Cosmological Distance Ladder and Cosmic Microwave Background Radiation

Greg Hill

Some say the universe is expanding at 73.2 +/- 1.3 kilometers/second/Megaparsec,
Some say it’s 67.6 +/- 0.3 kilometers/second/Megaparsec.
From what I’ve tested of a Cepheid variable,
I hold that 73.2 is infallible.
But if I had to measure twice,
I think I know enough of dark energy density,
To know that 67.6 is nice
And it is also my propensity,
To say that would suffice.

The Science

Mimicking the form of Robert Frost's poem ‘Fire and Ice,’ this poem examines the seemingly irreconcilable measurements of the Hubble constant, used to describe the expansion of the Universe. Galaxies appear generally to move away from each other at rates proportional to their distance, attributed to what scientists call dark energy. They use two methods to measure this. One uses Cepheid variables (stars with measurable luminosity and pulses used to measure distances) as part of a ‘cosmological distance ladder’ to determine the Hubble constant. Another is based on measurements of the cosmic microwave background. But the more precise those methods get, the more those methods do not agree, a problem known as Hubble tension. Even as we improve our ability to measure the rhythms of the Universe, our increased knowledge continues to expose deeper and more confounding questions whose answers elude us like distant galaxies receding beyond our reach.

The Poet

Greg Hill is a poet and Adjunct Professor of English in Connecticut, United States. His work has appeared in Six Sentences, Cargo Literary, Atlas and Alice, the Penteract Press anthology ‘Myth & Metamorphosis’, and elsewhere, and he has an MFA in Writing from Vermont College of Fine Arts. In the free time afforded to a father of three, he experiments with composing music for piano using cryptographic constraints. Twitter: @PrimeArepo. Website: gregjhill.com.

Next poem: Cycle by Alice Laciny