E4
1.e4, commonly notated as the King's Pawn Opening in chess, constitutes White's most frequent initial move, advancing the pawn guarding the king two squares toward the opponent's side to seize control of the central d5 and f5 squares while unblocking lines for the king's bishop and queen.[1] This strategic gambit, rooted in the principles of rapid piece development and territorial dominance established since the codification of modern chess rules in the late 15th century, underpins a vast array of subsequent variations, including open games against Black's mirroring 1...e5—such as the Italian Game and Ruy Lopez—and semi-open defenses like the Sicilian (1...c5) or French (1...e6).[2] Employed extensively by elite players including former world champions Bobby Fischer, who favored aggressive 1.e4 lines for their tactical dynamism, and Garry Kasparov, who integrated it into his repertoire for its flexibility in both positional and sharp middlegames, the opening exemplifies causal realism in chess theory by prioritizing empirical advantages in space and initiative over speculative gambits.[3] While debates persist on its optimality versus 1.d4 in hypermodern contexts—evidenced by database analyses showing comparable win rates at master levels—1.e4 remains a cornerstone for aspiring players due to its alignment with fundamental tenets of center occupation and harmonious development, free from the biases of transient fashion in opening theory.[4]Entertainment
Broadcasting
E4 launched on 18 January 2001 as a subscription-based digital companion channel to Channel 4, initially available exclusively on Sky Digital (channel 163) and cable platforms such as NTL and Telewest, targeting viewers aged 16-34 with entertainment programming broadcast for 12 hours daily.[5][6] On 10 May 2005, Channel 4 introduced the E4 Music Zone, extending broadcasts to 24 hours a day by filling mornings with music videos, marking the channel's first full-day programming.[7] Channel 4 announced on 16 December 2004 that E4 would transition to free-to-air status on digital terrestrial television (DTT), with the launch occurring on 27 May 2005 via the Freeview platform (channel 13 in England, Scotland, and Northern Ireland; channel 14 in Wales), coinciding with the start of Big Brother series 6 to capitalize on event-driven viewership.[8] This move aligned with the ongoing UK digital switchover process, which began in 2008 and completed nationwide by 2012, enabling wider terrestrial access without subscription fees, though E4 had been available on DTT pay services like Top Up TV since March 2004.[8] E4 is transmitted free-to-air across multiple platforms in the United Kingdom, including DTT via Freeview and Youview (channel 13), satellite via Freesat (channel 122) and Sky (channel 135 for SD/HD, channel 235 for +1 timeshift), and cable via Virgin Media (channel 134).[9] A high-definition simulcast, E4 HD, debuted on 14 December 2009 on Sky+ HD (channel 215), expanding to Virgin Media on 1 April 2010, with content upscaled or natively produced in HD to enhance visual quality for compatible receivers.[10] The channel's streaming service, integrated into Channel 4's on-demand platform, became available alongside linear broadcasts, offering live and catch-up viewing geo-restricted to the UK and Republic of Ireland, with 2024 streaming metrics showing significant growth in young adult engagement (24% of total viewing from 16-34-year-olds).[11] E4 maintains a consistent broadcast schedule emphasizing youth-oriented entertainment, with advertising-funded transmission adhering to Ofcom regulations for public service channels.[12]Transportation
Roads
The European route E4 is a primary north-south trunk road spanning approximately 1,590 kilometers through Sweden, connecting the border with Finland at Haparanda in the north to Helsingborg in the south.[13] It serves as the country's principal longitudinal highway, facilitating freight and passenger transport along much of Sweden's eastern seaboard parallel to the Gulf of Bothnia and the Baltic Sea.[14] The route integrates with national road numbering, often coinciding with Swedish trunk roads like Riksväg 75 in the north and Europaväg 4 signage throughout.[13] From its northern terminus at the E10 junction near Haparanda, E4 proceeds southward through Norrbotten County, passing Luleå and Piteå before reaching Boden and continuing via Umeå in Västerbotten County. Further south, it traverses Sundsvall, Hudiksvall, and Gävle in central Sweden, entering Stockholm County where it encounters heavy urban congestion around the capital. Beyond Stockholm, the highway links Norrköping, Linköping, Jönköping, and Huskvarna in Östergötland and Jönköping Counties, terminating at Helsingborg in Skåne County near the Öresund Strait.[13] [15] Sections vary from four-lane divided motorways in populated areas to two-lane alignments in rural northern stretches, with speed limits typically ranging from 90 to 120 km/h where conditions permit.[16] E4 functions as a critical artery for Sweden's economy, carrying over 100,000 vehicles daily near Stockholm and supporting timber, mineral, and industrial logistics from the north.[17] Traffic volumes have strained the route, particularly the 30-kilometer segment through Stockholm, which lacks capacity for projected growth from population increases and regional commuting.[17] To address this, the Swedish Transport Administration (Trafikverket) is constructing the E4 Stockholm Bypass, a 21-kilometer motorway with 18 kilometers in tunnels, designed to divert through-traffic and reduce inner-city loads by up to 30 percent upon completion expected in the mid-2030s.[18] Other upgrades include the 31-kilometer widening and safety enhancements between Ljungby and Toftanäs in Småland, completed in phases to improve flow and reduce accident rates on curvier sections.[19] Safety features along E4 incorporate variable speed limits, radar-based vehicle detection for congestion management, and barriers in high-risk zones, responding to challenges like winter icing and heavy truck volumes.[20] [21] The route's development aligns with European Agreement on Main International Traffic Arteries (AGR) standards, emphasizing connectivity to Finland and Denmark via ferries from Helsingborg.[13]Railways
The E4 designation in railways applies to multiple locomotive and trainset classes across different operators and eras. The London, Brighton and South Coast Railway (LB&SCR) E4 class comprised 75 0-6-2T side-tank steam locomotives designed by Robert J. Billinton, constructed between 1897 and 1903 at Brighton Works.[22] Intended primarily for suburban passenger services and mixed traffic, the design evolved from the earlier E3 class with enlarged 5 ft diameter driving wheels for improved speed and a radial trailing axle to enhance stability, coal capacity (3 tons), and water capacity (1,408 gallons).[22] Key specifications included inside cylinders measuring 17.5 in × 26 in, a boiler pressure of 160 psi, and a tractive effort of 18,045 lbf, with an overall weight of 57 tons 10 cwt.[22] Post-1923 railway grouping, the class saw continued use under the Southern Railway and British Railways for freight and passenger workings until the early 1960s, with the last withdrawals occurring around 1962.[22] One locomotive, No. 70 Birch Grove (built 1898), survives in preservation at the Bluebell Railway, where it operated intermittently from 1962 until undergoing major overhaul in 2016 due to firebox issues; it now serves as a static exhibit.[22] The Great Eastern Railway (GER) E4 class, classified as T26 during construction, consisted of 100 2-4-0 steam locomotives designed by James Holden and built between 1891 and 1902.[23] Suited for mixed-traffic duties such as agricultural trains, cross-country services, and slower main-line passenger workings, these locomotives featured 5 ft 8 in driving wheels for responsive performance and rearranged steam passages for efficiency, delivering a tractive effort of 14,700 lbf at 85% boiler pressure with a maximum axle load of 14 tons 3 cwt.[23] Under the London and North Eastern Railway (LNER) from 1923, they retained the E4 classification but were restricted to Route Availability Group 2 due to their axle loading, with most scrapped by the 1930s amid dieselization and electrification trends.[23] None are preserved. Japan's E4 series represented a modern application, as an 8-car (expandable to 16-car) double-decker electric multiple unit (EMU) introduced in 1997 by East Japan Railway Company (JR East) for high-capacity Tohoku and Joetsu Shinkansen services.[24] The sets accommodated 1,634 seated passengers in full 16-car formation, prioritizing volume over speed to handle peak demand.[24] Regular operations ceased on October 1, 2021, following replacement by the E5 series, which provided reduced weight, faster acceleration, higher top speeds, and greater scheduling flexibility to meet evolving transport needs without double-deck constraints.[24]Military
Aircraft
The E-4B aircraft, designated as the Advanced Airborne Command Post and nicknamed "Nightwatch," serves as the National Airborne Operations Center (NAOC) for the United States Air Force, enabling the President, Secretary of Defense, and Chairman of the Joint Chiefs of Staff to maintain command and control of U.S. nuclear and conventional forces during national emergencies or disruptions to ground-based facilities.[25][26] A militarized variant of the Boeing 747-200, it features hardened construction against electromagnetic pulse (EMP) effects, nuclear blasts, and radiation, with an advanced electrical system supporting extensive communications equipment for global connectivity via satellite, high-frequency radio, and secure data links.[25][27] Development began in the early 1970s as a successor to the EC-135 Airborne Command Post, with the first E-4A prototype flying on June 13, 1973, and achieving initial operational capability in December 1974; all four initial aircraft were delivered between 1974 and 1977.[27] Upgrades to the E-4B standard, completed by 1985, enhanced communications bandwidth, added battle staff facilities, and incorporated improved survivability features, including redundant systems and aerial refueling capability for extended airborne operations.[25][26] The fleet, consisting of four aircraft operated by the 1st Airborne Command and Control Squadron at Offutt Air Force Base, Nebraska, under Air Force Global Strike Command, maintains one plane on continuous alert, capable of takeoff within minutes of notification.[25] Key capabilities include directing emergency war orders, coordinating joint forces, and providing a survivable platform for continuity of government operations, with interior configurations supporting up to 112 personnel, including flight crew, battle staff, maintenance, security, and communications teams across multiple compartments for command, operations, and rest.[26][27] It lacks offensive armament but relies on speed, altitude, and stealthy mission profiles for protection, with a maximum speed of approximately 600 mph and a range of 7,010 miles unrefueled, extendable indefinitely via KC-135 or KC-46 tankers.[25]| Specification | Details |
|---|---|
| Crew | Flight: 26; Mission: up to 86 additional |
| Dimensions | Length: 231 ft 4 in (70.5 m); Wingspan: 195 ft 8 in (59.6 m); Height: 63 ft 5 in (19.3 m) |
| Engines | 4 × General Electric F103-GE-100 turbofans |
| Maximum Takeoff Weight | 800,000 lb (363,000 kg) |
| Service Ceiling | 42,000 ft (12,800 m) |
Personnel ranks
In the United States Armed Forces, the E-4 pay grade designates the fourth level of enlisted personnel, typically achieved after promotion from E-3 following 18–24 months of service, depending on the branch and performance.[28] This grade marks the transition from junior enlisted roles to positions with increased technical expertise or limited supervisory duties, though responsibilities vary by branch-specific rank titles.[29] Basic monthly pay for an E-4 in fiscal year 2025 ranges from $3,027.30 for those with less than two years of service to $3,824.10 for those with over six years, excluding allowances for housing, subsistence, and special duties.[30] Branch-specific ranks at E-4 reflect distinct organizational structures and missions. In the Army, E-4 personnel hold either the rank of Specialist (SPC), focused on specialized technical skills without command authority, or Corporal (CPL), a non-commissioned officer role involving junior leadership and squad-level supervision.[31] The Marine Corps assigns E-4 to Corporal (CPL), emphasizing small-unit leadership as the first NCO grade.[32] The Navy and Coast Guard use Petty Officer Third Class (PO3), which involves rate-specific technical duties and petty officer responsibilities within divisions.[28] The Air Force and Space Force designate Senior Airman (SrA), prioritizing mission execution and eligibility for NCO roles upon further promotion.[29]| Branch | E-4 Rank Title(s) | Key Responsibilities |
|---|---|---|
| Army | Specialist (SPC), Corporal (CPL) | Technical specialization (SPC); junior leadership (CPL)[31] |
| Marine Corps | Corporal (CPL) | Squad-level supervision as entry-level NCO[32] |
| Navy | Petty Officer Third Class (PO3) | Division technical support and watchstanding[28] |
| Air Force/Space Force | Senior Airman (SrA) | Airman development and mission support[29] |
| Coast Guard | Petty Officer Third Class (PO3) | Sector-specific operations and enforcement[28] |