Will, thanks for that.

I can imagine the presents of a ALIEN (SpaceCraft), could create panic, but
why is our Militairy Defence developing strategies and weapons to state,
human-kind is not going to wait and sit down, if an invasion of ALIENs and their SpaceCraft(s) would/could cause/pose a threat.

If 'they' are able to be in the universe for a long time, they must have some kind of protection against radiation (from the universe or stars), some sort of shield.
This would make this SpaceCraft a difficult object to approach or attack.

They also would have be ahead of our technology and probably withstand
virusses, bacteria, etc., so 'partly humanoïd' and machine (Cyborg)

This would make us an easy target, if they have other then friendly, reasons
for visiting this planet.

They've come up with some bizar stuff, large holes, a few 100 or more meters
deep filled with water, a Nuclear Device on the bottom, top is sealed to build up presure.
When ignited, all the energy most Gamma Rays would make steam of the water, in a few milliseconds and shoot it in space, the seal could really do
some serious damage, if it's made of a solid and heavy material.

If you create a Nucleair Explosion in space, it would render little effect,
1-- No Shock-Wave, c.q. presure wave.
2-- No heat build up.
3-- Only radiation, which imposes no threat to 'them'. (Shield)
4-- The E.M.P. created, would only cause problems for ourselfs.(If the Earths
magnetic field, doesn't shield us, enough!).

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I would think that if there are any UFO's they would more likely be unmanned robotic drones. If we have been visited then it was most likey many thousands of years ago, and not currently.

Probably true and if 'they' found a way to make 'copies' or some sort of reproduction,
I hope they'll try again, so we can get a chance to see or notice ' them '.

If they've visited, this earth before, it could be shocking, seeing the 10 fold, or more increase of inhabitants and the changes made, compaired to (a) thousand(s) years ago!
Making it unlikely, visiting earth again, or with different intentions!
We changed and we changed the earth, why should 'someone' want to visit this planet, unless it's their only option, or need some recourses still available, like H2O.

But this is all speculation, we are trying to explore our 'own' galaxy and 'universe' or multiverse, as more and more ideas come to mind, we will succeed, or being wiped out.
Our geatest 'enemy' is still our incapabillity to fight bacteria and virusses, successfully.
Seeing, our latest discoveries are hardly a hundred years old, we also have a long way
to go. Let alone, travelling through space, at more then the speed off light.
(Not possible, according to our earthly science, or way of thinking.)

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No advanced aliens have recently visited Earth, We would be able to hear them on their own planet. We have been looking and listening for 50 years and have found nothing.

If they came here on a 1000 year journey with a big Mother ship that housed all of the flying saucers and other craft we would have been able to detect them in orbit.

It may not be true that we can detect them from here. The radio signals may be too weak to get here with any real strength. The signals may not be on the frequencies we monitor. They could be coming from a part of the sky we haven't observed yet. There could have been signals before we even existed. There may be life now, but they aren't using primitive radio signals. There are so many possibilities.

Absolutely correct. It is much easier to debunk the possible existence and presence of UFO's rather than it is to debunk Seti@home!

If you are a minister, you are not supposed to be in here.

Perhaps I was a little too mean. Sorry about that.