Why did the seed take so long, and the mind so little?
The seed that founded the Vigil weighed 1,000 kg. It was pushed out of the Solar System by a laser at a tenth of light speed, and the trip to a black hole and its star 28 light-years away took 297 years, including the burn of the fusion stage that stopped it. It carried everything needed to start a factory, and carrying and then stopping that cargo is why it could only travel at a tenth of light speed. How it was launched is the story of Pushed by light, and how it stopped is Stopping from 0.1c.
The story treats a mind as a pattern that can be stored, copied and sent. It uses 1 × 1017 bits as an illustrative state size; the information needed to reproduce a human mind is unknown. frontier From Saturn, where the minds set out, a laser 1,000 metres across, aimed at a mirror of the same size at the Vigil, delivers 1.1 × 1016 bits a second.
Guess first How long does the actual transmission of one whole mind take, once the signal is flowing?
About 9.5 seconds of link time. The light still needs 28 years to cross, because nothing outruns light, but the sending itself is measured in seconds, while the seed's flight was measured in centuries. Only 8.8 watts of the sender's 1 × 1012 watts reach the far mirror, and it is enough.
The seed delivers the machinery on a slow initial flight. After that, sending a mind uses 9.5 seconds of a 1 × 1012 watt laser, a small energy expenditure compared with accelerating a probe.
The arriving data reproduce a copy of the transmitted state. Whether that copy preserves personal identity or has conscious experience remains unresolved frontier. The full page on the mind link gives the link budget and discusses these assumptions.