diff --git a/src/main.cpp b/src/main.cpp
index 992a39c..4df46cf 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -103,9 +103,8 @@ int main()
 
     // set parameters of moon's orbit around earth
     Orbit orbit;
-    orbit.setSemiMajorAxis(1.0);             // in km
-    // TODO: implement zoom
-    //orbit.setSemiMajorAxis(384748);             // in km
+    double semiMajorAxis =  3.84748e9;
+    orbit.setSemiMajorAxis(semiMajorAxis);          // metres
     orbit.setEccentricity(0.055);
     orbit.setInclination(glm::radians(5.15));   // radians?
     orbit.setArgumentOfPeriapsis(318.15);       // in the case of the moon these last two values are
@@ -117,9 +116,10 @@ int main()
     map.setParticle({"earth", 5.9e24});
     map.setParticle({"moon", 7.3e22});
     map.setRelationship("earth", "moon", orbit);
-    ParticleVisualizer earthVis(map, "earth", 0.2, litProgram, unlitProgram);
-    ParticleVisualizer moonVis(map, "moon", 0.1, litProgram, unlitProgram);
-    OrbitVisualizer orbitVis(orbit, unlitProgram);
+    float scale = semiMajorAxis * 1.1;
+    ParticleVisualizer earthVis(map, "earth", 0.2, litProgram, unlitProgram, scale);
+    ParticleVisualizer moonVis(map, "moon", 0.1, litProgram, unlitProgram, scale);
+    OrbitVisualizer orbitVis(orbit, unlitProgram, scale);
 
     // register input
     glfwSetKeyCallback(window, keyCallback);
diff --git a/src/orbitvisualizer.cpp b/src/orbitvisualizer.cpp
index 03a4e58..258f970 100644
--- a/src/orbitvisualizer.cpp
+++ b/src/orbitvisualizer.cpp
@@ -1,8 +1,8 @@
 #include "orbitvisualizer.hpp"
 #include "gfx.hpp"
 
-OrbitVisualizer::OrbitVisualizer(const Orbit& orbit, const GLuint shaderProgram)
-    : _orbit(orbit), _shaderProgram(shaderProgram)
+OrbitVisualizer::OrbitVisualizer(const Orbit& orbit, const GLuint shaderProgram, float scale)
+    : _orbit(orbit), _shaderProgram(shaderProgram), _scale(scale)
 {
     glGenVertexArrays(1, &_vao);
     glGenBuffers(1, &_vbo);
@@ -36,6 +36,8 @@ void OrbitVisualizer::regenerateVertices()
         pos.y = y;
         pos.z *= -1;
 
+        pos /= _scale;
+
         _vertices.push_back(pos.x);
         _vertices.push_back(pos.y);
         _vertices.push_back(pos.z);
diff --git a/src/orbitvisualizer.hpp b/src/orbitvisualizer.hpp
index fb925b3..db9be6a 100644
--- a/src/orbitvisualizer.hpp
+++ b/src/orbitvisualizer.hpp
@@ -7,7 +7,7 @@
 class OrbitVisualizer
 {
     public:
-        OrbitVisualizer(const Orbit& orbit, const GLuint shaderProgram);
+        OrbitVisualizer(const Orbit& orbit, const GLuint shaderProgram, float scale);
         ~OrbitVisualizer();
 
         void render(const float time);
@@ -18,6 +18,7 @@ class OrbitVisualizer
         const int _vertexCount = 100;
         const GLuint _shaderProgram;
         const Orbit& _orbit;
+        const float _scale;
 
         GLuint _vbo;
         GLuint _vao;
diff --git a/src/particlevisualizer.cpp b/src/particlevisualizer.cpp
index 9d83445..82fa1bf 100644
--- a/src/particlevisualizer.cpp
+++ b/src/particlevisualizer.cpp
@@ -1,8 +1,9 @@
 #include "particlevisualizer.hpp"
 
 ParticleVisualizer::ParticleVisualizer(const ParticleMap& map, const std::string& particleId, float radius,
-        GLuint sphereShaderProgram, GLuint widgetShaderProgram)
-    : _map(map), _particleId(particleId), _sphere({radius, 2, sphereShaderProgram}), _widget(widgetShaderProgram)
+        GLuint sphereShaderProgram, GLuint widgetShaderProgram, float scale)
+    : _map(map), _particleId(particleId), _sphere({radius, 2, sphereShaderProgram}),
+        _widget(widgetShaderProgram), _scale(scale)
 {
 }
 
@@ -16,6 +17,8 @@ void ParticleVisualizer::render(float time)
     pos.y = y;
     pos.z *= -1;
 
+    pos /= _scale;
+
     // TODO: extract widget to its own visualizer since we know it wants an orbit but we
     // might not have one here
     //// render widget
diff --git a/src/particlevisualizer.hpp b/src/particlevisualizer.hpp
index d16c987..2cce070 100644
--- a/src/particlevisualizer.hpp
+++ b/src/particlevisualizer.hpp
@@ -8,7 +8,8 @@
 class ParticleVisualizer
 {
     public:
-        ParticleVisualizer(const ParticleMap& map, const std::string& particleId, float radius, GLuint sphereShaderProgram, GLuint widgetShaderProgram);
+        ParticleVisualizer(const ParticleMap& map, const std::string& particleId, float radius,
+                GLuint sphereShaderProgram, GLuint widgetShaderProgram, float scale);
         ~ParticleVisualizer() = default;
 
         void render(float time);
@@ -18,6 +19,7 @@ class ParticleVisualizer
 
         const ParticleMap& _map;
         const std::string _particleId;
+        const float _scale;
         Icosphere _sphere;
         Widget _widget;
 };