The Black Knight Satellite, according to those who believe the conspiracy theories, is an artificial satellite that has been orbiting Earth for over 13,000 years, watching from above, sending our signals back at us, and occasionally sending cryptic messages to Nikola Tesla.

Nikola Tesla and the signal

One of the main pieces of evidence for the Black Knight Satellite that conspiracy theorists point to (other than the photograph, which we'll get to later) is a strange signal received by none other than Nikola Tesla in 1899.

Tesla had been given $100,000 by Jacob Astor – who later died aboard the Titanic – to create a new lighting system, which Nikola naturally blew on creating experiments at his Colorado Springs laboratory. During one of these experiments, he recorded a signal that he believed to be artificial in nature, and from an intelligent species not of this Earth.

"I felt as though I were present at the birth of a new knowledge or the revelation of a great truth," he wrote of the signal in 1901. "Even now, at times, I can vividly recall the incident, and see my apparatus as though it were actually before me. My first observations positively terrified me, as there was present in them something mysterious, not to say supernatural, and I was alone in my laboratory at night."

"It was some time afterward when the thought flashed upon my mind that the disturbances I had observed might be due to an intelligent control. Although I could not decipher their meaning, it was impossible for me to think of them as having been entirely accidental. The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another."

Look, Tesla, as well as being a genius, was a strange guy. Sure, he invented a lot of really cool things, but you've got to take any proclamations from a man who claimed to be in love with a pigeon in the way "a man loves a woman" and that the pigeon loved him back with at least a little pinch of salt. In the same article, he suggested that intelligent beings could be dwelling within the Moon, to give you an idea of the understanding of other worlds.

While the Black Knight theorists believe the signal was sent by the satellite, Tesla believed it to be from Mars. While it's not possible to know for certain what he observed, it's possible the signal came from either a lot further than Tesla thought, or a lot closer than Black Knight conspiracy theorists will accept. Theories suggest he could have observed a signal emitted by a far away celestial object – such as a pulsar (he would have to be very lucky to do so, especially given the equipment he was working with) and the radiation of Jupiter (much more likely, according to a study that attempted to look at what the equipment he was using could detect).

Or, as is sometimes the case, it could just have been of Earthly origin. Hey, even the best of us occasionally are baffled by signals that came from a canteen microwave.

Sure, the signal could also have come from a satellite that has been orbiting the Earth for thousands of years, but that is an extraordinary claim which requires extraordinary evidence. It's also not clear why you would jump to this conclusion, given that it can be explained without resorting to "there's an alien ship just above us that we haven't spotted all this time".

Long delayed echos

In the film Contact, aliens first alert humanity to the fact that they have received our transmissions by sending transmissions of Adolf Hitler giving a speech, as (according to the film, which took some dramatic license for a cool scene) it was one of the first high-frequency broadcasts that could make it through the ionosphere. 

Black Knight conspiracy theorists believe that the "satellite" has been doing something similar, sending back our own signals at us as "long delayed echoes".

In 1927, engineer Jørgen Hals also picked up a strange signal. Or, to be more precise, a normal signal, repeated in a strange manner.

"I repeatedly heard signals from the Dutch short-wave transmitter station PCJJ (Eindhoven)," he wrote to professor Carl Størmer at the University of Oslo.

"At the same time as I heard the telegraph-signals I also heard echoes. I heard the usual echo, which goes round the earth with an interval of about 1/7 second, as well as a weaker echo about 3 seconds after the principal signal had gone. When the principal signal was especially strong, I suppose that the amplitude for the last echo 3 seconds after lay between 1/10 and 1/20 of the principal signal in strength. From where this echo comes I cannot say for the present. I will only herewith confirm that I really heard this echo."

The echoes, despite prompting many investigations, are still not explained today. There are several likely natural explanations, however, ranging from the signal traveling several times around the world (eerie audio here) to signals being reflected by distant plasma clouds.

Again, there is no evidence to suggest it was reflected by a satellite in the Earth's atmosphere, nor an explanation for why conspiracy theorists would leap to this conclusion first.

The Black Knight Satellite photographs

In a piece of evidence that goes somewhat against the "NASA are covering everything up" portion of the Black Knight Satellite theory, there are several photographs that are publicly available on the NASA website which show the alleged UFO. Or, to be pedantic, FO, as the photographs have already been identified.

First, take a look. Cool, aren't they?

Well, sorry to burst the bubble, but the photographs are of a bit of debris that NASA had dropped. Specifically, a thermal blanket, which NASA reported as having gone missing (along with a few other bits and pieces) before the photos were incorporated into the conspiracy theory.

Is the Black Knight Satellite real?

No.

Or at least, it's incredibly unlikely that it is real, and there is no evidence for it that holds up to scrutiny. The "evidence" for the theory, as with many conspiracy theories, is an array of unconnected events brought together to create a fun narrative. There are some branches to the story that show how truly absurd it is, such as that the Illuminati shot down the satellite in 2017, and that astronaut Gordon Cooper saw the satellite while aboard the Mercury 9 spacecraft (he didn't, he strongly denies it and NASA transcripts show no such event).

As fun as it is to believe, what we're essentially looking at here is a cool first look at a signal from space, an unexplained echo, and a blanket.