World Science Scholars

4.7 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?”

    • Yeah. It’s completely change my understanding about the behaviour of light.

    • What would happen if the same experiment occured using sounds waves instead? Imagine that the forward and backward presidents agreed to sign the agreement once they heard the sound of a horn that was placed at an equidistant point between them whilst on the train. Will the stationary observers agree that that event took place at the same moment?

    • yes because the speed of sound is relative to observer not an constant .

    • I think that, since the sound waves are transmitted through the air which itself is being carried by the train, the sound will hit the presidents at the same time in both frames of reference.

    • If the relativity of simultaneity is different for different people on the earth then what happens in space??? Is it different there too???

    • so basically it tells us relativity of simultaneity is relative to the vision/perspective of the person

    • yes thats right

    • wow thats right

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    • What if we have a laser gun at equidistant shooting them at the same time? (who will die first?)

    • Yes it still seems incredible to me… only thing stranger is when I think about the fact that an objects journey to the depth of a black hole is instantaneous but on hold for possibly billions of years for us.

    • It has changed the way I think

    • Yes sir, this behavior of time space and light is completely unimaginable. Your mind doesn’t want to accept it but it is truth, thanks sir providing such knowledge that basically taught in university

    • It’s very interesting to understand how time works differently ,according to the observations of different people

    • What intrigues me i that in this model a singular event is now accurately locked into history at two different time points. If we push the velocity of the train to very fast speeds we may have both Presidents agreeing that they signed at 12.00. But the observers are equally convinced that one signed at 11.59 and one signed at 12.01. The same universe now has historically accurate dates that differ, from which point in time future events may be measured, thereby propagating more differences, e.g. the ceremony of the signing reenactment every year. That’s just weird, but also cool.

    • Yes, it does blows my mind this fact. But for me even stranger is the fact that times stops at the singularity of a black hole.

    • Certainly, the constant speed of light has brought a different narrative to the way I see simultaneity

    • It is quite easy to grasp the mathematics of “relativity of simultaniety” but it is hard to imagine it in reality!!!

  • `4,7

  • Let us move on

  • Pleas let us move on

  • This changes the entire concept of occurrences, say, on the other side of the galaxy. To say what is observered is to ask when did it really happen? There are other relativistic effects such as extreme gravity (black holes) which have an extreme effect on reference. We probably wouldn’t be surprised if other relativistic effects where found. Bottom line: the universe is not what, where, or when it appears to be.

  • I feel happy we are far away from moving or travel at speeds close to the speed of light. It would be a totally different world/universe and we would need to understand time and events in a completely different way that what we have today. Syncing with events, objects and people at those speeds where all this relativity become evident would be that hard that we will need, at least, really special clocks to make it work.

  • Special Relativity is truly stunning, and shows the deep meaning of spacetime and some incredible effects, however I think that Quantum Teleportation is even stranger, that you can teleport the information of a Quantum system (with quantum entanglement) to in principle be able to recreate it .

  • When the math version of this course will come

  • Yes, something even stranger- the appearance of OU physics Lecturers in their pioneering 1970s tv broadcasts 🙂

  • Yeah! It completely made to feel amazed, that how a single constancy, the speed of the light, makes the whole act of simultaneity as relative and is respect to the state of motion of the observer. And, it also completely bashed the Newton’s mechanics at the ranges of lightspeed and his understanding of time as universally same to the statement,”TIME IS RELATIVE”

  • Yes! It made to feel amazed, that how a single constancy, the speed of the light, makes the whole act of simultaneity as relative and is respect to the state of motion of the observer. And, it also completely bashed the Newton’s mechanics at the ranges of lightspeed and his understanding of time as universally same to the statement,”TIME IS RELATIVE”

  • Yes, I have always thought of this notion that two persons playing ball on a moving bus, will there be any time difference in which they get the ball. Now, it’s clear to me.

  • I think light goes with logarithmically spaced vectors with respect to observer. But it’s an absolute constant.

  • It’s strange, at first I found it all a bit unremarkable…depressingly so. Even with the interactive demos showing the different points of view, it struck me as a kind of trivial. I have gradually changed my mind, though. I see now it was my own intellect and imagination that were unremarkable and just not quite ready. It was a subtle and slow process but one that keeps my mind in a constant state of wonder, now. It’s not easy at all for me to understand even the most basic principles involved here but I’m grateful for the opportunity to try. Fascinating!

  • When we are on train.

  • Yeah absolutely it blown my mind, there nothing wierd when it comes to science, almost a lot will feel weird on first and when we know that deep it just excites us

  • When I heard that the speed of light never changed, my mind rebelled. Then I realizing the frequency and therefore energy of a photon goes up linear with the momentum of a photon. Since the energy goes up with square of velocity only the mass and momentum are changing.
    If a moving observer crosses a stationary observer exactly when the stationary observer sees simultaneous lighting strikes, and doesn’t see simultaneous lighting strikes, my mind rebels.

  • Relative Simultaneity could be felt while under the influence of psychedelics. Deep states of meditation, such as sensory deprivation, also reach theta, lambda and epsilon brainwave states. Spend enough time in these states, and neural network rewiring could easily occur, as well as ageless intellectual maturity.

  • Yeah it is mesmerizing.

  • i have read in the theory of relativity too, the lightning example, but it never fails to blow my mind

  • I consider the intrinsic dark energy of space, as wels the idea of fundamental strings or membranes that exist in spatial dimensions other than the ordinary 3D space of our general perception, to be on a par with the relativity of simultaneity for ‘strangeness’.

  • I am graduate student now but I learned about special theory of relativity when I was in school now after 10 years I still wonder what is time? and why it slows down its weird fact that Dr. Brian Greene led me to some of the clearity through his books, his shows and this course.

  • I’ve seen it before, but it still intrigues me how light behaves.

  • I don’t understand why my answer in the previous exercise was wrong. Train is at rest, I am at the platform so at rest too, And the “correct” answer says there would be a time difference and the video claims that the train is moving with respect to me with -v? Why if we are both at rest??

  • Yes this sooo blows my mind… as i am wrapping my mind about what it means about reality…. just how?? Wow. But God! How? !!

  • I think my misunderstanding was due to not understanding the meaning of the word ‘strolling’. I thought the meaning was standing, but it means walking. Now clear 🙂

  • I think if I used 2 timers capable of measuring the small amount of time involved. Then those on the MOVING train would see they were wrong!

  • What would happen if the same experiment occurred using gravity waves instead?

  • When a theory or discovery challenges the natural way in which us humans think I believe that may lend to its credibility. When I first came across the relativity of simultaneity i thought it to be accurate but not so astounding because I have long thought that time is experienced at different rates to each individual and may even differ for each person several times in the space of a day. It is important to remember we are made of matter that interacts with many different forces and particles therefore our complete make up is in a state of constant fluctuation.

  • always blows my mind

  • So yeah, my observations so far:
    1. The speed of light cannot change irrespective of your speed.
    2. Relativity of Simultaneity explains the difference between the observer and receiver, also If you travel further against the speed of light it will take more time to reach you; it can be even 1/10000th of sec.

  • yes professor actually whole of Physics blows my mind. all empirical laws of gas,thermodynamics and kepler laws.when i learned that our universe is mechanical universe.IT IS OBEYING THE EQUATIONS.

  • Yes. This actually changed my outlook to this universe

  • Me also. I think that is the reason why “relativity of simultaneity” is so confusing.

  • Yes it still seems incredible to me… only thing stranger is when I think about the fact that an objects journey to the depth of a black hole is instantaneous but on hold for possibly billions of years for us.

  • Yes. Absolutely.

  • It completely blowed my mind…

  • It is still mindblowing, yes. But thanks god, we live such a slow (in terms of velocities of our actions) ife that it is not really confusing in an everyday life. But I’l tel you what is of equal “mindblow” factor for me. It’s the emptyness of microcosmos. Just imagine how tiny the particles are in terms of “size” how much emptyness is between them… It’s all actually transparent – all those buidings, cars, people…But then you switch on the interaction and add communication between those tiny particles and start rendering the objects ( all those buidings, cars people)

  • Interesting ways to explain. I feel it and understand it a little differently each time. It is a phenomenon that will still satisfy and force you to ask more questions.

  • Would the same thing occur if two balls were thrown at the ‘same speed’? The observers on the platform would obviously say the time taken to reach two equidistant destinations was different because the train is moving, but what about the people on the train? Would the ball be moving at the same speed from their perspective?

  • Is there any other facts of physics considered to be stranger?

    That is a difficult one.

    Holograms are not considered mainstream in NorthAm, nor is positive ion science. Black light is perhaps the strangest of things in physics.

    Whether two events at separate locations are simultaneous depends on the motion of the observer relative to the locations of the events.

    When encountering a paradox, there is usually a science to it. Motion as determining time is quirky.

  • love it all. it’s all exciting and interesting

  • The simultaneity realization hurts my brain but i am starting to accept it.

  • Yes, even though theoretically the concept that simulataneity is relative is familar, to be able to imagine or pre-empt (for want of a better word) its ramifications on the way we see and understand things is difficult to wrap one’s head around. Almost intimidating, actually.

  • The relativity of simultaneity is indeed a mind-blowing concept that challenges our intuitive understanding of time. When I first encountered it, I was astounded by how our perception of the order of events can be altered by our relative motion. Even though I am a high school graduate who is not as acquainted with this field as Dr. Greene, I can appreciate the profound implications of this principle.
    However, it’s important to note that what may seem strange or mind-boggling in physics is often a result of our limited human perspective. Over time, physics has made remarkable progress in unraveling the mysteries of the universe and providing us with a deeper understanding of how things work.
    As our knowledge of physics has expanded, many phenomena that once seemed strange or inexplicable have been explained and incorporated into our broader understanding of reality. Concepts like quantum mechanics and general relativity have provided us with powerful frameworks to explain the behavior of particles, the nature of gravity, and the dynamics of the universe.
    While there are still frontiers and unsolved mysteries in physics, such as the nature of dark matter and dark energy, these are areas where our understanding is still evolving. With each new discovery and breakthrough, the once-strange aspects of the universe are continuously demystified and incorporated into our scientific understanding.
    So, while the relativity of simultaneity can still elicit awe and wonder, it is essential to acknowledge that physics has come a long way in making sense of the reality we experience. The strangeness of physics is often a testament to the richness and complexity of the natural world, and our ongoing quest to unravel its secrets.

  • Yes. I consider this a life changing perspective actually when we started experimenting with the models I started thinking of every source of light I had from the lightbulb that was above me until massive light sources as the sun. Other question of physics that I would ask would how does light fuctions in a black hole or through a black hole.

  • Yes. I consider this a life changing perspective actually when we started experimenting with the models I started thinking of every source of light I had from the lightbulb that was above me until massive light sources as the sun. Other question of physics that I would ask would how does light functions in a black hole or through a black hole.

  • Yes. It’s interesting when our general ideas about time are challenged and we are faced with scientific facts. I also find that t8me moves in one direction only a fascinating concept and I hope to know why one day.

  • Yes I have encountered it before, to me the most surprising thing is that how experiment start from laboratory curiosity, like electric and magnetism, end up with Maxwell’s equations and then predicted the speed of light is constant. Then how scientist of the time struggled to stay stick with the common sense and invent the ether for them, instead of just believe the equations. Generally, is shows me how things are connected and the working principle of the universe is independent of our intuitive ideas.

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