h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I only partially read it. I soon realised the value of the advice at the end of the first paragraph, and decided to "walk away swiftly in the opposite direction".

That's a shame. It's a very thought-provoking and highly controversial idea. You could scan the three stages and get the gist of it.

I suppose that's the trouble with my guide entries: they go into so much detail that people get put off by their length. My new entry on the Origin of the Universe is twice as long as this one! I get carried away because I'm so fascinated by the things I write about.

Hi.
I'm not even going to try pretending I'm anything of an expert on this sort of thing. But I think a lot about this sort of thing, and would like to point out one major problem - unfortunately, this wouldn't "prove" the existence of parallel universes. For a start, there is the pre-ordaned theory (which is almost opposite to parallel universes, but also very similar in ways) - it may be pre-ordained that you're going to survive this rather dangerous experience, and hence your survival gives you the wrong conclusion - but more importantly, there is always the point of luck. The possibility that you will survive 10 times exists. It's quite small, but it may happen. Same for 100 times, or 1000 times. The fact that you survive in your conciousness doesn't mean that there must be an alternative universe for you to end up in - it may just be that you are immensely, insanely lucky at this time. The possibility of getting 1000 heads in a row with a fair coin exists. In some ways, the very fact that this universe would exist if the parallel universes theory is true means that if it isn't, then only one of the universes will happen, and the survival one could be that one.

And what about if you believe in an afterlife? The conciousness will go on then as well.

I think it's a very intersting article, and well written, but I'm not convinced by all the arguments.

You are right, of course. It is plain that there is a minute possibility of surviving, but as I say, after 10 turns I think there is a 99.9% chance of being dead, so the evidence is pretty convincing (to yourself) when it comes, although I agree that it can never be 'proved' totally and absolutely. But the same applies for everything. I can't even prove that I exist, let alone the existence of parallel universes. Nobody can. There are few things that are totally and utterly provable, absolute and constant. The only thing that is like that is probably mathematics, and even that is just an abstract thing.

But the physicists who devised this theory refer to it as a proof for parallel universes - and you can't really that argue that the experiment, were it to be carried out, would provide a considerable chunk of evidence towards supporting an otherwise unproved theory. I am not giving any personal opinions about whether it's a load of nonsense or not; I am simply passing on information that Tegmark and others have proposed, which is effectively 'their' view of things.

I agree that this entry is well written, and very interesting. It had me gripped 'til the end.

My only (slight) quibble is you say "This is called their superposition", wheras it may make more sense to say "This is called superposition" (as superposition is a principle (like Newton's Laws), rather than a property (like Charge)).

It may also be worth rephrasing "When an individual electron is fired at the two slits, an interference pattern emerges" by adding something like, "it appears to interfere with another electron, even though only one electron is there.", to make it a little clearer what you mean.

It's a great entry though, and I'm sure it will get picked for the Guide.

Bob McBob

Baryonic Being: off topic, but I'm sure you will be interested in F150575?thread=416534&show=20&skip=0&lpcr=0#p5273322 and what follows.

Thanks Bob for your comments; thanks Old Hairy for the link.

Is it unanimous that no more work is necessary on this entry?

I'll take that as a yes.

Yes!

The one electron/two slit experiment. I thought that the normal explanation of the result is that electrons are waves, so they cause interference patterns. I didn't think it was anything to do with parallel universes.

This sentence needs to be rephrased: it suggests that Max Tegman's name is a physicist:

"The man's name is Max Tegmark, who is indeed a physicist – at the University of Pennsylvania to be more precise".

I'd suggest:

"The man's name is Max Tegmark. He is a physicist – at the University of Pennsylvania to be precise".

anesthetic --> anaesthetic

kill you grandfather --> kill your grandfather

wholesomely --> wholly

(wholesomely means something else entirely)

"worlds that have different laws of physics" - why would the laws of physic be any different in a parallel world? Surely all this is in the framework of unchanging laws across all possible worlds?

"Quantum computers work by performing different parts of a calculation in different universes" - but quantum computers don't work. They are a theoretical construct which is based on the theory of parallel universes. They haven't managed to build any yet.

"And, just like a teacher entering a room of rowdy school children, they calm down when they are observed. "

This suggests that a teacher calms down when he or she is observed by the children. You should phrase it as:

"And, just like a room of rowdy school children when the teacher walks in, they calm down when they are observed."

How very observant you are, Gnomon! Thank you.

"The one electron/two slit experiment. I thought that the normal explanation of the result is that electrons are waves, so they cause interference patterns. I didn't think it was anything to do with parallel universes."

The wave explanation is the one that I have given first, but I have also given the many-worlds explanation, which is also a possibility.

"This sentence needs to be rephrased:..."

Done!

"anesthetic --> anaesthetic"

Done!

"kill you grandfather --> kill your grandfather"

Done!

"wholesomely --> wholly"

Done!

"'worlds that have different laws of physics' - why would the laws of physic be any different in a parallel world? Surely all this is in the framework of unchanging laws across all possible worlds?"

Why shouldn't the laws of physics be different in different universes? This is in fact a serious possibility that is wholly believed by the Astronomer Royal, Martin Rees.

"'Quantum computers work by performing different parts of a calculation in different universes' - but quantum computers don't work. They are a theoretical construct which is based on the theory of parallel universes. They haven't managed to build any yet."

I've written an entry about Quantum Computing. They have, in fact, built small versions of quantum computers, and they do work - to a certain extent. And, there is nothing in the theory of the Standard Model to suggest that quantum computers are impossible to build. If you really want, I could put the sentence into the conditional tense - 'quantum computers would work by...'.

"And, just like a teacher entering a room of rowdy school children..."

Changed!

Thank you again.

As you've described it, the two universes exist because of a single random event which caused a single universe to split into two. Why would a random event happening cause the laws of physics to change? It wouldn't, so each of the two universes must have the same laws of physics as the original "parent" universe, so they must have the same laws of physics as each other.

No; for one such random event occurs at the very beginning of the universe, whereby the nature of its creation alters the laws that will ultimately govern it, and hence there begins a multiverse of very different universes from the start, branching out from there.

Anyone interested in becoming immortal?

That was a beautiful article. I almost feel like trying it. I think I will when I reach 70 or something.

One point though, in your line:

"It is necessary for this variation to understand a quantum mechanical concept known as spin. 'Spin' is a loose term used by physicists with no fixed definition, pertaining to its angular momentum and symmetry, and is measured in Planck units4."


The 'pertaining to its' part has one problem. You mention what 'it' is two lines after this. Probably should mention before.

Otherwise greatjob.

Thanks for pointing that out; I think I've fixed it now.

To be honest, I don't know why some very old physicist hasn't already tried this experiment. Even if it didn't work, we would know about it. Good luck!

It's been a long time since I wrote this...

Not sure who's got a pick at the moment, BB!

Didn't you hear the news? Scouts have an extra pick this week; Paully said so on the mailing list, he did; ready for the Big Push in the Autumn, you see.

No, I hadn't seen it ... however as you've brought it to my attention ...