Philadelphia once comprised six congressional districts. However, as a result of the city's declining population, it now has only four: the 1st district, represented by Bob Brady; the 2nd, represented by Chaka Fattah; the 8th, represented by Mike Fitzpatrick; and the 13th, represented by Brendan Boyle. All but Fitzpatrick are Democrats. Although they are usually swamped by Democrats in city, state and national elections, Republicans still have some support in the area, primarily in the northeast. A Republican represented a significant portion of Philadelphia in the House as late as 1983, and Sam Katz ran competitive mayoral races as the Republican nominee in both 1999 and 2003.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): How many congressional districts were there at the peak population?
Ah, so.. six

The United States launched the orbital workstation Skylab 1 on May 14, 1973. It weighed 169,950 pounds (77,090 kg), was 58 feet (18 m) long by 21.7 feet (6.6 m) in diameter, with a habitable volume of 10,000 cubic feet (280 m3). Skylab was damaged during the ascent to orbit, losing one of its solar panels and a meteoroid thermal shield. Subsequent manned missions repaired the station, and the final mission's crew, Skylab 4, set the Space Race endurance record with 84 days in orbit when the mission ended on February 8, 1974. Skylab stayed in orbit another five years before reentering the Earth's atmosphere over the Indian Ocean and Western Australia on July 11, 1979.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): The Skylab 1 was launched on which date?
Ah, so.. May 14, 1973

The above explanation is merely a simple introduction to vacuum pumping, and is not representative of the entire range of pumps in use. Many variations of the positive displacement pump have been developed, and many other pump designs rely on fundamentally different principles. Momentum transfer pumps, which bear some similarities to dynamic pumps used at higher pressures, can achieve much higher quality vacuums than positive displacement pumps. Entrapment pumps can capture gases in a solid or absorbed state, often with no moving parts, no seals and no vibration. None of these pumps are universal; each type has important performance limitations. They all share a difficulty in pumping low molecular weight gases, especially hydrogen, helium, and neon.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What other pump do entrapment pumps have similarities to?
Ah, so..
unanswerable