diff --git a/utils/__init__.py b/utils/__init__.py
new file mode 100644
index 0000000..40b2d11
--- /dev/null
+++ b/utils/__init__.py
@@ -0,0 +1,5 @@
+from constants import *
+from math import *
+from os_tools import *
+from plotting import *
+from simulation import *
diff --git a/utils/constants.py b/utils/constants.py
new file mode 100644
index 0000000..a48c1f7
--- /dev/null
+++ b/utils/constants.py
@@ -0,0 +1,5 @@
+solar_radius = 6.957e8
+solar_mass = 1.9885e+30
+
+earth_water_mass = 1.7e21  # Lécuyer et al. 1998
+earth_mass = 5.9722e24
diff --git a/utils/math.py b/utils/math.py
new file mode 100644
index 0000000..a100e25
--- /dev/null
+++ b/utils/math.py
@@ -0,0 +1,4 @@
+def clamp(n: float, smallest: float, largest: float) -> float:
+    assert smallest < largest
+    return max(smallest, min(n, largest))
+
diff --git a/utils/os_tools.py b/utils/os_tools.py
new file mode 100644
index 0000000..a230c1b
--- /dev/null
+++ b/utils/os_tools.py
@@ -0,0 +1,39 @@
+import os
+import subprocess
+from pathlib import Path
+import socket
+from sys import argv
+
+from setproctitle import setproctitle
+
+def filename_from_argv(argument: str = None) -> Path:
+    if len(argv) < 2:
+        raise ValueError("specify filename")
+    if argument:
+        fn = argument
+    else:
+        fn = argv[1]
+    fn = fn.replace(".bin", "").replace(".meta.json", "")
+    if fn.endswith("."):
+        fn = fn[:-1]
+    return Path(fn.replace(".bin", "").replace(".meta.json", ""))
+
+
+def git_hash() -> str:
+    output = subprocess.run(["git", "rev-parse", "--verify", "HEAD"], capture_output=True)
+    return output.stdout.decode()
+
+
+def check_heartbeat_needs_recompile() -> None:
+    library = Path("heartbeat/heartbeat.so")
+    code = library.with_suffix(".c")
+    if code.stat().st_mtime > library.stat().st_mtime:
+        raise RuntimeError("heartbeat.so is out of date. Please recompile it from source.")
+
+
+def process_friendlyness(fn: Path) -> None:
+    if socket.gethostname() == "standpc":
+        # only handle other computers specially
+        return
+    setproctitle(f"[{fn.stem}] [rebound-watersim] read /home/winklerl23/sim-info.txt for more information")
+    os.nice(5)
diff --git a/utils/plotting.py b/utils/plotting.py
new file mode 100644
index 0000000..91a2a55
--- /dev/null
+++ b/utils/plotting.py
@@ -0,0 +1,14 @@
+from typing import Tuple
+
+from matplotlib import pyplot as plt
+from matplotlib.axes import Axes
+from matplotlib.figure import Figure
+
+
+def create_figure() -> Tuple[Figure, Axes]:
+    """
+    helper function for matplotlib OOP interface with proper typing
+    """
+    fig: Figure = plt.figure()
+    ax: Axes = fig.gca()
+    return fig, ax
diff --git a/utils.py b/utils/simulation.py
similarity index 63%
rename from utils.py
rename to utils/simulation.py
index b782300..9b6b46a 100644
--- a/utils.py
+++ b/utils/simulation.py
@@ -1,24 +1,13 @@
-import os
-import socket
-import subprocess
 from ctypes import c_uint32
-from pathlib import Path
 from random import randint
-from sys import argv
-from typing import Tuple, Dict
+from typing import Dict
 
-from matplotlib import pyplot as plt
-from matplotlib.axes import Axes
-from matplotlib.figure import Figure
 from numpy import linalg
-from rebound import Simulation, Orbit, Particle, OrbitPlot
+from rebound import Simulation, Orbit, OrbitPlot, Particle
 from scipy.constants import pi, gravitational_constant
-from setproctitle import setproctitle
 
 from extradata import ExtraData
-
-solar_radius = 6.957e8
-solar_mass = 1.9885e+30
+from utils import solar_mass
 
 
 def random_hash() -> c_uint32:
@@ -76,38 +65,11 @@ def show_orbits(sim: Simulation):
     OrbitPlot(sim, slices=1, color=True)
     plt.show()
 
-
-def clamp(n: float, smallest: float, largest: float) -> float:
-    assert smallest < largest
-    return max(smallest, min(n, largest))
-
-
-def filename_from_argv(argument: str = None) -> Path:
-    if len(argv) < 2:
-        raise ValueError("specify filename")
-    if argument:
-        fn = argument
-    else:
-        fn = argv[1]
-    fn = fn.replace(".bin", "").replace(".meta.json", "")
-    if fn.endswith("."):
-        fn = fn[:-1]
-    return Path(fn.replace(".bin", "").replace(".meta.json", ""))
-
-
-def create_figure() -> Tuple[Figure, Axes]:
-    """
-    helper function for matplotlib OOP interface with proper typing
-    """
-    fig: Figure = plt.figure()
-    ax: Axes = fig.gca()
-    return fig, ax
-
-
 def reorder_particles(sim: Simulation, ed: ExtraData) -> None:
     """
     probably not needed anymore
     """
+    exit()
     particles_by_hash: Dict[int, Particle] = {}
     hashes = []
     suns = []
@@ -151,23 +113,3 @@ def reorder_particles(sim: Simulation, ed: ExtraData) -> None:
     # TODO: double-check meaning
     sim.testparticle_type = 1
     assert sim.N == original_N
-
-
-def git_hash() -> str:
-    output = subprocess.run(["git", "rev-parse", "--verify", "HEAD"], capture_output=True)
-    return output.stdout.decode()
-
-
-def check_heartbeat_needs_recompile() -> None:
-    library = Path("heartbeat/heartbeat.so")
-    code = library.with_suffix(".c")
-    if code.stat().st_mtime > library.stat().st_mtime:
-        raise RuntimeError("heartbeat.so is out of date. Please recompile it from source.")
-
-
-def process_friendlyness(fn: Path) -> None:
-    if socket.gethostname() == "standpc":
-        # only handle other computers specially
-        return
-    setproctitle(f"[{fn.stem}] [rebound-watersim] read /home/winklerl23/sim-info.txt for more information")
-    os.nice(5)