A bolide is an bright meteor one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, it is considered a synonym for a fireball. In geology, a bolide is a large impactor. One definition describes a bolide as a fireball reaching an apparent magnitude of −14 or brighter — more than twice as bright as the full moon. Another definition describes a bolide as any generic large crater-forming impacting body whose composition is unknown. A superbolide is a bolide that reaches an apparent magnitude of −17 or brighter, 100 times brighter than the full moon. Recent examples of superbolides include the Sutter's Mill meteorite in California and the Chelyabinsk meteor in Russia; the IAU has no official definition of "bolide", considers the term synonymous with fireball, a brighter-than-usual meteor. Astronomers tend to use bolide to identify an exceptionally bright fireball one that explodes, it may be used to mean a fireball, audible. Selected superbolide air-bursts events: Tunguska event 2009 Sulawesi superbolide Chelyabinsk meteor Geologists use the term bolide in a somewhat different context than astronomers do.

In geology, it indicates a large impactor. For example, the Woods Hole Coastal and Marine Science Center of the USGS uses bolide for any large crater-forming impacting body whose origin and composition is unknown, as, for example, whether it was a stony or metallic asteroid, or a less dense, icy comet made of volatiles, such as water and methane. Comet Shoemaker–Levy 9 § Impacts Earth-grazing fireball Meteor procession Tollmann's hypothetical bolide historic record of bolides that have been witnessed entering the Earth’s atmosphere around the world from 861 through 2012 Bolide Events 1988 - 2017

2020 Ontario Liberal Party leadership election

The 2020 Ontario Liberal Party leadership election will be held on March 7, 2020 following the resignation of Kathleen Wynne as leader on June 7, 2018, after over five years as leader of the Ontario Liberal Party, a major provincial political party in the province of Ontario, Canada. The deadline for candidates to register was November 2019 at 5:00 pm; the six candidates in the race are Michael Coteau, Steven Del Duca, Kate Graham, Brenda Hollingsworth, Mitzie Hunter, Alvin Tedjo. The Ontario Liberal majority government led by Kathleen Wynne was defeated in the 2018 general election by a wide margin, returning a caucus of just 7 MPPs and losing official party status in the Legislature. Wynne tendered her resignation as party leader, while continuing to sit in the legislature as MPP for Don Valley West. Wynne announced on election night that she had asked the party president to begin the process of choosing an interim leader. According to the party's constitution, an interim leader is to be selected by a vote of the party caucus, the presidents of riding associations without an elected Liberal MPPs and party executive members.

The Liberal caucus unanimously endorsed Ottawa South MPP John Fraser to serve as interim leader on June 13, 2018. Fraser assumed the office of interim leader on June 14, following a vote of party executives and presidents of riding associations for the remaining 117 ridings that do not have a Liberal MPP. Under the procedure outlined by the party's constitution, the leader is to be chosen in a traditional delegated leadership convention in which up to 2,000+ delegates would be eligible to vote, made up of 1,984 elected delegates in addition to ex officio delegates, youth delegates from campus clubs and delegates representing the Women's Commission. Riding delegates would be able to run as independents. Balloting at convention continues until one candidate receives a majority of ballots cast. Candidates had until November 25, 2019 at 5 pm to register and December 2, 2019 was the deadline for individuals who wish to vote to become members of the party. Delegate election meetings are to be held on February 8 and 9, 2019.

An attempt to amend the party constitution to change the leadership election system to a One Member One Vote model was supported by 57% of delegates to the party's Annual General Meeting held on June 8, 2019, failing to receive the two-thirds majority required for it to pass. Candidate Showcase – Thursday, November 28, 2019 at 7:00PM EST Guelph Leadership Debate – Sunday, December 8, 2019 at 1:00PM EST Windsor Leadership Debate – Thursday, December 12, 2019 at 7:00PM EST Sudbury Leadership Debate – Sunday, January 12, 2020 at 1:00PM EST Ottawa Leadership Debate – Wednesday, January 20, 2020 at 7:00PM EST Markham Leadership Debate – Saturday, February 1, 2020 at 1:00PM EST Toronto Leadership Debate – Monday, February 24, 2020 at 7:00PM EST Background: MPP for Don Valley East and Liberal critic for Economic Development, Labour and Infrastructure. Date announced: June 16, 2019 Date registered with Elections Ontario: July 24, 2019 Campaign website: Policies: Background: Former MPP for Vaughan, Former Minister of Economic Development and Growth and Minister of Transportation.

Date announced: April 3, 2019 Date registered with Elections Ontario: July 19, 2019 Campaign website: Policies: Background: 2018 candidate in London North Centre, former civil servant at City of London, instructor at Western UniversityDate announced: September 7, 2019 Date registered with Elections Ontario: August 23, 2019 Campaign website: Policies: Background: Ottawa personal injury lawyer Date announced: November 25, 2019 Date registered with Elections Ontario: Campaign website: Policies: Background: MPP for Scarborough—Guildwood, former Minister of Advanced Education and Skills Development, Minister of Education, Associate Minister of Finance. Date announced: August 14, 2019 Date registered with Elections Ontario: August 20, 2019 Campaign website: Policies: Background: 2018 candidate in Oakville North—Burlington, former director of Government Relations for Sheridan College, former political staff to multiple Ministers of Training and Universities Date announced: May 27, 2019 Date registered with Elections Ontario: August 23, 2019 Policies: Advocates merging the Catholic and public school systems.

Advocate for basic income. Campaign website: Yvan Baker, current federal Liberal MP for Etobicoke Centre, former MPP for Etobicoke Centre, former Parliamentary Assistant to the Minister of Finance Bonnie Crombie, former federal MP for Mississauga—Streetsville, Mayor of Mississauga Nathalie Des Rosiers, former Minister of Natural Resources and Forestry and MPP for


A solenoid is a type of electromagnet, the purpose of, to generate a controlled magnetic field through a coil wound into a packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it; the term solenoid was coined in 1823 by André-Marie Ampère to designate a helical coil. In the study of electromagnetism, a solenoid is a coil whose length is greater than its diameter; the helical coil of a solenoid does not need to revolve around a straight-line axis. In engineering, the term may refer to a variety of transducer devices that convert energy into linear motion; the term is often used to refer to a solenoid valve, an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch. Solenoid bolts, a type of electromechanical locking mechanism exist.

In electromagnetic technology, a solenoid is an actuator assembly with a sliding ferromagnetic plunger inside the coil. Without power, the plunger extends for part of its length outside the coil. Electromagnets with fixed cores are not considered solenoids. An infinite solenoid has infinite length but finite diameter. "Continuous" means that the solenoid is not formed by discrete finite-width coils but by infinitely many infinitely thin coils with no space between them. The magnetic field inside an infinitely long solenoid is homogeneous and its strength neither depends on the distance from the axis nor on the solenoid's cross-sectional area; this is a derivation of the magnetic flux density around a solenoid, long enough so that fringe effects can be ignored. In Figure 1, we know that the flux density vector points in the positive z direction inside the solenoid, in the negative z direction outside the solenoid. We confirm this by applying the right hand grip rule for the field around a wire.

If we wrap our right hand around a wire with the thumb pointing in the direction of the current, the curl of the fingers shows how the field behaves. Since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, the field is only pointing downwards. Now consider the imaginary loop c, located inside the solenoid. By Ampère's law, we know that the line integral of B around this loop is zero, since it encloses no electrical currents. We have shown above that the field is pointing upwards inside the solenoid, so the horizontal portions of loop c do not contribute anything to the integral, thus the integral of the up side 1 is equal to the integral of the down side 2. Since we can arbitrarily change the dimensions of the loop and get the same result, the only physical explanation is that the integrands are equal, that is, the magnetic field inside the solenoid is radially uniform. Note, that nothing prohibits it from varying longitudinally, which in fact it does.

A similar argument can be applied to the loop a to conclude that the field outside the solenoid is radially uniform or constant. This last result, which holds true only near the center of the solenoid where the field lines are parallel to its length, is important as it shows that the flux density outside is zero since the radii of the field outside the solenoid will tend to infinity. An intuitive argument can be used to show that the flux density outside the solenoid is zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can; the magnetic field lines follow the longitudinal path of the solenoid inside, so they must go in the opposite direction outside of the solenoid so that the lines can form a loop. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is reduced. Now recall that the field outside is constant. In order for the total number of field lines to be conserved, the field outside must go to zero as the solenoid gets longer.

Of course, if the solenoid is constructed as a wire spiral it emanates an outside field the same way as a single wire, due to the current flowing overall down the length of the solenoid. Applying Ampère's circuital law to the solenoid gives us B l = μ 0 N I, where B is the magnetic flux density, l is the length of the solenoid, μ 0 is the magnetic constant, N the number of turns, I the current. From this we get B = μ 0 N I l; this equation is valid for a solenoid in fr