186282.397 miles/second

[SpeedFreek]

Harmonicaman: Thanks. That makes sense to me if the westbound planes movement relative to the stationary clock was somewhat different to the eastbound plane. It seems there may be a gravitational effect too in this scenario.<br /><br />Aidan13791: I would suppose that, technically, even if the photon were able to observe us, it would observe nothing because the journey takes no time at all. It leaves the star and then hits the back of our eyeball in an instant (or is that less than an instant?). At best, it could only observe us for an infinitely small time, heh, so the amount it would see us age would be infinitely small? <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[aidan13791]

Thankyou, that was very helpful. <br />I have come to the conclusion that a photon, since time is non-existant to it, cannot observe outside influences affecting it, but can only feel the effects. Also, if we could see what happens in that instant that the photon can 'see' something, then we would just see whatever was in the direction that the photon was facing in the instant that it was produced (since photons are bosons, they can be produced en masse).

 

[SpeedFreek]

If time is does not exist to the photon in this scenario, and it cannot observe outside influences, how can it feel their effects?<br /><br />Of course, photons are bouncing around our universe and having lots of effects happen to them. But to the photon it all happens instantaneously. (I realise the irony of attributing things like observation and feeling to a photon, the one particle with the least chance of doing these things! <img src="/images/icons/wink.gif" />)<br /><br />I once heard a school of thought that, since everything is instantaneous to the photon, maybe there was, in reality, only ONE photon, but it was everywhere at once! <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>(seeing as when in an inertial frame, the dilation is symmetrical)<p><hr /></p></p></blockquote> <br />to confuse you more, there is no 'symmetrical time dilation', that is such that it would result in perceivable changes - like slowed down aging when I didn't go travel on rocket someplace and simply stayed put down on Earth<br /><br />I mean, what the hell do I care if somebody went on a journey to a star or not, if he did, he might very well call me back over a radio and tell me - "I am now crusing at constant velocity near the speed of light towards Alpha Centauri and so I am in an inertial frame and can consider myself at rest with you on Earth moving away from me at constant velocity and I can see you moving slow, age slow:... and I could radio him back to stuff it, that I age the same way as I ever did, thank you very much... ROFL<br /><br />it is nice to talk about inertial frames but only untill the time comes and the cow should be butchered LOL that is untill we have to start to consider the real world experimental facts because then things get messy (I mean if all these things were nice and square, there wouldn't be any controversy over this issue)<br /><br />why the hell should I all of a sudden start aging slower now after all those years I lived just because some crackpot decided now to fly off someplace? <br /><br />yet the fact remains that the time dilation with real lasting physical effects does in fact result from travel at constant speed and those effects do show up only on the one who went to travel, not on the one who stayed home, never mind the inertial frames in which things are supposed to be symmetrical (I told you I am gonna confuse you)<br /><br />those planes with clocks aboard were flown East and West around the world partly to eliminate the gravitational and acceleration factors - clocks on both planes suffered the same acceleration conditions and only difference was that one went around the Earth on <div class="Discussion_UserSignature"> </div>

 

[aidan13791]

Speedfreek: I once heard a school of thought that, since everything is instantaneous to the photon, maybe there was, in reality, only ONE photon, but it was everywhere at once! <br /><br />Possibly, that would fit in with the Superposition principle and maybe the Copenhagen Interpretation of Quantum Mechanics, but then, why are masses of photons produced every time we switch on a lightbulb?

 

[SpeedFreek]

vanDivX: So it seems that the jury is still out on this one then? Any age difference cannot happen just during acceleration or deceleration (if the time difference on the airplanes gets bigger, the longer they fly at constant speed) but also, the difference cannot just happen during constant speed (if there is time dilation on a relativistic journey when there is no constant speed, just acceleration and deceleration). Nice one. Now my head hurts! <img src="/images/icons/wink.gif" /><br /><br />Aidan13791: Are lots of photons produced when we switch a lightbulb on? Or is it just the one photon, but seen everywhere at once? Heheh sorry I think I am just being silly now.<br /><br />Anyway, thanks for all your help guys!<br /><br />Although this thread as deviated somewhat from its original topic, it still shows that at speeds close to the speed of light, it wouldn't necessarily take too long for someone to travel to the stars and back. Just don't bother waiting up for them! <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[aidan13791]

It actually makes more sense than you think. Obviously, there are many photons, but some of them are actually in two places at once. This is because some of them are in an entangled state, (read something on quantum entanglement). Also, they are all part of a superposition, which is another way of them being in two places at once. They are all in many places at once due to the fact that they are in a wavefunction, but once we measure or observe them, the wavefunction 'collapses', forcing the photon to assume one of those places. This is supported by the double slit experiment. It is also covered in the book 'in search of Schrodingers cat', if you have ever read it.

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>So it seems that the jury is still out on this one then? Any age difference cannot happen just during acceleration or deceleration (if the time difference on the airplanes gets bigger, the longer they fly at constant speed) but also, the difference cannot just happen during constant speed (if there is time dilation on a relativistic journey when there is no constant speed, just acceleration and deceleration). Nice one. Now my head hurts! <p><hr /></p></p></blockquote>well, no jury is out on this, what I say here comes from me (don't know that anybody at all puts it like I just did but then again I don't watch what goes on much) and I wouldn't count my view as some jury by no means, there is no official position on this, these days its mainly disenting views on forums on net from people that sense something is not right there and either defend the standard accepted view or choose the acceleration as disenting view (or perhaps reject such real effect like aging difference altogether or whatever)<br /><br />its like this, age difference happens during both acceleration and constant speed travel, clocks in stronger gravitational field tick slower and we age slower than in relatively weaker gravitational field and accelerated clocks tick slower and we age slower if we are suffering acceleration than when at rest (acceleration is really just gravitation)<br /><br />you could also travel to stars and accelerate all the time (which is possible since you can accelerate all you want and you will never get to speed of light anyway) but the point is that this time dilation with real effects also happens during travel at constant velocity, theory says so and experiments confirm it<br /><br />and that is where conundrum lies, inertial reference frames are supposed to yield symmetrical effects, they are just expression of relativity of things, I can say your clock tick slower while you move and you can say that from your viewpoint it is m <div class="Discussion_UserSignature"> </div>

 

[nojocujo]

I should say that the jury is out.....It should be depentdent upon the gravitational energy density as to whether there is a time dilation or a time contraction...... theorectically speaking. I don't like attributing a spacetime acceleration/deceleration to gravity but current physics GR does so I am suspect or my views are. Gravitaional acceleration/deceleration should be separated from a spacetime acceleration/deceleration. It would clean up GR.

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>the nearest star is 4.3 light years away and we're not even close to light speed yet, one day we might be. and even if we are, we will take decaades to get to other stars. so my questions are:<br />do you think we will ever reach another star?<br />why can't matter go faster than light (or if it can please tell me)?<br />and if we are to get to another star ina non-conventional way, what will it be?<p><hr /></p></p></blockquote><br />simple answer to (that normal folks would understand) 'why can't matter go faster than light' would be 'for the same reason that you can't outrun your own shadow<br /><br />now I know science minded people might jump in here and show me that one can in fact outrun his own shadow under some special conditions (don't know really but wouldn't be surprised, not my cup of coffee figuring such stuff)<br /><br />what I want to say is that for matter, light (el/mag radiation) is the way of its fastest transport in the form of energy, matter itself as long as it stays as matter can not only never outrun that mode of transport but can't even equal it, only approach it<br /><br />and light for matter is not some external agent that it can bypass and choose to travel by some other mode, matter itself is inseparably connected with light down at the bottom of it, in fact matter can be said to be materialized light<br /><br />even if macroscopic bodies of matter are electrically neutral, the particles that make it up employ elmag fields to hold together in atoms and molecules etc and for matter to move faster than light would mean to outrun its own elmag fields and leave them behind (since those fields can transform and therefore move at speed of light only) which is absurd<br /><br />"if we are to get to another star ina non-conventional way, what will it be?"... the way I look at this is looking at other examples when we did something already that once seemed unthinkable - for example mankind always dreamed of trave <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

As I illustrated in my previous posts in this thread, when you put time dilation into context it makes relativistic interstellar travel more plausible. I used a 4 light year example at 0.6c, which takes the traveller 5.333~ years, but looks to an observer like it takes 6.666~ years.<br /><br />Lets take a destination further away, and check out how long it would take the traveller to get there at various speeds.<br /><br />Arcturus is a star that is 36 light years away. So if you could travel at just under the speed of light you would expect the journey to take something over 36 years - but it takes far, far less than that!<br /><br />As you approach the speed of light, the amount of time dilation increases exponentially.<br /><br />So, 36 light years:<br />At 0.1c it should take 360 years but actually takes 358.2 years<br />At 0.5c it should take 72 years but actually takes 62.4<br />At 0.9c it actually takes 17.4 years<br />At 0.99c it actually takes 5.13 years<br />At 0.999c it actually takes 1.61 years!<br /><br />The question is, how long before we can build ships that can travel this fast? Well I wouldn't expect it in our lifetimes! But I would imagine we will be able to travel at relativistic speeds before we discover how to exploit spacetime with wormholes or other exotic methods. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

<blockquote><font class="small">In reply to:</font><hr /><p>At 0.999c it actually takes 1.61 years! <p><hr /></p></p></blockquote><br /><br />yeah, but that's 1.61 yrs for astronauts on the ship, you got to keep in mind that for us left behind here it would take 36+ yrs for one way trip... who is gonna be the chosen one or should we say damned one? because when the astronauts would return, everybody here that lived when they left on that trip would be dead, I just hope you take stock of these secondary things too LOL<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

Of course.<br /><br />As I said further up the page...<br /><br />"At speeds close to the speed of light, it wouldn't necessarily take too long for someone to travel to the stars and back. Just don't bother waiting up for them!" <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

ok, I missed that one <img src="/images/icons/smile.gif" /><br /><br />anyway, once you get some years behind your belt and wisdom behind ears, you beging to realize that there is not much point in such mission except for those astronauts who will get to see what nobody had seen before<br /><br />but what is in it for the rest of us who would stay home? why should we go to the expense to provide them with the ship and all when they will just wave bye to us and vanish into the blue sky to be heard from no more (as far as we live that is, including our children)<br /><br />who cares about next generation reaping some benefits from it when it won't do any good for us, not even quench our curiosity, no nothing, nada, ship that surely would not come cheap would just go puff...<br /><br />if we would have the technology to do such things, wouldn't it be better to just explore closer space like that kuiper belt and what not in some reasonable time frames, not like now with Voyager taking decades to get somewhere there<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

In the short term, I agree. There is little point sending manned missions outside our solar system for exploration purposes - this is what probes are for. It is easier and cheaper to send unmanned probes to the stars (especially if we are searching for habitable planets).<br /><br />But in the long term? What if we want to settle on the planets around other stars? How about when we have colonies in a few different star systems?<br /><br />You could "emigrate" to a colony in a relatively short period of time. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

<"5. Most (admittedly fictional) accounts of relativistic travel assume that the ship would accelerate until it reaches the halfway or turnover point, and then decelerates until it reaches it's destination (or turns round and makes the return trip). In this scenario the traveller spends very little time, if any at all, in an inertial frame during the journey. Nearly the whole journey is either accelerating, deceleration or turning round. How does this affect the time dilation?"><br />from some refresher reading around, there seems to be a difficulty of computing time dilation that happens during accelerated motion, also all or many (or most) accounts don't ascribe the asymmetrical aging to happen gradually during acceleration phase of the travel but they see it (most of it) as happening all of a sudden during that instant in time when the rocket comes to the actual turnaround point - there the aging procedure makes a huge jump... <br /><br />basically all accounts that I read (that see no problem with twin paradox) are at some point unclear and downright spooky making it look like the answers they supply are cooked up to fit the case, typically they are fogy on the issue where exactly that asymmetrical aging happens, during which stages of travel<br /><br />I would say it is not they want to cover something up as it is that they want to fool themselves into believing there is no problem there <br /><br />that Hafele-Keating airplane borne clocks experiment is probably not decisive and perhaps one can't draw support from it one way or another on this issue, still it seems uncany that it showed such a distinct time lapse differences, I don't understand why this type of experiment wasn't repeated many times since then the way Michaelson-Morley experiment was <br /><br />from the symmetry of the two flights, there should have been no difference in the lapse of time gained or lost by the clocks on the two flights - East and West bound, only time difference should have bee <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

Thats a very interesting article indeed. Many thanks for taking the trouble to find it and post it! It leads me to certain thoughts about this subject..<br /><br />We know that time dilation happens, and we have an equation to describe its effects in a simple, general way. But the equation is <i> only truly validated after the journey has ended. </i> It doesn't help us understand what is actually happening during the trip. Especially as relativistic doppler effect precludes us from knowing what is <i> actually </i> happening to the traveller.<br /><br />I think the problem with a lot of the theoretical examples of time dilation is that relativistic doppler effect complicates the "observation" element of the experiment. This business of "time dilation being symmetrical between two inertial objects" is only ever illustrated by things like observing flashing lights, or radio signals. What I mean here is that the nature of light itself gets in the way of our understanding. We know that the speed of light is always observed to be the same, irrelevent of your actual velocity. If you are travelling at 0.5c, photons do not overtake you looking like they are travelling at 0.5c too.. they still move at c, relative to you.<br /><br />If we violate the laws of thermodynamics in order to observe the experiment, would that change the effects we see? I mean, if the traveller and the resting observer could monitor each other in <i> real time, </i> using some form of instantaneous transmission for instance, what would they see? I haven't seen any illustrations of this example, but it might help us understand the problem.<br /><br />If, as I am wondering, our current theory is only relevent when doppler effected observations are made, maybe there is some form of quantam-like element at work here. If we think of time dilation as a wavefunction of possibilites, we can only know the result <i> when the observation is made </i>? But any observation is doppler effected and therefore not an observ <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[mithridates]

Responding to the first post, it's my opinion that the first thing we should be concentrating on at this moment are telescopes and looking for other planets on Earth. I and others here know that the universe is huge, fantastic and with unlimited opportunities for exploration but to the average person it's a huge black void and it's hard to get the average person's attention when there isn't anything concrete out there to talk about (concrete being something with or with a high probability of having life). We're just about at the point where with our technology we'll be able to look at most nearby star systems, find their planets and analyze their atmospheres, and hopefully we'll be able to find something that the mass media as well as the average person can look at and say "wow, I bet there's life there." At the moment most of the planets we've discovered are huge and hot, and though they're pretty interesting in and of themselves there's little chance of life there so we need to keep refining our techniques.<br /><br />Once we have found a number of places that are really good candidates for life, we'll have the interest of the average person and the debate will move from these boards on space out into the major newspapers, and that's when I think technology to make the trip will finally seem necessary. That's why I think at the moment we should be focusing on observation and unmanned exploration, because it's cheaper and more effective, and will eventually find us something that will pique the interest of the average person. Going into space right now and circling the Earth in LEO just serves to drive home the fact that we're still pretty weak and pretty slow, and all the while taking valuable funds away from more worthwhile unmanned probes and space telescopes. That's the way I see the current situation. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[mithridates]

Oh, and by the way there's an interesting image on Wikipedia showing light going from the Earth to the Moon in real time with everything to scale including the size of the Earth and the Moon. Here it is:<br />http://upload.wikimedia.org/wikipedia/en/6/60/Speed_of_light_from_Earth_to_Moon.gif<br /><br />It's pretty interesting but looking at it this way the speed of light actually looks pretty slow. Anybody else get that impression? I mean, it's just the distance from the Earth to the Moon but I can drum my hands on the desk some twenty times before it even gets there. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[vandivx]

<"I still don't really know how the mechanics of the atomic clocks experiments help us, as the motion of the planes relative to the "resting" clock doesn't seem very symmetrical to me. ... And each plane shows a very different path through space from the other. Imagine plotting the paths of all three, seen from above, relative to the sun."><br />it was not meant to be completely symmetrical, on the contrary, only the inertial and gravitational acceleration was supposed to be symmetrical, flight as flight, same starting and landing inertial accelerations, same gravitational potentials BUT different paths through space insured by utilizing the Earth spin - hence the two directions chosen, East and West around the Earth over the equator<br /><br />the whole point of the last century of physics is that space is not absolute, you shouldn't be able to tell (detect) that you are moving through space, only relative to other bodies and only non-inertial motion should be detectable and even that is supposed to be relative in GR<br /><br />if the space should be absolute, then it would matter indeed what the path through it is but then most of physics would have to be rebuilt<br /><br />if the clock time lapse after the two trips should be different from each other, that would tell the whole story<br /><br />never mind comparing them to the clock left on Earth - that was mainly necessary because there was just one airplane taking two trips in succession but only interesting point was if the two flight clocks would suffer different time dilation after being made to undergo the same inertial acceleration and gravitational influences but over different path length in space<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>