The Quantum Theory that Connects the Entire Universe


SciShow is supported by Go to to get 20% off of an annual Premium subscription.

Quantum mechanics is weird and seems a bit…complicated. But understanding it can help us to understand the universe.

Hosted by: Hank Green

SciShow has a spinoff podcast! It’s called SciShow Tangents. Check it out at
Support SciShow by becoming a patron on Patreon:
Huge thanks go to the following Patreon supporters for helping us keep SciShow free for everyone forever:

Bill & Katie Scholl, Adam Brainard, Greg, Alex Hackman, Andrew Finley Brenan, Sam Lutfi, D.A. Noe, الخليفي سلطان, Piya Shedden, KatieMarie Magnone, Scott Satovsky Jr, Charles Southerland, Patrick D. Ashmore, charles george, Kevin Bealer, Chris Peters
Looking for SciShow elsewhere on the internet?

Image Sources:

100 comments on “The Quantum Theory that Connects the Entire Universe

  1. The Great Mechanized Ape on

    i call BS. this whole cat thing assumes that the observer of the box is the only one experiencing reality. if you put the cat in the box alive and it comes out alive, the objective reality is that it was never is any other state of being other than alive. it can't come back from the dead. we dont invoke majic or magic to explain physics. if you could ask the car what happened it would say it spent some time in a box and came back out. not that it it exsisted in limbo untill the lid came back off. these guys did too many drugs or im doing just the right amount. the obvious answer is we dont know what is really goig on with super positioning.

  2. MrFermiMr on

    Many of these so-called wired features of qm can be understood in a triple system diagram. Shrodinger cat: the cat is observer 1 (O1) and say the lab is (O2). O1 observes a radioactive decay, and is dead(D) or alive(A) depending on whether the atom has decayed. Then according to O2, the state of O1, denoted by |O1> = |D> + |A>, is a mixed state, a superposition. But in the system of O1 it must be a pure state. This is understood as the procedure of tracing out degrees of freedom: O1 is in a superposition, only because O2 does not have access to its real state. Similar properties should be case if O1 makes statements about O2, that is O1 will say O2 is in a kind of superposition, until it has a chance of interacting with it.

  3. The Sapien on

    One way to solve the puzzle of locality is to drop the idea that the moving present is objective. Our temporal sense does not allow the future to affect the past. However, everything in physics seems to suggest otherwise. We don't have a science that can distinguish between what is now and what is not now. So maybe it's just a point of view or frame of reference, thus missing information and not complete.

  4. Buck Starchaser on

    I understand that the layman's descriptions don't do justice to the amount of thought and experimentation that went into these theories. That said, it seems that quantum theories tend to jump to wild conclusions instead of looking deeper for the causes of the observed effects. For example, the concept of superposition seems to boil down to "I didn't know until I looked, but it's strange that I couldn't predict what I would see." That doesn't seem to require the object to be unusual when not observed, only that the experiment forces conditions that stop the object from doing it's own thing, like making it silly cold or isolating it.
    It's like taking the cat experiment and assuming its behavior when you try to cram it into a deathbox is its casual behavior, while completely neglecting your own causal behavior.
    From what I've heard, there's a situation where you can't find the location of an electron unless you stop it, but if you stop it, you can't find its energy state. Granted, I'm sure I'm missing something here because it seems pretty obvious what's going on. Time moves much more slowly for a massive object (such as a human-scale observer/machine), than it does for the electron. So, the tiny electron is unobservably fast at our scale, unless we take extraordinary efforts to put it in a box. But then it can't behave naturally. There, I just made the Schrodinger's Cat logical. If only I could turn that into research grants.

  5. Toraxa on

    So does this mean the answer to the old question "If a tree falls in the forest and nobody is around to hear it, does it make a sound?" is both yes and no?

  6. Enty Ropy on

    Physicists who make decisions are more like religious fanatics than scientists. There is no proof, so no reason for a decision. Reasoning based on what we would like to have, or our subjective perception is not science. Imo the many worlds interpretation describes the reality of time, and the copenhagen interpretation describes the reality of space. They both add up to a duality of reality, 2 different perspectives on the same thing.

  7. Jim Fortune on

    If there's a window in the box with the cat, and one observer can see into the box, and another observer can't, does the super-position only exist for the observer who can't see the cat? And what does it take to be an observer? Is a camera an observer? Is a microbe an observer? Is the cat an observer? What if instead of a cat, it's a person. Is the person an observer?

  8. Lukos0036 on

    What bugs me is the "Till you observe it" part of superposition. What is so special about having a sentient being see it happen? That implies we have some sort of power directly over the state of matter and that simply isn't the case. Superposition shouldn't exist because if a tree falls in the forest and no one is there to hear it, it still makes a sound. Hearing it doesn't make it real or unreal. Observing a particle should not have any influence at all on it's state. No one has yet to explain what is so special about the act of observation or just how it is supposed to define the nature of a thing. It sounds like voodoo silliness. I think if your conclusion sounds a bit too hand wavy and magic it is probably wrong and should be studied more carefully.

  9. Karl Houseknecht on

    We don't have to accept that cats are dead and alive. Depends wholly on who is the observer. In the experiment, it could be argued that the geiger counter is the observer, because it's observing the decay of the atom and knows whether or not that's happened.

  10. RazorbackPT on

    I'm not a physicist but having read the work of Sean Carrol, Max Tegmark and others I find it strange how the Copenhagen interpretation is still taken seriously today. I don't know much about Pilot Wave, the interpretation the physicists I mentioned subscribe to is Everett's many-worlds interpretation. I also think it makes the most sense.

  11. Miles Guilford on

    Nice video, one slight quibble…
    No sensible living Copenhagen advocates think the cat is in any sense both dead and alive, only pop science books would espouse that view, not physicists…the wave function would collapse at the measuring device. It's not that observation or measurement per se causes wave function collapse, it's certain interactions which cause the collapse, which happens with or without observation or measurement. Schrödinger agreed with this interpretation, the cat is reductio as absurdum of the "observation causes wave function collapse" view of some Copenhagen advocates, since, he argued, cats can't be both dead and alive at the same time.

  12. Willskull on

    It's all a lack of technology for the time being, it took like 70 years to prove that gravitational waves are real despite even Einstein's doubts humans could ever observe such minimalistic event and yet we did!

  13. Tom Morgan on

    I like the pilot-wave theory on a purely philosophical level. The idea that there’s something binding every single molecule in the universe, something intrinsic to the foundation of reality… that’s really nice to think about.

  14. Tyrandus on

    The Copenhagen interpretation is just stupid. It's more an exercise of the mind and psychology than common sense and empirical data.

    The cat isn't alive and dead at the same time. It's either alive, or it's dead. Period. The information is there even if it hasn't yet been observed.

  15. DiabloQFDB on

    Damn, I wrote a giant 10 point rebuttal to the kindergarten level take on quantum mechanics from this video and the continual popularization of irrelevant interpretations that have been outdated for 50-100 years, pointing out common misconceptions and everything.

    And forgot to do a backup before hitting "commit"! And got it got lost.

  16. Todd Brill on

    There is no logical reason you need to accept any postulation. If a theory doesn't make sense or jive with reality, its okay to question it and not accept it as truth. The whole point behind science is the search for truth in reality. Experiments are how we test our theories so that if a theory doesn't make sense, we can discard it, not accept it.

  17. AvangionQ on

    Can that pilot wave idea potentially be used for long distance communication? Would be useful for when humanity expands to the moon, mars, nearby asteroids, space stations, etc …


Leave a Reply

Your email address will not be published. Required fields are marked *