{"product_id":"6-planet-mini-planetarium","title":"6-Planet Mini Planetarium","description":"\u003cp\u003eA minimalist hand-driven planetarium that turns the six classical planets — Mercury, Venus, Earth, Mars, Jupiter, and Saturn — at astronomically accurate relative speeds. 10 cm wide, 5 cm tall. A desk piece that models the solar system (as it was known in the 1700s!).\u003c\/p\u003e\u003cp\u003e \u003c\/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cu\u003eWhy only 6 planets?\u003c\/u\u003e\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eI came across a gear train for a planetarium that was designed by Scottish astronomer James Ferguson in the mid-1700s. At the time, Uranus and Neptune had not been discovered. His design used a single stacked gear to drive 6 planets, and I thought it was cool! In order to print it however, I had to include a dedicated connector gear for Jupiter-Saturn, as the teeth would have been too small to be printed. Description of the model can be found \u003ca target=\"_blank\" rel=\"noopener noreferrer ugc\" href=\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/e\/e4\/Life_of_James_Ferguson%2C_F.R.S._-_in_a_brief_autobiographical_account%2C_and_further_extended_memoir_-_with_numerous_notes_and_illustrative_engravings_%28IA_lifejamesfergus00hendgoog%29.pdf\"\u003epage 300 here\u003c\/a\u003e.\u003c\/p\u003e\u003cp\u003e \u003c\/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cu\u003eParts Required\u003c\/u\u003e\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eRequires 7 ball bearings with these diameters:\u003c\/p\u003e\u003cp\u003eSun = 12 mm\u003c\/p\u003e\u003cp\u003eMercury, Venus, Earth, Mars = 6 mm\u003c\/p\u003e\u003cp\u003eJupiter, Saturn = 8 mm\u003c\/p\u003e\u003cp\u003e \u003c\/p\u003e\u003cp\u003eI included spheres for printing, but I think marbles or ball bearings would look much better. You can get all you need for approx \u003ca target=\"_blank\" rel=\"noopener noreferrer ugc\" href=\"https:\/\/www.aliexpress.com\/item\/1005005478220120.html?spm=a2g0n.shopcart.shoppingCartRecommend.1.889538daynGNBm\u0026amp;gps-id=shoppingCartRecommend\u0026amp;scm=1007.13440.426876.0\u0026amp;scm_id=1007.13440.426876.0\u0026amp;scm-url=1007.13440.426876.0\u0026amp;pvid=dba1ce6d-80a4-48ca-adf7-58965f92268e\u0026amp;_t=gps-id%3AshoppingCartRecommend%2Cscm-url%3A1007.13440.426876.0%2Cpvid%3Adba1ce6d-80a4-48ca-adf7-58965f92268e%2Ctpp_buckets%3A668%232846%238108%231977\u0026amp;pdp_ext_f=%7B%22order%22%3A%22228%22%2C%22eval%22%3A%221%22%2C%22sceneId%22%3A%223440%22%2C%22fromPage%22%3A%22recommend%22%7D\u0026amp;pdp_npi=6%40dis%21EUR%219.51%219.51%21%21%2172.14%2172.14%21%400b88ac1917819931342991931e0e88%2112000033243882554%21rec%21IE%216310077030%21X%211%210%21n_tag%3A-29919%3Bd%3A465e1e40%3Bm03_new_user%3A-29895\u0026amp;utparam-url=scene%3AshoppingCartRecommend%7Cquery_from%3A%7Cx_object_id%3A1005005478220120%7C_p_origin_prod%3A\"\u003e€10 on ali express\u003c\/a\u003e. I used a copper ball for Earth just to add distinction. \u003c\/p\u003e\u003cp\u003e \u003c\/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cu\u003eOrbital Periods and Errors\u003c\/u\u003e\u003c\/strong\u003e\u003c\/p\u003e\u003cfigure class=\"table\"\u003e\u003ctable\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cstrong\u003e\u003cu\u003ePlanet\u003c\/u\u003e\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e\u003cu\u003eActual Period (days)\u003c\/u\u003e\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e\u003cu\u003eModel Period (days)\u003c\/u\u003e\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003e\u003cu\u003eError (%)\u003c\/u\u003e\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSaturn\u003c\/td\u003e\n\u003ctd\u003e10755\u003c\/td\u003e\n\u003ctd\u003e10733.87\u003c\/td\u003e\n\u003ctd\u003e0.19\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eJupiter\u003c\/td\u003e\n\u003ctd\u003e4331.74\u003c\/td\u003e\n\u003ctd\u003e4330.82\u003c\/td\u003e\n\u003ctd\u003e0.02\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMars\u003c\/td\u003e\n\u003ctd\u003e686.98\u003c\/td\u003e\n\u003ctd\u003e686.67\u003c\/td\u003e\n\u003ctd\u003e0.05\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEarth\u003c\/td\u003e\n\u003ctd\u003e365.25\u003c\/td\u003e\n\u003ctd\u003e365.25\u003c\/td\u003e\n\u003ctd\u003e0.00\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVenus\u003c\/td\u003e\n\u003ctd\u003e224.7\u003c\/td\u003e\n\u003ctd\u003e224.76\u003c\/td\u003e\n\u003ctd\u003e-0.03\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003e87.97\u003c\/td\u003e\n\u003ctd\u003e88.01\u003c\/td\u003e\n\u003ctd\u003e-0.04\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\u003c\/table\u003e\u003c\/figure\u003e\u003cp\u003eDesign by FelicksSulla on MakerWorld (license: BY).\u003c\/p\u003e","brand":"Mymadmanlab","offers":[{"title":"Default Title","offer_id":67372600328496,"sku":null,"price":7.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0987\/0809\/5280\/files\/0_7ce5d244-c96a-4b72-b1c6-95e969400e4e.png?v=1784130451","url":"https:\/\/mymadmanlab.com\/products\/6-planet-mini-planetarium","provider":"Mymadmanlab.com","version":"1.0","type":"link"}