According to many witness statements, after a downfall of rain, the dark clouds broke and the sun appeared as an opaque, spinning disk in the sky. It was said to be significantly less bright than normal, and cast multicolored lights across the landscape, the shadows on the landscape, the people, and the surrounding clouds. The sun was then reported to have careened towards the earth in a zigzag pattern, frightening some of those present who thought it meant the end of the world. Some witnesses reported that their previously wet clothes became "suddenly and completely dry.
Estimates of the number of witnesses range from 30,000-40,000 by Avelino de Almeida, writing for the Portuguese newspaper O Século, to 100,000, estimated by Dr. Joseph Garrett, professor of natural sciences at the University of Coimbra, both of whom were present that day.
The miracle was attributed by believers to Our Lady of Fátima, an apparition of the Blessed Virgin Mary to three young shepherd children in 1917, as having been predicted by the three children on 13 July, 19 August, and 13 September 1917. The children reported that the Lady had promised them that she would on 13 October reveal her identity to them and provide a miracle "so that all may believe.
According to these reports, the miracle of the sun lasted approximately ten minutes. The three children also reported seeing a panorama of visions, including those of Jesus, the Blessed Virgin Mary, and of Saint Joseph blessing the people.
Some of the witness statements follow below. They are taken from John De Marchi's several books on the matter.
De Marchi claims that the prediction of an unspecified "miracle", the abrupt beginning and end of the alleged miracle of the sun, the varied religious backgrounds of the observers, the sheer numbers of people present, and the lack of any known scientific causative factor make a mass hallucination unlikely. That the activity of the sun was reported as visible by those up to 18 kilometers away, also precludes the theory of a collective hallucination or mass hysteria, according to De Marchi.
Pio Scatizzi, S.J. describes events of Fátima and concludes
The ... solar phenomena were not observed in any observatory. Impossible that they should escape notice of so many astronomers and indeed the other inhabitants of the hemisphere… there is no question of an astronomical or meteorological event phenomenon …Either all the observers in Fátima were collectively deceived and erred in their testimony, or we must suppose an extra-natural intervention.
Steuart Campbell, writing for the 1989 edition of Journal of Meteorology, postulated that a cloud of stratospheric dust changed the appearance of the sun on 13 October, making it easy to look at, and causing it to appear yellow, blue, and violet and to spin. In support of his hypothesis, Mr. Campbell reports that a blue and reddened sun was reported in China as documented in 1983.
Joe Nickell, a skeptic and investigator of paranormal phenomena, claims that the position of the phenomenon, as described by the various witnesses, is at the wrong azimuth and elevation to have been the sun. He suggests the cause may have been a sundog. Sometimes referred to as a parhelion or "mock sun", a sundog is a relatively common atmospheric optical phenomenon associated with the reflection/refraction of sunlight by the numerous small ice crystals that make up cirrus or cirrostratus clouds. A sundog is, however, a stationary phenomenon, and would not explain the reported appearance of the "dancing sun". Nickell suggests an explanation for this and other similar phenomena may lie in temporary retinal distortion, caused by staring at the intense light and/or by the effect of darting the eyes to and fro so as to avoid completely fixed gazing (thus combining image, afterimage and movement). Nickell concludes that there was
likely a combination of factors, including optical and meteorological phenomena (the sun being seen through thin clouds, causing it to appear as a silver disc; an alteration in the density of the passing clouds, so that the sun would alternatively brighten and dim, thus appearing to advance and recede; dust or moisture droplets in the atmosphere, imparting a variety of colors to sunlight; and/or other phenomena).
However, there are marked problems with the sundog theory because the meteorological conditions at the time of the Miracle of the Sun were not conducive to such an occurrence. Sundogs occur in the presence of cirrus clouds, which are made out of ice, not water droplets. A sundog could have occurred prior to the rainstorm but not trailing the rainstorm, which is when the phenomenon occurred. A sundog would have to have occurred, at very least, hours prior to the storm, since cirrus clouds can precede a rainstorm by a few hours. The short and brief rain experienced before the sun event, on the other hand, indicates cumulonimbus clouds.
Not everyone reported seeing the sun "dance, including the children, who reported seeing Jesus, the Virgin Mary, and Saint Joseph blessing the people. Some people only saw the radiant colors. Others saw nothing at all.
Paul Simons, in an article entitled "Weather Secrets of Miracle at Fátima", states that he believes it possible that some of the optical effects at Fatima may have been caused by a cloud of dust from the Sahara.
Kevin McClure claims that the crowd at Cova da Iria may have been expecting to see signs in the sun, as similar phenomena had been reported in the weeks leading up to the miracle. On this basis he believes that the crowd saw what it wanted to see. But it has been objected that McClure's account fails to explain similar reports of people miles away, who by their own testimony were not even thinking of the event at the time, or the sudden drying of people's sodden, rain-soaked clothes. Kevin McClure stated that he had never seen such a collection of contradictory accounts of a case in any of the research he had done in the previous ten years.
Leo Madigan believes that the various witness reports of a miracle are accurate, however he alleges inconsistency of witnesses, and suggests that astonishment, fear, exaltation and imagination must have played roles in both the observing and the retelling. Madigan likens the experiences to prayer, and considers that the spiritual nature of the phenomenon explains what he describes as the inconsistency of the witnesses.
Author Lisa Schwebel claims that the event was a supernatural extra-sensory phenomenon. Schwebel notes that the solar phenomenon reported at Fátima is not unique - there have been several reported cases of high pitched religious gatherings culminating in the sudden and mysterious appearance of lights in the sky.
It has been argued that the Fátima phenomenon and many UFO sights share a common cause, or even that the phenomenon was an alien craft.
Many years after the events in question, Stanley L. Jaki, a professor of physics at Seton Hall University, New Jersey, Benedictine priest and author of a number of books reconciling science and Catholicism, proposed a unique theory about the supposed miracle. Jaki believes that the event was natural and meteorological in nature, but that the fact the event occurred at the exact time predicted was a miracle.
The event was officially accepted as a miracle by the Roman Catholic Church on 13 October 1930. On 13 October 1951, papal legate Cardinal Tedeschini told the million gathered at Fátima that on 30 October, 31 October, 1 November, and 8 November 1950, Pope Pius XII himself witnessed the miracle of the sun from the Vatican gardens.