After they collapsed, the hollow core was gone. The remaining rubble was only a few stories high. The twin towers were built between and No building constructed at that time would have been able to withstand the impact of the terrorist attacks in We can, however, learn from the collapse of the skyscrapers and take steps to construct safer buildings and minimize the number of casualties in future disasters. When the twin towers were constructed, the builders were granted some exemptions from New York's building codes.
The exemptions allowed the builders to use lightweight materials so the skyscrapers could achieve great heights. Others say the architectural design actually saved lives.
After the Collapse: A Behavioral Theory of Reputation Repair - Oxford Handbooks
These skyscrapers were designed with redundancies—anticipating that a small plane could accidentally penetrate the skyscraper skin and the building would not fall from that type of accident. The north tower was hit at a. ET, between floors 94 and 98—it did not collapse until a. Even the south tower was able to stand for a remarkable 56 minutes after being hit at a. The second jet hit the south tower on lower floors, between floors 78 and 84, which structurally compromised the skyscraper earlier than the north tower. Most of the south tower occupants, however, began evacuating when the north tower was hit.
The towers could not have been designed any better or stronger.
Nobody anticipated the deliberate actions of an aircraft filled with thousands of gallons of jet fuel. Conspiracy theories often accompany horrific and tragic events. Some occurrences in life are so shockingly incomprehensible that some people begin to doubt theories. They might reinterpret evidence and offer explanations based on their prior knowledge.
Why the World Trade Center Towers Fell on 9/11
Passionate people fabricate what becomes alternative logical reasoning. When the buildings collapsed, some thought it had all of the characteristics of a "controlled demolition. Some people believe that the twin towers were brought down by explosives, although others find no evidence for this belief.
Writing in the Journal of Engineering Mechanics ASCE, researchers have shown "the allegations of controlled demolition to be absurd" and that the towers "failed due to gravity-driven progressive collapse triggered by the effects of fire. Engineers examine evidence and create conclusions based on observations. On the other hand, the Movement seeks the "suppressed realities of September 11th" that will support their mission. Conspiracy theories tend to continue in spite of the evidence.
While architects strive to design safe buildings, developers don't always want to pay for over-redundancies to mitigate outcomes of events that are unlikely to happen. Tall office buildings are required to have more durable fireproofing, extra emergency exits, and many other fire safety features. Share Flipboard Email. Table of Contents Expand. Aircraft Impact.
After the Collapse
Heat From Fires. Collapsing Floors. Why They Flattened. Strong Enough? Legacy on Building. Jackie Craven, Doctor of Arts in Writing, has over 20 years of experience writing about architecture and the arts. The observer simultaneously measures the classical value of that observable to be the eigenvalue of the final state.
The quantum state of a physical system is described by a wave function in turn — an element of a projective Hilbert space. This can be expressed in Dirac or bra—ket notation as a vector:. They form an orthonormal eigenvector basis , formally. An observable i. A "measurable parameter of the system" could be the usual position r and the momentum p of say a particle, but also its energy E , z components of spin s z , orbital L z and total angular J z momenta etc. The coefficients c 1 , c 2 , c These are complex numbers.
For simplicity in the following, all wave functions are assumed to be normalized ; the total probability of measuring all possible states is one:. With these definitions it is easy to describe the process of collapse. However, we never observe collapse to a single eigenstate of a continuous-spectrum operator e. In these cases, the wave function will partially collapse to a linear combination of "close" eigenstates necessarily involving a spread in eigenvalues that embodies the imprecision of the measurement apparatus.
The more precise the measurement, the tighter the range. The complete set of orthogonal functions which a wave function will collapse to is also called preferred-basis. In fact the eigenstates of position are not even physical due to the infinite energy associated with them. A better approach is to derive the preferred-basis from basic principles. It is proved that only special dynamic equation can collapse the wave function. Depending on the system Hamiltonian and wave function , the determination equations may yield preferred-basis as energy eigenfunctions , quasi-position eigenfunctions , or a mixed energy and quasi-position eigenfunctions ; such as an energy eigenfunctions for the interior of a macroscopic object and the quasi-position eigenfunctions for the particles on the surface.
Wave function collapse is not fundamental from the perspective of quantum decoherence. He, however, emphasized that it should not be understood as a physical process.
Consistent with Heisenberg, von Neumann postulated that there were two processes of wave function change:. By explicitly dealing with the interaction of object and measuring instrument , von Neumann  has attempted to create consistency of the two processes of wave function change. He was able to prove the possibility of a quantum mechanical measurement scheme consistent with wave function collapse. However, he did not prove the necessity of such a collapse. Although von Neumann's projection postulate is often presented as a normative description of quantum measurement, it was conceived by taking into account experimental evidence available during the s in particular the Compton-Simon experiment was paradigmatic , but many important present-day measurement procedures do not satisfy it so-called measurements of the second kind.
The cluster of phenomena described by the expression wave function collapse is a fundamental problem in the interpretation of quantum mechanics, and is known as the measurement problem. The problem is deflected by the Copenhagen Interpretation, which postulates that this is a special characteristic of the "measurement" process.
Originating from de Broglie—Bohm theory, but no longer tied to it, is the physical process of decoherence , which causes an apparent collapse. Decoherence is also important for the consistent histories interpretation. A general description of the evolution of quantum mechanical systems is possible by using density operators and quantum operations.
The significance ascribed to the wave function varies from interpretation to interpretation, and varies even within an interpretation such as the Copenhagen Interpretation. If the wave function merely encodes an observer's knowledge of the universe then the wave function collapse corresponds to the receipt of new information. This is somewhat analogous to the situation in classical physics, except that the classical "wave function" does not necessarily obey a wave equation.
If the wave function is physically real, in some sense and to some extent, then the collapse of the wave function is also seen as a real process, to the same extent. From Wikipedia, the free encyclopedia.
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For other uses, see Collapse. Process by which a quantum system takes on a definitive state.
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Classical mechanics Old quantum theory Bra—ket notation Hamiltonian Interference. Advanced topics. Quantum annealing Quantum chaos Quantum computing Density matrix Quantum field theory Fractional quantum mechanics Quantum gravity Quantum information science Quantum machine learning Perturbation theory quantum mechanics Relativistic quantum mechanics Scattering theory Spontaneous parametric down-conversion Quantum statistical mechanics.
For an explanation of the notation used, see bra—ket notation. For details on this formalism, see quantum state. This section may present fringe theories , without giving appropriate weight to the mainstream view , and explaining the responses to the fringe theories. Please help improve it or discuss the issue on the talk page.