The latest selections from the SPACE.com mailbag…

Gentry Lee's latest column contemplated whether intelligent aliens exist, and what they might think of humans. Readers respond.

To the Editor:

In his article "Are We Alone?" Gentry Lee writes:

"What would they conclude from their observations that our species...is also still spending an enormous percentage of its gross world product on weapons of destruction?"

Josh Chamot's article "Acidic Clouds Responsible for Ozone Depletion" sparked a skeptical response from reader John Jarrell. Now, more readers enter the fray, including SPACE.com contributor John Shirley.

To the Editor:

Someone wrote in expressing an understandable and probably commonplace confusion -- how can ozone depletion problems be caused by supercold clouds yet somehow connected to global warming and doesn't this mean, they wonder, that global warming is bunk...? Basically what is happening is that global warming happens lower in the atmosphere, down in the greenhouse created by particulate pollution of various kinds as well as excessive CO2, and the ozone depletion caused by these frozen clouds happens up very high in the atmosphere. In terms of warmth and cold, they are two separate systems -- yet everything in the atmosphere is related. So yes, both are possible at once and can be interrelated.

John Shirley
 
 

To the Editor:

Regarding John Jarrell's letter (in response to your article "Acidic Clouds Responsible for Ozone Depletion") in which he sneers at the idea that man-made ozone destruction can occur, and that this can be accelerated by global warming: Would it be asking too much for him to actually read a few articles on the subject in the regular science journals (forget the environmental magazines) before shooting off his mouth? Any of the dozens of pieces Science and Nature have run on the subject in their news sections over the past two decades would suffice.

If he did, he'd learn that:

(A) Even the skeptics about man-made global warming agree that global warming in the lower atmosphere from any source (man-made or natural) paradoxically lowers the temperature of the upper atmosphere.

(B) Even skeptics about man-made ozone destruction (of which there are now very few) agree that tiny traces of chlorine -- which is released in the upper atmosphere when man-made CFCs are broken down by solar ultraviolet light above the ozone layer -- can destroy vast numbers of ozone molecules by acting as a catalyst.

(C) They also agree that this reaction is tremendously accelerated on the surfaces of water-ice crystals, especially when they also include traces of nitric acid (NOT nitrogen, which freezes at a tremendously lower temperature). And the colder the stratosphere, of course, the more water-ice clouds there are in it.

Mr. Jarrell may not be a member of "the cult of the Earth Mother," but I wish he was a member of the cult of people who actually know something about science, or can read a news article and actually understand what was clearly stated in it.

Bruce Moomaw

Greg Clark's article "Will Nuclear Power Put Humans On Mars?" brought a critical letter from reader Tony Vasquez, who worried about the possible effects of a nuclear accident in space. Now, readers respond to Vasquez.

To the Editor:

In his recent letter, Tony Vasquez asks, "If the Challenger shuttle that exploded after launch had had 77 pounds (35 kilograms) of enriched uranium aboard, where would that uranium have gone?"

I assume he's worried about radioactive material being scattered around Florida. The answer however is that the material would have remained inside its explosion-proof container, fallen into the ocean and been later recovered by NASA salvage vessels. No one would have been exposed to anything dangerous.

The biggest problem with using nuclear power in space is not technical; it is getting the nuclear bugaboo out of the public's perception. Until we change the equation "nuclear = bad" in the mind of the public, forget about nuclear anything in space.

Bill Roman
Sterling, Virginia
 
 

To the Editor:

In a response to "Will Nuclear Power Put Humans on Mars?" Mr. Tony Vasquez asked where a nuclear reactor would go if one were present on board the space shuttle Challenger in 1986. I have an answer for him:

The bottom of the ocean, in one piece. From there it'd be recovered, and the fuel would probably be useful for a later space mission.

If you want an analogy of what the Radioisotope Thermoelectric Generators (RTGs) look like, think of a brick, or, more precisely, a rounded brick. This structure is hard to break, much less vaporize into the millions of particles required to cause the environmental catastrophe that space-nuclear-power opponents tout as the only outcome of a launch failure.

Considering the fact that many pieces of Challenger survived intact, I doubt that the energy was sufficient to destroy an RTG, assuming one was on board.

If you want to show environmental concern, I'd be more worried about where the tons of hydrochloric acid, hydrazine and nitrogen tetroxide did go when the Challenger exploded. Space travel is a difficult business, and while it holds promise to become easier in the future, I don't believe we should do nothing in wait for that time.

Tom Hill
Olney, Maryland

And finally, for now, a word about Battlefield Earth. For James Pinkerton's opinion piece about the movie, click here. For Kenneth Silber's review, click here.

To the Editor:

It is ironic that every column I have read that reviews this movie is obviously written by someone who has not read the book. I realize that most would be daunted by such a hefty book, but if they read it, I am sure that an understanding of the movie would come about. The characters and story line are done totally tongue-in-cheek, with no one character or scene truly taking itself seriously, yet the story doesn't acknowledge that this is the case, it just plows on into telling the story. Travolta is correct that it is a page turner, it is the kind of book that as you read, you say to yourself, I can't believe I am reading this, but I can't put it down....

In that light, I imagine the book and the movie have many more points in common than the critics give it credit for.

David S. Hawkins
Haverhill, Massachusetts