Scientists speculate that life exists on other planets in the universe. Yet, the probability of ever making contact is extremely low for the German physicist and former astronaut Ulrich Walter.
"Yes, there are beings out there, but we will never meet them. We will never communicate with them. But they must exist," says Walter to ZDF, who celebrated his 70th birthday on Friday.
"Logic demands it, given the almost infinite number of other planets." However, these are in other galaxies, which humanity will never be able to travel to. "In fact, it can be shown that we will never pick up messages from them, even if they send some."
Photo: Wiki Commons - Ulrich Walter as a Astronaut in 1993
Extraterrestrial Life in the Milky Way Unlikely
In our Milky Way - according to Walter, the "accessible part" of the universe to us - the likelihood of extraterrestrial life or other civilizations is very low.
Travel to them is even more out of the question. Such voyages would take more than 10,000 years - even if it's just a few light-years away.
"The Basis for Biological Life Is Everywhere"
Water, carbon, and energy are essential for life not just on Earth, but also in the universe. "The basis for biological life is everywhere. The improbability first lies in such a planet needing to receive exactly the right amount of energy from another sun-like star."
A second critical point is the emergence of the first cell from inanimate matter. Other forms of life are hard to imagine. This involves the chemistry of information carriers like DNA.
Complex silicon compounds, however, do not have the necessary stability - and the most important metabolic product is solid, insoluble silicon dioxide in comparison to gaseous, highly soluble carbon dioxide.
"Silicon cannot store this amount of information and it does not have the right chemical environment." he says to the German tv channel.
What Do Extraterrestrial Beings Look Like?
Walter leaves open what the "little green men" might actually look like.
They would need an intake and output for their essential metabolism, just like us. Biology offers a wide variety of carbon-chemistry-based variations. "And these exist everywhere in space."
