Science Simplified 4 All
Simple Explanation of the Most Notorious Experiment | Double Slit and Delayed Choice Quantum Eraser
This is not science fiction. This is real experimental physics.
In this video, we break down the most mind-bending experiment ever done in science — the Delayed Choice Quantum Eraser — in simple, clear language. No complex equations. No intimidating jargon. Just pure, mind-blowing reality.
We begin with the famous Double Slit Experiment, trace its evolution through single-particle interference, and finally dive into the baffling world of quantum entanglement, coincidence counting, and the experiment that some believe… broke time.
Did this experiment really prove retrocausality? Or is the truth even stranger?
Even Einstein struggled with these ideas. He called it “spooky action at a distance.” But the experiments that followed seem to confirm exactly what he couldn’t accept.
0:00 – Intro
02:22 – History Of Light
03:25 – Double Slit Experiment
05:44 – Explanation Of Double Slit Experiment
08:47 – History Of Light Continues
10:49 – Double Slit Experiment with Electron
11:31 – Single Particle Double Slit Experiment
13:36 – Which Way Experiment
15:40 – Using Entangled Photons and New Experiment Setup
17:56 – Delayed Choice Experiment
19:53 – The Delayed Choice Quantum Eraser Experiment.
🎥 If you’ve ever wondered why scientists say reality itself is weird, this video is your gateway.
🎯 By the end, you’ll never look at the world — or time — the same way again.
🧠 No knowledge is small. And some knowledge might just break your understanding of reality.
👇 WATCH TILL THE END to witness the experiment that still shocks physicists today.
⚠️ UPDATE October 2025:
Recently, PBS Space Time released a new video discussing the same experiment, featuring quantum physicist Mithuna Yoganathan.
In my video, I had clearly mentioned that even though this setup may appear to show retro causality — where the future seems to affect the past — it should not be treated as proof of it, and retro causality should be ruled out.
The new PBS Space Time explanation explores in more depth *why* retro causality should be ruled out.
Both videos complement each other and together help viewers understand the ongoing debate around the quantum eraser interpretation in modern quantum mechanics.
Watch their perspective here: https://youtu.be/sc7FlWUAnzA
This video explores whether future measurements can influence past events through the quantum eraser setup. We examine which-way information, causal ordering, and the role of post-processing in understanding these results. The debate continues: Does Alice’s measurement choice affect Bob’s earlier photon behavior, or does quantum superposition explain everything without backwards causation?
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You are welcome to my science channel Science Simplified 4 All. My name is Anoop. I am a science enthusiast. My science talk videos are an attempt to simplify complicated science topics so that everyone can understand. My videos will include topics like Physics, Astrophysics, Astronomy, Blackholes, Special Theory of relativity, General Theory of relativity, Spacetime, stars, quantum mechanics, science experiments, science projects, biology, aliens, science facts, science documentry etc. I will try to explain science in simple ways without too much equations, formulas and graphs. Some of my videos may be useful for the science students, science class, science master, and competitive exam students like UPSC etc.
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Time is just a human made illusion.
God knows everything.
It simple truth explains everything, from electrons to Cosmos..
Both are watched soon or later. Stop deciving people.
To look at something is to be connected to it. The image is in your mind. Consciousness is pattern recognition via electro magnetic frequencies. Our electro magnetic signature when observing something by the very act of being connected causes harmonic frequencies. Thus the electron behaves to match the tune. So it is and isnt aware depending on how you want to define it.
This came with amusement. I have been reading about Artificial electrons by prof Balungi Francis. He writes, they do because artificial electrons do more.
14:50 Why don't they just use a new photo plat for each particle and then overlay them? That way they know exactly which particle did what.
And how do we know that the half-silvered mirrors really let through random photons? Could it not be that the "wave photons "go through and the "particle photons" don't?
You NEVER can guarantee you shots one electron at once.
At this level of current an individual electron has a bizarre behavior like travel as fish cardumen, with sync vibration.
It's because God created it, and He creates amazing things. But people keep trying not to give Him the credit for some reason.
Ok act nonchalant their watching us
Particles think that they are sooo big, but they really aren't.
You first presumption is that it's lifeless…maybe you wanna reconsider
mind-bogging! The universe is just making fun of us 🙂
I’ve a suggestion probably never been given:
All scientists not only leave the premises they shouldn’t even be thinking about the experiment being run inside. Now let the “janitor etc.” invite a “totally non-scientific person” who has no clue about such science and wasn’t even told or heard about this experiment or its issues to run the test she must be completely oblivious and unable to assume any outcome. Because it was claimed that the observer is part of the experiment by these scientists may also means the observer’s thoughts and assumptions affecting the result. Give it a try please! ☝️👌
** Sorry, but you never gave the reason or solve the problem either! Instead It’s just a narration of old results.
Photons laughing at us
From all that has been said so far, the conclusion is that reality itself does not exist, but is a product of our consciousness. We are not external observers of the reality around us, but fully integrated participants in the matrix created by God's providence, which interacts with our consciousness. The fact that consciousness is an integral part of "external reality" explains why a magician is able to pull a rabbit out of his hat. When Christ stands before Pontius Pilate for questioning, he says "I have come to bear witness to the truth", Pilate answers him with the rhetorical question "What is truth?". The illusory nature of the world is clearly a topic that has occupied people for a long time.
Perhaps before we try to understand the effects of 'watching' we need to establish what this watching actually is. Is it a visible watching or sensing of electric or magnetic fields or is it some other way of 'seeing' what happens. When scientists tell us how they actually watch we might be a bit more informed about what is going on.
The electron is consciousness in superposition waiting for an observer to collapse the wave function into a particle. No past no future only ever present moments waiting to happen. No observer no particles …no self no universe
I like to experiment it in real time but I am facing difficulty in doing so other than laseer light experiment for interference pattern 😢
Bro….why is there no love experiment showing this experiment?
So, basically what you are saying is we change our behavior when someone is watching us (there is a camera) 😂
If either result wasn't watched or recorded, how do they know the result?
Has the experiment been done in a vacuum. Perhaps the existing light is affecting the light your orojecting through the slits.
Laurence Doyle – a Christian Science lecturer who also works for NASA already talks about this and explains it well to students – just search his name
So, electrons behave differently when observed, if so then C and D in last experiment would not give interference pattern because it was observed regardless if it was random or not, and not just that if electron would know it will be observed like A and B detectors why does it matter which detector will observe it, it should know the future that it will be observed hence behave as a particle not wave (interference pattern).
Which means electron doesn't know it is being observed if we use quantum eraser experiment or something else is happening. Unless this mirror is interfering with electron, maybe they did the experiment idk, but they should put C and D directly begind A and B mirror so when electron passes through A or B mirror it gets instantly recorded on C or D so basically we still have information from where electron came from but that will tell us does mirror through which electron passes is interfering with electron maybe changing it somehow, maybe making it think its not observed.
When we record what it does it shows what’s possible. Yeah that’s because all it does you clowns. It doesn’t do anything else
This is the best video I have seen explaining double slit experiment and future-past causality. In more than 25 years, no one has covered this topic so completely n chronologically like u. Thanks 👍🏽
Yeah but the electron could go back in time and change it's outcome e while in Super position based on the observation. Also, how does it know when it's being observed by the instrument in which observed it in the first place (secondary observation). It knows WHEN a conscious being is going to observe the instrument that initially observed it. So basically it's operating in past, present, AND future while in super position, it's remarkable!!
Finally, a simple explanation
Thank you
great explanation, my first time truly understanding the mystery ….
Thank you! Very nice video!