Thursday, March 19, 2020

First Battle of the Marne in World War I

First Battle of the Marne in World War I The First Battle of the Marne was fought September 6-12, 1914, during World War I (1914-1918) and marked the limit of Germanys initial advance into France. Having implemented the Schlieffen Plan at the wars outset, German forces swung through Belgium and into France from north. Though pushing back French and British forces, a gap opened between two armies on the German right wing. Exploiting this, the Allies attacked into the gap and threatened to encircle the German First and Second Armies. This forced the Germans to halt their advance and retreat behind the Aisne River. Dubbed the Miracle of the Marne, the battle saved Paris, ended German hopes of a quick victory in the west, and touched off the Race to the Sea which would create the front that would largely hold for the next four years. Fast Facts: First Battle of the Marne Conflict: World War I (1914-1918)Dates: September 6-12, 1914Armies Commanders:GermanyChief of Staff Helmuth von Moltkeapprox. 1,485,000 men (August)AlliesGeneral Joseph JoffreField Marshal Sir John French1,071,000 menCasualties:Allies: France - 80,000 killed, 170,000 wounded, Britain - 1,700 killed, 11,300 woundedGermany: 67,700 killed, 182,300 wounded Background With the outbreak of World War I, Germany began implementation of the Schlieffen Plan. This called for the bulk of their forces to assemble in the west while only a small holding force remained in the east. The goal of the plan was to quickly defeat France before the Russians could fully mobilize their forces. With France defeated, Germany would be free to focus their attention to the east. Devised earlier, the plan was altered slightly in 1906 by Chief of the General Staff, Helmuth von Moltke, who weakened the critical right wing to reinforce Alsace, Lorraine, and the Eastern Front (Map). Chief of the German General Staff Helmuth von Moltke. With the outbreak of World War I, the Germans implemented the plan which called for violating the neutrality of Luxembourg and Belgium in order to strike France from the north (Map). Pushing through Belgium, the Germans were slowed by stubborn resistance which allowed the French and arriving British Expeditionary Force to form a defensive line. Driving south, the Germans inflicted defeats on the Allies along the Sambre at the Battles of Charleroi and Mons. Fighting a series of holding actions, French forces, led by commander-in-chief General Joseph Joffre, fell back to a new position behind the Marne with the goal of holding Paris. Angered by the French proclivity for retreating without informing him, the commander of the BEF, Field Marshal Sir John French, wished to pull the BEF back towards the coast but was convinced to stay at the front by War Secretary Horatio H. Kitchener. On the other side, the Schlieffen Plan continued to proceed, however, Moltke was increasingly losing control of his forces, most notably the key First and Second Armies. Marshal Joseph Joffre. Photograph Source: Public Domain Commanded by Generals Alexander von Kluck and Karl von Bà ¼low respectively, these armies formed the extreme right wing of the German advance and were tasked with sweeping to the west of Paris to encircle Allied forces. Instead, seeking to immediately envelop the retreating French forces, Kluck and Bà ¼low wheeled their armies to the southeast to pass to the east of Paris. In doing so, they exposed the right flank of the German advance to attack. Becoming aware of this tactical error on September 3, Joffre began making plans for a counter-offensive the next day. Moving to Battle To aid this effort, Joffre was able to bring General Michel-Joseph Maunourys newly-formed Sixth Army into line northeast of Paris and to the west of the BEF. Using these two forces, he planned to attack on September 6. On September 5, Kluck learned of the approaching enemy and began to wheel his First Army west to meet the threat posed by Sixth Army. In the resulting Battle of the Ourcq, Klucks men were able to put the French on the defensive. While the fighting prevented the Sixth Army from attacking the next day, it did open a 30-mile gap between the First and Second German Armies (Map). Into the Gap Utilizing the new technology of aviation, Allied reconnaissance planes quickly spotted this gap and reported it to Joffre. Quickly moving to exploit the opportunity, Joffre ordered General Franchet dEspà ©reys French Fifth Army and the BEF into the gap. As these forces moved to isolate the German First Army, Kluck continued his attacks against Maunoury. Composed largely of reserve divisions, the Sixth Army came close to breaking but was reinforced by troops brought from Paris by taxicab on September 7. On September 8, the aggressive dEspà ©rey launched a large-scale attack on Bà ¼lows Second Army driving it back (Map). Field Marshal Sir John French. Photograph Source: Public Domain By the next day, both the German First and Second Armies were being threatened with encirclement and destruction. Told of the threat, Moltke suffered a nervous breakdown. Later that day, the first orders were issued for a retreat effectively negating the Schlieffen Plan. Recovering, Moltke directed his forces across the front to fall back to a defensive position behind the Aisne River. A wide river, he stipulated that the lines so reached will be fortified and defended. Between September 9 and 13, German forces broke off contact with the enemy and retreated north to this new line. Aftermath Allied casualties in the fighting numbered around 263,000, while the Germans incurred similar losses. In the wake of the battle, Moltke reportedly informed Kaiser Wilhelm II, Your Majesty, we have lost the war. For his failure, he was replaced as Chief of the General Staff on September 14 by Erich von Falkenhayn. A key strategic victory for the Allies, the First Battle of the Marne effectively ended German hopes for a quick victory in the west and condemned them to a costly two-front war. Reaching the Aisne, the Germans halted and occupied the high ground north of the river. Pursued by the British and French, they defeated Allied attacks against this new position. On September 14, it was clear that neither side would be able to dislodge the other and the armies began entrenching. At first, these were simple, shallow pits, but quickly they became deeper, more elaborate trenches. With the war stalled along the Aisne in Champagne, both armies began efforts to turn the others flank in the west. This resulted in a race north to the coast with each side seeking to turn the others flank. Neither was successful and, by the end of October, a solid line of trenches ran from the coast to the Swiss frontier.

Tuesday, March 3, 2020

De Broglie Wavelength Hypothesis Overview

De Broglie Wavelength Hypothesis Overview The De Broglie hypothesis proposes that all matter exhibits wave-like properties and relates the observed wavelength of matter to its momentum. After Albert Einsteins photon theory became accepted, the question became whether this was true only for light or whether material objects also exhibited wave-like behavior. Here is how the De Broglie hypothesis was developed. De Broglies Thesis In his 1923 (or 1924, depending on the source) doctoral dissertation, the French physicist Louis de Broglie made a bold assertion. Considering Einsteins relationship of wavelength lambda to momentum p, de Broglie proposed that this relationship would determine the wavelength of any matter, in the relationship: lambda h / p recall that h is Plancks constant This wavelength is called the de Broglie wavelength. The reason he chose the momentum equation over the energy equation is that it was unclear, with matter, whether E should be total energy, kinetic energy, or total relativistic energy. For photons, they are all the same, but not so for matter. Assuming the momentum relationship, however, allowed the derivation of a similar de Broglie relationship for frequency f using the kinetic energy Ek: f Ek / h Alternate Formulations De Broglies relationships are sometimes expressed in terms of Diracs constant, h-bar h / (2pi), and the angular frequency w and wavenumber k: p h-bar * kEk h-bar * w Experimental Confirmation In 1927, physicists Clinton Davisson and Lester Germer, of Bell Labs, performed an experiment where they fired electrons at a crystalline nickel target. The resulting diffraction pattern matched the predictions of the de Broglie wavelength. De Broglie received the 1929 Nobel Prize for his theory (the first time it was ever awarded for a Ph.D. thesis) and Davisson/Germer jointly won it in 1937 for the experimental discovery of electron diffraction (and thus the proving of de Broglies hypothesis). Further experiments have held de Broglies hypothesis to be true, including the quantum variants of the double slit experiment. Diffraction experiments in 1999 confirmed the de Broglie wavelength for the behavior of molecules as large as buckyballs, which are complex molecules made up of 60 or more carbon atoms. Significance of the de Broglie Hypothesis The de Broglie hypothesis showed that wave-particle duality was not merely an aberrant behavior of light, but rather was a fundamental principle exhibited by both radiation and matter. As such, it becomes possible to use wave equations to describe material behavior, so long as one properly applies the de Broglie wavelength. This would prove crucial to the development of quantum mechanics. It is now an integral part of the theory of atomic structure and particle physics. Macroscopic Objects and Wavelength Though de Broglies hypothesis predicts wavelengths for ​matter of any size, there are realistic limits on when its useful. A baseball thrown at a pitcher has a de Broglie wavelength that is smaller than the diameter of a proton by about 20 orders of magnitude. The wave aspects of a macroscopic object are so tiny as to be unobservable in any useful sense, although interesting to muse about.