Space.
There's a lot of it.
And we eagerly reach into the unknown to search for answers to profound problems.
Are we alone?
Are we the most advanced of us?
We are we the way we are?
We know that intelligent civilisations exist.
Because we exist.
And so the search for deeper meaning continues.
But how?
Finding signs of other civilisations in our galaxy is not a simple matter. The tools we use are limited by our technological capabilities, and so we can only search for signals that approximate to our own.
Like finding another cup on the end of the string attached to our own.
This is the gist of our Search for Extraterrestrial Intelligence (SETI): filtering the galaxy for comms similar to ours like radio wavelengths called technosignatures.
"One of the great advantages of the search for technosignatures at radio wavelengths is that we are sensitive to signals emitted from thousands of light-years away. And it does not take that much power," astronomer Jean-Luc Margot of the University of California Los Angeles.
"For instance, our search can detect the Arecibo Planetary Radar at distances of over 400 light-years. And it can detect a transmitter that is only 1,000 times more powerful than Arecibo - a trivial improvement for an advanced civilisation - all the way to the centre of the galaxy. The volume of the galaxy that can be sampled with a radio search for technosignatures is immense."
Margot and company searched for technosignatures in 2018 and 2019 using West Virginia's robust Green Bank Telescope.
The result of just four hours of observation?
A total of 31 stars resembling our Sun and a whopping 26,631,913 technosignatures were found.
So did we discover aliens playing old-timey be-bop on their 2-way radio?
Not exactly.
Every technosignature was coming from Earth.
Remember "The Dish" and the microwave?
In 2015, the long-standing 17-year-old mystery of "suspicious perytons" (short radio signals) interfering with the Parkes Radio Telescope was solved.
The source?
A microwave oven in the Parkes break room used for heating up employee lunches.
Funny, but radio-frequency interference (RFI) is a cause for concern.
Similar to the microwave and the dish interference, our own signals are muddying the metaphorical waters on a galactic scale.
"RFI could potentially obscure an extraterrestrial signal," Margot said.
"RFI makes our job more difficult because we detect tens of millions of signals per hour of telescope time, and we need to make a determination about every single signal: is it anthropogenic or is it extraterrestrial? It would be a lot easier if we detected only a few signals. Fortunately, our algorithms allow us to automatically classify over 99.8 percent of the signals."
How are they fixing it?
The data processing pipeline has been tweaked with refined sensitivity and signal detection rate. Plus a new filter is automatically classifying RFI in the collected data. This rules them out before they pile onto the already large pool of data.
Even though the filters are flagging 99.84% of signals as RFI - a lot less data to process - the remaining 1.6% equates to 43,020 signals.
Are these aliens yet?
Nope.
About 90% of the 43,020 signals were known RFI. Leaving just 4,539 signals as "promising" alien technosignatures.
As the team manually worked through the remaining technosignatures one-by-one, they soon found all were Earth based as well.
"If a signal is detected in multiple directions on the sky, we can be extremely confident that it's anthropogenic," Margot said. "An extraterrestrial signal from an emitter at interstellar distances would be detected in only one direction."
While a kick in the guts, the result is expected.
A search of over 10 million stars turned up 0 signs of alien technosignatures early this year.
Even so, it's not all bad.
Margot and the UCLA use SETI data to train the next generation of students.
"We conduct the search as part of a SETI course that I have taught at UCLA annually since 2016. This course appears to be unique in the US and perhaps worldwide," he said.
"Students collect terabytes of data from known or suspected planetary systems, write a data-processing pipeline collaboratively, search for technosignatures in the data, and publish the results. It is most satisfying to witness the students acquire important skills .. all in the context of this important search."
The revised method also revealed some issues with quantifying older data. The new method shows previous estimates of how many potential civilisations are transmitting signals in the Milky Way.
They're too low by a factor of 15.
How?
They "... fail to detect some of the signals that they are designed to detect," Margot said.
"We implemented a signal injection and recovery analysis tool that allows us to quantify the efficiency of data-processing pipelines. This efficiency must be taken into account when attempting to place bounds on the number of transmitting civilisations."
Further limitations in our SETI endeavours are being recognised and revised.
Such as, when two intersecting signals are detected, the algorithm only acknowledges the one with the highest signal-to-noise ratio. Missing the other entirely.
When a faint signal exists in a wash of background noise, they're most often missed too.
And these areas of high signal density must be attuned carefully.
Advancing the measures needed to overcome these limitations is difficult, time-consuming work that is worth the effort.
RFI is an issue for every radio astronomer on Earth.
So much so that entire methods and measurements are being made obsolete because of the interference.
Some measurements can't be detected between the Parkes telescope and Sydney.
It's that bad.
This ties in with NASA's near-future venture to the moon and building a radio telescope there as the moon is a natural buffer against Earth-based RFI.
This amplifies SETI data processing.
And we can be more efficiently powering through the real candidates for technosignatures, not our microwave lunches.
"The search may answer one of the most profound scientific questions of our time: Are we alone?" Margot said.
"All life on Earth is related to a common ancestor, and the discovery of other forms of life will revolutionise our understanding of living systems. On a more philosophical level, it will transform our perception of humanity's place in the cosmos."
Do you think we're close to an E.T. moment? Let us know in comments and share with a friend to spread ARSE.
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