Constantly Inconstant
In the summer of 1993, I was invited to take part in a
fellowship at the Harvard University Center for Astrophysics. Besides several all-expenses paid weeks in Massachusetts
and some killer field trips, it was a chance to study and write curriculum
about the concept of time. For that
golden summer I had the chance to work with some of the country’s best theoretical
physicists and astronomers. It was a
feast for the mind. It also means that
when I see articles about astrophysics, I grab the popcorn and settle in like I’m
watching a Bette Davis movie.
Recently, there
has been a “crossover” hit in astrophysics.
That is, information that starts and usually stays in the scientific
journals has become popular in broad circulation media. Usually this happens when there is a catchy
or thought provoking topic, paradigm shifting concepts being presented, or visuals
that work for everybody. It turns out
that a certain inconstancy of the Hubble Constant fits all three
categories. I will pause while you reach
for your popcorn.
Here is the
thing. In
1929, American astronomer, Edwin Hubble, observed a shift in the spectrum of
light (toward the lower-frequency, red end of the spectrum) coming from objects
measured from Earth. This “red” shift indicated
that these objects were moving away from us.
You can experience the same phenomenon when you close your eyes and
listen to the sound of a car coming toward you, and then as it passes and moves
away from you. Sound waves and light
waves behave the same way. Waves coming
toward you are shortened, creating higher frequencies and sounding higher in
pitch. The same object moving away from
you will have its waves stretched out, lengthened and have a lower pitch. When you hear “weeeyooooouuu” think red
shift.
Hubble
found that this red shift was occurring—well—everywhere he looked. No matter where he pointed his telescope the
universe was moving away from us. And
the farther away the object was the faster it was moving. The universe seems to be getting constantly
bigger. Voila! The Hubble Constant (Ho), one of
the most important numbers in cosmology.
With this number we can estimate the size and age of the universe from
the primordial "Big Bang."
Of
course, Hubble still needed a yardstick.
For that he needed the help of a good woman. Henrietta Swan Leavitt, of
Harvard College Observatory, discovered that the intrinsically brighter variable
stars (the Cepheids) have longer periods. This insight — Leavitt’s law — allows
astronomers to know the Cepheid’s absolute luminosity, then gauge the distance
to the star based on how bright or faint it appears. With this knowledge the scientific community
thought it had a good bead on the size and scope of the universe.
But
now, some recent observations have caused a certain unease in the inviolable understanding
of the Hubble Constant. The universe, is
seems, is not looking the way it should.
We have
used the Constant to calculate that 5% of the universe is composed of physical
matter, that which the sun, this Earth, and all the life on it, are made
of. Another 25% is dark matter, which
emits no radiation and is known only from the way its gravity affects the
motion and configuration of galaxies. The rest is dark energy, the driving
factor in the acceleration of cosmic expansion.
Why is all of this moving away from everything else? Why does space itself seem to be
expanding? Why do the sections of the
sky that once seemed to be empty are now filled with more and more and more
galaxies? Why do better instruments show
more “stuff.” The numbers of the constant
do not add up.
I don’t know,
but I will tell you what I first thought.
What if what we are seeing is a time signature? What if time, our 4th dimension,
leaves a blip on the radar. We know that
galaxies bend time, Einstein proved that.
What if some of these sightings are really reiterations of a galactic
mass here, there and beyond? What if the
music of the spheres has an echo?
Think hard
and keep the faith.
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