Time is an abstract concept.
Seconds, minutes, hours, were developed by humanity to rationalize the movement from one moment to the next. All species on all planets have their own way of understanding time, their own designations for the increments that mark the passing of sunrise to sunset, from the beginning of life times to their ending.
What is not abstract is the existence of what many refer to as "the time stream." While time itself is open to interpretation, there is the undeniable fact that an action occurs, causing a reaction, and it becomes a fact, also called a fixed point.
All fixed points are not the same, however. Some are more "fixed" than others, it simply depends on how much the time stream is changed from the action and reaction.
Say you spill a glass of milk this morning, and you're so upset about it you've completely ignored the advice you've heard all your life about the proper emotional response to milk spilling. You get into your time machine, fly through the vortex of time, and stop yourself from spilling the milk. You succeed. No harm done. The fixed point has been altered with minimal or even no damage done to the time stream. The action was merely a small pebble thrown in a massive lake, creating just a small ripple. Of course, you could also inadvertently make a thunderous crash when your time machine lands, the same thunderous crash that startled you a few moments earlier and caused you to spill your milk in the first place. This is what quantum physicists call a "grandfather paradox," and beginning to explain it would certainly create a headache for everyone involved.
The types of fixed points that are impossible to change are the types that would cause such a monumental change to what has been true for centuries, it would be impossible for reality to rewrite itself without causing a near total collapse. For example, if you're a centuries old time traveler who has discovered that your future wife is supposed to murder you in Nevada, you can easily avoid altering time by faking your own death after having miniaturized yourself in a robot body that can act as your corpse in a somewhat silly and convoluted, but also stunningly brilliant plan.
But I digress...
Time is an abstract concept. Fixed points cannot be altered or changed. And even if you did try, the universe has many ways of restoring and repairing itself. Whether it is horrible paradox devouring monsters, or a brave woman who was inspired by a hero, time will be restored by someone. Unless you can find a loophole...
The Great Intelligence floated along the ripples of time. Free of a physical form, the creature of personified darkness watched all of the Doctor's life unfold before him.
The giiiiiiiiiirl...she is everywhere...how do I destrooooooy the Doctor...undo hissssss history...if she is everywhereeeeeee...yeeeesssss...that is hoooooooow. A newwww tactic must beeeee employed.
The year was 1998. Rose Tyler was 12-years old and she was running away from home.
Thick rain drops fell with a pitter-patter tempo on the London streets. Rose sat alone at a bus stop wrapped in a pink poncho. The rain hid the tears on her cheeks.
She didn't mean to get so mad at her mom. She didn't know why her mom always had to yell so loudly at her.
Haaaaate. She haaaaaaates you.
A voice whispered in Rose Tyler's ear. Rose looked around, but she was still alone.
It made her so mad when Garth picked on Billy Tanner. She finally stood up to him today. She pushed him off the swing and said that if he ever bugged Billy again she'd throw all the rocks she could find at his head. Garth said she had beaver teeth and was the dumbest girl in school. Rose threw a rock at his head.
Stupiiiiiiiiiid giiiiiiiirl. He's riiiiiiiiight.
Rose clapped her hands over her ears. She hated that voice. She wished it would go away, but it clung to her. It refused to let go. In order to get away, she ran down the street, but the whispers followed her.
Stttuuuppppiiiidddd giiiiiiiirl. You wooooon't escappppppeeeeee.
With cheeks wet with tears, she stopped to catch her breath.
"Hey, you here for a movie?"
Rose wiped the tears from her eyes and saw the cinema standing before her. In between the two doors was a booth with a glass window. A young woman with an overpowering smile and brunette hair gave Rose a wave.
"We're giving out free tickets today," the woman said, "but only to people who are smiling!"
The obvious attempt to make Rose change her attitude only soured her mood. She wasn't a kid any longer. It would take far more than a stupid movie ticket to make her feel better.
"Ah, did I say only people who are smiling?" the woman said "I meant only people who are mad and upset about something. They're the ones who get free tickets!"
The woman printed out a small red ticket and slide it through he opening in the booth window.
"You ever seen that one?" the woman pointed to a movie poster with a massive grey robot carrying a blonde haired woman in its arms. The title read The Day the Earth Stood Still
"It's a classic," the woman explained, "one of my absolute favorites."
Rose took the ticket, still not completely convinced, but willing to let the weird woman change her mind. She giggled at the woman's outfit: a bright blue shirt under a white vest with St. John's Cinema scrawled across the right side in white embroidered letters.
"You have to wear that for your job, right?" Rose asked.
"Yeah, it's kinda silly, isn't it?" the woman said.
"Especially the bow tie," Rose said.
The woman's hand reached for the bowtie in a protective way.
"Hey now," the woman said, "bowties are..."
"Dumb!" Rose said with a laugh, and the woman couldn't help but join her.
The movie was better than Rose ever expected. The final words that the strange alien man spoke still bounced around in her head: "The Universe grows smaller every day, and the threat of aggression by any group, anywhere, can no longer be tolerated..."
She looked up at the stars that were slowly beginning to show themselves in the night sky.
"How'd you like it?" the woman was no longer trapped behind the glass of the ticket booth. A red coat covered her work clothes and kept her warm from the damp air.
"It was brilliant," Rose said, "thank you for the ticket."
The odd pair began to walk along the London streets, hoping to avoid any more rain.
"Are you alright?" the woman asked.
"I think so," Rose said, "I...don't really want to go home though?"
"Trouble with mum, or dad?" the woman asked.
"How did you-?"
"I was your age once too. There's only one thing that can get someone your age that upset."
"She just gets so mad sometimes. I don't understand why."
"Something I learned when I was your age is that your mum and dad won't always be there when you want them to be. Sure, they may be standing around you, but once you reach a certain age, it's almost like...you need to take care of them and help them more than they need to take care of you. They start to realize their lives are almost over. They're watching you grow-up quicker than they ever expected. And sometimes they get mad. But, as long as they aren't hurting you in a way that truly isn't right, you can't hold it against them. You're an adult now. What they say or do...it's not as important as it once was."
Rose thought about this for awhile. She didn't know if she was ready to try and be someone so...grown-up.
"That doesn't seem fair. I don't know how to be an adult yet."
"It's not fair," the woman said, she crouched down so she was right at Rose's eye level "but it will still happen. The important thing to remember is that you aren't what your mum says you are, or your dad says, or your school says, or what other kids say. You are who you are and you are the choices you make. Nothing else defines you. It won't be easy. It never is. But running away from a problem never solves it. It just leaves a big mess for someone else to have to clean up."
The woman walked Rose all the way back to her flat.
"I'm sorry I called your bowtie dumb," Rose said.
"S'alright, it didn't bother me at all," the woman rested a hand on Rose's shoulder, "now, I meant what I said. If your mum ever does anything truly terrible to you, I want you to come right back to that theater. It's not running away if it's to protect yourself."
"I will, but I know my mum would never do something like that."
"You're very lucky then," the woman gave Rose one last smile and waved goodbye.
Rose climbed the seemingly endless steps to her apartment. Her mother was sitting on the couch in the upright position. The television was on, and the phone was clutched tightly in her hands. She was still in her work clothes. Rose quitely took off her mother's sneakers, and gently placed her head on a pair of large pillows. She leaned in and gave her mother a kiss.
"Love you, Rose..." she heard her mother say in voice trapped in the realm of dreams.
Rose climbed into her own bed and realized, for the first time in weeks, the horrible voice was finally silent.
Rose never saw the woman again. The loophole had closed. Time ticked onward.