This week's subjects, all born in the 1940s, hold the distinction of still being alive at the time of this writing.

    The first is Stephen Hawking (1942- ), one of those rare scientists whose presence has penetrated the popular media. Though few would claim to fully understand his ideas, his unique appearance has made him an icon in pop science circles.

    The "unique appearance" I mentioned is due to a disability: he suffers from amyotrophic lateral sclerosis (ALS), popularly known as "Lou Gehrig's disease" (after an American baseball player who was diagnosed with the nerve-destroying disease in 1939).

    Commencing during his university years, over the course of his life the disease has left him almost entirely paralyzed and unable to speak. This has led to the use of his trademark wheelchair (which he is known to drive like a maniac), and the familiar voice created by a voice synthesizer (now controlled by the action of a single muscle in his cheek).

    He has beaten the odds: given a two-year life expectancy at age 21, he is now 73 years old!

    He has downplayed the importance of his disease, saying he wants to be thought of as "a scientist first, popular science writer second, and, in all the ways that matter, a normal human being with the same desires, drives, dreams, and ambitions as the next person."

    And what a scientist! The title of this article comes from a TV series about his work, which encompasses refinements of Einstein's theory of general relativity, as well as a major theory about radiation from black holes.

    His 1988 pop science book "A Brief History of Time" is subtitled "From the Big Bang to Black Holes." Despite the intimidating title, it has been a bestseller for decades, and has been translated into at least 35 languages. Later editions go beyond "hard science" to speculation on time travel, wormholes, and alternate universes.

    In addition to numerous high honors in his native England, Dr. Hawking has also received the Presidential Medal of Freedom in the United States.

    Vocabulary: Which word above means:

    1. device used to make the sound of someone speaking

    2. unable to move

    3. frightening

    4. physical impairment

    5. crazy person

    6. scientific knowledge as understood by everyday people

    7. made little of, gave small importance to

    8. determined by a doctor

    9. characteristic, how someone can be identified

    10. amount of time someone is predicted to live

    ANSWERS: 1. voice synthesizer 2. paralyzed 3. intimidating 4. disability 5. maniac 6. pop science 7. downplayed 8. diagnosed 9. trademark 10. life expectancy