Planet Defense

View 824, Sunday, May 11, 2014

If a foreign government had imposed this system of education on the United States, we would rightfully consider it an act of war.

Glenn T. Seaborg, National Commission on Education, 1983


Today ends the Spring pledge drive. This is the last pitch about money you’ll hear for a while (well, there may be a similar announcement in the mailbag I’m hoping to get prepared before midnight). As we have said often, this site runs on the Public Radio model. It’s free to all, but it will not stay open unless it gets enough subscribers. I do want to thank all those who chose to subscribe this week, and particularly the new subscribers.

If you have never subscribed to this place, this would be a good time to do it. If you have subscribed, but it has been a while since your renewed – if you can’t remember when you renewed your subscription – this would be a great time to do that. I won’t be reminding you of it for a while, so do it now while you’re thinking about it…


It appears overwhelmingly clear that the alien attack on the Taliban was Photoshopped, and I have to confess I never thought otherwise because the remarks from those taking the movie didn’t mention the object, just the bombardment. Of course I have just been to a lecture by Claudio Maccone, who is well known for his interest in SETI (Search for Extra Terrestrial Intelligence) and also for planet defense – Space Defense if you will. That’s something Niven and I have been interested in for decades. (See Yesterday’s View)

Planetary defense usually means defense against impacting objects, but there are other views.

Alien contact

My whole problem with contacting aliens has always been; what if they think humans are as tasty as we consider lobster? Have we ever asked the lobsters about their civilization? Pretty much "No"! Why would you expect a space traveling race to be so noble? They will arrive here hungry after traveling so far. Best to not be the main course…

bill brunton

Those who read FOOTFALL by Larry Niven and Jerry Pournelle will know that we do not assume the “they’re friendly and here to help us” view, nor do they want to eat us. Our aliens have a very complex social order. Of course stories about Earth resisting invaders have become more common since we wrote Footfall (and they weren’t rare before we wrote it) but we did work on the question of “If they can cross interstellar space, why don’t they just snuff us and have done with it? What chance have we got?” Footfall was our first novel to make Number One on the publisher’s best seller list, and we’re rather proud of it, and despite having been written before the end of the Cold War it holds up pretty well.


As it happens I got this today also:

What is your take on this?

Clean Up Space Junk or Risk Real-Life ‘Gravity’ Disaster, Lawmakers Say <>

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Clean Up Space Junk or Risk Real-Life ‘Gravity’ Disaster… <>

While the plot of the hit Hollywood film \"Gravity\" is fictional, the United States must bolster efforts to address the alarming amount of space junk s…

View on <>


You have worked extensively with the space program, so tell me it this is so?

1) Except in rare cases when we want a polar orbit or something unusual, we launch satellites in the direction the Earth spins because that is the economical in terms of energy usage? So most of the satellites move in the same direction.

2) If two Satellites are moving in the same direction but at different speeds, they are in different orbits? So one will be at a different altitude than the other.

3) Even if two satellites are moving at different speeds and/or directions (due to elliptical orbits or not having exactly the same vector) would the difference be enough to cause serious damage?

Everything sent to orbit is launched eastward because that’s the way the world turns, and you want to add rather than subtract the rotational velocity to the velocity change (Delta-V) achieved by the rocket engines. It also makes the clock lose time ( ) but that’s a story for another time.) But of course the latitude from which it is launched will play a big part in determining the orbit the satellite will have after it reaches orbital velocity. In general, the rocket will pass over its launch site. A satellite launched on the equator will more or less stay jut over the equator at all times; one launched from Kazakhstan will go that far north during every orbit.

This establishes a lot of orbits, and space is very large. Space junk can be a real danger, but again, space is very large. The Wikipedia article on Space Debris is fairly good (or was when last I looked). The danger of space debris as present is often exaggerated, particularly by those who want to be paid to clean it up, but it is not something to be ignored forever.

Incidentally, while the US and Russia and the other powers wanting to become space faring nations have a shortage of the capability to get stuff into orbit, there is an even more critical lack of the ability to get garbage and waste out of space. One proposal is for a “streamlined” garbage net to be tethered to Space Station, since any mass put in orbit has a potential use if we ever build a more sophisticated space station. In any event, waste accumulation can be a problem. There are a number of science fiction stories written about space junk causing critical accidents, and of course there is the movie Gravity.


I don’t know if this has anything to do with what Dr. Maccone was working on or if there is a metric that could apply, but I define civilization thus:

That person is civilized who, having the means and opportunity to compel another against his will with impunity and profit thereby, refuses to do it because he believes it is wrong.

Richard White

Austin, Texas

Dr. Maccone’s metric for level of civilization is bits/person, a measure of information processing divided by the number of people in the civilization. The main critique I have of the measure is the denominator: you can change the metric by eliminating the low information members of the population. One can imagine situations in which survivors of a nuclear war would retain much of the technology, and quickly recover to become a considerably higher level of civilization (according to the metric) if the size of the denominator falls greatly relative to the numerator.

I will have more to say on this another time. Maccone’s mathematics was beautiful; and do understand this is a first cut at a metric that would allow us to compare ours with an alien civilization. If I ever have time I may try guessing the metric for the Fithp, the aliens in our novel Footfall, compared with Earth…


Once again this is the close of the Spring Pledge Drive, and I will no longer be bugging you about subscriptions to this place. This site operates on the Public Radio Model. It is free to all, and we try to keep it interesting. It can only stay open with your support. If you have not subscribed, this would be a great time to do that. If you have subscribed but have not renewed in a while, or can’t remember when you last did, this is the right time to renew.





Freedom is not free. Free men are not equal. Equal men are not free.




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