Horn of a dilemma needs close attention
I WAS very concerned to learn recently that one of astronomy’s iconic instruments is at risk: the horn-shaped radio antenna in the US that provided one of the strongest pieces of evidence of the Big Bang, which astronomers have determined took place about 13.8 billion years ago.
The site on which the antenna is located is slated for development, and there is fear that it could be moved, causing damage, or even destroyed.
The historical importance of this instrument, known as the “Holmdel Horn” because of its location on Crawford Hill in the town of Holmdel, New Jersey, cannot be overstressed.
Built by Bell Labs as a communications antenna, it was used to make one of the most significant scientific discoveries of all time: the Cosmic Microwave Background Radiation.
Two astronomers, Arno Penzias and Robert Wilson, were using the antenna for astronomy in May 1964 when they first noticed some unexpected background radio noise in their receiver.
Their efforts to remove the noise included taping the seams in the antenna with aluminium tape and even removing pigeon droppings (and the pigeons) from the horn, but the “unwanted” signal remained.
For the scientific background to what they found, I’ll briefly take you back to the 1910s, when US astronomer Vesto Slipher was working at the Flagstaff Observatory in Arizona.
He made measurements on many “fuzzy” objects – which were later found by Edwin Hubble to be galaxies full of stars, separate from our own Milky Way galaxy – and discovered that most of them were receding from us.
He did this by examining the spectra of their light: looking at the shift in wavelength of the light, caused by their motion relative to us.
These observations were just the beginning. In the 1920s, Edwin Hubble and Georges Lemaitre noted that the galaxies that were receding faster were the more distant ones. This led to the famous relationship between velocity away from us and distance from us, which is now known as the Hubble-Lemaitre Law. It is a cornerstone of cosmology, and especially the concept of the expanding universe. It led to the idea that the universe began in a very hot and very dense condition, suddenly expanding from a point in the event that is well known as the “Big Bang”.
Having begun so small and hot, the universe has expanded so much that it has cooled considerably. In fact, it has cooled so much that its overall temperature is just 2.7 Kelvins – that is, just 2.7C above what scientists call absolute zero, which is minus 273.16C.
It is known that everything with a temperature above absolute zero emits radiation, peaking at a particular wavelength. It turned out that was exactly what Penzias and Wilson had found: the “Cosmic Background Radiation”, which is the remnant of the Big Bang, 13.8 billion years after the great expansion (and cooling) began.
It was a major episode in the history of science, and to this day it is a very strong piece of evidence for the Big Bang to have taken place.
Penzias and Wilson won the Nobel Prize for their discovery. Wilson said in 2014: “The importance of this discovery really only became clear over time.”
However, the finding was so significant that it was more or less the “death knell” for a rival theory about the universe, called the Steady State Theory.
That idea suggested that the universe had always existed and that matter filled the gaps as the space expanded.
Now, the Holmdel Horn sits unused and in far from perfect condition, but it is not unloved. It simply can’t be allowed to be damaged or destroyed.
I will be following the news about the Holmdel Horn very closely. I rarely sign petitions, but I have done so in this case.
If you would like to join me, the URL, whose name conveys the important message in itself, is https://actionnetwork.org/petitions/savebig-bang-antenna