"The Armagh Observatory Human Orrey" Mark Bailey Presentation of Armagh Observatory outreach initiatives and the Human Orrey. Presented at 2nd UNAWE International Workshop. (Date: October 2006)

1. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
The Armagh Observatory
Human Orrery
Mark E. Bailey, David J. Asher
and
Apostolos A. Christou
meb@arm.ac.uk
http://star.arm.ac.uk
The Human Orrery
An orrery is a dynamic solar system model
• designed to illustrate the heliocentric world-view
In a Human Orrery people become the planets
• the whole of solar system astronomy can be
investigated in a fun way “on the ground”
The simplest Human Orreries are not to scale
• e.g. planets on circular orbits; no accurate link to
the planets’ true positions in space versus time
! => only a limited range of activities possible
They become more interesting when laid out
with greater care
• e.g. the Dynic Astropark Human Orrery (Japan)
The Human Orrery is as versatile as a sundial
• the Armagh model has an accurate scale of 1:150
billion, and a fixed time-step of 16 days
! it shows the 6 classical planets,1 asteroid and 2
comets at any time Dynic Astropark Human
! it includes the 13 ecliptic constellations, as well as Orrery (c.1997)
directions to more distant objects in the Universe
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Leiden, 2006 Oct. 12
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2. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Why “Orrery”?
Invented around 1704 by George Graham
(c.1674–1751)
• he gave a copy (or its design) to John Rowley
(1674–1728), the celebrated London instrument
maker
Rowley made a copy for Prince Eugène of
Savoy
• he then made another for his patron, Charles
Boyle, the fourth Earl of Orrery
Charles Boyle (1674–1731)
• author, soldier and statesman
• grandson of Roger Boyle (1621–1679), the first
Earl of Orrery
! a son of Richard Boyle, the first (or Great) Earl of
Cork (1566–1643)
! in his day, “one of the richest men on the planet”
The name “orrery” for such a model was
popularized by the Irish essayist Sir Richard Images © Science Museum
Steele (1672–1729) and National Portrait Gallery
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Rowley’s Orrery, in Science Museum
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3. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
John, Fifth Earl of Cork and
Orrery (b.1707)
Orrery, invented by Graham 1700. Improved by
Rowley and presented by him to John, Fifth Earl of
Orrery, after whom it was named at the suggestion
of Richard Steele
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Ground-Based Astronomy for All…
Each orbital tile shows various
astronomical data
• the name; tile number; date;
distance from Sun; ecliptic
longitude; and true anomaly
With a simple “key” shown on
the central Sun-tile
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4. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Principal Features
The Armagh Human Orrery shows:
• the elliptical orbits and changing positions of
various solar system objects versus time
! provides an accurate “map” of the solar system,
giving users a better “feel” for the Earth’s
position in space
! enables all of Kepler’s laws to be discovered by
direct measurement; the times of meteor
showers from the two comets; and much more…
• the relative orbital periods and positions of the
different orbital objects
• the thirteen ecliptic constellations through
which the Sun passes in a year
! which ones are visible at different times of year
! and that the First Point of Aries is in Pisces!
• the directions to more distant objects in the
Universe
! facilitating discussion of the variety of different
“animals” in the astronomical “zoo”
Most important, it is fun to use!
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Location in the Observatory
Grounds
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5. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Overview of Human Orrery
2nd UNAWE Workshop
Leiden, 2006 Oct. 12
Some Orrery Activities
“Walking the Orrery” and “Running the Orrery” (and
how fast can you go…)
• investigating Kepler’s third law
Finding the planets “tonight” (or at any other date)
• and discovering which can be seen after dark at
night, or as morning or evening stars
• investigating conjunctions, oppositions and
alignments; and the visibility of distant stars
Measuring angles and distances between objects
• working out distances and speeds in space
• investigating Kepler’s laws by direct measurement
• investigating the mathematics of orbital motion and
of ellipses (areas, circumferences etc.)
• using a “map” with a scale of 1:150,000,000,000
Learning new mathematical and calendrical concepts
• counting (more than 200 tiles!)
• modular arithmetic (e.g. 14 tiles for Venus etc.)
• ratios of planetary orbital periods (e.g. 8/13 V/E)
• “leap steps”, “leap stops” and Leap Years
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6. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Other Activities and Games
History, design, teamwork, dance and play!
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Leiden, 2006 Oct. 12
Summary and Conclusions
The Armagh Human Orrery (http://star.arm.ac.uk/orrery)
• a dynamic solar system model where people become the
moving objects
• the first outdoor exhibit to show with precision the orbits and
positions of the main solar system bodies
• engages people in maths, space science and astronomy
! introduces key concepts of astronomy, as well as pointers to more
distant objects in the Universe, in a fun and entertaining way
• brings “heaven down to Earth”; provides an improved
understanding of Earth’s changing position in space
! encourages people to observe the sky, and to compare what they
see from “Earth” — on the ground — with what they see from Earth
— in the sky
• facilitates a wide range of interdisciplinary activities
! e.g. ranging from history, astrology and the development of
astronomy, to dance, physical exercise and design
• easy to make, easy to use, and as versatile as a sundial
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7. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Acknowledgements
We thank especially Miruna Popescu and Brendan Owens for their help
with images and other material
Astronomy at Armagh Observatory is funded
by the Northern Ireland Department of
Culture, Arts and Leisure
meb@arm.ac.uk
http://star.arm.ac.uk
Orbital Periods, Leap Steps
and Leap Stops
Planet Orbital Orbital Number Leap Step Number Number of
Period Period of Tiles or Leap of Orbits Earth
(days) (years) per Orbit Stop? for Leap Years for
Step/Stop Step/Stop
Mercury 87.969 0.2408 5.5 STEP 520 125
Venus 224.701 0.6152 14 STOP 23 14
Earth 365.256 1.0000 23 STEP 6 6
Mars 686.980 1.8808 43 STEP 16 30
Ceres* 1681.592 4.6039 21* STOP 50 230
Jupiter** 4332.589 11.862 27** STOP 13 154
Saturn** 10759.23 29.457 67** STOP 4 118
*Tiles every 80 days
**Tiles every 160 days
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8. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Find the Planets
The Human Orrery can show where the planets are at any time.
To do this use the Earth as a key.
Earth in Space
STEP 1: Find the nearest Earth tile for the chosen time of year. For Choose an object and a date (for example, Mars on 2010 August 13). Use
example, Earth is at tile number “14” on August 13 of any year. Keep this the method described above to locate the Earth and the object at this time.
Earth tile number (“14”) in your head. Now stand on the Earth’s tile and look towards the central Sun tile.
If the planet is to the left of the Sun tile, then it will be visible from Earth as
STEP 2: Find the Start Tile for the chosen planet and year using the table.
an “evening star”. If it is to the right, it will be visible as a “morning star”. If it
This gives the planet’s position on January 1 for each year. For example, on
2010 January 1 Jupiter is at tile “114” and Mercury is at tile “4”. lies beyond the Sun tile, or (in the case of Mercury and Venus) possibly
between the Earth and the Sun, then it will be a daytime object and not visible
at night. If the planet is behind you (i.e. opposite the Sun in space), then it
will be visible all night. Planets can be seen when the sky is clear, so you can
check your result on the next clear night.
You may find cases when planets appear to line up in the same direction as
seen from Earth or another vantage point in space. This is a planetary
grouping or alignment. For example, Mercury, Venus and Saturn were closely
aligned at tile numbers “0”, “11” and “11”, as seen from Earth (tile “11”), on
2005 June 26.
Looking farther afield, beyond the solar system, the Human Orrery shows the
thirteen (not twelve) zodiacal constellations traversed by the Sun in the
course of a year, the constellation boundaries, and the directions to a variety
of more distant objects in the Universe. You can use the Human Orrery to
discover when these constellations and other objects can be seen at night.
Positions of orbital objects on January 1 for each year.
STEP 3: Go to the Start Tile and move forward the same number of steps
as the Earth tile number from STEP 1. In the case of Jupiter, stepping
forward 14 tile-steps brings you to tile “128”. Note that the tiles for Jupiter
and Saturn are marked every ten steps so that you must find the next closest
tile (“130”) or make a rough estimate of tile position. For the two comets and
the asteroid, tiles are marked every 5 steps. Positions of the six classical planets for a range of interesting dates.
For Mercury, be careful to follow the order of tiles, which are interleaved.
Also, when tile “0” is reached (for Mercury or any other planet) you must
continue around the orbit again. For Mercury, in this example, you should
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reach tile “7” for 2010 August 13 after moving forward 14 steps.
Leiden, 2006 Oct. 12
The Human Orrery
What is an Orrery? The small yellow dot at the The orbital tiles show
An orrery is a dynamic model of the solar system. The Human Orrery is an orrery in centre of the Sun tile data such as tile
represents the size of the number, date, and
which people play the role of the moving planets. The first orrery, a mechanical device,
was invented around 1704 by the English clockmaker George Graham (c.1674–1751). Sun (about 1.4 million km) the values of L, r, and
on the scale of the Human f.
This showed the Earth and Moon orbiting the Sun, but later models showed all the known
planets. Orrery.
Walking the Orrery
First, choose a planet and find its Start Tile, for example the tile labelled “0”, which is the
planet’s position on 2005 January 1. Now move from tile 0 to 1 to 2 and so on. Each
step corresponds to 16 days of time. Repeat this for other planets to see how their
speed changes with distance from the Sun. If you are part of a group, each person can be
a di!erent planet and you can walk the orrery in lock-step on the call of a group leader.
The name “Orrery” comes from the patronage of Charles Boyle (1674–1731), the fourth
Earl of Orrery, Co. Cork, who commissioned a copy of the first orrery from the London
instrument maker, John Rowley. The Armagh Human Orrery is the first outdoor exhibit
to show with precision the elliptical orbits and changing positions of the planets and
other solar system objects with time.
With this exhibit, you can imagine you are a planet, asteroid or comet, and follow its path
around the Sun. You can investigate the laws of planetary motion, work out the positions
of the planets at any time, their distances from one another and when they are visible
from Earth. The model also shows the directions from Earth of more distant objects in
the Universe.
Note that the asteroid Ceres and the two comets (Encke and Halley) are shown every five
time-steps (80 days), and Jupiter and Saturn every ten time-steps (160 days).
When you come to the last tile of a given orbit, make sure you move on to the next tile,
Sun Tile labelled “0”, and start counting 0 to 1 to 2 again. Also, observe that Mercury’s eleven
tiles represent two revolutions of that planet around the Sun.
At the centre of the Human Orrery lies the Sun tile. This presents a key to the
information on the orbital tiles. The letter r denotes the distance from the Sun in “Walking the Orrery” shows that planets nearer the Sun move faster. You can also see
when planets come close to one another or line up as seen from Earth or another point
astronomical units (AU), where 1 AU is approximately 150 million kilometres. The scale
of the Human Orrery is 1:150 billion, so 1 metre on the ground corresponds to 1 AU in on the orrery. In fact, the Human Orrery provides an accurate “map” of the solar system,
enabling all the laws of planetary motion to be discovered by direct measurement on the
space.
ground.
The true anomaly f is the angle measured around the orbit from the object’s point of
closest approach (perihelion) to the Sun. L denotes the ecliptic longitude of the object,
measured anti-clockwise from the direction of the First Point of Aries, which is shown on
the Sun tile and also on the plaque fixed to the Robinson Dome. As viewed from Armagh
(in the northern hemisphere) all the planets revolve around the Sun anti-clockwise, in the
direction of increasing L. On the Human Orrery only Comet Halley revolves in a
clockwise, “retrograde” direction.
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9. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Observatory Grounds and Astropark
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Education and Public
Outreach
Exhibitions, Tours, Public
Lectures, Open Days
• library, archives and rare books
• public lectures, school and
undergraduate work experience
• developing Observatory Grounds,
Astropark, and Human Orrery
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10. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Some Historic Instruments
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Why Astronomy?!
Underpinned by three main strands of interest:
• the broadly “religious” or cosmological strand
! the quest to understand our “Origins”, Man’s place in the Universe
• the broadly “practical” strand, i.e. commercial, military, or
economic “spin-off” from astronomy, including education
! e.g. the Calendar; Navigation; Celestial Mechanics; Earth
Observation; Image Processing; the “Inspiration” of Astronomy
• the broadly “scientific” strand of curiosity driven research into
Mathematics, Planetary Science and Astrophysics
! the project, no less, to understand the nature, contents and
interactions of all the objects in the entire Universe…
We live at an exceptional time: a “Golden Age” in which
activity in all these areas is at an all-time high
• provides astronomy with a rare conjunction of opportunity
• contributes to the unprecedented advances in observation
and theory (the former almost always leading the latter)
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11. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Location of the Armagh
Observatory
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Montage Overview of Human
Orrery
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12. Mark E. Bailey, David J. Asher, and The Armagh Observatory Human Orrery
Apostolos A. Christou
Overview of Human Orrery
2nd UNAWE Workshop
Leiden, 2006 Oct. 12
RAS, London, 13 January 2006 12