I'll talk about UFOs.

But first consider the following scenario.
You are in a forest with your friends, picking blueberries, you have been there about five minutes when you hear a loud rumbling/shattering noise, you look at your watch and see that the time is two minutes after two in the afternoon. You wonder if the sound is coming from an airplane that is taking off from some lake nearby and think no more about its source. You start picking berries again when you hear a kind of a double peep tone that seems to come from either behind you or is generated in such a way that it seems to be in the middle of your head.
Immediately after that, you seem to be in a surreal, kind of a dream world, you look up and there are two humanoids in front of you, you do not see their faces or any detail of their clothing, all you see is that they are humanoid figures. One of the humanoids requests that you move forward and lift your feet, you look down and see a small platform in front of you and you step on it.
The request is not a harsh command but a gentle request, you have no fear of the humanoids and you are unable to disobey their request.
As soon as you step on the platform it starts to move, the motion is very smooth and you seem to be part of the platform so that it is impossible to fall off. The sensation is as if you were floating in the air.
You travel with your friends and the humanoids up into what you believe to be a craft of some type that they used to arrive in. As you float upwards and into a rounded corridor, you figure that the humanoids are aliens and say welcome to Earth, then you start asking questions like where did they come from and what is their purpose for being here and other questions such as technical details of the propulsion system of the craft.
They remain quiet and you are taken to a room that seems like a sterile lab or a hospital room, where you and your friends are given a thorough physical examination.
After the examination they invite you to ask questions.
At this point the incredible things that surround you start causing apprehension in your psyche and you wonder if it is safe to be inside this ship, to this they answer that it is much safer inside the ship than on the outside and explain that the ship is shielded from all types of dangers, but outside you are constantly bombarded by various types of radiation that affect the body.
You want to know where they came from and they take you to the corridor that you came through.
On the opposite side of the examination room and beyond a railing there is a three dimensional display of stars, as you gaze at the stars while standing on the moving platform, you get a sensation of floating in space among the stars.
They ask you if you know where you are on the map. You try to distinguish the solar system and Earth from the display but the display is from such a perspective that you can not point to the planet Earth. You answer that you do not know, at which point they reply that they can not explain where they are from if you do not know where you are.
You accept their answer and ask how the craft is controlled. They take you to another much larger room where there is a large window showing the forest outside, you look through the window and see the forest and the sky but you also notice something like sparks or fireflies in the air, the humanoids seem interested in them. You quip that you have never seen fireflies in the day time and they explain that what you are observing is a result of radioactive elements in the atmosphere.

You look around the room and to your right there is a console that reminds you of a church organ, behind you there is a kind of a pillar that reaches from the floor to the ceiling.
You ask the humanoids about the method of propulsion of the craft and they ask you what you think about it.
You explain that it must be very different from the space ships used by Earth people because this craft can fly through space as well as the atmosphere and can land in places that only a helicopter might be able to land.
Then you realize that the only way such a feat could be accomplished is if the atmosphere that surrounds the ship can be controlled somehow. You imagine that there is a machine in the craft that can remove the atmosphere from the top side of the craft and then is able to place it on the underside, such a density difference of the surrounding atmosphere then would lift the craft vertically like a helicopter.
The humanoids do not explain their system, but they assure you that you will figure out the operation.
Then they say that it is time for them to leave and you will be taken back to the forest. While you are going down a ramp towards the ground, you become aware of a communication between the two humanoids; one says to the other, this one seems different, at that moment you see the beings clearly, your eyes focus on the eyes of the humanoids and the pupils of their eyes are very large and dark, it reminds you of a very large cat that is about to bounce on its prey, and you seem to be the prey. The hair on the back of your neck stands on end and you are filled with terror.

Then you find yourself picking blueberries and wonder why you are somewhat tired, there is only few blueberries in your basket so you should not be tired yet.
You glance at your watch and see that almost two hours have gone by since you checked your watch last. You compare your berry collections with that of others and chide yourself for being such a poor berry picker.

Imagination is a wonderful thing, and quite often it leads to new developments or even breakthroughs in technology.

For instance the above story gives you three big ideas that could be developed into commercial products.

!) The platform could be powered by air pressure and controlled by computer chips, it would be very useful for moving heavy objects or give mobility to people with disabilities.

2) How about developing a holographic display and detection system that is able to display not only the scenery as it looks to the eyes, but also is able to convert phenomenon such as nuclear decay events into visual effects.

3) My favorite is the idea of constructing an airplane that has no wings and has the ability to take off vertically, accelerate and fly out of the atmosphere into space and back, then is able to decelerate, fly and land anywhere like a helicopter.

I am certain that the number one could be constructed without too much trouble, it might not be as smooth in operation as the one in the story but it would certainly work.

Number two is not within our immediate ability to construct, at least I do not know of any method that would achieve such a display system, but that does not mean that such a system can not be constructed someday.

Number three is within the feasibility of today's technology. At least in my opinion. Certainly, it would need a lot of research and development in the areas of magnetohydrodynamics, plasma physics, fluid dynamics, and aerodynamics, besides the thorough understanding of gas laws and the behavior of the atmospheric gasses at various temperatures, densities, and velocities.
I believe that the basic mechanisms already exist to make such a craft, all that is needed is further development of the existing equipment.

Why has no one built such a machine? Maybe no one thinks that it is possible, or perhaps they do not have enough knowledge to understand the operating principle or other requirements of the structure. Perhaps they are afraid of building something totally different from existing devices.
Or perhaps the financing and labor is impossible to get.
On the other hand, some of the unidentified flying objects may already be such craft.

What do you think?

Johannes