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6.8 Relativity of Simultaneity
Discussion
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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?”
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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.
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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.
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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 http://youtu.be/HxH4pKLqUBY. 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.
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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.
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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).
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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?
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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.
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I’m not Brian, but it seems to me that if you used something slower it would exaggerate the effect instead of eliminating it. Say we use two people with even strides ( equal walking speeds ) and they walked to FL and BL this would allow the train to travel further during the signing, which would make it stretch out the time and make a longer interval between. What would make it seem closer is when we slow the train, slowing the train keeps both observers closer to the event. While speeding up the train widens the distance between observations. Which gives a longer relative gap between FL and BL.
Just a thought from an old retired coal miner. if I’m off sides let me know, John
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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?
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I was completely blown and it not only changed my understanding but reshaped me even as a person , realizing how much wrong doings in the world is meaningless as nothing is objectively true , we’re all here existing on the stage of time but yet we chose to hate each other. Also how whatever i experience has already happened from some other perspective and may be about to happen in some other perspective.
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It becomes plausible as you apply the math to show this is true. I only have a high school education, but the simple math explained how 2 different perspectives could still be true to each other. I followed along and did the math with you. Remarkable. I just want to learn more with the math to understand. Thank you.
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I am revisiting this course for a third time to try to embed the core concepts more firmly in my mind. I am in a similar position to Mr Talbot (but probably considerably older), and find the mathematical proofs and derivations very compelling. As for the final aspect of the initial question – learning that neuroscience teaches us that our perceptions are filtered not just by exposure to a limited spectrum, but also by a brain that has evolved to protect us from the dangers of exposure to reality, is not strange, but nevertheless very fascinating }:‑)
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I think we’re assuming some kind of homogeneity and anisotropy of the region of spacetime within which we make our observations about relativity of simultaneity. I’d question if these observations would change, and how exactly, in more complicated surroundings like, e.g. within the ergosphere or between the event horizons of a Kerr (rotating) black hole. Or even a charged hole maybe. Would the frame dragging effects somehow kick in and make the relativity of simultaneity effects get redistributed nonuniformly? And how exactly? This is probably one thing about physics that I might find stranger.
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During this section should have been stressed much more that, the relativity of simultaneity refers to measuring the moment when the events take place, not the way these events are really seeing by the eye of the observer. Namely, we are not taking into account the time that, after the event has “locally happened”, light takes to travel from this event to the eye of the observer. In fact, one observer in the train located at one of the wagon ends wouldn’t actually see them to sign at the same time either because the light would take more time to travel from the opposite end of the wagon. Nevertheless, he would still agree that both leaders had signed the treat simultaneously because for “measuring” the real moment when both events took place, he should take into account the delay of light to reach his eye (and this is the difference between measuring and seeing).
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I’ve been really struggling with the relativity of simultanety. As you have explained, it isn’t learned from our life experiences, it’s not terribly intuitive. Perhaps because of my advanced age (82), my life experiences have been baked into my head a llittle more intensely than others younger than me. But you are so convincing, I’m beginning to see the light. I have lots of daily time to ponder all of this, and I’m really excited to learn more.
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When technology allows for monitoring the relativity of simultaneity, this will eavesdrop on different times.
This is something that allows for a timing edge for those that need this.
Other concepts that are mindblowing are smaller brains being more intelligent, consciousness occuring on the cortex blanket, and dark matter influencing single galaxies but not multiple grouped galaxies.
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yes, it is mind-blowing. Every time I think about it feels strange, it seems amazing, it is wonderful how we are capable of figuring this out and understanding the fact. And just by speed of light being constant, how our perception of reality changes, how our understanding reach to another level ,it is beautiful.
yes, there are many things in physics that seems strange, and special theory of relativity is one of those.
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