Danielson manoeuvred her chair so she could see. Gantt pointed to the luminescent figures. 'You see the seismometers saturated when it got too close, so they stopped giving any useful information.' He played with the keys some more. 'The gravimeter here in camp also went off scale. They're meant to measure fluctuations of a part in a billion, and this one was at one per cent before it pooped out. The outer stations were fine, though; here's the mass they detected, a bit over ten million metric tons. That's just about what you guessed, wasn't it, Alex?'
'Pretty close,' admitted Runyan. He thought for a while and then asked, 'How long were the seismometers inactive?'
Gantt consulted the computer and then replied, 'Twenty— eight point — well, call it an even twenty-nine seconds, why?'
'Maybe we ought to go back to your tent where we can talk this over,' Runyan replied.
They left the equipment tent and walked towards Gantt's.
Wary glances followed them. All over the camp men stood in groups of three and four, discussing the strange event in muted and not so muted tones. Runyan and Danielson occupied the chairs they had first sat in upon their arrival, only a few hours ago. Gantt disappeared inside idle tent and returned with three styrofoam cups and a bottle of bourbon.
'A bit early in the day for normal circumstances,' he said, 'but I could use a little bracer. Will you join me?'
The other two nodded their acceptance and received their cups in turn. Runyan took a fairly healthy slug and looked on with mild surprise as Danielson drained hers in one quick motion and held it out to Gantt for a refill.
Danielson caught Runyan's look, grinned, and said in a voice hoarsened by the liquor, 'All us Virginians are bourbon drinkers, suh!'
Gantt smiled at the quip and raised his cup to gesture a toast, 'Well, here's to the future: may it not be entirely black.' He continued with a shake of his head, 'I must say that was the most god-awful feeling. I had the definite impression that you people had snuck up on either side of me and lifted my chair and then dropped it. All this instrumentation and electronics are well and good, but they're no substitute for being grabbed and shaken to let you know you're up against the real thing. The idea that that thing actually came up within, what, two or three yards of the tent? Jesus!' He drained his cup and poured another dollop.
'Did you feel a sideways pull?' inquired Danielson.
'That's what bowled me over. I had one foot in the air when someone raised the floor and then gave me a shove.'
'I guess maybe I did,' answered Gantt, 'but I was sitting down, so that took some of the edge off.'
'You're right. The thing must have come up just outside the tent,' Runyan joined in. 'Must have been one of those tunes when it got jarred off course somehow. Actually, in spite of the low probability, it's lucky no one was hit. I was thinking. Pat may have had a good idea: it might be of some interest to find the hole it made coming out and the other falling back in. Apparently that occurred just a bit further to the east, near the edge of camp. I think we may have learned something important here, in addition — to having the wits scared out of us.'
'What's that?' asked Gantt.
'Well, there are three things that come to mind. First, we've confirmed the fact that it comes down near where it went up. That's significant.'
'I thought of that. It's the same as Dallas ,' said Danielson, her eyes shining. 'It must be moving with the same tangential velocity as the surface of the earth as it comes up.'
Gantt looked puzzled, and Danielson explained to him, 'Remember that, because it rotates, the surface of the earth is actually moving at about a thousand miles an hour. If this thing were literally moving on a line pointed at a fixed direction in space, then as it reached the surface we would move out from under it at just that speed. How long did you say it was up? About a half of a minute? Let's see, the earth's surface rotates about twenty miles in a minute or about ten in the time the thing was up.'
'Closer to seven,' said Runyan with unconscious pedanticism, 'but clearly the relative motion could have been much greater than it actually was.'
'I guess I still don't quite see,' began Gantt.
'The point is,' explained Runyan, 'that when it comes to the surface of the earth it's virtually at rest with respect to the local terrain. That can't be an accident. It must have begun that way. We can rule out the idea that it's a naturally occurring black hole. To have it moving at precisely the earth's orbital velocity so that it could be trapped was asking a lot. To insist that it also move in consonance with the rotation of the earth is out of the question. I could never put any store in the idea anyway, but now I think we can really lay it to rest.
'Let me put it another way,' he continued, 'if you were to imagine taking a black hole and holding it in your hand so that both you and it were moving along with the surface of the earth, and then you were to drop it, and let it orbit freely, the result would be just what we have seen. It would drop down, pass to the far side of the earth and return. It must return to precisely the same altitude as that from which it was dropped, and at its highest point, when it momentarily has no velocity towards or away from the earth's centre, it must have precisely the same sideways motion as when it was released. To someone moving with the same motion, that is, with the velocity of the earth's surface, it would seem to come momentarily to an exact standstill.'
'But it didn't stand still,' objected Gantt, 'that is, it continued on up.'
'That's my second point,' replied Runyan. 'One we kicked around in La Jolla. We know how far up it went. It took about fifteen seconds to go up and an equal amount to return. At one gee, that's a distance of about three thousand four hundred feet. What's the altitude here?'
'About twenty-three hundred feet,' said Gantt.
'Then apogee is about five thousand seven hundred feet above sea level. A bit over a mile. That must be the altitude from which it was originally dropped.'
Before either Danielson or Gantt could comment, Runyan was on his feet. 'Let me get something out of my luggage.' He tossed off the remaining bourbon in his cup, set the cup on the chair arm, and strode purposefully over to the mess tent where their luggage had been placed. The cup blew off, and Gantt rescued it from the ground. Runyan rummaged for a moment and then returned with a stack of computer output. He regained his seat and balanced the paper on his knees so he could easily riffle the accordion— folded sheets.
'Another little project of mine,' he explained. 'Pat, you said that in Dallas your agents thought about forty seconds elapsed from the time you first heard the noise to when it returned. That gives an estimate of the altitude to which it rises. I figured they could be off by ten per cent either way. The Seamount event gave a more accurate estimate. I narrowed down the maximum altitude to within three hundred feet. What I've got here is a list of every point on earth which falls along the locus of the orbit and within three bins in altitude, each spanning a hundred feet. With this new precise data of yours, Ellison, we can throw out two-thirds of the possibilities. There are surprisingly few left. Few enough that they can all be checked in a finite time. There are a couple in California , a few in Arizona , a small batch in New Mexico and that's for the continental United States.' He looked on down the list, 'There's a couple of places in Morocco, one in Algeria, some in Iran, Afghanistan, and Pakistan, none in Tibet, it's all too high, and finally, in the northern hemisphere, several places in China.' He flipped to another sheet. 'The southern hemisphere is even more sparse. A few places on either side of the Andes, in Chile and Argentina. That's about it. Everything else is lower, mostly ocean.'