Posted on August 1, 2004

Soapbox Seminar #4

Jackson-Ryan Bites the Dust!

It all started out at the exit.

Remember how Al Jackson and Mike Ryan predicted there’d have been an “exit event” later the same day as the impact? Here’s how they put it in their 1973 Nature article:

Because of its high velocity and because it loses only a small fraction of its energy in passing through the Earth, the black hole should very nearly follow a straight line through the Earth, entering at 30° to the horizon and leaving through the North Atlantic in the region 40°-50° N, 30°-40° W.

Well, they did more than predict it; they went and bet the farm on it:

This exit provides a check for the whole hypothesis. At the exit point there would be another air shock wave and an underwater shock wave and disturbance of the sea surface, Microbarograph records could be checked for an event similar to that caused by the entry shock displaced by the proper amount of time. Oceanographic and shipping records could be studied to see if any surface or underwater disturbances were observed.

Now, don’t get me wrong: When a new theory makes predictions that can be empirically tested, that’s a good thing. And the crazier the theory, the more it’s got to have that kind of verification. It was this same sort of thing that finally brought Newtonian physicists around to Einstein’s way of thinking, for instance, once the observations of the precession of Mercury during the 1918 eclipse matched the predictions of General Relativity.

Still and all, it was because of that “exit event” prediction that Mike and Al got to watch their brand-new hypothesis go down the tubes within a year of its publication.

And, most mortifying of all, it was a couple of naturalized fellow Texans that did them in.

In 1974, William H. Beasley and Brian A. Tinsley from the University of Texas at Dallas wrote in to Nature to say “We have examined copies of the English microbarograph records, but have been unable to find any sign of waves from the suggested exit explosion.” There was more, but what it came down to in the end, was:

All the evidence favours the idea that the impact which caused the Tunguska catastrophe involved a body with characteristics like a cometary nucleus, rather than a black hole.

That wasn’t all.

Even as he was writing up the original article, Mike says he’d been worried about what other detectable effects the hole might’ve had, both on impacting the earth, and while tunneling through it. In the end, he and Al went with some handwaving about how “the black hole would leave no crater or material residue” as it plunged into the earth at the impact site, and how once inside the earth “the rigidity of rock would allow no underground shock wave.” And, what with one thing and another, they somehow never got around to running the calculations that would have checked all that out.

But somebody else did.

In 1976, Jack O. Burns, George Greenstein, and Kenneth L. Verosub drove the final nail in the coffin. Their paper in the Monthly Notes of the Royal Astronomical Society started out promisingly enough:

The apparent uniqueness of this [Tunguska] event requires that all possible explanations must be seriously considered and that no explanation can be discarded merely because it has a low probability of occurring.

But things went downhill from there.

Burns, Greenstein, and Verosub started out with the power of the impact — cited by E. L . Krinov at somewhere between ten and forty megatons — and worked backwards. Assuming all that energy had to come from gravitational effects alone (no friction mechanics for a micro black hole — it slices through ordinary matter like it wasn’t there, remember?), that meant the Jackson-Ryan hole would have had to weigh somewhere between ten quadrillion and one quintillion tons. A little on the high side versus Al and Mike’s guesstimate, but what’s an order of magnitude or two ‘mongst friends?

Then Burns and company took it one step further. They figured what would happen when that same mass, that same gravitational energy touched down on earth. According to them —

[T]he point of entry of the hole into the Earth should be marked by a patch of melted and resolidified rock of diameter 1/2 to 4 kilometres, overlain by fused soil of comparable extent.

Wow! A disk of fused earth and melted rock maybe three miles wide and Lord knows how thick. Bet that’d have been hard to miss!

But Burns, Greenstein, and Verosub weren’t done yet. They also calculated the effect of the hole’s gazillion-ton mass burrowing through thousands of miles of the earth’s crust and mantle. The answer? “[S]everal thousand simultaneous earthquakes,” each of them as big or bigger than the most powerful earthquake ever recorded.

Now, the international physics community already had their backs up over Jackson-Ryan — a knee-jerk reaction, maybe, to the amount of play the idea was getting in the mass media. So, once the Beasley-Tinsley and Burns-Greenstein-Verosub papers came out, all hell broke loose.

With characteristic understatement, Al Jackson simply says “Well, we took some guff from some people, not too bad.” As Mike recalls it, “A number of physicists came down on me with Al’s ‘what a piece of crap.’” In particular, a Princeton celebrity professor was “furious” with the two of them. According to Mike:

Said professor spoke to me later at a conference, and when I said the idea was dead because of no exit shock, he said that we should quickly write an article squashing the theory before it could get into the popular literature and cause “bad craziness” (advice we never took).

Even Carl Sagan hopped aboard the bandwagon. Rent the video of Cosmos Episode IV, “Heaven and Hell” (better yet, buy the DVD here), and you’ll see Carl pointing out how “the records of atmospheric shock waves show no hint of an object booming out of the North Atlantic later that day.” The no-exit-event objection, in other words.

What had started off as a simple debate over a new hypothesis was turning into a game of astrophysical pile-on.

Russian researchers, who sometimes seem to think like the Tunguska Event is their private preserve, routinely went ballistic at just the mention of the Jackson-Ryan hypothesis. Roy Gallant reports that our old friend Academician Nikolai V. Vasil’ev was still steamed about it two decades later, in 1992:

If Jackson and Ryan had bothered to acquaint themselves with the geophysical materials published in Russia and America before publicizing their fantastic idea, they most likely would never have proposed it. Evidently the authors, in their naivete, supposed that in 1908 such a cataclysmic event as a black hole exploding out of the North Atlantic Ocean would have gone unnoticed. However, the population of the eastern regions of Canada, Iceland, and southern Greenland was significant. Those people published newspapers and had meteorological stations and observatories, and there were dozens of vessels in the open ocean. Furthermore, a tsunami would have been generated. Under these circumstances the event could not possibly have gone unnoticed.

If professional scientists indulge themselves in such liberties, you can imagine how readily such science fiction notions will be eagerly and gullibly seized by the mass media... The sad results are disoriented public opinion and complications in the further study of this complex natural phenomenon.

It wasn’t only the Russians, of course. We’ve already seen how Tom Gehrels, the principal investigator for Operation Spacewatch, went out of his way to lump Jackson and Ryan’s “mini-black hole” hypothesis in with UFO crash-landings as “nonsensical speculation” as late as the mid-nineties.

But they were all beating a long-dead horse. Far as the world physics community was concerned, by the late seventies Jackson-Ryan had already crashed, burnt, and got shoveled over with dirt. Tunguska researchers could breath a sigh of relief and go back to fighting over meteorite this, and cometary that. Even Al Jackson and Mike Ryan pretty much forgot about it. It sure looked like the end of the line.

Or maybe not. Leastways, I hope to be able to convince you that — be it right or wrong — the Jackson-Ryan hypothesis isn’t “naive,” or “science fiction,” or “nonsensical speculation,” or any of the other names folks have called it over the years. That — right or wrong — it’s no less scientific than any of the more widely held theories. And that, as Burns and his friends pointed out, in a situation where “all possible explanations must be seriously considered and ... no explanation can be discarded merely because it has a low probability of occurring,” it might just possibly be right.

But to see how it might be right, we’ve first got to take a closer look at those primordial black holes.

[Notes and Further Reading]

William H. Beasley and Brian A. Tinsley, “Tungus event was not caused by a black hole,” Nature, vol. 250, August 16, 1974, pp. 555-556.

Jack O. Burns, George Greenstein, and Kenneth L. Verosub, "The Tungus Event as a Small Black Hole: Geophysical Considerations," Monthly Notices, Royal Astronomical Society, vol. 175 (1976), pp. 355-357.

Roy A. Gallant, The Day The Sky Split Apart: Investigating a Cosmic Mystery, Atheneum, 1995. [Click here to order]

Roy A. Gallant, Meteorite Hunter: The Search for Siberian Meteorite Craters, McGraw-Hill, 2002. [Click here to order]

Tom Gehrels, “Collisions with Comets and Asteroids,” Scientific American, March 1996, pp. 54-59.

Albert A. Jackson, IV and Michael P. Ryan, Jr., “Was the Tungus Event due to a Black Hole?” Nature, vol. 245, September 14, 1973, pp. 88-89.

Special thanks again to Al Jackson and Mike Ryan for sharing their personal reminiscences of the aftermath of their Tunguska paper.

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