Yesterday's HORIZON programme: What is Reality? ..

The non amateur stuff. Hawking, black holes, that sort of thing

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brian livesey
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Yesterday's HORIZON programme: What is Reality? ..

Post by brian livesey »

One of the physicists in the programme held the position that, because a particle can be in two places at the same time, this means that there are many replicates of himself in parallel universes.
I'm no expert, but I detect a flaw in this way of thinking. The physicist assumed that, because particles can be in one place and another simultaneously, as demonstrated in the celebrated slit experiment and in particle acccelerators, this must always be the case.
It overlooks the fact that when we change the conditions we get different results. There's no reason to think that because a particle acts in a certain way in certain conditions, that it will act the same way in all conditions, including when it is part of the human body. In this instance, the particle is neither being shot from a laser, nor being accelerated.
Has anyone else any thoughts on this?
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Post by Davej »

Hi Brian,
I can't really comment as a lot of it was beyond me. that's why I don't post much on this section very often ).
I found it interesting though but I did switch it off after twenty minutes or so and recorded the rest for later viewing. Anyone who missed it can view it on BBCiplayer. To save the trouble of searching for it here it is...

http://www.bbc.co.uk/iplayer/episode/b0 ... s_Reality/

All the best
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brian livesey
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Post by brian livesey »

There are other criticisms to make about the programme. If the physicist mentioned thinks that he's been replicated many times in other dimensions, and assuming that he thinks everything is made of elementary particles, how could his replicates have consciousness?
There's no data to show that consciousness - thoughts, concepts, feelings - consist of particles, so his replicates must be mindless.
The physicist in question seems to be trapped in an old-fashioned mechanistic universe of whizzing, colliding, particles and nothing else.
Another physicist, erring on the idealist side, claimed that the Universe is mathematics incarnate. This is a common error - to take one aspect of reality and use it to account for the rest. Nature's infinite variability can't be accounted for on the basis of one aspect of itself. :wink:
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Post by jb1970 »

I've recorded it but not watched it yet. Did he claim that there certainly will be replicates of himself or that it is a possibility? Quantum physics seems to say that nothing is certain. I'll watch the program.

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Post by Tony Markham »

A lot of the confusion in this area arises through thinking of particles such as electrons as having a precise location.

Its easier (and probably more accurate) to think of them as being more "fuzzy". This allows a particle to simultaneously pass through both slits in the double slit experiment and then interfere with itself to produce the interference pattern at the detector.

Particles only stop being "fuzzy" when we "measure" them - such as via the detector in the double slit experiment. Whether the particle is detected as something with a precise location or as something more wave-like will be influenced by how we carry out the measurement.

The "replication" referred to in the programme is a theoretical idea - at the quantum level, events don't have a guaranteed outcome - there are a range of possibilities, each with a different probability. We will see one outcome. The idea of the other outcomes occurring in parallel universes is a way of avoiding having to explain why the particular outcome occurred in our universe.
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Post by David Frydman »

Doesn't the last paragraph imply that there must be an infinite number of parallel universes to cope with every event that happens.
If indeed there are parallel universes.

Regards, David
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Post by Tony Markham »

To allow for all possibilities for all events would indeed require an infinite number of parallel universes.

Personally I think that theoreticians need to accept that an outcome has to occur ... and the one that occurs just happens to be a particular one ... and therefore we don't need to "invent" parallel universes in order to prevent "our" outcome being "special".
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Post by brian livesey »

Correct me if I'm mistaken, but are you saying that events that occur in nature ( not in physics laboratories ) at the quantum level are completely random? If so, how do we account for the fact that there's order in the Universe?
In the programme, we were informed that the basic building blocks of "reality" are the particles known as quarks, muons and leptons. If these phenomena are particles in the literal sense, then they must be divisible into even smaller elementary particles: every particle of matter has spatial dimensions.
Perhaps the programme meant that quarks et al are the smallest particles so far discovered, and that ( allowing for the Higg's boson ) more powerful accelerators might reveal more.
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Post by stella »

Sorry Brian, but Peter Higgs does not have an apostrophe in his name.
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Post by Tony Markham »

Brian,

We can't predict with 100% certainty whether a single event will have a particular outcome, but that doesn't mean that outcomes are totally random - we can predict that some outcomes will be more likely than others ... hence there is order on the bigger scale of nature.

On the small scale, an electron encountering a "barrier" that it doesn't have enough energy to cross will (nearly) always be reflected back, but quantum physics allows a very very very small probability that it will "tunnel" through the barrier.

Regarding quarks, once again our everyday concept of a particle as being something like a grain of sand makes it difficult to envisage "particles" at the atomic or sub-atomic levels. At these levels the entities referred to as "particles" don't have specific spatial sizes and it is usually necessary to resort to some sort of analogy in order to get an understanding .

I quite like the way that the use of the names "up, down, top, bottom, strange, charm" given to the quarks allows the analogy of particles such as protons and neutrons being made up of a specific combination of a number of "properties" ... and a property such as "up" can't be subdivided. The names of the quarks are of course arbitrary, but the analogy does help us get closer to an understanding of a world very different from our everyday experience.
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Post by brian livesey »

Thanks, Tony, for the clarity of your reply. By the way, Stella, you left out the comma after "Sorry". :wink:
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Post by joe »

I suggest reading Richard Feynman's, QED: The Strange Theory of Light and Matter. It explains extremely well and in detail many of the confusing aspects of how particles can behave randomly and yet be predictable. That's if you haven't already, of course!
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Post by brian livesey »

If I was younger, Joe, I'd probably read more in-depth on the subject, but I'm too lazy these days. :roll:
Nowadays, I prefer the radio and the lie-back-and-watch television approach, rather than reading eye-watering technical books on physics and astrophysics.
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Post by joe »

Understood. This book is small, around 100 pages, and is a record of a few lectures he made. Very easy to follow.
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Post by Davej »

brian livesey wrote:Thanks, Tony, for the clarity of your reply. By the way, Stella, you left out the comma after "Sorry". :wink:
Hi Brian,
Sorry but you've still been Stella'rd :) .
I think my English grammar is a bit better than my astrophyicist knowlege.
There should be no comma after "sorry", sorry :wink:
That's me done on this section for another year or so (good reading though).

All the best
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