People tend to believe what they want to believe. If they deny the possibility of life from other places than earth and the 3rd dimension, then things like aliens just don't register in the realm of possibilities.
From the research that I've done on the subject of crop circles, it seems to me there are two types: circles which have been done by humans, and ones which have been done by some form of alien.
There is footage on the internet of orbs of light which glide over a field and create the designs very quickly and perfectly.
The circles done by humans are easy to detect because they are sloppy, and are not very complicated.
Circles appear overnight. The ones which researchers say are done by aliens are intricate. The alien circles bend the fragile crop in the field to create their amazing designs. Once the plant grows a little it is easy to see that they were not harmed. In fact, crops which have been bent for the sake of alien circles grow better and stronger than the rest of the field which was not touched.
Circles created by humans consist of broken stalks of crops.
Circles created by aliens are sort of woven; some go this way and then the next level go that way. The size and complexity of the circles would be impossible to create by humans in such a short time. They are perfect in their geometry too.
The content differs also. With some of the alien circles, there are elements of physics. It is as if they are desperately trying to tell us something to help us. In some, the circles tell us of ways to create fuel by using water to get us into space. In others, the circle tells us that good still exists on earth and to hang in there.
In some, it shows what could be interpreted as an image of the hollow earth. If you don't know what the hollow earth idea is, it means that there are many beings living under the earth's crust several miles down and have been existing there for a very long time. Evidently there are aliens of various descriptions from different places living in peace there along with some humans.
Admiral Bird supposedly had one of his diaries disappear. This particular diary told of his discovery of an entry into the hollow earth where he found bipedal life. When he encountered beings within an opening into the hollow earth, he told his government about it and was asked to keep silent on the subject. His daughter also admits this.
Those who live underground have been in contact with some governments. They asked that we stop doing nuclear testing or nuclear wars because it affects their quality of life there.
They don't really want us to join them as we are far too ridiculous for their taste. We are warlike, prejudiced, you name it.
The "real" crop circles are communications of geometry. Sacred geometry.
Any one who understands physics would tell you that several of them are way more than mere pretty designs.
People often ask for a "sign". I'd say these are surely definite signs.
There have been at least 81 different aliens who have been visiting earth for a very long time and continue to do so. One group has made a deal with the government in the US to have a port to come and go from. They give us various technical data in exchange for abductions of humans for any purpose they wish, as well as animals. (like cows for example)
Our dna is very important to them. Also, they have impregnated women from all over the world with their "seed". When the Bible tells of the beings from the sky who came and impregnated pretty women from earth, it's not a fairy tale.
Check out ancient art. Paintings and cave drawings will reveal images of space beings, as well as ufo craft. We thought they were gods. We painted wings on them because they flew.
There are many different human groups who have been working on ruling the world for a long time. There are also certain alien groups who sometimes work with them for the same end, or aliens who work alone to take over this wonderful earth. Most of us are considered less than cattle to them, but there are a few aliens (and humans) who consider us beings of light who forgot our heritage once we descended into this 3rd dimension of duplicity. Those who love us try to guide us and encourage us, that as times "end"....we will ascend to the next dimension where we came from and we will rise above the nonsense of blood lust we experience here.
Aliens can travel through worm holes, or from one dimension to another. They can appear and disappear. Some don't manifest any more than an orb of light. This type would be a group of entities.
Our knowledge of fiber optics is one example of information which has come from aliens.
Darwin's theory has been blown out of the water on evolution when it comes to human intelligence. We could not have evolved to the point where we are today technologically in the span of time we've been here on earth. Something came to us and enlightened us and informed us. Something hurried us along.
Our universe is a bubble in the 9th dimension. Life is a great deal more complicated than we generally imagine. We can remain asleep if we wish. But let's not be surprised if suddenly the veil is lifted and reality intrudes. Crop circles? Why not? What other ways are we being communicated with?