The year 1834 in science and technology included many events, some of which are listed here.

Astronomy

• Hermann Helmholtz proposes gravitational contraction as the energy source for the Sun
• Johann Heinrich von Mädler and Wilhelm Beer publish Mappa Selenographica, the most complete map of the moon up until that time
• Thomas Henderson appointed first astronomer-royal for Scotland

Biology

• James Paget discovers in human muscle the parasitic worm that causes trichinosis
• Félix Dujardin proposes that single-cell animals should be classified in a group by themselves

Geology

• The Triassic is named by Friedrich August von Alberti for the three distinct layers of redbeds, capped by chalk, followed by black shales that are found throughout Germany and Northwest Europe, called the 'Trias'

Mechanics

• Carl Gustav Jakob Jacobi discovers his uniformly rotating self-gravitating ellipsoids
• John Scott Russell observes a nondecaying solitary water wave (soliton) in the Union Canal near Edinburgh and uses a water tank to study the dependence of solitary water wave velocities on wave amplitude and water depth

Physics

• Émile Clapeyron presents a formulation of the second law of thermodynamics
• Heinrich Lenz discovers Lenz’s law
• Jean-Charles-Athanase Peltier discovers the Peltier effect
• Michael Faraday publishes "On Electrical Decomposition" in the Philosophical Transactions of the Royal Society (in which Faraday coins the words electrode, anode, cathode, anion, cation, electrolyte, electrolyze).

Awards

• Copley Medal: Giovanni Plana

Births

• January 7 – Johann Philipp Reis (d. 1874), physicist and inventor.
• January 15 - Frederick DuCane Godman (d. 1919), lepidopterist, entomologist and ornithologist.
• January 17 - August Weismann (d. 1914), biologist.
• February 7 – Dmitri Mendeleev (d. 1907), chemist.
• February 16 – Ernst Haeckel (d. 1919), zoologist.
• March 17 - Gottlieb Daimler (d. 1900), engineer and automotive pioneer.
• April 30 - John Lubbock (d. 1913), naturalist and archaeologist.
• August 5 – Ewald Hering (d. 1918), physiologist.
• August 22 – Samuel Pierpont Langley (d. 1906), astronomer.
• December 15 – Charles Augustus Young (d. 1908), astronomer.

Deaths

• February 16 – Lionel Lukin (b. 1742), inventor.
• February 26 – Alois Senefelder (b. 1771), inventor.
• August 7 – Joseph Marie Jacquard (b. 1752), inventor.
• October 10 – Thomas Say (b. 1787), naturalist.