A clock that can detect tiny shifts in the flow of time itself

http://www.npr.org/2014/11/03/361069820/new-clock-may-end-time-as-we-know-it

by rrauenza • 12 years ago

259 149 12 years ago

FlailFast2• 12 years ago

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• 12 years ago

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

FlailFast2• 12 years ago

Thanks! Clearly missed that when I skimmed.

jessaustin3• 12 years ago

"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.

sp3324• 12 years ago

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

droopybuns• 12 years ago

If we designed houses around planck lengths as the unit of measurement, we'd get nothing done.

It's not that timekeeping gets meaningless- it just means that there is a threshold where the variability of unsynchronized clocks disrupts certain highly precise problems.

GauntletWizard• 12 years ago

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.

ithkuil3• 12 years ago

If you can't synchronize the clock with any other clock in the world, the increased precision of this kind of clock gets a bit meaningless (or at least has only a very local usefulness).

aqme282• 12 years ago

That's only for measuring the time since 0 BC. If you're trying to measure the duration of a very precise experiment to a very precise degree, this kind of clock can be very useful.

Strilanc2• 12 years ago

You can still synchronize them, it's just that "synchronize" takes on a more complicated meaning. Both sides can use their clock, and the known positions of the two clocks over time, to predict the time that the other clock should be reading. The time deltas are no longer the same on both sides, but you can still transform between the two in order to compare them and detect errors occurring.

More pragmatically, we'll probably agree on a standard centralized time (i.e. International Atomic Time) and everyone will translate between their own locally perturbed time and the standardized time when synchronizing.

deciplex• 12 years ago

It's not like the issue they're dealing with doesn't exist with literally every clock in the world - it's just that we didn't have a clock that was sensitive enough to notice before.

In a sense, this is not a property of the clocks, but rather just the way nature is. We can't keep these clocks in sync at various places around the world, because the thing they measure is not in sync at various places around the world. But, we've known that for about one hundred years - what's the big deal?

nullc is right, this is a bad article.

amosgewirtz2• 12 years ago

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.

EGreg4• 12 years ago

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• 12 years ago

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

guelo• 12 years ago

The Ramadan fast ends at sunset. The sunset ends later for people at higher elevation because you can see over the horizon a little bit more. Not because of the time dilation of gravity.

amosgewirtz2• 12 years ago

Right, which is why I said that "This mismatch in time happens for a different reason."

taylorbuley• 12 years ago

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!

gokhan• 12 years ago

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."

EGreg4• 12 years ago

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_lishin3• 12 years ago

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.)

biot• 12 years ago

Quantum entanglement cannot communicate information, regardless of any other factors. See http://en.wikipedia.org/wiki/No-communication_theorem

Strilanc2• 12 years ago

Probably nothing more than usual. The local operations you can do to entangled particles are all commutative w.r.t. the operations applied by the other side. So whether they happened at the same time or before or after or slower or faster than the other side doesn't affect the local outcome

(That should also make it clear why you can't use entanglement to communicate instantaneously: the other side must get the same results whether they measure before or after you've sent your message. So if entanglement allowed communication instead of just esoteric types of coordination, you could use it to send messages backwards in time.)

darkhorn5• 12 years ago

Also may depend on what kind of watch you wear, like quarts watches are sensitive to magnetic field.

VLM3• 12 years ago

Sadly no. That would be a convenient and nifty way to vary frequency for ham radio applications if it were the case. Even just a couple dozen PPM in a magnetic field would be sufficient for transmit receive switching but it just doesn't work. Also if that were the case mounting a crystal nearby a power transformer or fan would generate massive noise in the output signal unless magnetically shielded, which also doesn't happen.

I would imagine magnetizing a mechanical watch would really mess things up, so at a "just under really messed up" threshold it would probably have the claimed effect.

You may be thinking of YIG garnet oscillators which are very dependent on magnetic field but they haven't been common tech in maybe 30 years. Even used on ebay they cost more than modern new microwave VCOs which is annoying. I have a box of old YIG osc in my basement which I actually used for ham radio experiments before modern solid state VCOs took over.

AnimalMuppet3• 12 years ago

Relativistic time effects are changes in the rate of time itself, not changes in the mechanism of a clock. If there was a magnetic field effect, that's a different, additional thing.

ChuckMcM• 12 years ago

But how about a person in the center of the Atlantic listening to a metronome broadcast from Death Valley and one from Mt. Everest, tick-tick-ticktick-ticktick-tick-a-tick-tick-a-tick :-)

joshgel• 12 years ago

He's really bored.

And death valleys ticks slower. He's at sea level, which is higher than Death Valley.

darkhorn5• 12 years ago

Degauss a quarts watch and time will seed up!

darkhorn5• 12 years ago

Edit: I mean clock! Not real time.

pbz• 12 years ago

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...

DennisP2• 12 years ago

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.

haberman5• 12 years ago

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.

waqf• 12 years ago

There is no absolute velocity, but there is absolute acceleration. And the mountaintop is accelerating more because it's in circular motion with a larger radius.

However, the effect of gravity is much more significant (if it weren't, the mountaintop would be flying out into space due to centripetal force).

AnimalMuppet3• 12 years ago

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

It's actually due to acceleration, whether from gravity or from motion. And, given earth's rotation, points on the surface accelerate (except for the poles).

But, as I pointed out elsewhere in this discussion, it's distance from the axis that determines acceleration from rotation, not distance from the center of the earth. (Distance from the center does determine gravity, though).

HCIdivision176• 12 years ago

Probably not. You're looking at a height difference of about 9 km [1], at a radius of 6380 km from earth's core [0] versus about an equatorial 6371 km. Rotational velocity at the equator is about 1040 mph [5], while Everest is looking at about 6380 km / 6371 km * 1040 mph = 1041.5 mph, assuming we moved Everest to the equator and kept everything else the same. One or two mph is really small compared to c, so much so WA just sorta says gamma = 1 [4].

And so is a mere 0.15% increase in height. But compare the gravitational acceleration at these two heights:

[2] Everest = 9.76322 m/s^2

[3] Sea Level = 9.831 m/s^2

Sea level is 0.69% stronger. That's somewhat more significant, and given that gravitational energy follows the inverse-square law, it makes some sense that it would amplify differences more than the linear effects of speed.

[0] https://www.google.com/search?q=radius+of+earth

[1] https://www.google.com/search?q=height+of+everest

[2] http://www.wolframalpha.com/input/?i=gravitational+accelerat...

[3] http://www.wolframalpha.com/input/?i=gravitational+accelerat...

[4] http://www.wolframalpha.com/input/?i=lorentz+factor+at+1.5+m...

[5] http://www.wolframalpha.com/input/?i=rotational+velocity+of+...

EDIT: forgot the reference to rotational velocity (and spelling). Note that the point is scale here. Gravity is n^2 versus velocity's n. It'll have a stronger effect in most cases (and any where speed overcomes, well, we call them relativistic speeds, and they'll often be some appreciable fraction of c, like 1% or more).

DOUBLE EDIT: 'AnimalMuppet makes a good point that the entire estimate for Everest's rotational velocity is flat out wrong. So I've changed my premise to match my initial incredibly incorrect assumption.

If I were to attempt to be correct about the problem, we'd see that Everest is cos(27.9881 degrees [10]) = 0.8837 [11] as fast as the equator, which sorta blasts out any height changes by long shot. (Note I'm assuming the earth to be a perfect, frictionless sphere here, and definitely not a oblate spheroid.)

[10] https://www.google.com/search?q=latitude+of+everest

[11] https://www.google.com/search?q=cos(27.9+degrees)

AnimalMuppet3• 12 years ago

You're forgetting that Everest isn't on the equator. Distance from the center of the earth doesn't matter; distance from the axis of rotation matters. So you need to multiply Everest's (height + radius) by the cosine of its latitude.

DanielBMarkham2• 12 years ago

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.

pavel_lishin3• 12 years ago

http://en.wikipedia.org/wiki/Robert_L._Forward#Forward_Mass_...

trhway• 12 years ago

it would take some time to develop "gravitationally stealth" F-22 :)

jofer3• 12 years ago

For what it's worth, just directly measuring changes in gravitational acceleration is much easier and much more sensitive to changes in mass distribution.

We've been able to measure gravitational acceleration very precisely for over a century now.

An 80-year-old LaCoste & Romberg gravimeter will do the job quite nicely, though it's slow to use and you need to know the elevation you're taking the measurement at very precisely. (Interestingly, the ones made before ~1950 are more precise than the ones made in the 60's to 90's. It's basically a very well made and well calibrated spring. When they switched to mass-producing them, the quality fell.)

Now you have a second problem, though... Regardless of whether you've measured things through gravitation acceleration or time dilation, going from the measured effect back to an actual mass distribution is a non-unique inverse problem. There are an infinite number of equally correct solutions (and a larger infinite number of incorrect ones). You can make a pretty good guess at what the mass distribution by applying reasonable a-priori constraints, but there's no single unique way to get the mass distribution from the gravitational effect of the mass.

ISL3• 12 years ago

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.

jofer3• 12 years ago

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.

DanielBMarkham2• 12 years ago

I'm just a random internet commenter (and don't we know everything!), so take what I say with a grain of salt.

I wonder, however, if the problems you are describing are things that would work themselves out over time as the equipment improves? The precision of these clocks sound like they're many orders of magnitude better than the old gravity sensors. I think. Perhaps all we'er waiting on is some kind of crazy technological magic over the next 50 years that would involve miniaturization, improved accuracy, and an array of a million or so. (All of which I just made up)

haberman5• 12 years ago

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• 12 years ago

Well, it's off by 30 seconds now. But eventually....

haberman5• 12 years ago

"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?

beachwood232• 12 years ago

I think his point is that time is so inherently relative to the location / inertia of the observer that it is in practice a human construct.

physonaught2• 12 years ago

The physicists definition of time is "What clocks measure". It sounds like he was just saying the party line.

kbart• 12 years ago

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.

VLM3• 12 years ago

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

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.

pit2• 12 years ago

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

Is it loosing or losing? Are both correct?

leoc• 12 years ago

Maybe time really is running out. ;)

pit2• 12 years ago

It's not running out, it's unwinding.

egamble• 12 years ago

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.

205guy• 12 years ago

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".

Retr0spectrum• 12 years ago

'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?

sp3324• 12 years ago

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.

delecti• 12 years ago

Right, but drift to/from what.

ars• 12 years ago

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.

Animats• 12 years ago

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.

ithkuil3• 12 years ago

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?

dendory• 12 years ago

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• 12 years ago

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.

jhallenworld• 12 years ago

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.

nullc4• 12 years ago

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.

wuliwong2• 12 years ago

The comment where the man makes a comparison to measuring electric current but tries to make it seem like we understand time better than electric current annoyed me. As if we have a greater fundamental understanding of what an electric charge "is" vs. time.

jacquesm2• 12 years ago

I love this page on that subject:

http://amasci.com/elect/charge1.html

It's not exactly 100% current (pun intended) but it makes the point nicely.

healsjnr1• 12 years ago

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.

nullc4• 12 years ago

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... on the redshift error at NISTs boulder facilities; and 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... (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.

jdbernard• 12 years ago

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

This article is poor scientific journalism. "New clock may end time as we know it." Seriously? How is that remotely true? There is nothing in this article that justifies that headline. If anything, this new clock affirms our understanding of the nature of time, pointing out the minute changes that we expect to see but have not had instruments sensitive enough to measure until now.

But that desire to pin down the elusive ticking of the clock may soon be the undoing of time as we know it: The next generation of clocks will not tell time in a way that most people understand.

Undoing of time as we know it? Will the existence of this clock somehow magically make all other clocks in the world turn incomprehensible? No, the truth is that most of society won't even be aware of this "undoing of time as we know it."

And on the subject of telling time in a way most people don't understand, that is already true of the cesium clocks they mention. We already have to deal with relativistic drift, of which most people are ignorant.

But this new clock has run into a big problem: This thing we call time doesn't tick at the same rate everywhere in the universe. Or even on our planet.

This line makes it out like we didn't know about relativity. Also, I hardly think more precision is a problem. If anything it gives us power to do things we never have done before. Technologies like GPS wouldn't work without the current generation of clocks. I'm excited about the new possibilities that an even more precise clock will open. It's not a problem.

They just may not be able to tell us the time.

What?!! This is incredibly misleading. The new clock will be just as able to tell time as all of the clocks we've had up until this point.

I could go on, but nullc is right, this article is crap. It is dripping with sensationalism.

krick2• 12 years ago

The fact you don't like his comment doesn't make it "worst kind of comment". Nothing was essentially wrong about what he said. Maybe kinda harsh, I don't know and don't really care: it's plain stupid to favor fanciness of speaking to correctness of facts delivered.

In turn, there were wrong, imprecise and misleading statements in that article, which does make it bad to some degree. It's not the worst of it's kind, but still pretty bad. Actually I would consider it harmful, to write something that is easy to pick up for uneducated people, that gives them impression that they understand it while giving them wrong impression about the subject, that is, being misleading. I'm not sure I could appreciate that even if it was impossible to write easy-to-understand useful quasi-scientific articles/books, but as I've seen them I must conclude it's not impossible, so that makes people writing misleading stuff with attractive headlines even more guilty.

Your comment in it's turn contains nothing, but claiming somebodies comment is "worst" based only on that being not populistic enough. I would say it makes your comment "the worst kind of comment and what is wrong with Hacker News".

goblin89• 12 years ago

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.

Comments like this may often offer a fair bit of factually correct information and interesting insights. Opposing views, strong opinions, critical thinking—all this seemed more like a “feature” of HN rather than a “bug” to me.

(Sorry, I may have accidentally downvoted you; this was not intended.)

physonaught2• 12 years ago

I though the article was cute, but I wouldn't go so far as to say it was crappy. The essence of the article was on point. You can't just report the time anymore, once special and general relativity become important, you have to report space-time. Sure, other effects are going to become important as well, but the essence of the article: time is not absolute, and this has practical difficulties for clock-makers, was well communicated.

ObviousScience• 12 years ago

You already can't do that, though. This isn't some new problem experienced only by this clock, though it's more sensitive to it.

The GPS satellites already had to correct for the passage of time being different for them relative to the surface of the planet. Decades ago.

kazinator• 12 years ago

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• 12 years ago

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.

iandanforth• 12 years ago

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.

polemic• 12 years ago

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)

wuliwong2• 12 years ago

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.

aqme282• 12 years ago

I may be wrong but this sounds like a confusion of accuracy vs. 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.

danbruc• 12 years ago

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.

imaginenore• 12 years ago

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.

snarfy• 12 years ago

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?

adventured• 12 years ago

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• 12 years ago

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.

stevewilhelm• 12 years ago

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/

ck2• 12 years ago

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

We need to fund this!

whattime• 12 years ago

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?

A clock that can detect tiny shifts in the flow of time itself

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