Looking for intelligent alien life is hard not just for space’s size | Explained Premium

The Search for Extraterrestrial Intelligence (SETI) seeks to find life on other planets. Neutrinos, which interact weakly with matter, may be used to communicate with aliens. NU-SETI proposes setting up experiments to detect a non-uniform neutrino flux. METI, or Messaging Extraterrestrial Intelligence, is a programme to send messages to potential alien worlds. SETI/METI efforts need to consider language, content, and medium of transmission.

Some scientific adventures are as fascinating for the casual observer as they are for an engaged specialist. One such is the Search for Extraterrestrial Intelligence (SETI), driven by the premise that if there is life on another planet (especially in the form of intelligent beings), then it could have reached a level of technological advancement equal to ours or perhaps greater. And just as we have tried to find such life out there, these alien beings may be looking for us as well.

Across the vast distances of the cosmos, electromagnetic-wave signals are our best bet to identify ourselves and others. They range from radio signals concentrated in a narrow frequency range to pulsating wideband signals.

Researchers also need to have the proper means and techniques to differentiate naturally occurring waves, like radio noise from the magnetosphere of Jupiter or the environs of stars, from those transmitted from more interesting sources. Waves from space are also distorted en route to the earth and whatever information they carry may not survive the journey intact.

This is why scientists have also proposed looking for neutrino signals. Neutrinos are subatomic particles. After photons, the particles of light, they are the most abundant particles in the universe. They also interact very weakly with  matter, and can move relatively untouched through the same media within which electromagnetic waves would diffuse. Given these properties, it’s not far-fetched to assume that some extraterrestrial intelligence is also trying to communicate with us with neutrinos, in addition to radio waves.

There is another basis to this assumption. Scientists are still trying to understand some instances of radioactive decay that involve (i.e. are mediated by) neutrinos. Specifically, these instances of radioactive decay wouldn’t have happened unless they involved neutrinos from some source in outer space.

Mathematically, a radioactive decay obeys an exponential decay law. That is, the decay rate is proportional to the number of atoms there are. But in a 2017 experiment at Purdue University, scientists found that the decay rate of radioactive manganese declined sharply. They found that this could be explained if the rate was “responding to small changes” in the ambient flow of neutrinos.

Based on their experiment, the scientists proposed setting up such decay experiments at different sites around the world, and analyse the data collected for signs of a non-uniform neutrino flux – which could in turn be associated with events in outer space. They called their proposal NU-SETI, and wrote: