- Black hole (Wikipedia)
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly.
- Report of the International polar expedition to Point Barrow, Alaska, in response to the resolution of the [U.S.] House of representatives of December 11, 1884 (archive.org)
The Secretary of War has the honor to transmit to the House of Representatives the report of the International Polar Expedition to Point Barrow, Alaska, together with the letter of the Chief Signal Officer of the Army, of this date, submitting the report to this Department, the same being furnished in response to the resolution of the House of Representatives of December 11, 1884, as follows : “Resolved, That the Secretary of War be requested to transmit to the House of Representatives, if not inconsistent with the public service, the report of the International Polar Expedition to Point Barrow, Alaska, by Lieut. P. H. Ray, U. S. Army, for the years 1881, 1882, and 1883.” ROBERT T. LINCOLN, Secretary of War.