The density of air reduces as height is gained.
It is greater at a lower altitude.
The greater the altitude, the lower the air pressure.
Air pressure falls of as one gains altitude. At high altitude the air pressure is very low but it does not "falls drastically", which implies a sudden change.
Because of less gravity in high altitude
well the air pressure decreases as you go higher up and so does the temperature due to the warm air expanding and cooling. so yes high altitude affects you anywhere
High altitude gives you less air, therefore a bit less power
Pressure affects the density of air by increase of pressure increases the density
High altitude balls, during manufacture, are pressurized less so that, when opened at altitude, the balls are not too bouncy, as would be the case with normal tennis balls at altitude. I believe they are also manufactured to have approximately a 6% greater diameter. This greater cross-sectional area ,when traveling through thinner air (i.e., at altitude), should produce roughly similar flight characteristics as regular balls at sea level.
Exactly!
Jet streams
Jet streams
high altitude chambers