Why do ink pens start leaking at high altitudes?

Why do people living at higher altitudes have higher lung capacity and more red blood corpuscles?

Why do diamonds sparkle?

Why does nose start bleeding on high mountains?

When the ink fountain pen leaks on high altitude :

Why do people suffer from altitude sickness after reaching the high altitude regions ? How does their body acclimatized after a couple of days ?

A kind of similarity found in polar regions and high altitude is

The " mountain sickness" in persons climbing to high altitudes with any aid of oxygen cylinders is due to

Why does ice melt slowly at higher altitudes?

The density of water at 4^0C is supposed to be 1000 kg m^(-3) . It is same at the sea level and at a high altitude?

Why do tribes who live in high altitude of Himalayas experience discomfort in respiration? How do they get adapted to survive in such a situation?