New Delhi: Don't miss the full blue moon tonight! Though Friday's moon will not actually be blue, but the term "blue moon" is used when two full moons occur in a single calendar month.
This month the first blue moon occured on Aug 1 and the second one occurs tonight.
In the first half of the 20th century,the blue moon apparently referred to the third full moon of a season — spring, summer, winter or fall, that boasted four full moons instead of the usual three.
But that definition was misinterpreted over the years, and today we call the second full moon in a single month a "blue moon."
The phrase "once in a blue moon" suggests that the celestial phenomenon is exceedingly rare, but that's not the case.
Blue moons come along once every 2.7 years on average, and sometimes much more frequently.
In 1999, for example, blue moons occurred in both January and March (with no full moon in February).
The moon reaches its full phase at 1928 IST (1358 GMT) Friday, marking the second full moon of August.
Stargazers won't be able to see two full moons in a single month again until July 2015.
Friday's full moon won't actually be blue, unless a load of dust or ash in the atmosphere lends it that particular hue from your vantage point.
Blue moons aren't named for their color, and they look like any other full moon in the sky most of the time.
Rather, the term has always been associated with an "extra" full moon. Blue moons exist because our calendar months aren't perfectly synched up with lunar months.
It takes 29.5 days for the moon to orbit Earth, during which time we see the satellite go through all of its phases. But all calendar months (except February) have 30 or 31 days, so occasionally two full moons get squeezed into a single month.
Like this August. Or this September, if you live in the Kamchatka region of the Russian Far East or New Zealand. In those locales, Friday's full moon actually occurs after midnight on Saturday (Sept. 1), making the following full moon — which comes along Sept. 30 — the blue one.
The legend of the full moon's effects on human behavior has existed for centuries, popularized by the myth of the werewolf.
The words “lunacy” and “lunatic” are derived from the same Latin root that gives us the word “lunar,” as people often attributed intermittent insanity to the phases of the moon.
While many people believe the full moon influences behavior, scientific studies have found very little evidence supporting the “Lunar Effect.”
In 1978, University of Miami psychologist Arnold Lieber wrote the book The Lunar Effect: Biological Tides and Human Emotions.
He argued that the moon influences day-to-day behavior and concluded that homicides increased during the full moon after analyzing Miami's crime records.
Similar crime studies during that same time period, however, found no such relationship.
Then, in 1986, researchers from the University of Saskatchewan in Canada combined the results of about 100 studies and found “no causal relationship between lunar phenomena and human behavior.”
They discovered statistical flaws in many of the papers that claimed to find such a link. They even reanalyzed Lieber's homicide data and found no correlation.
More recently, numerous studies have been conducted by intrigued researchers, with most attempts to blame the moon for everything from suicides to vomiting after surgery coming up empty.
So with all this evidence to the contrary, what makes the full moon lunacy theory still so popular?
Perhaps it's the media, who know people are more likely to read a crime story if some police officer blames it on the moon.
Or maybe people just want to hold onto an urban legend that's been around for hundreds of years.
A more scientific answer may be selective memory. If some bizarre murder or car accident occurs, people are probably more likely to remember it if it happened during the night of a full moon.
There is no scientific evidence to prove that drivers turn nearly lunatic on full moons.
The lunar effect is the theory that there is correlation between specific stages of the Earth's lunar cycle and deviant behavior in human beings that cannot simply be explained by variation in light levels.
There is no good reason to expect this to be the case, and in spite of numerous studies, no significant lunar effect on human behaviour has been established. Scholars debunking the effect sometimes refer to it as the Transylvanian hypothesis or the Transylvanian effect to emphasise its fanciful nature.
Examples of the belief have been found in ancient Assyrian/Babylonian writing. The term lunatic itself was derived in Latin from the word luna, meaning "moon"
It is widely believed that the moon has a relationship with fertility due to the corresponding human menstrual cycle, which averages 28 days.
However, no connection between lunar rhythms and menstrual onset has been conclusively shown to exist, and the similarity in length between the two cycles is most likely coincidental.
It is sometimes claimed that surgeons used to refuse to operate on the full moon because of the increased risk of death of the patient through blood loss.
In October 2009, British politician David Tredinnick asserted that during a full moon "surgeons will not operate because blood clotting is not effective and the police have to put more people on the street.".
A spokesman for the Royal College of Surgeons said they would "laugh their heads off" at the suggestion they could not operate at the full moon.
Some studies seem to offer limited support for lunar effects, but most fail to show any relationship between the phase of the moon and abnormal behaviour, and meta-analyses have revealed that apparently significant results are likely to be statistical anomalies rather than indicative of a real effect.
In general, apparent positive findings have tended to be inconclusive, contradicted by other studies, or shown to be the result of statistical errors.
Two other studies found evidence that those with mental disorders generally exhibit periods of increased violent or aggressive episodes during the full moon, but a more recent study found no such correlation.
A study into epilepsy found a significant negative correlation between the mean number of seizures and the fraction of the moon illuminated by the sun, but this correlation disappeared when the local clarity of the night sky was controlled for, suggesting that it was the brightness of the night that influenced the occurrence of epileptic seizures.
A reported correlation between moon phase and the number of homicides in Dade County was found, through later analysis, not to be supported by the data and to have been the result of inappropriate and misleading statistical procedures.
A fifteen month study in Jacksonville, Florida revealed no lunar effect on crime or hospital room admittance.
A meta-analysis of thirty-seven studies that examined relationships between the moon's four phases and human behavior revealed no significant correlation.
The authors found that, of twenty-three studies that had claimed to show correlation, nearly half contained at least one statistical error.
Similarly, in a review of twenty studies examining correlations between Moon phase and suicides, most of the twenty studies found no correlation, and the ones that did report positive results were inconsistent with each other.