for-a-minute-inside-a-crystal-the-basis-of-quantum-memory [extremetech.com]
This also proves that boredom is harmful. (Score:5, Insightful)
If the salamanders are expending more energy in the same place with the same physical stimuli and it's just through their eyes as a visual stimuli, then what you're saying is that by boring them, their brains took up more energy and that may have actively harmed them.
You're putting them through more stress and making their body work harder.
You just proved that boredom in the intellectually capable can create PTSD or other mental health issues, right?
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I interpreted it instead as trying to figure out and learn patterns of unfamiliar stimuli. Fish are too familiar to them to trigger the "learning stress".
In other words, a mind works harder in WTF mode.
Why the backward fish didn't trigger the WTF mode itself is a WTF, or should I say FTW.
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No, that's not at all what this is saying, and I'm not sure how you managed to come up with that.
If anything, you would argue the opposite. More energy was utilized by the brain when confronted with the novel image. But nothing suggests anything about it "may have actively harmed them".
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Well, making the mitochondria work harder causes more oxidative stress, and that's usually considered harmful. (The exceptions I can think of involve the immune system using it to kill something undesired off, and that doesn't exactly refute the point.)
Still, that could be restated as "metabolism considered harmful", which makes me want to ask "compared to what?".
termodynamics and quantum theory (Score:2)
It just occurred to me that a sufficiently long-leaving entity would be immortal due to quantum effects of statistically recycling thermodynamic states even with lower entropy.
First study in history.... (Score:5, Funny)
.... in which the first entry in the list of citations is the pager number of the principal investigator's weed dealer.
Maybe (Score:2)
Isn't that a bit redundant? (Score:1)
Re: (Score:2)
Well, saying that an entire systems (no externalities) moves from order to disorder is one definition of time. But that "no externalities" makes it difficult to measure.
Well, if no one else will do it... (Score:5, Funny)
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True. It is hard to wreck a nice beach.
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Wouldn't it be better to say that bananas fly like fruit, since strictly banana is the subset?
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<woosh>
oh dear.
</woosh>
</woosh>
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Wouldn't it be better to say that most know species of time flies prefer to eat wood, since that's really the only part of the arrow that a time fly likes to eat?
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Or maybe... (Score:5, Insightful)
The reaction of the salamanders had nothing to do with the "arrow of time." We know that animals don't react to videos in the way humans do. Some dogs and cats do react to movies about other animals, but for some, it's just background noise. Perhaps for these animals, the images on the screen don't register as anything interesting because they have no smell, an important part of their sensory perception.
Salamanders likely have even more limited perception of what's happening on a video screen. We know from studies of neural networks, that an untrained network produces essentially random output from any input. Since the "training" (instinct) of these salamanders does not associate any meaning to video images, it's hard to assert that the neural-level reactions relate to the "arrow of time."
Re:Or maybe... (Score:4, Insightful)
We know from studies of neural networks, that an untrained network produces essentially random output from any input.
In the days when Sussman was a novice, Minsky once came to him as he sat hacking at the PDP-6.
“What are you doing?”, asked Minsky.
“I am training a randomly wired neural net to play Tic-Tac-Toe” Sussman replied.
“Why is the net wired randomly?”, asked Minsky.
“I do not want it to have any preconceptions of how to play”, Sussman said.
Minsky then shut his eyes.
“Why do you close your eyes?”, Sussman asked his teacher.
“So that the room will be empty.”
At that moment, Sussman was enlightened.
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"At that moment, Sussman was enlightened."
Thats more than I am. No idea what Minksy was getting at, remove its input in order to ..... ?
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If you wire the NN randomly, it still has preconceptions, you just don't know what they are,
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Well it has to be wired somehow or it wont work to start with so sounds like Minsky was full of his usual shit.
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so sounds like Minsky was full of his usual shit.
that damn minksy!
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You are agreeing with Minsky so sounds like you are just as full of shit.
Re: Or maybe... (Score:2)
Ever thought of learning to read? Might help.
A Chuck Norris video would have been better (Score:2)
Chuck decides when neurons move.
Re: A Chuck Norris video would have been better (Score:1)
Uhm, W T F? (Score:1)
The second law of thermodynamics says that everything tends to move from order to disorder, a process known as entropy that defines the arrow of time.
Uhm... no?
Doesn't it seem.... obvious... that if somebody invented a technology that could create order from a disordered system, time would still be flowing in the same direction? The "arrow of time," eg, things can happen, is an unexplained detail of reality that is not in any way based on the 2nd Law of Thermodynamics.
And a movie played "backwards..." is playing forwards in time. D'oh! I don't know whose cousin they are to have had this paper accepted, but if actually gets published it is going to get RE
Re: (Score:3)
Then consider this sentence:
"On one hand, it's somewhat obvious that an arrow of time would be biologically produced. "
Apparently time...didn't exist before biology? It does raise interesting questions. Does that mean there is no time on Jupiter? Or that rocks exhibit no time?
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That depends on what he meant. If by "arrow of time" he was referring to an internal model of events, then it would be biologically produced, even though time happened anyway.
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No, it means that the direction of time is something biologicals perceive because biology is based on reactions that proceed in a certain direction.
Time could more abstractly be seen as a dimension without a fundamental difference between forward and backward. Consider a page of text, read from top to bottom. Perhaps the content of each line of text is based on the previous line, so from the point of view of a line of text the previous line is considered "past" and the next one is "future". But a person loo
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Time could more abstractly be seen as a dimension without a fundamental difference between forward and backward.
I don't think it can.
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Time could more abstractly be seen as a dimension without a fundamental difference between forward and backward. Consider a page of text, read from top to bottom. Perhaps the content of each line of text is based on the previous line
That seems like an... easily tested hypothesis. I suspect that you can that exact experiment described in pre-Socratic works...
Re:Uhm, W T F? (Score:4, Informative)
Doesn't it seem.... obvious... that if somebody invented a technology that could create order from a disordered system, time would still be flowing in the same direction?
Yes, but no.
You cannot make such a machine. It is unphysical. A machine, ANY machine will produce more entropy than order, always.
Sure, you can direct and concentrate the order so that you can use it, but your machine will still be dumping more disorder into the environment than it produces order for you to use.
So yes, time will always flow one way. But no, you couldn't make a machine that produces order that doesn't also produce even more disorder.
And if you somehow managed to build such a machine then congrats, you have debunked the highest, most prevailing principle we find in the universe.
The "arrow of time," eg, things can happen, is an unexplained detail of reality that is not in any way based on the 2nd Law of Thermodynamics.
Sure, it's the other way around. The 2nd law of thermodynamics is based on the notion that time has a direction.
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The "arrow of time," eg, things can happen, is an unexplained detail of reality that is not in any way based on the 2nd Law of Thermodynamics
The 2nd law of thermodynamics is based on the notion that time has a direction.
Hmm...
And yet, there definitely are schools of thought that suggest that it is due to the 2nd law that time has a direction, so both you and the OP are, at least partially, wrong about that. I make no comment on the correctness of these, or your, schools of thought, merely your (implicit or explicit) claims that they don't exist.
I will say though, that the 2nd law is only truly applicable when considering a closed system. Now all we have to consider is if there is such a thing...
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And yet, there definitely are schools of thought that suggest
So? The mere existence of "schools of thought" does not change the scientific consensus. There are numerous routes to arriving at the 2nd Law without leaving any accepted, consensus theories. So there is no need at all to appeal to weird fringe theories about a hidden clockwork.
the 2nd law is only truly applicable when considering a closed system. Now all we have to consider is if there is such a thing...
Consensus is that the Universe is a closed system. My "school of thought" is that that is not demonstrated, and probably not true. That's the problem with using "schools of thought" as a basis of negative proof. It makes it impossibl
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That's the problem with using "schools of thought" as a basis of negative proof. It makes it impossible to talk about anything.
Impossible to arrive at a conclusion both 'sides' can agree on, perhaps, but I'd say this thread provides proof that it's possible to talk about this stuff.
So? The mere existence of "schools of thought" does not change the scientific consensus. There are numerous routes to arriving at the 2nd Law without leaving any accepted, consensus theories. So there is no need at all to appeal to weird fringe theories about a hidden clockwork.
I think in my haste to play devil's advocate to the OP my comments might have lacked a certain substance. It is true that the 'consensus' view is that entropy requires an (thermodynamic) arrow of time. Given that the 2nd law deals with entropy this means that, as the OP stated, the 2nd law is based on the arrow of time. So far so good. My 'reversal' of t
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You cannot make such a machine. It is unphysical. A machine, ANY machine will produce more entropy than order, always.
That is a basic misunderstanding of the 2nd law.
Even in the summary, they get that part right:
The second law of thermodynamics says that everything tends to move from order to disorder
You don't get this "unphysical" bullshit out of "tends to."
The reality is that the complete lack of any theory on how to reverse entropy, and the lack of examples that have been found in nature to reverse entropy, leads to the 2nd Law, which is not actually a law but merely a consistent observation that is believed to be impossible to avoid. But there is no basic principle, no physical force, that prevents such a m
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The reality is that the complete lack of any theory on how to reverse entropy
But there are plenty of theories to reverse entropy. Locally.
It isn't "unphysical" or "unpwossuble" or any other silly bullshit.
Oh, well, good luck, you'd certainly get a Nobel Prize if you found a way!
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The reality is that the complete lack of any theory on how to reverse entropy
But there are plenty of theories to reverse entropy. Locally.
You're just passive-aggressively pretending that somebody didn't understand that. It's just a shy pejorative from an asshole.
You were playing that 'that's unpwossuble so I'm sciencey' game. That's Elmer Fudd territory. You shouldn't have gone there, you were wrong, get over yourself. You're not sciencerific. You don't have any idea what is unpwossuble.
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It's just a shy pejorative from an asshole.
Aah, i see. Very sciency. Very sciency indeed...
That's Elmer Fudd territory.
A grand argument. I bow my head.
You shouldn't have gone there, you were wrong, get over yourself.
What masterful prose.
You're not sciencerific.
Again, i congratulate you on your fine reasoning.
You don't have any idea what is unpwossuble.
Ooh, the finale! How thrilling to see everything come together!
This may be too much science for me tho. So many sound arguments. I'm not sure my Elmer Fudd brain can contain it all.
Arrow Of Time (Score:3)
Adrian the salamander stepped into the Quantum Leap accelerator and disappeared...
Let the salamanders watch (Score:1)
...salamander porn. Chimps like to watch chimp-porn, so I wonder how far down the brain size chain porn enjoyment goes.
Whose job was it to video chimps doin' it anyhow? Did they advertise for that job? And it didn't trigger the spam filters?
Biologists overreaching much? (Score:3)
They should stick to torturing animals to death for fun and profit.
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Its a good example of experts in one field thinking they're clued up about another when in actual fact they're no more clued up than the average joe.
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Or you are misunderstanding what they said. The "arrow of time" can be considered distinct from time, and there are multiple ways of modeling just what that phrase means. Some of which make perfect sense in this context.
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i think most people here thought that "arrow of time" was meant in the physics sense, not the "perception of time" biological/neurological sense.
and there are multiple ways of modeling just what that phrase means
but only a few ones that make sense because everyone else is also using them
Uncertain Bedrock (Score:2)
The experiment relies on the assumptions of experimenters for "...similar to what a salamander might experience in everyday life". That's somewhat uncertain footing, is it not?
Embarassing or Ridiculous? (Score:4, Insightful)
Biology used to be collecting (capture+kill) but now is mostly about experimenting (torturing) on models (animals) with bizarrely sketchy assumptions.
Primary conclusion from the experiment: "We don't really understand how neurons work nor physics concepts like entropy." Something that should have been known before they were given money and the go-ahead on the experiments.
About biology: it has no first principles like say, physics, from which to formulate theories of expected cellular behaviour let alone something as 'meta' and beyond their education as 'entropy' and 'time'. More profoundly, and alluded to in the experimenter's comments, they don't know anything about salamander perception. The tacit assumption is that it must be like human perception but how likely is it that a reptile perceives the world as humans do? Or putting it in human terms, let's say you were shown two videos but one of them was utterly beyond your comprehension and experience in every way (visual, olfactory, tactile, etc). Would someone observing you be able to draw a conclusion about your experience of ... time?
Re: Embarassing or Ridiculous? (Score:2)
Salamanders are amphibians, not reptiles.
(cf. Skitt's Law)
Seems like low quality research (Score:4, Interesting)
At least from the summary, I feel like there's a lot of reaching and room for rationalization.
They collected some sort of data about activity, and then extrapolated that this specifically must be some "arrow of time" and then when the activity they went to measure actually increased in response to random synthetic stimulus contrasted to orderly stimulus, they double downed and said they must just be using more energy because the 'arrow of time' is not so clear.
They measured some neural activity that increased when faced with weird synthetic movie instead of fish. You can say all sorts of things, I don't feel like they convey how that vague observation translates into a very specific 'arrow of time' concept.
So, to paraphrase... (Score:1)
Job Title: Salamander Media Navigator (Score:1)
Which time? (Score:1)
Are we measuring entropy based on space time time or quantum number of oscillations required to travel over a distance time.
Since both of these are increasing the entropy is likely to increase so there is nothing special about our perception of time as our perception of time is built on top of systems that encapsulate the effects of time.
...What in the shit is this? (Score:2)
I won't even stoop to discussing the content of this embarrassing drivel. I feel slightly dumber just for having read the summary.
What's "mind-bending" to me is that someone with posting privileges on Slashdot *actually thought this was worth posting.* Seriously, "biological processes *create time*"? Wow, yeah! Sounds legit, and totally worthy of the attention of a group of intelligent people coming here to read serious science news! The world must know right away that Einstein, Hawking and every other reno
sole stimulus (Score:2)
Not looking deeply enough (Score:2)
"...you have to have an arrow of time because you develop from a baby to an adult"
If you don't recognize this statement as a tautology you're not ready to be researching the subject.
This Is Silly (Score:1)
So basically, fish are more familiar? (Score:1)
Can we stop funding this kind of study, please? It very obviously has no scientific value at all.