There ’s been a lot of hubbub about the opening of FTL neutrinos . But would break the light barrier really be such a self-aggrandizing bargain ? Hell , yes , it would ! In this week ’s “ Ask a Physicist , ” we ’ll find out why .
While I normally attempt to deviate subject from column to pillar based on thequestions you send me , we ’re going to keep the treatment from my last on pillar onfaster - than - lighttechnology .
What are your scene for bring forth a faster - than - twinkle drive ?
Why the change ? A few weeks back theOPERAexperiment announced that they had apparently quantify neutrino travelingfaster than lightsome . There was an enormous amount of excitement , both here and elsewhere , but also a lot of skepticism . My status : I’m not buying it .
Scientific discovery : Physicists at CERN have put down particles move faster than light
quicker Than Light Neutrinos ? Not So tight
But are faster than light particles really such a big stack ?
They sure are . FTL communication results in nothing less than being capable tocommunicate to the past , and produces all of the complexity and paradoxes of sound sure-enough fashioned metre travel .
Jason Honanasks :
Even if the communication took place instantaneously , I do n’t see how one would use that to communicate with one ’s own past times . Can you explain it in plain English ?
Specifically , Alice and Bob need to chat , Bob sends a content and N seconds later , Alice sends a response . Even if the passage sentence for the message were zero , N seconds have still elapsed for both individual . How does a superluminal transit upper equate to minus elapsed meter ? Would n’t , at serious , a subject matter have a zero delay ? ”
This column ’s blend to be a second dissimilar than the normal “ call for a Physicist ” fare . While it ’s not going to employ equating per se , I will put in a few diagrams . However , if you really want some equations , a more technical adaptation of this discussion appears inmy web log .
A Simple Tachyon Telephone
Suppose we ’ve managed to educate a beam that jaunt across vast distances at faster than the stop number of light source . On the aerofoil , this is incisively the result announce by the OPERA experiment , sinceneutrinosare so weakly interact that they can easy travel interstellar space without interacting with anything .
require a Physicist : Can I build a doomsday gimmick using neutrino ?
While the OPERA measurement only paint a picture that the neutrinos travel at something like 2 theatrical role in 100,000 quicker than the speed of lighting , but basically , once the light barrier is transgress , then it ’s only a subject of fine tuning to get any superluminal hurrying we wish . For our determination , I ’m going to speculate we have atachyontelephone which sends signals at 4 fourth dimension the upper of light . ( Again , I do not believe that the OPERA outcome will pan out . I just wanted to make that clear ) .
Jason and I suffer 1 light - second from one another , and send each other messages . Normally , igniter would take 1 second to journey that distance ( by definition ) , but since we ’re using our tachyon beam , the signal gets send in only a quarter of a second .
In a so - called“spacetime diagram ” , a snippet of our conversation would look like this .
The bold lines show where Jason and I are at any given time . Since we ’re standing still , we move through sentence , but not through outer space . The diagram tells a very boring story :
I send Jason a subject matter .
He receives it and sends me a signaling back
I receive his subject matter .
And what do you know ? Jason was exactly right ! I get his response after I send my original subject matter .
But once we start motivate , thing get far more interesting .
Moving transmitters
Einstein ’s Theory ofSpecial Relativityis based on two fairly mere assumptions :
What come about If You ’re Traveling At The Speed Of Light And Turn On Your Headlights ?
There ’s absolutely no differentiation between somebody moving at a constant amphetamine and focus , and somebody stand still .
Everybody will value thesame speed of light , regardless of their state of motion .
The trouble is that for both of these things to be true , mensuration of clock time and blank are very strongly related to to your land of motion . We go through this with hobos in Chapter 1 of the“User ’s Guide to the Universe , ” , but the effect is this :
Moving clocks always seem to run slow .
Under normal circumstance , this is n’t a big deal . A car subspecies by you on the main road at 100 miles per hour , for example , and the dashboard clock only seems to campaign easy and the equipment driver historic period more lento than you do — but only by about 1 part in 10 ^ 14 . Even if he force around for a hundred years , this only add together up to a delayed aging of about 30 microseconds .
But if we ’re traveling a unspoilt fraction of the velocity of light , thing become very different . This is the origin of the“twin paradox,”where one Twin Falls stays on world , and the other goes on an interstellar adventure . When the travel matching return , she finds that she ’s aged far less than the stay - at - home twin . But since she ’s been peril to tons of grave cosmic rays , her vernal good feel are something of a Pyrrhic victory .
This Animated Video Simplifies Einstein ’s Complicated Twin Paradox
It turns out , though , that we ’ll be able to overwork dissimilar local clocks to make a phone call — ( cue dramatic medicine ) to the past times !
An Anti - telephone
So here ’s the trick : Suppose we ’re fly away from each other at half the speed of lighter , and , just to make things concrete , he and I can send tachyon beams to one another with almost infinite swiftness . If you ’d like to see what happen if the signal is just faster than sparkle rather than immeasurably tight , please check out theequation - ridden reading .
Jason and I fly past each other in our spaceships and 1 1/2 seconds later ( a time chosen to make the diagram look skillful ) , I send him a message .
Here ’s the weird part . Even though 1.5 seconds have slide by on my clock since Jason and I passed one another , because of this whole “ time dilation ” thing , only about 1.3 endorsement glide by for him .
In and of itself , this is n’t such a big deal . After all , if Jason charge me a communique by ceremonious means — wireless sign , perhaps — I ’d still get it after I sent him my original subject matter .
However , once we look at thing from Jason ’s perspective , they start to look seriously messed up .
recollect that Einstein tell us that there ’s no elbow room to narrate who ’s stand still and who ’s move . Just as I think Jason ’s alfilaria are running slowly , he thinks he ’s stomach still , I ’m fly to the left , and that my clocks are running slowly . Yes . This is one of the many crazy headaches that follow from relativity .
From Jason ’s perspective , the 1 1/2 second that fleet before I sent my first signal is more like 1.7 second gear . In other words , I institutionalise the sign after he received it .
Jason then sends me a reply . It could be something as dim-witted as , “ Do n’t call me ! ” He transmits it in a flash back to me .
From my perspective , I get his response before I ever post out my original message and , if I ’m not a huge fan of causality , presumably could forbid me calling him in the first position . In other words , we ’ve go a serious paradox on our hands .
This is nuts ! The simple ability to send signals faster than light would allow us , in a very real style , to strike the past times . And that my friends , is why the prospect of faster than lightsome neutrinos ( or anything else for that affair ) would be such a world - changing discovery .
Dave Goldbergis the writer , with Jeff Blomquist , of“A User ’s Guide to the Universe : Surviving the peril of Black Holes , Time Paradoxes , and Quantum Uncertainty . ”(follow us ontwitter , facebook , twitterorour web log . ) He is an Associate Professor of Physics at Drexel University and is currently work on a fresh Holy Scripture on symmetry . palpate free to get off email to[email protected]with any questions about the universe .
Top illustration by R.T. Wohlstadter via Shutterstock
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