Debaters learn that in order to be able to defend any hypothesis, you must also learn to defend the counter-party. This way you can predict which counterarguments will be launched at you. The best known phrase for it comes from Chinese strategist Sun Tzu, who famously said: if you know yourself and you know your enemy, you will win every battle.
With this in mind, a group of scientists from Queens University Belfast in the UK and the Max Planck Institute for Solar System Research in Germany have been looking at which planets are ideally situated to study…. Earth.
Instead of looking for aliens, where would the aliens be looking for us in other words.
And the findings are surprising to say the least. Of all the planets in our solar system, it would appear that Mercury, Venus, Earth, and Mars are actually more likely to be spotted than the more distant Jovian planets Jupiter, Saturn, Uranus, and Neptune, which are in fact much larger in size.
Robert Wells, a PhD student at Queens University Belfast said, "Larger planets would naturally block out more light as they pass in front of their star. However, the more important factor is actually how close the planet is to its parent star - since the terrestrial planets are much closer to the Sun than the gas giants, they'll be more likely to be seen in transit."
Looking for distant worlds where alien civilisations would have the best chance of spotting any part of our solar system, the research team looked for parts of the sky from which more than one planet could be seen crossing the sun.
In doing so, they concluded that at most three planets could be observed from any point outside our solar system.
One of the team’s scientists, Miss Katja Poppenhaeger from Queens University Belfast. said that: "We estimate that a randomly positioned observer would have roughly a 1 in 40 chance of observing at least one planet. The probability of detecting at least two planets would be about ten times lower, and to detect three would be a further ten times smaller than this."
The journal Monthly Notices of the Royal Astronomical Society published the study.