La liquefazione delle reliquie di sangue: una proposta di spiegazione

A miracle is an event which doesn't follow the known laws of nature so it is usually ascribed to God; many events reported in the Old and New Testament are regarded as miracles. Many rationalistic philosophers reject the concept of "miracle": David Hume upheld miracles break the laws of nature, therefore can't happen. Nevertheless this statement presume a full knowledge of nature "common course". Since we don't have such a knowledge, it looks more correct the Sant'Agostino's standby; he defined miracles as something contrary to "what we know about nature" not as "contrary to nature".

Unfortunately miracles are useless to add something on our knowledge of nature for are unique events which can't therefore be studied according to the rules of science.

But alongside "unique" or "unforeseeable" miracles (i.e. weeping statues, sudden health recovers etc.), there is one which happens regularly. In the San Gennaro's chapel (Naples cathedral) there are two hermetically sealed ampoules which are said, by tradition, to contain the Saint's blood.
This blood, which looks curdled, melts regularly. According to historical documents, San Gennaro (Bishop of Benevento) was beheaded in Pozzuoli in 386 A.D.; his body was taken in Naples catacombs, then to Benevento, after to Montevergine and, in the end, to Naples in 1497.
The first historically documented martyr's blood melting happened on Aug. 17 1389, when the relic was donated to the Roman Catholic Church by an anonymous. Since then, after nine centuries, meltings still happen regularly, without any seeming external intervention.
This event happen twice a year: Saturday preceding the first Sunday of May (San Gennaro's body transport from Pozzuoli to Naples anniversary) and Sept. 19 (martyrdom anniversary). Anyway the event hasn't such a regular recurrence: following a solemn procession, fervent prayers start in the Naples cathedral where it can take several hours or days for the blood to melt down. In this case people praying, at beginning, looks anxious and impatient to increasingly become exhorting.

Since many believers don't accept any explanation different from a miracle, let's try a step by step scientific method. First of all the ampoules holding the blood look like a "black box": something you can watch at, on which you can make some measurements but which is forbidden to open and verify what is inside.

IIf, for instance, we have a sealed glass box filled with straw and we see move the needle of a nearby compass, we could think the box contains a magnet, concealed by the straw; but, if we would notice the compass needle move only, but not always, when in the light, we should think the magnet inside is a very strange one…

Since 1820, thank to Dane physicist Hans Christian Oersted, it is well known that an electrical circuit with current produces an electrical field able to move a compass needle.
Modern scientists would figure out the box does not contain a magnet but an electrical circuit (solenoid) powered by a photoelectric cell. Light powers the cell (hidden by straw which doesn't block light) and makes the current flow in the circuit, thus creating the electrical field which moves the needle. But … all this happens only with sun light being the only one having the necessary frequency to trigger the phenomenon. It would be difficult make scientists believe the box contains a magnet with a strange behaviour even though they can't open the box to substantiate their theory; at the same time common people would be confused.
The "black box" we've talked about is something easy to make and reproduce and, consequently, not unique. So, if we would find some others, even the most ignorant in physics should agree the behaviour of the supposed magnet is not unique and will start thinking maybe there are other explanations. Well, even ampoules holding the miraculous blood are not unique for there are many other events of this kind:

• Santo Stefano's blood relic kept in the old Clarisse nunnery in piazza del Gesù;
• San Giovanni's and San Lorenzo's blood relic kept in San Gregorio Armeno's church;
• San Luigi Gonzaga's and San Pantaleone's kept in the Gesù Vecchio church. These relics melting, however, as well as that of other kept in private chapels, don't occur regularly.

These relics melting, however, as well as that of other relics kept in private chapels, don't occur regularly.

If we now consider the troubles these relics had to undergo before getting into the ampoules, together with the several hundreds of martyrs reported in history, it is very surprising there are just a few instead of tens.
Anyway, far from Naples, there are two more relics which melt regularly:

• San Pantaleone: blood is contained in a glass ampoule and, by tradition, melts every year on the 27th of July (day when the Saint was beheaded in Nicomedia - 325 A.C. - emperor Massimiliano reigning). The relic is kept in the chapel bearing the Saint's name in Ravello's cathedral (60 km. From Naples) and attracts all amalfitan Riviera residents; depending on how much time the blood takes to melt, and the degree of melting, peoples cast predictions for the year coming. Availables documents set the first melting in 1112 A.C..
• San Lorenzo: the blood, contained in a glass ampoule, melts every year on the 10th of Aug. (day of martyrdom which took place in Rome, year 258 A.C., emperor Valeriano reigning). According to tradition, a Roman soldier, witnessing the Saint's execution by grilling on blazing coal, picked some fat and blood drops up while the martyr was passing away and took them in Amaseno (100 km from Rome) where the relic is kept in the local church.
  Availables documents set first meltings after 1600 B.C.

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