
Faster Than the Speed of Light? - zzzeek
http://www.nytimes.com/2013/07/23/science/faster-than-the-speed-of-light.html?hp
======
lisper
The right way to think of this: the speed of light is not a speed limit, it's
a speed _reference_. Everything is always moving at the speed of light through
spacetime. When you "move" through space, you're not changing the magnitude of
your velocity vector, only its direction. So the more you move through space,
the less you move through time.

If you could move through space at the speed of light your velocity through
time would be zero and you would appear (to yourself) to be moving infinitely
fast, or equivalently, to be everywhere at once, or (again equivalently) that
the universe had no spatial extent in your direction of travel due to an
infinitely large Lorenz contraction.

~~~
TomGullen
I really really want to understand this, but I can't get past your third
sentence. No fault of your own, just me. But if you have anything I can read
that explains it better I would be grateful!

~~~
ramidarigaz
Here's an illustration, if it helps:
[http://imgur.com/YrlKW4Z](http://imgur.com/YrlKW4Z)

The length of the red arrow is always the same. When your velocity is zero,
your "time speed" is 1.0. As you begin to move faster, the arrow tilts towards
the X axis, decreasing your "time speed".

~~~
ars
It's not a great way of describing it though.

The biggest issue is that the interchange between speed and time is not
linear. So that graph doesn't make sense as displayed.

At a minimum you have to understand that the time scale on the side of the
graph is not linear, but rather exponential. And graphs with exponential
scales are not easy to understand.

Making it worse is that there are other things that can slow down time -
namely acceleration.

~~~
ramidarigaz
Oop. You're right. I overlooked that. I put about 2 minutes into the
illustration and didn't think it over very much (I probably should have).

I was mostly responding to TomGullen's confusion about the GP's statement,
rather than trying to paint a super-accurate picture.

~~~
ars
I wasn't really criticizing you as much as the concept of describing
relativity as a tradeoff between the two. I don't think that helps enough to
overcome the misunderstandings it can cause.

------
acjohnson55
I read about this months ago, and it's an interesting idea. I'm not a
physicist, but I spent some time trying to puzzle out how this fits in with my
understanding of relativity. So please, correct any misunderstandings.

It's important to realize that the craft is never traveling faster than the
speed of light through the space in front of it. But there's nothing in
relativity that prevents objects from apparently traveling faster than the
speed of light "after the fact". The farthest apart objects that we can see
are significantly further apart in light-years than the estimated age of the
universe, which is generally thought to be possible because of the expansion
of space itself as objects were traveling apart at subluminal speed.

I don't think that apparent FTL travel violates causality because it doesn't
allow you to actually reach anything outside of your light cone. It took me a
while to understand this, but you can't really view the light cone as
something that is statically determined at a given point in time, because it
depends on the geometry of space as over time. So a craft capable of
distorting space just ends up with a really funky-shaped light cone that's
warped wider than normal out in its direction of travel and narrower in the
opposite direction as it moves (if you had a way of externally viewing the
curvature of spacetime, which you don't).

But one thing I could not really figure out is whether this so-called FTL
travel has the potential to violate causality, because I don't fully
understand how causality and FTL are related.

~~~
btilly
_But one thing I could not really figure out is whether this so-called FTL
travel has the potential to violate causality, because I don 't fully
understand how causality and FTL are related._

The relationship is that FTL in one reference frame is travel backwards in
time in another.

If you're able to travel FTL in 2 different inertial reference frames, then
you should be able to travel backwards in time and violate causality. Note
that the "should" here is important - I can think of lots of possibilities for
how that should could be prevented.

That said, I'd be much more optimistic about the plausibility of a proposed
warp technology that only lets you go FTL relative to the implicit reference
frame of the distant stars. Because that avoids any possibility of causality
violation.

~~~
shardling
>That said, I'd be much more optimistic about the plausibility of a proposed
warp technology that only lets you go FTL relative to the implicit reference
frame of the distant stars. Because that avoids any possibility of causality
violation.

I don't understand what you're getting at. It would be trivial for someone
close by to match that reference frame, and then what?

~~~
btilly
_I don 't understand what you're getting at. It would be trivial for someone
close by to match that reference frame, and then what?_

And then nothing. :-)

My point is that being able to go FTL relative to distant stars does not allow
time travel relative to distant stars, which means that there is no
possibility of causality violation.

Being able to go FTL in 2 arbitrary reference frames leads to potential
causality violation.

~~~
shardling
It's still not at all clear to me what you're saying.

Feel free to express yourself in more technically/mathematically: while GR is
certainly not my field, I took classes in grad school that covered the
material.

~~~
btilly
This is a point about SR, not GR.

In SR, if A and B are two events and B is outside of the light cone of A, then
reference frames can be found where A happens before B, A and B happen at the
same time, and A happens after B. Therefore FTL travel in one reference frame
is traveling backwards in time in another.

The ability to travel FTL in a single preferred reference frame is not
sufficient to cause causality violations. That is because all trips move me
forward in time according to the preferred reference frame, so I can't wind up
at the same time and place that I (in my personal history) was at before. But
if I can travel FTL in my choice of reference frame, in my choice of
direction, then I can plan a trip from A to B which is FTL in one reference
frame, then switch and travel from B to A FTL in a different reference frame.
From the original reference frame I first traveled FTL, then backwards in
time. In the second reference frame I first traveled backwards in time, then
FTL. But both agree that two copies of me wound up at the same place at the
same time, and I can try to violate causality.

Suppose that you go from SR to GR but are dealing with a large region that is
approximately described by SR though locally it may look different. In my
"warp drive" there is no local FTL. But the observations about SR, reference
frames, and simultaneity still hold between two distant locations. The ability
to warp as fast as I like but only relative to one "approximate SR reference
frame" does not let me violate causality. But the ability to do it in any
direction relative to any reference frame that I like, gives me the ability to
construct "closed time-like loops". Which is what is required to try to
violate causality.

Note that I say "try". It is possible that a unified theory of GR and QM could
allow for closed timelike loops, but (thanks to quantum decoherence) would not
allow you any meaningful interaction with the previous copy of you.

------
Steuard
I hate to put a damper on the enthusiasm about this awesome topic, but this
article doesn't even contain a hint of any reason to believe that the NASA
scientist in question is making progress on any sort of FTL technology.

Alcubierre's work on "warp bubbles" has been known for years, but as even this
article points out, there are _enormous_ roadblocks to making it practical.
For example, it requires matter with properties that have never been observed
in the universe (namely, violations of the positive energy condition). If this
NASA scientist thinks that he has a way to produce such matter, that would
already be a bigger deal than any scientific finding in (conservatively) the
past thirty years. Why hasn't he announced _that_?

Also, Alcubierre himself is quoted in the article pointing out that no signal
from inside the warp bubble can ever reach the front of the bubble to "turn it
on" in the first place. (As I recall, Alcubierre's equations describe an
"eternal" warp bubble, moving forever with no beginning or end.) Has the NASA
team found a way around that? The article doesn't give any hint that they
have. (Nor that they haven't, but as a theoretical physicist myself I'd like
to think that I'd have heard of a breakthrough like that.)

So what I want to know is, first, why did the NY Times decide this was worth
reporting on (while leaving out any evidence that this NASA team is capable of
making meaningful progress)? And second, why is NASA devoting multiple salary
lines to this particular project? (There might be good answers, but they
aren't evident here.)

~~~
kamaal
>>For example, it requires matter with properties that have never been
observed in the universe (namely, violations of the positive energy
condition).

At first I thought about this, but then its for us to really ponder on a
simple fact. You can achieve a X goal by doing Y, but to say you can achieve
only by doing Y is wrong.

Scientific history is standing testimony to that. People have expressed
skepticism about anything and everything, stuff like airplanes, nuclear
energy, mobile phones, internet anything you name it. 50 years before they
were all invented and put to use, they would have all seemed pointless
directions of pursuit- yet all of it makes perfect sense today.

Yet some tangential line of thinking causes a major technology break through
every now and then we are left wondering what we where thinking all along.

~~~
2muchcoffeeman
Remember that the people who make these discoveries are scientists. It's one
thing for a person on the street to be skeptical it's another thing when a
scientist in the field in question is skeptical.

Now these guys don't even have a hypothesis on how to turn the machine on.
Forget the engineering. They can't get an idea to work. I'm with the GP, this
is not very exciting. Even having a working idea on how all the parts may work
would be more exciting than this article.

~~~
kamaal
>> It's one thing for a person on the street to be skeptical it's another
thing when a scientist in the field in question is skeptical.

No, Scientists are human beings too. And the fact is, a scientist's thoughts
are biased based on what the person knows.

People co relate the events to happen in future on the basis of what they know
right now. Which is the root cause of all problems. Though sometimes
skepticism is perfectly valid.

>>Now these guys don't even have a hypothesis on how to turn the machine on.

These guys are not working on building the machine.

>>Forget the engineering.

Exactly. The first rockets were not built by directly opening up the lab and
making the prototype in the first hour.

Even while building things like the first rocket, or the first viable airplane
a lot of math and physics work had to be done. Which is what is happening now.

>>They can't get an idea to work.

Seems like they already have experimental test bed to verify their math.

>>I'm with the GP, this is not very exciting. Even having a working idea on
how all the parts

I'm excited. Its not like software where you fire up your IDE and just get
down to coding. That works with software because 100% of whatever we do is
already done and proven by nearly everybody else. We just exercise the same to
our domains of business.

Building some thing like a warp-drive may very well require some years of work
on math and physics before any field trials are started. Basically nobody has
done anything like this every before. No one knows the consequences, or the
side effects or even the kind of effort such an endeavor would demand.

If you want an easy analogy, Alonzo Church died finishing his work on the
lambda calculus before he could see a working electronic computer. Same could
be told about Alan Turing. Yet these guys had mathematically demonstrated all
they said was possible.

When the first gates were built, people expressed the same skepticism if the
combination of these AND-OR-XOR gate will ever achieve something substantial.
Or when the first brick was built, and when the first wheel was built.

------
ams6110
I found the comparison of the iPhone to a "Star Trek" communicator a bit off
topic. Even 40 years ago, I don't think anyone would have argued that
something like an iPhone would be possible in the future. The idea didn't
violate any known physics. Hand-held two-way radios were already commonplace.
The fact that we achieved sufficient advances in circuit miniaturization and
battery technology to build a hand-held smartphone does not in any way imply
that we'll be able to build a warp drive for a spacecraft.

~~~
dclowd9901
How about 60 years ago? 80? 100? At some point, if I explained to someone that
I would be able to pick up a small black plate filled with electrical signals
(ha!) flying around it many million times per second and use it to learn the
answer to any question, talk to (AND SEE) any person in the world, in real
time, how far back would you have to go to hear "that's impossible," because I
guarantee you, at some point, someone thought that it was, even if not 40
years ago.

Hell, I remember explaining to my dad when I was a kid that someday there
would be a way to watch whatever you wanted, whenever you wanted, simply
because that's what people wanted to exist. In my mind, it was an
inevitability, and he felt it would never happen. This was only a scant 20 or
so years ago.

~~~
lmm
>At some point, if I explained to someone that I would be able to pick up a
small black plate filled with electrical signals (ha!) flying around it many
million times per second and use it to learn the answer to any question, talk
to (AND SEE) any person in the world, in real time, how far back would you
have to go to hear "that's impossible," because I guarantee you, at some
point, someone thought that it was, even if not 40 years ago.

As soon as we have real science (i.e. post-Descartes) anything mechanistic
seems possible. There was probably a point at which we had insufficient
knowledge to say one way or another, but this isn't the kind of thing that's
ruled out by physical law in the way that FTL travel is.

>Hell, I remember explaining to my dad when I was a kid that someday there
would be a way to watch whatever you wanted, whenever you wanted, simply
because that's what people wanted to exist. In my mind, it was an
inevitability, and he felt it would never happen. This was only a scant 20 or
so years ago.

You were lucky that time, but it's not a reliable heuristic. Plenty of people
want to be immortal, but it hasn't happened yet. (OTOH, human immortality
seems a lot more plausible than FTL travel - we can't see how it would work
yet, but there's no law that rules it out - which puts it in the same category
I think a phone would have seemed like in Newton's day).

------
wikiburner
This fascinates the hell out of me.

It's simultaneously infuriating and awe-inspiring that something that's
visible to the naked eye - stars - could be so completely out of reach for us.

However, with the recent work of Drs Alcubierre and White, it's clear that
cracks are forming in the _Impossibility_ of FTL travel.

That leads me to believe the FTL is inevitable, because in the history of
science, whenever we begin to see how maybe something could kinda, sorta,
maybe exist, it's usually just a matter of time (perhaps centuries) until we
crack it.

~~~
VLM
"because in the history of science, whenever we begin to see how maybe
something could kinda, sorta, maybe exist, it's usually just a matter of time
(perhaps centuries) until we crack it."

Like mermaids, magic, the halting problem, ESP, and religion?

~~~
yk
> mermaids

A matter of advanced genetics. ( See C. Stross "Neptune's Brood" ;)

> magic

"Any sufficiently advanced technology is indistinguishable from magic." Arthur
C. Clarke

> the halting problem

Any super Turing machine that can calculate busy beaver is sufficient. ( And
creates a halting problem of its own.)

> ESP

Let me guess, live TV does not count?

> religion

I am pretty sure that we developed organized religion eons ago.

~~~
eli_gottlieb
I do wish to note as a matter of my own expertise that we don't have super-
Turing machines.

------
VLM
Lets have some fun with implications of FTL other than the usual cookie cutter
"scifi" narrative. There's not much new in the article, lets cook up something
really new here.

First of all FTL travel involving information transfer would have some
interesting implications for the existing automated market high freq trading
systems. Your proximity to the central clearing house no longer limits your
profits. In fact the whole concept of HFT and a central clearing house and "A"
individual market price might no longer have much meaning in that kind of
economy. And that might be good, or bad, or not matter much.

Another aspect given ridiculous paranoid military industrial complex would be
anything capable in theory of eventually delivering an a-bomb would be
classified and hidden until an area defense exists. In fact a rational
participant in MAD would immediately nuke any MAD member who got "close" to
inventing actual FTL because they would insta-win any MAD scenario, therefore
bomb them before they FTL bomb us. Aside from any direct weaponization of FTL
"things" materializing in .mil owned reactor cores or .mil strategic targets.
Shields materializing at FTL speeds in front of the laser beam headed toward
the target. FTL drones to spy on people so quickly they're out of range before
the target sees they were there. Yeah I think the first country to develop FTL
will probably get nuked by everyone else, unless the discoverer is legendarily
neutral (the swiss?) or ... Which would suck if the USA "wins" because it
means I'd be getting toasty unless every other nation is suicidal and refuses
to strike. Bummer for me and the rest of the usa. So I sincerely hope this
dude fails.

Another interesting aspect vaguely hinted at in Ian Banks culture series is a
FTL-ish universe culture by its very geography/technology inherently ends up
much more libertarian than our own rapid descent into "1984". So there's
interesting political issues where any group of modern "pilgrims" can at will
escape the clutches of the evil empire. On the other hand small festering
groups of true believers like to fanatically drink the koolaid, so I donno
whats worse, one evil empire or a billion little clans of crazies all
disconnected from each other.

Patent something and transmit the patent FTL such that you can deliver a cease
and desist at FTL speeds before a non-FTL player even gets to see they've been
checkmated?

------
ufmace
This is like 50 steps ahead of anything that's actually happening, but I have
to wonder what the potential destructive power of a warp-drive style FTL drive
is. If you can create a spacetime distortion strong enough to move a ship
around at FTL speeds, what happens when that distortion gets anywhere near the
Earth? Will it cause some sort of total destruction to an enormous area?
Change the orbit of the moon, the earth, asteroids? It would have a big effect
on how any ships with such a drive are used. It could be sort of like SSBNs,
where only major governments have them, and they only allow extremely senior
and trusted people to operate them.

~~~
Udo
Yes, it would likely be very destructive - however, once you have massive,
fast ships moving around the solar system the Earth will be in danger anyway,
warp-tech or no. I think it's too early to speculate meaningfully about safe
distances and danger levels when it comes to this technology, which as you
correctly presumed doesn't exist yet.

The press is hugely missing the point when they steam ahead using nonsense
StarTrek analogies without an apparent clue of what's (im)possible with
today's technology, but neither are the people in here getting it who are
stuck lecturing each other about causality violations. This is not about speed
or acceleration, or even the transmission of information. It's about bending
space time. Let's not forget the enormity of that concept, but let's also
admire this potentially useful shortcut that might open up for us in the far
future.

Current models are purely theoretical and work on a basis that is pretty
similar to carrying a black hole around. Needless to say, in an age where we
don't even have the energy to reach Earth orbit economically, the power
requirements of such a technology are nothing but prohibitive.

But even if we had enough power (and hence mass) to warp space by brute force,
it would be a huge event that needs to happen far away from planets. While the
general principle is interesting, I think what we lack is a more sophisticated
method of modifying the properties of space time, something that works on a
smaller scale and can be more easily contained. "FTL" neutrinos were
interesting for this exact reason (before they sadly turned out to be a
measurement error) because they would have opened a door for us to access and
manipulate space itself without having to resort to enormous and ultimately
wasteful energies. I sure hope we'll discover how to do that in time.

~~~
stan_rogers
That, and the potential for damage to space-time in general, were explored in
Start Trek TNG. That's one of the things I liked about the series: the things
that were invented as plot conveniences often had implications that themselves
later became plot drivers. (Not always, of course. It was entertainment, not
science. But often enough.)

------
ChuckMcM
Kind of curious what other effects you might get if you localized a change in
space-time. Given that the planet and the solar system are in motion would it
deflect in the direction opposite that motion? If so could you put better
numbers on how much inflation occurred post big bang?

------
aufreak3
For those looking to grasp relativistic physics, checkout the game "A slower
speed of light" [1] and "spacetimetravel" [2]

[1] [http://gamelab.mit.edu/games/a-slower-speed-of-
light/](http://gamelab.mit.edu/games/a-slower-speed-of-light/) [2]
[http://www.spacetimetravel.org/ueberblick/ueberblick1.html](http://www.spacetimetravel.org/ueberblick/ueberblick1.html)

------
russell
I would dearly love to see FTL, but to paraphrase Fermi, where are the aliens?
The first civilization that gets FTL would colonize the galaxy before any
other developed. It's harder for me to accept that we are the first
technological civilization than it is to believe that FTL is possible.

~~~
kamaal
The universe is far too big. I mean its really really big. Even if we acquire
FTL, lets say in the next decade(for assumption's sake) and start traveling.
Its possible given our resources, time and required focus to achieve anything
meaningful we may not even step out of milky way for several thousands of
years from now.

The milky way has around 100 billion stars. Searching 100 billion stars for
some meaningful results is not a Joke. Even if we do divide and conquer or do
the equivalent of map-reduce approach to exploring space. There is no way we
can get to meaningful results even in several thousands of years from now.

There fore the biggest challenge after the invention of FTL will be how
quickly we can multiply spread and explore.

Trust me once we get FTL technology, the biggest challenge will be the dealing
with overwhelming size of universe. In fact just within a few years we may
even think FTL was an easy problem to solve. Our problems will be exploring
the universe within human life timescales, multiplying fast enough to occupy
and explore it.

So an alien civilization in some really far galaxies even with FTL technology
possibly cannot search for us in the size the universe is.

------
DanielBMarkham
I'd love to see some big-league X-Prize money around this. You don't even need
working tech. Just demonstrate that it's possible.

It would change everything. Especially if Kepler announces a boatload of stars
with perhaps-habitable worlds around them.

~~~
wikiburner
Yeah, that's been my billionaire fantasy for a while now. The goal line could
be just a design that a panel of esteemed physicists and engineers deems
workable.

------
ColinWright
Single page:

[http://www.nytimes.com/2013/07/23/science/faster-than-the-
sp...](http://www.nytimes.com/2013/07/23/science/faster-than-the-speed-of-
light.html?_r=0&hp&pagewanted=all)

~~~
strathmeyer
Still get "YOU’VE REACHED THE LIMIT OF 10 FREE ARTICLES A MONTH."

~~~
ColinWright
Did you try following the suggestions in reply to this comment:

[https://news.ycombinator.com/item?id=6086017](https://news.ycombinator.com/item?id=6086017)

------
VLM
An interesting tech startup idea.

If you can transfer things/information faster than light, then link-state
routing protocols no longer would have a meaning in a network containing at
least some FTL links. Therefore some startup should create an internet scale
distance-vector routing protocol. OSPF is dead, long live RIPv4 or whatever.
Cisco would be an obvious candidate to purchase the startup. Obviously demand
would depend on FTL deployment rates.

I'm only half kidding, I think...

------
geuis
The question that occurs to me much later is what are the naturally occurring
phenomena that hint toward these physics? As far as I know, as an interested
layman, is that all experiments can be equated to events happening somewhere
in the universe. Everything from black holes to supernovas act like massive
particle accelerators. Are their any hypothetical situations that are similar?

------
lnanek2
Article seems a little misinformed. It claims you couldn't sent a signal to
the front of the ship to turn the drive off, but the whole point of the drive
is that, within the bubble, nothing is going faster than the speed of light.
It is the stretching and compression of space time outside the bubble that
moves the ship.

------
Arnor
I can only assume death greets anyone inside this hypothetical device.

~~~
freehunter
That's what people said about cars travelling faster than 20mph. The human
body just couldn't withstand that kind of speed.

~~~
bennyg
It's always the acceleration that matters.

~~~
freehunter
And how sudden the stop is.

~~~
jrarredondo
Which is what bennyg said, except in negative numbers.

~~~
Arnor
This has nothing to do with acceleration. The idea is that you bend space-time
so that you experience movement of a relatively short distance but actually
travel hundreds of light years. In order to do so you have to alter space-time
as we know it. Just a few weeks ago, we found we don't even know what happens
at the edge of our own solar system. How can you think that bending space and
time will act the same way as driving faster in a car? Your experience could
be movement in the range of a few KM, but in the end you could be light years
away. The problem (and the reason you will surely perish if you try it) is
that you need to change the way space and time fit. Go ahead and try it, just
be a few hundred light years away first so you don't ruin our perfectly
functional solar system.

------
eli_gottlieb
There is precisely one thing in this article that was scientifically
interesting: pointing out that Nature has inflated space at apparently-
superluminal speeds before.

------
s_q_b
How does one generate the negative mass necessary to warp space-time?

------
pitiburi
link to the article without paywall?

~~~
justanother
Chrome: Right-click, Open Link in Incognito Window

~~~
psbp
or clear your cookies. It's probably a good idea to delete your cookies on a
daily basis.

------
fragsworth
> Harold G. White, a NASA physicist, gets ideas for his warp field from a Star
> Trek starship concept.

It is ridiculous to think that physicists get any ideas from science fiction.
It happens the other way around. All he did was use it in a presentation. I'm
nerd raging like hell here.

~~~
simmons
I don't know how much inspiration Star Trek provided in this case, but it's
not unheard of for scientists and engineers to find some inspiration in
science fiction.

I'm reminded of a story about how the science fiction writer Katherine MacLean
[1], who predicted the role of computers in communication and music in her
1947 novelette _Incommunicado_ , accidentally stumbled into a conference of
electrical engineers and found herself quickly surrounded by Bell Telephone
researchers who were inspired by her ideas to build the next generation of
communications equipment.

As a software engineer, I have to admit to being inspired by near-future
software engineering fiction that explores new ideas, many of which are quite
achievable.

[1]
[http://en.wikipedia.org/wiki/Katherine_MacLean](http://en.wikipedia.org/wiki/Katherine_MacLean)

~~~
Niten
> As a software engineer, I have to admit to being inspired by near-future
> software engineering fiction that explores new ideas, many of which are
> quite achievable.

What are some of your favorite examples of this genre?

~~~
simmons
My favorite examples are from several years ago -- Charles Stross's _Halting
State_ and Vernor Vinge's _Rainbows End_. The technology portrayed probably
doesn't seem quite as amazing today in 2013, but I'm always reminded of how
technology seems to be converging on those futures whenever I read over the
latest APIs from the Khronos Group. More recently, Ramez Naam's _Nexus_ from
earlier this year is pretty awesome, although a little more out there than the
other two.

