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Astrochemistry
Reactions: More discussion of space elevators, plus care with significant figures
August 23, 2024
| A version of this story appeared in
Volume 102, Issue 26
Letters to the editor
More on space elevators
Howard Mark’s comments on the Periodic Graphics article about space elevators were very much to the point (C&EN, Aug. 5, 2024, page 5). I would like to add one other comment.
The space elevator design discussed in the article is the type often discussed in the scientific (and science fiction) literature. It consists of a space station well above the height of geostationary orbit, anchored by an extremely strong cable to a point on Earth. Freight and passengers are conveyed up or down the cable. As Mark points out, the anchor point has to be on the equator.
Because the station is at a height at which its orbital velocity would be much lower than that of a geostationary satellite, it is dragged along by the cable. Thus the cable is under a good deal of tension. As Mark points out, the anchor point has to be on bedrock in a seismically stable location. That anchor must be extremely strong.
The length of the cable is given in the article as 100,000 km, which is more than twice Earth’s circumference. If or when the cable fails, it will fall on the equator. Depending on the point of failure, it may wrap itself all the way around Earth, destroying anything on the equator—unless it burns up completely on reentry. That appears unlikely. Even if it does, it would leave thousands of kilometers of superhot vapor that could start fires over a large portion of the tropics.
It appears that a space elevator would require permanent evacuation of the entire equatorial zone to avoid the large loss of life that would otherwise result from a cable failure.
James M. Castro
Helena, Montana
Significant figures
The second paragraph of your editorial on microplastics in the June 10/17 volume (page 2) was disappointing for an American Chemical Society publication. Giving five significant figures and no standard deviation for the average concentration of a highly variable measurement such as microplastics in humans and dogs is disrespectful of the limits of the data.
I fear that the authors fell into the religious trap of thinking scientific numbers must always have two significant figures to the right of the decimal point. My guess, given the type of data, is that it might justify three significant figures, but more likely two. Especially in an editorial, you are setting the example. Thank you.
Joe M. Regenstein
Ithaca, New York
Chemical & Engineering News
ISSN 0009-2347
Copyright © 2024 American Chemical Society
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