Orrery

Description

Models of the Solar System have been made since the times of Ancient Greece and Rome and by the early 18th century clockmakers used Gears to make models which could show the Orbits of Planets. One such clockwork model was presented to Charles Boyle, 4th Earl of Orrery and this how they became known as Orreries.

Features and Applications

Orries can show the positions of the Planets and their movements around the Sun but it is difficult to represent the Solar System to scale because of the great size of the Sun and Planets and the massive distances between them (measured in Astronomical Units or AUs) – especially if both the Inner Planets and Outer Planets are to be included.

Smaller, table-top size models overcome this by using different Scales for the diameters of the Planets and the distances they are from the Sun to create a model which a least indicates their size relative to each other. But even in this case the Sun is not scaled because it is so big - try the Exploratorium Calculator!

Larger Planetarum models attempt to provide a more realistic sense of scale and distance of the by projecting on to a dome or ceiling – usually this is limited to the Inner Planets. Scale models of the full Solar System can be set out in parks, on cycle routes or along public footpaths. One such model can be found in York where it is spread out along 10.2 km (6.4 miles) of the old East Coast main railway line. Details of the York Solar System model includes a map of where the Planets are located on the cycle route and how they where made, together with information relating to a smaller walking route within the York University Campus.

---

Activity: The order of the Planets starting from the Sun is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune (and once included Pluto which is now reclassified as a Dwarf Planet). The sequence can be remembered using a Mnemonic one example of which is a phrase in which the starting letter of each word is used to name the Planet such as: Many Vicars Eat Mushy Jam Sandwiches Under Netball Posts. Others exist but can you think of a new one of your own which does not include Pluto?

---

Making Model Orreries

An Orrery is a model of the Solar System which shows the positions of Planets around the Sun. The DT Online article Orrery Model shows how to make one using Stripwood Technology.

Working models can be made from construction kits such as Lego and Meccano as shown below. See also the NASA website Table-top Models for more ideas.

DT Online Buyers' Guide

Notes:

• MDF Discs which are pre-drilled are most useful if available, otherwise this might be done as preparation before using with younger children - alternatively a Hand Drill Stand could be used (if neccessary, adults or older children can cut them out of strips of MDF or Ply using a Holesaw).
• Dowels 4mm, 5mm, and 6mm are useful sizes for axles.
• Florist Wire is easily bent into shape whereas stiff wire, such as Brass Brazing Rod, is more suitable for connecting rods.

• See also Stripwood Components Buyers Guide and Stripwood Tools Buyers Guide

---

MDF and ply discs	Wood Dowel Rod	Wooden Clothes Pegs	Wooden Matchsticks for Craft	Wooden Lolly Sticks for Craft	Wooden Cocktail Sticks and Skewers for Craft	Unpainted Wooden Beads	Polystyrene Balls	Florists Wire	Brazing Rod
Cotton Reels	Wooden Spools	Copper Foil Tape	PVC Tube	Assorted Cable Ties	Hook and Loop Stick On Tape	Coloured Card for Craft	Greyboard	Cotton String	Elastic Bands