S03E15: The Large Hadron Collision
Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.
Previous Episode 
Season 1
Pilot
S1E1 / 24 Sep 2007
The Big Bran Hypothesis
S1E2 / 01 Oct 2007
The Fuzzy Boots Corollary
S1E3 / 08 Oct 2007
The Luminous Fish Effect
S1E4 / 15 Oct 2007
The Hamburger Postulate
S1E5 / 22 Oct 2007
The Middle-Earth Paradigm
S1E6 / 29 Oct 2007
The Dumpling Paradox
S1E7 / 05 Nov 2007
The Grasshopper Experiment
S1E8 / 12 Nov 2007
The Cooper-Hofstadter Polarization
S1E9 / 17 Mar 2008
The Loobenfeld Decay
S1E10 / 24 Mar 2008
The Pancake Batter Anomaly
S1E11 / 31 Mar 2008
The Jerusalem Duality
S1E12 / 14 Apr 2008
The Bat Jar Conjecture
S1E13 / 21 Apr 2008
The Nerdvana Annihilation
S1E14 / 28 Apr 2008
The Pork Chop Indeterminacy
S1E15 / 05 May 2008
The Peanut Reaction
S1E16 / 12 May 2008
The Tangerine Factor
S1E17 / 19 May 2008
Season 2
The Bad Fish Paradigm
S2E1 / 22 Sep 2008
The Codpiece Topology
S2E2 / 29 Sep 2008
The Barbarian Sublimation
S2E3 / 06 Oct 2008
The Griffin Equivalency
S2E4 / 13 Oct 2008
The Euclid Alternative
S2E5 / 20 Oct 2008
The Cooper-Nowitzki Theorem
S2E6 / 03 Nov 2008
The Panty Piñata Polarization
S2E7 / 10 Nov 2008
The Lizard-Spock Expansion
S2E8 / 17 Nov 2008
The White Asparagus Triangulation
S2E9 / 24 Nov 2008
The Vartabedian Conundrum
S2E10 / 08 Dec 2008
The Bath Item Gift Hypothesis
S2E11 / 15 Dec 2008
The Killer Robot Instability
S2E12 / 12 Jan 2009
The Friendship Algorithm
S2E13 / 19 Jan 2009
The Financial Permeability
S2E14 / 02 Feb 2009
The Maternal Capacitance
S2E15 / 09 Feb 2009
The Cushion Saturation
S2E16 / 02 Mar 2009
The Terminator Decoupling
S2E17 / 09 Mar 2009
The Work Song Nanocluster
S2E18 / 16 Mar 2009
The Dead Hooker Juxtaposition
S2E19 / 30 Mar 2009
The Hofstadter Isotope
S2E20 / 13 Apr 2009
The Vegas Renormalization
S2E21 / 27 Apr 2009
The Classified Materials Turbulence
S2E22 / 04 May 2009
The Monopolar Expedition
S2E23 / 11 May 2009
Season 3
The Electric Can Opener Fluctuation
S3E1 / 21 Sep 2009
The Jiminy Conjecture
S3E2 / 28 Sep 2009
The Gothowitz Deviation
S3E3 / 05 Oct 2009
The Pirate Solution
S3E4 / 12 Oct 2009
The Creepy Candy Coating Corollary
S3E5 / 19 Oct 2009
The Cornhusker Vortex
S3E6 / 02 Nov 2009
The Guitarist Amplification
S3E7 / 09 Nov 2009
The Adhesive Duck Deficiency
S3E8 / 16 Nov 2009
The Vengeance Formulation
S3E9 / 23 Nov 2009
The Gorilla Experiment
S3E10 / 07 Dec 2009
The Maternal Congruence
S3E11 / 14 Dec 2009
The Psychic Vortex
S3E12 / 11 Jan 2010
The Bozeman Reaction
S3E13 / 18 Jan 2010
The Einstein Approximation
S3E14 / 01 Feb 2010
The Large Hadron Collision
S3E15 / 08 Feb 2010
The Excelsior Acquisition
S3E16 / 01 Mar 2010
The Precious Fragmentation
S3E17 / 08 Mar 2010
The Pants Alternative
S3E18 / 22 Mar 2010
The Wheaton Recurrence
S3E19 / 12 Apr 2010
The Spaghetti Catalyst
S3E20 / 03 May 2010
The Plimpton Stimulation
S3E21 / 10 May 2010
The Staircase Implementation
S3E22 / 17 May 2010
The Lunar Excitation
S3E23 / 24 May 2010
Season 4
The Robotic Manipulation
S4E1 / 23 Sep 2010
The Cruciferous Vegetable Amplification
S4E2 / 30 Sep 2010
The Zazzy Substitution
S4E3 / 07 Oct 2010
The Hot Troll Deviation
S4E4 / 14 Oct 2010
The Desperation Emanation
S4E5 / 21 Oct 2010
The Irish Pub Formulation
S4E6 / 28 Oct 2010
The Apology Insufficiency
S4E7 / 04 Nov 2010
The 21-Second Excitation
S4E8 / 11 Nov 2010
The Boyfriend Complexity
S4E9 / 18 Nov 2010
The Alien Parasite Hypothesis
S4E10 / 09 Dec 2010
The Justice League Recombination
S4E11 / 16 Dec 2010
The Bus Pants Utilization
S4E12 / 06 Jan 2011
The Love Car Displacement
S4E13 / 20 Jan 2011
The Thespian Catalyst
S4E14 / 03 Feb 2011
The Benefactor Factor
S4E15 / 10 Feb 2011
The Cohabitation Formulation
S4E16 / 17 Feb 2011
The Toast Derivation
S4E17 / 24 Feb 2011
The Prestidigitation Approximation
S4E18 / 10 Mar 2011
The Zarnecki Incursion
S4E19 / 31 Mar 2011
The Herb Garden Germination
S4E20 / 07 Apr 2011
The Agreement Dissection
S4E21 / 28 Apr 2011
The Wildebeest Implementation
S4E22 / 05 May 2011
The Engagement Reaction
S4E23 / 12 May 2011
The Roommate Transmogrification
S4E24 / 19 May 2011
Season 5
The Skank Reflex Analysis
S5E1 / 22 Sep 2011
The Infestation Hypothesis
S5E2 / 22 Sep 2011
The Pulled Groin Extrapolation
S5E3 / 29 Sep 2011
The Wiggly Finger Catalyst
S5E4 / 06 Oct 2011
The Russian Rocket Reaction
S5E5 / 13 Oct 2011
The Rhinitis Revelation
S5E6 / 20 Oct 2011
The Good Guy Fluctuation
S5E7 / 27 Oct 2011
The Isolation Permutation
S5E8 / 03 Nov 2011
The Ornithophobia Diffusion
S5E9 / 10 Nov 2011
The Flaming Spittoon Acquisition
S5E10 / 17 Nov 2011
The Speckerman Recurrence
S5E11 / 08 Dec 2011
The Shiny Trinket Maneuver
S5E12 / 12 Jan 2012
The Recombination Hypothesis
S5E13 / 19 Jan 2012
The Beta Test Initiation
S5E14 / 26 Jan 2012
The Friendship Contraction
S5E15 / 02 Feb 2012
The Vacation Solution
S5E16 / 09 Feb 2012
The Rothman Disintegration
S5E17 / 16 Feb 2012
The Werewolf Transformation
S5E18 / 23 Feb 2012
The Weekend Vortex
S5E19 / 08 Mar 2012
The Transporter Malfunction
S5E20 / 29 Mar 2012
The Hawking Excitation
S5E21 / 05 Apr 2012
The Stag Convergence
S5E22 / 26 Apr 2012
The Launch Acceleration
S5E23 / 03 May 2012
The Countdown Reflection
S5E24 / 10 May 2012
Season 6
The Date Night Variable
S6E1 / 27 Sep 2012
The Decoupling Fluctuation
S6E2 / 04 Oct 2012
The Higgs Boson Observation
S6E3 / 11 Oct 2012
The Re-Entry Minimization
S6E4 / 18 Oct 2012
The Holographic Excitation
S6E5 / 25 Oct 2012
The Extract Obliteration
S6E6 / 01 Nov 2012
The Habitation Configuration
S6E7 / 08 Nov 2012
The 43 Peculiarity
S6E8 / 15 Nov 2012
The Parking Spot Escalation
S6E9 / 29 Nov 2012
The Fish Guts Displacement
S6E10 / 06 Dec 2012
The Santa Simulation
S6E11 / 13 Dec 2012
The Egg Salad Equivalency
S6E12 / 03 Jan 2013
The Bakersfield Expedition
S6E13 / 10 Jan 2013
The Cooper/Kripke Inversion
S6E14 / 31 Jan 2013
The Spoiler Alert Segmentation
S6E15 / 07 Feb 2013
The Tangible Affection Proof
S6E16 / 14 Feb 2013
The Monster Isolation
S6E17 / 21 Feb 2013
The Contractual Obligation Implementation
S6E18 / 07 Mar 2013
The Closet Reconfiguration
S6E19 / 14 Mar 2013
The Tenure Turbulence
S6E20 / 04 Apr 2013
The Closure Alternative
S6E21 / 25 Apr 2013
The Proton Resurgence
S6E22 / 02 May 2013
The Love Spell Potential
S6E23 / 09 May 2013
The Bon Voyage Reaction
S6E24 / 16 May 2013
Season 7
The Hofstadter Insufficiency
S7E1 / 26 Sep 2013
The Deception Verification
S7E2 / 26 Sep 2013
The Scavenger Vortex
S7E3 / 03 Oct 2013
The Raiders Minimization
S7E4 / 10 Oct 2013
The Workplace Proximity
S7E5 / 17 Oct 2013
The Romance Resonance
S7E6 / 24 Oct 2013
The Proton Displacement
S7E7 / 07 Nov 2013
The Itchy Brain Simulation
S7E8 / 14 Nov 2013
The Thanksgiving Decoupling
S7E9 / 21 Nov 2013
The Discovery Dissipation
S7E10 / 05 Dec 2013
The Cooper Extraction
S7E11 / 12 Dec 2013
The Hesitation Ramification
S7E12 / 02 Jan 2014
The Occupation Recalibration
S7E13 / 09 Jan 2014
The Convention Conundrum
S7E14 / 30 Jan 2014
The Locomotive Manipulation
S7E15 / 06 Feb 2014
The Table Polarization
S7E16 / 27 Feb 2014
The Friendship Turbulence
S7E17 / 06 Mar 2014
The Mommy Observation
S7E18 / 13 Mar 2014
The Indecision Amalgamation
S7E19 / 03 Apr 2014
The Relationship Diremption
S7E20 / 10 Apr 2014
The Anything Can Happen Recurrence
S7E21 / 24 Apr 2014
The Proton Transmogrification
S7E22 / 01 May 2014
The Gorilla Dissolution
S7E23 / 08 May 2014
The Status Quo Combustion
S7E24 / 15 May 2014
Season 8
The Locomotion Interruption
S8E1 / 22 Sep 2014
The Junior Professor Solution
S8E2 / 22 Sep 2014
The First Pitch Insufficiency
S8E3 / 29 Sep 2014
The Hook-Up Reverberation
S8E4 / 06 Oct 2014
The Focus Attenuation
S8E5 / 13 Oct 2014
The Expedition Approximation
S8E6 / 20 Oct 2014
The Misinterpretation Agitation
S8E7 / 30 Oct 2014
The Prom Equivalency
S8E8 / 06 Nov 2014
The Septum Deviation
S8E9 / 13 Nov 2014
The Champagne Reflection
S8E10 / 20 Nov 2014
The Clean Room Infiltration
S8E11 / 11 Dec 2014
The Space Probe Disintegration
S8E12 / 08 Jan 2015
The Anxiety Optimization
S8E13 / 29 Jan 2015
The Troll Manifestation
S8E14 / 05 Feb 2015
The Comic Book Store Regeneration
S8E15 / 19 Feb 2015
The Intimacy Acceleration
S8E16 / 26 Feb 2015
The Colonization Application
S8E17 / 05 Mar 2015
The Leftover Thermalization
S8E18 / 12 Mar 2015
The Skywalker Incursion
S8E19 / 02 Apr 2015
The Fortification Implementation
S8E20 / 09 Apr 2015
The Communication Deterioration
S8E21 / 16 Apr 2015
The Graduation Transmission
S8E22 / 23 Apr 2015
The Maternal Combustion
S8E23 / 30 Apr 2015
The Commitment Determination
S8E24 / 07 May 2015
Season 9
The Matrimonial Momentum
S9E1 / 21 Sep 2015
The Separation Oscillation
S9E2 / 28 Sep 2015
The Bachelor Party Corrosion
S9E3 / 05 Oct 2015
The 2003 Approximation
S9E4 / 12 Oct 2015
The Perspiration Implementation
S9E5 / 19 Oct 2015
The Helium Insufficiency
S9E6 / 26 Oct 2015
The Spock Resonance
S9E7 / 05 Nov 2015
The Mystery Date Observation
S9E8 / 12 Nov 2015
The Platonic Permutation
S9E9 / 19 Nov 2015
The Earworm Reverberation
S9E10 / 10 Dec 2015
The Opening Night Excitation
S9E11 / 17 Dec 2015
The Sales Call Sublimation
S9E12 / 07 Jan 2016
The Empathy Optimization
S9E13 / 14 Jan 2016
The Meemaw Materialization
S9E14 / 04 Feb 2016
The Valentino Submergence
S9E15 / 11 Feb 2016
The Positive Negative Reaction
S9E16 / 18 Feb 2016
The Celebration Experimentation
S9E17 / 25 Feb 2016
The Application Deterioration
S9E18 / 10 Mar 2016
The Solder Excursion Diversion
S9E19 / 31 Mar 2016
The Big Bear Precipitation
S9E20 / 07 Apr 2016
The Viewing Party Combustion
S9E21 / 21 Apr 2016
The Fermentation Bifurcation
S9E22 / 28 Apr 2016
The Line Substitution Solution
S9E23 / 05 May 2016
The Convergence Convergence
S9E24 / 12 May 2016
Season 10
The Conjugal Conjecture
S10E1 / 19 Sep 2016
The Military Miniaturization
S10E2 / 26 Sep 2016
The Dependence Transcendence
S10E3 / 03 Oct 2016
The Cohabitation Experimentation
S10E4 / 10 Oct 2016
The Hot Tub Contamination
S10E5 / 17 Oct 2016
The Fetal Kick Catalyst
S10E6 / 27 Oct 2016
The Veracity Elasticity
S10E7 / 03 Nov 2016
The Brain Bowl Incubation
S10E8 / 10 Nov 2016
The Geology Elevation
S10E9 / 17 Nov 2016
The Property Division Collision
S10E10 / 01 Dec 2016
The Birthday Synchronicity
S10E11 / 15 Dec 2016
The Holiday Summation
S10E12 / 05 Jan 2017
The Romance Recalibration
S10E13 / 19 Jan 2017
The Emotion Detection Automation
S10E14 / 02 Feb 2017
The Locomotion Reverberation
S10E15 / 09 Feb 2017
The Allowance Evaporation
S10E16 / 16 Feb 2017
The Comic-Con Conundrum
S10E17 / 23 Feb 2017
The Escape Hatch Identification
S10E18 / 09 Mar 2017
The Collaboration Fluctuation
S10E19 / 30 Mar 2017
The Recollection Dissipation
S10E20 / 06 Apr 2017
The Separation Agitation
S10E21 / 13 Apr 2017
The Cognition Regeneration
S10E22 / 27 Apr 2017
The Gyroscopic Collapse
S10E23 / 04 May 2017
The Long Distance Dissonance
S10E24 / 11 May 2017
Season 11
The Proposal Proposal
S11E1 / 25 Sep 2017
The Retraction Reaction
S11E2 / 02 Oct 2017
The Relaxation Integration
S11E3 / 09 Oct 2017
The Explosion Implosion
S11E4 / 16 Oct 2017
The Collaboration Contamination
S11E5 / 23 Oct 2017
The Proton Regeneration
S11E6 / 02 Nov 2017
The Geology Methodology
S11E7 / 09 Nov 2017
The Tesla Recoil
S11E8 / 16 Nov 2017
The Bitcoin Entanglement
S11E9 / 30 Nov 2017
The Confidence Erosion
S11E10 / 07 Dec 2017
The Celebration Reverberation
S11E11 / 14 Dec 2017
The Matrimonial Metric
S11E12 / 04 Jan 2018
The Solo Oscillation
S11E13 / 11 Jan 2018
The Separation Triangulation
S11E14 / 18 Jan 2018
The Novelization Correlation
S11E15 / 01 Feb 2018
The Neonatal Nomenclature
S11E16 / 01 Mar 2018
The Athenaeum Allocation
S11E17 / 08 Mar 2018
The Gates Excitation
S11E18 / 29 Mar 2018
The Tenant Disassociation
S11E19 / 05 Apr 2018
The Reclusive Potential
S11E20 / 12 Apr 2018
The Comet Polarization
S11E21 / 19 Apr 2018
The Monetary Insufficiency
S11E22 / 26 Apr 2018
The Sibling Realignment
S11E23 / 03 May 2018
The Bow Tie Asymmetry
S11E24 / 10 May 2018
Season 12
The Conjugal Configuration
S12E1 / 24 Sep 2018
The Wedding Gift Wormhole
S12E2 / 27 Sep 2018
The Procreation Calculation
S12E3 / 04 Oct 2018
The Tam Turbulence
S12E4 / 11 Oct 2018
The Planetarium Collision
S12E5 / 18 Oct 2018
The Imitation Perturbation
S12E6 / 25 Oct 2018
The Grant Allocation Derivation
S12E7 / 01 Nov 2018
The Consummation Deviation
S12E8 / 08 Nov 2018
The Citation Negation
S12E9 / 15 Nov 2018
The VCR Illumination
S12E10 / 06 Dec 2018
The Paintball Scattering
S12E11 / 03 Jan 2019
The Propagation Proposition
S12E12 / 10 Jan 2019
The Confirmation Polarization
S12E13 / 17 Jan 2019
The Meteorite Manifestation
S12E14 / 31 Jan 2019
The Donation Oscillation
S12E15 / 07 Feb 2019
The D & D Vortex
S12E16 / 21 Feb 2019
The Conference Valuation
S12E17 / 07 Mar 2019
The Laureate Accumulation
S12E18 / 04 Apr 2019
The Inspiration Deprivation
S12E19 / 18 Apr 2019
The Decision Reverberation
S12E20 / 25 Apr 2019
The Plagiarism Schism
S12E21 / 02 May 2019
The Maternal Conclusion
S12E22 / 09 May 2019
The Change Constant / The Stockholm Syndrome
S12E23 / 16 May 2019
Unraveling the Mystery: A Big Bang Farewell
S12E24 / 16 May 2019
Johnny Galecki
Leonard Hofstadter
Jim Parsons
Sheldon Cooper
Kaley Cuoco
Penny
Simon Helberg
Howard Wolowitz
Kunal Nayyar
Rajesh Koothrappali
Melissa Rauch
Bernadette Rostenkowski
