[ExI] paradox perhaps

spike at rainier66.com spike at rainier66.com
Thu Sep 15 04:41:04 UTC 2022



From: extropy-chat <extropy-chat-bounces at lists.extropy.org> On Behalf Of Mike Dougherty via extropy-chat
Subject: Re: [ExI] paradox perhaps


On Wed, Sep 14, 2022, 8:23 PM spike jones via extropy-chat <extropy-chat at lists.extropy.org <mailto:extropy-chat at lists.extropy.org> > wrote:

Mike one minor detail: it isn’t a trend but rather only one number based on one number.  Is it possible to estimate  a span between visits with *any* level of confidence (and if so, what confidence?) based on the time since the last visit?

>…I say no.  


>…What you are proposing feels to me like asking if it is possible to predict the outcome of a fair coin flip based on the result of a previous coin flip….


>…And that's why/how common sense fails us: you are drawing parallels to mountaintop logbook signatures, i am grasping at straws like bass/infrasound - but neither of those are good surrogates for what LIGO is actually measuring. 


>…It is fun to think about though :)



Mike back in about the early 2000s when there was all the buzz about whether LIGO was worth building, I estimated the probability of a detectable event in each century at about 50-50, so I was a skeptic on building the thing.  If you were following it, you may recall they turned it on in late 2015 but it was really only a test run, for calibrations and such.  No one expected the bwIP about 3 wks after they turned it on.


They studied the hell outta that signal and in February announced to the world LIGO had witnessed a black hole merger.  That was the first time I started thinking about this question.  I really wondered if it was possible, this was a once in a lifetime event, and they just happened to get the instrument turned on just in time to detect it.  That was the first time I really thought about the problem of estimating a frequency of an event based on a single known interval (about 3 wks in the case of LIGO, 10 days in the case of the mountaintop log book.)


Well now we have a second LIGO.  The first one is in BillW’s neighborhood: Livingston Louisiana, the other is in Hanford near Richland WA.  There is another interferometer (Virgo) which is being built in India, so we can triangulate and figure out where the wave came from.  Cool!


Regarding something I posted about a few weeks ago, why I thought these events would be so rare: I couldn’t (and still can’t) grasp where all that angular momentum is going.


The following are not even BOTECs, no need to mess up an otherwise back of an envelope.  We can do these in our heads.  Imagine two black holes forming (somehow) at a sun/earth distance, one AU, so about 150 million km, so multiply by 2 pi, the circumference of the orbit is about a billion km, and it goes around in about 30 million seconds, so the earth goes about 30 km per second.  So now imagine increasing the mass of both to 30 solar masses, same distance apart, so the attraction is 60 times greater, so the orbit speed is close enough to 8 times faster, 240 km per second and we still having messed up an envelope.


The momentum absorbed is the equivalent of (somehow) stopping an object of mass 30 solar masses going 250 km per second.  I run thru those equations regarding warping of spacetime, and I just don’t get how there could be so many of these events still happening.


My visual picture of two black holes forming at 1 AU must be wrong, because if that really did happen (somehow) then it would require something weird like dark matter participating in drawing down the angular momentum.  Dark matter does interact gravitationally with ordinary matter, but I don’t understand how dark matter could come along and cause two black holes to fall together.


There’s just too dang much I don’t know.



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