void gazebo_stats_callback(ConstWorldStatisticsPtr &msg) {
Time t(msg->sim_time().sec(), msg->sim_time().nsec());
Time rt(msg->real_time().sec(), msg->real_time().nsec());
// Time rt = Time::realNow();
// if(gazebo_registered) {
Time::setTime(t, t.seconds() / rt.seconds());
// }
// gazebo_last_time =
}
void cb2(ConstWorldStatisticsPtr &_msg)
{
std_msgs::Float64 realtime, simtime,nanosec;
realtime.data=_msg->real_time().sec();
//nanosec.data=_msg->real_time().nsec();
simtime.data=_msg->sim_time().sec();
pub2.publish(realtime);
pub3.publish(simtime);
//pub4.publish(nanosec);
}