Atomic clocks now keep time well enough to improve models of Earth
Summary: Experimental atomic clocks have now achieved three new performance records, now ticking precisely enough to not only improve timekeeping and navigation, but also detect faint signals from gravity, the early universe and perhaps even dark matter.
What I find very interesting is that this universe has a physically process that can actually be stable to 1 part in 10^18. Why should such a physical fact, actually exist?
Despite the the usual nonsense waffle attached to the existence of "geometrical" "space-time", time is a a physical process. It is real. It is a result of real physical objects changing their position. Thus, their needs to be an object changing its position, very regular to actually create a real physical time reference.
1 sec in the age of the universe is around 0.5 10^18, so, if atoms were not stable to this level, its certain that we could not exist to observe itMy take is, that this is just one of the, possibly, 10^500 (string theory) random multiverse universes, all with different laws of physics.
-- Kevin Aylward
If a region of space could be at absolute zero, within that region of space would there be time? Granted an external observer would continue to experience/measure time but within that region how would you measure time? The same question applies to absolute hot.
The universe would continue to expand within the region so I guess if you could measure the expansion of space its self you would have movement. The expansion is causing one point in space to move relative to another point.
-- Chisolm Republic of Texas
Kevin Aylward wrote
My experience of time is a bit different. In my experience, we live in a cross field of past and future we call 'now'. And our senses are normally limited to just that now. In reality both past and future is known, or can be known. No I am not religious, just talk about my own experience. But religions also point to this.
Today I designed an build an other fascinating experiment that I expect to give a null result in my margin of accuracy but would change things forever if it does not. With some luck and time I will run it this weekend. It is related to time deletion...
Physics is fun, more fun than fishicks, concepts.. hammered into kids heads.
No, multiverses does not do it for me, and even the term 'universe' is misleading, you probably mean 'observed universe' Some have pointed out there are other bangs before the big one everybody is on about, for example Sir Roger Penrose, type his name in youtube and many interesting lectures and interviews pop up, I have viewed many of those. Some of his 'there were other big bang' ideas seem to have been confirmed by observations he predicted.
And why not? Just like we have many stars exploding on an even finer level than nuclear physics why not? Singularities make no sense, divide by zero is math with incomplete equations equations that are incomplete, do not see a reality we have not discovered yet. Just like or 'trickety simulations are incomplete. Now I am looking forward to my new experiment....
If it works I will give it to the Russians, there is some Russian experiment inspiration in it... :-) If you say: >What I find very interesting is that this universe has a physically process >that can actually be stable to 1 part in 10^18.
then remember, all is relative, you are like a piece of rubber band measuring a / on a piece of rubber band and move with it, and say: 'Why does it always measure the same?' Your yard stick moves / stretches / crimps with the thing you test!!!
What experience would that be, and why would it matter?
Time is something that is measured, by a clock usually. How one perceives time is metaphysics, and not something I really care to address.
Ahmmm...... Quantum Mechanics says otherwise.
Religions say, essentially, nothing of relevance to how/why the universe works.
The multiverse is the notion that this big bang is one of many. This is actually trivially obvious after the fact. Just as the Earth is not in the centre of the universe, surprize, surprize.
If their is physics that generate a big bang, why er.. on earth... would that physics only generate the one?
The notion is that there are uncountable numbers of big bangs, all with different laws of physics. Most could not even interact with this one. They could have elctgibs and nuetronphips or whatever, which mean nothing to electrons in this universe if they happened to meet them.
Divide by zero is exactly what is required. It allows an infinite of solutions to the same equation.
Either there is a reason for it all or there is not. If there is a reason, what is the reason for that reason?
The only reason that does not require another reason (i.e. who created god), is if that reason is random.
No reason means its random. Given enough lottery tickets, everyone wins sooner or later.
For me, its the only rational explanation. I don't believe in magic.
-- Kevin Aylward
How do you know what "space" is? What defines it?
This is actually, pretty trivial to understand, why the majors don't, is a mystery to me.
Simply consider a true, empty universe, and reject magic. So....
There is no such thing as "Space" and "Time" on their todd. Everything is about *relations* between real, physical objects. End of.
Space is recognition that objects don't all sit on top of each other. Time is recognition that objects change their position.
That's truly it. This is the real universe. It operates only by real physical objects. Everything is defined with reference to what real physical objects are and do. "Space-time" is simply a mathematical behavioural model for descriptive purposes. It doesn't say anything about the underlying physical mechanisms as to what is.
No objects to define space, no space. Period. Space is marks between objects. No change of objects position, no time. Period. Time is objects moving.
Just imagine everything, all objects, all of them, stopped. Time would stop, because....that's how time is created. without moving objects, time is meaningless.
Special Relativity discovered that the clock of time motion depends on C, the speed of light. It doesn't know why.
I have mussed one or two meanderings on this :-)
-- Kevin Aylward
What makes the objects "real, physical"? Is it space, the space between them? Is it possible that each defines the other?
Clifford Heath.
Yeah amazing! I thought they did 10^15 but I'm obviously way out of date.
So this mostly says there are 10^4 (100x100) atoms in an optical lattice with transitions good* to 10^16, so you get a 100 times averaging advantage. (but there's tons more to make it work... I've only read about optical combs.)
George H.
*I assume good means a long lifetime.
Oops forget the link,
It is a carefully chosen transition with an astonishingly high Q factor and the atoms are trapped in a lattice more or less forced to remain stationary in optical tweezers. Its a very ingenious setup. Might even be able to independently detect larger gravitational waves.
It is effectively a way of trapping the atoms in a vapour phase but ultra cold state so that their emission frequency is almost untainted by Doppler shift. I presume they pick the transitions extremely carefully to find the ones with the most enormous natural Q factor and no nearby transitions that might get in the way.
Back in the day we used H-masers short term during observations on VLBI nodes and rubidium/cesium clocks for the longer term. For reasons that escape me now the more precise short term time on the H-maser tended to occassionally skip a beat from time to time making life more difficult looking for fringes. I think they have overcome this problem now.
This is a modern report on VLBI timekeeping from Haystack:
This is an article from the 1990's by the Royal Belgium Observatory detailing their experiences with H-maser clocks on US navy.mil who seem to have let their site security certificate lapse (hardly a good omen).
Military intelligence = oxymoron.
-- Regards, Martin Brown
Ahmmmm......
A "physical" object, is something that has to be accepted as an axiom.
"space" is what keeps physical objects separate from each other. Its where objects are not.
A collection of objects, separated from each other, marks out a grid, which which to locate other physical objects. Its all relational.
It is physical objects that define and create space. "Space" is completely meaningless without objects. "Time" is is completely meaningless without objects changing position.
Again, this is really so blinding obvious. Its stunning that so much metaphysical waffle abounds about space and time. How we, as conscious beings experience "time" is another entirely.
What is key though, is that the objects that create space, and time when they move, require a stunningly stable definer of space and time. If not, atoms and so forth would dismantle themselves over the billions of years it took for as to evolve, in which case, we could not be here to observe it all. In my view, this leads directly to Special Relativity and Quantum mechanics.
-- Kevin Aylward
Am 01.12.18 um 10:29 schrieb Martin Brown:
This dual H/Cesium thing is still done; the Cesium is the law, but the H has the better short time performance. I have made the analog parts of a Dual Mixer Time Difference system to compare / regulate such a pair. I'm not aware of skipping beats. We store our few atoms in micro gravity on the ISS; that allows for even less motion than at the culmination point of a fountain.
cheers, Gerhard
An axiom, is something that *does not have to* be accepted. They are not intrinsically necessary. But if you do, other consequences may flow. Those consequences are completely contingent, because they depend on a deliberate choice to accept something that was not intrinsically necessary; but we might accept them because the consequences match observation.
However, you can start with different axioms, and get different (or the same) consequences. If those consequences also match observations, there is *nothing* to choose between the axioms.
I happen to like your metaphysics, but it is a *choice* you made.
Clifford Heath.
Sure, but that is not actually what I meant. My statement was about what must be assumed to give any meaning to any discussion at all.
A "physical" object, itself must be taken as fact as a fundamental starting point. If we don't, we might as well all just stay in the bedroom amusing ourselves with our left hand.
A physical object is whatever it needs to be. Its circular, but there is no other choice when one gets to any of the fundamentals. Absolute definitions are impossible.
For example, what is a 1kg mass? It has to be compared to another mass. Which makes it a circular definition. In fact, this is part of the route of the problem in understanding Quantum Mechanics. For example, an object is never in actuallly two positions, but the modelling number that is assigned to it is not unique. Objects can not be defined to have say, position, without defining its position in relation to other objects. Essentially, like, what is the velocity of the moon? Depends on the velocity of the person measuring it. Several unique numbers, for the same physical condition. It don't mean that they are two moons!
Or...In a discussion of consciousness, it must be taken as an axiom that consciousness exists. If you disagree, stand with your legs apart, whilst I give you a firm kicking in the balls to convince you....
and... sure... differing axioms can lead to different models which the same results. Special Relativity & Lorentz Ether Theory is an example. Another example is the "curved-space-time" model of Gravitation under General Relativity, i.e. an assumption of no real physical force of gravity as in mass curves space and space tells mass how to move. However, one gets, essentially, identical equations to that model by an exchange of momentum particle force field from spin 2 gravitons. Most popular accounts of General Relativity usually ignore that fact that the ball rolling around curved space is not actually fact, but only a non unique model of gravity.
All of physics is based on behavioural models of "objects", of which deeper meanings, are essentially, meaningless. An electron is something that has mass, momentum, position, energy, charge, spin etc. There are numbers invented by Physicists, not nature. Nature has no such numbers.
-- Kevin Aylward
No, the basis of physics is observations, not models; the models are superstructures atop those observations, and can be demolished or amended... but the observations cannot.
Physicists measure and express those measurements in numeric form. Nature is all the articles being measured, and certainly DOES have a lot of (pure ratio) numbers, as well as physical quantities which are not unitless (and which can be almost ANY number, if you decide to pick an oddball set of units to express the measurement in).
As an exercise, tell us your weight is 6 and 7/8, and in what units of (force or mass) that is true.
Now your just pissing about with words on a one-upmanship play.
A list of a millions of observations don't make much useful physics. That's just a bunch of unconnected facts. The key bits about *Physics* is connecting the observations. The connections are made by behavioural models. What an "electron" actually is, is meaningless. That's the point that was being made. Many don't understand that point. "Physics" means diddly squat without putting numbers to the observations.
I was specifically addressing the common confusion about what physical objects are. It is trivially obvious that one makes "observations" for models to make any sense at all. The models are, dah...., trying to connect the observations.
I already made the point that the models are not unique, by pointing out two examples. So, your point about models "can be demolished", was thus, er.... pointless.
-- Kevin Aylward
That's what Ernst Mach tried to argue, about a century ago. It isn't a productive point of view.
But it make sense to tie the numbers to concepts.
But you can't build models without concepts
As a philosopher of science, Keven Aylward is less than impressive. Popper might be his role model, but Polanyi
has my vote.
-- Bill Sloman, Sydney
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Not really correct I think. There are many, many observations that form sc ientific theory and later are found to be inaccurate or in some cases just wrong. With the advance of technology it is not uncommon to find the lack of rigor in measurements resulted in bad theory. One example is the lack o f time keeping precision that when improved displayed the irregularities of the rotation of the earth.
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oNot sure what your point is.
orce or mass)
Again...
Rick C.
Tesla referral code -
Einstein would disagree. To wit:
Einstein specifically stated:
"The theory of relativity belongs to a class of "principle-theories...As such, it employs an analytic method, which means that the elements of this theory are not based on hypothesis but on empirical discovery."
That is, physical hypothesis (mechanisms) are ignored from the outset, so clearly makes no statement as to what those processes might be. Einstein is directly declaring here explicitly, that he not not going to offer an explanation, for example, a hypothesis as to why "sources could immediately find a common speed". However, there is no suggestion or implication that such a physical process does not exist. Undelaying mechanisms are just ignored.
The reality is, modern physics, simply assigns parameters to objects (mass, charge, spin) and tries to come up with a mathematically description that takes these parameters as is. Any explanation, just puts the unknown one stage further up the backs of the turtles.
Feynman also address this point as to what does an explanation actually mean.
What's your point?
Some of us actually keep to technical points when discussing technical issues.
Kevin Aylward
But Einstein also wrote the photo-electron paper and the Brownian motion paper, which respectively made photons and atoms discrete entities.
Relativity is problematic for modern physics precisely because it's not quantised, and Einstein spent the later part of his career looking for a theory of everything which would do better.
Not necessarily.
There's a limit to what you can explain to an English-language science reporter in a finite time, and a much lower limit on what it's worth explaining.
The concepts are an essential step on the road to building a useful mathematical model. Observations are fine - as far as they go - but you have to have some idea about what you are observing, and what you want to measure.
My joke, when I was doing the experimental part of the my Ph.D. was that I ought to have been writing down the phase of the moon for each of the strings of observations that I recorded.
You probably mean " the models are superstructures atop those observations, and can be demolished or amended... but the observations cannot. "
This wasn't something I wrote - it comes from whit3rd. I'm conscious of the fact that demolishing the model could well imply that observations would become incomplete, because the next model could require that you measured more variables.
But you are discussing philosophical issues, albeit somewhat inexpertly. And your capacity to keep track of who said what isn't great either.
-- Bill Sloman, Sydney
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