The Solar System is a real waste of space, all things considered. The wattage that Earth and the rest of the material contents of the system absorbs as a percentage of the energy emitted by the Sun overall is negligibly close to zero. A billion identical such planets could be inserted into the system just in a naive Klemperer Rosette, and that's a child's-play solution. Add a reasonably intelligent mathematician to the equation and you may be up to a trillion, still without substantial tidal problems or irritating occlusions on any of the outer Earths.

Cast out a map of the current Solar System and the really interesting bits are the space lanes, the cosmic transit network. These are invisible mathematical formations which indicate low-energy, high-efficiency routes between points in the System. For example, if you're travelling from Earth to Mars, there are various routes you can take and a certain bare minimum quantity of kinetic energy needed to convert into gravitational potential to push you that far out of the gravity well. For a given quantity of delta-vee (and a small hyper-economical people carrier like our subject today has a reasonable capacity for this before refuelling even if it can't accelerate too hard) there is also a shortest-transit-time route. Given lots of ships and lots of traffic (both people and cargo) there are certain routes which everybody is going to want to take at once. These morph over time, obviously; depending on where Earth and Mars are, it can take you two hours or thirteen.

Legally permissible routes are published by space transit authorities in the form of computer-consumable mathematical formulations. You have to stay on a legal route, the alternative is to completely program your own plan, which is (a) incredibly mathematically complex, (b) exceptionally dangerous if miscalculated (don't want to hit something, or fly too close to the Sun, (c) almost completely without official support if you run out of fuel and can't make another correction when you arrive and end up blasted out of the System entirely and (d) illegal for all of the above reasons. You might as well try to drive a car where there are no roads.

And because the routes are public and strictly finite in number everybody takes the same routes so they get busy. One has to allow for the safe distance between ships and when they're travelling at thousands of kilometres per second, the relative speeds involved become instakill dangerous, so a gap of several minutes is strictly mandated by flight computer regulations. So there are bottlenecks in space. The queue, for example, for the first dive past Phobos and back towards Luna can get long at peak seasons -- that is, when the two are on the same side of the Sun.

And this is the stuff that Jik-The-Junior loves: the maps and the computations and the big three-dimensional holographic model of the space lanes and the way it modulates and changes shape over time. When the family is travelling Jik-The-Senior usually gathers them around and they play videogames but Junior loves watching the screens and the readouts and the ship-exterior sensorium.

"Dad, what does 'AVOID EARTH, TURN ON RADIO' mean?"

They're thirty-five minutes out from Nairobi Line Top. Or were. "Give me the headset." Junior does this. This doesn't involve literally removing a piece of equipment from his head and handing it to his father (which is good, because up until a few years ago both of them would have needed shaved heads to interface with the equipment). The handover is electronic. Jik-The-Senior sends out a confirmation-of-receipt signal in response to a "hey, wake up and tell us you received this" data packet broadcast to all the ships in the inbound lane. This response is mandatory; having an intelligent human being sat in control of the ship is mandatory. Letting Junior take over is technically against the law but he is learning to fly and under strict instructions to hand stuff over if he gets the kind of message he just got, although none of them have ever seen that exact message.

J-Senior opens up the radio. This is not a euphemism. Radio travels at the speed of light. There is no relativity violation. Still, the broadcast includes audio and video. At least, this close to Earth, the news will be properly up-to-date. The big blue globe rolls underneath them.

"--you can see hundreds of people being escorted out of the liftport right now, of all ages and races, those people you see escorting the crowds are workers for the liftport ground control system, that's what you can tell by the insignia on their shoulders there. You can see, uh, automated surface transit trains entering the terminal also, we think that's for evacuation purposes too. There are ambulances lining up outside but from what we understand there is still very little in the way of official movement towards the Terminal Six building itself and, if, um, if what I was told just a few minutes ago is to be believed there still isn't. We're now being told that a safe distance of eight miles is being recommended but at this stage it is extremely unclear how safe this is if reached, nor how practical it is to evacuate to that distance."

"Thank you, the main story once again: Nairobi Tower's Electromagnetic Descent Control Room at Nairobi Line Top has been seized by a group of Gabonese militants. The EM descent controls have been shut down, freezing all lift passengers in transit between Liftport base and the High Nairobi terminal. Ships docked at Line Top have been instructed to leave for Lunar orbit and inbound traffic to all Earth spaceports have been instructed to do the same."

"I just want to interrupt you there: it looks like the plan is becoming clearer. As you know the secondary purpose of the entire Earth space elevator system is electricity generation: metal ores are mined from captured asteroids and sent down the elevator in canisters similar to the passenger cars. The descent generates kinetic energy which is used to drive electricity through a coil wrapped around the bulk of the space elevator, so at the same time as receiving ore at ground level the descent of the ore is slowed to a safe speed and most of the city of Nairobi is powered by the generated energy, including the spaceport. With these controls shut down and the automated safety interlocks defeated, the ore canisters will fall at an unchecked rate. As we feared this means there are probably something of the order of two hundred such ore canisters headed down here, each of them containing more than a hundred tonnes of ore in addition to the mass of the canisters themselves. Each of them essentially therefore constitutes a-- hold on, something's happening, do you see that?"

The scene is a flat white city built on top of a huge flat brown and green expanse but the city itself is not the interesting bit: the skyline is dominated by a white skyscraper protrusion with red-painted sections which goes all the way from the ground into space. It's a dizzying sight. The space-tree branches into ten distinct segments as it reaches ground level, each segment wired into a separate complete self-contained liftport terminal joining the main section, incidentally visually underlining the fact that the port is not built up from the ground but suspended from geostationary orbit. The tower is ridged and lined with slots where the external cars travel.

The camera which is now at least two miles from the liftport complex itself is trained as high into the sky as its focal length will manage. What it sees is a descending lift car, one of the extra-large yellow ore containers. It's sliding down one of the lift slots towards the complicated network where it'll get turned horizontal, shunted over towards a waiting rail car and transferred out for processing. But this one, a klick in altitude, is descending far too fast. In fact, this whole thing happens in a fraction of a second (and the hundred or so distinct videos of the event will have to be stitched together to uncover what exactly is happening), and the canister goes from a klick to zero in a fraction of a second. It hits ground level so fast that the parabolic arc which is supposed to turn it horizontal can't take the force and disconnects under the stress, and the canister hits the ground hard instead of, as you'd expect, being fired out across the city at incredible speed. Then there's an explosion.

"I--"

And then the shockwave hits the camera crew.

And they cut back to the news room. "I-- well, we've just lost contact with our camera crew, but if there are other canisters descending then they'll have had time to gather more speed than the previous one, so each impact will be successively larger. Um."

Jik calls for the ship to turn around, but in practical terms that means they will have to dive under the Earth and loop around back in the direction they came. That necessitates a close approach within visual range of the Halo itself. As they're making the correction and beginning to accelerate through, his sensorium locates more significant flashes down on the ground: the Brazilian Tower has been used to bomb its own base as well. As hours pass, the hair-thin yellow spindle which marks the Halo begins to crackle and change shape, and finally crumple like paper.