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If I was to look up, would I be looking at light from the past? If i was to travel there and look at earth would i be looking in the past?

Sort of like a paradox question that questions the perception of time. Every human interpenetrates time differently but measures it the same around the world. We use the Gregorian Calender and it is widely excepted that there are 365 days in a year and 24 hours in a day and so on. If I was to look up I would be looking into the past because it takes so long for light to reach earth. So if i was to look at earth from a far star or planet, would i be looking into the past? And yes it does make it a different question depending on how fast you travel to that far star or planet.

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    Aug 29 2012: Yes...but remember that "past' and "present" are relative to the observer. A different way of considering your question would be, "If there were two different observers on planets on opposite sides of the (galaxy, Universe, etc) looking back at each other, what would they each see?"

    Each observer would see their OWN "present" right next to them, but the "past" of the other observer because of the time it takes the "present" light from each observer to travel to the other observer. Each observer would currently be seeing the other's "past light" that left the planet the other observer was on in the other observer's "past".

    Are you asking if you could theoretically see your OWN past if you managed to travel away from your own planet faster than the speed of light?
    • Aug 29 2012: I was more or less trying to describe the first revised scenario that you said. So if time is only relevant to the observer how do we agree on a universal time?
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        Aug 30 2012: There is no universal time. What you refer to is a man-made construct. We invented clocks. We divided the days into hours, minutes, seconds, and now nan-seconds. But time is EXPERIENCED differently in different places. Someone on Mt. Everest experiences time differently than someone on a boat in the North Sea and differently. That's because the top of Mt. Everest has to travel more miles in a day that the boat at sea level in the northern hemisphere has to travel. The equator has to travel about 24,000 miles more in a day than someone standing on the north pole.

        At the same time, there is gravity that affects time. Take a sky scraper. Those on the bottom floor experience time differently than those on the top.

        But, commerce is well-served by a universal time construct. Time zones, for instance, were "invented" when the railroad companies need to create their time schedules. They are a very recent thing. Time is not as important for many other cultures.
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        Aug 30 2012: There is no universal time. What you refer to is a man-made construct. We invented clocks. We divided the days into hours, minutes, seconds, and now nano-seconds. But time is EXPERIENCED differently in different places. Someone on Mt. Everest experiences time differently than someone on a boat in the North Sea. That's because the top of Mt. Everest has to travel more miles in a day that the boat at sea level in the northern hemisphere. The equator has to travel about 24,000 miles more in a day than someone standing on the north pole.

        At the same time, there is gravity that affects time. Take a sky scraper. Those on the bottom floor experience time differently than those on the top.

        But, commerce is well-served by a universal time construct. Time zones, for instance, were "invented" when the railroad companies needed to create their time schedules. They are a very recent thing. When we began to move faster, the need for a common time understanding became important. Time is not as important for many other cultures.
        • Jon Ho

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          Aug 30 2012: Actually... there IS universal time. The whole universe experience the same time from the Big Bang until now, if you take the universe as a frame of reference. Like, Big Bang + 13 Zillion years, 2 months, and 3 days ago, I had lunch at Blue Lobster.

          Except... and this is where it gets tricky, that time can bend due to gravity, due to Gravitational Time Dilation. Which you so conveniently explained. ;)
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        Aug 30 2012: Jon Ho. Well, yes and no about the universal time. The singularity does not experience time like you do. Either there is no time or it experiences all times that ever will be in any context that can exist simultaneously. We really have no way of knowing which for sure. Time as we know it doesn't appear until space appears, and that happens after the expansion, not before it.

        If a spaceman had been part of a community that had been traveling at tremendous speeds for generations, then that community will be living in a much younger universe than you are, so your lunch date was relative to your position.
        • Aug 30 2012: Ok, how do we know that our time is the "correct" universal time after all humans have only experienced time on earth, i assume a body large enough to curve time, as mentioned by Jon Ho? wouldn't we have to find the center of the universe and measure time there somehow? Because we only measure from the light from our star because it's the closest.
        • Jon Ho

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          Sep 1 2012: I wasn't talking about the singularity, I was talking about AFTER the Big Bang. BIG difference. ;)

          And again, I agree about the second part, time IS space, space IS time. However... If a spaceman had been part of a community that had been traveling at tremendous speeds for generations, that community is STILL living in the SAME UNIVERSE. Only difference is due to TIME DILATION, they suffer(?) the effects of time slower.
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        Aug 31 2012: The only "corrrect" universal time is the moment of NOW - the source of your power. It is a moment that we all have in common, but it is an infinite concept. (How long is now? How far can you run in no time?) Beyond the abstract moment of now, (past & future) time is relevant to your position as observer, your trajectory, and your velocity. This is true for you, for a cell in your big toe, for a galaxy.

        Prior to the big expansion, all times probably existed IN THEIR POTENTIALS in an infinite moment of now., just as yours do. They only became realized (KNOWABLE) with the appearance of SpaceTime.

        As to measuring light: Someone, at some time, established a system of measurement. In the US, it's based on a foot. In the UK, it's based on a meter.

        Light travels at 186,282 miles per second or about 700 million miles per hour. It can also said to travel at 299,792,458 meters per hour. This is true for all light in our reality. However, it turns out the light's speed is farster, the farther away from its source it becomes. (an interesting factoid)

        We dont just measure light from our star. We measure light from the furthest reaches of the heavens. The diameter of the observable universe is 93 billion light years or 8.80×1026 metres. But remember, ours is probably not the only universe. It is more likely that we are more like 2 dimensional beings living in a 3 or more dimensional reality. Shouldn't this impact your notion of time?

        Little is known about time. I conceive of it as a multi-layered grid like framework and I navigate the grid like a ship captain navigates the oceans. But that is MY theory.
        • Jon Ho

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          Sep 1 2012: No, no, no!

          Well, maybe, if we are all still in the singularity, then yeah, I agree with you everything you said, that everything, past, present, and future, is NOW.

          After the Big Bang though, and with the introduction of Space-Time(TM), to say that everything happen in the NOW, the idea that all is one, with no thought of cause and effect, is well, just wrong. Why? Because what you are proposing is exactly what my friend Zeno proposed a couple of millenium ago. Check out "http://en.wikipedia.org/wiki/Zeno's_paradoxes"

          I LOVE your theory of time! Brilliant! Let me add more to it. Instead of just the oceans, try adding canals, rivers, lakes, whirlpool and eddies in the water, and rivers that bend back towards itself. ;)
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        Sep 1 2012: Another take on time. Let's take a photon and split it in half - sending each half down fiber optic cables at the speed of light. When the atom split, they became "entangled". They only appear to be two photons, but they are really more than two. The division is an illusion. How do I know that?

        Because when you split the photon in half, they had opposing spins. When one photon got to a point 14 miles away from the other (though it could have been across the universe), the spin of one was changed and the other SIMULTANEOUSLY (in no time) changed its spin accordingly. How did the information get from one to the other in zero time? It could only be if the separation was an illusion or if 2 photons exist in one dimension and a third in the next - which exists in a reality that does not have time. (Recently proved at CERN). (1+1=3+ in the quantum world)

        Well, using this principle, let's say that the entire potential universe existed as a singularity, but it suddenly split apart. In this analogy, then we are ALL one in at least one other dimension. From the position of the ultimate relationship, there is only one moment. It is "NOW", which is how information is transferred across the multiverse in zero time.

        Thus, the only uniform time that is true for ALL observers in any situation is NOW.
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      Sep 1 2012: Jon Ho -> No one suffers from time dilation. Here's an example. Let's say that two toddler twins were playing together in the back yard. A space ship lands. One of the toddlers, being curious, climbs aboard. The space ship then takes off, unaware that the child is aboard. They take of at 80% of the speed of light. When the aliens, being nice aliens, discover the child, they decide to return it to its own world, so they return and land in the back yard and let the child out. At that moment a 10 year old boy comes running out of the house. That 10 year old by is the toddler's twin. No one has experienced suffering due to time dilation, but I suspect that many suffered at the 8.5-year perceived loss of a young child.
      • Jon Ho

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        Sep 2 2012: That toddler who climbed aboard the space ship 'suffered' Time Dilation when he was accidentally taken from 3D into 4D. ;)

        If I was them aliens I would have returned the child at the exact moment the child boarded my ship in curiosity because:
        1) Travelling at 80% speed of light is extremely inefficient; I would be 90,000 years old if I were to go back to Alpha Centauri and
        2) Any aliens worth his salt would travel not just through Space but through Time as well. ;)
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          Sep 2 2012: Agreed, and I see that as our future, but this requires understanding time differently. And again, the multiverse theory and the universal moment of NOW seems the most likely avenue to that point. But we have taken the science as far as we can reasonably take it - given that there is no science that allows us to take it further.
          :-)
      • Jon Ho

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        Sep 2 2012: I'm unable to reply, can't find the reply button, silly TED programmers...

        but...

        People assume that time is a strict progression of cause to effect, but actually, from a non-linear non-subjective viewpoint, it's more like a big bowl of wibbly wobbly timey wimey... stuff. ;)

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