Is Time Travel Possible? Part 2

In the last post, I introduced the notion of time travel into the past and pointed out that the potential for a temporal paradox would prevent time travel that allowed changes to the past.  Is it possible, as some have argued, to affect, influence, or participate in the past without changing the past?

No.

First, there is the Butterfly Effect.  You can get the general idea by watching the movie of the same name, but the idea is simple: small events get amplified over time into much larger consequences.  The Butterfly Effect is actually a mathematical result of chaos theory, whereby nonlinear relationships cause effects that seem to be entirely unpredictable over a long enough time period.  Perhaps one of the most fascinating papers I ever read was this one (“Gargantuan chaotic gravitational three-body systems and their irreversibility to the Planck length”), in which the authors show that even the largest objects in the universe are fundamentally unpredictable over a long enough time period.  They analyze initial conditions that are precise down to the Planck length, because that length, according to physicists, is the smallest length that has any possible physical meaning in the universe.  So if precision down to the Planck length can’t predict the motions of supermassive black holes, then nothing can.

The Butterfly Effect is a problem for time travel into the past, and here’s why.  You certainly can’t go back in time to kill one of your ancestors, as that would prevent your own existence and cause a temporal paradox.  But what if instead you did something seemingly inconsequential, but that event caused another event that caused another event… that prevented your own existence.  In the first installment of Back to the Future, Marty pushes his future father out of the road so that he didn’t get hit by a car, but of course that caused a chain of events that led to Marty’s future mother falling for him instead of his future father.

But what about something more subtle?  Say you want to go back in time just to observe your ancestors – you have no intention of killing or even interacting with them.  Say you’re just walking around and watching from a distance.  A malarial mosquito starts buzzing around you and you swat it away.  If you hadn’t been there, it would have just fed on some nearby rat.  But your swatting at it stimulates it; angry and hungry, it flies in the direction of your ancestors and stings one.  Maybe that ancestor dies from malaria before he reproduces.  Maybe he just gets sick and misses his opportunity to mate with the woman who would have been your ancestor.  Or maybe nothing serious happens at all.  Maybe he was already in the middle of having sex with her when he gets stung by the mosquito, and the brief moment he spends smacking the mosquito is enough to change which sperm cell ultimately fertilizes her egg.  That alone would be enough to change the identity of their descendants, and it would (arguably) prevent YOU from existing.

Physicists and philosophers who argue that time travel into the past is possible usually understand the Butterfly Effect and might retort something like, “Time travel into the past is possible as long as you don’t do anything, even something small that could chaotically amplify, that would change the facts of the present.”

Here’s the problem: THERE IS NO EVENT, NO MATTER HOW SMALL OR SEEMINGLY INSIGNIFICANT, THAT WOULD SATISFY THAT REQUIREMENT.

As I discuss in this paper, information in the universe is embedded in the relationships, correlations, and entanglements among and between all the particles and fields throughout the universe.  Whether the amount of information in the universe is constant or changing is a fundamental question.  Those who believe in the assumption of U (that quantum wave states always and universally evolve linearly) believe that the information content of the universe is fixed.  As you know if you read this blog or my papers (such as this or this), I have shown that U is false and that the information content of the universe is increasing – specifically, collapse of the quantum wave state upon irreversible correlation events is what produces new information.  Nevertheless, whether the information content of the universe is constant or changing, we can all agree that at the present moment there is a certain amount of information in the universe (and it is a staggeringly large amount).

In other words, there are a huge number of “facts of the present,” and every one of them correlates to some event in the past.  Every single event in the past gets embedded as a fact in the information structure of the universe.  (Those who believe in U would say that every event in the past is already embedded in the information structure of the universe, both past and future, in a block universe.)

What does this all mean?  Imagine a speck of dust a million years ago that might have flown in direction A or direction B depending, for example, on some quantum event.  There is necessarily some physical experiment that can be done today whose outcome would depend on whether that speck of dust went in direction A or B, whether or not anyone could figure out which experiment to perform.  In other words, that seemingly insignificant event from a million years ago is currently embedded in the information structure of the universe, which means that there is some feature of the universe today that depends on that event.  That feature may (or may not) be small, depending on the extent to which it was chaotically amplified, and it may not even be possible to know what kind of experiment would differentiate that feature.  But the point is that the happening of that event a million years ago MUST be physically embedded in the universe today.  (If it wasn’t, then it didn’t happen – which is the point I’ve been trying to make over and over regarding measurement and physical irreversibility.)

So here’s the problem.  If it was possible for you to travel back in time, even if you tried your best not to change the past, your mere physical presence would be a fact that gets embedded in the future information structure of the universe.  The universe, after all, is constantly measuring you and everything about you.  Trillions of air molecules are bouncing off your body every second.  Infrared radiation (heat) is constantly being emitted and absorbed by your skin.  Even your own minuscule gravitational field causes changes around you that constantly provide evidence of your presence.

Even if all you wanted to do was watch your ancestors in the past, and you were somehow able to send back just your eyeballs (or, even better, a tiny camera[1]), your eyes work by focusing and absorbing photons on your retina, and the FACTS about whether or not particular photons in the past got absorbed get permanently embedded in the universe.  At a bare minimum, in order to see something, you have to change the trajectory and/or presence of photons.  These would constitute events, the occurrence of which would forever affect the universe.

Therefore, there is no way to send anything physical to the past, no matter how small or seemingly insignificant – and thus there is no way to directly observe the past – without affecting the present.  If, for example, it was possible to travel to the past in some kind of super-insulated vehicle that managed to affect nothing in the past, except that it allowed a few photons to be absorbed by your retinas so that you could see something, the facts about the absorption of those few photons would be embedded in the universe in a way that would reveal measurably distinct outcomes at any time after, including the present. 

So here’s what I’ve pointed out so far:

·       You can’t travel back in time to kill an ancestor because this would cause a temporal paradox.

·       You can’t travel back in time to do much at all because, thanks to the Butterfly Effect, almost anything you do will get chaotically amplified over time in a way that somehow prevents your existence or your ability or willingness to travel back in time.

·       Nevertheless, if you did travel back in time (or sent something back in time), even if you did nothing, your very presence in the past would get embedded as permanent facts of the universe.  The way the universe is right now (or 10 minutes ago or 10 years ago) depends on whether you travel back in time.

The last point is key.

Imagine that there is some conscious experience you had 10 minutes ago (at time T) that depended, at least to some small extent, on whether you time traveled to the past.  Assume for simplicity that you observed something as blue – i.e., there is a fact, embedded in the universe, about your conscious experience of seeing blue at time T.  However, if you travel into the past, your mere existence gets embedded in the universe in such a way that, at time T, you instead experience seeing red.  So what did you actually experience?

Some may reply that this is just a case of memory erasure or modification, but in these papers (here and here) I argue that retroactive modification of conscious states is impossible.  I’m not saying someone can’t misremember something.  I’m saying that conscious states are history dependent, that the facts of past conscious states get embedded in future states much as past physical events get embedded in future states of the universe.  If there is indeed a fact about what I am consciously experiencing now, then it evidences facts about previous conscious states.  It is therefore impossible for me to experience my present conscious state (which, indeed, I am experiencing) if my past conscious states are not facts and can instead be retroactively changed.  And because time travel into the past implies the ability to retroactively change my own past conscious states, then it would imply that there is no fact about my current conscious state (and also no fact about the current physical state of the universe).  This is false.

Therefore, time travel into the past in any form, even just to observe it, is impossible.

One nagging objection to the above analysis is this: it all hinges on one’s ability to choose whether to travel into the past.  If there’s no free will, then it is either true or false that I’ve already traveled into the past.  But if I have, then that fact is already embedded in the present universe and there is nothing I can do to prevent myself from traveling into the past.  Of course, I believe that we have free will, but it remains one of the problems I am currently working on.

I’ve said enough for this post.  What other objections or thoughts do you have?

---

[1] But then where would the image information be sent?  On that note, if you were able to send back just your eyeballs to the past without the rest of your body and brain to consciously experience it, then what’s the point?

Is Time Travel Possible? Part 1

Traveling into the Future

We can certainly travel into the future, which is what we are doing right now at the rate of 1 minute per minute.  We can even change that rate.  With drugs or alcohol, we can change the perceived rate in which we travel into the future.  But we can also change the actual rate, relative to others, thanks to Einstein’s relativity.  This is called relativistic time dilation and it is caused by two physical phenomena. 

The first is relative motion (characterized by Einstein’s “special” relativity).  Imagine you and a friend are wearing really accurate and precise watches.  If your friend is moving toward you or away from you at some speed, her watch will tick slower than yours.  However, the effect in our normal everyday world is very, very tiny.  Take the person’s speed, divide it by the speed of light, then square that result, and that’s the approximate effect.

For example, let’s say your friend is jogging toward you at 3 meters per second (which is almost 7 miles per hour).  Divide that by the speed of light (about 300,000,000 meters per second), and then square that result, and you get 10^-16, or 0.0000000000000001.  So for every second your watch ticks, your friend’s watch will tick 100 billionths of a billionth of a second slower.  Imperceptible.  However, if your friend could approach the speed of light relative to you, then her watch would slow down significantly relative to yours.  In fact, if she zoomed away at near the speed of light for long enough, then turned around and returned to Earth, she might have aged only a few months while you aged a few years or longer.

The second phenomenon is gravity (characterized by Einstein’s “general” relativity).  Time slows inside a gravitational potential well.  For example, time ticks slightly slower on the surface of the earth than in outer space, which is why GPS satellites must account for this tiny effect to stay accurate.  The stronger the gravity field, the stronger the time dilation.  A great example was in the movie Interstellar in which the crew lands on a planet closely orbiting a supermassive black hole, leaving one crew member in the mother ship much further from the black hole.  The crew on the planet felt time passing normally, but when they returned to the mother ship, they realized that their hour on the planet had corresponded to many years passing for the crew member on the mother ship.

These things are certainly interesting to think about, but the technology does not exist – and may not ever exist – that will allow humans to experience significant time dilation.  Yes, time dilation is real and we have to account for it in GPS satellites, nuclear reactors, and particle accelerators, but will we ever have the technology to accelerate a human to near the speed of light (relative to another human)?  Probably not.  So while possible in principle, time travel into the future through use of relativistic effects will probably remain science fiction.

Traveling into the Past

The far more interesting question, and the one that most people wonder regarding time travel, is whether it’s possible to travel into the past.  We all want to be Marty McFly (or Doc Brown, depending on your personality), with the freedom to see the past, experience the past, and even change the past.

Lots of reputable physicists, like Nobel Prize winner Kip Thorne (author of Black Holes & Time Warps), claim that the laws of physics allow for time travel into the past, and even suggest fascinating ways of doing so, like stretching open and passing through wormholes.  (Note: wormholes are theoretical predictions and there is exactly zero empirical evidence that they exist.  Even if they could exist, there is no good reason to believe that we could ever create them at will, engineer them to specifications, choose their endpoints in spacetime, stretch them open, or pass matter through them.  They are, purely and simply, science fiction.)

The obvious problem with time travel into the past is the risk of a temporal paradox.  For example, what would happen if you killed your ancestors?  If you did, then you couldn’t be born, which means you couldn’t go back in time to kill your ancestors.  Doesn’t that problem by itself rule out time travel into the past? 

Some say that there’s no problem as long as there’s no possibility of actually changing the past, a concept called the self-consistency principle.  For example, maybe you can travel to the past, but as soon as you try to kill one of your ancestors, some mystical force prevents you from following through.  This statement, which comes from the Stanford Encyclopedia of Philosophy, highlights the point: “We should note the crucial distinction between changing the past and participating in (aka affecting or influencing) the past.” 

So what do you think?  Is it possible to affect, influence, or participate in the past without changing the past?

If time travel into the past was possible, what kinds of things could you do without causing a temporal paradox?

In the next post, I’ll dig into this a little more. 

Shameless Self-Promotion: Who is Andrew Knight?

Yesterday a neighbor asked me, “Oh, you’re a physicist?  So what do you do?”

I hemmed and hawed and gave her a really half-assed answer that didn’t reflect the meaning or magnitude of what I’m doing.  So despite the risk of being a shameless self-promoter, let me clearly and confidently answer a few questions.

Who am I?

·       A philosopher of physics and mind.  This is my most recent identity, starting in 2018 when I began pursuing, full-time, answers to the hardest unsolved problems in physics and philosophy.

·       A rocket scientist.  I invented the Rotating Spindle Pump™, a rocket engine liquid propellant pump that is lighter and less expensive than traditional turbopumps.  It was recognized as a Modern Marvel of The History Channel Invent Now^TM Challenge.  I am the sole inventor on ten U.S. patents covering RSP and other rocket engines and pumps.

·       An inventor.  I am the sole inventor on an additional seven U.S. patents on a variety of technologies including software, information compression, and consumer products.

·       A teacher.  I taught high school physics (including AP physics) as well as mathematics at several colleges, including the University of Georgia.

·       An eternal student.  I am currently taking graduate physics courses at East Carolina University, the 10^th university I’ve attended.  Others include UF (B.S.), MIT (S.M.), Georgetown (J.D.), Princeton, NYU, Shenandoah U, Universidad de Guadalajara, USF, and UAH.

·       A nuclear engineer.  I received my undergraduate and master’s degrees in nuclear engineering.

·       An entrepreneur.  I started two small hospitality businesses in Maine: the Inn at the Agora and the Agora Grand Event Center, which I sold in 2018.

·       A world traveler.  When my wife and I returned from our travels this past summer, I had traveled to my 101^st country.

What am I currently doing?

·       Pondering and solving hard problems about consciousness and the physical universe

·       Documenting, publishing, and explaining this progress via this blog, my channel on YouTube, and papers (especially this, this, this, and this).

What problems have I solved?

·       Is quantum computing possible or scalable?

·       Is Schrodinger’s Cat (or Wigner’s Friend or macroscopic quantum superpositions in general) possible?

·       Does the brain cause consciousness?

·       If the brain produces conscious identity, can the brain be copied?

·       Can conscious states be copied?

·       Is mind uploading possible?

·       Will artificial intelligence (AI) ever be conscious?

·       Is consciousness algorithmic?

·       Is the physical world reversible?  Is it deterministic?

·       Does consciousness cause collapse of the quantum wave function?

·       Do quantum waves always evolve linearly (i.e., unitarily and reversibly)? 

·       Is the above assumption (“U” or “universality”) a valid inference?

·       What are quantum superpositions?  Are they relative?

·       What does conscious identity imply about the Many Worlds Interpretation (MWI) of quantum mechanics?

·       The measurement problem

·       The black hole information paradox

·       Did the Afshar experiment demonstrate a paradox in wave-particle duality?

·       What is the role of gravity in decohering quantum superpositions?

·       Is time travel possible?

·       What scientific evidence is there for the existence of God?

·       Does infinity exist?

What problems am I working on?

·       Is there an afterlife?

·       Are conscious states history dependent?

·       Are there more possible conscious states than can be produced by the brain?

·       Do we have free will?

·       Information creation: Is Planck’s constant (ℏ) actually decreasing?  If quantum uncertainty is decreasing with time, what does that tell us about the past?  Can we extrapolate backward in time to the Big Bang?

·       Are thoughts private?

·       Why is it always now?

·       What causes the arrow of time?

What I have already accomplished is significant and important, whether or not anyone else recognizes or validates the results.  I am excited to have the time, energy, and mental capacity to continue working on these fascinating, difficult, and very meaningful problems.

FYI: Here is a selected portion of my current CV (curriculum vitae).

All Contradictions Are False

Today I received a great question from a reader that was worth posting here.  First, he references my paper on the impossibility of scalable quantum computing and says:

There seems to be nowhere for anyone to discuss it. Academia is sealed off to the public nowadays. 

Agreed.  That’s because, as I discussed in this post, there is an unholy marriage between the prophets of quantum computing and the Cult of U (i.e., the fanatical belief that quantum wave states always evolve linearly).  After attempting to submit several papers to the arXiv that questioned the assumption of U, I had assumed I was blacklisted until the unexpected happened.

Then, he asks a key question:

We hear (ad nauseum) that the spin on an electron can be both 'up' and 'down' simultaneously, but what does that actually mean?  It may be true in ket space, but it cannot be true in actual space.

First, let me point out that this should be a really stupid question.  No intelligent person should ever have to ask, “What does it mean if X is true AND X is false?”  Logically, that looks like X ∩ ¬X, which any logician will say is a contradiction and therefore a false statement.

But here’s the thing… the reader’s question is a perfectly reasonable and rational question in the physics world, because we are constantly bombarded by characterizations of quantum superpositions that are completely nonsensical.  For example, Schrodinger’s Cat is constantly described by physicists as “a cat that is both dead and alive simultaneously.”  But this is a contradiction and is necessarily false. 

This is the kind of logical error that physicists routinely make.  I have tried to point them out in papers like this and this.

If an object is in quantum state described by |A> + |B>, it is simply not the case that the object is in both state |A> and |B> simultaneously.  In fact, none of the following statements are true:

·       The object is in state |A>.

·       The object is in state |B>.

·       The object is not in state |A>.

·       The object is not in state |B>.

Indeed, there simply is no fact about whether the object is in state |A> or |B>.

In other words, dear reader, you have been misled by physicists who either don't understand basic logic or are intentionally trying to deceive the world with bad characterizations of quantum mechanics, because that is what is necessary to keep the investment money flowing into quantum computing.

By the way, infinity itself is also a contradiction.  As I discuss in this post, atheist physicists like to posit infinitely many universes to account for the existence of something that has a zero probability.  But all contradictions are false, so infinity cannot be used to imply anything true.

Andrew Knight is Qualified to Endorse

The universe is more unpredictable than I had imagined. 

As I discussed here, I was certain I had been blacklisted from the arXiv.  I have submitted ten papers to it, five of which question the assumption of U (the assumption that quantum wave states universally evolve linearly/reversibly).  Exactly five of those ten papers were rejected… can you guess which ones?

Two days ago, I submitted my new paper (“Wigner’s Friend Depends on Self-Contradictory Quantum Amplification”) to several preprint archives, as well as the arXiv just for the hell of it.  As with most of my submissions to arXiv, it immediately went “on hold” and I fully expected it to be rejected.  Amazingly, it was published last night and can be accessed here.

I don’t get it.  This new paper is not all that different from several others I’ve submitted.  The argument is somewhat different, and it’s shorter and clearer.  It also directly responds to an article that was published last year in Physical Review Letters that essentially shows that reversible measurements are a logical contradiction.  But, like my other articles that have been rejected by arXiv on the indefensible basis that they were “unrefereeable,” this article bluntly rejects U – and the physical possibilities of Schrodinger’s Cat and Wigner’s Friend – on a purely logical basis.

What’s even more amazing is that I submitted it under the subtopic physics.hist-ph (history and philosophy of physics), but some anonymous arXiv moderator moved it to quant-ph (quantum physics), which makes it my third arXiv publication in that topic.

Here’s why that’s amazing.  You can’t submit to arXiv unless someone, who is already regarded as sufficiently competent on a particular topic, endorses you in that topic.  This is one way that arXiv tries to keep out the crackpots.  (As it turns out, Scott Aaronson was the person who originally endorsed me for the quant-ph topic years ago.  He also sent me a snarky email this morning adamantly opposing the argument in this new paper.)  So how do you become an arXiv “expert” on a particular topic?  By getting three articles on arXiv in that topic.  I had already had three articles in the physics.hist-ph topic, but I only had two in quant-ph.  Indeed, I submitted the current article to the physics.hist-ph topic. 

But not only was my article published on arXiv, someone intentionally reclassified it as quant-ph, which makes it my third article in that topic.  I am now “qualified to endorse” in the quant-ph topic on arXiv.  In other words, by arXiv’s own standards, I am now, due to the reclassifying and publishing of an article that rejects the assumption of U, sufficiently competent in quantum physics to help screen out other crackpots.

WTF.  Seriously, WTF.  Either I'm finally getting heard, or someone at arXiv made a huge mistake.  Smart money's on the latter.

Schrodinger's Cat is Dead... and its Proponents are Braindead

It has become clear to me now that there is an entire industry that thrives on the ambiguity inherent in Schrodinger’s Cat and Wigner’s Friend. 

They are both based on contradictory assumptions.  And contradictions are false.

I have explained it in a simple paper understandable by anyone, including by those in the academy whose prestige and paychecks depend on perpetuating the contradictions.

The paper is here.  It won’t be published, but I don’t care anymore.  Grass is green and the sky is blue, and even if 10,000 academics publish papers to the contrary, all they are doing is perpetuating a system of mutual masturbation which is not interested in – and does not value – truth. 

It is now extraordinarily clear to me that any physicist who actually believes that Schrodinger’s Cat is physically possible in the actual universe is – to use the words of asshole Richard Dawkins – either ignorant or stupid.

I am done with this silly game.