Infinity—Nothing to Trifle With

Snowflake curveThe topic of infinity comes up occasionally in apologetics arguments, but this is a lot more involved than most people think.  After exploring the subject, apologists may want to be more cautious.

Philosopher and apologist William Lane Craig walks where most laymen fear to tread.  Like an experienced actor, he has no difficulty imagining himself in all sorts of stretch roles—as a physicist, as a biologist, or as a mathematician.

Since God couldn’t have created the universe if it has been here forever, Craig argues that an infinitely old universe is impossible.  He imagines such a universe and argues that it would take an infinite amount of time to get to now.  This gulf of infinitely many moments of time would be impossible to cross, so the idea must be impossible.

But why not arrive at time t = now?  We must be somewhere on the timeline, and now is as good a place as any.  The imaginary infinite timeline isn’t divided into “Points in time we can get to” and “Points we can’t.”  And if going from a beginning in time infinitely far in the past and arriving at now is a problem, then imagine a beginningless timeline.  Physicist Vic Stenger, for one, makes the distinction between a universe that began infinitely far in the past and a universe without a beginning

Hoare’s Dictum is relevant here.  Infinity-based arguments are successful because they’re complicated and confusing, not because they’re accurate.

One of Craig’s conundrums is this:

Suppose we meet a man who claims to have been counting from eternity and is now finishing: . . ., –3, –2, –1, 0.  We could ask, why did he not finish counting yesterday or the day before or the year before?  By then an infinite time had already elapsed, so that he should already have finished by then.…  In fact, no matter how far back into the past we go, we can never find the man counting at all, for at any point we reach he will have already finished.

Before we study this ill-advised descent into mathematics, let’s first explore the concept of infinity.

Everyone knows that the number of integers {1, 2, 3, …} is infinite.  It’s easy to see that if one proposed that the set of integers was finite, with a largest integer n, the number n + 1 would be even larger.  This understanding of infinity is an old observation, and Aristotle and other ancients noted it.

But there’s more to the topic than that.  I remember being startled in an introductory calculus class at a shape sometimes called Gabriel’s Horn (take the two-dimensional curve 1/x from 1 to ∞ and rotate it around the x-axis to make an infinitely long wine glass).  This shape has finite volume but infinite surface area.  In other words, you could fill it with paint, but you could never paint it.

A two-dimensional equivalent is the familiar Koch snowflake.  (Start with an equilateral triangle.  For every side, erase the middle third and replace it with an outward-facing V with sides the same length as the erased segment.  Repeat forever.)  At every iteration (see the first few in the drawing above), each line segment becomes 1/3 bigger.  Repeat forever, and the perimeter becomes infinitely long.  Surprisingly, the area doesn’t become infinite because the entire growing shape could be bounded by a fixed circle.  In the 2D equivalent of the Gabriel’s Horn paradox, you could fill in a Koch snowflake with a pencil, but all the pencils in the world couldn’t trace its outline.

Far older than these are any of Zeno’s paradoxes.  In one of these, fleet-footed Achilles gives a tortoise a 100-meter head start in a foot race.  Achilles is ten times faster, but by the time he reaches the 100-meter mark, the tortoise has gone 10 meters.  This isn’t a problem, and he crosses that next 10 meters.  But wait a minute—the tortoise has moved again.  Every time Achilles crosses the next distance segment, the tortoise has moved ahead.  He must cross an infinite series of distances.  Will he ever pass the tortoise?

The distance is the infinite sum 100 + 10 + 1 + 1/10 + ….  This sum is a little more than 111 meters, which means that Achilles will pass the tortoise and win the race.

Some infinite sums are finite (1 + 1/2 + 1/4 + 1/8 + … = 2).

And some are infinite (1 + 1/2 + 1/3 + 1/4 + … = ∞).

(And this post is getting a bit long.  Read Part 2.)

Photo credit: Wikipedia

Related posts:

Related articles:

  • “Zeno’s paradoxes,” Wikipedia.
  • “Zeno’s Advent Calendar,” xkcd.com.
  • “Paradoxes of infinity,” Wikipedia.
  • “Is God Actually Infinite?” Reasonable Faith blog.
  • Peter Lynds, “On a Finite Universe with no Beginning or End,” Cornell University Library, 2007.
  • Mark Vuletic, “Does Big Bang Cosmology Prove the Universe Had a Beginning?” Secular Web, 2000.
  • Wes Morriston, “Must the Past Have a Beginning?” Philo, 1999.
  • William Lane Craig, “The Existence of God and the Beginning of the Universe,” Truth Journal.

4 thoughts on “Infinity—Nothing to Trifle With

  1. I’m fond of Georg Cantor’s story of the Infinite Hotel — already full of an infinity of guests when the infinite bus pulls up with an equal number looking for a place to stay. “No problem!” says the manager, and moves Guest 1 to Room 2, Guest to to Room 4, Guest 3 to Room 6, … and presto! has an infinite number of odd-numbered rooms available for the newcomers.

  2. Pingback: Infinity—Nothing to Trifle With (2 of 2) | Galileo Unchained

  3. Pingback: Infinity—Nothing to Trifle With (2 of 2) | Cross Examined

  4. Pingback: Aristotle timline | Firstloveconsu

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