We find new quantitative estimates on the space-time analyticity of solutions to linear parabolic equations with time-independent coefficients and apply them to obtain observability inequalities for its solutions over measurable sets.1991 Mathematics Subject Classification. Primary: 35B37.Theorem 2. Assume that J ⊂ ∂Ω × (0, T ) is a measurable set with positive surface measure in ∂Ω × (0, T ). Then, there is N = N (Ω, J, T, δ) such that the inequality