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Expert Voices

Do We Live in a Quantum World?

Abstract illustration of particles interacting at the quantum level.
Abstract illustration of particles interacting at the quantum level.
(Image: © Shutterstock)

Paul M. Sutter is an astrophysicist at The Ohio State University, host of Ask a Spaceman and Space Radio, and author of "Your Place in the Universe." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights

Let's face it: quantum mechanics is really confusing. All the rules of physics that we're used to simply go straight out the window in the quantum realm. 

Put a particle in a box. According to classical physics (and common sense), that particle should stay in that box forever. But under quantum mechanics, that particle can simply be outside the box the next time you look. In classical thinking, you can measure the momentum and position of something to an arbitrary degree of precision. Not so in the quantum world — the more you know about one, the less you know about the other. Is something a wave or a particle? According to the classical viewpoint, you can pick one and only one. But ask your friendly neighborhood quantum mechanic, and they'll tell you something can be both.

Related: Objective Reality Doesn't Exist, Quantum Experiment Shows

The quantum world is hard to understand, but at some point the rules of the subatomic give way to the rules of the macroscopic. But how? We're not exactly sure, and it's been a long, strange journey in trying to answer that question.

One atom at a time

The first person to put some useful labels on the quantum world was physicist Niels Bohr. In the early 1900s, scientists around the world were beginning to awaken to the strange and unexpected behavior of atomic and subatomic systems. They had, after decades of grueling work, realized that certain properties, like energy, come in discrete packets of levels dubbed "quanta." And while physicists were beginning to sketch out a mathematical foundation to explain these experiments, nobody had yet developed a complete, consistent framework. 

Bohr was one of the first to attempt it. And while he didn't provide a full theory of quantum mechanics, he did lay some serious groundwork. He also promoted some ideas that would become the cornerstones of modern quantum theory.

The first appeared in his early attempt to model the atom. In the 1920s, we had known through a variety of very cool experiments that the atom is made of a heavy, dense, positively charged nucleus surrounded by a swarm of tiny, light, negatively charged electrons. We also knew that these atoms could only absorb or emit radiation at very specific energies.

But, like, what did it look like?

Bohr put the electrons "in orbit" around the nucleus, waltzing around that dense core like planets in an eensy-teensy solar system. In a real solar system, the planets can have whatever orbit they like. But in Bohr's atom the electrons were stuck on little tracks — they could only have certain predefined orbital distances. 

By jumping from one orbit to another, the atom could receive or emit radiation at specific energies. Its quantum nature was thus encoded.

Related: How a Last-Ditch Hack Led to the Invention of Quantum Mechanics

A quantum connection

But Bohr added one more interesting twist. There are a lot of potential ways to construct a quantum model of the atom — why should this one be used? He found that when the electrons orbited very far away from the nucleus, their quantum nature disappeared and the atom could be perfectly described by classical electromagnetism. Just two charged particles hanging out.

This was called the Correspondence Principle, and it was Bohr's argument that his model of the atom was the best. You can have any quantum theory you want, but the right ones are the ones that give way to classical physics under some limit. In the case of his atom, when the electrons got far away from the nucleus.

Bohr's model of the atom was incomplete and would later be replaced by the valence shell model that remains to this day. But his Correspondence Principle lived on, and it formed a cornerstone of all quantum theories to come — a guiding light that allowed physicists to construct and select the right mathematics to describe the subatomic world.

But Bohr didn't stop there. He argued that, even though this Correspondence Principle allowed a connection between the quantum and classical worlds, those two worlds are not the same. 

No quantum for you

Around the same time that Bohr was puzzling all this out, his good buddy Werner Heisenberg came up with his soon-to-be-famous Uncertainty Principle. Try to measure the position of a tiny particle, and you'll end up losing information about its momentum. Go for the opposite, trying to pin down its momentum, and you'll become ignorant about its position.

Bohr took this idea and ran with it. He saw Heisenberg's Uncertainty Principle as a part of a much larger facet of the quantum world: that everything comes in pairs. Consider the most famous pair in the quantum world, the wave and the particle. In classical systems, something is either purely a wave or purely a particle. You can pick one or the other to classify some behavior. But in quantum mechanics, these two properties are paired up: everything is simultaneously both a particle and a wave and always exhibits some properties of both.

Plus, at its heart, quantum rules rely on probabilities — quantum mechanics only reproduces classical physics on average. Based on these two insights, Bohr argued that a quantum theory can never explain classical physics. In other words, atoms and their ilk operate under one set of rules, and trains and people operate on another set of rules. They can and must be connected via the Correspondence Principle, but otherwise they live separate and parallel lives.

Was Bohr right? Some physicists argue that we just haven't worked hard enough, and that we do fundamentally live in a quantum world, and that we can reproduce classical physics from purely quantum rules. Other physicists argue that Bohr nailed it and we don't need to talk about it anymore. Most just keep their heads down and crunch through the math without worrying about it too much.

But still, it's something to think about.

Learn more by listening to the episode "Why can't I quantum tunnel myself?" on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Thanks to Roberts L., Lieven S., @g33ksquared, James W., Benjamin T., @newportfloat, @smattywood, and Maria A. for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter. 

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  • voidpotentialenergy
    Can i say Yes and No? I'm working on a theory on time and space that seems to answer many of the quantum riddles and duality of the universe. It's about as far from standard thinking as possible.

    If your interested i will try and communicate it here best i can.
    Warning though it's conjecture and will rub those in the field without imagination the wrong way.
    Reply
  • rod
    Interesting report showing some of the struggles in science between quantum mechanics and the macro universe we live in. The science used to overthrow the geocentric firmament and accept the heliocentric solar system is not based upon quantum mechanic uncertainties and not knowing where an object is that can be seen with a telescope, e.g. the 11-Nov Mercury transit and times predicted for observing as well as locations where the celestial event could be seen. It seems if we apply the quantum world to the heliocentric solar system - the Earth can be immovable and modern astronomy is overthrown. Presently the marriage of the quantum world with General Relativity (example) is a work in progress.
    Reply
  • voidpotentialenergy
    rod said:
    Interesting report showing some of the struggles in science between quantum mechanics and the macro universe we live in. The science used to overthrow the geocentric firmament and accept the heliocentric solar system is not based upon quantum mechanic uncertainties and not knowing where an object is that can be seen with a telescope, e.g. the 11-Nov Mercury transit and times predicted for observing as well as locations where the celestial event could be seen. It seems if we apply the quantum world to the heliocentric solar system - the Earth can be immovable and modern astronomy is overthrown. Presently the marriage of the quantum world with General Relativity (example) is a work in progress.
    Only because eninstein believed that space/time were one thing. If you think of space as one thing and time as another then lots of the perspective riddles can be solved on all scales. Empty space having potential energy that creates time (quantum fluctuation) Held in check from the potential energy of a void or empty space. Only thing you can't have in the universe is nothing. and that in itself says something. JMO
    Reply
  • rod
    voidpotentialenergy said:
    Only because eninstein believed that space/time were one thing. If you think of space as one thing and time as another then lots of the perspective riddles can be solved on all scales. Empty space having potential energy that creates time (quantum fluctuation) Held in check from the potential energy of a void or empty space. Only thing you can't have in the universe is nothing. and that in itself says something. JMO

    Okay, back in January 2019, Sky & Telescope published their Sky Gazer's Almanac with celestial events predicted to view throughout 2019, the Mercury transit is a good example. Does your science lead to accurate predictions like this for the heliocentric solar system that telescope users like myself can observe and verify as true? A good theory in science must be testable - and falsifiable, otherwise the Earth is still immovable.
    Reply
  • voidpotentialenergy
    I'm not sure but i think you are asking about the relativity of mercury transiting the sun and it's offset time due to a gravity well? Relativity. With space and time as 2 entities and gravity as a local compression of quantum fluctuation (time) you get the same offset, but you also get the offset of living on a world that has it's quantum fluctuation slowed a very tiny amount. different perspective same conclusion, If gravity is simply an effect then it being felt across the universe instantly breaks no speed L laws . (Spooky action at a distance) as a time compression effect works well.As a particle entanglement very difficult to explain how 2 far flung particles can communicate faster than light.

    Hope that's was sort of what your question was?
    Reply
  • rod
    voidpotentialenergy said:
    I'm not sure but i think you are asking about the relativity of mercury transiting the sun and it's offset time due to a gravity well? Relativity. With space and time as 2 entities and gravity as a local compression of quantum fluctuation (time) you get the same offset, but you also get the offset of living on a world that has it's quantum fluctuation slowed a very tiny amount. different perspective same conclusion, If gravity is simply an effect then it being felt across the universe instantly breaks no speed L laws . (Spooky action at a distance) as a time compression effect works well.As a particle entanglement very difficult to explain how 2 far flung particles can communicate faster than light.

    Hope that's was sort of what your question was?

    No, I am thinking along the lines of Einstein General Relativity prediction of the motion of the perihelion of Mercury that was observed with telescopes, tested and verified as accurate and correct. The heliocentric solar system orbital mechanics and elliptical motion laws allow specific predictions to be made in astronomy for viewing and verification. So far - I do not observe quantum mechanics applied to the heliocentric solar system to make better and more accurate predictions like Einstein did for Newton's math concerning planetary orbits around the Sun like General Relativity did for Mercury. Astronomers had some difficulty with Mercury's orbit around the Sun based upon Newton - Einstein using General Relativity explained Mercury's motion better, astronomers tested, and found more accurate.
    Reply
  • voidpotentialenergy
    rod said:
    No, I am thinking along the lines of Einstein General Relativity prediction of the motion of the perihelion of Mercury that was observed with telescopes, tested and verified as accurate and correct. The heliocentric solar system orbital mechanics and elliptical motion laws allow specific predictions to be made in astronomy for viewing and verification. So far - I do not observe quantum mechanics applied to the heliocentric solar system to make better and more accurate predictions like Einstein did for Newton's math concerning planetary orbits around the Sun like General Relativity did for Mercury. Astronomers had some difficulty with Mercury's orbit around the Sun based upon Newton - Einstein using General Relativity explained Mercury's motion better, astronomers tested, and found more accurate.
    Space and time as 2 entities will give the exact same result as relativity.
    Relativity though can't explain what time is other than a gravity well.
    With time and space as 2 entities it can explain why the universe started how it maintains itself and why relativity works.

    Only real difference is relativity says that time relative and gravity well speed alter that perspective.
    I think all 3 are different parts of the same thing (empty space) creates (time) quantum fluctuation balanced naturally with potential energy of a void.
    Gravity a compression of time (compression of quantum fluctuation)

    When i though experiment a conventional physics black hole it gets very messy and difficult to explain with singularities and unknowns.
    No real theory why a black hole simply doesn't shrink forever and become an infinite point of energy.

    With time, space and gravity all being different forms a black hole is simple time compression physics.
    Reply
  • rod
    In your model, you state, "Space and time as 2 entities will give the exact same result as relativity." What astronomers have tested your model and published the results of those tests using the heliocentric solar system and shown the model you describe provides equal or better results than what Einstein did for Mercury's orbit using General Relativity?
    Reply
  • voidpotentialenergy
    rod said:
    In your model, you state, "Space and time as 2 entities will give the exact same result as relativity." What astronomers have tested your model and published the results of those tests using the heliocentric solar system and shown the model you describe provides equal or better results than what Einstein did for Mercury's orbit using General Relativity?
    Darn work always getting in the way.

    No one has tested my prediction with space and time as 2 different entities.
    It probably doesn't need to be tested since it is using the exact same idea as relativity just with separated forces so the answer will be the same.

    Proof of the idea gets more more interesting with duality of wave and particles at the same time thought experiment.

    Conventional would say that things move through the universe as a particle and wave through space/time with some pretty odd math and jump to conclusion ideas.

    With 2 separate things, the wave is in time and the particle in space with no math puzzles.
    Reply
  • B Pramana
    Have anyone heard of "The Ultimate Unification Theory" or "Metascience"?
    Reply