CS0122 C# is inaccessible due to its protection level when accessing PlayerController.rb......

Hey guys, i'm trying to make a simple speed/velocity meter, I found out i could do so by accesing the rigidbody's velocity.magnitude. Only problem is, the rigidbody belongs to the player gameobject rather than the textUI object.

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class Speedmeter : MonoBehaviour
 {
     public float Speed;
     public GameObject CuboidPlayer;
     public Rigidbody rb;
 
 
     public Text text;
 
     void Awake()
     {
         text = GetComponent<Text>();
     }
 
     void Start()
     {
         GameObject.Find("CuboidPlayer");
         Speed  = PlayerController.rb.velocity.magnitude;
 
     }
 
     void Update()
     {
 
         text.text = " " + PlayerController.rb.velocity.magnitude;
     }
 }
 

It presents me with said error and an unworking project with this playercontroller script: ( unworking as in nothing responds anymore while there are no errors or whatsoever except the one mentioned ).

 using UnityEngine;
 using System.Collections;
 
 [System.Serializable]//This adds another class to the script menu in the inspector tab.
 public class Boundary
 {
     public float xMin, xMax, yMin, yMax, zMin, zMax;
 }
 
 
 public class PlayerController : MonoBehaviour
 
 {
     public GameObject attractedTo;// Set's gravity pull towards star
     public float strengthOfAttraction = 5.0f;
 
     //The purpose of this script is to simulate Newtonian phy
     public float maxThrust = 0.01f; //The maximum Thrust provided by the thruster(s) at full throttle
     public float rollWeight = 0.000000000005f; //This float and the next two only serve to adjust sensitivity
     public float pitchWeight = 0.000000000005f;//of the controls, and to allow calibration for more massive ships.
     public float yawWeight = 0.00000000005f;//Set these 3 floats to the mass of the rigidbody for sensitive controls
     public AudioClip ImpulseSound;
     public Boundary boundary;
     public float speed;
 
     private bool isMoving;
     bool isPlaying;
 
     Rigidbody rb;
    
     void Start()
     {
         rb = GetComponent<Rigidbody>();
         isMoving = (Input.GetKeyDown("z") || Input.GetKeyDown("x") || Input.GetKeyDown("left") || Input.GetKeyDown("right") || Input.GetKeyDown("up") || Input.GetKeyDown("down"));
 
         
 
     }
 
     void Update()
     {
         speed = rb.velocity.magnitude;
         //The code below describes when to play the sound to tell you are moving.
 
         if (isMoving)
         {
             GetComponent<AudioSource>().clip = ImpulseSound;
             GetComponent<AudioSource>().Play();
         }
 
         else
         {
             GetComponent<AudioSource>().clip = ImpulseSound;
             GetComponent<AudioSource>().Stop();
         }
             transform.position = new Vector3 //Here I clamp the cuboid's position within the Cubiverse sector's boundaries
             (
                 Mathf.Clamp(GetComponent<Rigidbody>().position.x, boundary.xMin, boundary.xMax),
                 Mathf.Clamp(GetComponent<Rigidbody>().position.y, boundary.yMin, boundary.yMax),
                 Mathf.Clamp(GetComponent<Rigidbody>().position.z, boundary.zMin, boundary.zMax)
                 );
     }
 
 
 
     void FixedUpdate()
     {
         Vector3 direction = attractedTo.transform.position - transform.position;//Sets values for gravity pull towards star
         GetComponent<Rigidbody>().AddForce(strengthOfAttraction * direction);
 
         float yaw = yawWeight * Input.GetAxis("Yaw") * Time.deltaTime;//Movement and rotation on 3 axis'
         float roll = rollWeight * Input.GetAxis("Roll") * Time.deltaTime;
         float pitch = pitchWeight * Input.GetAxis("Pitch") * Time.deltaTime;
         Vector3 Rotation = new Vector3(pitch, roll, yaw);
         rb.AddRelativeTorque(Rotation);
         float throttle = maxThrust * Input.GetAxis("Thrust");
         rb.AddRelativeForce(Vector3.forward * throttle);
         System.Console.WriteLine("input is " + yaw.ToString() + ", " + pitch.ToString() + ", " + roll.ToString());
 
         float strafeHor = maxThrust * Input.GetAxis("StrafeHorizontal");
         rb.AddRelativeForce(Vector3.left * strafeHor);
         float strafeVer = maxThrust * Input.GetAxis("StrafeVertical");
         rb.AddRelativeForce(Vector3.up * strafeVer);
         
             
 
         
     }
 }

after trying to make the public float speed in the PlayerController script static it all went wrong. I intentionally didn't try a static variable at first because that seemed, static rather than dynamic which i want for my ship. I want the number to go up or down a long the values presented by my cuboid's rigidbody.