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01192008, 08:01 AM  #1  
 
Class 2 Laser Join Date: May 2007
Posts: 350
Rep Power: 11 
I'm fascinated with space travel and if we are to ever travel between Stars we need to go as close to the speed of light as possible(actually we really need to exceed it many times over, but that's a different kettle of fish). *Also the other problem we have to deal with is Zero G. *So I got to wondering what if we built a space ship that was basically a huge disc were we would inhabbit the top(roof) or bottom(floor) of the disc, depending upon the direction we are accelerating, and accelerated at a constant 1  1.5 G to reach the destination ?? *The question I am dying to know the answer to is how long would it take, and how far would we have travelled, to reach the speed of light at a constant acceleration to maintain a force of 1G, and 1.5G respectively ?? *I know there will be someone smart enough on this Forum that could answer this question.
 
01192008, 10:11 AM  #2  
 
Class 3R Laser Join Date: Oct 2006
Posts: 2,032
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Hm, never really thought about that! Take E=MC^2 out of the picture and you have 1g = ~9.8 m/s^2. Speed of light is ~3 x 10^8 m/s. For distance, you have d = (v^2)/(2a). So in the case of 1 g where a is ~9.8m/s^2, we're talking ~4.6 x 10^5 meters (4.6 trillion kilometers) For time, you have t=v/a So at 1g its ~3x10^7 seconds (just under a year). Now, thats all taking relativity out of the picture though. With relativity, you cant even make it to the speed of light *:P. Well, the calculations would still *apply I guess, but you'll have a hell of a time applying 1G of force on anything once you're going a reasonable portion of the speed of light! According to massequivalence the faster you're going the more energy it takes to achieve the same acceleration, and to accelerate to the speed of light would take infinite energy (that's a HELL of a lot of power plants and you'd still wind up a bit short I think *). Good luck on your voyage! Don't forget to wear your seatbelt  
01192008, 12:48 PM  #3  
 
Class 2M Laser Join Date: Feb 2007
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I agree with Pseudo here, according to relativity, no matter, not even a particle can travel at the speed of light, let alone a ship with people aboard. The only way to travel huge distances or "appear" to break the speed of light is to "fold" or "warp space". Imagine a sheet of A4 copy paper with point A at the very top and point B at the very bottom, the distance in a straight line from point A to point B is 1 light year. now what if you were to fold that piece of paper in half? Now point A and point B are only seperated by the thickness of the paper , so a quick journey across the thickness of the paper takes you from A to B, now unfold the paper and you have appeared to cover a huge distance without actually breaking the speed of light. Think about it. Jase  
01192008, 01:54 PM  #4  
 
Class 1M Laser Join Date: Jan 2008
Posts: 168
Rep Power: 9 
actually americas army already have this technology antigravity engines you just dont know it yet dont expect to hear it on the tv news if you are interesten in conspiracy , technologies there alot of forums discusing that , also there are licenses of antigravity engine technologies
 
01192008, 02:53 PM  #5  
 
Class 2 Laser Join Date: Nov 2007
Posts: 317
Rep Power: 10 
There are two items relative to this discussion (sorry for the pun)  one is the existence of tachyons (not the ones they try to make you think they make bracelets out of...) The real tachyons are subatomic particles who's normal velocity is FASTER than light, and who's REST VELOCITY is infinite speed (which means there may be only one tachyon in the universe, and it exists in ALL places everywhere, simultaneously.) Secondly, there are some novel technologies being explored that do the space warping thing, but it is functionally equivalent to a lensing effect, most easily described by a movie effect we've probably all seen... One common example is in a horror or suspense film where someone has to run, for example, down a hall, and when they show the hall from their perspective, the camera does something with the lenses and the end of the hall appears to go further and further away, while objects in the foreground appear to remain in their proper distance. The warping effect is roughly equivalent to the inverse of that, whereby the target of teh travel appears to be suddenly just a few feet away, and the object to do the travelling actually reaches through the warped space and is there. If you were the traveller in this example, it would seem as if you simply took a few steps, but when you turned around to look back  the distance would be huge. This has something to do with actually distorting the fabric of space similar to what gravity does, but with a much smaller energy requirement than the creation of a planetsized gravitational field! In the field of chromodynamics (the more recent incarnation of Quantum Physics), there are some elegant mathematical formulas which precisely and with absolute accuracy describe the bizarre behaviour of subatomic particles/forces that no other field of study has been able to duplicate. There is a huge problem, however... in order to work with this mathematics, it forces you to assume two things very fundamentally different from what conventional science has come to believe. These two fundamental, radically different understandings concern the nature of empty space  the really "empty space" that exists between subatomic particles and electrons  the place where "nothing" is supposed to exist... But the math of chromodynamics  which I reiterate has been infallable in accurately predicting the behaviours of particles and forces like no other branch of science  requires us to accept that "empty space" actually contains: INFINITE ENERGY and INFINITE MASS at every infinitely small point of empty space everywhere in the universe. Any quantum heads among us who might want to chime in on this.... there's something here that a lot of bright minds are having trouble accepting  but cannot deny. Personally, I think it'll change everything, and make the whole problem of "faster than light travel" a moot point. In fact  we might never need to travel faster than we can walk! Dave X  
01192008, 04:51 PM  #6  
 
Class 2 Laser Join Date: May 2007
Posts: 350
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Wow !! *This is awesome !! *I love this stuff even though I understand only about half of it, but that dosn't matter to me, just thinking about all the new ideas and theories that come out is good enough for me. *Especially if the laws of Physics don't forbid them. Tachyons sound very cool !! And thanks Pseudo that is exactly what I wanted to know. *I'll save you a seat Well here is another one I have been wondering about for a while. *In order for light not to be able to escape(be seen) from a black hole wouldn't it have to be being pulled into the black hole faster than itself, essentially exceeding it's own speed limit ?? *I really don't have a clue, just a thought. Oh one other thing, is the Jury still out on whether light is a particle or a wave ?  
01192008, 06:07 PM  #7  
 
Class 2 Laser Join Date: Nov 2007
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Actually light is BOTH a particle AND a wave, it depends on what the observer is looking for  really! Google/Wiki the doubleslit experiments. This is the major "mystery" in quantum physics. IF light is a particle, it shouldn't exhibit wave motion, and if it's a wave, it shouldn't exhibit particle behaviour  but it does in both cases. OBSERVATION is an active force. Stranger than fiction! Likewise, if you want to really get why light doesn't "escape" a black hole, again, google/wiki "Event Horizon". It is a point wehere the escape velocity *required* to exit the black hole exceeds the speed of light, but it is only a requirement, not anything actually travelling that fast, hence once something enters the event horizon, it disappears from the observer's view as the light reflecting from it can no longer exit the boundary defined by the event horizon. Dave PS., the event horizon, also known by some as the "Oh Sh&#!!!" point!  
01192008, 07:28 PM  #8  
 
Class 2M Laser Join Date: Feb 2007
Posts: 810
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Morepower . what you are refering to is called "Escape velocity" It is the speed required to overcome the gravity produced by any concentration of mass. The gravitational field produced by any object depends on 2 things. Its total mass and the density of that mass. The higher the mass and the higher its density, produces a greater gravitational field and therefore the faster you have to go, to be able to escape the gravitational field it produces. The escape velocity of Earth is 7.1 miles per second (ie, you have to travel at that speed to break the earths pull to enter space) The escape velocity of the moon is about 1.5 miles per second, due to its lower mass. A black hole is usually the result of the collapse of a super massive star, under its own gravity at the end of its life. The matter is so concentrated and dense that a few grains of this material would weigh several thousand tonnes on earth. with such a concentration of super dense matter the gravitational pull and therefore the escape velocity exceeds 186,000 miles per second which as you know is the speed of light, so the "event Horizon Xan was talking about is the point around the super dense object where its escape velocity exceeds the speed of light, therefore we cannot see past it, hence the term "black hole" I understand that photons behave both as particles and waves but I think it is generally accepted now that photons have no mass and are indeed true waves. Jase  
01192008, 08:05 PM  #9  
 
Class 1M Laser Join Date: Sep 2007 Location: Nashville, TN
Posts: 169
Rep Power: 21 
In response to the first question: the main problem with that is the amount of energy that would be required. The faster your velocity, the more energy you need to keep that acceleration (according to relativity). The reason you can't travel the speed of light is that you would need infinite energy to reach it. We did a problem in physics that figured the amount of fuel need to reach something like half the speed of light and it was equivalent to the mass of the earth! :P that was of course usual conventional means, so until we develop a new propulsion method, we won't get even close to that velocity. This is exciting stuff! I love physics!  
01192008, 08:31 PM  #10  
 
Class 2 Laser Join Date: Sep 2007
Posts: 415
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Well, photons do have mass, or else you would have trouble setting up a gravitational lens. You can calculate their mass by solving E=mc˛ for m, and say E is the photon's energy (h*f). Actually, photons are not so special, if you start considering De Broglie's wave equation which says everything is a wave... hehe, gets really messy there. @Tallaxo: Isn't escape velocity the speed you need to leave a gravitational body never mind, reread your posting? I think he means the Schwarzschild radius, which is the radius of an object of a certain m,ass at whick it will trap light. To explain this, if our sun were shrunken down to a 10km ball, it would (contrary of exceed) the schwarzschild radius of its mass, and thus start trapping light coming in. About OP: Once you start approaching the speed of light, you get heavier. Thus to keep you accelerating at the same rate, you need more energy. For example, at .86c, your mass is now double of what it is at rest. So you keep on accellerating, and you keep getting heavier, and thus need more and more energy to accelerate, which in turn makes you heavier again...so yeah kinda hard to reach c. Although, to get to places fast, there are other ways. One being said, the "lens effect", which basically means "compress space so that what used to be a foot is now an inch". So if you then move with 100mph, space is flying past you at 1200 "compressed" mph. Now, as you get closer to c, that enables you to seemingly fly faster that c, although you move with less speed. Kinda hard to explain. Another idea seriously being thought through is teleportation. If you have ever heard of wormholes or bent space touching again, this is another way of "cheating on the universal speed limit"  because if you "jump" from a to b, your average speed (distance over time) might be over c but you have never travelled faster than it. Same if, at a car race, after the race has begun, you just drive off the road, and straight to the finish line, thus finishing the race in a phantastically short time. Yeah, physics can be puzzling and fun the same time  
01192008, 11:20 PM  #11  
 
Class 1M Laser Join Date: Sep 2007 Location: Nashville, TN
Posts: 169
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01202008, 01:54 AM  #12  
 
Class 2 Laser Join Date: May 2007
Posts: 350
Rep Power: 11 
Man I love this Forum !!! So many nice, learned folk willing to put in the time to answer some of my NOT so learned questions ;D ;D I honestly have to say that out of everything I have learned in life I have learn't some of the COOLEST things here. That whole light behaves differently depending on whether it is observed or not really perplexes me. I can and do think outside the square most of the time, but I give up on that one !! Just one other thing about whether light is a partical or not. If it is a partical wouldn't it be travelling at a slower rate after it has been bounced off a mirror due to the fact that, in theory, it would have to come to a complete stop to change direction ? And when we turn a light source on does it take any time for the light to reach it's speed, as in, does it have to accelerate from zero ? If it does have to accelerate then it has mass ? If not then it has no mass ? Crazy stuff huh ?? But it is good for the brain, use it or lose it they say. When I ask my friends stuff like this they just cock their head on one side, and with a blank expression ask me am I on drugs, and if so what are they so they know which ones to avoid ;D ;D ;D  
01202008, 03:12 AM  #13  
 
Class 2 Laser Join Date: Nov 2007
Posts: 317
Rep Power: 10 
That whole lightparticle/wave slow on bounce thing is really based on the echoes of Newtonian (pool balll) physics that most of us were brought up on. Think of it this way  a photon is a photon because it exists travelling at the speed of light. If it were to need to get up, yawn, stretch, check it's watch, and start running  it wouldn't be a photon, by definition! A photon is "born" going the speed of light. A photon is really energy only  but it can behave as either a particle or a wave. So when a photon bounces off of a mirror, it's more like a wave than a particle. A photon can be slowed by various media (my most recent research foray dealt with something called a BoseEinstein Condensate which can slow light down to 38mph! But  that IS the speed of light through that media, so a photon can continue to be a photon, even though to an observer, it appears to be travelling dangerously below highway speed! It is interesting to note that "the speed of light" isn't a constant everywhere  it varies all over the place depending on the media it is travelling through, another oddity  a very "wavelike" property, reminiscent of sound waves. What's really odd is when you examine how a photon is produced in solidstate lasers. Something happens to get an electron that is associated with an atom, all excited. It whirls around faster  electron on caffeine  but eventually, it can't sustain that level of excitation, so it finally flops back down on the electron couch where it rests  but when it does, it gives up all the extra energy it had in one single pulse  what we call a photon. The electon gave up no mass (heck, the electron hardly even HAS any mass), and yet, the photon can be observed as behaving like a particle (if we look for it to behave that way)... very strange. It's the universe itself stating what everyone needs to realize (many of whom are here on this forum!)  that you see in the world what you expect to find. Expect something different  and lo & behold, there it is. Look for a photon to be a wave, devise an experiment to prove it is  and it's a wave. Look for a photon to be a particle, devise an experiment to prove it is, and it's a particle. Wake up in the morning and expect to have a miserable day  and you will. Imagine the world is finally getting better, on a more harmonious track  and.... how you fill that in, is what you will find over time. It's a mathematical certainty. Amazing... Dave  
01202008, 09:50 AM  #14  
 
Class 2 Laser Join Date: Sep 2007
Posts: 415
Rep Power: 11 
Yup, that describes the situation pretty good! @Morepower: The way reflection works: There are two concepts of reflection in my head, and I am unsure where to apply which: On the one hand, light is a (radio)wave. So this "Radiowaveatvisiblefrequencies" flies into a mirror. Now when this hits a metallic mirror, it will be swallowed like a radio wave hitting a receiving antenna. So now this "light" is trapped inside the mirror as an electric signal. But every electric signal inside a conductor broadcasts an electromagnetic wave. I.e., the metal surface "rebroadcasts" the light wave This is really messy, might not help clear things up On the other hand, as to why the photon doesn't "stop" when being reflected: The photon you send to the mirror isn't the photon you get back. So you throw your photon at that mirror, and once it hits it, Schwoops, a mirror atom (or electron, rather) absorbs it. No more photon then, it dissapeared, and the electron does its "highcaffeine dance". So the photon didn't really stop, it was just "dissolved" in midair. Then suddelny the electron emits that energy again, by creating a new photon. Which then starts off with regular c. Still, I don't know why that would explain "inward angle = outward angle"... About the waveparticleconcept: What helped me was to figure that mass and energy is basically the same, mass just being "more conpressed". But saying the tiny fracture of energy the photon has can, just as it likes, jump to being mass and back to energy. So (yeah, I know this isn't right) imagine a "cloud of energy" flying through space, that might as well condense into one tiny ball of "solid matter". So if necessary, the photon can shift its "shape" to particle, if needed, or back to energy/wave, if a wave is needed. What I think is really thrilling is frequency doubling (and other quantuum optics stuff). Got no insight there, but shining a light into a crystal which makes one out of two..that's just a very complex thing to grasp, in my opinion.  
01202008, 10:20 AM  #15  
 
Class 3R Laser 
Dave, I couldn't have explained all that better myself. Seriously I know and understand it, but im crap at explaining it :P Regarding space travel. Faster is definitely not the way to go. I read a lot of Asimov, both the novels and serious scientific books which I learnt a lot of this from. A singularity, if it exists, is the perfect way to travel. By simply folding space, you can travel seemingly through vast swathes of 3 dimensional space while only having moved a very short distance by your own perspective. A problem a lot of people have is thinking of travel only in 3 dimensional space. We move freely in 3 dimensions, at a fixed speed and path in a fourth (time) and... a whole lotta other really odd things go on in dimensions 513 which I have no idea about. Think of this. You can represent 3 dimensional space on 2 dimensions, like in a seemingly 3D drawing or graphic. It follows then, that you could represent 4 dimensions in 3. A mistake a lot of people make here is trying to imagine 4 space dimensions, which there aren't. We can theoretically just as easily fold 3 dimensional space as a 2 dimensional image. The thing is, we have to work out how to make the laws of physica simply not apply to a certain object. philguy, the way I understand frequency doubling is this (I'm probably totally off): that inside the molecular structure of the crystal, the lattice is arranged just so, that it is exactly right to make the photons bounce backwards, then forwards in half the distance, i.e. at half their original wavelength. like going > < > > > if you get what i mean. Also Dave, re tachyons. If they (it) exists at or above light speed, then the only option for it is to exist everywhre simultaneously. That's smply what faster tahn light velocity entails.  
01202008, 10:30 AM  #16  
 
Class 2 Laser Join Date: Sep 2007
Posts: 415
Rep Power: 11  Quote:
Okay, I dare you to a) get me a 3DModel of a 4Dworld. b) prove me wrong when I say "there is no 4th spatial dimension". By the way: your first statement implies there is a fourth dimension of space. Also, it isn't really that hard to picture a fourth dimension I think this is really problematic as as we are 3dimensional beings, the concept of movin not only "sideways and longways and slantways and any other way you can think of", but also "out of" this space. The problem becomes a bit clearer when you picture explaining a 3Dworld to a 2Dguy.  
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