diff --git a/src/amuse/units/constants_original.py b/src/amuse/units/constants_original.py
new file mode 100644
index 0000000000..113ed9682f
--- /dev/null
+++ b/src/amuse/units/constants_original.py
@@ -0,0 +1,351 @@
+"""
+Physical constants
+"""
+# This is an auto generated file, do not change manually. Instead if you want
+# to add constants or change them, change the nist.txt file and run nist.py
+
+import numpy
+from amuse.units.si import m, kg, s, A, K, mol, none
+from amuse.units.derivedsi import Hz, MHz, sr, N, Pa, J, W, F, C, V, T, ohm, S, Wb
+
+# BASE UNITS***********************************************
+X220X_lattice_spacing_of_silicon = 1.920155762e-10 | m
+alpha_particle_mass = 6.6446562e-27 | kg
+alpha_particle_mass_energy_equivalent = 5.97191917e-10 | J
+Angstrom_star = 1.00001498e-10 | m
+u = 1.660538782e-27 | kg
+atomic_mass_constant_energy_equivalent = 1.49241783e-10 | J
+atomic_mass_unit_hyphen_hertz_relationship = 2.2523427369e23 | Hz
+atomic_mass_unit_hyphen_joule_relationship = 1.49241783e-10 | J
+atomic_mass_unit_hyphen_kelvin_relationship = 1.0809527e13 | K
+atomic_mass_unit_hyphen_kilogram_relationship = 1.660538782e-27 | kg
+atomic_unit_of_charge = 1.602176487e-19 | C
+atomic_unit_of_current = 0.00662361763 | A
+atomic_unit_of_electric_potential = 27.21138386 | V
+atomic_unit_of_energy = 4.35974394e-18 | J
+atomic_unit_of_force = 8.23872206e-08 | N
+atomic_unit_of_length = 5.2917720859e-11 | m
+atomic_unit_of_mag_flux_density = 235051.7382 | T
+atomic_unit_of_mass = 9.10938215e-31 | kg
+atomic_unit_of_time = 2.4188843265e-17 | s
+Bohr_radius = 5.2917720859e-11 | m
+characteristic_impedance_of_vacuum = 376.730313461 | ohm
+classical_electron_radius = 2.8179402894e-15 | m
+Compton_wavelength = 2.4263102175e-12 | m
+Compton_wavelength_over_2_pi = 3.8615926459e-13 | m
+conductance_quantum = 7.7480917004e-05 | S
+conventional_value_of_von_Klitzing_constant = 25812.807 | ohm
+Cu_x_unit = 1.00207699e-13 | m
+deuteron_mass = 3.3435832e-27 | kg
+deuteron_mass_energy_equivalent = 3.00506272e-10 | J
+deuteron_rms_charge_radius = 2.1402e-15 | m
+electron_mass = 9.10938215e-31 | kg
+electron_mass_energy_equivalent = 8.18710438e-14 | J
+electron_volt = 1.602176487e-19 | J
+electron_volt_hyphen_hertz_relationship = 2.417989454e14 | Hz
+electron_volt_hyphen_joule_relationship = 1.602176487e-19 | J
+electron_volt_hyphen_kelvin_relationship = 11604.505 | K
+electron_volt_hyphen_kilogram_relationship = 1.782661758e-36 | kg
+elementary_charge = 1.602176487e-19 | C
+Hartree_energy = 4.35974394e-18 | J
+hartree_hyphen_hertz_relationship = 6.57968392072e15 | Hz
+hartree_hyphen_joule_relationship = 4.35974394e-18 | J
+hartree_hyphen_kelvin_relationship = 315774.65 | K
+hartree_hyphen_kilogram_relationship = 4.85086934e-35 | kg
+helion_mass = 5.00641192e-27 | kg
+helion_mass_energy_equivalent = 4.49953864e-10 | J
+hertz_hyphen_joule_relationship = 6.62606896e-34 | J
+hertz_hyphen_kelvin_relationship = 4.7992374e-11 | K
+hertz_hyphen_kilogram_relationship = 7.372496e-51 | kg
+inverse_meter_hyphen_hertz_relationship = 299792458.0 | Hz
+inverse_meter_hyphen_joule_relationship = 1.986445501e-25 | J
+inverse_meter_hyphen_kelvin_relationship = 0.014387752 | K
+inverse_meter_hyphen_kilogram_relationship = 2.2102187e-42 | kg
+inverse_of_conductance_quantum = 12906.4037787 | ohm
+joule_hyphen_hertz_relationship = 1.50919045e33 | Hz
+joule_hyphen_kelvin_relationship = 7.242963e22 | K
+joule_hyphen_kilogram_relationship = 1.112650056e-17 | kg
+kelvin_hyphen_hertz_relationship = 20836644000.0 | Hz
+kelvin_hyphen_joule_relationship = 1.3806504e-23 | J
+kelvin_hyphen_kilogram_relationship = 1.5361807e-40 | kg
+kilogram_hyphen_hertz_relationship = 1.356392733e50 | Hz
+kilogram_hyphen_joule_relationship = 8.987551787e16 | J
+kilogram_hyphen_kelvin_relationship = 6.509651e39 | K
+lattice_parameter_of_silicon = 5.43102064e-10 | m
+mag_flux_quantum = 2.067833667e-15 | Wb
+Mo_x_unit = 1.00209955e-13 | m
+muon_Compton_wavelength = 1.173444104e-14 | m
+muon_Compton_wavelength_over_2_pi = 1.867594295e-15 | m
+muon_mass = 1.8835313e-28 | kg
+muon_mass_energy_equivalent = 1.69283351e-11 | J
+natural_unit_of_energy = 8.18710438e-14 | J
+natural_unit_of_length = 3.8615926459e-13 | m
+natural_unit_of_mass = 9.10938215e-31 | kg
+natural_unit_of_time = 1.288088657e-21 | s
+neutron_Compton_wavelength = 1.3195908951e-15 | m
+neutron_Compton_wavelength_over_2_pi = 2.1001941382e-16 | m
+neutron_mass = 1.674927211e-27 | kg
+neutron_mass_energy_equivalent = 1.505349505e-10 | J
+Planck_length = 1.616252e-35 | m
+Planck_mass = 2.17644e-08 | kg
+Planck_temperature = 1.416785e32 | K
+Planck_time = 5.39124e-44 | s
+proton_Compton_wavelength = 1.3214098446e-15 | m
+proton_Compton_wavelength_over_2_pi = 2.1030890861e-16 | m
+proton_mass = 1.672621637e-27 | kg
+proton_mass_energy_equivalent = 1.503277359e-10 | J
+proton_rms_charge_radius = 8.768e-16 | m
+Rydberg_constant_times_c_in_Hz = 3.28984196036e15 | Hz
+Rydberg_constant_times_hc_in_J = 2.17987197e-18 | J
+standard_atmosphere = 101325.0 | Pa
+tau_Compton_wavelength = 6.9772e-16 | m
+tau_Compton_wavelength_over_2_pi = 1.11046e-16 | m
+tau_mass = 3.16777e-27 | kg
+tau_mass_energy_equivalent = 2.84705e-10 | J
+triton_mass = 5.00735588e-27 | kg
+triton_mass_energy_equivalent = 4.50038703e-10 | J
+unified_atomic_mass_unit = 1.660538782e-27 | kg
+von_Klitzing_constant = 25812.807557 | ohm
+# DERIVED UNITS***********************************************
+alpha_particle_molar_mass = 0.00400150617913 | kg * mol**-1
+atomic_mass_unit_hyphen_inverse_meter_relationship = 7.513006671e14 | m**-1
+atomic_unit_of_1st_hyperpolarizablity = 3.206361533e-53 | C**3 * m**3 * J**-2
+atomic_unit_of_2nd_hyperpolarizablity = 6.23538095e-65 | C**4 * m**4 * J**-3
+atomic_unit_of_action = 1.054571628e-34 | J * s
+atomic_unit_of_charge_density = 1.0812023e12 | C * m**-3
+atomic_unit_of_electric_dipole_mom = 8.47835281e-30 | C * m
+atomic_unit_of_electric_field = 5.14220632e11 | V * m**-1
+atomic_unit_of_electric_field_gradient = 9.71736166e21 | V * m**-2
+atomic_unit_of_electric_polarizablity = 1.6487772536e-41 | C**2 * m**2 * J**-1
+atomic_unit_of_electric_quadrupole_mom = 4.48655107e-40 | C * m**2
+atomic_unit_of_mag_dipole_mom = 1.85480183e-23 | J * T**-1
+atomic_unit_of_magnetizability = 7.891036433e-29 | J * T**-2
+atomic_unit_of_momentum = 1.992851565e-24 | kg * m * s**-1
+atomic_unit_of_permittivity = 1.112650056e-10 | F * m**-1
+atomic_unit_of_velocity = 2187691.2541 | m * s**-1
+Avogadro_constant = 6.02214179e23 | mol**-1
+Bohr_magneton = 9.27400915e-24 | J * T**-1
+Bohr_magneton_in_Hz_div_T = 13996246040.0 | Hz * T**-1
+Bohr_magneton_in_inverse_meters_per_tesla = 46.6864515 | m**-1 * T**-1
+Bohr_magneton_in_K_div_T = 0.6717131 | K * T**-1
+kB = 1.3806504e-23 | J * K**-1
+Boltzmann_constant_in_Hz_div_K = 20836644000.0 | Hz * K**-1
+Boltzmann_constant_in_inverse_meters_per_kelvin = 69.50356 | m**-1 * K**-1
+conventional_value_of_Josephson_constant = 4.835979e14 | Hz * V**-1
+deuteron_mag_mom = 4.33073465e-27 | J * T**-1
+deuteron_molar_mass = 0.00201355321272 | kg * mol**-1
+electric_constant = 8.854187817e-12 | F * m**-1
+electron_charge_to_mass_quotient = -1.75882015e11 | C * kg**-1
+electron_gyromag_ratio = 1.76085977e11 | s**-1 * T**-1
+electron_gyromag_ratio_over_2_pi = 28024.95364 | MHz * T**-1
+electron_mag_mom = -9.28476377e-24 | J * T**-1
+electron_molar_mass = 5.4857990943e-07 | kg * mol**-1
+electron_volt_hyphen_inverse_meter_relationship = 806554.465 | m**-1
+elementary_charge_over_h = 2.417989454e14 | A * J**-1
+Faraday_constant = 96485.3399 | C * mol**-1
+first_radiation_constant = 3.74177118e-16 | W * m**2
+first_radiation_constant_for_spectral_radiance = 1.191042759e-16 | W * m**2 * sr**-1
+hartree_hyphen_inverse_meter_relationship = 21947463.137 | m**-1
+helion_molar_mass = 0.0030149322473 | kg * mol**-1
+hertz_hyphen_inverse_meter_relationship = 3.335640951e-09 | m**-1
+Josephson_constant = 4.83597891e14 | Hz * V**-1
+joule_hyphen_inverse_meter_relationship = 5.03411747e24 | m**-1
+kelvin_hyphen_inverse_meter_relationship = 69.50356 | m**-1
+kilogram_hyphen_inverse_meter_relationship = 4.52443915e41 | m**-1
+Loschmidt_constant_X27315_K_and__101325_kPaX = 2.6867774e25 | m**-3
+mag_constant = 1.2566370614e-06 | N * A**-2
+molar_gas_constant = 8.314472 | J * mol**-1 * K**-1
+molar_mass_constant = 0.001 | kg * mol**-1
+molar_mass_of_carbon_hyphen_12 = 0.012 | kg * mol**-1
+molar_Planck_constant = 3.9903126821e-10 | J * s * mol**-1
+molar_Planck_constant_times_c = 0.11962656472 | J * m * mol**-1
+molar_volume_of_ideal_gas_X27315_K_and__100_kPaX = 0.022710981 | m**3 * mol**-1
+molar_volume_of_ideal_gas_X27315_K_and__101325_kPaX = 0.022413996 | m**3 * mol**-1
+molar_volume_of_silicon = 1.20588349e-05 | m**3 * mol**-1
+muon_mag_mom = -4.49044786e-26 | J * T**-1
+muon_molar_mass = 0.0001134289256 | kg * mol**-1
+natural_unit_of_action = 1.054571628e-34 | J * s
+natural_unit_of_momentum = 2.73092406e-22 | kg * m * s**-1
+natural_unit_of_velocity = 299792458.0 | m * s**-1
+neutron_gyromag_ratio = 183247185.0 | s**-1 * T**-1
+neutron_gyromag_ratio_over_2_pi = 29.1646954 | MHz * T**-1
+neutron_mag_mom = -9.6623641e-27 | J * T**-1
+neutron_molar_mass = 0.00100866491597 | kg * mol**-1
+G = 6.67428e-11 | m**3 * kg**-1 * s**-2
+nuclear_magneton = 5.05078324e-27 | J * T**-1
+nuclear_magneton_in_inverse_meters_per_tesla = 0.02542623616 | m**-1 * T**-1
+nuclear_magneton_in_K_div_T = 0.00036582637 | K * T**-1
+nuclear_magneton_in_MHz_div_T = 7.62259384 | MHz * T**-1
+h = 6.62606896e-34 | J * s
+Planck_constant_over_2_pi = 1.054571628e-34 | J * s
+proton_charge_to_mass_quotient = 95788339.2 | C * kg**-1
+proton_gyromag_ratio = 267522209.9 | s**-1 * T**-1
+proton_gyromag_ratio_over_2_pi = 42.5774821 | MHz * T**-1
+proton_mag_mom = 1.410606662e-26 | J * T**-1
+proton_molar_mass = 0.00100727646677 | kg * mol**-1
+quantum_of_circulation = 0.00036369475199 | m**2 * s**-1
+quantum_of_circulation_times_2 = 0.000727389504 | m**2 * s**-1
+Rydberg_constant = 10973731.5685 | m**-1
+second_radiation_constant = 0.014387752 | m * K
+shielded_helion_gyromag_ratio = 203789473.0 | s**-1 * T**-1
+shielded_helion_gyromag_ratio_over_2_pi = 32.43410198 | MHz * T**-1
+shielded_helion_mag_mom = -1.074552982e-26 | J * T**-1
+shielded_proton_gyromag_ratio = 267515336.2 | s**-1 * T**-1
+shielded_proton_gyromag_ratio_over_2_pi = 42.5763881 | MHz * T**-1
+shielded_proton_mag_mom = 1.410570419e-26 | J * T**-1
+c = 299792458.0 | m * s**-1
+standard_acceleration_of_gravity = 9.80665 | m * s**-2
+Stefan_hyphen_Boltzmann_constant = 5.6704e-08 | W * m**-2 * K**-4
+tau_molar_mass = 0.00190768 | kg * mol**-1
+Thomson_cross_section = 6.652458558e-29 | m**2
+triton_mag_mom = 1.504609361e-26 | J * T**-1
+triton_molar_mass = 0.0030155007134 | kg * mol**-1
+Wien_frequency_displacement_law_constant = 58789330000.0 | Hz * K**-1
+Wien_wavelength_displacement_law_constant = 0.0028977685 | m * K
+# RATIOS ***********************************************
+alpha_particle_hyphen_electron_mass_ratio = 7294.2995365 | none
+alpha_particle_hyphen_proton_mass_ratio = 3.97259968951 | none
+deuteron_hyphen_electron_mag_mom_ratio = -0.0004664345537 | none
+deuteron_hyphen_electron_mass_ratio = 3670.4829654 | none
+deuteron_g_factor = 0.8574382308 | none
+deuteron_mag_mom_to_Bohr_magneton_ratio = 0.0004669754556 | none
+deuteron_mag_mom_to_nuclear_magneton_ratio = 0.8574382308 | none
+deuteron_hyphen_neutron_mag_mom_ratio = -0.44820652 | none
+deuteron_hyphen_proton_mag_mom_ratio = 0.307012207 | none
+deuteron_hyphen_proton_mass_ratio = 1.99900750108 | none
+electron_hyphen_deuteron_mag_mom_ratio = -2143.923498 | none
+electron_hyphen_deuteron_mass_ratio = 0.00027244371093 | none
+electron_g_factor = -2.00231930436 | none
+electron_mag_mom_anomaly = 0.00115965218111 | none
+electron_mag_mom_to_Bohr_magneton_ratio = -1.00115965218 | none
+electron_mag_mom_to_nuclear_magneton_ratio = -1838.28197092 | none
+electron_hyphen_muon_mag_mom_ratio = 206.7669877 | none
+electron_hyphen_muon_mass_ratio = 0.00483633171 | none
+electron_hyphen_neutron_mag_mom_ratio = 960.9205 | none
+electron_hyphen_neutron_mass_ratio = 0.00054386734459 | none
+electron_hyphen_proton_mag_mom_ratio = -658.2106848 | none
+electron_hyphen_proton_mass_ratio = 0.00054461702177 | none
+electron_hyphen_tau_mass_ratio = 0.000287564 | none
+electron_to_alpha_particle_mass_ratio = 0.00013709335557 | none
+electron_to_shielded_helion_mag_mom_ratio = 864.058257 | none
+electron_to_shielded_proton_mag_mom_ratio = -658.2275971 | none
+fine_hyphen_structure_constant = 0.0072973525376 | none
+helion_hyphen_electron_mass_ratio = 5495.8852765 | none
+helion_hyphen_proton_mass_ratio = 2.9931526713 | none
+inverse_fine_hyphen_structure_constant = 137.035999679 | none
+muon_hyphen_electron_mass_ratio = 206.7682823 | none
+muon_g_factor = -2.0023318414 | none
+muon_mag_mom_anomaly = 0.00116592069 | none
+muon_mag_mom_to_Bohr_magneton_ratio = -0.00484197049 | none
+muon_mag_mom_to_nuclear_magneton_ratio = -8.89059705 | none
+muon_hyphen_neutron_mass_ratio = 0.1124545167 | none
+muon_hyphen_proton_mag_mom_ratio = -3.183345137 | none
+muon_hyphen_proton_mass_ratio = 0.1126095261 | none
+muon_hyphen_tau_mass_ratio = 0.0594592 | none
+neutron_hyphen_electron_mag_mom_ratio = 0.00104066882 | none
+neutron_hyphen_electron_mass_ratio = 1838.6836605 | none
+neutron_g_factor = -3.82608545 | none
+neutron_mag_mom_to_Bohr_magneton_ratio = -0.00104187563 | none
+neutron_mag_mom_to_nuclear_magneton_ratio = -1.91304273 | none
+neutron_hyphen_muon_mass_ratio = 8.89248409 | none
+neutron_hyphen_proton_mag_mom_ratio = -0.68497934 | none
+neutron_hyphen_proton_mass_ratio = 1.00137841918 | none
+neutron_hyphen_tau_mass_ratio = 0.52874 | none
+neutron_to_shielded_proton_mag_mom_ratio = -0.68499694 | none
+proton_hyphen_electron_mass_ratio = 1836.15267247 | none
+proton_g_factor = 5.585694713 | none
+proton_mag_mom_to_Bohr_magneton_ratio = 0.001521032209 | none
+proton_mag_mom_to_nuclear_magneton_ratio = 2.792847356 | none
+proton_mag_shielding_correction = 2.5694e-05 | none
+proton_hyphen_muon_mass_ratio = 8.88024339 | none
+proton_hyphen_neutron_mag_mom_ratio = -1.45989806 | none
+proton_hyphen_neutron_mass_ratio = 0.99862347824 | none
+proton_hyphen_tau_mass_ratio = 0.528012 | none
+Sackur_hyphen_Tetrode_constant_X1_K_and__100_kPaX = -1.1517047 | none
+Sackur_hyphen_Tetrode_constant_X1_K_and__101325_kPaX = -1.1648677 | none
+shielded_helion_mag_mom_to_Bohr_magneton_ratio = -0.001158671471 | none
+shielded_helion_mag_mom_to_nuclear_magneton_ratio = -2.127497718 | none
+shielded_helion_to_proton_mag_mom_ratio = -0.761766558 | none
+shielded_helion_to_shielded_proton_mag_mom_ratio = -0.7617861313 | none
+shielded_proton_mag_mom_to_Bohr_magneton_ratio = 0.001520993128 | none
+shielded_proton_mag_mom_to_nuclear_magneton_ratio = 2.792775598 | none
+tau_hyphen_electron_mass_ratio = 3477.48 | none
+tau_hyphen_muon_mass_ratio = 16.8183 | none
+tau_hyphen_neutron_mass_ratio = 1.89129 | none
+tau_hyphen_proton_mass_ratio = 1.8939 | none
+triton_hyphen_electron_mag_mom_ratio = -0.001620514423 | none
+triton_hyphen_electron_mass_ratio = 5496.9215269 | none
+triton_g_factor = 5.957924896 | none
+triton_mag_mom_to_Bohr_magneton_ratio = 0.001622393657 | none
+triton_mag_mom_to_nuclear_magneton_ratio = 2.978962448 | none
+triton_hyphen_neutron_mag_mom_ratio = -1.55718553 | none
+triton_hyphen_proton_mag_mom_ratio = 1.066639908 | none
+triton_hyphen_proton_mass_ratio = 2.9937170309 | none
+weak_mixing_angle = 0.22255 | none
+# DERIVED CONSTANTS***********************************************
+pi = numpy.pi
+hbar = h / (2.0 * numpy.pi)
+four_pi_stefan_boltzmann = 4.0 * numpy.pi * Stefan_hyphen_Boltzmann_constant
+mu0 = 4 * numpy.pi * 1.0e-7 | N / A**2
+eps0 = mu0**-1 * c**-2
+sidereal_day = 86164.100352 | s
+# machine constants
+eps = numpy.finfo(numpy.double).eps
+precision = int(numpy.log10(2 / eps))
+# DROPPED UNITS***********************************************
+"""alpha_particle_mass_energy_equivalent_in_MeV = 3727.379109 | MeV
+alpha_particle_mass_in_u = 4.00150617913 | u
+atomic_mass_constant_energy_equivalent_in_MeV = 931.494028 | MeV
+atomic_mass_unit_hyphen_electron_volt_relationship = 931494028.0 | eV
+atomic_mass_unit_hyphen_hartree_relationship = 34231777.149 | E_h
+Bohr_magneton_in_eV_div_T = 5.7883817555e-05 | eV*T**-1
+kBeV = 8.617343e-05 | eV*K**-1
+deuteron_mass_energy_equivalent_in_MeV = 1875.612793 | MeV
+deuteron_mass_in_u = 2.01355321272 | u
+electron_mass_energy_equivalent_in_MeV = 0.51099891 | MeV
+electron_mass_in_u = 0.00054857990943 | u
+electron_volt_hyphen_atomic_mass_unit_relationship = 1.073544188e-09 | u
+electron_volt_hyphen_hartree_relationship = 0.0367493254 | E_h
+Faraday_constant_for_conventional_electric_current = 96485.3401 | C_90*mol**-1
+Fermi_coupling_constant = 1.16637e-05 | GeV**-2
+hartree_hyphen_atomic_mass_unit_relationship = 2.9212622986e-08 | u
+hartree_hyphen_electron_volt_relationship = 27.21138386 | eV
+Hartree_energy_in_eV = 27.21138386 | eV
+helion_mass_energy_equivalent_in_MeV = 2808.391383 | MeV
+helion_mass_in_u = 3.0149322473 | u
+hertz_hyphen_atomic_mass_unit_relationship = 4.4398216294e-24 | u
+hertz_hyphen_electron_volt_relationship = 4.13566733e-15 | eV
+hertz_hyphen_hartree_relationship = 1.51982984601e-16 | E_h
+inverse_meter_hyphen_atomic_mass_unit_relationship = 1.3310250394e-15 | u
+inverse_meter_hyphen_electron_volt_relationship = 1.239841875e-06 | eV
+inverse_meter_hyphen_hartree_relationship = 4.55633525276e-08 | E_h
+joule_hyphen_atomic_mass_unit_relationship = 6700536410.0 | u
+joule_hyphen_electron_volt_relationship = 6.24150965e+18 | eV
+joule_hyphen_hartree_relationship = 2.29371269e+17 | E_h
+kelvin_hyphen_atomic_mass_unit_relationship = 9.251098e-14 | u
+kelvin_hyphen_electron_volt_relationship = 8.617343e-05 | eV
+kelvin_hyphen_hartree_relationship = 3.1668153e-06 | E_h
+kilogram_hyphen_atomic_mass_unit_relationship = 6.02214179e+26 | u
+kilogram_hyphen_electron_volt_relationship = 5.60958912e+35 | eV
+kilogram_hyphen_hartree_relationship = 2.06148616e+34 | E_h
+muon_mass_energy_equivalent_in_MeV = 105.6583668 | MeV
+muon_mass_in_u = 0.1134289256 | u
+natural_unit_of_action_in_eV_s = 6.58211899e-16 | eV*s
+natural_unit_of_energy_in_MeV = 0.51099891 | MeV
+natural_unit_of_momentum_in_MeV_div_c = 0.51099891 | MeV/c
+neutron_mass_energy_equivalent_in_MeV = 939.565346 | MeV
+neutron_mass_in_u = 1.00866491597 | u
+Newtonian_constant_of_gravitation_over_h_hyphen_bar_c = 6.70881e-39 | (GeV/c**2)**-2
+nuclear_magneton_in_eV_div_T = 3.1524512326e-08 | eV*T**-1
+heV = 4.13566733e-15 | eV*s
+Planck_constant_over_2_pi_in_eV_s = 6.58211899e-16 | eV*s
+Planck_constant_over_2_pi_times_c_in_MeV_fm = 197.3269631 | MeV*fm
+Planck_mass_energy_equivalent_in_GeV = 1.220892e+19 | GeV
+proton_mass_energy_equivalent_in_MeV = 938.272013 | MeV
+proton_mass_in_u = 1.00727646677 | u
+Rydberg_constant_times_hc_in_eV = 13.60569193 | eV
+tau_mass_energy_equivalent_in_MeV = 1776.99 | MeV
+tau_mass_in_u = 1.90768 | u
+triton_mass_energy_equivalent_in_MeV = 2808.920906 | MeV
+triton_mass_in_u = 3.0155007134 | u
+"""
diff --git a/src/amuse/units/units.py b/src/amuse/units/units.py
index 92f2fb8c3d..fbfd2b4d81 100644
--- a/src/amuse/units/units.py
+++ b/src/amuse/units/units.py
@@ -1,5 +1,7 @@
 """
-Units supported in AMUSE
+Units supported in AMUSE - 2025 version
+Values are taken to be the same as in Astropy (default unit set).
+If/when they are not, this file should be updated.
 """
 
 import numpy
@@ -21,7 +23,7 @@
 minute = named("minute", "min", 60.0 * s)
 hour = named("hour", "hr", 60.0 * minute)
 day = named("day", "day", 24.0 * hour)
-yr = named("year", "yr", 365.242199 * day)
+yr = named("year", "yr", 365.25 * day)
 julianyr = named("julian yr", "julianyr", 365.25 * day)
 ms = named("meter per seconds", "ms", m / s)
 kms = named("kilometer per seconds", "kms", km / s)
@@ -43,20 +45,20 @@
 
 # astronomical units
 angstrom = named("angstrom", "angstrom", 1e-10 * m)
-au = named("astronomical unit", "au", 149597870691.0 * m)
-aud = named("au per day", "aud", 149597870691.0 * m / day)
+au = named("astronomical unit", "au", 149597870700.0 * m)
+aud = named("au per day", "aud",  au / day)
 parsec = named("parsec", "parsec", au / numpy.tan(numpy.pi / (180 * 60 * 60)))
 kpc = named("kilo parsec", "kpc", 10**3 * parsec)
 Mpc = named("mega parsec", "Mpc", 10**6 * parsec)
 Gpc = named("giga parsec", "Gpc", 10**9 * parsec)
-lightyear = named("light year", "ly", 9460730472580.8 * km)
-LSun = named("solar luminosity", "LSun", 3.839e26 * W, latex=r"L_{\odot}")
-MSun = named("solar mass", "MSun", 1.98892e30 * kg, latex=r"M_{\odot}")
-RSun = named("solar radius", "RSun", 6.955e8 * m, latex=r"R_{\odot}")
-MJupiter = named("jupiter mass", "MJupiter", 1.8987e27 * kg)
-RJupiter = named("jupiter radius", "RJupiter", 71492.0 * km)
-MEarth = named("earth mass", "MEarth", 5.9722e24 * kg)
-REarth = named("earth radius", "REarth", 6371.0088 * km)  # IUGG mean radius
+lightyear = named("light year", "ly", 9460730472580800.0 * m)
+LSun = named("solar luminosity", "LSun", 3.828e26 * W, latex=r"L_{\odot}")
+MSun = named("solar mass", "MSun", 1.988409870698051e+30 * kg, latex=r"M_{\odot}")
+RSun = named("solar radius", "RSun", 695700000.0 * m, latex=r"R_{\odot}")
+MJupiter = named("jupiter mass", "MJupiter", 1.8981245973360505e+27 * kg)
+RJupiter = named("jupiter radius", "RJupiter", 71492000.0 * m)
+MEarth = named("earth mass", "MEarth", 5.972167867791379e+24 * kg)
+REarth = named("earth radius", "REarth", 6378100.0 * m)  # IUGG mean radius
 kyr = named("kilo year", "kyr", 1000 * yr)
 myr = named("million year", "Myr", 1000000 * yr)
 gyr = named("giga (billion) year", "Gyr", 1000000000 * yr)
@@ -83,8 +85,9 @@
 
 # imperial distance units
 inch = named("inch", "in", 0.0254 * m)
-foot = named("foot", "ft", 0.3048 * m)
-mile = named("mile", "mi", 1609.344 * m)
+foot = named("foot", "ft", 12 * inch)
+yard = named("yard", "yd", 3 * foot)
+mile = named("mile", "mi", 5280 * foot)
 
 percent = named("percent", "%", 0.01 * none)
 metallicity = core.none_unit("metallicity", "metallicity")
diff --git a/src/amuse/units/units_original.py b/src/amuse/units/units_original.py
new file mode 100644
index 0000000000..92f2fb8c3d
--- /dev/null
+++ b/src/amuse/units/units_original.py
@@ -0,0 +1,102 @@
+"""
+Units supported in AMUSE
+"""
+
+import numpy
+from . import constants
+from . import quantities
+
+# The two imports below are to explicitly expose everything directly used in
+# this module.
+from .si import (named, s, m, kg, none, core, no_unit,)
+from .derivedsi import (km, V, W, J, Pa, rad,)
+
+# importing * from si and derivedsi since we do want all of the units in these
+# modules, and we don't want to repeat everything here.
+from .si import *
+from .derivedsi import *
+from .stellar_types import stellar_type
+
+# misc every day
+minute = named("minute", "min", 60.0 * s)
+hour = named("hour", "hr", 60.0 * minute)
+day = named("day", "day", 24.0 * hour)
+yr = named("year", "yr", 365.242199 * day)
+julianyr = named("julian yr", "julianyr", 365.25 * day)
+ms = named("meter per seconds", "ms", m / s)
+kms = named("kilometer per seconds", "kms", km / s)
+
+# units based on measured quantities
+e = named("electron charge", "e", constants.elementary_charge.as_unit())
+eV = named("electron volt", "eV", e * V)
+MeV = named("mega electron volt", "MeV", 1e6 * eV)
+GeV = named("giga electron volt", "GeV", 1e9 * eV)
+E_h = named("hartree energy", "E_h", constants.Hartree_energy.as_unit())
+amu = named("atomic mass unit", "amu", constants.u.as_unit())
+Ry = named(
+    "rydberg unit",
+    "Ry",
+    (constants.Rydberg_constant * constants.h * constants.c)
+    .as_quantity_in(eV)
+    .as_unit(),
+)
+
+# astronomical units
+angstrom = named("angstrom", "angstrom", 1e-10 * m)
+au = named("astronomical unit", "au", 149597870691.0 * m)
+aud = named("au per day", "aud", 149597870691.0 * m / day)
+parsec = named("parsec", "parsec", au / numpy.tan(numpy.pi / (180 * 60 * 60)))
+kpc = named("kilo parsec", "kpc", 10**3 * parsec)
+Mpc = named("mega parsec", "Mpc", 10**6 * parsec)
+Gpc = named("giga parsec", "Gpc", 10**9 * parsec)
+lightyear = named("light year", "ly", 9460730472580.8 * km)
+LSun = named("solar luminosity", "LSun", 3.839e26 * W, latex=r"L_{\odot}")
+MSun = named("solar mass", "MSun", 1.98892e30 * kg, latex=r"M_{\odot}")
+RSun = named("solar radius", "RSun", 6.955e8 * m, latex=r"R_{\odot}")
+MJupiter = named("jupiter mass", "MJupiter", 1.8987e27 * kg)
+RJupiter = named("jupiter radius", "RJupiter", 71492.0 * km)
+MEarth = named("earth mass", "MEarth", 5.9722e24 * kg)
+REarth = named("earth radius", "REarth", 6371.0088 * km)  # IUGG mean radius
+kyr = named("kilo year", "kyr", 1000 * yr)
+myr = named("million year", "Myr", 1000000 * yr)
+gyr = named("giga (billion) year", "Gyr", 1000000000 * yr)
+
+# alternatives, for compatibility
+AU = au
+AUd = aud
+Myr = myr
+Gyr = gyr
+pc = parsec
+Lsun = LSun
+Msun = MSun
+Rsun = RSun
+Mjupiter = MJupiter
+Rjupiter = RJupiter
+Mearth = MEarth
+Rearth = REarth
+
+# cgs units
+g = named("gram", "g", 1e-3 * kg)
+cm = named("centimeter", "cm", 0.01 * m)
+erg = named("erg", "erg", 1e-7 * J)
+barye = named("barye", "Ba", 0.1 * Pa)
+
+# imperial distance units
+inch = named("inch", "in", 0.0254 * m)
+foot = named("foot", "ft", 0.3048 * m)
+mile = named("mile", "mi", 1609.344 * m)
+
+percent = named("percent", "%", 0.01 * none)
+metallicity = core.none_unit("metallicity", "metallicity")
+
+string = core.string_unit("string", "string")
+
+# special unit for keys of particles
+object_key = core.key_unit("object_key", "key")
+
+# angles
+pi = numpy.pi | rad
+rev = named("revolutions", "rev", (2 * numpy.pi) * rad)
+deg = named("degree", "deg", (numpy.pi / 180) * rad)
+arcmin = named("arcminutes", "arcmin", (1.0 / 60) * deg)
+arcsec = named("arcseconds", "arcsec", (1.0 / 3600) * deg)