Starship Walker

The Wall Passage

A day later, Mr Rogers and his team completed their analysis and mapping work. They found that the wall was ten light years wide across the galactic plane, and appeared to be over one hundred light years tall. It was like a gigantic vertical blind. The Xinglong Hao was four light years from its closest horizontal boundary, and at least forty-five light years from its top boundary. Its distance from the bottom was uncertain.

"But that's not all we've found," Mr Rogers said, at another meeting chaired by Captain Xing in his conference room.

Gillian had decided that the wall, though bizzare, was nothing special for her. One way or another, they would get around it.

But then Mr Rogers added: "We've also discovered a black hole at each end of the wall."

As the shock of this news subsided, Mr Rogers added, "The black holes are orbiting around each other, so over a period of several hundred years the wall between them is rotating. We've found a bizarre star system, but we can't imagine what's created it."

"It sounds like a gigantic cosmic swizzle stick," Abel Yegg remarked.

"Or a revolving door," Mr Dryen added. He asked, "How close are the black holes to the horizontal ends of the wall?"

"It depends what you mean by 'End'," Mr Rogers replied. "The wall doesn't have a hard boundary, it just gets less and less dense. Gillian can start crossing through its sparse zone as soon as we can identify a suitable passage and complete a risk analysis for the ship - and for Gillian."

"Just for the record," Captain Xing said, "I need to be assured that there are no other alternatives to finding a passage through the wall. For example, why can't we go over the top or the bottom of it?"

Mr Rogers answered, "Our instruments can't detect the wall's boundaries in the vertical plane, because both ends disappear too far into galactic clouds. We can't conclusively identify an end in either direction."

The Captain nodded. "I just needed to confirm that."

Abel added, "Our entire galaxy is like a gigantic sponge, made up of gas and dust clouds, and the clouds are full of cavities and tunnels. The ship is inside a tunnel through the galactic cloud, and the Wall is blocking it."

"Very well," Captain Xing said, "I'm happy for passage planning to commence. But I'm especially concerned that we take extra precautions. I particularly mean increased safety margins, since we'll be in unknown territory as well as the vicinity of a black hole."

"I agree, Captain," Mr Dryen said.

Abel added, "I'm sure that suits Gillian - er, Mr Berry."

"Will we feel anything when we're near the black hole?" Gillian asked.

"No," Mr Rogers said. "It's just a nearby star as far as we're concerned, like any we need to stay aware of when they're a light year or so off our course. We'll be in its gravitational field, but we won't get close enough to it to give us problems."

"Whether it's a black hole or a star," Mr Dryen added, "Depending on our distance, we may need to start the ship's engines. Every time Gillian completes a step, we're subject to gravitational forces that combine with the vector we had when we left the Gliese system."

"And what's our vector relative to the nearest black hole?" Gillian asked.

Mr Dryen replied, "Well, unfortunately, it's about twenty degrees off the direct course for our likeliest passage through the wall, and in favour of the nearby black hole."

"Damn!" Mr Rogers said. "We'll have to work out what that means for Walking. Once she starts, Gillian may not be able to stop and rest until we're well clear."