Gravity.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Gravity : MonoBehaviour
{
    public float mu = 1f;//Гравитационная постоянная G
    private void OnTriggerStay(Collider col)
    {
        //Квадрат расстояния между телами
        double sqrDistance = (transform.position - col.transform.position).sqrMagnitude;
        col.attachedRigidbody.AddForce(
            (transform.position - col.transform.position).normalized * (mu / sqrDistance),
            ForceMode.Force
            );
    }
}