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Re: LHC Dangerous?

Posted: Mon Feb 09, 2009 3:30 am UTC
by Sir_Elderberry
Yeah, looking back, I'm not sure that my post was quite what he was looking for, but eh.

Re: LHC Dangerous?

Posted: Mon Feb 09, 2009 4:37 am UTC
by baragon-kun
thats my point

how do you know that the micro black holes will be so slow, what are the mechanism, such as the ones discussed on the papers of mangano and giddings, as well as the ones from benjamin koch, horst stocker & Marcus bleicher http://arxiv.org/abs/0807.3349

mechanism such as

Bondi Acrretion
and formulas to know how stable mini black will be slow enough

Re: LHC Dangerous?

Posted: Mon Feb 09, 2009 10:31 pm UTC
by baragon-kun
on another thing

i will admit that i was a little exceptic about the debunking of Rossler arguments, but now i preety much see why this guy should not be taken seriously

http://onscreen-scientist.com/?p=47
http://refugeesfromthecity.blogspot.com/2009/01/soft-underbelly-of-scientific.html

Re: LHC Dangerous?

Posted: Thu Feb 12, 2009 10:23 pm UTC
by cass j
Yakk wrote: First, the post you quote (from a comment on an environemtal website) talks about 5 GeV black holes. We have colliders that are well beyond that.


Misprint. Tev, as should be obvious from the rest of the post.

Yakk wrote: So, that's just either sloppy or plain dishonest.


Sloppy. Was tired.

Yakk wrote: At, say, 100 GeV, the black hole has 20 times the mass of a proton.


That would be 107 times Mp.

Yakk wrote: Let's look at the rate it soaks up particles.

As the black hole slows down, it soaks up particles slower, as the volume it etches particles out per second decreases.

cross section = k * mass^(2/3)
area/time = cross section * velocity
velocity = momentum/mass
so...

area/time = k*momentum / (mass^(1/3))

Ie: the black hole soaks up fewer particles per second as it gains mass, at least until it starts using attraction to soak up particles.


The Schwarzschild radius is proportional to M, the crossection is proportional to M^2. When the MBH has increased in mass by a factor f by accretion, due to conservation of momentum its velocity has decreased by the same factor. But its crossection is increased by a factor of f^2. So its rate of accreting, proportional to the VOLUME(not area!) swept out in unit time is proportional to f. It is accreting exponentially at a rate proportional to its mass.

Yakk wrote: As gravity is extremely extremely weak, that won't start being a factor for a long while.


Exponential process. Depends on the e-time or you can calculate by the doubling time. Wildly unknown. A mass equivalent to 5000 neucleons will grow to the mass of the earth in approx 160 doublings.

---

Yakk wrote: And then on top of this, you have the neutron star problem. Neutron stars are dense, and would be able to trap some of the black holes that form from cosmic rays.

As neutron stars aren't black holes, they must either evaporate or not form...


Neutron stars are not as robust an argument as most suppose, but certainly better than the persistence of the vastly less dense objects in the solar system which isn't a guarantee at all. I brought up some of the problems with Prof Mangano of the CERN LSAG. Here is an email I sent him after he prompted me to redo the calculations which convinced me that white dwarfs were the best assurance of safety from planetary catastrophe:

Dear Professor Mangano

Thank you. You seem to have all the bases covered, and have shown considerable patience. I also know that you are doing the math, and not just a public relations exercise. You've made me look again at things I only considered superficially.

Thought of the poles of the neutron star, but assumed any one easily detectable would have a magnetic axis not aligned with the spin axis.

Considered mBHs produced by cosmic rays on a companion body, but worried frame dragging near the neutron star might force the approaching mBH to be deflected enough to miss. Definitely greater than escape velocity if no first contact.

Never even thought of neutrinos. Had no idea they could be so energetic, and didn't know their crossection increases with energy, so very significant in neutron stars. Not affected by the mag field, and allow a neat way to sneak around the frame drag*.

Also considered very energetic neutrons produced by cosmic rays striking nuclei within 700 light seconds / [1-(v/c)^2]^1/2 to allow for the distance the neutrons can travel before decaying. They would not be deflected by the magnetic field, however powerful. Again frame dragging near the neutron star was a worry, if the deflection is powerful enough. Did no actual calculations(translation, not sure how to even start!).

Also considered old spun-down pulsars with weak fields. An mBH with a crossection of approx 10^-38m^2(Greg Landsberg's guesstimate) would sweep out a volume of 2x10^-34m^2 if it transected the whole 20km diam. For a 2 solar mass neutron star with 2.4x10^57 nucleons, the average volume occupied by one of them is only 1.75x10^-45. So the mBH would cut out the volume of over 10^11 nucleons, not even allowing for the growth of the crossection during the accretion. The mBH wouldn't even get to the other side.

Only trouble with that is the difficulty of noticing the difference if the galaxy is full of 2Mo black holes of 6km radius as opposed to old 2Mo neutron stars of 10km radius! I think other effects besides radio pulses should help out here, but I'm just learning as I go along.

I considered white dwarfs, but rejected them based on an order of magnitude calculation(literally on the back of an envelope!) that showed an initially relativistic mBH still exiting with over escape velocity. It seems that is a borderline case, so have to recalculate. I naively assumed constant density, and did not take into account the growth of the radius of the mBH as it accreted 10^5 nucleons! Allowing for the increase in crossection, and the fact that the density goes up rapidly with the mass, white dwarves are surely the best bet, because there are so many of them. The science is well understood, not speculative at all, and their ages give us reason for confidence. Lots of them are binary, even better odds.

*Possibly the neutron star frame drag could be avoided by a neutron or locally produced mBH approaching exactly along the spin axis. But companion bodies, and the highest concentration of other material acting as the local n or mBH sources, are likely to be in the rotational plane of the neutron star, just like an accretion disk. But very high energy cosmic neutrinos should be isotropic, and not subject to the same constraint at all.

I must say I'm glad you were kind enough to reply to my queries. I was really worried by all the "black hole factory", and "don't worry(waving a wand, and uttering the magic words) Hawking Radiation, will make them evaporate" and "mosquitoes" nonsense! I thought everyone at CERN had gone mad, and weren't looking at the weakness of the arguments about cosmic rays on Earth or the Moon. And the worst was the amazing assumption that the growth of an mBH, with a built in positive feedback, would be linear "and take longer than the age of the universe to gobble a milligram" of Earth.

A single mBH with initial mass of 5000 nucleons that lasted long enough to start accreting, would gobble the earth in about 160 doublings in an exponential process*, because the factor is 2^160=10^48 approx, and the product is 5x10^51, > the 3.6x10^51 nucleons in the Earth.

*Would only level off (as per logistic equation) when an appreciable fraction of the Earth was inside the BH.

It wasn't the alarmist sites that were alarming, it was CERN's "safety at the LHC" page!

Best regards

cass j

---

Yakk wrote: On top of that, you just quoted a CRACKPOT RED FLAG post that is an ANONYMOUS comment ON A NON-PHYSICS website, and claimed that IT IS A PHYSICIST.


I told Mangano I was a concerned layman, as I said in my very long original post.

Yakk wrote: AND in about 30 minutes of EFFORT, I just went and found a massive gaping HOLE in the only bit of his mathematics that I BOTHERED TO TRY TO TEAR APART.


No you didn't. Your effort would have been better spent if you knew that the Schwarzschild radius is proportional to M.

Yakk wrote: The rest of the numbers seem to be hand-wavey as well. "Oh look, error margins ! It must be even less reliable than that!" without actually saying what magnitues are consistent with current observations.


Einstein's claim that the bending of light past the sun was twice as much as predicted by Newton't theory was controversial. Within three years it was verified by Eddington's observations of the 1919 eclipse(he organized two simultaneous expeditions to S Africa and S America).

When a new theory revises a requirement by a factor of 15, 30, or even 60+ magnitudes, then it is not unreasonable to ask if we really know what we are doing, especially when there is no experimental evidence to allow us to chose from competing predictions that differ by extraordinary ranges of magnitude.

Yakk wrote: On the other hand, I have:
http://doc.cern.ch//archive/electronic/ ... 910333.pdf
http://doc.cern.ch/yellowrep/2003/2003-001/p1.pdf
which are a research document done by people not working at CERN, which contains physics models that I can't dismiss with a few minutes of math effort.


Not surprised.

Interestingly, the LSAG report, which is more robust, dismisses many of the arguments of its predecessors(and , bizarrely, the CERN safety at the LHC webpage that raised the alarm rather than assuaged fear).

White dwarfs are the best bet for safety. Actually far more robust than neutron stars because of the magnetic field issue, sheer numbers, age, proximity of so many(Sirius B is only twice as far as Proxima Centauri), and general ease of study and direct observation.

cass j

Re: LHC Dangerous?

Posted: Wed Feb 18, 2009 9:10 pm UTC
by hitokiriilh
It will destroy us all. All you scientists are just arrogant and will doom us all!
/sarcasm

Re: LARGE BLACK-HOLE-CREATOR OF DOOM! Dangerous?

Posted: Thu Feb 26, 2009 5:13 am UTC
by baragon-kun
from now on let just ignore the false information that mr walter wagner posted here, people like him sadly will never learn and will never get satisfied, (seriously did you think we wouldnt notice how you are)

silly manchild, i feel sorry for you :roll:

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 10:02 am UTC
by Anubis
There is nothing to worry about. No micro black holes will be produced, because string theory is bunk.

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 3:34 pm UTC
by gmalivuk
Care to back that up with any evidence or even just a little bit of speculation from any real scientist?

Also, micro black holes being produced isn't actually dependent on string theory in the first place, so even if you're completely correct, that's pretty irrelevant to this discussion...

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 4:07 pm UTC
by Chfan
Why did people think the micro black holes would kill us? Did they not believe in Hawking radiation or were they just following the sensationalization choo-choo train?

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 4:37 pm UTC
by PM 2Ring
Chfan wrote:Why did people think the micro black holes would kill us? Did they not believe in Hawking radiation
Well, micro black holes can only last long enough to do anything if Hawking radiation doesn't happen, or at least if it works differently than expected, eg due to string theory related effects. So there's not much point discussing them at all if Hawking is right (which most of us expect to be the case). Still, it's nice to have all bases covered.
Chfan wrote: or were they just following the sensationalization choo-choo train?
Mostly.

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 4:38 pm UTC
by belmosco
lots of scientists have worked to create this great machine. so there won't be any problem. :D :D :D

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 9:17 pm UTC
by Anubis
gmalivuk wrote:Care to back that up with any evidence or even just a little bit of speculation from any real scientist?


Plenty of "real" scientists have speculated along those lines. However, I cannot provide any actual evidence, since string theory is basically non-falsifiable at this point.

gmalivuk wrote:Also, micro black holes being produced isn't actually dependent on string theory in the first place, so even if you're completely correct, that's pretty irrelevant to this discussion...


http://en.wikipedia.org/wiki/Micro_black_hole wrote:In familiar three-dimensional gravity, available technologies do not reach the minimum Planck mass required to produce a black hole. However, in scenarios where there are extra dimensions of space in certain special configurations, such as large extra dimensions, and special cases of the Randall-Sundrum model and String theory configurations like the GKP solutions, the Planck mass can be as low as the TeV range. In these circumstances, it was argued in 2001 that black hole production could be an important and very visible effect at the Large Hadron Collider (LHC)[6][7][8][9] or future higher-energy colliders.


I know Wikipedia isn't the best source, but you could easily verify that information elsewhere.

Re: LHC Dangerous?

Posted: Sun Mar 01, 2009 11:34 pm UTC
by doogly
Anubis wrote:
gmalivuk wrote:Care to back that up with any evidence or even just a little bit of speculation from any real scientist?


Plenty of "real" scientists have speculated along those lines. However, I cannot provide any actual evidence, since string theory is basically non-falsifiable at this point.

gmalivuk wrote:Also, micro black holes being produced isn't actually dependent on string theory in the first place, so even if you're completely correct, that's pretty irrelevant to this discussion...


http://en.wikipedia.org/wiki/Micro_black_hole wrote:In familiar three-dimensional gravity, available technologies do not reach the minimum Planck mass required to produce a black hole. However, in scenarios where there are extra dimensions of space in certain special configurations, such as large extra dimensions, and special cases of the Randall-Sundrum model and String theory configurations like the GKP solutions, the Planck mass can be as low as the TeV range. In these circumstances, it was argued in 2001 that black hole production could be an important and very visible effect at the Large Hadron Collider (LHC)[6][7][8][9] or future higher-energy colliders.


I know Wikipedia isn't the best source, but you could easily verify that information elsewhere.


Large extra dimensions, the Randall Sundrom model - these are not string theory. Perhaps you have decided string theory is bunk before knowing the least thing about it?