You don't have to be bad at all to be sent down to hell. If you're young and don't know any better than I don't think you will. Also, think of it this way. You get mad at say your wife or whatever. You get in one little fight that lasts 30 seconds or whatever and you pick up some random object and she dies. That whole process can take up like a minute. The consequenses would possibly be a sentence in prison for life.
Now think of it like this, the choices you make in life, if you don't accept Jesus (not trying to get all Bible...e lol can't spell) which takes like 30 seonds to do then you will go to hell for eternity. I'll come back to this thread when I can remember what I was going to say. I had a really good speach that someone told me at youth group. Also, my friend said there is 7 regions of hell differing in pain. I haven't looked this up so I don't know for sure. So basically if you are a murderer, adulterer, abuser... idk then you will go up to one of the higher levels. But still, eternity is a long time. Think of it this way, if you were in there for a thousand years and that's all you could be like oh only 999 years and 364 days to go I can do that easy. Then the time goes up and you're like, "Oh I can do that!". But, unfortunately there is no end. Your suffering in hell will be for eternity meaning no end. You will be in there forever and there is nothing you can do. You will also have all those thoughts of, "why didn't I listen to my friend that one time" and all those things.
Also, a bunch of people don't believe in God anymore (prophesies!!!!) But you know how you learn about things in school in history class way back in the day? All that stuff is real right? Well, basically the Bible is sort of like a history book in a way telling us what happened in that time. What makes it any different than the American History or Geography books that we use in school now days? Now some of you are probably going to debate me which I will not accept because I'm going to abandon this thread once I'm done.
Now for your question of physical proof. Go out and either find an illegal ebook or the real book of "90 minutes in heaven". The guy died in a car crash when he was hit head on by a semi at a combined speed of I think 120mph and the car was so messed up you couldn't even tell it's a car. The guy inside was coming back from a church convention or something I think and he died instantly on the site. Another guy in his car coming back from the same convention saw the car crash and went over to see the guy and he wanted to start praying. The guy started praying to a complete dead guy and started singing hymns about God. Meanwhile the other guy is in heaven and he sees all his family and stuff. I'm not going to say the rest of the heaven part because I need to move on. The guy that was praying for the dead guy in the car was still singing and guess what, the dead guy comes back to life amazingly. Now, the paramedics checked the guy several times to make sure he was completely dead. They checked several times and the guy was absolutely dead and no way to come back. The guy comes back alive and starts singing the hymns with the guy praying for him. The guy praying and singing for the dead guy (now alive) prayed that he has no internal injuries or brain damage. Guess what happened? No brain damage or internal injuries. But he did have a huge chunk taken out of his legs and a 5 year recovery process but yeah. The paramedics said there was absolutely no way he could come back and after aobut 10 minutes dead you have serious brain damage. This guy was dead for 90 minutes. Also, the doctors said there is absolutely no medical reason why he came back to life. They could not find any way how it is even nearly or at all possible to save him.