OT Primordial black holes are dark matter.

As an aside, you now hold the record for the weirdest compliment I've ever received. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

I don't know it! I was trying to suggest an answer to your initial objection.

No, we have a shared past but divergent futures. AIUI. Although actually I don't know how that works with the fundamental laws of physics supposedly being time symmetrical.

Well that's the same thing. They are different "philosophical" interpretations of the same mathematics. But you can better just use the mathematics and be done I suspect.

I suspect you must be familiar with the idea already but:

Make a random number generator based ultimately on a QM effect like shot or thermal noise. A decoder is set to generate a signal for all numbers except the value 999,999,999.

Connect the decoder output via a switch to e.g. bomb on your head.

With the switch open, you see a sequence of random numbers.

Close the switch, and if MWI is correct you then see

999,999,999 999,999,999 999,999,999

(or else a mysterious malfunction).

I am not a true believer here, just trying to explain away your initial objection to it. It still does not seem that unreasonable and cleverer people than me seem to prefer it.

--

John Devereux

The whole reason for the MWI afaict is to try to explain away the specialness of the actual course of history, by saying that it isn't special at all, just one of an uncountable multitude.

But it is special, because it's the one we're in. How did we get just here and not somewhere else? It's the same question in another form--the only difference is this ridiculous mass of purely hypothetical universes we've dreamed up. It doesn't depend on the future, which is as unknown in the real universe as in one of the dreams of Brahma, I mean MWI multiverses.

But that doesn't work, ISTM. Who is this "I" that would see this? Identity relies on continuity--i.e. in story. I'm not even sure it makes sense to say that there would be fewer P. Hobbses after that--the number of universes would be uncountably infinite. By way of analogy, any finite segment of the real line can be put into a 1:1 correspondence with the whole real line.)

Most folks I've talked to about it have had objections that were theological at bottom--the problem of uncaused events and the wide-open field for divine providence. If there really is a God, that changes everything, forever. Some of us react with joy, some don't.

Signing off for the weekend. Happy Labor Day, everybody.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

I had never heard that (although it does "explain" it. It thought it was to explain (avoid) the problem of what exactly collapses the wave function. What constitutes a "measurement".

And every other "version" asks the same thing.

[...]

The surviving ones.

There is continuity in that surviving branches have the same memories. The same as they all do (in MWI) normally without the severe culling of the experiment.

If the multiverse splits you into two identical copies, you can say that the original is then dead if you like. But if this is in fact going on you would be none the wiser. You could not tell. Certainly each copy would think it is the same person and in fact it would be the same person at that point IMO.

Sorry I don't understand that.

Well yes, perhaps. If.

If I thought it all likely I would too I would imagine. It just seems.... bizzare. Sorry. (I know, this from someone who has just posted all the above wild speculation. I still find even that more believable somehow).

And to you!

--

John Devereux

But there's the question of what "meaning" means- what values we place on events and actions, "good" or "bad".

For theists, those definitions are absolute and inflexible, handed down f rom the ultimate unimpeachable authority.

For non-theists, there are other options that *seem* to boil down to util ity.

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If by definition those who use their free will to not follow the absolute inflexible decrees are "abusing" their free will, then how is it "free"?

ed

Sigh. Which "sin", Original Sin?

The Mormons (among others) seem to think that's exactly the case.

Buddhists take a more, shall we say utilitarian approach- indulging in "a ddictions and vices" isn't "evil", it just wastes time we could be using im proving ourselves and others.

So, "cheering section"? We are so much more...

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Support your group (family, tribe, nation, etc.) and it will support you. The hard part (for some) is realizing that the group will outlive you, so ensuring your own survival is less important than ensuring the continuation of the group.

I blame Plato for formalizing Duality and embedding it into Western thoug ht.

What's to say the shadow-casters aren't just shadows of a different sort?

Is there one in any system?

s.

That's Law, of the "Always God" sort.

And, sometimes let them make mistakes so they can see why not to make tho se mistakes.

Altruism is a sort of shared (or maybe less incorrectly, projected) selfi shness.

I want what I think is good for me, but I must deal with others who want what they think is good for them, and I should help others get what they wa nt in the short term *even if it conflicts with what I want in the short te rm* so I can get what I want in the long term.

Sometimes, that's even good business practice. ;>)

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Bingo!

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Worse, we now know that many of our "purely intellectual decisions" are m ade before we think we make them.

Even if all of love, emotion, etc. were nailed down as unambiguous "mere biochemistry", I don't think love would go out of style.

Mark L. Fergerson

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That's an interesting point. Feynman diagrams do not take the arrow of ti me into account, so there must be *many* possible pasts that lead up to our shared "now". All traces of differences have been swamped out by the commo nalities, though. "Sum over histories" writ large if you like.

Heard of the Mandela Effect? Some folks claim to remember historical even ts differently from what "history" says happened, citing it a evidence of t he MWI. Most dismiss it as faulty memory, but I'm POSITIVE that I read Mand ela died in a South African prison in the 1980's. Maybe it was somebody's p ropaganda piece in a low-rent rag, but still.

Then there's the wildly popular movie "Where The Wild Things Are". Maybe I led a deprived childhood but I never heard of the book it was made from.

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"Shut up and calculate." ;>)

Conversely, philosophers make horrible physicists; many of them don't eve n believe the physical universe exists...

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Science used to be called "Natural philosophy".

OTOH I've never heard of an "empirical philosopher".

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See, this is where pure philosophers fall down in not taking cues from th e pure physical sciences. If angels are bosons you can superpose an infinit e number of them...

MWI universes OTOH apparently obey Fermi-Dirac statistics; that's why the y're mutually unreachable.

Interpretation is a favorite pastime of humans. Nothing mysterious about it at all.

Mark L. Fergerson

Haldane said that he'd sacrifice himself for two sibling or eight cousins - they represented the same amount of his DNA (not that Haldane would have been aware that DNA was involved, or how).

-- Bill Sloman, Sydney

Yes that's interesting - above my pay grade though :)

Could you perhaps have got him mixed up with Biko?

[...]

--

John Devereux

(snip to the physics, and the psychology, maybe)

Feynman diagrams are just the math* turned into pictures, and nobody's falsified the math.

No, definitely Mandela; Biko had already been beaten to death in 1977. The Mandela Effect is really a thing, look it up.

• Also above my pay grade, but I know people who can do it.

Mark L. Fergerson

So our past is divergent as well as our future. All the myriad ways conspire to converge into exactly our present instant.

Yes I did.

I met him in the early 90's! He was definitely alive at that point. :)

(I was on a flight to south africa and had got bumped to business class somehow. He appeared from behind the first class curtain and started going around meeting people).

--

John Devereux

To carry that analogy further, I sometimes feel like modern physics is using higher and higher degree polynomial curves for their fitting. Their error bars are getting tighter through better experiment, so they know it's not just a straight line with noise - it really is a curve. But perhaps that complex high degree polynomial is actually hiding a simple sine wave.

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Bad analogy. Modern physics is using more and more exotic fitting functions , but each parameter means something.

Higher order polynomials just tack on more and more arbitrary corrections, and none of the higher order parameter weights have any physical significan ce.

I remember fitting an absorbance curve which was funny shaped because the o ptical filter spanned enough wavelengths that the extinction coefficient va ried significantly across the wavelengths getting through, so I approximate d it with a linearly sloped extinction coefficient. It more of less worked, and made physical sense.

--
Bill Sloman, Sydney

They already had dark matter (which at the time it was proposed could have been non-luminous baryonic matter but that is now ruled out by much better observational data). Dark energy was a new name given to the corresponding Einsteins cosmological constant by analogy. (it is another thing we see the effects of but not the thing itself)

Chances are that one day a much better theory will include SR,GR & QM into a GUT that includes each of the others as a weak field limiting case. String theorists might be onto something but only time will tell. it is one of those breakthroughs that we will know when we see it and after a century or so teaching it in universities will become mainstream with a few old cranks insisting that it isn't true.

Pretty much as has happened with relativity and Big Bang cosmology over the twentieth century.

Generally there is some underlying theoretical model to explain why things behave as they do and the hypothesis is tested against the observations. Right now the obeservers have the upper hand with ever more sensitive and wider spectral range of observations from new instruments coming onstream all the time.

That is what engineers do. It is amazing the number of people that will fit a cubic calibration polynomial to 4 data points :(

Normally physicists have a pretty good idea of the shape of curve that they are fitting to data and the question is more along the lines of how much of it (if any) is needed to explain the observations.

Extracting tiny amounts of signal from overwhelming amounts of noise by a combination of devious experminental technique, bulk data and massive amounts of signal processing is our stock in trade.

Regards, Martin Brown

And some intriguing plot possibilities (I'm thinking of Gaiman's _Interworld_)

I bought a calibrated temperature sensing diode form Lakeshore, with some multi-paramter fitting function. Eight or more variables. I was using it to calibrate some other diodes, the temperature variation of which had a nice linear temperature dependence. (When I subtracted curves from two diodes and plotted vs T, I got a straight line.) When I looked real close at the subtracted data I could see this slow oscillation (not random error) and I always have wondered if it was form the fitting function. (the error was really small.)

Regardless of which, I wondered if they would do better job by adding a little more physics to their model.

George H.

Or by using a better set of basis functions, even without extra physics.

Cheers

Phil Hobbs

It might have been a deliberate minimum ripple fit to the calibration to guarantee absolute bounds on the error. Typically the misfit looks like one of the orthogonal Chebyshev polynomials. Rational functions often give a nicer fit for fewer free parameters than a polynomial.

I am sure Phil knows this stuff but it might help George understand the pattern of residuals in his calibration.

Regards, Martin Brown

Especially for functions with asymptotes, or where most of the action happe ns in a smallish part of the domain.

Acton has an especially good intuitive discussion of why that is--basically because denominator roots get placed appropriately.

A favourite trick of mine (which I didn't invent) is the FFT Chebyshev rati onal function fit to a known function. You take, say, 2048 samples at Cheby shev abscissae, and cosine-transform them to get a 2047th-order polynomial. Then you pick your numerator and denominator orders, and construct a Cheby shev rational function with undetermined coefficients. Equate this to the l ong polynomial, cross-multiply to clear the denominator, apply the orthogon ality telation to nuke the cross-terms, and solve for the coefficients.

This is easy to automate, so you can easily try out several choices of orde r, and yields very nearly the exact equiripple approximation.

I haven't tried it for experimental calibrations, but for lowish orders I e xpect it would work fine.

Cheers

Phil Hobbs

Thanks Martin, The residuals don't bother me at all, they were way below other errors in the calibration. I was just using it as an example of polynomial fitting. And I don't mean to be dissing Lakeshore*, for all I know someone did try and put a little physics into the fitting. (I paid zero attention to the fitting function and just loaded their data into the temp controller.)

George H.

• Well I will dis Lakeshore in this way, I paid for a calibration from 70 - 325 K, I'm using the diode from 77 to ~< 400K, I cared more about room temperature and below so I didn't want to pay for calibration to 500K (I think that was the high T option.) And I figured (wrongly) that the "calibration" above 325 would have a little more error, but would be good enough. When I plotted the calibration data, there was a few degree step change in going from 325 to 330. Above the data point I paid for they just plugged in their "standard" curve with no attempt to correct it for the specific diode. (OK I guess that's their choice, to maximize profits over utility/customer satisfaction.) Anyway I first subtracted off a constant offset voltage and that worked OK, but was still a bit off. Fortunately** I had three other (uncalibrated) diodes in the probe whose difference's remained linear in T***, so I could see the difference. A fix in of the lakeshore diode that subtracted an additional T term, and Viola. Everything was awesome!

**There's real value in having three of something to compare, you can take everyone's differences.

*** sorry I had knee surgery yesterday and I'm supposed to rest today with my foot elevated, and iced every 20 min. So at at home in front of the 'puter.

Anyway, I was just thinking the linear plot in T is also a linear plot in 1/T. And is the

1/T plot "more physical" for a diode sensor?

The knee feels great, I was given all these pain killers but haven't touched them. I can start exercising it this afternoon. I haven't had a beer for three days and the best think about no pain killers is I can have a beer with lunch!