If You Don’t Understand Quantum Physics, Try This!

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If You Don’t Understand Quantum Physics, Try This!

If You Don’t Understand Quantum Physics, Try This!

Quantum physics has a mystique of being complicated
and hard to understand, in fact Richard Feynmann who won the Nobel prize for his work on quantum
electrodynamics said: “If you think you understand quantum physics, you don’t understand
quantum physics”. Which is kind of disheartening for us because if he didn’t understand it,
what chance do the rest of us have? Fortunately this quote is a little misleading.
We do in fact understand quantum physics really well, in fact it is arguably the most successful
scientific theory out there, and has let us invent technologies like computers, digital
cameras, LED screens, lasers and nuclear power plants. And you know, you don’t really want
to build a nuclear power plant if you don’t really understand how it works. So quantum physics is the part of physics
that describes the smallest things in our Universe: molecules, atoms, subatomic particles
thing like that. Things down there don’t quite work the same way that we are used to
up here. This is fascinating because you and everything around you is made from quantum
physics, and so this is really how the whole universe is actually working. I’ve drawn these protons, neutrons and electrons
as particles, but in quantum mechanics we really describe everything as waves. By the
way I’m using quantum physics and quantum mechanics interchangeably, they are the same
thing. So instead of an electron looking like this, it should look something like this.
This is called a wave-function. But this wave-function isn’t a real physical
wave like wave on water or a sounds wave. A quantum wave is an abstract mathematical
description. To get the real world properties like position or momentum of an electron we
have to do mathematical operations on this wave-function, so for the position we take
the amplitude and square it, which for this wave would look something like this. This
gives us a thing called a probability distribution which tells us that you are more likely to
find the electron here than here, and when we actually measure where the electron is,
an electron particle pops up somewhere within this area. So with quantum physics we don’t know anything
with infinite detail, we can only predict probabilities that things will happen, and
it looks like this is a fundamental feature of the Universe which was quite a departure
from the clockwork, deterministic universe in classical physics, the kind of thing Newton
derived. This wave-function model predicts what subatomic
particles will do incredibly well, but weirdly we’ve got no idea if this wave-function is
literally real or not. No one has ever seen a quantum wave because whenever we measure
an electron all we ever see is a point like electron particle. So there is like this hidden
quantum realm where the waves exist, and then the world we can see, which is where all the
waves have turned into particles. And the barrier between these is a measurement. We
say a measurement ‘collapses’ the wave function, but we don’t actually have any
physics to describe how the wave collapses. This is a gap in our knowledge that we have
dubbed the measurement problem, and this is one of the things that Feynmann was referring
to with his quote. Another confusing thing is how exactly to
picture an electron. It seems to be a wave until you measure it, and then it is a particle,
so what actually is it? This is known as particle-wave duality, and here is an example of it in action:
the famous double slit experiment. Imagine spraying a paintball gun at a wall
with two openings in it, you’d expect to see two columns of paint go through and hit
the wall behind. But if you shrink this all down to the size of electrons you see something
quite different. You can fire one electron at a time at the slits and they appear on
the back wall, but as they build up over time you get a whole pattern of stripes, instead
of just two bands, this pattern of stripes is called an interference pattern, something
you only see with waves. The idea is that it is the electron-wave that goes through
both slits at the same time, and then the waves from each slit overlap with each other,
and where the waves add together you have a high probability of the electron popping
up at the wall, but where the waves cancel out the probability is very low. So actually
on the back wall the highest probability of finding the electron is in the middle of the
slits, and then it goes down and up again, and down and up again and this is the interference
pattern. So when you fire one electron after another they follow this probability distribution
and this interference pattern starts building up, and that’s exactly what we see in experiments.
So this shows that electrons behave like waves in this experiment. A question is what actually happens to this
spread-out electron-wave when you do a measurement? It seems like it goes from this spread out
wave to this localised particle, but like I said, there’s nothing in quantum mechanics
that tells us how the wave-function collapses. And this is not only true for electrons, but
for everything in the Universe, so this double slit experiment has huge consequences for
our model of the Universe, and it was very surprising the first time it was done. Physicists
are still grappling with this question today and have come up with many interpretations
of quantum mechanics to try an explain these results, and explain how reality actually
works. Okay lets go back to the wave-function. Now
we can use this picture to explain other features of quantum physics that you may have heard
about. So this is just one possible wave-function
for an electron, but there are many others. Like this one for instance. This says that
the electron has a probability of being over here, and a probability of being over here,
and very little probability of being in the middle. This is perfectly allowable in quantum
physics and this is where the phrase ‘things can be in two places at once’ comes from.
This is known as superposition, which comes from the fact that this wave can be made by
adding, or superimposing these two waves. The word superposition just means the adding
together of waves and we already saw this in the double slit experiment, and is not
really a very special phenomenon. You can even see superposition by dropping two pebbles
into a pond where the ripples overlap. Now for entanglement. Let’s say two electron-waves
meet. Their waves interfere with each other and become mixed up. This means that mathematically
we now have one wave-function that describes everything about both electrons and they are
inextricably linked, even if they move far away from each other. A measurement on one
of the particles, like measuring if it is spin up or down is now correlated with a measurement
on the other, even if they move billions of miles away. Einstein was very uncomfortable
with this idea because if you measure one of the particles here you instantaneously
know what the other will be even if it is billions of miles away, and that’s got a sort
of whiff of faster than light communication, which is not allowed by the theory of relativity.
But it turns out you can’t actually use this to communicate information, because the
measurements give you random results, but the fact that they are correlated means that
somehow there is a link that stretches over that distance. This is called non-locality. Quantum tunnelling. Quantum tunnelling is
where particles have a probability of moving through barriers, essentially allowing things
like electrons to pass through walls. When a wave-function meets a barrier it decays
exponentially in the barrier, but if the barrier is narrow enough the wave-function will exist
on the other side meaning there is a probability of the particle being found there when a measurement
is made. In fact the only reason you are alive is because
of quantum tunnelling in the Sun which make the Sun shine. Protons normally repel each
other, but they have a small probability of quantum tunnelling into each other which is
what turns hydrogen into helium and releases fusion energy. All life on Earth exists because
of energy from the Sun, except for life around hydrothermal vents. Now on to the Heisenberg Uncertainty principle.
I said that the beginning that this wave-function contains all of the information like position
and momentum of the electron, we just have to do some maths on it. The position is given
by the amplitude, or height of the wave, and the momentum is given by the wavelength of
the wave. But for this specific wave the position gives
us a probability distribution, so we don’t know exactly where the electron is. Also there
is an uncertainty in the momentum because this wave is made of many different wavelengths. But we can reduce that uncertainty, let’s
have a wave that only has one wavelength, so a sine wave. Now we know the momentum exactly
because the wavelength has a single value, but look at the position. There is an equal
probability of the electron being found anywhere in the universe. Okay let’s do the opposite
let’s make a wave that has only got one position. Now we know exactly where the electron
is, but what is the wavelength of the wave? Now the wavelength is very uncertain. Basically
only a sine wave gives you a precise momentum, and any wave that isn’t a perfect sine wave,
you have to build out of multiple different sine waves, and each of those multiple different
sine waves has got a different wavelength, and hence you have a range of possible different
values of momentum for the particle. This is Heisenberg’s Uncertainty principle,
you can only know certain things precisely, but not everything. Either you have got a
definite value of momentum, and don’t know anything about position, or you know the position
very well, but don’t know anything about the momentum, or you are in some intermediate
state. And this isn’t a limit of our measuring apparatus, this is a fundamental property
of the Universe! And finally, where does the name ‘quantum’
come from. Well a quanta is a packet of something like a chunk of something, and one of the
first quantum effects people saw were atomic spectra which is where atoms give off light
with specific discrete energies. It works like this. Imagine a string that is tied at
both ends, like a guitar string. If you pluck it, only certain waves can exist because the
ends are tied down, in this situation we say that the wavelengths are quantised to certain
values. The same thing happens if you ties the ends
of the string together because the waves have to match up, they can only vibrate in certain
restricted ways. And this is what is happening to an electron in an atom. The electron-wave
is constrained by the atom and quantised to certain wavelengths, short wavelength have
high energy and long wavelengths have a lower energy. This is why the light emitted by an
atom looks like a barcode because each bar of light corresponds to an electron jumping
from a wave with a high energy to one with a lower energy, and at the same time emitting
a quantised photon of light when it does this. So the light from an atom is quantised to
discrete packets of energy. Okay so that’s all the basics of quantum
physics, here are some technical notes which aren’t essential to know, but pause the
screen now if you are interested in a little more mathematical detail. So to round up. In quantum physics objects
are described with wave-functions, but when we measure them, what we see are particles,
so this leads to particle-wave duality, and also the measurement problem. And the consequence
of these wave-functions are the quantum phenomena of superposition, entanglement, quantum tunnelling,
the Heisenberg uncertainty principle and energy quantisation. So if you understand these things
you have got a good basic understanding of quantum physics. Despite its reputation I think quantum mechanics
isn’t too difficult for most people to get the basics of what is going on. In the past
I have relied upon analogies to try an explain it, but here I have just described what is
actually going on which I think might be more helpful. But if you have more questions I’ll
be on the comments below so ask away. For me the weird thing about quantum physics
is that on the one hand it is incredibly accurate and predictive but also it has got giant holes
in it like the measurement problem which we just don’t understand. So we can wonder,
will we ever actually understand quantum physics, or is it just too abstract for our human brains
to comprehend. Well I hope this video has helped you understand a little more about
how quantum physics works. And thanks to the sponsor of this video brillaint.org,
who have just launched their daily problems which you can dip into if you have a spare
5 minutes each day. Each problem teaches you some interesting facts that you can then use
to solve the problem. And if you enjoy that specific problem there are links to more on
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if you are confused and need more guidance, then you can join with the community discussions.
So this is a simple, fun way to keep learning more. If that sounds interesting go to brilliant
dot org slash dos or click on the link in the description below, and the first 200 to
do so will get 20% off the annual subscription which unlocks all of their premium content. Well that’s it from me, thanks for watching
and I’ll see you next time.

100 thoughts on If You Don’t Understand Quantum Physics, Try This!

  1. This video made way more sense than most attempts at explaining QM. You avoided saying logical nonsense like 'On and off and the same time.' Thanks.

  2. so the entanglement of M&M's being made together and individually packaged, could be the same if one pack went to Mars, and the other pack went to New York, Brilliant…! Do they weigh the same when eaten at their destination?….And is one package fresher than the other? [email protected]

  3. when observers view a wave it turns into a partial due to the act of observation creates or the observer are just seeing were that particle is on the p-brain. So you are really measuring the wave at the time you view that wave passing through a p-brain. I guess what I’m saying is the p-brain is the time position of the wave when observed

  4. Now I understand quantum physics.
    Physics has been quantisied to its shit.
    Working in wave form but outcome as a particle shit…..

  5. life is frequencies.
    we see these frequencies
    in their densest forms.

    everything is sound.
    light is frequency.

    life is pretty much vibrations.

    we are just a vibe.

  6. As with any field of study, the student needs time to learn the language first. Words like "wave function" and "sine wave" can make most people give up just as they're starting. Repetitively hearing and reading the language is crucial.

  7. My take on this as a non-science person is that anything can happen at any time (the uncertainty principle). Accept all perceptions as they occur. Don't get freaked out by them as they ARE (exist), at least in that moment.

  8. Only interested to know (1) what is QM/QP or quantum coefficient and (2) what is this for and (3) how are they used to do (2). QM is quanta, understanding nature or properties of wave/ electron behavior etc. = OK. With this understanding, we can make laser, LED, computers, nuclear plant and jelly beans. Sorry I made the last one up, but OK too! I couldn't get no.3 objective accomplished here, sad sad. Say as a scientist I understand how does an electron behave–so how does this behavior understanding is used to make LED, etc.????

  9. They say that only subatomic particles work on quantum laws so that we people who don't have special lab equipment and funding can not check for ourselves and confirm these pathetic ideas. People agree with this theory to look smart, yet they are dumb because they do not question the system and don't test it themselves.

  10. Great video! Now, how does quantum computing using quantum algorithms and qubits derive from this and actually work? Same level of explanation much appreciated!

  11. Complete bullshit. Quantum mechanics is based on field theory, which is infamous for being the vaguest theory on the planet, that also just happens to be the most efficient and widely applicable theory we have. Classical analog circuitry can be anywhere from 10,000-100,000x faster and more efficient than digital, and even taken up less space, because dualistic logics are not efficient and nature demands greater efficiency, with quantum systems sometimes being over 100% efficient. The less classical our descriptions of nature become, the faster and more wildly efficient and creative, however, classical logic and causality provide the necessary error corrections and add more beauty and meaning.

  12. Quantum physics is fuzzy junk science, nothing to do with reality. It won’t be a foundation for future space travel or any practical use for mankind. It’s like the Big Bang; all theory, and a flimsy one at that.

  13. I am very confused because if a measurement is needed to collapse the wavefunction, then what about the Big Bang? There were no sentient beings back then…so who or what collapsed the wavefunction?

  14. It's just the wave length of small particles in the Universe with extra calculations…. Its used in quantam computers to "PREDICT" Super position which is something u can't predict with ur mind u can just guess it. Ex: if you flip a coin and try to guess if it falls as heads or tails and sometimes it works but its kind of
    A fluke to really predict it we use quantam computers….. In such computers u can't use binary ( i.e 0s and 1s) but in quantam computers we use cubits

    And I m 12 so catch up

  15. would you give a lecture on the infinity – eternity? people go entirely through life never thinking about this conundrum Thanks.

  16. How is this interpretation of Quantum physics used to build a faster computer?
    Apparently IBM have made use of Quantum physics to produce 100-1000 times faster computer – where is the replacement of Digital bits and Qbits – completely above my head.

  17. You mention quantum entaglement cannot be used for communication because measurements results are random. Can the fact that a measurement occured be used to relay information? For example, measuring once in a second a 0 and twice a second a 1.

  18. Quantum entanglement can be understood in a way which does not violate the theory of relativity if you consider that the two remote particles are " connected " through some sort of medium where information passes between them instantaneously. Relativity just says that no " material " object can travel at the speed of light and this is not violated if we talk about INFORMATION being transmitted faster than light.

    By the way, being a trial lawyer and an amateur " theoretical " physicist, which means I can BULLSHIT with the rest of them and speculate to my heart's content as long as I back it up with some sort of foundation, I wrote an article a few years ago proposing to challenge the limitation on the speed of light imposed by Einstein which I called EINSTEIN WAS WRONG.

    The premise was to take EINSTEIN to court to challenge this speed limit and indicate which evidence and what proof would I cite to make my case.

    My first argument was that the mathematics that EINSTEIN used to support his limit on the speed of light was a flawed application of the LORENZ TRANSFORMATION EQUATIONS and the mathematical RULE which EINSTEIN used to mis-represent its meaning, as follows;

    – EINSTEIN uses the mass transformation equations in a self serving , circular and truly a philosophical manner. As all you physicists know, in that equation, when the speed of an object reaches the speed of light the equation resolves into a having a radical in the denominator which is the SQUARE ROOT of ZERO. EINSTEIN then makes the conclusion that a ZERO in a denominator equals INFINITY and that since infinite mass is impossible…therefor no material object can reach the speed of light.

    The problem with this is that a ZERO in a denominator is NOT necessarily infinity. This is NOT a math law, but a " theory " and many mathematicians do not agree with it.

    Secondly, even a layman would consider it to be illogical that an object can travel to 99.000000000% of the speed of light but that there is an INVISIBLE WALL which prevents it from going that extra 0.0000000001% . This intuitively makes NO SENSE.

    – Then I cited the numerous experiments which have observed supra-luminal phenomena over and over, recently adding TESLA to that list…the man EINSTEIN called the " smartest man in the world " and who actually conducted experiments where he observed these phenomena.

    – In addition to those studies I also refer to the classic TUNNEL EXPERIMENT where a beam of light is split in two where one beam travels to a target in a vacuum and the other travels through a chamber filled with CESIUM gas to slow it down. The counter intuitive result is that the obstructed beam consistently WINS the race, meaning it is traveling faster than " C " and more interestingly, that the beam in that chamber seems to EXIT the device BEFORE it enters !

    If you are not compromised by the prejudices of conventional wisdom you will come to logical conclusion which I have proposed for several years and which is an ALTERNATIVE theory to the theory on the limit of the speed of light and which states that ;


    This explains why the Cesium obstructed beam still wins the race because it has been slowed down but not completely and the INVISIBLE part did enter before , so it explains why it seems to exit before it enters because we could not see the INVISIBLE portion when it entered .

    If in fact there are portions of light which are invisible and travel faster than " C " it would explain many of the unresolved mysteries of physics such as the DUAL NATURE OF LIGHT and QUANTUM ENTANGLEMENT. It would also tell us, as BURBIDGE hypothesized, that the RED SHIFT is mis-calculated and the Universe is really much SMALLER than what we think.

    I challenge all of you " theoretical " physicists to contemplate this alternative theory and see if you can put some meat on this skeleton of my theory

  19. Which book or books or online materials, in your opinion, are the best resources that explain quantum mechanics from the ground up?

  20. Who is Niels Bohr to tell Einstein to stop telling God what to do? And who is God to tell Niels Bohr to tell Einstein not to tell God what to do? And who is Einstein to disapprove of the cabal of Niels Bohr and God who between them created a discernible but unintelligible foundation for reality, eh? That! is the questions.

  21. What a bunch of double talk! The earth is not a spinning ball as many nut jobs want us to believe! We are not random!

  22. Sir I have some questions :-
    1. Does quantam physics apply to all electrons and protons and even to those of our body?
    2. Do all of them show the property of superposition and tunneling and does uncertainty principle apply to all? If yes then how do we even exist?

  23. One thing i don’t understand and this is for me to

    If we learn the thing in school
    Why does it go below a b
    If we learn it we know it
    But when we test it
    We fail it

  24. So if we have something that can calculate the electron's momentum and location precisely at the same time in almost no time at all then we can predict the future isn't it?

  25. This proves we don't really exist unless anti matter is void of varying degrees within our grasp of reality enveloped on the outside of our cerebrospinal electromagnetic discharge. Kapeesh

  26. Thank you. It was explained pretty good. Can you do a video on the Quantum Computing and how these concepts are transferred to the domain of Computer Science. That would be great.

  27. Since one of my reletives told me"you phsically look very well, how couldn't you pass on physics lesson" İ haven't studied physics.😂😂😂

  28. Can’t the measurement barrier be how the ozone layer is collapsing a way of showing the particles that formed are breaking apart and then meteors hit up eventually reducing us back to nothing and going back into the flow of time? Jk I don’t get it

  29. The fact of quantum mechanics is that it suggests there is a brilliant mind behind everything we cannot really get ahold of.

  30. Quantum physics is like a moron trying to explain to you how dumb he is but he can't because he is dumb or someone who takes a B line around the world to get to his friend's house across the street. If you don't get it, that means you're smart. Let the idiot rot in his little web of lies. Just remember at its roots Quantum Physics means… Many things… yeah… you study many things… ok… So many things you ran out of shit to study so you started making shit up? Please…. explain to me how big infinity is, then convince me you can grasp its size and I can't because I am dumb then prove it to me even though you can't because I am dumb. All you're doing is saying that what you think is true is absolute and anyone who doesn't agree with you is too stupid to understand. Math is so simple you had to find a way to convince yourself and others you are God and know everything. But you don't. You don't know anything. You have produced nothing and have proven nothing. Can you prove nothing exists? That's what I thought. If you think what I wrote is wrong or bullshit, its simply because you are too stupid to understand. You are not a word wizard as I am. I know all. And all is all…

  31. Today we can learn everything we want from Internet. Governmental traditional education is running out of time and the old system will die. A new global civilisation will be arise soon! Peace & Love.

  32. Everyone who wants to make some sense of quantum mechanics must know from the beginning that (a) physicists do not know yet why it works; (b) there are DIFFERENT interpretations of it – so whoever tells you "I KNOW" – is a lair. https://www.cognisity.how/2019/10/entanglement.html

  33. I have a question, and don't know where else to ask it. It may be a stupid one, so forgive my ignorance, if it is.

    At what size does quantum physics give way to Newtonian physics?

    In other words, the super-small acts different than the things we're used to in everyday life. If you start blowing up the size of those super-small things, at what size would they "switch over'' from behaving like they do at the quantum level to what we see/know as the familiar way things are at our size?
    Is that known? Is it even knowable?
    Or am I just dumb, and asking asinine questions?

  34. It is easier to understand quantum physics being blinded, it reduces the amount of debranching stupid questions in human beings.

  35. At 2.57 – Our world just sees the quantum world side on.
    Great video thanks, will work through it with the children.. obviously I will watch it a few times first!!

  36. After watching this, I made a hot cup of coffee and went outside with it. Comfortably, I rested upon a wooden bench where I could feel the warm sunlight. I sipped and I pondered, for nearly an hour after the coffee was gone. "Interesting" I concluded to myself. Earl Nightengale figured it out. It really is, The Strangest Secret (although it's not actually a secret nor is it strange, it's the way things are).

  37. So the sun must be faster than light if the light that comes from it are lightspeed , so planets must be faster than light too , in my mind anyway lol i think we are static and all stars are going around us , as time lapse camera's show, a circle of stars above earth going round and round , i also think because of gravity we see things differently?

  38. Actually we are just a complex form of nothingness, we should not exist because when the big bang happened billions of years ago, matter and antimatter should cancel each other, but because of some unknown factor, in every billion of times matter and antimatter cancel each other, there is more matter that remains. And that is we the universe. Actually the universe is equal to 0

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