C++ cin a float before a string 不起作用，但 cin a string before 起作用为什么？

如何解决C++ cin a float before a string 不起作用，但 cin a string before 起作用为什么？

不起作用：

#include <iostream>
#include <string>
using namespace std;

int main() {
  
  string planet;
  double weight;

  cout << "What is your earth weight?\n";
  cin >> weight;
  cout << "What planet do you want to fight on? ";
  getline (cin,planet);
  cout << "your planet is " << planet << "\n";
}

作品：

#include <iostream>
#include <string>
using namespace std;

int main() {
  
  string planet;
  double weight;

  cout << "What planet do you want to fight on? ";
  getline (cin,planet);
  cout << "your planet is " << planet << "\n";
  cout << "What is your earth weight?\n";
  cin >> weight;
}

以第一种方式运行它会在打印“你想在哪个星球上战斗？”后终止程序。我的问题是：为什么它是第二种方式而不是第一种方式？和c++的编译方式有关系吗？