Does Feynman's Multiple Histories mean what I think it does?

I was Just reading The Universe in a Nutshell for the first time.
In it, Steven Hawking says that Feynman's Multiple Histories certifies that theory that everything that can exist, does or will exist. That out there in the cosmos there is an exact replica of Erath, you, me ect...

However, when I entered Feynman's Multiple Histories into a search engine the results don't seem to match what Hawking said in his book.

So who is right and what does Multiple Histories mean?

 

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I think that Hawking and Feynman understood the same thing by Feynman's use of Multiple Histories. I think Hawking also extended that in his belief system to include the interpretation you first mentioned. There is no proof for that interpretation.

 

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For an exact replica of "Earth, you, me etc", those relicas would, imo have to have the exact same pasts as the originals.

In other words each replica would subtend an entire,evolving replica universe

If that was the case it would be a meaningless assumption and the possibility of it happening/having happened can be dismissed as of no interest .

Any body that can be said to exist(Earth, you, me etc) does not exist as static definable separate entitiy but as part of the changing ,dynamic environment it is part of.

 

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Recently I started reading The Universe in a Nutshell by Steven Hawking and I came across his chapter on Feynman's Multiple Histories. Hawking said it confirmed the theory that, somewhere out in the cosmos, there's exact duplicate of Earth, you and me doing what we're doing right now, purely by coincidence.

I looked up Feynman's Multiple Histories online to see if that's what it meant. Not only did I find that's not what it means but I found a conversation on Physics Stack where someone had voiced a similar issue. The other person said that Universe in a Nutshell was a bad book and they should stop reading it at once. A few other said Hawking was arrogant and his writings had no real value.

I was shocked by all of this. Ever since I first heard about him back in the 90s, he's been portrayed as this icon of genius, the greatest mind of a generation. When TV, movies and videogames want to create a genius character, they create him in Hawking's image. And I know that's not a scientific way to rate intellect but it wouldn't be this way if most people didn't think he was a genius and I can't help but think they thought that because he is. Apert from some references in Futurama accusing him of plagiarism, I've never heard a bad word against him until now.

So I want to ask you, was Steven Hawking a good scientist? Is his work considered fact or theory? Is it done scientifically? Should his book be considered to be full of immutable proven facts or current models and theories? Because I can't tell if someone says everything like it's true. And should I keep reading The Universe in a Nutshell? Because I'm only half way through.

 

"Fact or theory" is a test you need to apply correctly in science. The only facts in science are suitably confirmed observations of nature. These observations are carried out by experimental scientists, of whom Stephen Hawking was not one. He was a theoretician so naturally what his research produced was theories, not facts. No doubt his book includes a fair amount of speculation, some of it metaphysical. This will go beyond his scientific theories and will doubtless be very much open to question. It should be noted that the various "interpretations" of quantum theory, including Copenhagen, Many Worlds, Relational etc are really metaphysics rather than science. They are the subject of much debate but do not affect the theory.

Hawking is regarded as a very good scientist. That does not make him infallible. Even Einstein made what we now think of as mistakes. But Hawking's public reputation was due not just to his science, which was good (though apparently not good enough for a Nobel Prize), but also to his impressive personal achievement of managing to do so much considering his terrible physical disability. One should not overemphasise his scientific contributions just because of that, which I think has been a problem in some popular portrayals of the man.

 

Based on his published papers and H index yes.

 

I think there may be some misunderstanding here.

Recall that when a quantum system is known to be in certain state, say A, but is measured to be in either state B or in state C, it is said to be in a superposition of states. Recall also that in this circumstance, there exists no measurement corresponding to state A, as it is the sum of the states B and C. Hence states are said to be descried by a state vector.

Feynman's idea as I understand it is that, since the history of a system is nothing other than its trajectory through configuration space, the present state of a system is the sum of these trajectories, that is, the superposition of multiple histories.

I am not aware that he intended it to apply outside the quantum realm, but I could be wrong.

 

If going by Dyson, then privately Feynman might have been reifying Sum Over Histories or attaching physical correlates and significance to its abstract description. Or (more safely), maybe it was purely "pictures" he was dabbling in rather than projecting such upon objective reality as a literal situation.

Freeman Dyson: Dick [Feynman] fought back against my skepticism, arguing that Einstein had failed because he stopped thinking in concrete physical images and became a manipulator of equations. I had to admit that was true. The great discoveries of Einstein’s earlier years were all based on direct physical intuition. Einstein’s later unified theories failed because they were only sets of equations without physical meaning. Dick’s sum-over-histories theory was in the spirit of the young Einstein, not of the old Einstein. It was solidly rooted in physical reality. --Disturbing the Universe (1979)

Dyson as quoted by Nick Herbert: Thirty-one years ago [1949], Dick Feynman told me about his "sum over histories" version of quantum mechanics. "The electron does anything it likes," he said. "It just goes in any direction at any speed, forward or backward in time, however it likes, and then you add up the amplitudes and it gives you the wave function." I said to him, "You're crazy." But he wasn't. --Quantum Reality: Beyond the New Physics (1987)​

I can't risk typing the "magnet" of his name directly in this post for obvious reasons, but coincidentally it also sounds like what a certain metaphysically-prone someone (below) advocates sans referencing and utilizing that particular item (as Hawking did).

Spoiler

Parallel Universes (2003)
https://space.mit.edu/home/tegmark/multiverse.pdf

EXCERPTS: If space is infinite and the distribution of matter is sufficiently uniform on large scales, then even the most unlikely events must take place somewhere. In particular, there are infinitely many other inhabited planets, including not just one but infinitely many with people with the same appearance, name and memories as you. Indeed, there are infinitely many other regions the size of our observable universe, There every possible cosmic history is played out. This is the Level I multiverse.

[...] As reviewed in this article, it is becoming increasingly clear that multiverse models grounded in modern physics can in fact be empirically testable, predictive and falsifiable. Indeed, as many as four distinct types of parallel universes have been discussed in the recent scientific literature, so that the key question is not whether there is a multiverse (since Level I is rather uncontroversial), but rather how many levels it has.

_

 

You can get misconceptions from popsci

 

The graphic shows multiple possible paths, leading to 5 outcomes.

The choice at each branch determines which path becomes a reality (red).

You can't return to the origin (0) and do it over. Time accumulates.

Floyd driving to the airport runs out of gas on (3-6) and misses his flight. The plane crashes (6) and no one survives. Had he not run out of gas he would have made his flight and been a fatality (3-7).

Floyd says "running out of gas saved my life". No so Floyd. Running out of gas and the plane crashing are independent events. There is no cause and effect.

His other choice at (3-8) would have resulted in severe injuries in an auto accident (8).

This is an example showing the future is not known until it happens. Theories like

many worlds are extreme attempts to predict the future. No better than astrology or tea leaves.

There seems to be a trend toward fantasy replacing objective science.

All things thinkable are not realizable.

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Unless your friend Floyd inhabits the quantum world, you are missingthe point

On the contrary, they are an admission that, in the quantum world, the future is by definition, unkmowable.

Let me repeat my earlier post:
If a quantum state is the sum of at least 2 other supparposed states, and if, for every such state this is true for each of its antecendent states, and, referring to the set of all such antecendents as a state's history, then the theory says that the present state of a quantum system is the sum over all its history.

 

QuarkHead;

We have a particle P that has 2 decay states, A and b with probability rates of .4 and .6 respectively. The probabilities are values based on the history of P. Which result happens now?
The future is unknowable period, since it hasn't happened. The images from distant events haven't arrived yet. We always observe events after the fact. All observations are historical. The so called successful 'predictions' are only the result of consistent laws regulating the universe.

My post was only contrasting many possibilities vs. one actuality. Many worlds or the block universe attempts to explain events that happen and even the ones that don't happen. In the manner of a popular comedian, 'it just don't look right to me'.

If the block universe contains all events that have and can happen, where do we put new events or new objects that are formed?

 

James;

It might help to refer to 'QED' by R. Feynman.

Feynman uses the 'least action' principle of Hamilton in his QED light interference experiments. Light as particles move wherever they can*. Since light has only one speed in vacuum, it's analogous to a race. The winner is the first to reach the finish line.

In the graphic, light from source S reflects from mirror M. Feynman envisions millions or billions of photons reflecting from the entire M surface. If the simple (for clarity) photon trajectories continue through M to the virtual image of D (D'), the comparison is easy to visualize. The shortest and least time is the line through location 1 on the M. Analysis of the angles a, reveals the equal angle of incidence to angle of reflection rule. Since the variation to either side of path 1 is minimal, its also the area of greatest intensity.


* I don't agree with any particle moving backward in time. Clocks moving at speed v>0 lose time. A clock cannot move slower than v=0, thus there is no speed by which a clock gains time. (a clock moved to a higher altitude runs faster only due to less gravitational influence)

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You said to be wary about putting scientists on pedestals. But the thing is I do, I always do, I don't think I can help it. I do it every time I read about science in books and online and every time I watch a science documentary.
You said "You probably don't put lawyers on a pedestal or assume that their every statement is a hard fact." Well I would if I were seeking legal advice or asking them about laws and trials. And are you saying I shouldn't assume their every statement is a hard fact. Are you saying they're not? Why wouldn't they be?
I also do the same thing with makers of history documentaries, doctors I visit and the teachers I've had.
Because all these people have knowledge, education, experience and access to resources I don't. And are probably a lot smarter then me.
Who am I to question them? How am supposed to learn anything if I doubt everything they say? You know who do question experts? Anti-vaxers, flat-Earthers and people who want evolution banned from all schools.
I do put scientists on pedestals. Because, as far as I know, they are the ones who know, the ones who figure out what is real and false and write the books about it, the book teachers teach from. As well as being the smartest people in the world. You don't think of politicians or artists being smarter then cosmologists and quantum physicists do you?

You say scientific claims are all provisional? Not according to every science documentary I've ever seen. And they don't say what's established and speculative. If anything they say it's all established.
On an episode of the show Nova, the presenter once said "Since there is a finite number of ways matter can be arranged in a finite space, there exists out there exact duplicates of you, me and everyone."
He didn't say "If there is a finite number of ways..." or "Let's suppose there is a finite number of ways..."
He said SINCE. So I can't help but assume that this thing about matter in a finite space is 100% true, and has been proven beyond a shadow of a doubt by scientists and is part of the things we know to be absolute truths. Because he wouldn't have said it like that otherwise.
Not long ago I saw another show presented by physicist Brian Cox. He was talking about how entropy will end the universe in a dark and lifeless void forever. With every sentence he said that this was what was going to happen. He never once said that any of this was supposition or there was any chance of this not happening. In fact I've never heard any scientist or virtually anyone at all say the universe won't end in my entire 37 year life.
Incidentally I've brought up these 2 issues here and on other sites and in each case the response has been quote "Of course it will" "It's as sure as 2+2=4" and some made fun of me for even questioning these things.
And now your telling me it's all provisional? You said I should look for the clues but what clues are there when they say everything as if it's a fact? How am I supposed to even begin to figure out what parts of science are factual and suppositional when everyone, fans and presenters, say it's all factual? And when people say it like that I can't help but think it's because it's the truth.

You've sent me into a bit of a panic here because you're asking me to think for myself. And while I know that's noble and vital, I don't know if I can do it.
For one thing, to do it I'd need a lot of scientific knowledge to challenge pop-science and if I had that I wouldn't need pop-science. How am I supposed to think for myself on a subject I know nothing about?
And for another there's my neurology. I have Asperger's syndrome, which means I tend to take statements literally and I think in absolutes, black and white, right and wrong with nothing in between. I know of grey areas and partial truths but at the same time my brain can't process them.
I'm not gullible or a mindless sheep but when someone, anyone makes a statement I can help but think it's true and if it conflicts with what I think I must be wrong.
It even happens with my own opinions, I like the show Fresh Prince of Belair, once I hard my dad say what a stupid show it was and I thought "Oh, my opinion of this show's quality must be wrong." And for a while I stopped enjoying it.
Another time I had seen this American-made documentary about the American revolution and I was awed at how it changed the course of human history. Then I saw this British-made about the revolution and the historian presenting it said it was started by the rich who thought they could get richer without British tax law. He even implied these people fired the first shot at Lexington to get it going.
It took some time but I came to the thought that this man's documentary fell more along the lines of conspiracy theories then anything else. But even now I feel I'm not allowed to think that. Really I can't help but think I'm not allowed to disagree with experts and the overwhelming masses who agree with them.
You said I should look for clues to what is suppositional? The only clues I can pick up on are when they say something like "All statements made in this programme are provisional, theories and hypotheticals based on current scientific knowledge which is subject to change." Which they never do.
Unless someone says something reeeeealy outrageous or obviously wrong I can't pick up on that at all.

In conclusion how am I supposed to think for myself and spot what is provisional on subjects I know little about, when my intellectual superiors state over and over it's true, when everyone else believes them and call me a fool for questioning them, when fact and opinion sound exactly the same and I'm fighting my own neurology?

 

What James says about science is basic philosophy of science and not in the least controversial. No theory can be proven true as all theories in science could in principle be overturned, if some new and unforeseen observation of nature came along that showed a theory to be wrong. One can never logically exclude the possibility of that.

Also you already know of several theories in science that are in a sense "wrong". What about Newtonian mechanics or his theory of gravitation? Einstein's special relativity showed Newtonian mechanics breaks down when objects are in relative motion that is a significant fraction of the speed of light. His general relativity also showed that Newtonian gravitation breaks down under certain circumstances, too. Nevertheless engineers and physicists continue to use Newton's theories because they are good enough for most purposes and far simpler to work with. They just keep in mind that their scope of application is limited.

Secondly, if you know anything of the history of science you will be aware of many more theories that served a purpose for a time and then were discarded after being shown to be poor models: the Ptolemaic (geocentric) system of astronomy, phlogiston, the aether, the caloric theory of heat.......etc etc. We cannot assume that none of the theories we have today will not one day be superseded.

So no need to panic. Just get used to the idea that theories are models of nature that may not be exact. Some work well all the time, so far as we know. Others work in certain circumstances, or are approximations. Some are contested by rival groups of theorists. And some are tentative because we do not yet have a full wealth of observations to know how good they are. That last limitation applies to a fair amount of cosmology, since a number of the relevant observations are difficult to make.

I'm sure you are right that TV programmes about science tend not to dwell on the philosophical limitations of scientific theories. They will be simplified for the purpose of teaching some specific theory and generally won't want to get side-tracked into a debate about the possibility, however faint, that the theory in question might get overturned one day.

But, Asperger's or not, you have to face the fact that scientific theories are not absolute and eternal. They are the best models we have for the time being. That's all they can ever be. Scientific research is working on improvements all the time.

 

Don't put yourself down.
Pop science can give you a flavour, I used to read lots of it.
I will say that you can get a decent view of the players, what they did and when. A history/chronology.
The technical details however, the real meat gets lost or brushed over.

Science is hard, you can't read a couple of books and understand it, it takes years of studying and practice.
Pop sci gives the impression you can take it in via YouTube videos or a Brian Cox book.

In terms of where to start, review what you learned school 14-16, school books. If you did any A level type courses or above I would still do that.
Reason? They usually have questions at the end of the chapters, have a go at them.
14-16 covered? Move up a notch. 16-18 A level.
You may not get this if you are not from UK.