Given the dodgy rep of Chinese research...
I'll wait for it to be peer reviewed and the experiment replicated thank you very much.
Time to start crying in your beer, people: according to researchers at the Hong Kong University of Science and Technology, not only is it impossible to break the speed of light, it will always be that way. Forget time travel, forget trips to distant galaxies, and ditch the idea that there’s a more advanced civilization than …
..it's racial stereotyping. Don't confuse the two.
Racism is when you act on, make a biased decision, or treat somebody differently based on this information (e.g based on a racial stereotype).
Also applies to sexism vs sexual stereotyping. Loads of sexual stereotypes on TV adverts (e.g. men can't multi-task, women can't catch or throw, women love to gossip, men love cars), but not employing a man or woman because of these stereotypes ("sorry, can't employ you because you would spend too much time gossiping in the office as you are a woman") is sexism, as you have made a biased decision based on a stereotype.
Admittedly an increase in stereotyping does lead to an increase in 'ism' (hence most people make the same mistake you did) but they are not the same thing at all.
My understanding is that racialism is making a distinction between people based on race, whereas racism is doing so with negative connotations.
Either way, it doesn't really matter because the point remains that some people (not all - it is so convenient to generalise, after all) are still following the formula that because this research was Chinese, it must be of lower worth, because fake products come out of China, therefore everything that comes out of China is fake. Which is clearly wrong.
..so do you tell black jokes about fried chicken? They're just jokes, right? Got any good Bernard Manning DVDs? You don't know whether anyone was offended by negative comments against the Chinese on here, and given how widely El Reg is read, it's more than possible.
But often the "it's just a joke" defence is wheeled out by people who can't or don't want to confront their own ignorant views.
> Tarring everyone with the same negative brush because they belong to the same race...
That seems like a reach, when your example really tars everyone with the same negative brush because they come from the same COUNTRY, which is a different thing. Yes, most (but by no means all) people who live in China are Chinese, but that is not germane, unless the original statement was "anyone who looks like they're Chinese only create fake products", which really would be racist.
..that no-one was claiming it's a group of Yorkshiremen knocking out Harry Potter compilations DVD, Louis Ditton handbags and dodgy scientific research. I'm pretty sure whatever blanket assumptions were being made it's on the basis of the producers being Chinese as well as being in China - but please correct me if I'm wrong.
I have no issue with someone discussing fake products coming out of China.
However I would not consider someone automatically asserting that a scientific paper is rubbish solely on the basis that the people writing it are Chinese to be a 'discussion of fake products coming out of China'. Especially when said individual clearly hasn't read either the report or the article in question. That would be more in the racial prejudice area wouldn't it.
"Wow, nothing like a bit of comedy racism eh?"
It's not comedy racism. It's a well-known fact in science circles that the best and brightest in China (and not just China, but many countries all over the world) run away to more interesting universities very early, leaving the still quite talented people left behind largely cut off from the main thrust of scientific research. They generally end up producing uninteresting research because of this, not because of any inherent weakness of Chinese genes.
Acknowledging that one country has not very good research is not racism, and using that word to describe verifiable conclusions cheapens it to the point where real, actual, important, racism is ignored or similarly tarnished. See also: wolf, boy who cried.
You're missing the point, this has nothing to do with the general quality of papers coming out of China.
This was a specific incident about a specific paper. Someone made a comment about an individual paper, that was peer reviewed by knowledgeable and hopefully independent scientists in the field, then accepted by the editor of PRL for publication (indeed was one of the Highlight articles in that particular issue). That comment was solely to rubbish the paper based on nothing more than the ethnicity of the authors, no other reason was suggested for why the paper might be no good. So how exactly is that not racism?
"That comment was solely to rubbish the paper based on nothing more than the ethnicity of the authors, no other reason was suggested for why the paper might be no good."
No, not ethnicity, location. If the university involved was the University of South-West Shropshire, or for a real one, Bishop Grosseteste University College Lincoln, then I would say the same thing. That university has a history of producing rubbish, this is from that university, therefore it is *likely* to be rubbish.
Oh, and peer review, yes, well, I am a reviewer for peer review and I don't know what I'm talking about, so that kind of cancels that point.
Actually 20% of the articles published by US labs are either completely withdrawn or amended after publication for "inconsistency" reasons (read: suspected fraud), or proven completely wrong within one year. That places the US firmly in first place when it comes to "dodginess" in research. What do you expect when 80% of the labs workforce is in short-term contracts (1 to 3 years) and under enormous pressure to publish?
Chinese research actually has a good reputation these days (in terms of integrity, if not for ethics). Hong Kong, origin of this paper, is seen as an emerging world-leading research center.
"It's a well-known fact in science circles that the best and brightest in China (and not just China, but many countries all over the world) run away to more interesting universities very early..."
It's a fact that many of them return after their education to help raise the standards back "home" and find highly productive and profitable jobs. This is especially true given the current economic climate as costs tend to be lower and opportunities more available. In the case of China, many of the best and brightest are state sponsored with the intent of getting a world class education and bringing it back to keep the economic growth going through research, business and education.
That said, you may be right and it may not be racism but it certainly is ignorance. After all, it's a well-known fact that many people can't look past their own pride colored glasses.
Problem El Reg ?
I would have said the same thing if it had come out of some other less than trustworthy institution....
It has been peer reviewed... but has it been replicated?
As long as you choose friendly peers, anything can be "peer reviewed" successfully.
Am I wrong in wanting science tested over and over ?
That is what science is about.
I always took from Albert that an arbitrary "something" travelling "faster than c" as far as an observer is concerned wasn't impossible, but rather meaningless. And if the observer itself is travelling at c - relative to an arbitrary "something" - travelling across the universe would mean the time taken would tend to zero - ie distance would become the meaningless factor - in the sense that the concept of "relative to an arbitrary something" would be nonsensical.
But I haven't had my morning coffee yet.
Warning: Armchair physics ahead:
An observer travelling at c will still spend whatever local time he or she takes to cross the universe - you can't magically ignore time just because you're going fast. The point old Albie was trying to make about that was that however much personal time passes for you, the time that passes in the rest of the universe will be a function of both the distance you travel and the time you personally take to travel it (ignoring any tedious acceleration and deceleration). Which will be significantly greater than your local time.
Things can teleport over very short distances (atomic scale) in a phenomenon known as quantum tunneling. It is the idea behind Hawking radiation that black holes presumably emit, for example. Nothing we've ever found travels faster than the speed of light over macro-scale distances though.
This paper says that information cannot travel faster than the speed of light when propagated by light, which whilst nice to know doesn't rule out tachyons or time travel. Hell, it doesn't even rule out exotic bits of space time like wormholes or alcubierre metrics; their issues come from other bits of physics.
So no, this doesn't have much to tell us about time travel.
Re: hawking radiation:
Not quite, Particles are constantly being created and annihilated in free space, to conserve energy and momentum (along with the other conservables, spin, strangeness, etc) they have equal and opposite E and P. Normally, these are short lived (almost instantaneous), but if one gets destroyed by something it is annihilated by the other, say a black hole eating it, the other one will remain (and is this case of a black hole, will appear to be emitted from the black hole)
There is another way to look at these than a particle/anti-particle pair appearing and then anhilating. An anti-particle on a feyman diagram looks the same as a normal particle travelling backwards in time. So another model is a single particle oscilatting backwards and forwards in time. I.E. Time travel, but heavily restricted by the energy-time version of the Heisenberg uncertainty principle and therefore useless for getting next week's lottery results.
Of course if this model is correct then it rather messes up the Hawking radiation theory, since I'm not sure how half of the pair falls into a black hole if its really a single particle. Just need the LHC to generate some quantum black holes so we can establish which is happening experimentally (by getting hawking radiation or not).
But it so happens that light travels at speed c - most of the time.
c would still exist and would still be the cosmic speed limit if there wasn't any light.
One apparent, but only apparent exception - the nature of the expansion of the universe is that distant space and distant objects are getting farther away from us although they are not moving farther away from us. So a distant object might appear to be moving away from us at more than the speed of light, but that is because space between here and there is stretching. It is indeed getting farther away, but it is not moving. And if it's receding at > c then you can't get there. We can see its past but never its present. And people there will say the same of us. If there are people there, which we can never know, see above.
1. photons? why photons, when time-tunneling neutrinos are already on the table? that's like moving from the gasoline engine back to the horse.
2. if time travel will ever exist - ever - then time travelers are here, now, in their subjective past. you want time travel technology? look for time travelers. they won't be that hard to spot: tall, vaguely asian, short attention spans and fast conversation, hanging around breaking news sites and places where large quantities of resources are available and not very well watched (war zones and colleges).
3. okay, 3, and that's all, i promise: a great way to defeat an enemy state or to take over your own. go back in time and start a religion that shapes that nation's citizens into willing followers.
okay, done. except for 4: maybe the reason that there aren't any time travelers isn't that there won't ever be any time travel, but that they do something so stupid that time itself ends. or we do.
And, if there are, why would they necessarily look and act as you describe? If they are from the future then engineering or disguising their appearance somehow is likely to be an option. And why show themselves and expose themselves to risk?
OTOH, why not show themselves, since copious reports of "aliens" or "ufos", not matter how bizarre or how many witnesses, are routinely ignored and dismissed anyway.
If time travel was possible you may never see a time traveler. Why? I know that the stealth bomber exists but I've never seen one, same with expensive cars. So If a time traveler came here he would be few and far between to amount to not existing. And how do you know what they would find interesting? Looking up Hitler as boy: Hitler was nothing special as kid, he had done nothing so no historian was watching him. So if a traveler was observing, who would know? Things only become interesting after the fact. Even Jesus' childhood was skipped.
"if time travel will ever exist - ever - then time travelers are here, now, in their subjective past."
This is a common rationale against time travel, but it makes a wide range of assumptions on the nature of the universe. If it is possible - and the odds are stacked against - then you might not see them here, in their past, as it hasn't been discovered *yet* - their past, may not be our present, if we invoke a many-worlds theory.
For your statement to be true not only requires that time travel be permitted, but also that the future is fixed, which raises many deep philosophical questions.
"For your statement to be true not only requires that time travel be permitted, but also that the future is fixed, which raises many deep philosophical questions."
A fixed future is a pretty easy time travel model to work with. Basically you can travel back in time, but you can't make any changes. The reason you can't make any changes is because you've already made any changes you would make when you traveled/will travel back in time. Trying to make any other changes is futile because you've already failed to make them.
Granted that's in fiction. It's one of several possible models in reality (assuming, of course, that time travel is possible, which is a foolish assumption).
Actually I once saw an MIT lecture on black holes where the speaker claimed that time travel may be possible inside a rotating black hole. I would imagine, though, that if you could survive going into and navigating inside a black hole you'd probably have better things to do than visit the early 21st century.
Ok, enough of that. Anyone want my physics armchair?
The idea is that the spinning black hole is 'twisting' space, pulling you around with it. Spin it fast enough and go close enough, and you're pulled around faster than (apparent) c.
Trouble with the black hole one is that the hole needs to be really massive and spinning really fast, as otherwise you've got to be so close to it that you're inside the event horizon, thus your time-travel is irrelevant because You're Not Getting Out.
Anyway, all the designs for CTC-based time machines will never allow travel back to before the creation of the time machine as it's the geometry that's allowing time travel - when you get back to when the machine was created, there's no longer a machine to take you back any further...
On the other hand, it's likely that most (perhaps all) designs for time machines are self-destructive - if a photon (or anything else for that matter) can enter the machine, travel back and then re-enter the machine, you'll rapidly (instantly?) end up with an infinite number of them travelling though the machine, thus infinite energy and infinite energy density. In other words, a singularity.
Of course, that's assuming it doesn't go properly boom before reaching infinite density.
some ideas, on time travel speculate that time travel into the past, before the time travel device was created, is not possible.
So, if on 1/1/2012 a time travel device is created, no one could come back to today and see, first hand, what is happening.
As to the article, As may have been mentioned elsewhere, while the speed limit for an object with mass is c , when the object "reaches" c the mass of the object has increased to a point where it is infinite, and hence needs infinite power to accelerate. Which is why c is the limit.
That said, there are no restrictions on APPARENT FTL travel.
For example the concept used in Star Trek's various Warp drives - they do not allow the ships to travel faster then c, they warp space bringing 2 distant points closer together, then the ship travels the now shorter distance normally.
Other hypothetical options would be:
- "hyperspace" - basically moving through a different dimension allowing the effect of FTL. This would be similar to a being able to move in 3 dimensions, to a citizen of a 2 dimensional world. Start here, disappear, reappear there.
- worm holes - similar to warp drives, a shortcut across a vast distance - ignoring getting crushed by gravity.
If you want the full article, you can currently reach it for free via Prof Du's research website:
Then you can read first-hand the section where they relate their findings to the various time travel hypotheses. Oh, hang on....
Can someone please explain what I'm missing here? OK, if you'd planned to use superluminal optical precursors as a stepping stone to a bit of autoinfanticide, I can see that you're going to feel pretty deflated right now. But not all time travel hypotheses require this effect, do they?
They're Chinese. They figured out how to do it, but they are putting out this disinformation so everyone else will stop research. Then, ONLY THEY will be the ones churning out high volumes of low quality clothing and useless plastic doodads faster than the speed of light and dominate the market, present, future, and past.
... for stealing the words out of my keyboard and forcing me to re-phrase:
In other news: Scientists to conduct studies to conclude once and for all whether a duck can in fact travel faster than The Speed of a Duck.
Mine's the one which has will have a quantum paradox in the pocket.
You don't need FTL if you can travel non-linear distance through higher dimensions.
Why travel 1,000,000 miles at c, when you can fold space-time and actually only tunnel 0.1 miles.
The former post office worker is happy, the noodley-appendaged one is happy, the string theory guy still earns his book royalties, everyone is happy.
It must be true/possible 'cos Star Trek dun it.
The pop culture stance agrees: "The Vulcan Science Directorate has determined that time travel is impossible."
The biggest take-away I received from college physics courses (not my major) is that we, as humans, are still in the proverbial dark-ages in our understanding of nature and physics. Yes, we have nukes and transistors and an LHC. We still cannot even pick apart the four fundamental forces (as we know them).
In the last 100 years, humankind has advanced more than it has... ever. We're not done advancing! For example, we have not yet picked apart how something as "simple" as gravity works. We have equations and "gravitons" as theoretical evidence. If we have it figured out, then where is anti-gravity tech?
We are simply not where we need to be, technologically, yet to even know beyond guess about something like "time travel" (at least the Hollywood version of it).
Keep in mind that the earth was also once considered flat. We now know better.
Do the Chinese?
"... but by the 13th century, people in the West believed it was flat again. Until a theory is definitively proven or disproven, it will go in and out of vogue."
By 'people' do you mean the average man in the street, or the so-called educated classes. Ever since Greek times, no textbook has referred to the world as anything other than spherical, including the 13th century textbook "On the Sphere of the World" (hint: the clue is in the title). Indeed, it is essentially impossible to perform astronomy without believing in a spherical earth.
If you mean average person on the street by 'people', then in this case let's look at today: evolution is still hotly debated; magnetism is poorly understood; quarks are in Mark Twain novels; 0.999... might not be equal to 1; and so on.
Finally, no theory can be proven, or even proved; merely it can have significant evidence in support of it.
Any mariner with an open mind knew that the world was roundish. Look at a ship sailing away, and it gradually drops below the horizon, until you can see only its sails and not its hull. Columbus was willing to stake his life on not falling off the edge. He had to be pretty darned certain in his own head.
He was also pretty certain that there were inhabited lands far to the West. Man-made detritus washed up from time to time, driven by the current and the prevailing wind, both known to be from that direction. Occasionally there would have been whole canoes, possibly containing bodies.
Quite a lot of people would have thought it was flat, or more like not thought about it at all. They were more concerned with witches, demons and such.
Any sailor who had left the sight of land and returned and anyone who had observed them would have a fairly good idea that it wasn't flat, as would many well-read people.
You beat me to it. What about tachyons? You can't accelerate to c, but if you are already in existence faster than it...
Also, the earth is flat, but its gravity distorted the space around it in a sphere!
So the light coming in or out of it is bent in a curve and any observer, Erastothenes included, came to the conclusion of a spherical planet.
Or we are trapped in Hanna-Barbera cartoon planet that wraps around, put in another words.
Also, gaining mass as you accelerate? What, do you get fatter as you speed up? Where is the mass coming from? All the kinetic energy you acquired to get that fast is spontaneously turning into mass?
Something to laugh.
And just to remind you...I'm claiming this !
There's two ways, IMHO :
The first is to actually bend spacetime, sho the shortest distance between two points is effectively zero. Many people have thought of this, so nothing new there. This is, however, NOT FTL.
The second way is exactly that. The bottleneck is ole Einsteins E+MC2. The ONLY way to get around this is to hide the mass from our universe in some way.
It requires some out-of -the-box thinking, but in due course I think it can be done. Hiding the mass would essentially forfeit the requirement of infinite energy to move the mass around.
I'm working on it...but it's slow going.
The article's spin is pessimistic and misleading. All this experiment has done is verify an axiom of special relativity for this particular circumstance. That was not unexpected.
Special relativity says that an object cannot be *accelerated past* the speed of light relative to any observer. Tachyonic theories avoid this by having objects created that are already travelling faster than the speed of light relative to an observer. Of course, tachyons are just an idea.
But we know that relativity is not the final word in physics because it remains incompatible with the other major theory, quantum mechanics. Most physicists believe we will one day have a super science or GUT that successfully encapsulates the same results we get from these two amazingly successful views of reality. Both QM and Relativity have enabled unexpected technologies that we could not dreamed about before - eg microelectronics, global positioning satellites. We have no way of knowing what insights and new technologies a GUT might produce - however the history of physics, if that is anything to go by, suggests that any major new understanding of the nature of reality will be likely to produce astonishing insights and unimaginable technologies. That has been the case throughout the history of physics. We have no way of knowing if a revolutionary understanding of the nature of time might not arise from a GUT.
So SF fans should live in hope. This experiment only confirms what we previously believed to be the case.
Stuff all that time travel nonsense, can one of the egg-heads please try to explain to me why aliens, with superior intelligence would bother coming to this burnt out rock? I mean for more than a bloody good laugh at us! They come here, land in a field next to some nutter who no one would believe, take 'em aboard their craft, stick medical implements where the sun never shines and for what? Oh, and Roswell? So aliens with stunning technology, travelled light-years to to our boring planet then crashed and died for the want of something simple like weather forecasts and some seat-belts?!
And these boffins say the universe makes perfect sense, I'm going down the pub for some real sense!
Better than that - they arrive completely undetected until they smash into the planet (at speeds they and their crafts are able to survive quite easily), weaving through vast amounts of space junk that contains our complete communications networks without touching a thing, in order to probe a single example of a soggy organism. Not very good science, stealth, or observation.
They also routinely attract the attention of locals, usually near military bases, and are written about, observed and recorded in military literature. On top of that, they also put the subject of their experiments back into the wild like nothing had happened, and their encounters always last less than 24 hours (average time away would almost always equal that of the average hangover). Where are your long-term experiments? Where are your controls? What happened to reintroducing captive subjects to their natural habitat slowly?
And why, in 170bn observable galaxies made of billions of stars each, bother with Earth - who still haven't worked out that it's probably not a very good idea to shoot each other? Go find that planet full of nubile air hostesses and retire there for the sake of science, if you call yourself an intelligent species!
Obviously some aliens turned up, had a look around and decided they didnt want anyone from *this* planet getting into space, so they replaced the entire political class in pretty much all countries with Morons who couldnt have an original thaught to save their lives. GWB, Obama, Brown, Sarcozy, Blair, Camaron, The other one, Everyone!, chucked a couple of rubber dummies in a scout ship and crashed it into Area51 to keep the nutters happy, and
Now their just all back at the Space dog and bone with some beers having a good laugh on how they pulled one over that bunch of two armed idiots on some insignificant planet thats going to murder one another Anyway.
I havent figured out how the Vatican and the Illuminatii figure into this yet, and lets face it, it wouldnt be a conspiricy theory worthy of name without giving his popeyness a promeneent role, so i could be mistaken.
You do know photons are massless, yes? It's not the mass of a photon that means it can't go faster than c, it's the momentum, which photons do have, hence the possibility of things like solar sails.
There may be other theoretical particles which have no momentum, which could travel faster than light, but then (if I remember this rightly), they'd have no energy, meaning that they could just pop in and out of existence, and couldn't interact with any other particles in any way which essentially means they wouldn't exist...
Solution, place an object in a universally unobservable state. It will both exist and not exist and therefore not be bound by observable limitations. (The Peak-a'boo-drive) - trademark
Or use the Futurama solution, by moving the entire universe around the ship, rather than moving the ship itself seeing as Space is the only thing that can move faster than light.
Also doesn’t some Scottish guy look after an engine that can do this?
no engage finger botton :(
All this experiment does is confirm that the optical precursor to a photon is still limited by the speed of light in a vacuum. No method of time travel or FTL travel has involved exceeding that speed in any case for decades - from pure fictional hyperdrives to seriously proposed topological methods (alcubierre "warp" drive), they all propose dodges to avoid needing to break light speed in the first place, and they are all still just as likely(or unlikely) as they were before this research was published.
Travel in normal space is like moving a value from one memory cell to another by sequentially moving it through each address in between - no matter how optimised your program and the CPU microcode is, you will always be limited by maximum speed achievable by your specific hardware.
However, if you can address the destination memory cell directly, your hardware limit will still apply but you will only need to do 1 jump to reach any destination, no matter how far from your starting point. All you need to do is to find the command that will tell your CPU to do that...
Mine is the one with the plaid.
I believe what you intended to say was:
'Mine is the one in plaid'
For your reference:
PLAIT - n,v - 'to plait' - to weave fibers together into a larger strand, 'a plait' - a strand of such woven fibres. AS IN: "I used to pin Margaret Tortarella's plaits to the desktop with drawing pins. Her plaits were very long; it must have taken her ages to plait them."
PLAID - n - cross-hatched striped pattern similar to a Scottish tartan; plaid is composed of arbitrary (usually horridly contrasting) colours not representing any Scottish clan. AS IN: "I notice plaid is back in fashion on the fairways this year"
Let us do an experiment.
Take a long thin inelastic rod, 186000 miles long. (Yeah, I still do Imperial on occasion).
You push it along from one end, until it bumps into something.
Now, if you feel it bump in less than a second after it bumped, then we have transmitted information faster than the speed of light.
Why should you not feel it instantaneously?
Exercise for the reader: develop this idea into something useful.
This was just a cheap Chinese copy and like most cheap chinese copies its no where as good as the real thing. In fact from what I read (and I had just got up) they had to slow the whole thing down by 500 nanoseconds just to measure it, no wonder it didn't go faster than the speed of light.
By the way is anyone else worried that the optical precursor goes faster than the photon? Does this mean we see the light before it arrives and worse still does this mean that the actual light does not go as fast as it should? If so can someone put another 50p in the meter to get it back up to speed please.
Pressure would be transmitted at the speed of sound in the rod, which depends on the material but is much slower than the speed of light. When the other end hits "something" the pressure wave has to travel back down the rod. Obviously a 186,000 mile rod can compress by quite a long way.even under mere finger pressure - probably many yards (well, you used imperial units).
Surely this was about time travelers, rather than covering vast distances at light speed? Aye, finding or creating a wormhole shortcut may be the way to flit across the universe. But time travel (excluding going forward at 1 sec / sec) either needs real FTL, or another method of achieving the same result.
Put one end of wormhole on a spaceship. Send that spaceship on a high-acceleration round-trip journey, while keeping the other end at home.
When the spaceship gets back, its end of the wormhole has existed for less time than the end that stayed home (twins 'paradox'), thus creating a tunnel that will take you forward or back the difference between the ages of the wormhole ends.
Of course, it won't take you any further back than when you built the wormhole and it might destroy itself due to a feedback loop.
Aside from that, given that we don't yet know the true physics of wormholes, the age difference might have stretched the hole so you can't take less time than the age gap to travel through it in one or both directions, the hole might become impassable or otherwise snap if one end is accelerated 'too much', or it might turn out to be impossible to move the ends relative to each other.
The last possibility would make them much less useful of course - it would be a bit of a pain having to figure out an orbit of such a structure that keeps *both* the ends in useful places.
"The only thing they have a proof of is that no known particles can travel at speed higher than the speed of light"
Since you're made up of known particles, and detection mechanisms exist (or would be possible using current engineering state-of-the-art given sufficient money) for all currently known particles and all particles hypothesised to exist, I'd say that pretty much covers all the bases for the moment.
Oh, and Aaron, the earth was only considered flat by early tribes who hadn't seen the sea. The first time you realise you can see the mast of the boat before the hull, the solution is pretty clear to a bright person. The Greeks knew it, and so did medieval people. The Greeks even had a good guess at the size. Columbus's sailors weren't unhappy about sailing off the edge of the world, they were unhappy about dying of starvation and thirst. Remember that Columbus thought he was sailing to India - had the American continent not been in the way, they would have run out of food and water well before they got there.
You cannot prove a negative. You cannot prove something will never travel faster than light because you cannot prove every single possible scenario.
You can only prove that under repeatable conditions a repeatable answer will occur.
So the research proves that under the conditions of the experiment, the speed of light was not exceeded. Had they given it a really hot cup of lapsang souchong then the outcome *might* have been different.
The Tunnel Drive? it was mentioned above by dpmaurer that evidence of tunnelling neutrinos has been seen (though not proven, as I understand it), so folding space, driving a tunnel between the surfaces, and driving down the tunnel to the other side, is not without the bounds of possibility, is it?
Troll, because I'm sure to have lit some inquisition-like nut's fuze ;-)
A *zero* rise time pulse hitting a dispersive medium is a very handy mathematical construct.
Until you try to build a machine to *make* such a thing.
Fast rise time pulse generators have various uses but all have a *finite* (10s of pS possible with off the shelf hardware, fS with exotic jiggery pokery) rise time and once the output rise above 0 V a "disturbance" *is* propagating in the medium. Weather humans can *detect* it is a problem the universe is indifferent to.
For the SF fans I'd say this is akin to the difference between radio and the "Ultrawave" communicator of James Blish's "Cities in Flight" series. Blish seemed to have a more than passing interest in relativity
Note that in the Blish universe FTL is *impossible* as well, what *is* possible is near instant acceleration *to* light speed (which would make quite a big difference anyway) and the development of affordable (and effective) anti aging treatments.
Everything is moving.
To successfully travel in time/FTL one has to calculate exactly where one is relative to where one wants to be taking in to account: rotation of the planet(s), orbital track of planet(s), motion of solar system through space, etc.
Otherwise one ends up in deep space without a pressure suit (which is not good)
or one ends up parking one's spaceship inside a sun or planet (which is also not good).
leads me to believe time slows near the speed of light, and stops at the speed of light (thus IMHO light is a wave of fixed energy quanta frozen in time and so acts like a particle, but i digress...) so theoretically we can travel vast distances and not age, our relatives however would be long since dead by the "time/space" we reach our destination, having effectively travelled forward in time... now travelling backwards in time, well...
I was thinking this while watching the Back To The Future series.
Either the prof. carefully calculates the rotation, orbit and every slight variance of the Earth such that the DeLorean lands at roughly the same spot, or perhaps he can only go back and forth by a 365.25 day intervals?
Also, what if the DeLorean (in the first film prior to the anti-gravity mechanism but could also apply to the 3rd) was on the same road, but it had been tarmacced several times such that the tyres are now embedded a couple of inches into the road? Or what if it had been landscaped as an onramp for a motorway? What if in the 3rd film the rail bridge had swayed a couple of inches?
Only John Titor has the answers. Give him his IBM computer.
Isn't there some theory somewhere that the universe is expanding at faster than light speeds? Which if true, would put this nothing goes faster than light speed theory in a box and bury it!
Oh and to the person who says we don't understand gravity, we do!
Simply put it's the force exerted on speace time by the mass of an object sitting on it.
I'm sure I read something that speculated that the characteristics of one of the stranger sub-atomic particles (neutrinos? tachyons?) could be explained if they were traveling backwards in time. This would explain why they interact so infrequently with ordinary matter.
Anyway, if a time traveller from the distant future were to travel back to the present it is very unlikely that we would be able to understand them. Unless of course they have the universal translator although I think even this would struggle to translate words or phrases which came into use in the future into equivalent present day terminology. For example what would be the the 16th century translation of the 20th century phrase 'integrated circuit'?
If you have listened to very old voice recordings you will have noticed that accents were very different and the grammar was slightly different to. The language keeps evolving which makes things difficult for time travellers to fit in. You would only need to get the time wrong by a couple of years to really stand out. Imagine some one turning up today with a Beatles hair cut and saying "Fab" and "Groovy" a lot....
From the manual:
As it would take the light from the headlights twice as long to travel to any obstacle and be reflected back as it would to crash into the obstacle, headlights are disabled by the onboard computer at c/2.
Thankyou for choosing the Vauxhall Astramax van.
The Speed of light is only relative to the time it takes to travel the distance covered. We dont really need to travel faster than light, we neeed to slow time down only for the observer so that relatively espeaking verything appears to be going faster.
Thats why I'm a proponent of Shmysics. The study of how various plant extracts when burned and the resultant fume inhaled, can be used to slow down time aswell as other things like brain function. :)
C isn't the speed of light, C is the speed of a massless particle. As far as we can tell, a photon is massless, so the two tend to be synonymous. If we should ever determine that a photon does indeed have mass, C will still be the limiting speed; it'll just be a different "mass less" particle.
It would be very hard to disprove the hypothesis that the "wave front" isn't moving faster than light as has been mentioned that it may result in the effect hitting at exactly the same time as it moved itself very slightly backwards in time to sit exactly where it was before exceeding lightspeed.
A photon can't go faster than the speed of light. This is an obvious statement. It's like saying a rock can't accelerate faster than acceleration of gravity when dropped in a vacuum. No kidding. He just proved that a constant is really a constant. However, just because a photon can't outrun itself doesn't mean something else isn't faster. Or, that the rules can't be bent under influence from outside sources.
Our biggest problem here is perception. We cannot perceive anything faster than light, therefore proving anything exists that travels faster than light is almost impossible. Until we are able to observe something traveling faster - either through direct or indirect observation - there will always be doubt to the possibility. All we will have is some math on a page to argue over. So, I submit to you the possibility of another X-Prize. The first person to be able to conceive and build a device or experiment to detect tachyons. Give them a million dollars and see what happens.
China recently banded any book, movie or television series that deals with time travel and alternate universes. This feels like science trying to prove a government edict for political favor - or because there was a gun to his head. Either way, saying that time travel is impossible is bound to be pointed at by the Chinese government as their proof that entertainment of this type is a waste of time and should be band.
Nothing new here - scientific dogma always insisted that nothing can travel faster than the speed of light (including light).
But not to be outdone, scifi writers came up with the concept of space 'wormholes' where somehow one is able to punch a hole through normal space time, at which point 'something' is created where conveniently the rules of normal space time do not hold.
So the question has to be - is it possible to create, for want of a better description, an a-la-carte wormhole?
Hmmm... Auntie's site claims that in some instances some researchers witnessed superluminal effects. So both cannot be true.
However, I think the unknowns (or even errors) in physics are more abounding than we realize. Example:
1) Light cannot escape gravitational pull of a black hole within a certain distance
2) Gravity laws are based around mass
3) Light has no mass, only relativistic mass caused by the fact it is pure energy moving.
Leaving the question: how does gravity operate on something with no mass?
Photons are electromagnetic so I would suspect that the effect of a black hole on light is down to electromagnetism, not gravity, or that at least, gravity is an electromagnetic affect attributable to gravitons.....
... but I guess I should get back to writing software and not wondering what would have happened if I opted for the physics degree instead. This anti-grav device of mine is coming along nicely though ;)
From General Relativity mass/energy bends spacetime - anything moving in spacetime follows the bend.
It was the first test of General Relativity.
The more mundane one happens everyday as GPS clocks are set to correct for various time mangling effects due to velocity/gravity
The research doesn't imply that ALL time travel by any method is impossible. Rather it says that faster than light time travel in a flat space vacuum is not possible. But this doesn't imply that time travel is impossible through other means such as, closed time loops in space, wormholes, space warp drives, Tipler rotating cylinders, etc. There are many schemes for theoretical time travel where all objects travel slower than the speed of light IN the Local Reference Frame, yet the objects that move backwards in time.
1 When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
2 The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
Time travel is possible! If you move a particle fast enough it can travel forward in time at a faster rate (Time Dilation). So, to clarify, what the researcher said is that travel BACK in time in a flat vacuum is not possible. There are many schemes that may overcome this limitation, wormholes, closed time loops, Tipler Cylinders, etc.
Search for Time Travel on Wikipedia, good article.
What it comes down to is that without a quantum theory of gravity we cannot determine with certainty whether or not such schemes are possible.
AFAIK, time travel* is not dependant on the ability to travel faster than light. Merely, faster-than-light travel was seen as the easiest way to travel back in time. We'll just have to find an other way, is all.
*actually time travel is easy as pie really. I myself achieve a quite reasonnable speed of 60 spm (seconds per minute). I can slow down, too, with only the help of a Vista install disk. Acceleration requires fuel -typically ethanol, but other substances are said to work too- much like you need nitrous oxide to lose the highway patrol. Haven't found the reverse yet, though a heavy use of the aforementioned fuels can apparently produce random jumps in either direction. Close enough for me.
"It's not comedy racism. It's a well-known fact in science circles that the best and brightest in China (and not just China, but many countri..."
If you do a bit or research you'd find that HK UST is a very highly placed university in world rankings. Many of the professors there are from Havard and other top universities.
This is in HK too remember, not mainland China.
There are a number of perfectly serviceable time machine designs that do not involve a photon exceeding a velocity of c. Larry Niven wrote a story based on an actual scientific paper awesomely titled "Rotating cylinders and the possibility of global causality violation" about one such design. The late Robert Forward also wrote about a few designs. However most such require certain types of exotic matter - either negative matter. or large quantities of neutronium or similar.
"In a statement (available here in Chinese) dated March 31, the State Administration for Radio, Film & Television said that TV dramas that involve characters traveling back in time “lack positive thoughts and meaning.” The guidelines discouraging this type of show said that some “casually make up myths, have monstrous and weird plots, use absurd tactics, and even promote feudalism, superstition, fatalism and reincarnation.”
The guidelines, which fell short of an outright ban of such dramas, seem to have come in response to a series of popular programs about protagonists drifting back to ancient times. "
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