It included a pictorial representation too, and I admit I was rather proud of it. I managed to unearth it and am putting it up here. Do read and comment. Sorry if the language feels a bit immature. It was written around 5-6 years ago!
Most of the HP fans are very fascinated by time-travel (henceforth referred to it as TT), but after reading a few articles by fans about Time-Travel, and some questions put up by HP fans about TT, I noticed that most of them have too many misconceptions about the whole thing.
Many of us, including myself, overlooked the concept of Time-Travel when we read PoA for the first time. But, after a lot of reflection over the whole thing, I noticed that it is not that easy as it seems on the first instance. But, at the same time, it is not difficult to understand if we give it a thought.
What is Time-Travel?
TT is the action of going back (or ahead, though it is not mentioned in the books) in time.
What is so special about it?
What makes TT special is the fact that after Time-Traveling, the actions of the Time Travelled person directly affects his past form. The other thing is that it results in two copies of the same person.
What makes it dangerous?
Well, TT is dangerous because your actions affect the past. In other words, what you do after time travelling will affect your past selves. Time travelling is extremely easy if you know you are going to TT in advance.
Also, keep in mind, the following question is meaningless – "What if this had happened instead of that? What if Harry had taken Buckbeak without letting MoM members see it?" The reason you can't ask such questions is because whatever happened in the book was because characters did things that led to it. It is difficult to digest this but it will ultimately sink in.
OK, I will elaborate everything with an example:
Let's imagine a person X. He is living an ordinary life. He has not yet time-traveled, but, plans to do it after an hour. The time now is 9:15 AM. He plans to go back 1 hour in time at 11 AM. At exactly 10 AM, one more X is added to the scenario. One X was already present and the other X has now come.
For one hour, two X's exist in the scenario. At exactly 11 AM, the original X time travels. Now we jump back to the past again. For the original X, it is PRESENT, but for the TT one, it is PAST. If they were to meet, the TT one would know what happened between 10 and 11 AM as he has already seen it, but the original X has not yet seen it. Actually, both are the same persons. A look at the diagram will make everything clear. You can see a timeline. The red line indicates the original X at 9:45 AM. Now, at 10 AM, the new X arrives. This is the blue line. At 11 AM, the original X (red) TTs and goes back to 10 AM whereas the new X (blue) continues the life. So, in the period of 10 AM to 11 AM, two X exist. I call this time-zone as the dual-existence zone.
Here, I come to a very very important part of TT. This is also a question that is asked by many.

Does Time-Travel mean that a TT person will be trapped in an infinite loop?
There it is… The most popular question. It was especially for this question that I drew the diagram of the timeline. It is clearly visible that there is only one loop. See, the red line goes on till 11 AM, and then the black line joins the red with the blue line that starts at 10 AM. Keep in mind that there is only one X. It is just that there are two copies of X between 10 AM and 11 AM. At 11 AM, the blue line continues forward. It DOESN'T loop. To understand it, take a rope and make a loop in it as shown in the figure. So, the red line goes on, turns around, becomes the blue line and then the blue goes on. So, there is no chance of being trapped in time forever like some Sci-Fi story or movie (not a very pleasant thought anyway!). There is only one loop. I think I couldn't explain it better.
I think I have answered most of the questions directly related to Time-Travel. I will now attempt to answer the two most burning topics about TT in GoF and OotP.
Is it possible that Fred and George TT'ed during the World Cup and thus told Bagman about the outcome about the match?
I will answer the technical portion of the thing (related to TT). I have imagined what might have happened.
After seeing the match Fred and George TT'ed and went back to the time a little before Bagman asking them for a bet. The original Fred and George new they will TT in the future so they went away to make the coast clear for their future selves. So, it was the TT'ed F and G who betted with Bagman. Later, the TT'ed ones either hid somewhere or stayed there. The original F and G either came back after ensuring that their future selves were away. I will quote my earlier lines - Time travelling is extremely easy if you know you are going to TT. See, how smoothly the plan worked.
P.S.: It is mentioned in GoF that Fred and George went away for a while during the cup.
Now, the most asked question:
Couldn't Harry TT and rescue Sirius?
The first mistake – Do not use Couldn't.
I will explain why you can't use it later.
I wished it were possible, but unfortunately, it is not.
If you refer to Mugglenet's Time Travel section, you would see that Harry couldn't have prevented Sirius's Death. Remember this:
You can prevent a thing from happening. You can't undo it once it has happened. (^Z won't work here!)
In PoA, Sirius was NEVER kissed by the Dementors. NEVER. Buckbeak was NEVER killed. NEVER. The reason Sirius was not kissed and Buckbeak didn't die was because Harry and Hermy-Own (OK, kidding! Harry and Herm-own-ninny, OK! OK! Harry and Hermione) time travelled and DIDN'T let it happen.
If Sirius had been kissed by the Dementors, nothing could have prevented it.
The main thing to understand if one wants to fathom the mystery of Time Travel is that Whatever is happening is happening because we did things that led to it.
This is the reason why I told you not to ask the WHAT IF THIS HAD HAPPENED INSTEAD OF THAT questions.
TT is possible every time. What makes the difference is that we don't do it. That is because we don't know when we need to TT. TT is running parallel to the normal time (this is to be understood). Harry and Hermione knew Sirius was going to be kissed. So they could prevent it from happening. If they had not TT'ed to save Sirius and Buckbeak, Beaky would have been dead and Sirius would have been kissed. Afterwards you couldn't have asked WHY DIDN'T HARRY AND HERMIONE TIME-TRAVEL TO SAVE SIRIUS AND BUCKBEAK? That is because, they DID TT and so Sirius and Beak are alive.
The reason why I forbade you to use couldn't is because nobody had stopped Harry from TT. He could have TT'ed if he wanted. But the fact again is that he didn't.
If Harry really had Time-Traveled to save his Godfather, Sirius would NEVER have died. The fact that Sirius has died shows that either Harry didn't TT or did but was unsuccessful in saving Sirius. Therefore, Harry couldn't have time-traveled. But, just to prove you that it was impossible for him to have time-traveled, I will change the story line a bit:
> Harry saw Sirius fighting with Bellatrix. Bellatrix launches the killing curse. Harry closes his eyes with fear. He hears footsteps and explosion. When he opens his eyes, he finds, to his surprise, that Sirius is not present in the room and Bellatrix has just gone to the other room.
> thinks Sirius died and fell through the veil. He runs towards the veil but Lupin comes from behind and says, "Harry, nothing to worry, Sirius is safe."
> Harry doesn't understand what's up but keeps quiet. After sometime, Lupin explains to him that Harry has to time-travel and save Sirius. Harry goes back in time (how he does it is no concern of ours). Now the story is from this Harry's point of view (the one who time-travelled). I will use "Potter" for the original Harry and "Harry" for the time-travelled one.
> Harry runs and hides himself. He sees Sirius and Bellatrix fighting and sees Bellatrix launching the curse and Potter closing his eyes. Harry runs and pulls Sirius out of harm's way. Bellatrix goes to the other room and Potter opens his eyes to see nobody but him.
Thus, the time-travelled Harry rescued Sirius.
> Potter goes to Lupin who tell Potter that he has to TT. Potter TT's and goes back and hides, and when the time comes, jumps and rescues Sirius.
What I have presented is a very crude description. I want to impress upon the fact that Sirius has DIED and Harry cannot undo his death by TT'ing. He could have prevented it. So, Sirius fans should not be hopeful.




















