The recent passing away of Stephen Hawking has rekindled interest in one of his theories about extra-terrestrial life, based on the insight about tiny particles in the first few seconds of creation of the universe following the Big Bang, about 13.5 billion years ago. These strange sub-atomic constituents are capable of being present at many places simultaneously (as per Quantum Physics). The fusion of these particles at the then temperatures of billions of degrees is believed to have produced different elements present on the earth and other planets.
The presence of these particles at many places, at the same moment of creation, can be responsible for the simultaneous birth of more universes and points to the probability of existence of living systems elsewhere as well. These life-forms may have some similarity with ours because of the commonality of these weird particles of matter. Already, the data from Kepler Space Telescope shows that more than 2000 planets exist outside our solar system. Also, the solar systems of some stars have earth–like habitable planets about 12 light years from us. A light year is the distance a ray of light (with speed of 186,000 miles per second) would travel in one year.
An orbiting telescope, much more advanced than Kepler’s has been launched recently to explore the presence of more earth-like planets in the solar systems of nearby stars. This has been named Transiting Exoplanet Survey Satellite (TESS). Another advanced Observatory, James Webb Space Telescope (JWST), is scheduled for launch in future.
For existence of life outside earth, liquid water besides carbon, nitrogen, hydrogen, sulfur and sources of energy are needed. Search for Extra Terrestrial Intelligence (SETI), started when Francis Drake suggested that, in addition, there are some other conditions too, though most of them have not been met yet. But the search continues.
The rate of formation of sun-like stars and the fraction of such stars with life-friendly planetary systems is one such condition. The living systems there must have evolving intelligence technology to emit electro-magnetic signals over sufficiently long periods of time so that we can detect them. Several probes have been sent in the past to Mars, Saturn and Jupiter (and their moons) with sophisticated transmitter-receivers and also instruments to study their soils and atmospheres.
Mariner orbiters show that water once flowed on Mars. Caves (having toxic gases) similar to earth are seen on this planet. Hubble’s Space Telescopes showed that there are cracks in the Europa, the Jupiter’s moon, in which icy water is present, as in earth’s cold Arctic region. Europa probably has a huge ocean of water below its icy surface and has many elements on its sea floor. Life existed in the past on Mars and Jupiter in microbial forms. Similar views are held about Saturn where jets of water have been seen erupting on its moon.
TESS (2018) and JWST (2020) may give definite clues to the existence of life outside earth, on planets within our known universe. We may also learn of life on planets in other universes where the requirements similar to those on earth are available. It is a continuing journey from science fiction of Carl Sagan to the realization of the dream of human settlement on other planets as envisioned by Stephen Hawking.