diff --git a/src/Universe.spec.ts b/src/Universe.spec.ts
index df93e1c..8e74297 100644
--- a/src/Universe.spec.ts
+++ b/src/Universe.spec.ts
@@ -3,13 +3,49 @@ import Universe from './Universe'
 import Vector from './Vector'
 
 describe('Universe', () => {
+  describe('parameter validation', () => {
+    it('should throw error if deltaTimeSegments is not a positive integer', () => {
+      expect(() => new Universe({
+        bodies: [],
+        deltaTimeSegments: 0,
+        changeCallback: () => {}
+      })).toThrow('deltaTimeSegments must be a positive integer')
+
+      expect(() => new Universe({
+        bodies: [],
+        deltaTimeSegments: -1,
+        changeCallback: () => {}
+      })).toThrow('deltaTimeSegments must be a positive integer')
+
+      expect(() => new Universe({
+        bodies: [],
+        deltaTimeSegments: 1.1,
+        changeCallback: () => {}
+      })).toThrow('deltaTimeSegments must be a positive integer')
+    })
+
+    it('should throw error if simulationInterval is not positive', () => {
+      expect(() => new Universe({
+        bodies: [],
+        simulationInterval: 0,
+        changeCallback: () => {}
+      })).toThrow('simulationInterval must be positive')
+
+      expect(() => new Universe({
+        bodies: [],
+        simulationInterval: -1,
+        changeCallback: () => {}
+      })).toThrow('simulationInterval must be positive')
+    })
+  })
+
   it('should call changeCallback', async () => {
     let resolver: (value?: unknown) => void
     const promise = new Promise((resolve) => { resolver = resolve })
 
     const universe = new Universe({
       bodies: [],
-      simulationInterval: 0,
+      simulationInterval: 1,
       changeCallback: () => { resolver() }
     })
 
@@ -37,7 +73,7 @@ describe('Universe', () => {
           velocity: new Vector(0, 0, 0)
         })
       ],
-      simulationInterval: 0,
+      simulationInterval: 1,
       changeCallback: () => { resolver() }
     })
 
diff --git a/src/Universe.ts b/src/Universe.ts
index 48461e2..5d33e61 100644
--- a/src/Universe.ts
+++ b/src/Universe.ts
@@ -11,20 +11,23 @@ export default class Universe {
   changeCallback: () => void
   private internalInterval: NodeJS.Timeout
 
+  /**
+   * @param universe definition of the universe
+   * @param universe.bodies orbital bodies in the simulation
+   * @param universe.gravity gravitational strength
+   * @param universe.collisions should bodies collide? (elastically)
+   * @param universe.deltaTime simulation time elapsed between iterations
+   * @param universe.deltaTimeSegments number of segments in which to split the simlation time delta for more precise calculations
+   * @param universe.simulationInterval computer time between iterations
+   * @param universe.changeCallback callback fired when simulation state changes
+   */
   constructor({
-    /** orbital bodies in the simulation */
     bodies,
-    /** gravitational strength */
     gravity,
-    /** should bodies collide? (elastically) */
     collisions,
-    /** simulation time elapsed between iterations */
     deltaTime,
-    /** number of segments in which to split the simlation time delta for more precise calculations */
     deltaTimeSegments,
-    /** computer time between iterations */
     simulationInterval,
-    /** callback fired when simulation state changes */
     changeCallback
   }: {
     bodies: Body[]
@@ -36,13 +39,21 @@ export default class Universe {
     changeCallback: () => void
   }) {
     this.bodies = bodies
-    this.deltaTime = deltaTime ?? 0.5
     this.gravity = gravity ?? 6.674e-11
     this.collisions = collisions ?? false
+    this.deltaTime = deltaTime ?? 0.5
     this.deltaTimeSegments = deltaTimeSegments ?? 1
     this.simulationInterval = simulationInterval ?? 10
     this.changeCallback = changeCallback
 
+    if (this.deltaTimeSegments % 1 || this.deltaTimeSegments < 1) {
+      throw new Error('deltaTimeSegments must be a positive integer')
+    }
+
+    if (this.simulationInterval <= 0) {
+      throw new Error('simulationInterval must be positive')
+    }
+
     this.start()
   }
 
@@ -60,7 +71,7 @@ export default class Universe {
     clearInterval(this.internalInterval)
   }
 
-  calculateGravitationalForces = () => {
+  private calculateGravitationalForces = () => {
     const bodyForces: Vector[][] = Array.from({ length: this.bodies.length }, () => [])
     this.bodies.forEach((body1, index1) => {
       this.bodies.slice(index1 + 1).forEach((body2, index2) => {
@@ -77,7 +88,7 @@ export default class Universe {
     })
   }
 
-  bounceCollisions = (body1: Body, index1: number) => {
+  private bounceCollisions = (body1: Body, index1: number) => {
     this.bodies.forEach((body2, index2) => {
       if (index1 !== index2) {
         const distanceBetweenBodies = body2.position.distance(body1.position)
@@ -104,7 +115,7 @@ export default class Universe {
     })
   }
 
-  moveBodiesThroughTime = () => {
+  private moveBodiesThroughTime = () => {
     this.calculateGravitationalForces()
     this.bodies.forEach((body, index) => {
       const deltaTimePerSegment = this.deltaTime / this.deltaTimeSegments
diff --git a/src/Vector.spec.ts b/src/Vector.spec.ts
index fcbc51a..d17665d 100644
--- a/src/Vector.spec.ts
+++ b/src/Vector.spec.ts
@@ -84,7 +84,7 @@ describe('Vector', () => {
     it('should scale vector to factor', () => {
       expect(new Vector(1, 2, 3).scaleTo(3))
         .toEqual(new Vector(expect.closeTo(0.8), expect.closeTo(1.6), expect.closeTo(2.41)))
-      expect(() => new Vector(1, -2, 3).scaleTo(-1)).toThrow(new Error('magnitude must be positive'))
+      expect(() => new Vector(1, -2, 3).scaleTo(-1)).toThrow('magnitude must be positive')
     })
   })
 })