Question: The Zel'dovich number is a dimensionless number named after a scientist that died in what year?
Context: The Grashof number (Gr) is a dimensionless number in fluid dynamics and heat transfer which approximates the ratio of the buoyancy to viscous force acting on a fluid.  It frequently arises in the study of situations involving natural convection and is analogous to the Reynolds number.  It's believed to be named after Franz Grashof.  Though this grouping of terms had already been in use, it wasn't named until around 1921, 28 years after Franz Grashof's death.  It's not very clear why the grouping was named after him. Yakov Borisovich Zel'dovich {'1': ", '2': ", '3': 'ForMemRS', '4': "} (Belarusian: Якаў Барысавіч Зяльдовіч , Russian: Я́ков Бори́сович Зельдо́вич ; 8 March 1914 – 2 December 1987), also known as YaB, was a Russian physicist of Belarusian Jewish ethnicity, who is known for his prolific contributions in cosmology and the physics of thermonuclear and hydrodynamical phenomena. In viscous fluid dynamics, the Archimedes number (Ar) (not to be confused with Archimedes' constant, π), named after the ancient Greek scientist Archimedes is used to determine the motion of fluids due to density differences.  It is a dimensionless number defined as the ratio of external forces to internal viscous forces and has the form: The Womersley number (α) is a dimensionless number in biofluid mechanics.  It is a dimensionless expression of the pulsatile flow frequency in relation to viscous effects.  It is named after John R. Womersley (1907–1958) for his work with blood flow in arteries.  The Womersley number is important in keeping dynamic similarity when scaling an experiment.  An example of this is scaling up the vascular system for experimental study.  The Womersley number is also important in determining the thickness of the boundary layer to see if entrance effects can be ignored. The Marangoni number (Ma) is a dimensionless number named after Italian scientist Carlo Marangoni. The Zel'dovich number is a dimensionless number which provides a quantitative value for the activation energy of a chemical reaction which appears in the Arrhenius exponent, named after the Russian scientist Yakov Borisovich Zel'dovich. The Kapitza number (Ka) is a dimensionless number named after the prominent Russian physicist Pyotr Kapitsa (Peter Kapitza).  He provided the first extensive study of the ways in which a thin film of liquid flows down inclined surfaces.  Expressed as the ratio of surface tension forces to inertial forces, the Kapitza number acts as an indicator of the hydrodynamic wave regime in falling liquid films.  Liquid film behavior represents a subset of the more general class of free boundary problems. and is important in a wide range of engineering and technological applications such as evaporators, heat exchangers, absorbers, microreactors, small-scale electronics/microprocessor cooling schemes, air conditioning and gas turbine blade cooling. The Sunyaev–Zel'dovich effect (named after Rashid Sunyaev and Yakov B. Zel'dovich and often abbreviated as the SZ effect) is the distortion of the cosmic microwave background radiation (CMB) through inverse Compton scattering by high energy electrons in galaxy clusters, in which the low energy CMB photons receive an average energy boost during collision with the high energy cluster electrons.  Observed distortions of the cosmic microwave background spectrum are used to detect the density perturbations of the universe.  Using the Sunyaev–Zel'dovich effect, dense clusters of galaxies have been observed. In fluid dynamics, the Galilei number (Ga), sometimes also referred to as Galileo number (see discussion), is a dimensionless number named after Italian scientist Galileo Galilei (1564-1642). The Weissenberg number (Wi) is a dimensionless number used in the study of viscoelastic flows.  It is named after Karl Weissenberg.  The dimensionless number compares the viscous forces to the elastic forces.  It can be variously defined, but it is usually given by the relation of stress relaxation time of the fluid and a specific process time.  For instance, in simple steady shear, the Weissenberg number, often abbreviated as Wi or We, is defined as the shear rate formula_1 times the relaxation time formula_2.  Using the Maxwell Model and the Oldroyd Model, the elastic forces can be written as the first Normal force (N).
Answer: 1987