Rare, all-red auroras are produced by high-altitude oxygen, at heights of up to 200 miles. Nitrogen produces blue or purplish-red aurora. The connection between the Northern Lights and sunspot activity has been suspected since about 1880.
In developed countries, the average birth weight of a full-term newborn is approximately 3.4 kg (71â2 lb), and is typically in the range of 2.7â4.6 kg (6.0â10.1 lb).
The optimal size for a newborn is around 4,000 grams, or roughly 8.8 pounds, according to Dr. Kramer. The average baby in the study was found to be smaller than optimal. In 1990, the average birth weight was 3,441 grams, and in 2005 it fell to 3,389 grams, according to the study.