1. The problem statement, all variables and given/known data can liquid helium at 4k (.1 nanometers interatomic spacing) be modeled by non spreading wave packets? 2. Relevant equations 1/(√2π)∫∞-∞ei(kx-wt)Φ(k)dk W(k) was Taylor expanded to a quadratic term Δpx2/(2mħ) The book then sas for a non expanding wave packet: |t| << mħ/Δpx2 Another relation: |t| Δvx =|t| Δpx/m << ħ/Δpx = Δx 3. The attempt at a solution I'm not sure where to begin. I figure... Δx is 1×10^-10 meters Δp>ħ/Δx Then I could say |t| << mΔx2/ħ Which tell me t must be very small since we are talking about ≈ (10^-10)^2 Other then that I don't know where to go from here.