Thursday, November 15, 2012

Speculation - the only way to fly


Ronald Bracewell
Here is another speculation, but probably not very original. In fact, it's a variation on the 1960 concept of a Bracewell Probe.  It's hard for me to imagine that some science fiction author or another hasn't treated this in some form.

In the future, we expect to be able solve these three broad classes of technological problem we haven't got a a handle on yet:
  1. Very large sensors that can remotely sense distant planets accurately enough to ascertain their habitability with a high confidence.
  2. The hosting of a human mind on a machine substrate - i.e. a truly intelligent machine.  This implies that the state of a human mind could be captured - "uploaded" onto a machine and captured in a data set. In other words, we could completely define what we now call the "self" in terms of data.  The crucial thing here (within an order of magnitude or so), is how much data.  Let's say it's about an exabit compressed, or  10^18 bits.  Some estimates are lower that, but I think we need lots of margin.  
  3. Travel across interstellar distance, although the problems of doing so quickly ( a significant fraction of the speed of light and exploiting time dilation effects) may prove to be insurmountable no matter how sophisticated our technology is, and at present we have only the broadest concept of how to cheat the speed of light limit.
Let's assume we could do both 1 and 2, but item 3 could only be done slowly, so that it takes hundreds or even many thousands of years to travel between the stars.  This would be a hopelessly tedious journey for a human or superhuman intelligence, and all the mass required for reliable life support would only slow it down and limit options for deacceleration.

So, we would want to send only a small mass to another star system and it would take a long time and cost a lot of energy.   However, we can transmit information far more cheaply and at the speed of light.  You might need a really big and powerful transmitting array, but this is just scaling up from current technology.  To transmit an exabit in a year you would need a transmission rate of about 30 gigabits per second -  well within plausibility, even over interstellar distances.  The size of the receiving antenna you would need on the other side would increase with the distance (roughly 100 meters on a side at 100 light years, given plausible assumptions about  the transmitter, noise temperature and losses), but such antennas can be made from gossamer materials that can be folded compactly.




So, our probes arrive over centuries at various star systems, probably in highly elliptical orbits with periods of hundreds of years.  They unpack themselves, check on their own health, report back, and and start looking around.  They will be looking for suitable sites where energy and materials can he harvested efficiently, allowing the colony to prosper.  Given that our civilization has survived long enough, he first transmissions from Earth will be a library updating all the knowledge stored on board the spacecraft: all the whats, whys and hows needed to understand, build and maintain the next generation of technology.

Dust Mites
When the first of our descendants finally arrive in digital form (possibly following a few retransmits of dropped data packets), they will be loaded into small postbiological bodies awaiting them, with all the energy harvesting equipment, actuators and sensors (that they had been training with on Earth) that they will need to assure their safety and prosperity.  These bodies may be very small indeed, less than a gram, given the huge energy costs for transporting an interstellar payload.  The minimum size may well be constrained by the simple need to shed heat generated by high rates of information processing, and we could be talking about people not much larger than dust mites (about a milligram).

Successful colonies will retain their technical knowledge and begin building the infrastructure they need to make the next leaps to other star systems.  However, some colonies may well fail, or may simply be content with where they are, even merging with local biospheres.  As Landis has properly pointed out, such colonies would inevitably reject homeworld control and develop their own agendas, and possibly quite a diverse set of visions for their destiny. However, only a few have to succeed at each stage to ensure  propagation throughout much the galaxy.

This is how we patiently but inexorably colonize the galaxy; not as rugged pioneers in multi-generational interstellar Conestoga wagons, but as a streams of bits flying across space at the speed of light, with the physical infrastructure we already need to survive and explore waiting for us when we arrive.

Well, it's just a speculation, and I can anticipate plenty of objections.  What do you think?



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Dream of the Open Channel by Paul Carr is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.