[X] My Assistant

[Guest_PhilCo126_*]

The Near-Earth Asteroid 99942 Apophis ( former designation 2004 MN4 ) was headline news again this week both in Newspapers & TV news. Observations pointed out that the Asteroid climbed a bit higher on the Torino impact hazard scale ( equivalent cosmic ‘Richter’ scale ) and could hit the Earth ( Southern Hemisphere ) on April 13, 2036 ( a Friday 13th I believe ).

Anyway, Apophis should pass between the Moon & Earth ( distance 250.000 KM ) in April 2029 … an amazing sight visible from Europe!
Interesting to know is the fact that European Space Agency ESA plans a mission to find out if an asteroid could be deflected from its course ( Don Quichote mission: Hidalgo is an impacter & Sancho is the observer probe ). American astronauts LU & LOVE wrote a paper in NATURE about a tug-rocket and NASA is making plans for a mission called ‘ The Son of Deep Impact ‘ … to be continued…



More on the Asteroid at:
http://www.esa.int/gsp/ACT/mission_analysis/asteroid.htm


Philip

[Guest_Richard Trigaux_*]

Important things in the discutio above, JRehling, RNeuhaus, dvandorn:


To avoid a future collision with an asteroid, it is enough to give it a very small push at the right moment (just before a close encounter with a planet) and this is mostly achievable with today or near future technology.

The chaotic aspect of their trajectory, which makes this trajectory difficult to predict, especially after a close encounter (this is called, I think, sensitive dependency to initial conditions) turns to our advantage: a very small tug just before a close encounter allows to completelly change the future trajectory.

Eventually crashing all the Earth threatening objects on other planets is not a bad idea. This would allow us for a safe future, even in the case in which we abandon any high technology.

By the way, nuking asteroids, as it was proposed by some who have nukes but who rather don't know what to do with, is just sheer deliria: the asteroid would be broken apart, but all the pieces would continue on the same trajectory (this is basic celestial mechanics). So, in place of receiving a huge asteroid, we would receive several small ones, plus the radioactive wastes of the bomb. It is not sure that it would be better.

[tty]

By the way, nuking asteroids, as it was proposed by some who have nukes but who rather don't know what to do with, is just sheer deliria: the asteroid would be broken apart, but all the pieces would continue on the same trajectory (this is basic celestial mechanics). So, in place of receiving a huge asteroid, we would receive several small ones, plus the radioactive wastes of the bomb.  It is not sure that it would be better.

Actually that idea is not as silly at it sounds. The idea was to blow a nuclear charge some distance from the asteroid. The energy would vaporize a thin surface layer on the exposed side. The vaporized material would blow away at high speed and the recoil would change the asteroid´s trajectory slightly.

Now the biggest problem in changing asteroid trajectories is probably that many (most?) asteroids are just rubble piles, very weakly bound by gravity. Most apparently less violent ways to move an asteroid would probably also break it up.

This is the beauty of the "gravity tug concept". Since it is based on gravity it affects all of the asteroid in the same way and there is no breakup. The downside is that it is quite slow.

In cases where the warning time is short (say a few years or less) the "Nuclear recoil concept" may actually be the best bet. If the charge is exploded at some distance and a directed-energy design is used the "push" will be nearly parallell and approximately the same all over the asteroid so the breakup forces shouldn't be too bad.

It would of course be a good idea to try it out on some non-earth crossing asteroid first.

tty

[Bob Shaw]

I hate to point out a grim and downright unsettling aspect of extinctions, but by any reasonable use of the term we're currently slap bang in the middle of one of the worst multiple extinctions ever seen - and all (or at least mostly) down to the activities of our own species over the last few thousand years. All we need is a big impact, a super-volcano or whatever, and our degraded natural environment may go downhill even more rapidly.

Time for a lifeboat, methinks!

Bob Shaw

[Guest_Richard Trigaux_*]

I hate to point out a grim and downright unsettling aspect of extinctions, but by any reasonable use of the term we're currently slap bang in the middle of one of the worst multiple extinctions ever seen - and all (or at least mostly) down to the activities of our own species over the last few thousand years. All we need is a big impact, a super-volcano or whatever, and our degraded natural environment may go downhill even more rapidly.

Time for a lifeboat, methinks!

Bob Shaw

Yes it is true that mankind activity resulted into many species disappearing, and many natural environment destroyed, and this is not just today, late prehistory men were already able to extinct species and destroy forests with flintstone axes. Today with technology we are just faster.

This is why I think that the survivability of any planetary civilization heavily relies on its "wisdom" about managing its natural environment, respecting it or at least exploiting it without degrading it each year more. This ecology wisdom is not unrelated with a more philosophical/spiritual wisdom, if we consider that in last analyse it is egocentricity of individuals which produces threatening pollutions, destructions, wars, etc. We can imagine authoritarian regimes willing to preserve environment, but they are subjects to revolutions which could result in a resurfacing of egocentric/predatory behaviours. So a freely accepted philosophical choice is an indispensible prerequisite, but it is still not enough: many countries (USSR) or philosophical movements tried to foster altruism (or at least enough citizen sense) but failed because they proposed no practical mean to really change our mind and become selfless. Only some buddhist or similar countries succeeded, because they proposed both the target (becoming non-selfish) the methods (spiritual works) and evidences of their success (successful communities based on some altruism) to convince selfish people, the whole set in a non-violent and non-authoritarian way. And it was not a 6 month plan, most usually it was rather 6 centuries to succeed. So the success of the human specy to survive relies on something like this, not on any technology or administration. Today we can begin to foster this awareness and encourage people who are able to help in this, in place of forming lobbies for burying our hands in the sand about climate change and the like.

We have not so much time: when climate temperature increases, there is more steam in the air, and steam is in turn a greenhouse gas. So greenhouse effect has a positive reaction onitself, in clear it can suddenly start to increase limitless: in some years we would have a temperature of 100°C or more on all the Earth. No doubt there would be some trouble with the stock exchange.