
A clock that can detect tiny shifts in the flow of time itself - rrauenza
http://www.npr.org/2014/11/03/361069820/new-clock-may-end-time-as-we-know-it
======
gokhan
A comment of the article by Joey N correctly notes that:

 _Right now, on the top of Mount Everest, time is passing just a little bit
faster than it is in Death Valley. That 's because speed at which time passes
depends on the strength of gravity. Einstein himself discovered this
dependence as part of his theory of relativity, and it is a very real effect._

"Just to be clear, the clock in Death Valley appears to run slowly from the
point of view of the eagle-eyed observer standing on top of Everest.

To a person in Death Valley, the clock appears to tick at precisely the rate
it would appear to tick if both person and clock were on top of Everest."

~~~
EGreg
I always wondered what happens to quantum entanglement when time dilation is
involved. For example if one of the particles falls into a black hole, can we
get info out?

~~~
pavel_lishin
As I understand it, you can't actually use this to transmit information. If
you entangle two particles, and then send one away, and attempt to measure the
appropriate property (I think it's spin), hurray: you know that the other
particle's spin is the opposite.

But that's not communication. It's like slicing a coin down the middle without
looking at it, hiding each half in a box, and giving one of the boxes to
someone going to the moon. A week later, you both open your box, and you know
exactly which side of the coin the other person has - but that's not
communication.

(Someone smarter than me, please correct whatever mistakes I've made, and
explain this in a better way.)

~~~
JoeAltmaier
That's the common explanation, but its apparently wrong. There is not a fixed
state of each 'quarter' in each 'box'. They are truly not determined until one
is resolved; then the other is resolved simultaneously. Still, not
communication.

~~~
sjeohp
> There is not a fixed state of each 'quarter' in each 'box'. They are truly
> not determined until one is resolved;

Isn't that unknowable? And aren't both situations (fixed vs undetermined)
effectively the same from an observer's point of view?

~~~
sls
No. What you are calling 'fixed' is a local hidden variable - an internal
state that has yet to be measured but is already determined. This state of
affairs is ruled out by Bell's Theorem -
[https://en.wikipedia.org/wiki/Bell%27s_theorem](https://en.wikipedia.org/wiki/Bell%27s_theorem)

~~~
yohanatan
That's only true if you take the Copenhagen interpretation. There are other
interpretations (like 'consistent histories' for example). See:
[http://en.wikipedia.org/wiki/Copenhagen_interpretation#Alter...](http://en.wikipedia.org/wiki/Copenhagen_interpretation#Alternatives)

~~~
om2
Other interpretations of quantum mechanics do not generally violate Bell's
Theorem, since it appears to be confirmed by experiment. There are other
interpretations which choose to abandon locality rather than hidden variables,
such as the De Broglie-Bohm pilot wave interpretation. But consistent
histories doesn't even do that. It's actually pretty similar to the Copenhagen
interpretation.

~~~
yohanatan
I didn't say anything about violating Bell's theorem. Yes pilot wave theory is
a better alternative that doesn't require spooky action at a distance but
consistent histories doesn't require wavefunction collapse (which is a huge
source of spookiness as well).

------
jessaustin
_" At this level, maintaining absolute time scale on earth is in fact turning
into nightmare," Ye says. This clock they've built doesn't just look chaotic.
It is turning our sense of time into chaos._

This seems a bit sensationalist. The new clocks will be more accurate than any
we have now, for existing applications. Those who develop new applications
_that actually use the increased precision_ will just need to be more careful
about which frames of reference they use. Those who built GPS already solved
some version of these problems.

~~~
sp332
If you can't synchronize the clock with any other clock in the world,
timekeeping gets a bit meaningless.

~~~
GauntletWizard
But you can predict and account for relativity; We already have good protocols
for dealing with expected drift. NTP already takes into account that your PC
is not keeping time as accurately as the upstream servers, and keeps a
driftfile that guesses at the time differential needed. The NTP daemon
silently adjusts the time every second to deal with this.

If two clocks are at different heights, they can compute the differential in
their rates and agree on a time unit. Sure, it might be 1 quadrillion ticks in
on one clock and 1 quadrillion and 1 ticks on the other, but it's still a
'second' so long as both sides see it as simultaneous.

~~~
SiVal
Even if you could measure altitude to centimeter precision, the clock speed
would depend on gravity, not altitude, and the Earth is too lumpy (in terms of
density) for that centimeter to tell you much when comparing two different
locations. I also think (speculate) that with this degree of sensitivity, we
will be able to measure some gravitational fluctuation due to the currents of
molten iron swirling inside the Earth.

With all this uncertainty, all you could do, after getting two clocks to
approximately the same altitude, would be to say that clock A is currently
running a factor of X faster than clock B. What you wouldn't know is how much
of the delta was due to altitude, how much due to unequal density underneath,
and other such factors, compared to how much was due to the internal
differences in the clocks themselves that you were trying to factor out by
using multiple clocks.

~~~
jofer
> we will be able to measure some gravitational fluctuation due to the
> currents of molten iron swirling inside the Earth.

As a geologist, I really wish that were possible, but what you're describing
is just far too small of an effect to be detectable from the surface.
Gravitational acceleration follows an inverse square law. Any signal from flow
in the outer core is completely swamped by the far larger (at the surface)
changes from things like local hydrological conditions, ongoing human
activity, etc.

On the bright side, though, we can already measure changes in the acceleration
of gravity incredibly precisely without directly using relativistic effects.
Even from orbit, things like regional flooding and changes in the mass of ice
sheets can be detected purely from changes in acceleration of gravity. Have a
look at some of the work that came out of the GRACE mission (also see the
ESA's GOCE satellite):
[http://www.jpl.nasa.gov/news/news.php?release=2004-224](http://www.jpl.nasa.gov/news/news.php?release=2004-224)

~~~
HCIdivision17
That is crazy. Like, I always knew that was technically possible, but we
quickly shot the thought experiment down as silly in high school/college. I
mean, feeling the changes in gravity to monitor the surface of a planet?
That's patently absurd.

I'm having a lot of fun being wrong today!

EDIT: Aaaand that's from 2004. Which means I really wasn't paying attention
while in college. Considering my roommate went to JPL to work on a sister
project, I feel a bit of shame just learning about it now.

------
nullc
Crappy article.

Sure, the more precise your oscillator is the more you need to worry about
other effects. Basic cesium beam clocks are precise enough the altitude based
corrections for relativity are required to achieve full accuracy. Each km of
altitude is about 10ns/day of slew, ... I can measure this myself with
equipment I have at home (I have an unusual home).

So sure, when you start making optical clocks with accuracy in the 1e-18 land
then external effects may well be much harder to correct for, e.g. tides have
an effect at the 1e-17 level ... but such a device could still keep time
better than prior techniques. The "They just may not be able to tell us the
time" is rubbish hyperbole that just serves to confuse readers who don't
already know the subject well.

~~~
healsjnr1
This is the worst kind of comment and what is wrong with Hacker News.

No one cares about your intellectual superiority, or the fact this might be a
special interest for you. This article wasn't written for you, you already
know and understand its content. There is literally nothing you could have got
from it.

I on the other hand enjoyed the article. This isn't a field I'm familiar, so
in general my knowledge was increased. That some concepts are misrepresented
and dumbed down is obvious, but this is far out weighed by the general
knowledge that was imparted.

Writing is all about picking an audience and conveying it effectively to the
audience. It's fine to point out inaccuracy or build on the finer points, but
don't be aggressive about it and don't insult the article because it offended
your superior intellect.

~~~
nullc
I'm glad you enjoyed it, but in my opinion the article was misleading. Not
just simplified.

I didn't go on and on in detail about systemic and random effects, linking to
NIST tech reports on all the corrections they have to do on primary standards
([http://tf.boulder.nist.gov/general/pdf/1846.pdf?origin=publi...](http://tf.boulder.nist.gov/general/pdf/1846.pdf?origin=publication_detail)
on the redshift error at NISTs boulder facilities; and
[http://tf.boulder.nist.gov/general/pdf/2704.pdf](http://tf.boulder.nist.gov/general/pdf/2704.pdf)
on the sources of error in the F2 primary reference, see section 3.2 on
relativistic effects), or pointing out people's amateur time keeping
experiments where they demonstrate relativistic influence on decades old
hardware ( [http://leapsecond.com/ptti2006/tvb-project-great-ptti-
ppt.pd...](http://leapsecond.com/ptti2006/tvb-project-great-ptti-ppt.pdf)
(this presentation is long and a ton of fun)), etc. or all the other bits of
trash I could have pulled out to demonstrate knowing something here... because
that wasn't my goal, the only point I was trying to make is that the article
was likely to make many readers _less_ knowledgeable about the subject.

(But I will give those links now, because this argument is boring and time is
neat!)

Perhaps you have enough background that you were not thrown off by the seeming
claim that improved accuracy somehow makes these experimental references _less
useful_, and you already know that relativistic effects aren't unique to
optical lattice clocks and already must be compensated for, but I am sure that
this is not universally the case.

What I get from the article isn't nothing... Potentially I get community
around me which is less informed than they started and all that entails.
Perhaps that's compensated for the fun they had reading about an interesting
subject? or the additional learning they do after? I don't know, but I think
the article could have been just as enjoyable without the bogus mystique that
makes it misleading.

But if pointing out an article was, in my opinion, potentially misleading
makes me everything that is wrong about Hacker News, I'll wear that proudly.

I, for one, think it's more likely the case that crappy shock headlines like
"end time as we know it", constructed drama, and false freshness are a bigger
drag on HN (and wider society) than any of my posts are likely to be... but to
each his own.

~~~
wglb
You didn't really respond to his _No one cares about your intellectual
superiority, or the fact this might be a special interest for you_ part of his
comment.

Your tone and delivery is a bit offputting.

And the thing that I didn't see you comment on that I found particularly
fascinating was that the increased resolution of these clocks is such that you
can discern differences in relativistic effect between floor and wall. That
changes how I think of time.

(My favorite headline that I read sometime around 1965 is "Dating Events in
the Vicinity of a Leap Second.)

~~~
nullc
OK. Dunno what to say there. I thought the article was misleading because it
was intentionally sensationalized, not due to some lack of intellectual
capability or because it wasn't addressed at an audience with a background in
the subject. I'm sure that I know less about the subject than everyone
interviewed in in the article. If anything, I think knowledge makes it better,
since you're not likely to be mislead by it.

Wrt relativistic effect, the first NIST paper I cited shows that they needed
altitude uncertainty less than 1m to avoid redshift from dominating the
clock's error. The second shows that for the improved F2 reference redshift is
one of the largest sources of uncertainty (and the corrected part is orders of
magnitude larger than the other listed systemic errors). It's really cool, I
agree. I'm happy to have people share in enjoying that, but sad about whatever
causes the press to always have to present things as new and categorically
different than what came before.

There are a number of really cool things they didn't mention: For example,
these optical lattice clocks that they're talking about are solid state--
involving mostly only lasers and vacuum cells. Unlike cesium based atomic
clocks, they may have reasonable prospects of being mass produced
inexpensively in the future, and efforts to do this are being funded by DARPA
(useful for many military applications, like jamming systems and anti-jamming,
navigation, and various sensing applications). So unlike the state of the art
atomic references these things may someday show up in very inexpensive
equipment, and allow for some fun science experiments, improvements to
reliable distributed systems, long baseline amateur radio astronomy, etc.

Or, Tom Van Baak measuring gravitational redshift with a minivan and some old
HP cesium beam clocks. okay, not "floor to wall", but if you haven't read his
presentation on it, you should, it's a load of fun and IMO, more accessible in
that it's not talking about technology that exists in a rats nest of cables on
an optical table in a single lab, but just old junk you can find surplus. :)

------
amosgewirtz
A "world in which your watch starts to tick faster, because you're working on
the floor above me." and "your 3:30 happens earlier than mine, and we miss our
appointment," seems ridiculous but it's not a totally foreign idea. For
example, if your apartment is above the 150th floor of Burj Khalifa (the
tallest building on earth), you must wait an additional 3 minutes to break the
fast during the month of Ramadan, while if you live between the 80th floor and
the 150th floor you only need to wait an additional 2 minutes. This mismatch
in time happens for a different reason, but the result is the same and people
seem to manage alright. Saying that this new clock might "End Time As We Know
It" is pretty sensationalist.

~~~
EGreg
Actually software developers have long been aware that different clocks can
run at different speeds and tryto compare apples to apples.

Does anyone remember the name of that article that describes various clock
synchronization techniques? I think it went something like "more than you ever
wanted to know about computer time" and was based on an earlier similar title
about another subject.

~~~
furyofantares
Perhaps "what every programmer should know about time" and "what every
programmer should know about memory" ?

~~~
EGreg
Yep! THANK YOU

------
Animats
Both special and general relativity effects are well known to affect clocks.
This is a major headache for GPS satellites, which have atomic clocks that
gain about 38 microseconds a day vs earth-based clocks from the combination of
speed and gravity difference.

38us/day slip is huge. That's 6 miles of GPS positional error. So GPS was
designed with an correction and adjustment scheme to deal with this. So it's
been a practical problem for decades.

~~~
ithkuil
As far as I know there is no headache, and although the theory is non
intuitive, it just works as expected. The physics behind it can get
complicated at the fundamental level, but computing a time dilation for an
orbit is hardly rocket science. You don't even have to compute it, you can
actually measure it right?

Do you know about any specific painful effect that was revealed only after
general relativity was tried to be applied to GPS satellites in particular?

------
kazinator
Time as "we" know it can only be coming to an end if by "we" mean those who
are completely ignorant of early 20th century discoveries in physics, and who
haven't even been exposed to enough science _fiction_ (let alone nonfiction)
to know about phenomena like the twin paradox. But for time as they know it to
be coming to an end, there has to be some expectation that they will suddenly
be enlightened. The existence of this new clock will certainly not the
catalyst of that enlightenment.

We have already had clocks for decades whose perturbation by relativistic
effects _matters_. Every GPS receiver (commonly found in now inexpensive
technology in use by millions of consumers) makes relativistic corrections to
the time base received from satellite signals, without which the positioning
would be hopelessly inaccurate.

Why would this clock "end time as we know it", when millions of users of GPS
navigation still have a naive view of time.

~~~
mikeash
A nitpick that doesn't detract from your main point: the relativistic
corrections for GPS are applied on the satellites with a slight change in how
fast their clocks run, so that they appear to run at the correct rate when
seen from the ground. The receivers don't have to know about it.

------
pbz
I thought the reason time flows differently on top of Mount Everest is because
the top of the mountain travels faster through space-time than the base
(because of the rotation of the earth), not because of gravity...

~~~
DennisP
It's gravity. The mountaintop doesn't travel faster through space-time.
There's no such thing as absolute speed, there's only the velocity compared to
something else.

Special relativity covers time dilation due to relative velocity, general
relativity covers time dilation due to gravity.

~~~
haberman
Even in relative terms, the top of Mt. Everest is traveling faster than
objects at sea level, no?

Wikipedia says: "Time dilation is caused by differences in either gravity or
relative velocity. Both factors are at play in the case of ISS astronauts (and
are actually opposing one another)."

Why wouldn't the same apply to the top of Mt Everest. Sure, unlike the ISS,
Everest is actually attached to the Earth, but still it is traveling a longer
distance than the oceans over the same period, and therefore would be moving
faster in relative terms AFAICS.

~~~
tedunangst
Is the top of Mt. Everest traveling faster? The distance between here and
there is a constant, no? From my frame of reference it's not moving at all.

~~~
haberman
Mt. Everest is higher. Because of the Earth's rotation, every point on earth
traces 360 degrees every day. However the radius of these arcs depends on
elevation. Ergo the top of Mt. Everest travels farther every day due to
rotation that any other place on earth. That is the same as saying it is
moving faster.

EDIT: I guess compared to a rotating reference frame this isn't true? Clearly
this isn't my area of expertise.

~~~
tedunangst
I think a way to rephrase the question is to ask, is the light coming from the
top of mt. everest red shifted or blue shifted or neither? (I'm not certain of
the answer, either. Physics was a long time ago.)

~~~
Smudge
It depends on the location of the observer. (coming towards you = blue, moving
away from you = red)

------
taylorbuley
The bit about why humanity collectively seeks to measure time so accurately --
perhaps, because, in fact we don't really understand it at all -- is an
interesting and salient morsel for us technologists to chew on. What do we do
when we don't understand something? Measure it!

------
VLM
If you enjoy the article, you'd enjoy these guys:

[http://www.leapsecond.com/time-nuts.htm](http://www.leapsecond.com/time-
nuts.htm)

I hang out more with the volt nuts. (how bout that LTZ1000A voltage ref, eh?
got three in my basement, because two aren't very useful LOL). I do not
remember who begat who but there is probably commentary in the archives of
both, if you go back far enough.

------
Retr0spectrum
'But this new clock is so sensitive, little changes in height throw it way
off. Lift it just a couple of centimeters, Ye says, "and you will start to see
that difference." '

How do they do these differences? Surely they would need a second, equally
accurate clock to compare it with?

~~~
sp332
If it's repeatable, you can just raise and lower the clock a few times and see
the difference. If the clock didn't keep good time, you'd just get a bunch of
noise. But if it's good enough, you should see similar drift each time.

~~~
ars
You can't measure time absolutely. You can only compare time.

You would have to have 2 of these clocks, and compare them.

But probably all they did is just calculate the expected difference.

------
haberman
"My own personal opinion is that time is a human construct"

What is this supposed to mean?

We can measure time with non-human instruments and time is at the core of
physics. How can it be a human construct?

Sure, hours, minutes, days, etc. are human constructs based on movements of
the earth, but time itself?

~~~
kbart
Time only defines the state of the extremely complex system known as universe.
It's an idea to make things more simple for us humans, not a physics
phenomena. Stop all the particles and waves in the universe and time has no
meaning. At least that's how I understand what he meant by this.

------
DanielBMarkham
Seems to me they haven't built a clock: they've built a tricorder.

Put an array of these in a box. Then computationally map the changes in
gravity from each clock. Bingo presto, you've just created a 3-D model of the
mass in the local area.

~~~
ISL
I build precision gravity sensors for a living. We tried doing something
similar and demonstrated a proof of principle. It works, but gravity is often
unkind to the experimentalist, chiefly through the combined facts that many
mass configurations can yield the same signal and that the inverse-square law
requires close proximity for good resolution. Almost any other sensor system
you could dream up is more efficient. For three-dimensional arbitrary mass
distributions, the inverse problem is extremely hard. For 2-D imaging or
simply localizing a mass, things are easier.

If there's any application for pure gravitational sensing that can resolve the
position of a higher-density mass to a few centimeters over distances of
perhaps a meter or that can make simple statements about a meter-scale mass
distribution, please drop me an email. We've tabled the project because we
don't know of a single use for it, academic or commercial. Device cost would
be in the low hundreds of thousands of dollars and require careful operation.
We've thought hard about this, but haven't ever found an application for which
some other sensor wouldn't be far more appropriate. X-rays, neutrons,
resistivity, clever weighing, optical techniques, microwaves, touch probes,
three-year-olds, lemurs, optical imaging, you name it, it's probably cheaper,
better, and faster.

~~~
jofer
If you can improve on current gravimeters, it should be marketable. Potential
fields surveys are still a big business with a lot of customers. (As an
exploration geologist in the oil industry, I use gravimetry on a daily basis.)

Generally speaking, though, accuracy of the sensor is rarely the limiting
factor in gravity surveys.

For land-surveys, it's precisely knowing your elevation, correcting for the
"unwanted" mass distribution around you, etc. For mobile surveys, it's
correcting for the acceleration of whatever vessel the instrument is on. Any
ideas you might have for improving the state of the art for the mobile case
would probably be _very_ marketable.

On a separate note, though, the inverse problem, while fundementally very non-
unique, is still solvable for many practical problems (e.g. we know the range
of density of the materials involved and we can make a reasonable starting
guess for the distribution of mass). Regardless, you're usually interested in
distinguishing between a few scenarios that can be easily forward-modeled.

~~~
ISL
Our instruments (
[http://www.npl.washington.edu/eotwash/](http://www.npl.washington.edu/eotwash/)
) are really good at measuring near-field gravity gradients; we don't build
gravimeters at all. We are adapting our gradiometers to make them more field-
usable (which might have considerable use in prospecting), but that's not a
huge science priority at present. Every few years, we look hard at whether or
not we can make a superior mobile gradiometer. If we could, you'd probably
know :). We have one new design that might fit into a borehole; if it works
well-enough, we may chase commercialization.

A lot of the imaging market appears to come from security/defense
applications, either in portal-monitoring or for IED detection. There are
defense contractors working on both. The former is easily spoofed (put your
uranium pit in a styrofoam sphere in a truck full of grain, done), and the
latter is hard to do at speed in a rugged environment.

I've spent a lot of time trying to figure out how to do gravitational imaging
on the sub-meter scale, and while it does work, it's hard to get sufficient
image resolution to be useful for anything other than a party trick.

If our other science weren't more interesting, I'd be doing it for fun alone.
Burning 3-6 months on the project to assess feasibility was as far as I wanted
to go without a clear exit strategy.

------
wuliwong
If one part of this clock is accurate to 10^-16 but noise/error contributed by
some other aspect of it is larger than that, then it is misleading to claim
these clocks have an accuracy of 10^-16.

This is the same type of stuff they are dealing with in the gravitational wave
experiments like LIGO and VIRGO. They have amazing sensitivity but it is still
lost in the noise. They don't claim to be able to make measurements to
accuracy which is lower than the noise levels. And I don't see why these clock
people should either.

~~~
aqme28
I may be wrong but this sounds like a confusion of accuracy vs. precision
([http://en.wikipedia.org/wiki/Accuracy_and_precision](http://en.wikipedia.org/wiki/Accuracy_and_precision))

edit: By which I mean that this clock could be precise to 10^-16 but be off by
10^-14 due to a mis-calibration.

------
polemic
All that this means is it's high time we abandoned our datetime's in favour of
spacetime's.

    
    
      from spacetime import spacetime, spacetimedelta
      then_and_there = spacetime.here_and_now() + spacetimedelta(years=1, x=5, y=3, z=-2)
    

Now all we need a detailed time-dependant gravity model of the universe to
account for relativistic effects, and some what to throw in quantum scale
stuff and we've solved.... everything.

(edit: formatting is hard)

------
whattime
Hey I've been pondering this article for a little while now and my friends and
I have come up with a question.

Say we have two people, Bob and Jane. Bob and Jane blink at similar rates when
they are standing next to one another. Both Bob and Jane have the accurate
watches described in this article.

Bob then takes a trip to space traveling near the speed of light. Right when
he takes off a laser initiates both stopwatches (one on bob's wrist and one on
jane's). At some time (...), from an equidistant point to both Bob and Jane a
light originates and then stops both Bob's and Jane's wrist watches. Btw, both
Bob and Jane have been blinking the whole time their watches have been
running.

The questions:

Upon stopping the watches:

1\. Do Bob and Jane see a different amount of time passed on their
stopwatches? (most of us are not in contention about this one)

2\. Have Bob and Jane blinked the same number of times?

------
iandanforth
I'm a little sad this article doesn't make the connection to acceleration. The
idea that sitting at different points of a gravity well is exactly equivalent
to different points along an acceleration curve (from the perspective of time)
is a delightful one and I wish it had been mentioned.

------
imaginenore
> _It 's one of the most accurate clocks on the planet: an atomic clock that
> uses oscillations in the element cesium to count out 0.0000000000000001
> second at a time_

For comparison, Planck time = 5.39106×10^-44 sec

We're pretty far from measuring time precisely.

------
jhallenworld
Atomic clocks are cool.. if one wanted to transmit a sporting event in the era
before time base correctors, one had to bring a video sync generator timed by
an atomic clock from the TV station to the event. This gets you the same frame
rate as the TV station (phase still needs to be adjusted to account for speed
of light delay). With all the signals in sync you can switch to a commercial
without messing up everyone's TV.

Time base correctors are also cool: the first generation ones were rack sized
and used core-memory. I think they were an enabling technology for on-location
news.

You can buy your own: rubidium standards sell for less than $300 on ebay.

------
adventured
I don't understand what's so confusing about time.

"but what time really is, is a question that I can't answer for you."

O'Brian almost correctly answers that right off the bat:

"My own personal opinion is that time is a human construct"

Time is a measurement, nothing more. It's not magic, it's not difficult to
understand, it's not separate from reality.

It'd be like calculating how long it takes you to walk around your coffee
table, and then being confused by what it means or what that measurement
consists of.

------
callesgg
[http://en.m.wikipedia.org/wiki/International_Atomic_Time](http://en.m.wikipedia.org/wiki/International_Atomic_Time)
The time we use it based on an average of many clocks.

The fact that time passes at different rates at different locations is already
account for.

------
danbruc
Could we (easily) build a clock that accurately measures space time intervals?
If you place two of them next to each other and synchronize them, you should
be able to separate them and they should still be synchronized whenever you
bring them back together no matter what happened in between.

------
haberman
It amazes me that our master clocks can be so accurate and yet our devices,
which ostensibly get their time from the master clocks through networks, can
be so off.

My Android phone is very frequently 30 seconds or more off from my friends'
iOS phones. I don't even...

~~~
brianpan
Well, it's off by 30 seconds _now_. But eventually....

------
stevewilhelm
> This new clock can keep perfect time for 5 billion years.

In theory.

In practice, I'll bet it stops keeping time before I do.

Check out the Long Now's 10,000 year clock project.
[http://longnow.org/clock/](http://longnow.org/clock/)

------
snarfy
> Time itself is flowing more quickly on the wall than on the floor

Velocity is a function of distance and time. How can time have a velocity?
Couldn't you also say the distances in the clock stretched or shrunk by the
lorentz factor?

------
FlailFast
Armchair astrophysicist here: any way that these clocks could be used to
detect evidence of gravitational waves? Seems like it would be a good use case
for increasingly sensitive clocks.

~~~
joezydeco
FTA: _" A network of clocks in space might be used to detect gravitational
waves from black holes and exploding stars."_

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FlailFast
Thanks! Clearly missed that when I skimmed.

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dendory
I'm glad to hear an actual scientist in this field also think what I've
thought for a long time, which is that time is a human invention. I can't
really explain it, but I've always felt like the universe doesn't really have
a concept of time, that everything is just right now, hence why I don't
believe in time travel either. Time is just a way for us to say 'something
was' or 'will be', but in reality what was isn't anymore, it's not that it's
in the past, but that the object was changed into what it now is.

~~~
fastaguy88
This may make sense to a physical scientist, but biological phenomena do have
a concept of time, because many biological molecules have an evolutionary
history. It's not only that something was, but also that something is that
embodies the trace of what was.

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ck2
_A network of clocks in space might be used to detect gravitational waves from
black holes and exploding stars._

We need to fund this!

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pit
> "But it can tick for billions of years without loosing a second."

Is it loosing or losing? Are both correct?

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egamble
It's losing. For some reason, I see the "loosing" misspelling more often now
than a few years ago. It seems to be a sort of orthographical meme that's
spreading.

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205guy
My brain always stumbles on the loose-lose pair. I don't usually substitute
them for each other, but I always have to think about which one to write. I
believe it is because of the odd spelling and pronunciation of the pair. The
extra o does not change the vowel sound, instead it changes the sound made by
the s (and neither sound like "close"). Typically, the hard and soft s sound
depends on the one or two s's [1]: desert and dessert.

Or it could just be the auto-correct (now in desktop apps as well, not just
mobile).

[1] I hate 's for plurals, but how else would you write "esses".

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darkhorn
Degauss a quarts watch and time will seed up!

~~~
darkhorn
Edit: I mean clock! Not real time.

