"Fred Hoyle - The Black Cloud" - читать интересную книгу автора (Hoyle Fred)

spotted. The disappearance of a bright star is not so easy to detect as the
appearance of a new bright star, but it would nevertheless have been noticed by
thousands of professional and amateur astronomers. It happened, however, that
all the stars near the cloud are telescopic, none brighter than eighth magnitude.
That's the first mischance. Then you must know that in order to get good seeing
conditions we prefer to work on objects near the zenith, whereas this cloud lies
rather low in our sky. So we would naturally tend to avoid that part of the sky
unless it happened to contain some particularly interesting material, which by a
second mischance (if we exclude the case of the cloud) it does not. It is true that
to observatories in the southern hemisphere the cloud would be high in the sky,
but observatories in the southern hemisphere are hard put to it with their small
staffs to get through a host of important problems connected with the Magellanic
Clouds and the nucleus of the Galaxy. The cloud had to be detected sooner or
later. It turned out be later, but it might have been sooner. That's all I can say."
"It's too late to worry about that now," said the Director. "Our next step must
be to measure the speed with which the cloud is moving towards us. Marlowe and
I have had a long talk about it, and we think it should be possible. Stars,on the
fringe of the cloud are partially obscured, as the plates taken by Marlowe last
night show. Their spectrum should show absorption lines due to the cloud, and
the Doppler shift will give us the speed."
"Then it should be possible to calculate how long the cloud will be before it
reaches us," joined in Barnett. "I must say I don't like the look of things. The way
the cloud has increased its angular diameter during the last twenty years makes
it look as if it'll be on top of us within fifty or sixty years. How long do you think
it'll take to get a Doppler shift?"
"Perhaps about a week. It shouldn't be a difficult job."
"Sorry I don't understand all this," broke in Weichart. "I don't see why you
need the speed of the cloud. You can calculate straight away how long the cloud
is going to take to reach us. Here, let me do it. My guess is that the answer will
turn out at much less than fifty years."
For the second time Weichart left his seat, went to the blackboard, and
cleaned off his previous drawings.
"Could we have Jensen's two slides again please?"
When Emerson had flashed them up, first one and then the other, Weichart
asked: "Could you estimate how much larger the cloud is in the second slide?"
"I would say about five per cent larger. It may be a little more or a little less,
but certainly not very far away from that," answered Marlowe.
"Right," Weichart continued, "let's begin by defining a few symbols."
Then followed a somewhat lengthy calculation at the end of which Weichart
announced:
"And so you see that the black cloud will be here by August 1965, or possibly
sooner if some of the present estimates have to be corrected."
Then he stood back from the blackboard, checking through his mathematical
argument.
"It certainly looks all right - very straightforward in fact," said Marlowe, putting
out great volumes of smoke.*


* The details of Weichart's remarks and work while at the blackboard were as
follows: