diff --git a/src/Simulation9.java b/src/Simulation9.java
index b0b7429..4286283 100644
--- a/src/Simulation9.java
+++ b/src/Simulation9.java
@@ -1,8 +1,122 @@
+import codedraw.CodeDraw;
+
+import java.awt.*;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Iterator;
+
 /**
  * Simulates the solar system.
  */
 public class Simulation9 {
 
-    // TODO: Implement the simulation using the Java-Collections framework.
+    // gravitational constant
+    public static final double G = 6.6743e-11;
 
+    // one astronomical unit (AU) is the average distance of earth to the sun.
+    public static final double AU = 150e9; // meters
+
+    // set some system parameters
+    public static final double SECTION_SIZE = 10 * AU; // the size of the square region in space
+
+    // all quantities are based on units of kilogram respectively second and meter.
+
+    // The main simulation method using instances of other classes.
+    public static void main(String[] args) {
+        if (args.length != 2) {
+            System.err.println("Error: wrong number of arguments.");
+            System.exit(1);
+        }
+
+        String statePath = args[0];
+        String date;
+        try {
+            date = ReadDataUtil.convertDate(args[1]);
+        } catch (IllegalArgumentException e) {
+            System.err.println("Error: State has wrong format (requires YYYY-MMM-DD), aborting.");
+            System.exit(2);
+            return;
+        }
+
+        // simulation
+        CodeDraw cd = new CodeDraw();
+
+        // create solar system with 13 bodies
+        HashMap<Massive, Vector3> forceOnBody = new HashMap<>();
+
+        forceOnBody.put(new NamedBody("Oumuamua", 8e6), new Vector3());
+        forceOnBody.put(new NamedBody("Earth", 5.972E24), new Vector3());
+        forceOnBody.put(new NamedBody("Moon", 7.349E22), new Vector3());
+        forceOnBody.put(new NamedBody("Mars", 6.41712E23), new Vector3());
+        forceOnBody.put(new NamedBody("Deimos", 1.8E20), new Vector3());
+        forceOnBody.put(new NamedBody("Phobos", 1.08E20), new Vector3());
+        forceOnBody.put(new NamedBody("Mercury", 3.301E23), new Vector3());
+        forceOnBody.put(new NamedBody("Venus", 4.86747E24), new Vector3());
+        forceOnBody.put(new NamedBody("Vesta", 2.5908E20), new Vector3());
+        forceOnBody.put(new NamedBody("Pallas", 2.14E20), new Vector3());
+        forceOnBody.put(new NamedBody("Hygiea", 8.32E19), new Vector3());
+        forceOnBody.put(new NamedBody("Ceres", 9.394E20), new Vector3());
+
+        Iterator<Massive> iter = forceOnBody.keySet().iterator();
+        while (iter.hasNext()) {
+            Massive a = iter.next();
+            if (a instanceof NamedBody b) {
+                boolean remove = false;
+
+                try {
+                    boolean found = ReadDataUtil.readConfiguration(b, statePath + "/" + b.getName() + ".txt", date);
+                    if (!found) {
+                        System.err.println("Warning: State not available for " + b.getName() + ".");
+                        remove = true;
+                    }
+                } catch (IOException e) {
+                    if (e instanceof StateFileNotFoundException notFound) {
+                        System.err.println("Warning: " + notFound.getMessage());
+                    } else if (e instanceof StateFileFormatException format) {
+                        System.err.println("Warning: " + format.getMessage());
+                    } else {
+                        System.err.println("Error: " + e.getMessage());
+                        System.exit(3);
+                    }
+                    remove = true;
+                }
+
+                if (remove) {
+                    System.err.println("Running simulation without " + b.getName());
+                    iter.remove();
+                }
+            }
+        }
+
+        // add sun after states have been read from files.
+        forceOnBody.put(new NamedBody("Sun", 1.989E30), new Vector3());
+
+        System.out.println("Starting simulation");
+        long seconds = 0;
+        while (true) {
+            seconds++;
+
+            for (Massive b1 : forceOnBody.keySet()) {
+                Vector3 force = new Vector3();
+                for (Massive b2 : forceOnBody.keySet()) {
+                    if (b1 != b2) {
+                        force = force.plus(b1.gravitationalForce(b2));
+                    }
+                }
+                forceOnBody.put(b1, force);
+            }
+
+            for (Massive body : forceOnBody.keySet()) {
+                body.move(forceOnBody.get(body));
+            }
+
+            if ((seconds % 3600) == 0) {
+                cd.clear(Color.BLACK);
+                for (Massive body : forceOnBody.keySet()) {
+                    body.draw(cd);
+                }
+                cd.show();
+            }
+        }
+    }
 }