My Planet Gravity system not working? C#

I have a system setup to try and detect when a player is in a specific planets gravity, but for some reason its not working. I will have my code below I have empty game objects with mesh colliders and rigidbodys on them to emulate the atmosphere and when they enter a certain one, they need to be pulled in. Here is the code i have: Thank you

using UnityEngine; using System.Collections;

[RequireComponent (typeof (Rigidbody))] public class GravityBody : MonoBehaviour {

 PlanetGravityEnter planet;
 
 void Awake () 
 {
     planet = GameObject.FindGameObjectWithTag("Planet").GetComponentInChildren<PlanetGravityEnter>();
     rigidbody.useGravity = false;
     rigidbody.constraints = RigidbodyConstraints.FreezeRotation;
 }
 
 void FixedUpdate () 
 {
     planet.Attract (transform);
 }

}

using UnityEngine; using System.Collections;

public class PlanetGravityEnter : MonoBehaviour {

 public float gravity = -10f;

 public void OnTriggerStay (Collider body)
 {
     Attract (transform);
 }

 public void Attract(Transform body)
 {
     Vector3 targetDir = (body.position - transform.position).normalized;
     Vector3 bodyUp = body.up;
     
     body.rotation = Quaternion.FromToRotation (bodyUp, targetDir) * body.rotation;
     body.rigidbody.AddForce (targetDir * gravity);
 }

}

using UnityEngine; using System.Collections;

public class FirstPersonController : MonoBehaviour {

 public float mouseSensitivityX = 250f;
 public float mouseSensitivityY = 250f;
 public float walkSpeed;
 public float runSpeed;
 public float jumpForce;
 public LayerMask groundedMask;

 Transform cameraT;
 float verticalLookRotation;

 Vector3 moveAmount;
 Vector3 smoothMoveVelocity;

 bool grounded;
 bool doubleJump = false;

 void Start () 
 {
     Screen.showCursor = false;
     cameraT = Camera.main.transform;
 }

 void Update () 
 {
     transform.Rotate (Vector3.up * Input.GetAxis ("Mouse X") * Time.deltaTime * mouseSensitivityX);
     verticalLookRotation += Input.GetAxis("Mouse Y") * Time.deltaTime * mouseSensitivityY;
     verticalLookRotation = Mathf.Clamp (verticalLookRotation, -80, 80);
     cameraT.localEulerAngles = Vector3.left * verticalLookRotation;

     Vector3 moveDir = new Vector3 (Input.GetAxisRaw ("Horizontal"), 0, Input.GetAxisRaw ("Vertical")).normalized;
     Vector3 targetMoveAmount = moveDir * walkSpeed;


     if (Input.GetKey(KeyCode.LeftShift) && grounded)
     {
         targetMoveAmount = moveDir * runSpeed;
     }

     moveAmount = Vector3.SmoothDamp (moveAmount, targetMoveAmount, ref smoothMoveVelocity, 0.15f);


     if (Input.GetButtonDown ("Jump") && (grounded || !doubleJump)){
         {
             rigidbody.AddForce(transform.up * jumpForce);

             if(!doubleJump && !grounded)
                 doubleJump = true;
         }
     }

     if (grounded)
         doubleJump = false;


     grounded = false;
     Ray ray = new Ray (transform.position, -transform.up);
     RaycastHit hit;

     if (Physics.Raycast (ray, out hit, 1 + 0.1f,  groundedMask)) 
     {
         grounded = true;
     }
 }

 void FixedUpdate()
 {
     rigidbody.MovePosition (rigidbody.position + transform.TransformDirection (moveAmount) * Time.fixedDeltaTime);
 }

}