This year, October 31 was more than just Halloween. It was also the first global celebration of Dark Matter Day. In 25 countries, 11 US states and online, people interacted with scientists, watched demonstrations, viewed films, took in art exhibits and toured laboratories to learn about the ongoing search for dark matter.
Symmetry has collected a series of photos from participants around the world. Check out how people celebrated Dark Matter Day and download a commemorative dark matter poster (to be printed using visible matter).
![Photo of Strasbourg planetarium in France, visitors watched the program "Phantom of the Universe"](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_0-1_DarkMatterDayrecap_0.png?itok=WSBu4Grs)
At Strasbourg planetarium in France, visitors watched the program “Phantom of the Universe.”
![Photo of actress Tilda Swinton narrated the planetarium show, audiences viewed at different Dark Matter Day events](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_0-2_DarkMatterDayrecap_0.png?itok=yyRWSKF0)
Actress Tilda Swinton narrated the planetarium show, which audiences around the world viewed at different Dark Matter Day events.
![Photo of planetarium show in Strasbourg, visitors were jokingly warned never to challenge a theorist](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_0-3_DarkMatterDayrecap_0.png?itok=OZqvSD_S)
In a talk after the planetarium show in Strasbourg, visitors were jokingly warned never to challenge a theorist.
![Photo of speaker Pierre Van Hove, a physicist, discusses the search dark matter](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_0-4_DarkMatterDayrecap_0.png?itok=a9bUv45X)
Speaker Pierre Van Hove, a physicist based at Institut Pluridisiplinaire Hubert Curien (IPHC), discusses the search for dark matter at the Large Hadron Collider after the show in Strasbourg.
![Photo of visitors approaching Van Hove, who is on the CMS experiment at the LHC, after the talk](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_0-5_DarkMatterDayrecap_0.png?itok=1PkNvuv9)
Visitors approach Van Hove, who is on the CMS experiment at the LHC, after the talk.
![Peter Sorensen of Berkeley Lab gives a talk at the California Academy of Sciences in San Francisco on Oct. 31.](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_3_DarkMatterDayrecap_0.png?itok=LfHH5FWe)
Peter Sorensen of Berkeley Lab gave a talk at the California Academy of Sciences in San Francisco on October 31.
![Photo of employees at SLAC National Accelerator Laboratory celebrating Dark Matter Day with Facebook Live broadcasts](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_8_DarkMatterDayrecap.png?itok=Jw7lZp6J)
Employees at SLAC National Accelerator Laboratory celebrated Dark Matter Day with Facebook Live broadcasts related to two upcoming projects that will study dark matter, the LZ experiment at the Large Synoptic Survey Telescope.
![Bart Bernhardt, co-founder of Nerd Nite SF, donned a Dark Matter Day t-shirt during an October 18 event in San Francisco.](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_1_DarkMatterDayrecap.png?itok=BEjclcz-)
Bart Bernhardt, co-founder of Nerd Nite SF, donned a Dark Matter Day t-shirt during an October 18 event in San Francisco.
![Obi-Wan Kenobi was spotted in a Dark Matter Day t-shirt in the Berkeley Lab Strategic Communications office.](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_2_DarkMatterDayrecap.png?itok=aE6e2Os-)
Obi-Wan Kenobi was spotted in a Dark Matter Day t-shirt in the Berkeley Lab Strategic Communications office.
![Photo of children making their own dark matter particles during a workshop at STFC’s Rutherford Appleton Laboratory in the UK](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_7_DarkMatterDayrecap.png?itok=Fjv6CANd)
School children made their own dark matter particles during a workshop at STFC’s Rutherford Appleton Laboratory in the UK.
![Photo of the auditorium packed for a special "Talking Science" public lecture at STFC’s Daresbury Laboratory.](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_6_DarkMatterDayrecap.png?itok=qeLd0Wgg)
The auditorium was packed for a special “Talking Science” public lecture at STFC’s Daresbury Laboratory.
![In a Parliamentary showcase at the House of Commons, MPs met with leading UK dark matter experts (L-R): Tommy Sheppard MP, Carol](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_5_DarkMatterDayrecap.png?itok=T8qGEYIb)
In a Parliamentary showcase at the House of Commons, MPs met with leading UK dark matter experts (L-R): Tommy Sheppard MP, Carol Monaghan MP, Prof Carlos Frenk, Patrick Grady MP, Prof Alex Murphy, Prof Sean Paling, Prof Martin Hendry and Dr Brian Bowsher.
![Dark Matter Day event in Victoria Street, London. (L-R) Sean Paling, Director of the Boulby Underground Laboratory, with Greg](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_4_DarkMatterDayrecap.png?itok=emTGr6hU)
Dark Matter Day event in Victoria Street, London. (L-R) Sean Paling, Director of the Boulby Underground Laboratory, with Greg Clark MP (Secretary of State for Business, Energy & Industrial Strategy), Dr Laura Manenti, and Prof Carlos Frenk.
![Photo of NTI lecture hall on Campus South filled to the last seat and no standing room was available](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_9_DarkMatterDayrecap.png?itok=obGqlbcu)
The interest of the public in Karlsruhe, Germany, was so great that the NTI lecture hall on Campus South was filled to the last seat and no standing room was available.
![Photo of two Karlsruhe Institute of Technology researchers summarizing scientists' current understanding of dark matter](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_10_DarkMatterDayrecap_0.png?itok=L8Lscnhf)
Two Karlsruhe Institute of Technology researchers summarized scientists’ current understanding of dark matter and talked about new experiments seeking to uncover its mystery.
![Photo of the German laboratory DESY turned into an art gallery for Dark Matter Day](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_15_DarkMatterDayrecap.png?itok=rtMKSLCj)
The German laboratory DESY turned into an art gallery for Dark Matter Day.
![Photo of yellow and grey machinery in industrial space](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_14_DarkMatterDayrecap.png?itok=Jq9nKym7)
Fifteen artists took part, showing works they created after an intense period of exchange with DESY scientists.
![Photo of the HERA accelerator tunnel](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_13_DarkMatterDayrecap.png?itok=Ri-L0geK)
The artwork at DESY included a sound installation in the HERA accelerator tunnel.
![Photo of dark matter artwork at DESY was displayed in test halls, accelerator shafts and office corridors](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_12_DarkMatterDayrecap.png?itok=W8UUkXWY)
The dark matter artwork at DESY was displayed in test halls, accelerator shafts and office corridors.
![Photo of Dark Matter Day, the other works were topped off with a program of short films called “Dark Matters”](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_11_DarkMatterDayrecap.png?itok=xtzlF78I)
On Dark Matter Day, the other works were topped off with a program of short films called “Dark Matters” and a live link to the CMS experiment at CERN.
![Photo of The Institute of High Energy Physics, Chinese Academy of Sciences and Shanghai Jiao Tong University](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_19_DarkMatterDayrecap.png?itok=RYuNvXaN)
The Institute of High Energy Physics, Chinese Academy of Sciences and Shanghai Jiao Tong University organized an event in Shanghai.
![Photo of visitors lining up outside the Dark Matter Day event in Shanghai](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_18_DarkMatterDayrecap.png?itok=-4u6v6oM)
Visitors lined up outside the Dark Matter Day event in Shanghai.
![Photo of the event in Shanghai beginning with public lectures followed by free discussion between the public and the scientists](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_17_DarkMatterDayrecap.png?itok=D61hh6VS)
The event in Shanghai began with public lectures followed by free discussion between the public and the scientists.
![Photo of attendees at the Shanghai event also watched Phantom of the Universe – The Hunt for Dark Matter.](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_16_DarkMatterDayrecap.png?itok=h4uCzQkt)
Attendees at the Shanghai event also watched “Phantom of the Universe.”
![Photo of Dark Matter Day at CERN which, included a dark matter cake](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_24_DarkMatterDayrecap.png?itok=Pv9RQqYG)
Dark Matter Day at CERN included a dark matter cake.
![Photo of Katharine Leney, Researcher on the ATLAS experiment at CERN, introducing the principles of dark matter](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_23_DarkMatterDayrecap.png?itok=oGaejhUO)
Katharine Leney, a researcher on the ATLAS experiment at CERN, introduced the evening by presenting the basic principles of dark matter using her bespoke dark matter cake. Later in the evening Wessel Valkenburg, a research fellow in the Theory Department at CERN, explained the how and why research is carried out on dark matter.
![Photo of the 270 attendees onsite as well as on the live webcast learned from CERN experts about the experiments and theories](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_22_DarkMatterDayrecap.png?itok=LbQyhxJj)
More than 270 attendees onsite as well as on the live webcast learned from CERN experts about the experiments and theories that seek to provide us with a deeper understanding of this strange and unknown matter.
![Photo of CERN joining the global celebration of Dark Matter Day from the Globe of Science and Innovation](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_21_DarkMatterDayrecap.png?itok=g45vuBnr)
On Tuesday, October 31, CERN joined the global celebration of Dark Matter Day from the Globe of Science and Innovation
![Photo of some creative participants dressed up in costumes related to dark matter](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_20_DarkMatterDayrecap.png?itok=gtiXS1Ek)
With Dark Matter Day falling on Halloween, some creative participants came dressed up in costumes related to dark matter
![Photo of a volunteer demonstrating magnetism at a Dark Matter Day event at Adler Planetarium in Chicago](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_25_DarkMatterDayrecap_0.png?itok=9vf56LMc)
A volunteer demonstrated electrical repulsion at a Dark Matter Day event at Adler Planetarium in Chicago.
![Photo of jar of jellybeans at the Adler Planetarium event represents the make-up of the universe, mostly dark energy and DM](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_26_DarkMatterDayrecap_0.png?itok=RBm_1XIX)
A jar of jellybeans at the Adler Planetarium event represented the make-up of the universe, mostly dark energy and dark matter.
![Photo of visitors and volunteers talk particle accelerators at the Dark Matter Day event at Adler Planetarium](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_27_DarkMatterDayrecap_0.png?itok=hVMR6gON)
Visitors and volunteers talked particle accelerators at the Dark Matter Day event at Adler Planetarium in Chicago.
![Photo of Lindsay Forestell](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_28_DarkMatterDayrecap.png?itok=JL_7Qzao)
When asked, “What’s the most interesting thing about dark matter that you wish people knew more about?” Lindsay Forestell, TRIUMF PhD scientist, replied: “You could name me every element in the periodic table, show me how all of the proteins and molecules and proteins in your body work, or build me a rocket ship and fly me to the moon. At most you would still only understand less than 5 percent of what’s out there in the Universe.”
![Photo of Brookhaven Lab took three dark matter experts to a local bar for some lively conversation over food and drink](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_30_DarkMatterDayrecap.png?itok=7psCSIrk)
On October 24, Brookhaven Lab took three dark matter experts to a local bar for some lively conversation over food and drink.
![Photo of participants at Brookhaven Lab’s Dark Matter Day “PubSci” event interacted with Paul Stankus](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_29_DarkMatterDayRecap.png?itok=ll0VxVJW)
Participants at Brookhaven Lab’s Dark Matter Day “PubSci” event interacted with Paul Stankus of Oak Ridge National Laboratory, Neelima Sehgal of Stony Brook University, and Paul O’Connor of Brookhaven—with science communicator Justin Eure serving as master of ceremonies.
![Photo for Dark Matter Day at Sanford Lab, James Haiston Jr. (aka Quailman) and Jack Genovesi (aka Jack-in-the-Box)](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_31_DarkMatterDayrecap_0.png?itok=QzXx1G_t)
For Dark Matter Day at Sanford Lab, James Haiston Jr. (aka Quailman) and Jack Genovesi (aka Jack-in-the-Box) of the South Dakota School of Mines and Technology donned Halloween costumes to reprise a recent Comic Con panel on dark matter and its role in popular culture.
![Photo of “Everything we know about the universe—regular matter and energy—accounts for a fraction of the universe”](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_32_DarkMatterDayrecap_0.png?itok=AVfRFYZj)
“Everything we know about the universe—regular matter and energy—accounts for a fraction of the universe,” said Michael Dowding (aka Mr. Incredible) of the South Dakota School of Mines and Technology at Sanford Lab's Dark Matter Day event.
![Photo of Berkeley Lab scientist Dan McKinsey participated in a Reddit AMA about dark matter](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_33_DarkMatterDayrecap.png?itok=ctOQFXqX)
Berkeley Lab scientist Dan McKinsey participated in a Reddit AMA about dark matter.
![Photo of Kathryn Boast of University of Oxford's Department of Physics tweeted this photo of a Dark Matter Day jack-o'-lantern](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_34_DarkMatterDayrecap.png?itok=od91tasw)
Kathryn Boast of University of Oxford’s Department of Physics tweeted this photo of a Dark Matter Day jack-o’-lantern.
![Photo of China Science & Technology Museum hosted a Dark Matter Day event on November 5](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_35_DarkMatterDayrecap.png?itok=G1Ep5hxs)
China Science & Technology Museum hosted a Dark Matter Day event on November 5.
![Photo of four hundred people attended in person, and more than 50,000 people watched the online broadcast of the talks](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_36_DarkMatterDayrecap.png?itok=iXW_QUdL)
Four hundred people attended in person, and more than 50,000 people watched the online broadcast of the talks.
![Photo of science lovers of all ages attended the Dark Matter Day event in Beijing](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_37_DarkMatterDayrecap.png?itok=jMykmq2k)
Science lovers of all ages attended the Dark Matter Day event in Beijing.
![Photo of the event included talks by four experts and a showing of the film “Phantom of the Universe”](/sites/default/files/styles/2015_inset_one/public/images/standard/Slideshow_38_DarkMatterDayrecap.png?itok=jgtjIJCL)
The event included talks by four experts and a showing of the film “Phantom of the Universe”
Download the poster
![Illustration of hands hold galaxies in the palm of their hands with dark matter particles swirling around Dark Matter Day Poster](/sites/default/files/images/standard/Dark_Matter_Day_Poster.png)