From Chris Eve, Lynton, Devon, UK
You report that searching for “Star Tugs”, machines capable of moving a sun, could be a new way to find alien civilisations (18 July, p 15). Given the low likelihood of having to dodge a supernova, the example given for ET doing this, perhaps we would do better to seek signs of other, similar technologies.
For example, civilisations may have developed the means to move a sister planet’s orbit into the habitable zone or to change the orbit of their own world to avoid a star’s expansion.
Such projects could involve a cascade of planned changes to the movement of a series of objects of increasing mass, set in train by an initial nudge. These could use gravity, impacts and vast motors.
In the same vein, intense electromagnetic fields generated by a spinning magnetic object have interesting possibilities for planetary-scale engineering. They could attract, repel, change the spin axis or alter the day length of an iron-rich planet.
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