We are not alone, or are we? This is a question that has divided many; while some believe there is little to no evidence to suggest there is extraterrestrial life, and objects like UFOs can be explained by optical illusion caused by temperature inversion, or crashed hot air balloons, others are convinced these explanations are nothing more than an elaborate cover-up to hide the truth.

There are many unexplained and mysterious things that exist on Earth, like the Nazca Lines, believed to be 2,000 years old, with images as big as 1,200 feet long. Or buildings created by ancient civilizations that show a technological and engineering advancement that came long after their time. There are also crop circles, geoglyphs in Ancient Egypt, exciting radio signals from space, and hundreds of testaments from individuals who believe they have either witnessed an unexplained object (this includes NASA's astronauts), or state they have had personal encounters with alien life-forms.

Below are objects and unexplained incidents that suggest there is something else out there, at least in the minds of the people who have witnessed them. Or at the very least, it's enough to spark theories as to why there is an area in the Nevada desert which has a blind spot on Google Earth.

20 The Nazca Lines Create So Many Unanswered Questions

Do unexplained lines in the Earth suggest that there is alien life? Perhaps not, but the Nazca Lines of Peru are much debated; how were they formed? Why were they formed? And who formed them? The lines comprise of a collection of giant motifs depicting animals, straight lines, and shapes, and are associated with the ancient Nazca civilization, History reports.

The geoglyphs are believed to be 2,000 years old and some of the pictorial representations are up to 1,200 feet long, while the straight lines can span across 30 miles.

19 An Ancient Civilization Was Able To Construct The Complex Sacsayhuamán

Sacsayhuamán is an ancient site in the Peruvian Andes, which according to National Geographic, some believe it is the work of not only an ancient civilization but also aliens. The location is more than a 1,000 years old, and the level of technology and engineering is surprising as the fortress contains rocks that are as heavy as 360 tons each, and they were carried from a distance of at least 20 miles.

Due to the precision of this masonry work, according to Ancient Code, even the Incas believed the site was created by an earlier people, descended from the skies.

18 Odd Craft Represented On Ancient Cave Paintings In Charama

Drawings from the past help researchers to better understand the people living in those times, but sometimes, they also baffle them, like the 10,000-year-old cave paintings from Charama, Chhattisgarh, which seem to depict an alien-like spaceship. According to Express, one archaeologist, JR Bhagat, spoke about the findings and suggested that it does seem prehistoric man may have seen extraterrestrial life forms, and the space crafts we associate with alien life in modern times seem to have been represented.

17 The SETI Project Received Strange Radio Signals

The existence of alien life is something that both terrifies and excites, and a piece of evidence could suggest an alternative life form is out there, is the radio signals from the Search for Extraterrestrial Intelligence (SETI) project. According to New Scientists, in 2004, astronomers searching for signs of extraterrestrial intelligence were surprised when they received signals from somewhere between the constellations Pisces and Aries, and while some believe it’s an attempt to make contact from aliens, others state it could be a natural phenomenon we have not seen before.

16 Crop Circles Still Remain A Mystery And Few Are As Complex As The Milk Hill Design

There is much debate about whether crop circles are man-made or the work of an alternative life form, and because they seem to happen overnight, it's not hard to see why the theories emerge. Among the many crop circles that have appeared, the one on Milk Hill in Wiltshire, England, is considered to be one of the most complex.

The pattern was discovered in 2001, and comprised of a series of 409 circles that formed a pattern known as a triskelion. According to Collective Evolution, the design is an impressive 780-foot pattern.

15 Many Question How Helicopter Hieroglyphs Came To Be On The  Temple Of Seti I

Why would the Ancient Egyptians carve helicopters and airplane imagery when these types of aircraft did not exist at this time? The hieroglyphs found on the temple of Seti I in Abydos are a mystery, and according to Outer Places, UFO enthusiast Steve Mera argues the depiction could suggest the people of this time had access to advanced technology through alien life forms.

However, other experts claim that the images are a result of original glyphs being drawn over, and thus creating the appearance of modern machines.

14 Buzz Aldrin Reported An Unexplained Moving Light On His Apollo 11 Voyage

Space travel has given us a wealth of knowledge, but perhaps the most interesting mission was that of the 1969 Apollo 11 flight, which saw man first walk on the moon. One of these astronauts was Buzz Aldrin, and he claimed when in space, he witnessed an unexplainable moving object.

According to The Telegraph, during a Reddit AMA, Aldrin wrote, “I observed a light out the window that appeared to be moving alongside us.” He went on to reveal there were many different explanations of what this could have been and did not immediately jump to the conclusion it was extraterrestrial, but simply, it was “unidentified.”

13 An Alien Mummy Turned Out Not To Be An Alien After All

We have long questioned whether aliens exist, and the jury is still out on this one. But there was an ancient mummy found in Peru's  Atacama Desert in 2003 that quickly made some people think this was the proof of aliens we'd all been waiting for. According to LiveScience, the mummy had an elongated head (resembling something similar to what we think of when we imagine grey aliens), but DNA evidence concluded the remains were human.

How did the skull become so elongated? There is a theory the skull could have become lengthened by childbirth, and after burial, it continued to extend because of the heat and pressure underground.

12 Oumuamua Has Caused A Debate About Whether It's A Space Rock Or Not

There is much debate about what Oumuamua is, but one thing we can all agree on is it’s an interstellar object and the first to be traveling through our Solar System. Some believe this object is space rock, others believe it's an alien spaceship because of the of the cigar-like shape.

The questions about what it is compelled astronomers from Western Australia to try and provide more scientific proof of what this object is, and according to LiveScience, they used the Murchison Widefield Array telescope to see if there were any signals to suggest alien life. The result? They stated, "We found no such signals with non-terrestrial origins."

11 A NASA Astronaut On Space Shuttle Atlantic Spotted Something

Earlier on this list, we mentioned during the Apollo 11 mission, astronaut Buzz Aldrin revealed he had seen an unidentified moving object, or rather a light source, alongside their spacecraft. But he has not been the only astronaut to hint at alien life, and according to Express, NASA astronaut Leland Melvin, who was onboard the Space Shuttle Atlantic claims he saw an object he cannot explain.

He stated it was “curved” and “organic” but that NASA dismissed it was extraterrestrial in nature and told him it was ice. Conspiracy and UFO enthusiasts theorists disagree.

10 The Washington Flap Was Explained Away

Another incident that got some people believing in extraterrestrial life making contact with Earth is the series of sightings took place in Washington DC, which Rebel Circus refers to as “The Washington Flap.” According to the publication, in 1952, a number of UFO sightings were made, including flying saucer-like objects appearing above the White House.

So, what could have caused these bright lights in the sky surrounding the official residence and workplace of the president of the United States? Rebel Circus claims it was explained away as “an optical illusion caused by a temperature inversion."

9 Teotihuacán Required Technology Far Superior To The Times

Another site from an ancient civilization worth noting is Teotihuacán, and according to National Geographic, this city in Mexico was built more than 2,000 years ago. But considering the size and complexity of this design, some feel it could not have been the work of human’s alone.

The city is believed to be have been created over centuries by a mixture of the Maya, Zapotec, and Mixtec peoples, but National Geographic notes many feel that at this time, these peoples were not yet “technologically developed” to match with the advanced structure.

8 Documentation Of Encounters Is Eerie -- And Plentiful

Perhaps the compelling argument suggesting alien life exists is not one object at all, but the multiple pieces of documentation? Although, none of it is scientific in nature.

According to New York Magazine, among the reasons to believe there is extraterrestrial life is the documentation has been gathered from many individuals who have stated they have had personal contact with extraterrestrials. The publication notes one UFO conference asked participants to document their experience with drawings, and although the accounts differ greatly, it seems these people truly believe what happened to them.

7 Seven Alien Earths Have Been Found And Researchers Believe They Could Support Life

In 2017, an interesting discovery was made; seven Earth-size alien planets which orbit TRAPPIST-1, a dwarf star that is 2,000 times dimmer than the sun. According to Space, scientists believe these planets, which are located 39 light-years from Earth, could have the right conditions to support life.

University of Cambridge’s Amaury Triaud, who is part of the research group, revealed that within the next few years there will be more information about these planets, and within ten years there would be evidence proving whether there is life.

6 Famous People Have Also Seen UFOs, Thus Adding Weight To The Encounters

There have been some famous UFO sightings like Roswell and Rendlesham Forest, but there are also people who have claimed to have had encounters -- as previously mentioned, there are even conferences for these people to gather. But these encounters are especially interesting when they happen to someone well known, like Mexican filmmaker Guillermo del Toro, who is responsible for films like Shape of Water and Pacific Rim.

According to New York Magazine, del Toro spotted a UFO in Guadalajara, and the publication states UFO Sightings Daily quoted him as saying, “It was so cr****. It was a flying saucer, so clichéd, with lights.”

5 The Mars Dunes

Humans are on the search for another planet which can accommodate life or any signs of it. Mars has been of specific interest, and researchers have revealed the planet’s ghost dunes could be evidence of alien life.

According to Fox News, research published in the Journal of Geophysical Research: Planets, reveals the ancient dunes have remained preserved, and within the dune, there could be microbial life protected from the surface radiation on Mars. Researchers believe these dunes could lead to the discovery of evidence of ancient life.

4 The Phoenix Lights Were Seen By Thousands Of People

An event known as the Phoenix lights took place in 1997; multiple people reported seeing unexplained and unidentified flying objects in the sky over the states of Arizona, Nevada, and the Mexican state of Sonora. According to Rebel Circus, there were so many individuals who witnessed this event, that 911 was inundated with calls.

The publication claims the lights flew in a “V” formation and it seems the mystery still remains unanswered. According to Ktar News, one witness said it couldn’t have been from Earth because the objects were too big and blocked out the stars.

The lights from the objects were explained as flares dropped by military aircraft in a training exercise, but many remain unconvinced.

3 Scientists Are Excited By The Prospect Of The Clouds On Venus

There is research to suggest the dunes on Mars are housing ancient alien life, but this is not the only planet to become the topic of research. According to Express, scientists believe aliens could also be living on Venus, or more specifically, atop the planet’s cooler clouds.

The reason scientists believe microbes may live in the clouds is that space probes noticed dark patches surrounding this area. The research has indicated more evidence needs to be done on Venus, and samples need to be tested on Earth.

2 The Findings Within The Mars Rock Have Been Disputed

There are fossilized microbes of alien life which fell to Earth in a meteorite, and were discovered in Antarctica in 1984, New Scientist reports. According to the publication, this rock was probably in the solar system for 15 million years before entering the Earth’s atmosphere, and it created excitement in the scientific community.

The publication notes NASA researchers saw signs of “nanobacteria” as well as organic molecules and very, very small quantities of mineral magnetite. The evidence has been disputed.

1 Astronaut And Sixth Man On The Moon, Edgar Mitchell, And His Testimony

It is always interesting when NASA astronauts comment about the possibility of extraterrestrial life forms, and Edgar Mitchell is one of these people. Mitchell served as the Lunar Module Pilot of Apollo 14 and was the sixth man on the moon.

He has also stated UFOs are real and according to Thought Co., Mitchell made this statement on Britain's Kerrang radio: "I happen to have been privileged enough to be in on the fact that we've been visited on this planet and the UFO phenomena are real.”

References: History, National Geographic, Ancient Code, Express, New Scientist, Collective Evolution, Outer Places, Ancient Code, The Telegraph, LiveScience, The Sun, Rebel Circus, Express, New York Magazine, Space, Fox News, Ktar News