The growing discussion around UFOs (now called Unidentified Aerial Phenomenon or UAPs) ramped up this past week.
Claims suggest US officials, and others around the world, have been in a pseudo arms-race, collecting parts and reverse engineering them.
However, no evidence as of yet has been presented.
Regardless of the claims, the question at heart is: if life exists, and it is intelligent, how likely is it to travel to Earth?
Firstly, no scientific evidence has ever been put forth, found, or concluded that points to life existing on another planet other than Earth.
However, there is a huge amount of work, particularly in our solar system, looking for signs of life - mostly bacteria or simple organisms.
The general consensus is that it is likely that it has existed at some point on Mars, and/or moons of Jupiter and Saturn.
There is also a general consensus that intelligent life does not exist in our solar system, else we would have found it by now.
Yes, we have looked on the far (dark) side of the moon.
If intelligent life is not from our solar system, then it must be from another star system. We estimate there are about 300 billion stars in our Milky Way galaxy.
Nearly all of the stars likely have at least one planet, and most have multiple planets - meaning trillions of planets may exist in our own Milky Way.
However, only a small fraction of these are believed to be Earth-like planets and capable of supporting life. Still, this numbers in the tens of billions.
This is also not even counting the moons, which in our solar system, are some of the best places.
Alpha Centauri is the nearest star system to our own. In the night sky, if you look towards the Southern Cross, there are two bright stars, called the pointers. The bottom, brighter one is Alpha Centauri, which is actually three stars orbiting around each other. Proxima Centauri, one of these stars and currently the closest star to Earth, potentially has three stars, and Alpha Centauri A potentially one as well.
The system is 4.2 light years away, meaning the light from the star you see tonight left sometime in March 2019. Currently, our fastest satellites, using a number of techniques, would take thousands of years to get there.
New technology like using lasers and light sails, hopes to get that to a few decades. Even if we could travel at the speed of light, it would take four years just to get to Earth from that star system. One, we think is unlikely to host intelligent life, if life at all.
Therefore, the star system aliens would come from is at least hundreds of light years away, more likely thousands to tens of thousands of light years. Travelling at the speed of light, that is a dedicate trip.
Many scientists think life is likely to exist. I even think intelligent life exists or has existed somewhere, at some point. However, the distances involved mean they must have a very dedicated reason for coming here to spends hundreds to thousands of years for the trip (keeping in mind we Canberrans often complain about driving to Sydney).
Alternatively, they can travel much faster than the speed of light, and our knowledge of the universe would completely change. Or they are not visiting.
- Brad E. Tucker is an Astrophysics and Cosmologist at Mt Stromlo Observatory and the National Centre for the Public Awareness of Science at the ANU.
