According to the findings of mainstream science, aliens have never visited the earth. Despite the whimsical fantasies of fictional works and the confusion of supposed eye-witnesses, there is no credible scientific evidence that aliens have ever visited the earth. Aliens did not visit the earth anciently and build the pyramids, nor do they sneak onto our planet in our day. Because of the unreliability of the human eyes and human brain, scientific data is established through (1) quantification, (2) use of accurate tools, and (3) repetition.

Quantification means that instead of a human giving a subjective account, the human – or better yet, a machine – measures a number to determine a property. For instance, “it feels hot outside” is a subjective statement of little scientific value. Is it hot enough to melt chocolate? Is it hot enough to melt steel? Does it just feel hot to the person making the statement because she just started menopause? We don’t know from this statement. A quantified statement such as “it is 90 degrees Fahrenheit outside” is more reliable, and therefore scientific. Next, the use of accurate tools means that a proven measurement tool is used to make the measurement instead of the human’s eyes. For instance, a builder who needs to measure a stud so he can cut the drywall to fit it does not just look at the stud and guess its length. He uses a tape measure to get an accurate value for the length. Lastly, repetition ensures that freak errors in measurement are identified and discarded. Builders know that they have to measure twice if they only want to cut once. Repetition also allows a value to be measured several times and averaged so as to minimize noise. Repetition means that one person takes the measurement several times, but it also means that other people make the measurement. Measurements repeated by different people minimize the error effects of a single faulty tool or confused human. If a builder uses a tape measure that has the numbers printed wrong, he may consistently get the same measurement, but it will still be wrong. Repetition by others will minimize such errors.

In every area of life, and not just in the lab, data is not reliable unless is has been quantified, measured by an accurate tool, and repeated. The alleged eye-witness accounts of UFO’s and alien visitations fail to be reliable data on all accounts. When a man tells a newspaper that he saw a bright light over his farm that looked like it had an alien face inside, he has provided no quantified information, he has used no tools to make his measurement, and he is unable to repeat or have others repeat the measurement. Three strikes against him means that such accounts are completely unreliable. If an alleged UFO witness actually went up to his awe-inspiring blob of light and tried to measure its width, temperature, etc. he would quickly find that reflections from clouds were playing tricks on his eyes or that fireflies were migrating. According to current reliable data, aliens have never visited earth, contacted earth, or even given any hint of their existence. These facts do not automatically rule out the existence of life on other planets. They just indicate that their influence has not yet reached earth.

Most alien accounts involve seeing something strange in the sky or a strange creature on the earth. The following objects, events, and experiences could be easily misunderstood to be aliens by unreliable human eyes:

Natural Objects

Fireflies firefly-forest-3
Barn owls barn_owl_close
Meteorites falling-meteorite-captured-on-dash-cameras-in-russia-video-55229-7

Electrical Disturbances

Corona discharge elmo
Cloud to ground lightning 48680-lightning_and_thunder_audio___multimedia_other
Cloud to cloud lightning Eric-Bartley
Elves, Sprites, & Blue Jets Sprite_from_ISS_(cropped)
Ionospheric air glow airglow_strip

Atmospheric Optical Effects

Aurorae green-aurora-rosing_1417_600x450
Clouds ufo_1241830c
Mirages mirage6
Rainbows rainbow_elam_1
Fogbows glories_tudorica_big
Sun dogs IMG_0047
Moon dogs k-bigpic
Light pillars pillars_tape
Circumhorizontal halos 3_fire rainbow
Searchlights promotional-searchlights-space-coast-music-festival
Laser guides VLT_Laser_Guide_Star
Earthquake lights earth quake light

Man-Made Craft

Airplanes YB49-2_300
Helicopters comache1
Hot-air balloons tumblr_mgkropZW0Y1qa944oo1_1280
Weather balloons ufo2
Dirigibles dirigible
Kites mega-alien-kite-10m-long2
Flares 250px-US_Army_52253_Best_Warrior_At_Night
Military drones 120220_57343-111010-futuretech-drone-915a.streams_desktop_large
Satellites 800px-Iridium_satellite
Rockets 38321750001_2131126341001_launch440
Man-made spacecraft STS-107_reentry
Frisbees 835455201_97c23516cc_z

Psychological Effects

Hallucinations caused by alcohol or drugs
Hallucinations caused by various medical diseases
Hallucinations caused by an abnormal fear response
Hoaxes and pranks carried out by other humans