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

He handed the picture to Emerson who, after passing it to Harvey Smith, said:
"It's certainly grown enormously over the twenty years. I'm a bit apprehensive
about what's going to happen in the next twenty. It seems as if it might cover the
whole constellation of Orion. Pretty soon astronomers will be out of business."
It was then that Dave Weichart spoke up for the first time.
"I've two questions that I'd like to ask. The first is about the position of the
cloud. As I understand what you've said, the cloud is growing in its apparent size
because it's getting nearer to us. That's clear enough. But what I'd like to know is
whether the centre of the cloud is staying in the same position, or does it seem to
be moving against the background of the stars?"
"A very good question. The centre seems, over the last twenty years, to have
moved very little relative to the star field," answered Herrick.
"Then that means the cloud is coming dead at the solar system."
Weichart was used to thinking more quickly than other people, so when he
saw hesitation to accept his conclusion, he went to the blackboard.
"I can make it clear with a picture. Here's the Earth. Let's suppose first that
the cloud is moving dead towards us, like this, from A to B. Then at B the cloud
will look bigger but its centre will be in the same direction. This is the case that
apparently corresponds pretty well to the observed situation."
There was a general murmur of assent, so Weichart went on:
"Now let's suppose that the cloud is moving sideways, as well as towards us,
and let's suppose that the motion sideways is about as fast as the motion
towards us. Then the cloud will move about like this. Now if you consider the
motion from A to B you'll see that there are two effects - the cloud will seem
bigger at B than it was at A, exactly as in the previous case, but now the centre
will have moved. And it will move through the angle AEB which must be
something of the order of thirty degrees."
"I don't think the centre has moved through an angle of more than a quarter
of a degree," remarked Marlowe.
"Then the sideways motion can't be more than about one per cent of the
motion towards us. It looks as though the cloud is heading towards the solar
system like a bullet at a target."
"You mean, Dave, that there's no chance of the cloud missing the solar
system, of it being a near-miss, let us say?"
"On the facts as they've been given to us that cloud is going to score a bull's
eye, plumb in the middle of the target. Remember that it's already two and a half
degrees in diameter. The transverse velocity would have to be as much as ten
per cent or so of the radial velocity if it were to miss us. And that would imply a
far greater angular motion of the centre than Dr. Marlowe says has taken place.
The other question I'd like to ask is, why wasn't the cloud detected sooner? I
don't want to be rude about it, but it seems very surprising that it wasn't picked
up quite a while ago, say ten years ago."
"That of course was the first thing that sprang to my mind," answered
Marlowe. "It seemed so astonishing that I could scarcely credit the validity of
Jensen's work. But then I saw a number of reasons. If a bright nova or a
supernova were to flash out in the sky it would immediately be detected by
thousands of ordinary people, let alone by astronomers. But this is not something
bright, it's something dark, and that's not so easy to pick up - a dark patch is
pretty well camouflaged against the sky. Of course if one of the stars that has
been hidden by the cloud had happened to be a bright fellow it would have been