为什么下面的代码对不同的执行给出不同的输出?

class Program
{
    public static void ThreadMainMethod()
    {
        for(int i=0;i<10;i++)
        {
            Console.WriteLine("Thread Proc{0}",i);
            Thread.Sleep(0);
        }
    }
    static void Main(string[] args)
    {
        Thread t = new Thread(new ThreadStart(ThreadMainMethod));
        t.Start();
        for(int i=0;i<4;i++)
        {
            Console.WriteLine("From Main Thread");
            Thread.Sleep(0);
        }
        t.Join();
    }