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The Stars, Like LeavesWeek of June 21, 1999NOTE: (June 23, 1999) I found out that the estimate I made in this Snack is off, which changes the numbers but not the idea behind the topic. I've added a bit more about it at the end of the page below.
I said in
A week before the wedding mentioned last week, my wife and I were
driving back home from Kansas. We were in West Virginia, a
beautiful area with relatively tall mountains covered by green
trees. I had been driving a long time (it's about 2000 kilometers
from Kansas to my home) and was in the passenger seat slowly
drifting off to sleep. From my vantage point, slumped in the
chair, I saw a green blur of unidentifiable trees, passing me
at about 100 kilometers an hour.
Although I may have been sliding down the path to Morpheus' arms,
the question was not an idle one. We don't really know how many
stars there are in our Galaxy, though we estimate there are
perhaps as many as 400 billion (that's a 4 followed by 11 zeroes).
I have a personal research project looking into finding dim red stars,
stars that are extraordinarily difficult to detect because they
are so faint. These stars may give us a handle on the way the
Milky Way behaves; its structure, density and perhaps even
how it formed. There may be billions of stars like the ones for
which I am searching, stars that have never been seen before.
If each one were a leaf, well, that sounds like a lot of leaves!
My brain leapt ahead. Guess that there are 1000 leaves per tree,
and I can see about ten trees straight back as I look out the window
and up the mountainside. That's 10,000 leaves at once. When I
pass 100 rows, that's a million leaves. If they're, say, five meters
apart I'll pass a million leaves in, um, let's see, about 20 seconds or so
(I was tired and being very rough with my numbers). So in one minute
I'll pass 3 million leaves.
That's quite a few!
But hold on. Three million leaves a minute
is 180 million an hour. But there are 400 billion stars in the
Galaxy. I'd have to wait over 2000 hours to pass that many leaves.
That's about three months! Yegads, three months at 100
kilometers an hour! It takes three days of nonstop driving to cross
the United States, but it takes thirty times as long to see as many leaves
as stars in the Galaxy. The Milky Way is huge!
I woke up pretty fast at that point, heart racing. Literally, I was
shaken awake by that little bit of personal epiphany. Space
is big, and we really aren't. It's pretty daunting sometimes
to think about how much more we have to learn.
Most people are lucky to have such an epiphany once in their lives; I've had
two. The first occurred many years ago, again while falling asleep. I
had a sudden visceral realization of just how much energy is produced
by the Sun, as if I were floating over the surface, soaked by the countless
photons produced by that furnace, and was jolted awake as solidly and
effectively as if someone had slapped me across the face.
I love astronomy. It provides a sense of perspective, and tells
us a lot about our real place in the cosmos. It has a far better
and more realistic affect on us than any manmade contrivance.
So the next time you're out driving, watching the scenery go by, imagine
that you're actually traveling through space. You'll never
complain about how long it takes to get where you're going again!
Oops! (June 23, 1999) After I received an email
from my old friend Dan
Durda I've had to rethink these numbers. He claimed 1000 leaves per
tree is way too low. He even called a plant biology researcher
at Cornell University to confirm it! Dan is a dedicated if somewhat wacky
friend. Anyway, I too called
Dr. Karl Niklas at Cornell, and he said that some trees can have upwards
of a million leaves on them, but it's not uncommon for larger leafed trees
to have much fewer. Sycamore leaves are indeed quite big (the tree where
I grew up commonly had leaves 20 or more centimeters across), and Dr.
Niklas agreed that an estimate of 1000 is probably too low, and 10000
is probably better (I'll say here that Dr. Niklas is not responsible for
any errors I make here, including the estimate I'm using!). So instead
of 90 days to pass as many leaves as stars in the Milky Way, it may only
take 9. And it would be fewer if you look at, say, mature oak trees. Then
you'd only need to pass a few hundred thousand trees. Still, that's a
long time. The numbers are impressive: there are more stars in
our Galaxy than we can name, let alone even see.
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