Disaster priorities [was Balloon-Borne Instrument Collects Antimatter]

Robert J. Bradbury (bradbury@www.aeiveos.com)
Wed, 18 Aug 1999 15:55:18 -0700 (PDT)

> Clint O'Dell <clintodell@hotmail.com> wrote:

Re: anti/normal-matter galaxy collissions

> It would be quite scary! I assume that the side with the most matter of its > type would win.

Yes, for those cases where the matter encounters its anti-matter. However, galaxies are mostly empty space. I think the average density is something like 1 atom per cubic meter (someone correct me if they know better). That is why a ramjet collector for interstellar travel needs to be huge. When galaxies, of normal matter, collide now, most of the material (stars, molecular clouds) passes through untouched. The gravitational distortions do change orbits though, sometimes creating collisions. (Think about Jupiter distorting comet/asteroid orbits throwing them at the Earth; its similar with the gravity of the entire galaxy and the stars orbiting in them).

> Is there a way that our side can gain an advantage so that > were not annihilated?!
Well, since the general view is that anti-matter galaxies don't exist, we may not have to worry about it. If that turns out to be true, then we need a really big computer (like a Matrioshka Brain) to compute all the gravitational trajectories and recomend one that lets us (and our star) avoid colliding with something.

> Since annihilation produces pure energy would that hold the > two universes apart in a rhythmic pattern for a while? If enough annihilation were occuring, you would get a fair amount of photon pressure that would provide outward momentum to particles that intercepted it. This would clear out the gas clouds fairly easily but probably wouldn't have much effect on the stars or black holes.

> I'm picturing power much greater than a supernova. Yes, these would be quasars & blazars, but current theories can account for these objects without having to resort to anti/normal-matter galactic collisions.

> How can an anti-matter galaxy and a posi-matter(?) galaxy co-exist? By not getting in each others way. :-)

> Is this because there is nothing between the galaxies? All empty space? There is belief that there may be atomic or molecular hydrogen in the space between galaxies, but the density is very low. All you need is for relatively energetic events in a galaxy (supernovas, star collisions, black holes eating matter, etc.) to give atoms or small molecules enough energy to be traveling faster than the galactic escape velocity and you can kiss them goodbye.

> Not to be million questions or anything but if disaster is possible its > probably worth while to prepare for it now. Well, I think we should balance our perspectives with regard to disasters... I would make up the "worry list" as follows:

Motor vehicles, falls, poisonings, fires, drowning, suffocation, and of course firearms.

Once you have finished not driving, climbing, eating, drinking, swimming, bathing, breathing and playing with guns, you should be concerned with:

After you get finished with all of those, we can discuss the extraterrestrial hazards (or events we should be concerned about), in approximate order of significance, I would say are:
- a meteor(asteroid) strike

Just guessing, I would put
- a collision between matter/anti-matter galaxies
someplace in the middle of the ET hazard list.


P.S. [For those who want to quibble on the details, ~50% of the prioritization are from Dyson's 1979 "Time Without End" paper. So read that before you put me up against the wall to shoot me.]

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