Discussion:
Anybody have suggestions for time related science fair projects?
(too old to reply)
Van Horn, David
2018-05-11 14:41:58 UTC
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Measuring the speed of light (Fizeau or Michelson method? Other ways)


I saw a great demo of this at the Exploratorium in SF. They had a long spool of fiber optic, a disc with holes, and a light source. When static, if the light shines through the hole in the disc into the fiber, then you can see the light coming out the other end of the fiber through a different hole. When rotating, you increase speed and the fiber output gets dimmer and dimmer till it's gone. At that point, the light going into the fiber arrives when the other end is blocked, and vice versa. High tech, but simple.
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jimlux
2018-05-13 13:29:31 UTC
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How about a demonstration of how GPS works, substituting sound waves for
radio ?
Maybe three sound sources with harmonically-related frequencies, then
measure their phase difference on an oscilloscope.
Cheat a bit : you don't need to do cdma acquisition. Have one reference at
a low frequency, switch two more on alternately at a higher frequency.
Measure the phase difference between one pair at a time and calculate your
location relative to the stationary sources.
In science fairs that are judged, the rubric really demands something
that can be cast into the classic "literature search, hypothesis,
experiment, data reduction, conclusion" form. Even straight up
engineering is sometimes knocked down - the International Fair (being
held this week, as it happens) does have separate rubric for engineering
projects.

So what you want to do is cast this as an experiment or engineering
project. For the latter: "Performance characterization of acoustic
multilateration"

For a more "sciencey" approach, you'd postulate some theory/hypothesis:
"air temperature measurement can be used to compensate for speed of
sound variation in acoustic multilateration"


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jimlux
2018-05-12 02:30:07 UTC
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A few months ago, I was a judge for the county level middle school
science
fair.  (I'm not very good at what they wanted, but that's a different
problem.)
What sort of interesting time related experiments can a middle school
geek do?
Borrowing serious gear may not be off scale as long as a youngster
can run it.
The whole area of celestial nav is time related and uses very simple
equipment -
Telling time by measuring the sun in some way.  Occultation of stars
by the moon.  Positions of jupiter's big 4 moons.
Pendulum experiments.  If the student has a way to change their
altitude, can they measure changes in g.  Driving a pendulum.
Coupled resonators  (spring/mass, pendulum, vibrating rods)
Measuring the speed of light (Fizeau or Michelson method? Other ways)
Water clock, sand hour glass, etc.  Measuring performance variation
over environmental variations.
the trick with good science projects is finding something that's not
just a "lab demo" - where there's some engineering component to
figuring out how to execute the demo with unusual or improvised
equipment, or where you're measuring something that's not been done
before.
The advice that we got when doing a middle school science project was
that you wanted an experiment with only one variable (altitude or
temperature etc) and a  measurement of a single variable (maybe over time).
and with multiple measurements possible - most middle school projects
tend to be a "one and done" - you get big kudos if you show even basic
statistical analysis - a simple significance test is a big deal,
assuming you're not doing it with some cookbook calculator. You'd need
to be able to explain what it means to the judges.

And something where you show an appreciation of measurement precision
and any curve fit. I used to mark down projects where they used Excel
to do a regression curve, and then reported the coefficients with 5
digits of precision, on measurements with at most 2 digits. (and no, not
thousands of measurements to get a sqrt(N) improvement)

AVAR is a kind of sophisticated concept - I think it would be hard for a
middle schooler to adequately explain what it is (heck, there's enough
trouble for people who do it for a living).


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Paul Bicknell
2018-05-11 06:56:55 UTC
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Hi how about frequency difference /temperature of a oved'ed Xtal oscillator

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] On Behalf Of Bill
Hawkins
Sent: 11 May 2018 06:40
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Anybody have suggestions for time related
sciencefairprojects?

Well, how about the frequency drift between a pendulum, a tuning fork,
and a crystal.
Atomic standards could be added depending on availability.

Bill Hawkins


-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] On Behalf Of Hal
Murray
Sent: Thursday, May 10, 2018 11:56 PM
To: time-***@febo.com
Cc: Hal Murray
Subject: [time-nuts] Anybody have suggestions for time related science
fairprojects?


A few months ago, I was a judge for the county level middle school
science fair. (I'm not very good at what they wanted, but that's a
different
problem.)

What sort of interesting time related experiments can a middle school
geek do?

Borrowing serious gear may not be off scale as long as a youngster can
run it.

---------

An alternat meaning to the "nut" part of time-nuts: ")
https://www.snopes.com/fact-check/schools-removing-analog-clocks/


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Wayne Holder
2018-05-13 00:37:58 UTC
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Using a pendulum to measure gravity requires precision timekeeping.
Wikipedia has a nice discussion of this at
https://en.wikipedia.org/wiki/Pendulum#Gravity_measurement

There are number of very clever techniques developed long ago, such as
Henry Kater's design for a reversible, dual pivot pendulum that made it
possible to get quite precise measurements starting about the 1820s. Then,
around 1835 Friedrich Bessel found ways to simplify calibration of Kater's
design and even cancel out errors due to air drag. More interestingly,
gravity measuring pendulums became not of the earliest ways used to
standardize the measure of length, which shows how nearly all efforts at
standardization ultimately rely on accurate timekeeping.

Wayne
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Brooke Clarke
2018-05-13 00:55:34 UTC
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Hi:

Here's some great ideas from Clifford Stoll:
https://www.ted.com/talks/clifford_stoll_on_everything?language=en
The transcript is available in 27 languages.

PS He has an on line business selling Klein Bottles (some with calibration certificates:)
http://www.kleinbottle.com/

I got a Chinese Spouting Bowl from him.
http://www.prc68.com/I/ChineseSpoutingBowl.shtml
--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html


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Bob kb8tq
2018-05-11 13:32:59 UTC
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Hi

NTP time offsets through various phases of the distribution process …..

Bob
A few months ago, I was a judge for the county level middle school science
fair. (I'm not very good at what they wanted, but that's a different
problem.)
What sort of interesting time related experiments can a middle school geek do?
Borrowing serious gear may not be off scale as long as a youngster can run it.
---------
An alternat meaning to the "nut" part of time-nuts: ")
https://www.snopes.com/fact-check/schools-removing-analog-clocks/
--
These are my opinions. I hate spam.
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MLewis
2018-05-12 23:25:30 UTC
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Would it be too simple a project to have a GPS demonstration:

* GPS time, leap seconds (need for)
* UTC time
* Local Time Zone time (rise, set, noon)
* Solar Time (rise, set, noon)
* Solid Earth Tides
* and a custom sun dial, marked for solar time and local time (a lamp
can simulate solar noon and other angles)


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Bruce Griffiths
2018-05-12 22:39:06 UTC
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Like this so called star target?:
https://www.edmundoptics.com/test-targets/resolution-test-targets/1-black-1-white-glass-star-target-5deg-wedge-pair-angle/

Bruce
Hi
Post by Van Horn, David
Measuring the speed of light (Fizeau or Michelson method? Other ways)
I saw a great demo of this at the Exploratorium in SF. They had a long spool of fiber optic, a disc with holes, and a light source. When static, if the light shines through the hole in the disc into the fiber, then you can see the light coming out the other end of the fiber through a different hole. When rotating, you increase speed and the fiber output gets dimmer and dimmer till it's gone. At that point, the light going into the fiber arrives when the other end is blocked, and vice versa. High tech, but simple.
My favorite exhibit that we never see anymore. IIRC it was a quarter
mile of fiber and a green laser. And ISTR that the disc had one hole on
one arm and two radially on the other, but I can't remember why. I
thought that the light would pass through the same hole twice, once on
the way in and on the way out when that same hole rotated 180 degrees to
the other end of the fiber. The disk spun somewhere around 50 rps (60
with an AC motor?).
1km in free space would be 6 microseconds round trip. I'm not sure a disk spinning at 3600 rpm would work. you'd need to have the "hole spacing" be on the order of 6 microseconds - and at 100 rps (6000 RPM), 10 ms/rev, you'd need the sending and receiving hole 6/10000 of a rev apart (about 0.2 degrees).
if you had 10 km of fiber, it would be a bit easier.
I think the term “long fiber” in this case should really be “very very long”. Exactly how the typical student
funds the acquisition of something in the “many miles” range, I have no idea.
You could use an optical grating of some sort as your “spinning disk”. The end of the fiber is going to be
mighty small. The spacing on the grating could be quite tight. Where you get a circular part like that ….
again no idea.
Bob
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Van Horn, David
2018-05-14 13:20:09 UTC
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What I remember was a brown or black disc with holes around the perimeter.
I remember a lot of holes.
This was around 1991 or so.

-----Original Message-----
From: time-nuts <time-nuts-***@febo.com> On Behalf Of Bruce Griffiths
Sent: Saturday, May 12, 2018 4:39 PM
To: Discussion of precise time and frequency measurement <time-***@febo.com>
Subject: Re: [time-nuts] Anybody have suggestions for time related science fair projects?

Like this so called star target?:
https://www.edmundoptics.com/test-targets/resolution-test-targets/1-black-1-white-glass-star-target-5deg-wedge-pair-angle/

Bruce
Hi
Post by Van Horn, David
Measuring the speed of light (Fizeau or Michelson method? Other ways)
I saw a great demo of this at the Exploratorium in SF. They had a long spool of fiber optic, a disc with holes, and a light source. When static, if the light shines through the hole in the disc into the fiber, then you can see the light coming out the other end of the fiber through a different hole. When rotating, you increase speed and the fiber output gets dimmer and dimmer till it's gone. At that point, the light going into the fiber arrives when the other end is blocked, and vice versa. High tech, but simple.
My favorite exhibit that we never see anymore. IIRC it was a quarter
mile of fiber and a green laser. And ISTR that the disc had one
hole on one arm and two radially on the other, but I can't remember
why. I thought that the light would pass through the same hole
twice, once on the way in and on the way out when that same hole
rotated 180 degrees to the other end of the fiber. The disk spun
somewhere around 50 rps (60 with an AC motor?).
1km in free space would be 6 microseconds round trip. I'm not sure a disk spinning at 3600 rpm would work. you'd need to have the "hole spacing" be on the order of 6 microseconds - and at 100 rps (6000 RPM), 10 ms/rev, you'd need the sending and receiving hole 6/10000 of a rev apart (about 0.2 degrees).
if you had 10 km of fiber, it would be a bit easier.
I think the term “long fiber” in this case should really be “very very
long”. Exactly how the typical student funds the acquisition of something in the “many miles” range, I have no idea.
You could use an optical grating of some sort as your “spinning disk”.
The end of the fiber is going to be mighty small. The spacing on the grating could be quite tight. Where you get a circular part like that ….
again no idea.
Bob
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ed breya
2018-05-14 20:00:37 UTC
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I don't know what sort of scientific level this contest is geared for,
but would guess that for middle-school level, extreme numbers-oriented
analysis of esoteric, time-nutty things may not dazzle, but bore the
participants, judges, and audience.

It may be best to relate to more hands-on, everyday experience and
observations of "normal" people. I like the suggestions about GPS and
stroboscopic and lasery stuff, where one can maybe appreciate how modern
everyday things work (like GPS, or how it's possible to talk to or send
a picture to anyone in the world on your cell phone, and how these could
not happen without precise time), or something visual and physical.

Some of the props should be "ordinary" things, like the a cell phone or
GPS receiver, for example. Lasers are always good as long as there's a
direct visual component to the observation. Strobe type stuff is
particularly easy, because it's doable with mechanical and acoustical
props, and signal measurement times are in reach of common lab equipment
like generators, scopes, and counters, and of course there's a big
visual experience component.

Small power visible lasers are common nowadays, so easy to use. Strobe
lights are fairly common too, but maybe not so much as the other items.
You can build (or buy) quite a nice strobe light nowadays using
high-powered LEDs - the kind used for replacing incandescent and other
illumination. This is quite easy and much safer than dealing with flash
tubes, and is much more versatile. In fact, maybe this could even be a
science fair project. The time element is in the stroboscopic effects
and ability to slow or freeze apparent motion - almost everyone has
observed this and can relate.

Ed
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Van Horn, David
2018-05-14 20:42:30 UTC
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Ah. The falling water goes up illusion.


-----Original Message-----
From: time-nuts <time-nuts-***@febo.com> On Behalf Of ed breya
Sent: Monday, May 14, 2018 2:01 PM
To: time-***@febo.com
Subject: Re: [time-nuts] Anybody have suggestions for time related science fair projects?

I don't know what sort of scientific level this contest is geared for, but would guess that for middle-school level, extreme numbers-oriented analysis of esoteric, time-nutty things may not dazzle, but bore the participants, judges, and audience.

It may be best to relate to more hands-on, everyday experience and observations of "normal" people. I like the suggestions about GPS and stroboscopic and lasery stuff, where one can maybe appreciate how modern everyday things work (like GPS, or how it's possible to talk to or send a picture to anyone in the world on your cell phone, and how these could not happen without precise time), or something visual and physical.

Some of the props should be "ordinary" things, like the a cell phone or GPS receiver, for example. Lasers are always good as long as there's a direct visual component to the observation. Strobe type stuff is particularly easy, because it's doable with mechanical and acoustical props, and signal measurement times are in reach of common lab equipment like generators, scopes, and counters, and of course there's a big visual experience component.

Small power visible lasers are common nowadays, so easy to use. Strobe lights are fairly common too, but maybe not so much as the other items.
You can build (or buy) quite a nice strobe light nowadays using high-powered LEDs - the kind used for replacing incandescent and other illumination. This is quite easy and much safer than dealing with flash tubes, and is much more versatile. In fact, maybe this could even be a science fair project. The time element is in the stroboscopic effects and ability to slow or freeze apparent motion - almost everyone has observed this and can relate.

Ed
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jimlux
2018-05-14 23:06:08 UTC
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Post by ed breya
I don't know what sort of scientific level this contest is geared for,
but would guess that for middle-school level, extreme numbers-oriented
analysis of esoteric, time-nutty things may not dazzle, but bore the
participants, judges, and audience.
Even at the middle school level, science fairs can be quite competitive
- The California Science Fair draws hundreds of projects at that grade
level (Grade 6-9) selected from fairs at the county level, which in turn
draw from school fairs.

The standard of judging is quite rigorous - a "demo" won't generally be
competitive at the state level, although it could make it through the
county level - depending on the county.
Post by ed breya
It may be best to relate to more hands-on, everyday experience and
observations of "normal" people. I like the suggestions about GPS and
stroboscopic and lasery stuff, where one can maybe appreciate how modern
everyday things work (like GPS, or how it's possible to talk to or send
a picture to anyone in the world on your cell phone, and how these could
not happen without precise time), or something visual and physical.
Virtually all science fairs prohibit lasers in a display - too many "bad
things" happening with remarkably high powered lasers available online.
You'll need to show it cannot be operated, or that it cannot present a
hazard (i.e. if it's built into a piece of hardware that cannot be
modified on site to allow exposure).

Even laser pointers are not allowed (because how is the display review
committee to know whether it's 1 mW or 100 mW)
Post by ed breya
Some of the props should be "ordinary" things, like the a cell phone or
GPS receiver, for example. Lasers are always good as long as there's a
direct visual component to the observation. Strobe type stuff is
particularly easy, because it's doable with mechanical and acoustical
props, and signal measurement times are in reach of common lab equipment
like generators, scopes, and counters, and of course there's a big
visual experience component.
Small power visible lasers are common nowadays, so easy to use. Strobe
lights are fairly common too, but maybe not so much as the other items.
You can build (or buy) quite a nice strobe light nowadays using
high-powered LEDs - the kind used for replacing incandescent and other
illumination. This is quite easy and much safer than dealing with flash
tubes, and is much more versatile. In fact, maybe this could even be a
science fair project. The time element is in the stroboscopic effects
and ability to slow or freeze apparent motion - almost everyone has
observed this and can relate.
A strobe is a fine display, and there's probably interesting time-nuts
kinds of experiments one can do using it - the combination of a short
duration strobe with a modern cellphone camera running at, say, 240 fps,
might be a good way to instrumentally measure a mechanical vibration.

But you need to have some set of experiments designed to confirm or
reject a hypothesis. You could have a hypothesis about synchronization
of vibrating rods on a common base, for instance.



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Mike Feher
2018-05-12 15:15:48 UTC
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How about a Stroboscope? -



Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

848-245-9115



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Bill Hawkins
2018-05-11 05:34:26 UTC
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Um, time dilation by altitude if you have access to a mile high change.
Or subjective time dilation when a person is prevented from doing a task
on time.

Bill Hawkins

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] On Behalf Of Hal
Murray
Sent: Thursday, May 10, 2018 11:56 PM
To: time-***@febo.com
Cc: Hal Murray
Subject: [time-nuts] Anybody have suggestions for time related science
fairprojects?


A few months ago, I was a judge for the county level middle school
science fair. (I'm not very good at what they wanted, but that's a
different
problem.)

What sort of interesting time related experiments can a middle school
geek do?

Borrowing serious gear may not be off scale as long as a youngster can
run it.

---------

An alternat meaning to the "nut" part of time-nuts: ")
https://www.snopes.com/fact-check/schools-removing-analog-clocks/


--
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Bruce Griffiths
2018-05-13 00:36:40 UTC
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At telecom wavelengths GDD can be quite low.
Laser source spectral widths can also be low.
At visible wavelengths an fiber length imbalance of 1m with a 1nm bandwidth light source makes interferometry impossible/difficult without GDD compensation even if delays are matched.
The moodulation bandwidth isnt an issue for this application but with a long enough fiber the source spectral bandwidth may be.
Polarisation locked single transverse mode VCSELs are inexpensive and typically have spectral bandwidths of 100MHz or so.


Bruce
Indeed; however, with single mode fiber the limit is not too bad. At
Arecibo we routinely ran bandwidths in
excess of 1 GHz through fibers of about 1500 ft length with no problems.
For the science fair project a
bandwidth of a few MHz should suffice for lengths of, say, 500 ft. It's
just that I don't know how bad the
multimode dispersion problem would be when using shorter wavelengths, and
I'm sure not equipped to
make any measurements at home now that I'm retired and far away from the
observatory.
Dana
Even with single mode fiber its finite group delay dispersion will likely
restrict the usable light source bandwidth.
Bruce
It may be that a nicely-written request to Corning could yield the loan
of
a big spool of fiber
for the duration of a science fair project.
Another alternative, perhaps easier to implement, might be an
electrically-driven light modulator
at the detector end. For the source, an LED or diode laser is easy to
modulate at respectable
rates. This approach should allow use of such high frequencies that an
open optical path using
mirrors might even suffice.
If one were to use two modulated sources (or one with a beamsplitter),
with
one path delayed
by the long(ish) fiber and the other by a minimal-length local fiber,
something resembling a streak
camera (implemented with a rotating mirror) might permit use of
substantially higher pulse rates
than with a rotating disk, without incurring the need for anything very
fancy in the way of mechanics.
Only the modulated source should require a reasonably accurate drive
frequency- the "detector"
would be essentially self-calibrating. A small mirror, say of cm size,
could probably be safely
rotated at Dremel speeds approaching 500 rev/s, and if 1 mrad angular
resolution is attained,
this would yield a resolution of ~160 ns. So a fiber length of 500 ft
(approx 750 ns one-way delay)
should yield an angular separation of nearly five "dots" between delayed
and undelayed dots.
And if the sources are modulated at a rate such that a few pulse
repetitions are visible in the
field of view, the scheme is self-calibrating as long as the PRF and the
velocity factor in the fiber
are known. Probably the only precision work would be the optics required
to focus a reasonable
amount of light from the source(s) onto the two fibers., and I believe
this
requirement could be
adequately met with microscope objectives borrowed from one's school's
biology lab.
A fly in the ointment is that if ordinary (read, inexpensive) IR fiber is
used at convenient visible
wavelengths, propagation will occur in more than one spatial mode, with
different modes propagating
at different speeds. I don't know how much of a problem this would
raise. But it may be that if
tweaking of the transmitting end illumination is done, both in angle and
transverse position, most
of the propagating light could be confined to a single mode. I speak of
visible wavelengths simply
because using these avoids the cost of electronic detectors,
oscilloscopes,
etc, potentially saving
a lot on the cost of the experiment as well as making for a more
satisfying
presentation.
Dana
Post by Van Horn, David
Hi
Post by Van Horn, David
Measuring the speed of light (Fizeau or Michelson method? Other
ways)
Post by Van Horn, David
Post by Van Horn, David
I saw a great demo of this at the Exploratorium in SF. They had a
long spool of fiber optic, a disc with holes, and a light source. When
static, if the light shines through the hole in the disc into the
fiber,
Post by Van Horn, David
then you can see the light coming out the other end of the fiber
through a
Post by Van Horn, David
different hole. When rotating, you increase speed and the fiber
output
Post by Van Horn, David
gets dimmer and dimmer till it's gone. At that point, the light going
into the fiber arrives when the other end is blocked, and vice versa.
High
Post by Van Horn, David
tech, but simple.
My favorite exhibit that we never see anymore. IIRC it was a
quarter
Post by Van Horn, David
mile of fiber and a green laser. And ISTR that the disc had one
hole on
Post by Van Horn, David
one arm and two radially on the other, but I can't remember why. I
thought that the light would pass through the same hole twice, once
on
Post by Van Horn, David
the way in and on the way out when that same hole rotated 180
degrees to
Post by Van Horn, David
the other end of the fiber. The disk spun somewhere around 50 rps
(60
Post by Van Horn, David
with an AC motor?).
1km in free space would be 6 microseconds round trip. I'm not sure a
disk spinning at 3600 rpm would work. you'd need to have the "hole
spacing" be on the order of 6 microseconds - and at 100 rps (6000
RPM), 10
Post by Van Horn, David
ms/rev, you'd need the sending and receiving hole 6/10000 of a rev
apart
Post by Van Horn, David
(about 0.2 degrees).
if you had 10 km of fiber, it would be a bit easier.
I think the term “long fiber” in this case should really be “very very
long”. Exactly how the typical student
funds the acquisition of something in the “many miles” range, I have no
idea.
You could use an optical grating of some sort as your “spinning disk”.
The
Post by Van Horn, David
end of the fiber is going to be
mighty small. The spacing on the grating could be quite tight. Where
you
Post by Van Horn, David
get a circular part like that ….
again no idea.
Bob
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Dana Whitlow
2018-05-11 15:22:44 UTC
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Raw Message
How about measuring variations in propagation delay for WWV on various
frequencies, or WWVB,
using GPS ticks as a reference.

Dana K8YUM


On Fri, May 11, 2018 at 9:41 AM, Van Horn, David <
Post by Van Horn, David
Measuring the speed of light (Fizeau or Michelson method? Other ways)
I saw a great demo of this at the Exploratorium in SF. They had a long
spool of fiber optic, a disc with holes, and a light source. When static,
if the light shines through the hole in the disc into the fiber, then you
can see the light coming out the other end of the fiber through a different
hole. When rotating, you increase speed and the fiber output gets dimmer
and dimmer till it's gone. At that point, the light going into the fiber
arrives when the other end is blocked, and vice versa. High tech, but
simple.
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