Re: [time-nuts] HP E1938 oscillator
Hi, I'd have to agree with Said, FEI got hit with fines for shipping 1000B OCXO's that were diverted to a proscribed country. Most major countries that are allies of the USA should be OK though. It's surprising what is controlled, very high speed 'scopes, low inductance high energy capacitors, quite a lot of fibre optic and laser stuff too. Robert. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: 27 May 2007 01:39 To: time-nuts@febo.com Subject: Re: [time-nuts] HP E1938 oscillator In a message dated 5/26/2007 15:20:44 Pacific Daylight Time, [EMAIL PROTECTED] writes: Richard (Rick) Karlquist wrote: Regarding non-USA requestors: I will need to look into the customs aspect of this. If anyone on the list can give me a tutorial on this it would be helpful. These are gifts if that matters for customs purposes. Also, they have essentially zero market value as discards. Hello Rick, on the customs issue, you may have to check the items against the commerce control list (CCL Export Administration Regulation) especially section 3A002 I believe. Even (or especially!) if they are of $0 value prototypes. High-tech items such as this super-high-tech oscillator cannot be exported into all countries w/o export license. You have to check the list, and then consider each country individually. Usually most western countries do not present an issue except maybe Israel. Fedex for example will ask for a harmonized code from the CCL to be written on the transport paperwork, and will not export it without written declaration by you. The government can be extremely sensitive to this, that's why some companies like MiniCircuits require a declaration of conformance even when buying and shipping their parts in the US! It is for example illegal to just sent schematics to China via email without export license... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Genetix Limited - Queensway, New Milton, Hampshire, BH25 5NN Registered in England No. 2660050 www.genetix.com Any opinions expressed in this email are those of the individual and not necessarily Genetix Ltd (Genetix) or any company associated with it. This email and any files transmitted with it are confidential and solely for the use of the intended recipient. If you are not the intended recipient or the person responsible for delivering to the intended recipient, be advised that you have received this email in error and that any use is strictly prohibited. If you have received this email in error please notify Genetix by telephone on +44 (0)1425 624600. The unauthorised use, disclosure, copying or alteration of this message is strictly forbidden. This mail and any attachments have been scanned for viruses prior to leaving Genetix network. Genetix will not be liable for direct, special, indirect or consequential damages as a result of any virus being passed on, or arising from alteration of the contents of this message by a third party. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
FEI should be FTS ? On Tue, May 29, 2007 9:31, Robert Atkinson said: Hi, I'd have to agree with Said, FEI got hit with fines for shipping 1000B OCXO's that were diverted to a proscribed country. Most major countries that are allies of the USA should be OK though. It's surprising what is controlled, very high speed 'scopes, low inductance high energy capacitors, quite a lot of fibre optic and laser stuff too. Robert. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: 27 May 2007 01:39 To: time-nuts@febo.com Subject: Re: [time-nuts] HP E1938 oscillator In a message dated 5/26/2007 15:20:44 Pacific Daylight Time, [EMAIL PROTECTED] writes: Richard (Rick) Karlquist wrote: Regarding non-USA requestors: I will need to look into the customs aspect of this. If anyone on the list can give me a tutorial on this it would be helpful. These are gifts if that matters for customs purposes. Also, they have essentially zero market value as discards. Hello Rick, on the customs issue, you may have to check the items against the commerce control list (CCL Export Administration Regulation) especially section 3A002 I believe. Even (or especially!) if they are of $0 value prototypes. High-tech items such as this super-high-tech oscillator cannot be exported into all countries w/o export license. You have to check the list, and then consider each country individually. Usually most western countries do not present an issue except maybe Israel. Fedex for example will ask for a harmonized code from the CCL to be written on the transport paperwork, and will not export it without written declaration by you. The government can be extremely sensitive to this, that's why some companies like MiniCircuits require a declaration of conformance even when buying and shipping their parts in the US! It is for example illegal to just sent schematics to China via email without export license... bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Genetix Limited - Queensway, New Milton, Hampshire, BH25 5NN Registered in England No. 2660050 www.genetix.com Any opinions expressed in this email are those of the individual and not necessarily Genetix Ltd (Genetix) or any company associated with it. This email and any files transmitted with it are confidential and solely for the use of the intended recipient. If you are not the intended recipient or the person responsible for delivering to the intended recipient, be advised that you have received this email in error and that any use is strictly prohibited. If you have received this email in error please notify Genetix by telephone on +44 (0)1425 624600. The unauthorised use, disclosure, copying or alteration of this message is strictly forbidden. This mail and any attachments have been scanned for viruses prior to leaving Genetix network. Genetix will not be liable for direct, special, indirect or consequential damages as a result of any virus being passed on, or arising from alteration of the contents of this message by a third party. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
Robert Atkinson wrote: Hi, I'd have to agree with Said, FEI got hit with fines for shipping 1000B OCXO's that were diverted to a proscribed country. Most major countries that are allies of the USA should be OK though. It's surprising what is controlled, very high speed 'scopes, low inductance high energy capacitors, quite a lot of fibre optic and laser stuff too. Robert. Robert That would have been under the old COCOM rules and cooresponding lists of controlled export items. The actual controlled export items in the new lists were revised recently and such crystal oscillators no longer appear to be a controlled item. Makes sense, since the Russia and China and other countries have have made equivalent performance oscillators for years. Similarly rules on exporting some lasers have also been relaxed. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
FEI didn't make the 1000B OCXO :-) Rob -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dr Bruce Griffiths Sent: 29 May 2007 09:35 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP E1938 oscillator Robert Atkinson wrote: Hi, I'd have to agree with Said, FEI got hit with fines for shipping 1000B OCXO's that were diverted to a proscribed country. Most major countries that are allies of the USA should be OK though. It's surprising what is controlled, very high speed 'scopes, low inductance high energy capacitors, quite a lot of fibre optic and laser stuff too. Robert. Robert That would have been under the old COCOM rules and cooresponding lists of controlled export items. The actual controlled export items in the new lists were revised recently and such crystal oscillators no longer appear to be a controlled item. Makes sense, since the Russia and China and other countries have have made equivalent performance oscillators for years. Similarly rules on exporting some lasers have also been relaxed. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
I agree with Bruce on this one. The whole idea of any restriction is to protect technology from getting into the wrong hands. If they already have that technology, then not much point in trying to restrict its export. Rob -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dr Bruce Griffiths Sent: 29 May 2007 09:35 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP E1938 oscillator Robert Atkinson wrote: Hi, I'd have to agree with Said, FEI got hit with fines for shipping 1000B OCXO's that were diverted to a proscribed country. Most major countries that are allies of the USA should be OK though. It's surprising what is controlled, very high speed 'scopes, low inductance high energy capacitors, quite a lot of fibre optic and laser stuff too. Robert. Robert That would have been under the old COCOM rules and cooresponding lists of controlled export items. The actual controlled export items in the new lists were revised recently and such crystal oscillators no longer appear to be a controlled item. Makes sense, since the Russia and China and other countries have have made equivalent performance oscillators for years. Similarly rules on exporting some lasers have also been relaxed. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
In message !!AAAYAOYAZyOzV8ERq+LmT45ypI7CgAAAEBvfOzZD3oJO [EMAIL PROTECTED], Rob Kimberley writes: I agree with Bruce on this one. The whole idea of any restriction is to protect technology from getting into the wrong hands. If they already have that technology, then not much point in trying to restrict its export. We, depends how many they need, right ? There is a big difference between trying to restrict HV caps for nuclear detonators and 12.7mm bullets... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
In message [EMAIL PROTECTED], Dr Bruce Griffiths writes: Robert Atkinson wrote: The actual controlled export items in the new lists were revised recently and such crystal oscillators no longer appear to be a controlled item. But interestingly enough, nobody has bothered remove analogue computers from the list last I looked :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
Poul-Henning Kamp wrote: In message [EMAIL PROTECTED], Dr Bruce Griffiths writes: Robert Atkinson wrote: The actual controlled export items in the new lists were revised recently and such crystal oscillators no longer appear to be a controlled item. But interestingly enough, nobody has bothered remove analogue computers from the list last I looked :-) Poul-Henning Well spotted. To this you can add Machetes (Post Rwanda item??). Horses (by sea for slaughter). The most amusing part is that the list of components proscribed by non nuclear proliferation requirements creates a handy shopping list of all you need to acquire for Uranium enrichment either via centrifuge or gaseous diffusion as well as a set of specifications for these and bomb triggering components. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
On Tue, 29 May 2007 16:31:40 +1200, Dr Bruce Griffiths wrote: Ulrich, Didier Talking about forces, gravitational fields etc makes no physical sense if the observer's reference frame isn't specified. For an observer in/on a satellite orbiting about the Earth with their reference frame fixed with respect to the satellite. There is no gravitational field, whatever methods chosen to measure a gravitational field (within the satellite) will always produce a null result. Not true. Very simple experiments will show occupants of the satellite that they are in a non-inertial reference frame. (Release a few test masses about the cabin and you will observe that they move/accelerate for no apparent reason, unless the satellite is in free fall which you'll know soon enough,) The experimenter must conclude that the satellite is undergoing acceleration due to the influence of an attractive (gravitational) field. Just because NASA calls it 'microgravity' doesn't make it true. It means NASA is wrong. Weightlessness is not the same as zero-g. Pendulum clocks fail to work, given an initial push they will just rotate around the pivot, provided the pivot suitably constrains the motion of the pendulum (ie a shaft running in a set of ball or roller bearings or similar and not a knife edge pivot). If, however the satellite acts as a rigid body and has a large enough diameter then it would be possible for an observer on the satellite to detect a gravitational field gradient. Therefore, you must conclude that somewhere inside the satellite g is not zero. If the satellite is large enough and orbits close enough to the Earth, this gravitational field gradient would tear the satellite apart. For an observer located on the Earth however the motion of the satellite can be accurately described by Newtonian mechanics where the centripetal pull of gravity acts on the satellite causing it to have a centripetal (radial) acceleration as it orbits the Earth. Bruce Regards, Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics) Bill Beam NL7F -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] HP E1938 oscillator
Shouldn't we restrict our conversation to timing stuff on this group? I'm sure there are lots of other restricted items out there to make bombs etc, but we were talking I believe about OCXOs. In the main the technology we are discussing is pretty well known in all quarters. As long as you cover yourself by stating who the end user is, then you are safe. If you are selling via a third party, then make sure that you are happy with the references he provides. If not - don't sell. Rob -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Poul-Henning Kamp Sent: 29 May 2007 10:04 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP E1938 oscillator In message !!AAAYAOYAZyOzV8ERq+LmT45ypI7CgAAAEBvfOzZD3oJO [EMAIL PROTECTED], Rob Kimberley writes: I agree with Bruce on this one. The whole idea of any restriction is to protect technology from getting into the wrong hands. If they already have that technology, then not much point in trying to restrict its export. We, depends how many they need, right ? There is a big difference between trying to restrict HV caps for nuclear detonators and 12.7mm bullets... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Bill Bill Beam wrote: On Tue, 29 May 2007 16:31:40 +1200, Dr Bruce Griffiths wrote: Ulrich, Didier Talking about forces, gravitational fields etc makes no physical sense if the observer's reference frame isn't specified. For an observer in/on a satellite orbiting about the Earth with their reference frame fixed with respect to the satellite. There is no gravitational field, whatever methods chosen to measure a gravitational field (within the satellite) will always produce a null result. Not true. Very simple experiments will show occupants of the satellite that they are in a non-inertial reference frame. (Release a few test masses about the cabin and you will observe that they move/accelerate for no apparent reason, unless the satellite is in free fall which you'll know soon enough,) The experimenter must conclude that the satellite is undergoing acceleration due to the influence of an attractive (gravitational) field. Just because NASA calls it 'microgravity' doesn't make it true. It means NASA is wrong. Weightlessness is not the same as zero-g. Only, if you insist on sticking to Newtonian physics with all its attendant problems. Pendulum clocks fail to work, given an initial push they will just rotate around the pivot, provided the pivot suitably constrains the motion of the pendulum (ie a shaft running in a set of ball or roller bearings or similar and not a knife edge pivot). If, however the satellite acts as a rigid body and has a large enough diameter then it would be possible for an observer on the satellite to detect a gravitational field gradient. Therefore, you must conclude that somewhere inside the satellite g is not zero. A finite gradient doesn't imply that the field itself is nonzero, except of course towards the extremeities of the satellite. Regards, Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics) Bill Beam NL7F Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] GPS Watch
http://www.mainnav.com/ Somewhat chunky offering from China... Rob Kimberley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
On Tue, 29 May 2007 22:27:42 +1200, Dr Bruce Griffiths wrote: Bill Bill Beam wrote: On Tue, 29 May 2007 16:31:40 +1200, Dr Bruce Griffiths wrote: Ulrich, Didier Talking about forces, gravitational fields etc makes no physical sense if the observer's reference frame isn't specified. For an observer in/on a satellite orbiting about the Earth with their reference frame fixed with respect to the satellite. There is no gravitational field, whatever methods chosen to measure a gravitational field (within the satellite) will always produce a null result. Not true. Very simple experiments will show occupants of the satellite that they are in a non-inertial reference frame. (Release a few test masses about the cabin and you will observe that they move/accelerate for no apparent reason, unless the satellite is in free fall which you'll know soon enough,) The experimenter must conclude that the satellite is undergoing acceleration due to the influence of an attractive (gravitational) field. Just because NASA calls it 'microgravity' doesn't make it true. It means NASA is wrong. Weightlessness is not the same as zero-g. Only, if you insist on sticking to Newtonian physics with all its attendant problems. This discussion began as a classical problem. The relativistic effects are many orders of magnitude smaller than Newtonian (v/c=2.6e-5). For example: A test mass released on the Earth side of the satellite cabin will advance in its own orbit a few mm/sec faster than one released on the far side due to purely classical differences in orbits. Easily observable without even using a timepiece. Once your feet leave the ground, not even Newtonian mechanics is intuitive. Who would have thought that 'putting on the brakes' to leave orbit would cause a satellite to speed up Pendulum clocks fail to work, given an initial push they will just rotate around the pivot, provided the pivot suitably constrains the motion of the pendulum (ie a shaft running in a set of ball or roller bearings or similar and not a knife edge pivot). Run the numbers - depends on how hard the push. Consider sheeparding of material in Saturn rings by small moons. If, however the satellite acts as a rigid body and has a large enough diameter then it would be possible for an observer on the satellite to detect a gravitational field gradient. Therefore, you must conclude that somewhere inside the satellite g is not zero. A finite gradient doesn't imply that the field itself is nonzero, except of course towards the extremeities of the satellite. Of course it does. If g=0 everywhere in the neighborhood of a point then the gradient is zero. Else, what is the meaning of gradient? Grad not zero implies field not uniform implies not(field zero everywhere). Regards, Bill Beam (PhD, physics 1966, past tenured Associate Professor of Physics) Bill Beam NL7F Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Bill Beam NL7F -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] GPS Watch
Cassio has offered similar for several years. Their battery life was less than a day (rechargable). This one is only about half as chunky as Cassio. On 5/29/2007 5:45:33 AM, Jason Rabel ([EMAIL PROTECTED]) wrote: Before clicking on that link I was half expecting some goofy contraption that included a hard hat with a cone shaped GPS antenna on top... lol. Seriously though, I wonder what the battery life is like? Jason http://www.mainnav.com/ Somewhat chunky offering from China... Rob Kimberley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Bill Beam NL7F -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] GPS Watch
At least Casio made an attempt to smooth the edges of the case.. :-) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill Beam Sent: 29 May 2007 15:15 To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Watch Cassio has offered similar for several years. Their battery life was less than a day (rechargable). This one is only about half as chunky as Cassio. On 5/29/2007 5:45:33 AM, Jason Rabel ([EMAIL PROTECTED]) wrote: Before clicking on that link I was half expecting some goofy contraption that included a hard hat with a cone shaped GPS antenna on top... lol. Seriously though, I wonder what the battery life is like? Jason http://www.mainnav.com/ Somewhat chunky offering from China... Rob Kimberley ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Bill Beam NL7F -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.467 / Virus Database: 269.8.0/818 - Release Date: 5/25/2007 12:32 PM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Pendulums Atomic Clocks Gravity Murphy's Lesser Known Laws
Having watched the recent discussion on Pendulums Atomic Clocks Gravity, I thought that I would add the following:- 1. Light travels faster than sound. This is why some people appear bright until you listen to them. 2. Change is inevitable, except of course from a vending machine. 3. Those who live by the sword get shot by those who don't. 4. Nothing is foolproof to a sufficiently talented fool. 5. The 50-50-90 rule: Anytime you have a 50-50 chance of getting something right, there's a 90% probability you'll get it wrong. 6. If you lined up all the cars in the world end to end, someone would be stupid enough to try to pass them, five or six at a time, on a hill, in the fog. 7. The things that come to those who wait will usually be the scraggly junk left by those who got there first. 8. The shin bone is a device used for finding furniture in a dark room. 9. A fine is a tax for doing wrong. A tax is a fine for doing well. 10. When you go into court, you are putting yourself into the hands of 12 people who weren't creative enough to get out of jury duty. Rob K ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Didier Juges wrote: Bruce, A lot of the statements that have been made lately on this subject kind of make sense to me in a way taken in isolation, but they do not all agree with each other, and that makes me uncomfortable. Example: I do not understand why the frame of reference would matter when you talk about gravity field. There is a gravity field or not, and the frame of reference should not matter. I understand that the frame of reference matters when you talk about displacement, velocity or acceleration. But the magnitude of a field, or a force, does not depend on the observer as it is static, or maybe a better term would be absolute or self-referenced? The reason that the frame of reference matters is that gravity is indistinguishable from acceleration. (This is an assumption that Einstein made when deriving his general theory of relativity. It seems to work.) An inertial frame of reference is a non-accelerating frame of reference. In an inertial frame of reference, Newton's laws of motion work -- if you use Newton's gravitational relationship, that the gravitational force (weight) that each of two bodies exerts on the other is proportional to both their masses, and inversely proportional to the square of the distance between them. In an accelerating frame of reference (either linear acceleration, or rotational acceleration, or both) additional forces, technically called fictitious forces, must be introduced in order to explain the motions of bodies with Newtonian mechanics. The fictitious forces on a body are also proportional to the body's mass. (A body's mass is just a measure of its inertia: to accelerate at an acceleration a, a force F must be applied, and the mass m is just F/a.) If the frame of reference has linear acceleration (relative to an inertial frame of reference), bodies within that frame of reference will experience a fictitious force that is proportional to their masses and to the acceleration of the frame of reference. Viewed from the frame of reference of a car that is accelerating away from a stop light, the passengers are pressed back in their seats by a force proportional to the acceleration of the car and to their masses. This fictitious force disappears when you view the situation from the an inertial frame of reference. Viewed from that point of view, the seats are pressing forward on the passengers to cause them to accelerate with the car. Viewed from a rotating frame of reference, we have other fictitious forces: centrifugal force and Coriolis force. Both of these are proportional to the mass of the body on which they act -- when viewed from the rotating frame of reference. Both vanish if you view the situation from a non-rotating frame of reference. Sometimes - usually, even - it's simpler to view the problem from an inertial frame of reference. Sometimes, though, it's easier to look at the problem in an accelerating frame of reference. If you do that, you account for the frame of reference's acceleration by introducing fictitious forces. Now, it makes sense that an object immersed in gravity fields from several larger objects may not be able to tell the difference between multiple fields, and a unique, net field (in the sense of Newton's net force), at least as long as the gradient is small enough that it cannot be observed within the dimensions of the object. So if the net field is zero and the gradient small enough to be ignored, the object will behave the same as if there were no field. When you say within the dimensions of the object I assume that you are looking at the problem from the frame of reference of the object. That's natural if you are, for example, in an orbiting satellite, such as the International Space Station. Viewed from an inertial frame of reference, the ISS is following an orbit determined by the vector sum of the gravitational forces (from earth, moon, sun, etc.) that act upon it. Viewed from the frame of reference of the space station, however, these forces add to zero. However, for an observer on earth, a satellite is in the gravity field of earth (let's assume all other gravity fields from the sun and other planets are negligible), which is not zero at the altitude of the satellite, Even an observer on earth is on an accelerating frame of reference. (The earth rotates on its axis.) ... yet for an observer on the satellite, the net field appears to be zero. Where is the counter-field coming from? And why can't we observe it from earth? How can the field be different when observed from different points? For an observer on the satellite (in the satellite's frame of reference), the counter-field is created by the fictitious forces due to the satellite's acceleration. For example, centrifugal force due to the satellite's gravitational acceleration towards the center of mass of the earth. Could it be that the effect of the gravity field (with is
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Finally, something that makes sense! Thanks, James Maynard. The idea that the centripetal force that balances the gravitational force is fictitious was not popular when I was educated, before 1960. But centripetal force goes away if gravity goes away. The orbiting object continues in a straight line because no forces are causing acceleration. When there is gravity, and an object falls around the Earth, the velocity vector is not constant - it rotates 360 degrees for each orbit of the Earth. An additional acceleration is required to make that happen, hence centripetal force. Gravity and centripetal force must balance if the object is to keep falling in an orbit, which does not have to be circular. If the orbit is not circular then the object's velocity magnitude changes to match its altitude. Centripetal force also goes away if radial motion goes away. The space shuttle has rocket engines that can reduce the radial motion so that the altitude falls low enough to start atmospheric braking. Note that great forces are required to change the angle of the velocity vector. A shuttle can not drive around the sky like an aircraft (when it is in space) but it does have some control of altitude. Bill Hawkins -Original Message- From: James Maynard Sent: Tuesday, May 29, 2007 11:26 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Didier Juges wrote: Bruce, A lot of the statements that have been made lately on this subject kind of make sense to me in a way taken in isolation, but they do not all agree with each other, and that makes me uncomfortable. Example: I do not understand why the frame of reference would matter when you talk about gravity field. There is a gravity field or not, and the frame of reference should not matter. I understand that the frame of reference matters when you talk about displacement, velocity or acceleration. But the magnitude of a field, or a force, does not depend on the observer as it is static, or maybe a better term would be absolute or self-referenced? The reason that the frame of reference matters is that gravity is indistinguishable from acceleration. (This is an assumption that Einstein made when deriving his general theory of relativity. It seems to work.) An inertial frame of reference is a non-accelerating frame of reference. In an inertial frame of reference, Newton's laws of motion work -- if you use Newton's gravitational relationship, that the gravitational force (weight) that each of two bodies exerts on the other is proportional to both their masses, and inversely proportional to the square of the distance between them. In an accelerating frame of reference (either linear acceleration, or rotational acceleration, or both) additional forces, technically called fictitious forces, must be introduced in order to explain the motions of bodies with Newtonian mechanics. The fictitious forces on a body are also proportional to the body's mass. (A body's mass is just a measure of its inertia: to accelerate at an acceleration a, a force F must be applied, and the mass m is just F/a.) If the frame of reference has linear acceleration (relative to an inertial frame of reference), bodies within that frame of reference will experience a fictitious force that is proportional to their masses and to the acceleration of the frame of reference. Viewed from the frame of reference of a car that is accelerating away from a stop light, the passengers are pressed back in their seats by a force proportional to the acceleration of the car and to their masses. This fictitious force disappears when you view the situation from the an inertial frame of reference. Viewed from that point of view, the seats are pressing forward on the passengers to cause them to accelerate with the car. Viewed from a rotating frame of reference, we have other fictitious forces: centrifugal force and Coriolis force. Both of these are proportional to the mass of the body on which they act -- when viewed from the rotating frame of reference. Both vanish if you view the situation from a non-rotating frame of reference. Sometimes - usually, even - it's simpler to view the problem from an inertial frame of reference. Sometimes, though, it's easier to look at the problem in an accelerating frame of reference. If you do that, you account for the frame of reference's acceleration by introducing fictitious forces. Now, it makes sense that an object immersed in gravity fields from several larger objects may not be able to tell the difference between multiple fields, and a unique, net field (in the sense of Newton's net force), at least as long as the gradient is small enough that it cannot be observed within the dimensions of the object. So if the net field is zero and the gradient small enough to be ignored, the object will behave the same as if there were no field. When you say within the dimensions of the object I assume
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Aargh! Please change Centripetal force also goes away if radial motion goes away. to Centripetal force also goes away if angular motion goes away. -Original Message- From: Bill Hawkins [mailto:[EMAIL PROTECTED] Sent: Tuesday, May 29, 2007 12:17 PM To: 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] FW: Pendulums Atomic Clocks Gravity Finally, something that makes sense! Thanks, James Maynard. The idea that the centripetal force that balances the gravitational force is fictitious was not popular when I was educated, before 1960. But centripetal force goes away if gravity goes away. The orbiting object continues in a straight line because no forces are causing acceleration. When there is gravity, and an object falls around the Earth, the velocity vector is not constant - it rotates 360 degrees for each orbit of the Earth. An additional acceleration is required to make that happen, hence centripetal force. Gravity and centripetal force must balance if the object is to keep falling in an orbit, which does not have to be circular. If the orbit is not circular then the object's velocity magnitude changes to match its altitude. Centripetal force also goes away if radial motion goes away. The space shuttle has rocket engines that can reduce the radial motion so that the altitude falls low enough to start atmospheric braking. Note that great forces are required to change the angle of the velocity vector. A shuttle can not drive around the sky like an aircraft (when it is in space) but it does have some control of altitude. Bill Hawkins -Original Message- From: James Maynard Sent: Tuesday, May 29, 2007 11:26 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Didier Juges wrote: Bruce, A lot of the statements that have been made lately on this subject kind of make sense to me in a way taken in isolation, but they do not all agree with each other, and that makes me uncomfortable. Example: I do not understand why the frame of reference would matter when you talk about gravity field. There is a gravity field or not, and the frame of reference should not matter. I understand that the frame of reference matters when you talk about displacement, velocity or acceleration. But the magnitude of a field, or a force, does not depend on the observer as it is static, or maybe a better term would be absolute or self-referenced? The reason that the frame of reference matters is that gravity is indistinguishable from acceleration. (This is an assumption that Einstein made when deriving his general theory of relativity. It seems to work.) An inertial frame of reference is a non-accelerating frame of reference. In an inertial frame of reference, Newton's laws of motion work -- if you use Newton's gravitational relationship, that the gravitational force (weight) that each of two bodies exerts on the other is proportional to both their masses, and inversely proportional to the square of the distance between them. In an accelerating frame of reference (either linear acceleration, or rotational acceleration, or both) additional forces, technically called fictitious forces, must be introduced in order to explain the motions of bodies with Newtonian mechanics. The fictitious forces on a body are also proportional to the body's mass. (A body's mass is just a measure of its inertia: to accelerate at an acceleration a, a force F must be applied, and the mass m is just F/a.) If the frame of reference has linear acceleration (relative to an inertial frame of reference), bodies within that frame of reference will experience a fictitious force that is proportional to their masses and to the acceleration of the frame of reference. Viewed from the frame of reference of a car that is accelerating away from a stop light, the passengers are pressed back in their seats by a force proportional to the acceleration of the car and to their masses. This fictitious force disappears when you view the situation from the an inertial frame of reference. Viewed from that point of view, the seats are pressing forward on the passengers to cause them to accelerate with the car. Viewed from a rotating frame of reference, we have other fictitious forces: centrifugal force and Coriolis force. Both of these are proportional to the mass of the body on which they act -- when viewed from the rotating frame of reference. Both vanish if you view the situation from a non-rotating frame of reference. Sometimes - usually, even - it's simpler to view the problem from an inertial frame of reference. Sometimes, though, it's easier to look at the problem in an accelerating frame of reference. If you do that, you account for the frame of reference's acceleration by introducing fictitious forces. Now, it makes sense that an object immersed in gravity fields from several larger objects may not be able to tell the difference between
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Bill, in general I would underwrite every single sentence of your explanation with the exception of The idea that the centripetal force that balances the gravitational force is fictitious was not popular when I was educated, before 1960. because gravitation IS the centripetal force for the satellite's motion. In this case the right word would have beeen indeed centrifugal. Centripetal forces are REAL forces and are the source of the permanent falling. While forces are one of the very first things that pupils are confronted with in learning physics they are by no means trivial and can be tricky to an high extend. If you would like to dive even deeper into this subject consider the following question: If I stand on the floor of my flat, clearly no acceleration is to be noticed on my body although it is clear that earth attracs me with my weight force (being much too high since years). If no acceleration is to be noticed at my body then a second force must be there that balances the gravitational force, and in this case it is really a BALANCE. Since I stand on the floor the floor must be the source of that force. Big question: HOW does it manage to exhibit this force to my body? Regards Ulrich Bangert Regards Ulrich Bangert -Ursprüngliche Nachricht- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von Bill Hawkins Gesendet: Dienstag, 29. Mai 2007 19:23 An: 'Discussion of precise time and frequency measurement' Betreff: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Aargh! Please change Centripetal force also goes away if radial motion goes away. to Centripetal force also goes away if angular motion goes away. -Original Message- From: Bill Hawkins [mailto:[EMAIL PROTECTED] Sent: Tuesday, May 29, 2007 12:17 PM To: 'Discussion of precise time and frequency measurement' Subject: RE: [time-nuts] FW: Pendulums Atomic Clocks Gravity Finally, something that makes sense! Thanks, James Maynard. The idea that the centripetal force that balances the gravitational force is fictitious was not popular when I was educated, before 1960. But centripetal force goes away if gravity goes away. The orbiting object continues in a straight line because no forces are causing acceleration. When there is gravity, and an object falls around the Earth, the velocity vector is not constant - it rotates 360 degrees for each orbit of the Earth. An additional acceleration is required to make that happen, hence centripetal force. Gravity and centripetal force must balance if the object is to keep falling in an orbit, which does not have to be circular. If the orbit is not circular then the object's velocity magnitude changes to match its altitude. Centripetal force also goes away if radial motion goes away. The space shuttle has rocket engines that can reduce the radial motion so that the altitude falls low enough to start atmospheric braking. Note that great forces are required to change the angle of the velocity vector. A shuttle can not drive around the sky like an aircraft (when it is in space) but it does have some control of altitude. Bill Hawkins -Original Message- From: James Maynard Sent: Tuesday, May 29, 2007 11:26 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Didier Juges wrote: Bruce, A lot of the statements that have been made lately on this subject kind of make sense to me in a way taken in isolation, but they do not all agree with each other, and that makes me uncomfortable. Example: I do not understand why the frame of reference would matter when you talk about gravity field. There is a gravity field or not, and the frame of reference should not matter. I understand that the frame of reference matters when you talk about displacement, velocity or acceleration. But the magnitude of a field, or a force, does not depend on the observer as it is static, or maybe a better term would be absolute or self-referenced? The reason that the frame of reference matters is that gravity is indistinguishable from acceleration. (This is an assumption that Einstein made when deriving his general theory of relativity. It seems to work.) An inertial frame of reference is a non-accelerating frame of reference. In an inertial frame of reference, Newton's laws of motion work -- if you use Newton's gravitational relationship, that the gravitational force (weight) that each of two bodies exerts on the other is proportional to both their masses, and inversely proportional to the square of the distance between them. In an accelerating frame of reference (either linear acceleration, or rotational acceleration, or both) additional forces, technically called fictitious forces, must be introduced in order to explain the motions of bodies with Newtonian mechanics. The
Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity
Bill Hawkins wrote: Finally, something that makes sense! Thanks, James Maynard. Thank you. However, in the following paragraphs you should use the term centrifugal rather than centripetal. A centripetal force is directed towards the axis of rotation. A centrifugal force is directed outward, away from the axis of rotation. I have edited your reply, with my changes indicated in [bracketed] text. The idea that the [centrifugal] force that balances the gravitational force is fictitious was not popular when I was educated, before 1960. But centripetal force [that is, the satellite's weight, mg] goes away if gravity [g] goes away. The orbiting object continues in a straight line because no forces are causing acceleration. When there is gravity, and an object falls around the Earth, the velocity vector is not constant - it rotates 360 degrees for each orbit of the Earth. An additional acceleration is required to make that happen, hence centripetal force. [Right. Here, the centripetal force is the gravitational force, the satellite's weight. The fictitious centrifugal force that balances the satellite's weight is only present when you view the problem from the frame of reference of the orbiting satellite.] Gravity and [centrifugal] force must balance if the object is to keep falling in an orbit, which does not have to be circular. If the orbit is not circular then the object's velocity magnitude changes to match its altitude. Centripetal force also goes away if radial motion goes away. I would say, rather, that the centripetal force, mg in this case, causes the satellite's velocity to change its direction. When viewed in the non-inertial frame of reference of the satellite, the corresponding fictitious centrifugal force also goes away, because the satellite is not accelerating in a direction perpendicular to its velocity. The space shuttle has rocket engines that can reduce the radial motion so that the altitude falls low enough to start atmospheric braking. Note that great forces are required to change the angle of the velocity vector. A shuttle can not drive around the sky like an aircraft (when it is in space) but it does have some control of altitude. Bill Hawkins [I should also edit part of my previous post, as indicated in the bracketed text below.] -Original Message- From: James Maynard Sent: Tuesday, May 29, 2007 11:26 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FW: Pendulums Atomic Clocks Gravity Didier Juges wrote: Bruce, A lot of the statements that have been made lately on this subject kind of make sense to me in a way taken in isolation, but they do not all agree with each other, and that makes me uncomfortable. Example: I do not understand why the frame of reference would matter when youtalk about gravity field. There is a gravity field or not, and the frame of reference should not matter. I understand that the frame of reference matters when you talk about displacement, velocity or acceleration. But the magnitude of a field, or a force, does not depend on the observer as it is static, or maybe a better term would be absolute or self-referenced? The reason that the frame of reference matters is that gravity is indistinguishable from acceleration. (This is an assumption that Einstein made when deriving his general theory of relativity. It seems to work.) An inertial frame of reference is a non-accelerating frame of reference. In an inertial frame of reference, Newton's laws of motion work -- if you use Newton's gravitational relationship, that the gravitational force (weight) that each of two bodies exerts on the other is proportional to both their masses, and inversely proportional to the square of the distance between them. In an accelerating frame of reference (either linear acceleration, or rotational acceleration, or both) additional forces, technically called fictitious forces, must be introduced in order to explain the motions of bodies with Newtonian mechanics. The fictitious forces on a body are also proportional to the body's mass. (A body's mass is just a measure of its inertia: to accelerate at an acceleration a, a force F must be applied, and the mass m is just F/a.) If the frame of reference has linear acceleration (relative to an inertial frame of reference), bodies within that frame of reference will experience a fictitious force that is proportional to their masses and to the acceleration of the frame of reference. Viewed from the frame of reference of a car that is accelerating away from a stop light, the passengers are pressed back in their seats by a force proportional to the acceleration of the car and to their masses. This fictitious force disappears when you view the situation from the an inertial frame of reference. Viewed from that point of view, the seats are pressing forward on the
Re: [time-nuts] OT: Not pendulums or atomic clocks or gravity
The angle of incidence is relative to the surface normal, not the surface itself. It's 0 degrees as the club face contacts the ball, not 45. -- john, KE5FX -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Palfreyman, Jim L Sent: Tuesday, May 29, 2007 8:36 PM To: time-nuts@febo.com Subject: [time-nuts] OT: Not pendulums or atomic clocks or gravity Since you have all enjoyed this discussion on rotating non-inertial frames of reference so much, here's another one for you. In golf, a typical pitching wedge has an angle of 45 degrees. Since angle of incidence equals angle of reflection why doesn't the ball bounce off the club, go straight up and hit you in the face? (A good golfer would hit it 100m.) Jim Palfreyman ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
