186282.397 miles/second

[sad_freak]

let's face it. ant space craft we ever built goes pretty damn slowly. <br />the fastes any craft's ever got to the moon i bleive was 9 hours. i can get from glasgow to london in less time.<br />and when you go to the moon, if you plan to return, half of the weigth of any craft it made up of fuel. <br />it has taken voyoger 17years to get past ploto, i belive. i have almost lived that long. <br />so even if we conqure the fuel and speed problems, then we are capped at 186282.397 miles/second aren't we. light speed. you can't go faster.<br />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?

 

[why06]

4.3 years is still a lot less than 17<br /><br />.....and anyway light speed travel is a ways off, but if wormholes could be perfected all we woul need to do is land a wormhole on the planet and we could travel back and forth as much as we wanted. <br /><br />don't get discouraged though.... the distances were traveling even in the near future will be incredible <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[qso1]

If humanity is meant to progress, it would seem to me we will eventually conquer this obstacle somehow.<br /><br />1.<br />One way is finding the science of SOL today has to be revised because some of the assumptions were wrong. The big one being we cannot exceed the Speed Of Light (SOL). One day we might find we can exceed the speed of light. We could then build starships not unlike those found in science fiction and go on to explore other star systems.<br /><br />2.<br />If we find SOL to be the limit, we can build multigenerational starships in which generations of humans pass before the ship arrives at a destination. Chances are, a starship will be a large vessel, large enough to contain and support 1,500 people or more. A small contingent of that group being the actual explorers of any worlds. If they determine the world being explored can be settled, the rest of the crew except minimal ship staffing, can come down. The minimal staff being rotated as needed.<br /><br />3.<br />Shortcuts through the space time continuum such as the wormholes described by why06 would also be possibilities, especially if it is found one can traverse distances that might be to great for even multigenerational distances. Trips to other galaxies for example.<br /><br />We may even progress through all three possibilities, from the simplest (Multigen ships) to the most complex (Shortcuts).<br /><br />The link below will give you some good info on SOL.<br /><br />http://en.wikipedia.org/wiki/Speed_of_light <br /><br />BTW, the fastest humans have travelled to date (About 7 miles per second) is about .004% SOL. These speeds being achieved on Apollo lunar flights during earth escape and just prior to re-entry. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[vandivx]

I think going to that nearest star would be worth it only if there were advanced civilization to be found there (I mean if we actually knew its there by having a contact with them) and if we found a way how to shrink the travel time to several years, like to 5 or 6 <br /><br />I don't know much about SETI programs but I suppose they do focus specifically on Alpha Centauri besides the general looking in all directions? <br /><br />realistically though, 'going to stars' is stuff for deep deep future if it will become possible at all, ever<br /><br />from my personal point of view, I mean from the point of my brief life, my only hope in that way is if somebody from out there travels to us here, that there is somewhere out there a civilization so immensely advanced to be capable of visiting us <br /><br />I imagine that one day we will have means of communication capable of mediating chat and even TV and inter-star-net with nearby stars' civilizations, perhaps capable of spanning the whole galaxy, but actual physical travel I don't think so<br />I can see the romantic side of such travel but a more hard nosed approach tells me there is no real need for such travel, just curiosity, and you know what killed the cat... LOL<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[cyrus_daywalker]

the galaxy spins correct? what if we launched a space craft extremely fast in the opposite direction, would that allow a shorter time to get out of the solar system? not necessarily towards a star but it would allow for us to leave the solar system correct?

 

[kmarinas86]

<font color="yellow">the galaxy spins correct? what if we launched a space craft extremely fast in the opposite direction, would that allow a shorter time to get out of the solar system? not necessarily towards a star but it would allow for us to leave the solar system correct?</font><br /><br />Launching in the object backwards wouldn't do much difference as launching in the forward direction. Alternatively, we may choose to launch in the direction of the earth's orbit and spin (when they are both going the same direction) when the earth is moving away from the center of the galaxy. If we have enough fuel we can rocket up to a higher orbit where the orbital period around the galaxy is greater, taking us away from the solarsystem. But we need more fuel and perhaps some gravity assist.

 

[derekmcd]

<i>the galaxy spins correct? what if we launched a space craft extremely fast in the opposite direction, would that allow a shorter time to get out of the solar system? not necessarily towards a star but it would allow for us to leave the solar system correct?</i><br /><br />IIRC, we did exactly this with Pioneer I and Voyager. They were launched in opposite directions. I believe the Pioneer craft was launched in the opposite direction of the of the sun's relative motion. I think Pioneer is about to leave our solar system and enter the heliopause (the point in which the sun's gravitation effects are almost nil or negated by interstellar objects). <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[SpeedFreek]

Hi there! I'm a noob interested in astrophysics and cosmology and this is my 1st post here. <img src="/images/icons/smile.gif" /><br /><br />One thing to remember about travelling at relativistic speeds is the phenomenon known as time dilation. You know how the idea is that someone leaves earth and travels near the speed of light and when they return to earth everyone has aged faster than they have.<br /><br />Well it makes interstellar space travel palatable! For instance, to travel 4 light years at 0.6c only takes 3.2 years! Huh? Well it takes 3.2 years for the people on the spaceship, but if we watch the ship from earth it looks like it takes 6 years 8 months to get there.<br /><br />The way it would work in practice is, that as you accelerate 0.6c you see the distance to your destination actually shrink! If you were travelling to the nearest star (let's call it 4 light years away), and you travel at 0.6c, the journey would only take you 3.2 years (according to special relativity where sqrt(1 - v^2/c^2) = 0.8). But to an observer on earth the journey one way would take 4/0.6 years, or 80 months. So the round journey for the spaceship would be 6.4 years. But when you got back 160 months or 13 years 4 months would have passed here.<br /><br />And thats only 0.6c! The time dilation increases dramatically as the speeds get closer to c. And of course, if you could travel AT the speed of light, the journey would be instantaneous. But you don't need to get to the speed of light for interstellar travel to be quick for the people doing the travelling.<br /><br />So if we can travel at relativistic speeds, close to the speed of light, interstellar journeys could be really quick. But only to the people on the spaceship. <br /><br />Edit: My maths was wrong above, (see below) but the principle still stands - the faster you go, the less time you experience compared to people back on earth. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[harmonicaman]

<b> -Speedfreek -</b><br /><br />Welcome aboard; nice first posting!<br /><br /><i>"The time dilation increases dramatically as the speeds get closer to c. And of course, if you could travel AT the speed of light, the journey would be instantaneous."</i><br /><br />Well; I would argue that to got your "m" (mass) up to "c" (the speed of light) it would take all the "E" (energy) in the universe. If you actually reached "c", you would find that the universe had suddenly become a very cold and dark place.<br /><br />Pondering near relativistic velocities is one thing, but you never want to get too close to "c" because you'll find that the universe has passed you by... <img src="/images/icons/rolleyes.gif" /> <br /><br />E=mc²

 

[spayss]

As a chemist I can state that energy to accelerate a particle to the speed of light is the easier issue. The difficult issue, and the one that is overlooked or ignored is the nature of the material itself that needs to travel at near the speed of light or even one thousandth the speed of light. Unobtanium.

 

[SpeedFreek]

Hi Harmonicaman!<br /><br />Good point, well made <img src="/images/icons/smile.gif" /><br /><br />I only mentioned being at the speed of light as an example of ultimate speed, but made sure to point out that we don't need to go that fast.<br /><br />Having only recently understood the implications of relativistic speeds myself, I was feeling a little evangelical about the positive benefits of time dilation! <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[khaihar]

So - under the assumption that Time is Constant, 1 second is 1 second. Just because position changes, wouldn't mean time changes. The time it'd take the light to catch up to the position change would be what you're viewing, not the craft itself.<br /><br />Someone flying 4 years out at any speed is still 4 years elapsed in time. You may be seeing the ghost of their images. Such as, a supernova-ing star. We know by the time the light hit us, the star is likely passed it's Supernova state. We're just /seeing/ the past, not the present in real time. Because light is so slow to cross the 'verse.<br /><br />

 

[SpeedFreek]

To Tigerbiten:<br /><br />Oops you are quite correct! My maths sucks and I applied the equation wrongly <img src="/images/icons/smile.gif" /> I'm still learning this stuff myself.<br /><br />As you said, it would take 5.333 years to travel 4 light years at 0.6c, but to an observer on earth it would look like it took 6.666 years. So the round trip would take 10.666 for the traveller, and 13.333 months to the observers on earth, a difference of 2.666 years, or 32 months.<br /><br />So over the round trip, when the traveller returned they would be 32 months younger than if they had stayed on Earth.<br /><br />To khaihar:<br /><br />Im not sure I understand you correctly. Although we do have to take into account the lag that the speed of light causes for the observer on earth, the observer still ages more than the traveller. I used a round trip scenario on purpose, so both people are back in the same position and inertial frame at the end (but the traveller has aged 32 months less than the observer). Mathematically, the lag is cancelled out on the return journey to all intents and purposes (the light cannot return after the spaceship!), although the way it all happens is a lot more complicated than my description (I left out the fact that the time dilation all happens during the acceleration, deceleration and turn around phases of the trip. When travelling apart at a constant 0.6c they are in the same inertial frame and if both people could see each other they would both look "slowed down". On the return trip, when travelling at the constant 0.6c, they would look speeded up to each other. The time dilation only actually becomes apparent during the acceleration, deceleration and turn around phases.)<br /><br />A person travelling at relativistic speeds wouldn't notice that seconds take longer to pass than at home, but they would experience less seconds than the observer over the journey. They would age less. It seems that time is not a constant unless you are in the same inertial fra <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>(I left out the fact that the time dilation all happens during the acceleration, deceleration and turn around phases of the trip. When travelling apart at a constant 0.6c they are in the same inertial frame and if both people could see each other they would both look "slowed down". On the return trip, when travelling at the constant 0.6c, they would look speeded up to each other. The time dilation only actually becomes apparent during the acceleration, deceleration and turn around phases.) <p><hr /></p></p></blockquote><br />I think that standard view in physics is that the time dilation effect takes place during travel at constant speed and that the acceleration stages of the trip while contributing to time dilation are negligible or can be made negligible by arranging the experiment to bring that out<br />your view seems to be part of disenting 'heretical' minority<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

I think I may have used the term time dilation too loosely, or you misunderstood me. I am talking about Einsteins special relativity, not a minority view. Maybe I just put it badly <img src="/images/icons/smile.gif" /> When I said "the time dilation all happens during.." what I should have said is that "the difference in their ages is considered to have happened during..". Time dilation describes the whole process, but I was just concentrating on the interesting part!<br /><br />Time dilation is symmetric between two inertial observers. When the traveller and the observer are moving away from each other at a constant 0.6c, they are in an inertial frame, so the time dilation effect looks the same to both of them (they are both slowed down the same amount, to the other). When they are moving towards each other at a constant 0.6c they are both speeded up by the same amount to each other.<br /><br />When the traveller returns and has aged 32 months less than the observer, this difference between the two is considered to have all happened during the acceleration to and deceleration from 0.6c.<br /><br />It is all covered in the so called "Twins Paradox" (which is what I based my example upon). It appears to be a paradox if one expects that, according to relativity, either traveller or observer may validly claim to be "at rest" (is the ship moving away from the planet or the planet away from the ship?), and thus each expects that the other will age slowly. Like most paradoxes, this occurs because of faulty assumptions. This one happens because the traveller undergoes acceleration while the observer does not. At the times when they are not in an inertial frame, it is the traveller who is swapping inertial frames, not the observer. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[vandivx]

LOL I didn't misunderstand you at all and you say again what you said before<br /><br />I 'think' that the traditional or the conventional view tought in classrooms is that the time difference in the twin paradox thought experiment comes about from that part of the trip when the 'traveler' moves at constant speed, actually it can be demonstrated mathematically that acceleration induced time dilation is a negligible contributing factor in the twin paradox experiment<br /><br />I picked on it because you seemed so sure about your claim <img src="/images/icons/wink.gif" />, I happen to be on the establishment side as far as the facts of the twin paradox go - that the time dilation is caused by traveling at constant speed - although I can see how people can have big problem with that on the current widely accepted premises (that motion is relative), hence the disenting opinion ascribing the time dilation effect purely to acceleration but that IMO is not the solution<br /><br />I suppose there would have been 'twin paradox' thread here somewhere already, no use trashing it out again, I thought I would ask which side seems to be getting upper hand these last few years as I don't watch the scene too much lately<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[Saiph]

van, feel free to hash it out, it's been a while since the twin paradox was discussed (the current fad appears to be the speed of light afterall). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[vandivx]

yep, speed of light is in and time dilation is one way how to get around its limitation, so<br />~~~~<br /><br /><br />re: speedfreek<br /><br />about acceleration being what's behind the time dilation, for starters there were those muons that lived longer than expected in cosmic particle showers and it was their speed that did that trick I understand, earth's gravitation field is negligible factor here, that was the first experimental confirmation of the time dilation unless I am mistaken (feel free to correct me, I am bad at history)<br /><br />then you have those experiments with clocks flown on planes actually done - one flies Eastbound around the earth and the other Westbound and when they land again, their clocks don't aggree, everything acceleration vise is symmetric except that one plane flew in the direction of Earth rotation and the other against it (which altered their speeds 'through space')...<br /><br />I would be curious then how you view photons of light for which the time stands still because they travel at constant speed which is widely aggreed view and physics would have to be reworked quite a bit if your ideas were to be right<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[aidan13791]

Building on the post about time dilation, because time passes slower at higher speeds, then time and age wouldnt be much of a problem because <br />a)the astronauts would live longer because the slowed time is like a form of stasis<br />b) it takes less time to reach the star or planet because time has slowed due to time dilation, from the astronauts' perspective.<br /><br />Re. VanDivX<br /><br />I believe that time will have stopped for a photon because it travels at light speed, and there is also a loophole regarding the SOL. All one needs is an object with negative energy (the hypothetical tachyon) as it will be on the other side of the SOL, and just as a an object with positive energy cant exceed lightspeed, a tachyon is forbidden from going slower than the SOL.<br />

 

[SpeedFreek]

Well firstly, I am humbled by your superior knowledge in this field <img src="/images/icons/smile.gif" /> I thought I understood the concepts, but there do seem to be problems with my understanding of time dilation and special relativity.<br /><br />I am an interested amateur, and have no formal education in these fields so I am open to anyone who can explain these things.<br /><br />Instead of making statements based on my limited understanding, I will ask questions.<br /><br />1. If time dilation is symmetric between 2 inertial observers, and they see each other sped up or slowed down by the same amount when in an inertial frame, how do they end up aging differently? Wouldn't they see the other slowed or sped up in a non symmetrical way only during the times they weren't in an inertial frame?<br /><br />2. In the atomic clocks on planes experiment, did the plane flying against the earths rotation have the same airspeed as the other plane? Or did they subtract the speed of the earths rotation from its velocity?<br /><br />3. A photon "experiences no time" during its journey, so if we could observe it during it journey towards us, would we see it "frozen in time"?<br /><br />4. If the photon could observe us as it journeyed towards us, would it see us frozen in time too? (This seems a silly question, I know!)<br /><br />5. Back to the twins paradox I'm afraid! 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 /><br />I wasn't trying to propose radical ideas, I thought I was saying it the way science does, but it seems I was wrong. Feel free to help me understand <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[aidan13791]

Well, I can only answer questions 3 and 4, I'm not all that well informed on the others. I think that as the photon itself is frozen in time, we *should* observe it accordingly, and as we are experiencing 'normally' progressing time, then this is what the photon will see. This is because one objects state in time shouldnt affect another. However, this is just my understanding of the subject, i also have no formal education in this (yet). I hope that helped.

 

[vandivx]

I will also just reply for now to Qs 3&4 for now, here is just a link for now http://www.mathpages.com/rr/s6-06/6-06.htm<br />start reading halfway down the page there<br /><blockquote><font class="small">In reply to:</font><hr /><p>Another experiment that could be performed is to fly clocks completely around the Earth's equator in opposite directions, so the eastbound clock's flight speed (relative to the ground) would be added to the circumferential speed of the Earth's surface due to the Earth's rotation, whereas the westbound clock's flight speed would be subtracted.<p><hr /></p></p></blockquote><br /><br />observing photon as it journeyed towards us would be similar to observing a dead human body with its eyes open staring ahead into space unfocused, a body for which life, time was suspended, sort of like watching egyptian mummy suspended in time and coming to life when it would slow down<br /><br />photon would not observe us (feel free undressing in your room while light comes in LOL), that is if we were the photon and moved as it does, we would not be conscious of anything (ok, we would still have burnt on our retinas that last view we had before we attained the speed of light but as consciousness/life is incompatible with stillness, not just outer but inner one as well, we would be for all practical purposes like that dead body above, suspended in time, our eyes staring unfocused into space, as far as life was concerned, we would be in effect unconscious for the time being, while moving at speed of light and only when we would slow down a bit, just a touch under the speed of light, we would beign to see the world but everything would be in a blur, in extremely fast motion, so that if we could stick to one spot, say by circling above it at nearly the speed of light, we would see people grow old in a jiffy and die in no time, generations would go by while we would experince aging by just a few seconds, <div class="Discussion_UserSignature"> </div>

 

[SpeedFreek]

Of course! It makes sense. Many thanks for these answers.<br /><br />If I may sum up 3 and 4 to make sure I understand them:<br /><br />We observe a photon from alpha centuri, heading towards us at the speed of light. It takes a little over 4 years and all the time we observe it, the photon looks as if it were suspended in time.<br /><br />The photon leaves alpha centuri and, observes us as it makes its journey. As the journey is instantaneous, any observation of us would look like we were suspended in time, because all it could observe is an instant in time.<br /><br />Is that it?<br /><br />If so, now I just need to understand how inertial frames and acceleration work in relation to time dilation. <img src="/images/icons/smile.gif" /> The more I think about it, especially if the whole journey is acceleration to and deceleration from relativistic speeds, it seems logical to conclude that any difference in ages of the viewer and the traveller occurs during the non-inertial frame (seeing as when in an inertial frame, the dilation is symmetrical). Sorry I'm repeating myself here.<br /><br />When I look for explanations from university websites, I find a few that mention the difference being caused by the swapping of inertial frames, but most seem to overlook it, describing the whole journey as if it happens at a constant speed. <img src="/images/icons/frown.gif" /> The maths all adds up (the frequency of flashing lights on the spaceship vs those on earth) the observations all add up to the traveller experiencing slowed time, but whenever they describe the 2 people viewing each other, they say that they both see the other slowed/speeded up by the same amount.<br /><br />STOP PRESS! I just read the link vanDivX posted. While I won't pretend to understand the maths, I understood the principles mentioned. Many thanks for that <img src="/images/icons/smile.gif" /> I also went to that sites main page and found a page about the twins paradox and all I can say is sorry! I didn't mean to open up <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[harmonicaman]

Answer to Question 2.<br /><br />In the famous atomic clock experiment (Hafele-Keating, 1971); the airplane that traveled <i>westward,</i> or against the spin of the Earth, gained time when compared to clocks that were both "Stationary" on the Earth and travelling eastward, with the spin of the Earth.

 

[aidan13791]

Yes, apologies. My response was a little bit off. We observe the photon as frozen, and it observes itself as frozen. As it is 'frozen' in time, time doesnt apply, so everything takes no 'time' at all. <br /><br />However, does the photon observe us as frozen or in our 'normal' time? I am still a little unclear on this. I dont think that the term 'frozen' is appropriate. I think that it is more logical to say that time doesnt exist to the photon. Therefore, as time is like a state of progression, it makes sense for the photon to see us as frozen. But it also seems to make some sense for us to be seen as non-frozen because we are not frozen in time. I think this because we are progressing in time, and if we did something to affect a photon, then it would make more sense for it to be able to go through a process of changing state than it does for it to be able to jump from one state to anothe. Can someone please clear this up for me. <br /><br />Thankyou in advance.