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Newton's Laws

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# Were Newton's laws superseded by quantum mechanics?

1 year ago

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31 Replies

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Kara Johnston

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Nicholas Miller

Newton's laws are still used today because they more or less work fine. We used Newton's laws to go to the moon. However when travelling at any appreciable speed and when accuracy is paramount (think GPS satellites) Special Relativity is used to make more accurate calculations.

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Newton's laws are a good model for day-to-day purposes. There are circumstances they do not fully describe - those involving very high speeds, strong gravitational fields, or very small scales. The first two need General Relativity, the third Quantum Mechanics. If a situation involves all three then all bets are off! Quantum Mechanics, however, provides more accurate modelling of a whole range of physical phenomena, particularly to do with electromagnetism, not just mechanical ones.

It's worth noting that Newtonian Mechanics was enough to get astronauts to the Moon and back.

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Farid Arya Arya

Hi. There is no conflict between Newton´s laws and quantum mechanics.

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Savio Antonio Vogt

No. Newton's laws are derterministic for objects in space-time that operate in everyday life. However, Quantum Mechanics describes the unseen world. It seems absurd that QM in principle, superseeds Newton's laws but, if one digs deeper, QM does make use of Newton's Laws or Newtonion Mechanics when they are 'Generalized'. Some examples are Hamiltonion, Lagrangian, and Routhinian Mechanics. Hope this answers your question.

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Sidra Shuja

No. Newton's laws are used to explain our daily life while at the atomic level, they fail to explain the motion and nature of atoms and that is where quantum mechanics come in. Therefore, Newton's laws are still in use.

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Joel Douglas-Jones

No they weren’t, Newtonian mechanics are very useful and accurate on the scales we work with generally in day to day life, Quantum mechanics on these scales produce the same answers as Newtonian mechanics, we only see large disparities between the two at the ~atomic scale

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Louis Houseman

Quantum mechanics do violate newtons laws, spesiffically his first law. However, quantum mechanics hasn't nessacarily 'superseded' newtons laws as quantum mechanics essentially describes different scales than what newtons laws describe. Newtons laws describe earthy mechanics (things that we may see and experience) quantum mechanics on the other hand deals with the extremely small, mostly they do not adress the same problems. Something that could be said to have superseded Newtons laws is relativity, (get in contact with me for a conversation about that).

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"to infinity and beyond!"

Good question, the answer is no, they weren't superseded, because the two describe different regimes.

Newton's Laws pertain to something called 'classical physics', which works with the macroscopic (large scale) going-ons of the macroscopic world. Classical physics is 'deterministic' (a.k.a, you can measure things and get concrete answers, like knowing both the position and speed of a car on the motorway, for instance.)

However, when applied to calculations concerning the quantum world - the scale of atoms and below - Newton's laws fail to correctly predict things.

Quantum mechanics (QM) is the study of quantum objects and is a theory that explains things on that scale with exquisite precision. However, because of the speeds at which some quantum objects are travelling, QM says one cannot know, with infinite precision, both the position and speed of an object. This statistical nature is what differentiates it from the absolute deterministic nature of our familiar classical world.

To surmise:

classical mechanics says: 'the car's travelling this fast and here it is.'

quantum mechanics says: 'this electron is more likely here than there, and it's more likely travelling faster than slower.'

For the moment, Classical Physics and Quantum Physics stand apart, divorced, because no one yet knows how to blend the two into one theory. This is one of physics frontier questions, (and if you solve it, you'll be rich!) so for the moment, we just use the two separately.

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Daniel Olokpo

No it doesn’t but in a miscroscopic word it does

when the energy is little or the masses are small

Quantum mechanics never set newtons law incorrect

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Aaron Mark Thomas

The answer is both yes and no! Newton's laws concern physics on large scales (in comparison to an atom) and so isn't truly in the realm of quantum mechanics which deals with physics on the smallest of scales. Newton's laws were in fact superseded by Einstein's theory of general relativity which deals with phenomena on the largest of scales

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Majd Yousof

Newton's Laws are inapplicable in atomic and subatomic scales, due to the added consideration of strong, weak and electromagnetic forces. So ultimately, at a larger scale, Newton's Laws are applicable, however on the quantum scale they aren't.

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Newton's laws remain a valid approximation that work well in everyday situations. We can still safely use our three laws of motion when doing problems about things like the motion of cars on the road.

Einstein's theory of relativity provides a more complete framework that takes into account the behaviour of objects as they approach the speed of light, and is needed for understanding how astronomical phenomena like black holes work.

Quantum mechanics provides insight into the behaviour of matter on a very small scale, and does in some sense supersede Newton's laws for the behaviour of atoms and other particles. We can't really treat atoms like billiard balls that simply bounce off each other - at a quantum scale things are different and more 'fuzzy'.

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Not really. In terms of A-level Newton's Laws are fully correct for macroscopic objects-even those requiring a microscope to see-i.e persons, planets, vehicles, tiny oil drops etc. Quantum physics only applies to subatomic particles. Additionally, subatomic particles conserve momentum in the Newtonian was...

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Gabriel Pinheiro Sanchez

Hi Kara,

This is an interesting question. Maybe trying to reframe it would make you understand it better. You can think of Mechanics as a subfield of Physics, it deals primarily with static or moving bodies inserted into a certain space. Newton's Laws of Mechanics apply in a specific area of this subfield, that of the visible world, anything from an ant to a jet will comply to Newton's equations just fine with little to no error.

However, when we move our observed space into smaller or bigger objects, these equations, while still somewhat valid, start to break apart and return wrong results when measured experimentally. That is where quantum mechanics comes in. The equations that Dirac, Plank, among others developed, work very well for objects inside this size scale, for example an atom can have a radius of 0.1 nanometers (that's 10000000000 times smaller than a meter!), here quantum mechanics works perfectly.

Now, for an extra thought, if we go to a large scale, a whole planet for example, General and Special relativity become the standard Mechanical equations we deal with. While Newton's equations work relatively better than for quantum scales, it still does not account for many phenomena we observe with objects so massive.

TL;DR It is not a matter of superseding one another, these theories complement each other to provide a complete view of our universe and the phenomena around us. As Newton famously said “If I have seen further it is by standing on the shoulders of Giants".

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Yes, within the quantum domain. This mean when we start looking at scales at an atomic level, Newton's laws do not apply and quantum mechanical effects take place. However, on bigger scales such as where us humans operate day to day life like going on a run or driving a car; Classical mechanics takes place where Newton's laws operate.

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