title: Is it possible to time synchronize two topics in ROS of same message type?
body: <p>I try to map robot gripper position to the resistance exerted by the object held by the gripper. I subscribed the gripper position from one topic and resistance value from another topic, since I want to ensure that the gripper position corresponds to the exact resistance value at that position. Given that both are float messages, how can I synchronize them?</p>
  
  <pre><code>self.sub1 = rospy.Subscriber("resistance", Float64, self.ard_callback)
  self.sub2 = rospy.Subscriber("gripperpos", Float64, self.grip_callback)
  </code></pre>