Why are we terrified of the Grays?, page 1

Great question. Even if the whole notion of 'ET', 'Grey Aliens' and ET-piloted UFOs is a myth, this classic figure does seem to have a visceral hold over the human psyche. Skeptics and believers alike seem to have this reaction

Before continuing, just keep in mind that despite your 'memory', or 'feelings' of being "dragged up to the roof", this most assuredly does not mean you were actually abducted by non-terrestrial beings.

Let's look at the most logical explanations. But before we do, we should assign a probability of 'unusual' or 'out-lying' explanations. In all fairness, I think there is no way to assign a probability of -zero-.

As part of the estimation, I think we have to consider:
1. Perception of a being that is non-standard does not automatically prove that it is from a distant planet. It could be
an inter-dimensional being,
o a being from the future;
o a virtual being with some tangible aspects;
o a non-tangible perception from the mind that is projected onto 3-D
space;
o temporal lobe epilepsy; or
o other - something we have not yet discovered.

We know that several situations can produce feelings of not being alone, and beings of unusual characteristics.
o electrical stimulation of the brain;
o sleep paralysis can cause perceptions of beings;
o 'fantasy-prone' individuals can form such a belief that a completely internal or subjective experience appears to be external and objective.

So in descending order we'd have to say:
1. Terrestrial phenomenon, mis-identified as an other worldly event;
2. External brain stimulation;
3. Internal brain stimulation;
4. Fantasy Event;
5. Outlier event
a. Future humans;
b. Inter-dimensional beings;
c. Non-terrestrial beings.

The reason we would put 'future humans' above dimensional or non-terrestrial beings is that, even though it may be impossible or unlikely to travel in time, at least we -know- that technology exists and that humans exist (and they desire to find ways to time travel).

In the case of alien beings from another planet, we don't know they exist, we are unsure of their ability to
o get into space,
o travel in their neighborhood,
o travel outside their neighborhood,
o be able to come to our planet, and
o be able to find us in the vastness of the M-W galaxy.

What are the barriers to coming here?
o Vast distances;
o Technological challenges;
o Motivation and opportunity;
o Need for an organized civilization to produce technology;
o Longevity of civilizations;
o Fiscal challenge of funding such a trip;
o Extreme cold and isolation of space;
o Radiation;
o Hard vacuum;
o micro-gravity;
o need of the civilization to establish self-replicating worlds locally to prevent catastrophic extinction events;
o need of the civilization to establish remote self-replicating worlds to prevent extinction by GRB (Gamma Ray Bursts)

What are the indications that ET is here:
Stories, some trace evidence, some radar confirmed UFO sightings (which we have never see positively linked to an actual ET flying them.)
Though we've heard stories of crashed aliens or flying aliens, all stories with reported recovered aliens do not have proof that they were flying in any craft (the craft was on the ground), nor that such beings were definitely proved to come from another world (as opposed to the above, including human hoaxings, including military or other organizations hoaxing the phenomena for their own purposes).

So I think you can get an idea about the scope.

(next) why are we afraid.

Again, the probabilities are not zero, though we can't really pick a number.