New tennis balls are considered fresh and not "flat". Old tennis balls exposed to play and air become flat and do not perform normally in a match.
The centers of tennis balls are rubber and rubber hardens with age.
In the early days of tennis, balls were often made of leather stuffed with hair or wool. The early tennis balls were made by Scottish craftsmen.
Old tennis balls have been used before, causing them to be worn in. New tennis balls have never been used before and easier to play with. It takes experience playing tennis to be able to tell the differences in old and new balls while playing. Otherwise, you can just tell by sight. New tennis balls are a very bright neon color and very firm, where old ones are darker in color and usually have less fuzz on them. Older tennis balls may also be slightly deflated.
A new tennis ball will bounce higher. Old tennis balls are considered "dead."
Give them to someone with a dog.
Tennis balls are very useful for more than just tennis. Old people put them on their walkers, and people throw them to their dogs. But tennis players use them for, well, tennis. I think the biggest market would be rackets and re-stringing them.
Before television was invented, tennis balls were white. They would have remained this way if television had not been broadcast on live TV This was because people couldn't see the white tennis balls flying across the screen. So, they were changed to neon green/yellow so that viewers could see them.
The polymeric materials in new tennis balls have a higher coefficient of restoration, so they tend to spring back into shape easier. With time and exposure to atmosphere, the compounds that keep the ball soft volatilize and leave into the atmosphere.
Tennis balls are geared for different court surfaces. There are tennis balls specifically designed for clay, hard court, and grass court surfaces. Check on the outside of the tennis ball can for the type of court surfaces you should use them on. For example, some tennis balls are specificially made for clay court surfaces. Some tennis balls work on hard court surfaces both indoors and outdoors. Check out your local sports store for many different brands. You also want to make sure that the balls you are playing with are "flat". Tennis balls lose their air pressure after you play with them. You can keep them in a special pressurized tennis ball can, but these are not used very much anymore. Make sure to open a new can of tennis balls when you hit the tennis course for a match. In fact, this a rule in tennis tournaments and leagues. You can squeeze the tennis ball to determine if it is flat. If you can easily squeeze it then it is most likely flat. Or you can bounce the ball to tell. Old tennis balls should be thrown away if they have lost most of their fuzz as well.
There is no way to answer this question, because most amateur players are not registered with any facility or team, so they would not be "counted", anywhere. Even if they were registered, not all clubs would reveal such numbers, in order to protect their members from potential privacy issues. The numbers of USTA and similar nationally recognized tennis associations around the world would tend to change from year to year, so that would not help, even if it were possible to track it down. One also cannot tell how by the number of tennis racquets and/or balls purchases, as many people own more than one racquet, buy more than one can of tennis balls, or share them with others, or continue to use old tennis balls.
there is no such thing as a type of ball python... but there are morphs of them.