Prolonging Life Beyond a Million Years

This post is about a preprint I recently came across on the scientific arXiv: Retaining Earth’s Habitability Beyond the Life of the Sun by Gabriel Harry. It offers several 'mega-engineering' solutions to the problems likely to arise, e.g. from the million year expiry date on the Sun and the difficulty of transporting civilization via interstellar voyages to other solar systems (or roaming around in spaceships indefinitely).

The paper identifies 7 main threats and their proposed solutions.

1. Sunburns and Hypothermia: Problem - The Sun, as part of the life-cycle as a star, is going to become brighter first (and burn everything on Earth) and then dimmer (too cold to support life on Earth). Proposed solutions - To counter increasing solar luminosity, we can remove some material from the Sun (e.g. using Dyson swarms, i.e. mirrors which focus the Sun's own light to blast away parts of it), or erect a sunshade of gigantic proportions. To account for lowered luminosity, we can set up fusion reactors on the nearby planets (e.g. Jupiter) with nuclear fuels and beam this energy on to the Earth's surface.

2. Staying out of the Sun: Problem - The Sun will also increase in radius and eventually swallow the Earth. Proposed solutions- Increase the orbital radius of the Earth by using a slingshot technique (gravitational assist).

   
   

   The quickest method might be to use a single big object to swing the Earth out to a bigger orbit, but this technique might be prone to miscalculations, leading to possible collisions with Earth (and wiping out everything but bacteria!). So better to use smaller objects repeatedly, giving incremental shifts. Starlifting, e,g, using Dyson swarms as above, might also help, by 'cutting the Sun down to size'.

   
   

3. A long day in the Sun - Problem - The Earth and the moon are eventually going to be locked tidally, which implies an Earth day longer than a month. This will clearly disrupt all kinds of schedules (including that of the posting of this blog). Proposed solution - Make smaller, artificial, suns with the appropriate orbital period, and have them circle the Earth.

   
   

4. Shift happens: Problem - We are slowly losing the original heat from the Earth's formation that drives tectonic movements essential for reshaping the Earth's surface, regulating the global climate, creating diverse habitats through mountain building, and recycling vital nutrients necessary for organic life.  Proposed solution - Drill a big hole and send an anti-matter engine into the core of the Earth to heat it up again.

   
   

5. Dehydration: Problem - Soon (on a cosmic timescale) all water will evaporate from the Earth. Proposed solutions - Take water from Jupiter (its atmosphere has substantial amounts), or Hydrogen and Oxygen from other planets (and combine them).

   
   

6. Going Bump: Problem - Collision with astrophysical objects will endanger, if not end, life on Earth. Most dangerous objects belong to the solar system (apparently Mercury is a threat). Proposed solutions - Solutions have already been demonstrated for small asteroids, and basically consist of batting them out of the way. Presumably this technique can be scaled up for larger objects using nuclear payloads.

   
   

7. Hit by the Big Blast: Problem - Big firecrackers in the universe - e.g, supernova explosions - might pose a threat. Solution - Move the Sun out of the path of harm (taking the solar system with it). I will let you read the paper for the engineering details.

   
   

   Summary: A mind-expanding article. It is clearly impossible to deal with all the complexity of the problem in 13 pages. But if you want to think big, these are the kinds of papers that need to be read (and written; hint - do a word search of the pdf for 'relatively easy').

   
   

   What made the article interesting to me is that all proposed solutions are based on current technology. It is interesting to see the estimates of the resources and energies required. I also found it interesting that a sizable literature dedicated to these problems already exists. Somebody needs to think about this stuff!