“And on its opacity, and a hundred and one other factors,” added Kingsley. “I must say it seems very unlikely to me that much heat will get through the gas. Let’s work out the energy required to heat it to an ordinary sort of temperature.”
He went out to the blackboard, and wrote:
Mass of Cloud 1.3 ? 1030 grams.
Composition of Cloud probably hydrogen gas, for the most part in neutral form.
Energy required to lift temperature of gas by T degrees is 1·5 ? 1·3 ? 1030 RT ergs
where R is the gas constant. Writing L for the total energy emitted by the Sun, the time required to raise the temperature is 1·5 ? 1·3 ? 1030 RT/L seconds
Put R = 8·3 ? 107, T = 300, L = 4 ? 1033 ergs per second gives a time of about 1·2 ? 107 seconds, i.e. about 5 months.
“That looks sound enough,” commented Weichart. “And I’d say that what you’ve got is very much a minimum estimate.”
“That’s so,” nodded Kingsley. “And my minimum is already very much longer than it will take the Cloud to pass us by. At a speed of 80 kilometres per second it’ll sweep across the Earth’s orbit in about a month. So it looks to me pretty certain that if the Cloud does come between us and the Sun it’ll cut out the heat from the Sun quite completely.”
“You say
“There’s certainly a chance, quite a chance I’d say. Look here.”
Kingsley moved again to the blackboard.
“Here’s the Earth’s orbit round the Sun. We’re here at the moment. And the Cloud, to draw it to scale, is over here. If it’s moving like this, dead set for the Sun, then it’ll certainly block the Sun. But if it’s moving this second way, then it could well miss us altogether.”
KINGSLEY’S DRAWING OF PRESENT SITUATION
KINGSLEY’S DRAWING OF SITUATION IN SIXTEEN MONTHS’ TIME
“It looks to me as if we’re rather lucky,” Barnett laughed uneasily. “Because of the Earth’s motion round the Sun, the Earth will be on the far side of the Sun sixteen months hence when the Cloud arrives.”
“That only means that the Cloud will reach the Sun before it reaches the Earth. It won’t stop the sunlight being blocked out if the Sun gets covered, as in Kingsley’s case (
“The point about your cases (
“That’s exactly it. Of course my case (
“Do we have anything to say about whether the Cloud is coming dead at the Sun or not?’ asked Herrick.
“Not on the observational side,” answered Marlowe. “Look at Kingsley’s drawing of the present situation. Only a very slight difference of velocity makes a big difference, all the difference between the Cloud hitting and missing. We can’t say yet which it’s to be, but we can find out as the Cloud comes in nearer.”
“So that’s one of the important things to be done,” concluded Herrick.
“Can you say anything more from the theory?”
“No, I don’t think we can; the calculations aren’t accurate enough.”
“Astonishing to hear you distrusting calculations, Kingsley,” remarked the Astronomer Royal.
“My calculations were based on your observations, A.R.! Anyway I agree with Marlowe. The thing to do is to keep a close watch on the Cloud. It should be possible to see whether we’re going to have a hit or a miss without too much trouble. A month or two should settle it, I suppose.”
“Right!’ answered Marlowe. “You can rely on us to watch this fellow from now on as carefully as if it was made of gold.”
After lunch Marlowe, Kingsley, and the Astronomer Royal were sitting in Herrick’s office. Herrick had explained the plan of writing a joint report.
“And I think our conclusions are very clear. May I just outline them for you?
1. A cloud of gas has invaded the solar system from outer space.
2. It is moving more or less directly towards us.
3. It will arrive in the vicinity of the Earth about sixteen months from now.
4. It will remain in our vicinity for a time of about a month.
“So if the material of the Cloud interposes itself between the Sun and the Earth, the Earth will be plunged into darkness. Observations are not yet sufficiently definitive to decide whether or not this will occur, but further observations should be capable of deciding this question.”
“And I think we can go a little further concerning future observations,” Herrick went on. “Optical observations will be prosecuted here with all energy. And we feel that work by the Australian radio astronomers will be complementary to ours, particularly with regard to keeping a watch on the line of sight motion of the Cloud.”
“That seems to sum up the situation admirably,” agreed the Astronomer Royal.
“I propose that we proceed with the report at full speed, that we four sign it, and that it be communicated to our respective Governments forthwith. I hardly need say that the whole matter is highly secret, or at least that we should treat it as so. It is rather unfortunate that so many are aware of the position, but I believe that we can rely on everybody proceeding with great discretion.”
Kingsley did not agree with Herrick on this point. Also he was feeling very tired, which no doubt made him express his views rather more forcibly than he would otherwise have done.
“I’m sorry, Dr Herrick, but I don’t follow you there. I see no reason why we scientists should go to the politicians like a lot of dogs thumping our tails, saying “Please, sir, here’s our report. Please give us a pat on the back and perhaps even a biscuit if you feel so disposed.” I can’t see the slightest point in having to do with a crowd of people that can’t even run society properly during normal times when there’s no serious stress. Will the politicians pass statutes to stop the Cloud coming? Will they be able to prevent it cutting off the light of the Sun? If they can, then consult them by all means, but if they can’t, let’s leave them out of the picture altogether.”
Dr Herrick was quietly firm.
“I’m sorry, Kingsley, but as I see it the United States Government and the British Government are the democratically elected representatives of our respective peoples. I regard it as our obvious duty to make this report, and to maintain silence until our Governments have made a pronouncement on it.”
Kingsley stood up.
“I’m sorry if I seem brusque. I’m tired. I want to go and get some sleep. Send your report if you wish, but please understand that if I decide to say nothing publicly for the time being, it will be because I wish to say nothing, not because I feel under any form of compulsion or duty. And now if you’ll excuse me, I’d like to get round to my hotel.”
When Kingsley had gone, Herrick looked at the Astronomer Royal.
“Dr Kingsley seems a trifle … er …”
