Isaac Asimov’s How Did We Find Out About Black Holes

About a month ago, Blake over at Science After Sunclipse posted an image of some of his early kindergarten science scribblings.  That got me thinking about my own early interest in science, and the sources that motivated me.  While visiting my Mom’s house in Chicago (and helping clear out some of my old junk from the basement, at her insistence), I came across a wonderful little book that had a big impact on me: Isaac Asimov’s charming little book, How Did We Find Out About Black Holes:


Judging from the publication date of this Scholastic Book — 1978 — I was probably in first  or second grade when I read it.  It is a marvelous little book, outlining the relevant advances in astrophysics from 1848 (the first evidence of white dwarf stars observed by Friedrich Bessel) to the early 1970s and the first supposed discovery of a black hole, an x-ray source known as Cygnus X-1.

The writing is concise, clear, and utterly gripping.  I still enjoy reading it now, even though it is a children’s book!   A sample:

In 1844, a German astronomer, Friedrich Wilhelm Bessel (BES-ul), discovered a star he couldn’t see.

This is how it happened.

All the stars we see in the sky are moving about.  They are so far away from us, though, that the motion seems very slow indeed.  Only by making careful measurements through the telescope will the motion show up as very tiny changes in position.

Even using the telescope won’t help much.  Only the nearest stars show changes in position when compared with dim, distant stars so far away that they don’t seem to move at all.

One of the stars nearest to us is Sirius (SIR-ee-us.)  It is about 50 trillion miles away, but that is close for a star.  It is the brightest star in the sky, partly because it is so close, and its motion can be measured easily through a telescope.

Bessel wanted to study that motion carefully,  because as the earth goes around the sun, we keep seeing the stars from slightly different angles.  Instead of seeing a star move in a straight line, we see it move in a line that wiggles slightly because of the earth’s motion.

The nearer the star, the larger the wiggle.  From the size of the wiggle, if it is carefully measured, the distance of a star can be calculated.  Bessel was particularly interested in this.  In fact, he was the first astronomer ever to calculate the distance of a star.  He did that in 1838.

He then became interested in measuring the wiggle in Sirius’s motion.  As he measured the position of Sirius night after night for a long time, he found that there was more of a wiggle to its motion than he had expected.  It changed position because the earth was revolving around the sun, but there was another change in position too — a slower one that had nothing to do with the earth.

Bessel concentrated on this new movement and found that Sirius was moving in an orbit around something or other, just the way the earth moves in an orbit about the sun.  He calculated that it would take Sirius fifty years to complete its orbit.

But what caused Sirius to move in this orbit?

There’s a lot of information in that short section, and as a child I ate it all up.  My interest in physics would wane for years after I lost interest in the book, but it was the initial spark which got me started in science.

Asimov’s work is at least a partial answer to a question posed in a post at Cocktail Party Physics:  “Does science fiction matter? At all?  Even a little?”  I would certainly say yes:  when science fiction writers decide to write nonfiction science, the results can be wonderful!

When I started researching this post, I found out that Asimov actually wrote a large collection of “How did we find out about…” books.  For fun, I’ve ordered “How did we find out about Pluto?” and “How did we find out about volcanoes?”, and I’ll come back to them in later posts.

Any other scientists out there want to share their earliest inspirations to get involved in science?  Feel free to leave a comment!

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5 Responses to Isaac Asimov’s How Did We Find Out About Black Holes

  1. Blake Stacey says:

    Asimov’s birthday is tomorrow. I need to post something to celebrate!

  2. Dawn says:

    Thanks for the post! I’m homeschooling my kids and picked up a couple of books in this series. I handed my 11 yr. old daughter the Atoms book, she groaned but read the first chapter and decided it was fantastic. Now I’m trying to hunt down the whole series to be part of our science and came across your post in my googling. Nice to hear that it inspired a future scientist!

  3. akak says:

    I loved this book as an 8-year-old… I even made my own audio book of it, dictating it into my little panasonic tape recorder. I hope to find a copy for my daughter now!

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