Turning to the Einstein equations, we only need the time-time component R 00 = K ( T 00 − − 1 2 T g 00 ) the low speed and static field assumptions imply that T μ μ ν ν ≈ ≈ diag ⁡ ⁡ ( T 00 , 0 , 0 , 0 ) ≈ ≈ diag ⁡ ⁡ ( ρ ρ c 4 , 0 , 0 , 0 ) .