This is the most useful infomration I've read in ages and I feel it will make me more popular by far. Hooray for NewScientist!
Sparklers appear to draw lines in the air because of the phenomenon known as visual persistence. The human eye does not react instantly when its view changes, but keeps the old image around for a few milliseconds. This is what enables us to perceive films or television images as moving pictures when they are in fact a sequence of still images. The persistence of the eye causes each image to merge into its successor, creating the illusion of movement.
If the changing image contains very bright objects against a dark background - such as a sparkler at night - the persistence lasts longer, so the light from quite a long period of time can be added together to appear as a single streak.
There are numerous gadgets that exploit this effect by using strips of fast-moving LEDs to apparently create writing in the air. Persistence can also be seen in the coloured spots left in your vision after a camera's flash has gone off.
The sparks from the sparkler are produced by burning flecks of a metal such as magnesium or aluminium flung off from the from the firework. Initially only their outer layer of metal burns, but after the fleck has burnt down to a critical size the core becomes so hot that it explodes. The sub-flecks from the explosion then burn out quickly and brightly in a distinctive star.
I am going to make the assumption that every single person who reads this blog like the scene in microscosmose when the snails had sex the best. Which is great because i have even MORE information on snail sex for you from NewScientist:
Apparently, male snails fire "love darts" into females before mating. They don't know exctly why, but they think it's because snails are promiscious and the dart coudl stop females from producing enzymes to kill sperm.
I am confused though because I thought snails were hermaphordites.
Article is as follows:
'Love darts' double snail's chance of offspring
Love's arrow may have helped Cupid's match-making, but it was never slathered in mucous. Yet to double their chances of paternity, some male snails fire slimy darts at their would-be female mates.
“Snails that hit their partners with a dart are able to father more babies,” explains Ronald Chase of McGill University in Montreal.
The so-called love darts are wielded by a number of molluscs, including the brown garden snail (Cantareus aspersus) where it sits on the right side of its body, adjacent to a mucus-producing gland.
A male snail passes approximately 5.5 million sperm to its partner in a single mating, Chase says. But he adds that only about 1400 sperm of these millions survive the attacks of enzymes, which digest the sperm within the female. Furthermore, snails mate promiscuously, so one sperm donation does not ensure fatherhood.
Hacked off
Chase and colleague Katrina Blanchard set up an experiment to test the idea that pricking a mate with a dart raises a male's chances of siring offspring. This involved 38 female brown garden snails, each paired with two male partners that had each had their darts surgically removed – the darts take a week to grow back.
Before mating with one partner, the female was injected with inert salty water, and before mating with the other an injection of the mucus associated with snail love-darts.
The researchers used genetic analysis to reveal that males who mated shortly after the mucus injection were twice as likely to sire offspring as those who mated following the saline injection. This was true regardless of the order of injections or mating.
Chase and Blanchard found the mucus appears to cause certain ducts in the females to contract, and they think this could stop the delivery of the enzymes that digest the sperm. But the substance within the mucus that does this remains a mystery.