Black holes, quasars and active galaxies. Black holes are objects so dense, and with so much mass, that even light cannot escape their gravity. The existence of black holes has been theorised for more than 200 years. It is impossible to observe them directly, and astronomers had no way to test their theories until Hubble arrived.
Sequence IIIG Test Method. Sequence IIIG testing for automotive engine oils. The Sequence IIIG Test is a fired-engine, dynamometer lubricant test for evaluating automotive engine oils for certain high-temperature performance characteristics, including oil thickening, varnish deposition, oil consumption, and engine wear.
In this Article. In this Article. A sleep study or polysomnogram (PSG) is a test that electronically transmits and records specific physical activities while you sleep. The recordings become data that a qualified sleep specialist analyzes to figure out if you have a sleep disorder. There are four kinds of sleep studies.