World Science Scholars

6.8 Relativity of Simultaneity

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    • Professor Brian Greene writes, “When I first learned about the relativity of simultaneity, it radically reshaped my basic understanding of reality. Now, decades later, I still find it to be an absolutely stunning fact about how time works. For those of you who have never encountered the relativity of simultaneity before, did you have the same reaction? And for those who have seen it before, does it still blow your mind? Is there any fact about physics that you consider stranger?”

    • Honestly when I first think I started to grasp a concept of quantum physics a few years ago, that changed the paradigm of my thought patterns perpetually.

    • This is indeed mind-blowing. I have read, that in some circumstances, two observers in different places can’t even agree which of two different events came first. This does sound a bit stranger. I think it is probably related to the information given in this section. Maybe I will understand more as I progress through the course.

    • This aspect of simultaneity is just comment sense, other aspects of simultaneity ????

    • Yes, it is a mind-shocking phenomenon.

    • Quantum mechanics is also stranger!

    • Yes this is absolutely mind blowing. Relativity in general. It’s really depicting how each human has a unique reality for them. And the fact that the past, present and future all exists suggests that the universe is designed specifically for the observer. It’s about us. Each of us can be thought of as essentially the center of the universe.

    • The things I find strange are the facts that I totally understand the relativity of simultaneity..That just blows my mind, time will never be the same again.

    • I can’t believe it!

    • To afirm the existence is something that requires to define what it is existence, not an easy philosofical statement. One thing is the reality for a human and another thing is what is it real.The word real is modern word not use before XVth century. The object independent of us, and the reality of that object for us, are different things, science try to know what the object is itself. Time is a reality for the humans, but is it a real object? a physical entity, or is it just space?
      At the end of this course I hope to understand if time is a phisical object or if it is just a compairaison of movements a concept created to be able to measure movements of objects. Since speep of light is a constant movement then we discover relativity of simultaneity.

    • A clip within the Pitfalls Module shows how everyone who is not moving relative to another will experience the same reality The problem with this is that NO TWO people have ever, or will ever experience exactly the same velocity within this universe.

      This is because everything is moving. The Earth is rotating, the Earth is rotating around the Sun, the Sun revolves around the galaxy, the galaxy itself is moving all the while the universe itself is expanding. Which actually means every single person on Earth experiences a unique reality in the way no two fingerprints are the same.

      And if you think standing still on Earth next to someone is moving the same velocity, think again. This diagram I created depicts the speed difference as every circumference of the Earth rotates at a different velocity. And on a larger scale, every circumference of the Milky Way is rotating at a different velocity.

      Seems, every person past, present and future will experience a unique experience of reality.

      You must be logged in to view attached files.
    • What is the time?

    • I don’t know

    • ?

    • Un fenomeno sorprendentemente contraintuitivo

    • Son temas muy sorprendentes, porque son fuera de lo común y que no estamos muy acostumbrados a tratarlos.

    • I still have problems to understand, even if I’ve already read about this subject before. Is not that easy to get rid of previous notions of how the universe works; we need to constantly rethink our understanding.

      • I agree with you. How do i perceive something like this? It’s incredible.

    • Interesting!

    • I did.

    • I think that it always blow my mind.

    • Yes, it is an exciting thing.

    • This truly blew my mind. Relative simulataneity is true and strange thing at the same time.

    • Yes it really did blow my mind this is the third time I am watching Professor Greene explaining about Relativity Of Simultaneity and still it is blows my mind. Quantum Mechanics is another branch of Physics that when I read about it blows my mind into a million pieces especially Quantum Entanglement.

    • My philosophy teacher teaches me the core concepts of the Theory of Special Relativity, Theory of General Relativity and Theory of Quantum mechanics. Being the student of mathematics, it was very astonishing for me to hear the concept of Theory of Special Relativity, at the first time. Initially, I thought that how can two observers observe same event on different time? It maybe there is going something wrong. I am still partially agreed with the Theory of Special Relativity.
      The reasons can be;
      Maybe our devices are inaccurate?
      Maybe it is not giving unique answer for different observers?
      Maybe the effect of Theory of Special Relativity is very small in our daily-life?
      Maybe something else? But I am trying my best to understand the core concept related to the Theory.

    • It still sounds weird that two observers disagree upon whether two events are simultaneous or not. If according to me, two events happen at the same time, then everyone will agree that they happen simultaneously, because we do not consider the finite time difference that comes with a finite speed limit (the speed of light).

    • If time began with the Big Bang and the expansion of the universe was with a speed equal to the speed of light (as nothing goes faster) than time was going very very slowly compared with today. This means that the universe could be much older than 14 billion years (one year with today’s length). It could also explain why we see the speed of the expansion of the universe increasing as we are looking in the past. This would mean that in reality the speed of the expansion of the universe is decreasing. Where did I go wrong?

    • I love that physics challenges us to think beyond what is obvious. The relativity of simultaneity goes to what we perceive as past, present and future. While I understand it and accept it, I’m not sure I really “get it”. The two slit experiments also blow my mind.

    • i was fascinated with Relativity since early high school days. Of course i was fascinated with something that i could not really understand. Since then i have done plenty of different things in my life and now that I am 53, i am happy to say that i feel the same tickle of joy when i study the subject anew.
      I thank you and Jim Simmons for offering us who are interested in Science as a hobby the possibility to visit such subjects with this interactive way.

    • Just something more, i dont know if my perspective is correct, but one can see the Treaty Signing event as follows:
      A person in the platform sees the future of the president of Forward Land, that is, the platform guy sees the FL president sining before the president actually signs
      And the same platform guy will see the past of the president of Backward Land because he sees the photons travel to the president before the latter signs the treaty.
      n the first case the platform guy and the FL President are approaching each other, at the second case the platform guy and the BL president are distancing each other away

    • I don’t Mr. Brian whether you are reading it or not but if we kick out light for our dependence and put something with less velocity than it, let’s say two balls indifferent direction with velocity 0.5c than their velocities should modify unlike light and shouldn’t both the observers see the event happening at same times? if you’re reading then please reply.

    • i LOVE relativaty

    • i was beyond blown away when i found about what the statement of relativity of simultaneity, but when it was explained with the correct assumption of the constancy of the speed of light, i realized that this actually made a lot of sense.

    • The fact that time is relative and can be different for different people, is an interesting concept. For me that raises lots of questions and also allows answering some questions.

    • strangeness of nature

    • Look simple but still perplexing

    • Let me define an action A which occurs only when action B and action C occurs simultaneously ( for eg. Let ball 1 falling on the rod at distance x from the centre be action B and ball 2 falling on the other end of the rod at distance x from the centre be action C and the rod being in equilibrium be action A ). As you explained that the notion of simultaneity is different for different frames of references, this also means that the particular action A might happen in one frame of reference and might not happen at all in another frame. How does special relativity explain this? You also mentioned a part where the alien sweeps into the human’s past or future. Let’s say the alien’s frame of reference sweeps into the human’s future and the action A does not happen at all in its frame. But it is quite possible that it might happen in the Human’s future when it eventually arrives at it right? How does special relativity explain this?

    • If in the Alien example, suppose the alien’s frame sweeps into the human’s past, then it should be able to affect the human’s past which eventually affects the human’s present right. How does special relativity explain this?

    • It’s still mind-blowing.

    • It blew my mind when I first encountered the relativity of simultaneity and it still does. However, what astounds me even more is quantum physics and the results of those experiments. For example, the wave-like properties of electrons.

    • What’s wonderful to me is that perspective is accorded a scientific respect and acknowledgement by being sewn into relativity

    • mind blowing. thankyou sir for taking this course in most effective manner for free

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