Depending on the area seen in an individual picture, brown, yellow and green continents can be seen or parts of Earth can be covered by white clouds. Earth is by far the most dynamic planet when seen from space.
Oxygen therapy is a medical treatment. It must be prescribed by a doctor. For people with COPD, oxygen therapy can be a helpful part of their treatment plan. The prescription your doctor writes will include: If you need oxygen for rest, exercise and/or sleep, and how much in liters per minute (lpm) for each activity.
According to Dr. Fred Furgang in his article Hypoxia, Oxygen, and Pulse Oximetry, a pilot should use supplemental oxygen if the oximeter reading is below 90%, maintain at 91-92% level when doing remedial tasks and above 93% with increased workload.