Astronomy

ASTROLETTERS

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Shadow bands

Mr. O’Meara, I was paging through the

February 2018 issue of Astronomy maga-

zine, which arrived a few days ago, and I

noticed your article about Earth’s shadow

bands. While reading it, I was reminded

of our January 2011 trip to Antarctica,

where I took this photo of the Full Moon

rising (11:55 p.m. local time) while we

were in the Lemaire Channel.

The Sun was just setting over my right

shoulder, thus some direct sunlight illu-

minated both the ice f loating in the chan-

nel and the snow-covered mountain in the

distant left. My photo also has Earth’s

shadow and the Belt of Venus, which you

described. Regards, and I enjoy reading

your monthly articles. — Bob Bedell,

Mansfield, TX

The next billion years

I just read David Eicher’s editor’s note for

the December 2017 issue of Astronomy.

Like Mr. Eicher, I often tell myself and oth-

ers that we have less than a billion years

before increasing solar output boils off our

oceans. But then it occurred to me that

even with just a thousand years of effort,

we could likely build a protective barrier

around Earth that limits the amount of

solar radiation we are exposed to.

Such a structure could buy the planet a

few billion extra years of habitability

(though the Sun’s red giant phase would

be a much tougher nut to crack). We could

also maintain the position of our protec-

tive barrier by using highly specific

impulse ion thrusters powered by solar

energy and Moon-mined fuel.

Anyway, all of a sudden (as of 10 min-

utes ago), I’m more optimistic than ever

that the Sun’s increasing power output

doesn’t have to render Earth uninhabit-

able in the next billion years. Assuming

that we don’t wipe ourselves out (which

is very possible), it seems we may have

the capacity to tame our star for at least

3 billion to 4 billion more years.

— Michael W. Schimpf, Pacific Grove, CA

Praise for prose

Tania Burchell’s article on the ALMA

project in the December 2017 issue is eas-

ily worth the cost of a year’s subscription.

Any science writer can lay out the facts

of a subject, although the writing may be

tedious or opaque. In contrast, Ms.

Burchell’s effortlessly graceful prose is a

joy to read. She clearly explains the meth-

ods and findings of the ALMA research-

ers, but also communicates their sense of

scientific curiosity and the joy of discov-

ery. I hope to see more of her lyrical writ-

ing in future. — Michael Silverglat, Missoula, MT

Entropy?

In his November 2017 column “Entropy

redux,” Jeff Hester talks about the Second

Law of Thermodynamics and its build-

ing of structure. He says all of that

complexity (due to increasing entropy)

arose from random and unguided pro-

cesses. I disagree with his assumptions.

Reality already tells me that information

is responsible for complexity and order,

a truth Hester seems to ignore.

In his October 2017 column, Hester

talked about the entropy of an interstellar

cloud that collapsed to form stars and

planets. However, that process had to be

guided by information (that is, by the

inherent laws that govern our universe).

And when we talk about life, any attempt

to use a reduction in entropy to produce

information fails because entropy is not

equivalent to the functional information

in cells.

Also, Hester chides creationists for

their claim that entropy stands in the way

of evolution. Well, Hester also stands in

the way of evolution when he claims that

order arose from random and unguided

processes. Such dogmatic assumptions

prohibit science to explore other possibili-

ties. Mr. Hester, stop holding back science.

Let it be free! — Paul Kursewicz, Epping, NH

Jeff Hester responds

The reader uses the phrase, “Reality

already tells me.” How does that commu-

nication occur? Does reality tap him on

the shoulder and whisper in his ear? Does

it slip him notes under the desk when the

teacher isn’t looking?

Reality doesn’t “tell” us anything.

Reality has to be interrogated. One of the

coolest things about science is just how

surprising and counterintuitive reality’s

secrets can be! Discovering reality means

setting aside assumptions and dogma. It

means brutally confronting ideas with

evidence from observation and experi-

ment, then throwing out the ideas that

can’t take the heat. My articles on entropy

discuss fundamental insights forged in

that unforgiving crucible over the last

century and a half. That doesn’t hold

science back; that is how science works.

The reader is correct that evolution and

structure formation can be discussed in

terms of information. But applying infor-

mation theory doesn’t change the

answers. Contrary to the reader’s asser-

tion, information entropy is equivalent to

the average amount of information pro-

duced by a stochastic (random and

unguided) process. That might make a

fun column ...

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may be edited for space and clarity.

BOB BEDELL