
Faster-Than-Light Neutrino Puzzle Claimed Solved by Special Relativity - dhimes
http://www.technologyreview.com/blog/arxiv/27260/
======
thegrossman
This is an almost trivial application of special relativity. It was be
absolutely shocking if the dozens of scientists involves in the neutrino
experiment didn't take this into account.

~~~
gruen
In 1999, NASA lost a $300MM Mars probe due to a metric/imperial conversion
oversight. Shocking, yes; unheard of, no.

~~~
Eliezer
But then they found the error afterward. These physicists _were_ looking for
an error, hard.

------
DanielBMarkham
Okay. This should be an easy one but somehow I'm getting stumped.

I understand the difference in frames between the GPS satellites and the
ground, but the sats themselves are fixed to each other, right? And the ground
stations are also fixed to each other. Each pair is in a separate frame.

But the measurement was on the ground, and the ground stations are not
accelerating relative to each other, not from the satellites. So is this
saying that the ground stations set their clocks initially wrong because of
their relative movement to the satellites? If so, wouldn't this be proven out
by comparing the neutrinos time to the time of a photon?

~~~
InclinedPlane
I haven't read the article yet. However, the ground stations are deeper in the
Earth's gravity well than the satellites. That is equivalent to acceleration
in relativity.

~~~
lutorm
That's negligible.

~~~
hebejebelus
When it comes to 60 nanoseconds, I'm not sure anything is negligible.

~~~
VladRussian
The GR effects here is on the scale of 1e-15s, i.e. several orders of
magnitude less than observed 6e-8s. 7 orders of magnitude is "negligible" as
GP correctly stated.

~~~
mrb
Actually gravitational time dilation on Earth's surface is on the order of
1e-9. But still negligible.

~~~
VladRussian
>Actually gravitational time dilation on Earth's surface is on the order of
1e-9. But still negligible.

it is compare to zero gravitation far from Earth. The effect i'm talking about
is integral of gravitational dilation change along the path of neutrinos. This
path is a chord under Earth surface - the 350 km down to 10km depth and the
next 350km bringing back to surface. The dilation change is about 1e-16 per
meter of depth.

------
kiwidrew
But the GPS satellites and receivers already correct for these relativistic
effects. Specifically:

"The engineers who designed the GPS system included these relativistic effects
when they designed and deployed the system. ... Further, each GPS receiver has
built into it a microcomputer that (among other things) performs the necessary
relativistic calculations when determining the user's location." [1]

[1] [http://www.astronomy.ohio-
state.edu/~pogge/Ast162/Unit5/gps....](http://www.astronomy.ohio-
state.edu/~pogge/Ast162/Unit5/gps.html)

~~~
thegrossman
Relativistic effects are only taken into account when determining the position
of the satellite itself, and the rate of it's clock.

It can't compensate for the effect in the linked-to article (namely, the fact
that the distance and flight time between the neutrino source and destination
is shorter according to the satellite, versus an observer on the ground)
because that effect depends on the specifics of the experiment.

Consider this: If you flipped the location of the neutrino source and
destination, you'd actually get the reverse effect (neutrinos would appear to
be going slower than light).

So it's up to observers on the ground to compensate for relativistic effects
of this nature.

(As I mentioned in another comment, I would be shocked if they didn't already
do that)

~~~
pbhjpbhj
As I understand it, and I've only read the original OPERA experiment paper,
they use the GPS signal to sync some caesium clocks (I'm assuming they're
caesium based on their name CS-something) and that they've done a comparison
by physically moving the clocks to check the synchronisation. The paper is
pretty involved on the points of the GPS sync though so I could have misread
that.

I was impressed that they allow for continental drift in their analysis and
indeed that they were apparently able to detect the crusts movement by an
Earthquake with the apparatus.

> _Consider this: If you flipped the location of the neutrino source and
> destination, you'd actually get the reverse effect (neutrinos would appear
> to be going slower than light)._ //

Flipped WRT what? They've run the experiment at differing times of the day
when the experiment is effectively flipped WRT the _helios_.

They also present a tentative energy relationship with the apparent
superluminal speed which wouldn't, it seems, be accounted for by a simple
relativistic [time-shift] systematic uncertainty.

~~~
cube13
>Flipped WRT what? They've run the experiment at differing times of the day
when the experiment is effectively flipped WRT the helios.

It's "flipped" only with respect to the center of the earth. Since this isn't
a point of measurement(the satellites are the ones effectively holding the
stopwatch), it's not really worth taking into account.

If the neutrino stream was going west->east(i.e. with the satellites) rather
than east->west, the receiving station would appear to be moving away from the
starting point of the neutrino stream. That would effectively decrease the
speed of neutrinos.

------
martincmartin
If true, this just goes to show how many effects you need to take into account
when dealing with numbers that are 2 thousands of a percent. Effects that can
normally be ignored because they're in the noise, turn out to be in the signal
instead.

------
jasondavies
Link to arXiv paper: <http://arxiv.org/abs/1110.2685>

~~~
qntm
I've never seen "photon" spelled with an F before.

~~~
themgt
I think English isn't the author's first language:

 _The authors of the OPERA paper [5] seem to include a correction for the
Lorentz transformations, but they not correct for the change in scenario. And
because they project back the time of provided by the moving clock to the
baseline they seem to incorrectly assume that the outcome of their experiment
should be equivalent to that using a clock in the baseline reference system_

~~~
eldina
Still a little odd, as the Dutch are generally considered to be the best non-
native speakers of English in Europe.

~~~
mauro_oto
Foton is spanish for Photon, I guess it's the same way in Dutch. (It is)

~~~
mladenkovacevic
I'd imagine Photon is spelt Foton in pretty much any phonetic language in the
world (or as they would say fonetic lol)

~~~
kachnuv_ocasek
You mean _fonetik_?

~~~
mladenkovacevic
Haha yes, pardon me.

------
daimyoyo
Until the faster than light result can be recreated in an independent
experiment, I am treating this like cold fusion. Neat result and absolutely
deserving of further investigation, but not definitive.

~~~
Jach
I don't really get why you're being downvoted to oblivion, that's a great
stance to take on science in general. So much media buzz is made over n=1
things; you can cut out a lot from your information diet by ignoring things
until they get replication. If special relativity is wrong, we'll find out in
due course, and the current counter-evidence against special relativity is
hardly a dent compared to the massive evidence in favor (both theoretical and
experimental). Just a few days ago I discovered this paper:
<http://arxiv.org/abs/1005.4172> They assert Events as the only fundamental
object, not space, not time. Then: "by asserting that some events have the
potential to be influenced by other events, but that this potential is not
reciprocal, we can describe the set of all events as a partially ordered set
or poset, which is typically known as a causal set" and from there they derive
Special Relativity.

~~~
jholman
Actually, while I fundamentally agree with the "ignoring things until they get
replication" proposal, I think there's an impracticality there, due to the way
information dissemination works.

There will be no flurry of HN links about this when someone replicates it
(even assuming, for the sake of argument, that neutrinos really can be fired
FTL, all of current physics is wrong, etc etc). Maybe a single link. It just
won't have the network effect; too much of the collective audience's interest
has already been consumed. And there'll definitely be no HN links when the
third and fourth teams replicate it.

Even if that's a wrong claim for this hypothetical result about relativity,
consider yesterday's "forced exercise and Parkinson's" link (
<http://news.ycombinator.com/item?id=3106799> ). That result is _completely_
immature (the rat experiments tested something very different from the human
experiments, there has only been one human experiment, the causal story is all
conjecture, etc), and there's no _way_ we're gonna hear about it when it's
usefully mature (i.e. after ten more studies). (Epistemologically, I think the
current result is not far removed from alternative medicine - there's some
evidence, but no elegant pattern of evidence across multiple contexts, and no
rigorous-but-failed attempts at falsification.) It's an interesting subject,
and an interesting research programme, and I want to know about things like
this, but it's too early to take this into account when making lifestyle
tradeoffs.

So it seems to me that my choices are kind of ugly: I can read a LOT of
cutting-edge stuff, and read all the follow-ups, knowing that most of the
ground-shakers won't actually pan out. Or I can wait 20 or 50 or more years
until it starts showing up in undergraduate textbooks. Or... I don't know,
there must be other options, but I don't know what they are. Another option is
reading Malcolm Gladwell et al, which I think is generally viewed with a
certain exasperation by the genuinely knowledgeable?

Is there a blog or magazine or whatever, that popularizes science, with this
slightly delayed view? "Exciting science news from 10 years ago, complete with
a decade of 20/20 hindsight!"

~~~
0x12
You're on to something here. One of my favorite subjects is 'what happened to
'x'' where 'x' is some discovery or bit of news some time down the line. Most
people don't even remember 'x' when asked about it until you jog their memory
a bit, I can't seem to help remembering all those things.

So, how did that story with the solar panels made from hair pan out? It was
pretty solidly debunked here on HN (as it rightly should have been), but what
interests me is what happened to the major players in that episode, if they're
still making solar panels from hair or if they came to terms with their error
and documented that and published it to negate some of the damage done.

------
zb
This paper: <http://tycho.usno.navy.mil/ptti/1996/Vol%2028_16.pdf> states that
"the time rate is appropriate to observers on the surface of the rotating
earth, that is, in the ECEF". I'm interpreting that to mean that the issue
raised in the OP is not correct, but I am by no means an expert in relativity.

Interestingly, the paper also states ('Missing Relativity Terms?', pp.
195-197) that there has been confusion in the past caused by people thinking
the time is measured in the ECI frame. It shows that the uncorrected-for
relativistic effects have an error on the order of only 2-3mm for a stationary
observer on the earth's surface (the same is _not_ true for e.g. other
satellites). 'In short, there are no "missing relativity terms."'

------
alain94040
Wouldn't an obvious test involve sending something else than neutrinos through
the same path, and measure that they are slower?

~~~
sp332
The path goes through the earth, so they can't send things on the same path.
The detector is far underground to protect it from interference.

------
ck2
Why don't they have synchronized atomic clocks on the ground?

~~~
perlgeek
They do, and they used a mobile atomic clock to compare the times. The problem
is that both locations are in different, accelerated frames of reference, so
reasoning about time in those frames of reference can become non-trivial.

~~~
quijote
Apparently they didn't use a mobile atomic clock but a mobile gps clock to
compare the times:
<http://operaweb.lngs.infn.it/Opera/publicnotes/note134.pdf> So it appears
they synchronized both timing sources with an orbiting clock, and the critique
from this dutch guy seemingly stands.

------
macaroni
could someone please explain this, i wish i could say i get it, but i am so
confused. i don't understand, are they not using gps just to synchronize the
clocks on both ends? what does it matter if in orbit the distance seems
shorter or longer if observed (viewed) from the satellites (is this what they
are saying?)?

~~~
podperson
Let's suppose you're trying to time a 100 yard dash based on sound. Someone
fires a gun, the race starts, and when the first runner crosses the finish
line another gun is fired, you determine the elapsed time.

There are obvious things to correct for -- e.g. if you're standing at the
finish line the sound from the finish line will take 1/3 of a second (roughly)
to get to you, so you need to adjust your calculation.

Now suppose that you are standing off on a barge during the race. You know the
distance to the start and finish lines but ignored the drift of the barge
because you figured it was insignificant.

We're talking 60 nanoseconds. The satellites are moving at tens of thousands
of miles an hour.

~~~
podperson
"the sound from the _start_ line" :-)

------
martinkallstrom
And Einstein snickers high up in the heavens, his hair as white and woolly as
the cloud upon which he partakes his afternoon slumbers.

~~~
martinkallstrom
"Fools", he mutters under his breath, "Neutrinos flying faster than light... I
pity your indolence." With wiry fingers he taps his pipe on his knuckles,
flinging burnt tobacco beyond the edges of the cloud. "Ah well," he sighs,
connecting his iPhone to his Macbook Air, "time to install iOS 5. I bet those
servers are not running as red hot any longer".

------
crizCraig
What's the general consensus on whether or not this was actually debunked?
<http://www.wepolls.com/p/3873491>

