Where do you look for E.T.? My paper on just that published in Acta Astronautica

 

Published in Acta Astronautica June 2025, open access till end July

Can there be any answer to that question that makes sense? We’ve been looking since the 1950s but ‘Space is big, really big…’ One answer is to consider from the problem that Schelling posed: “if you have to meet someone in New York City tomorrow but can’t communicate, what is your best option on where to go?” That’s a Schelling Point, one that both you and the person you hope to meet could mutually guess. (The most likely answer back in the ‘50s was the viewing deck of the Empire State building.

But in space? Now you have to consider whether you’re dealing with Apes, Angels or Men. Don’t write off the  Apes; they just need time to – bang the rocks together? – and then they’ll be as good as us and probably behave like us, so time is the only barrier. But we can write off Angels because they’re not here. Something may prevent species like ours ever becoming omnipresent and omnipotent in our own galaxy. So if we limit our search for ‘people like us’ who are limited to power sources we can pretty much scope out – fusion power and fusion drives – then the BIGNESS OF SPACE becomes the limiting factor, and this includes how far a transmitter can signal and be picked up by the sort of tech we can imagine.

It would help, wouldn’t it? to have a unique place that everyone knew about to go look for signals. The only location that has been proposed hitherto is the galactic centre. Unfortunately, it’s a very nasty place! In addition to the super-monstrous black hole SgrA*, there are (by x-ray observation) probably a million stellar-mass black holes flitting around it. Even a space captain of Luke Skywalker’s skill would need all his time and energy dodging problems, let alone set up a beacon. In the very long timescales for a beacon to be of any use, even stars aren’t safe as they can be ejected by the black hole. Need somewhere quieter. In the AMiTe Treffpunkt section of this blog, I proposed the AMiTe point mid-way between the Milky Way and Andromeda galaxies, a great place for chains of starships to thread through and exchange information, but way too far for a beacon to signal with any reasonable chance of refuelling. However, there was another point in that paper also defined by Local Group geometries, the ‘MiM’ (mid-Magellanic) point. At the suggestion of Mike Garrett, academic director of Jodrell Bank, I expanded that idea into a paper. I’m pleased to say that it was accepted for publication by the prestigious Acta Astronautica. Sadly, as I wasn’t funded for the work and ‘Open Access’ is very expensive if not backed up by an institution, it will only be available until end July for free, and then will go behind a pay wall (these guys have to make money too!). For now you can see it at:

https://authors.elsevier.com/a/1lFAPLWHGBKg- 

Picture credit: Elsevier, used with permission

To See Ourselves as Others See Us

 

The Mighty Mark 1 - a place of pilgrimage

On the day of named-storm Eunice in 2022, I managed to keep my appointment with MikeGarrett, Sir Bernard Lovell chair of Astrophysics at University of Manchester and Director of Jodrell Bank Centre for Astrophysics. Jodrell Bank, with its famous Mark 1 Telescope - made out of bits of battleships! - a name to conjure with. Many visits as a boy there; a place of pilgrimage during the Apollo program. Keeping just ahead of the storm on the M6, we were inside the Alan Turing Institute when it finally hit, and it was ‘knock-you-off-your-feet’ strong when we exited 2 hours later. It was great to meet a Radioastronomy and SETI group and to present the AMiTe idea. Lots of discussion, suggestions for references and encouragement to think further about observational consequences.

While Mike’s JBCA group of 190 people have wide ranging (multi light-year!) research interests including active galaxy nuclei and giant arrays (running  e-MERLIN, the UK's radio astronomy network), they are also active in the Search for Extraterrestrial Intelligence (SETI), and Mike is currently vice-chair of the IAAs SETI Permanent Committee.

So it’s quite fun to keep tabs on his publications. Here’s one that was publicised only in the last week: What would aliens learn if they observed the Earth? This claims to be the first proper study of the Earth’s Technosignature in 50 years and takes into account all modern human sources of radiation. We currently emit a whopping 4GW of radio noise, just from mobile phone transmission. The team has analysed databases of transmitters and considered the radiation pattern, and the potential for detection at nearby stars. These were limited to nearby systems, including Alpha Centauri, out to a maximum of 8 light-years. The conclusion:

“We worked out that an alien civilisation near these locations would, however, need much better telescopes than we have to detect the Earth’s mobile radio leakage. But that would be quite probable, given most technical civilisations are expected to be much more advanced than we are.”

It would be lovely to think that the closest stars have anciently wise civilisations, just waiting for the ‘youngsters’ (us, a mere 4.5bn years after the Earth cooled) to grow up and invent smartphones. Life may be ubiquitous (C’mon NASAPerseverance) but there again, it’s been a long, hard road here. And despite the best (breeding) efforts of Elon Musk, human numbers may start to decline as early as 2050. If the closest extant technical civilisation may be “outside theMilky Way and therefore forever inaccessible” (Brian Cox musing) then we’re going to need a pretty big ‘scope on the Cheshire Plain to detect that.

But maybe there would be a chance to detect ‘we’re here’ signals from an AMiTe point. I’m still to write up the next version of the paper with suggestions from meeting Mike, but there are some clues in the 'Brian Cox' post. Happy listening!

Picture credit: Unesco