but they are many concrete evidence of photos,some dated back to the early 20th century which photoshop haven't exist yet,but pranks using models or solid objects is possible.what are them,who are them.where they are from.no1 will know unless a alien came out of nowhere 1 day and explains itself

ah the famous roswell incident and the mysterious and top secret area 51.but the latter seems to be jz some rumours and made up stories

http://en.wikipedia.org/wiki/Area_51

Thanks m8

@Icy
And the other thing is, you can try put an apple inside the pyramid and the other one at a refrigerator. Within a month, you can see the result
Apple inside the pyramid is still fresh and you can eat it right away.

NB : about the apple thing, i was told by the pyramid guide when i was having my trip there
Thanks
Rcode

If there is Alien or UFO visiting earth, under current physics science law, the faster moving speed is light speed, but we haven't discover any planet within several thousand light year away except the solar system.

So either Alien can travel in light speed and they have very long life, or can travel beyond light speed (which dismiss Einstein's theory). So in order to have Alien or UFO, we needs to have either one of it, so that they can reach here.

I am not saying there is no alien existing or other living in the universe, as universe is so big, so we think it is impossibe, only earth got life, right?
But those could be thoousand light year or even more away, which by any means there is no chance to reach under curreny physics law.

The universe is so big, we can't even get out the solar system, not the mention the milky way galaxy which our solar system is a tiny peanut within, while there are many many others galaxy as well.

Who define their shape and looks? Who like our imagination.. I hav doubt on the shape and looks part.. arent there other life form that those always shown.. Always the little green martian look.. Y they jus wanna observe us? Y dont they make contact? Y their flying craft is always saucer type? R we just being visited by 1 type of alien? Y us?

Another theory to chew on:
If they (alien) were to create a device to observe us, why create something that looks so different from earth creature? Logically, they should create a device or probe which look exactly like human, so they can hide among us. If not, try other earthly creature, that should blend easily.

There are few theories why they look so differently:
1. The 'thing' we saw is indeed themselves
2. The 'thing' we saw is a fail probe, the success probe is already among us. 
3. Alien 'vision' is different than us, they see differently, and hence saw a different version of us. They might be seeing a different realm/dimension (different thing), but created the device in our realm/dimension.