According to the popular extraterrestrial hypothesis, UFOs are ’somebody else’s spacecraft’. The earth is allegedly being visited by beings from other solar systems who are carrying out a survey of our planet and its inhabitants. Various objections have been raised to this hypothesis .
The possibility that there are numerous intelligent civilizations in our galaxy is now widely accepted. The SETI project is trying to detect their presence by analyzing radio signals from space. Some scientists, however, argue that alien civilizations must be very rare or even nonexistent because if they were as numerous as commonly believed, the earth should have been visited by several of them by now; these scientists dismiss the idea that UFOs are extraterrestrial spacecraft.
Those who believe that aliens are already here are often asked why the visitors don’t land on the White House lawn. One possible answer is that they have got more sense! Others argue that there is no need to as the aliens have already struck a secret deal with the authorities! A more common argument is that the aliens are obeying a ’prime directive’ not to interfere in earth affairs — though this is clearly contradicted by the enormous impact the UFO phenomenon has had on human society over the past 50 years, if not the past several millennia.
There could conceivably be obstacles preventing humanlike lifeforms from surviving a journey through interstellar or intergalactic space, but none are known at present. It has, however, been argued that UFOs cannot come from another solar system because the enormous distances involved are prohibitive. However, even with our present technology it is possible to travel to another star, though it would take numerous generations.
Moreover, some alien civilizations could have developed technologies far in advance of those on earth. And although standard relativity theory forbids faster-than-light travel, reality may not. Just as sound waves cannot propel an object to supersonic speeds, so electromagnetic forces cannot accelerate objects to superluminal speeds. What gravity control may yet achieve, remains to be seen.
Another objection to the ET hypothesis is that it is highly improbable that intelligent lifeforms on other planets would be humanoid in appearance and display human emotions. Others disagree and argue that since the basic human form is highly functional and efficient, it could be fairly common in the universe. *
According to theosophy, every mature sun has a family of planets, and kingdoms corresponding to those on earth will evolve on every planet, though at any one time only one kingdom is dominant on each of the 12 globes (located on 7 different cosmic planes) making up a complete ’planetary chain’. The ’human’ kingdoms on the 7 ’sacred planets of our own solar system (i.e. those most closely related to earth) are said to approximate our own form to some extent .
It is also speculated that extraterrestrials may have played a role in genetically engineering the human race, or that they have genetically modified themselves in order to make themselves more humanlike — though given their rather ’alien’ appearances, the attempt does not seem to have been a complete success!
A stronger objection is that it is unlikely that intelligent beings from other planets would be adapted to our own gravity or able to breathe our own atmosphere.