Alex nodded slowly she admitted the class was interesting not more so then Arithmancy and Potions but still good. She made sure to write everything down.

Cadence took down notes as the Professor spoke, looking up at him every so often. This was all getting a bit deep, but she figured it would be important, right? When the Professor asked them if they were all following him, Cadence nodded her head. Now she was starting to understand. Raising her hand she asked, "So, a theory answers the question, 'Why?'"

Simon was following the professor very throughly."Yes , sir" he answered.

Kevin nodded and said "Yes sir i am following you"

Amy turned pink as he pointed at her and nodded slowly taking down the notes

Trixie smiled as the professor told her that it wasn't a bad start to his question. Well at least she had been brave enough to even answer it. She shrugged when he told her that he would quibble with her assumption definition. "Just my opinion sir" she smiled sweetly and returned back to her notes. She was on a roll today. She felt reasonably intelligent. She nodded as he started to explain the difference between hypothesis and theory's. SHe looked at the girl who asked the question about theory's giving answers and wanted to answer it herself but was unsure of whether the teacher was going to do that instead.

"Synthesis certainly plays into it," Risu confirmed, nodding, "but a scientific theory is more than just a synthesis of knowledge. It doesn't just answer the question, 'Why?' That's of course necessary for the theory to work, but it's not all of it. Every good scientific theory has a second part to it, a very important one. Testable predictions."

He raised the fifth finger of his right hand. "Testable predictions. To stay within our example, we have concluded, through our experiments, that ice melts faster in warmer climates. The first part of our theory says something like, 'Ice melts faster in warmer climates because...'," Risu paused, then shrugged. "Something. It has to do with temperature and the strength of chemical bonds, and an exact explanation would take us too far afield. But our theory fulfils the first important function, which is to explain the experiments we've run."

He got up with a heavy sigh and stood before the class. "Now, the second part - does our theory make testable predictions? It doesn't yet, but we can amend it to do so. Let's assume..." he smiled again, "that for the maths of our theory to work out, ice melts twice as fast for each degree the temperature rises. That's what our theory predicts. On the basis of that prediction, we can now go back and run a new series of experiments investigating that specific claim. If the experiments show that ice does indeed melt twice as fast when you raise the temperature by one degree, then our theory has been confirmed and we can be proud of ourselves. If the experiment shows that, for example, ice melts three times as fast, there is something wrong with our theory and we need to tweak it."

He paused again. "Questions?"

Keeley's head spun slightly. This was getting more complex. Bah. Buut... she was kinda catching on. Sort of. Not really. Well, they needed to know this for their exams or whatever, so she brushed aside a piece of scarlet hair and continued jotting down her notes like a good girl.

Amy scribled down the notes listening to the proffessor it was hard but in a way it was like physics, once you had a grasp on it, it becomes easier and easier

'That guy is a great teacher' Simon thought.Well he didn't have any questions.He just had it in.He wrote down the notes.

Ellie decided to actually raise her hand this time.

"Um, I'm kind of lost with this an astronomy... Doesn't astronomy have to do with the sky and stars... hence our telescopes?" Ellie asked this politely. Otherwise he could have taken it the wrong way. In reality, this was just more than her mind was willing to handle at this time...

Trixie nodded. She liked this lesson. She was able to apply her scientific knowledge throughout and was actually enjoying it. "So what we are saying is that a theory starts off with a prediction, something that we believe may be true. Our theory is either based upon this prediction or vice versa, provided we are given some evidence and support? she questioned. "And if this theory is tested, more than twice to make it completely fair and unbias, then we can call it a fact, or quite simply proved" she said making sure she had got this correct.

Kevin was a bit lost and raised his hand and said "Sir what does science have to do with astronomy"

"Professor this might be a stupid question, but how do you know when a Theory is incorrect?" Simon asked, he hoped the Professor wouldn't yell or throw him out of the class for not knowing.

Risu had to admit he was taken aback by that. His eyebrows climbed again. "Of course it does, and I admit that this is very complicated, but it's necessary when we consider the split of astronomy and astrology into two distinct branches of knowledge. I promise we will return to astronomy soon."

He grinned. "Does that sound fair? Good. Erm... where was I? Wait, another question first. Yes." He pointed at the student who had her hand raised.

"Not quite. Theories contain predictions, that is certainly true, but they are not based on predictions themselves. I can give you an example of this if you want, but first I need to address something else. Something very important - theories are not facts. Theories can never be facts. Facts are something completely different."

Risu ran a hand through his hair. "Unfortunately, this is again complicated because of our every-day language where fact is understood to be something 'better' than theory. In science, theories rank higher than facts. Facts just, well... exist. Theories string these facts together into an explanation as to why these facts exist. As in the example of gravity that was brought up earlier, it is a fact that we are experiencing gravity right now because we are not currently floating in the air. However, we need a scientific theory to explain why this is. Is this distinction clear to you?" He glanced at the rest of the class. "Is it clear to everyone? It requires very precise thinking, I agree, but it's of tremendous importance in science."

He looked around. More hands had been raised.

"Well, astronomy is one scientific discipline, of course. That's the purpose of this whole business, to show you how astronomy separated from astrology and became science."

"Good question. A theory is incorrect when it cannot describe reality," Risu said. "If, for example, experiments are run whose results the theory cannot predict, then the theory needs either needs to be reworked or abandoned completely. Or, to pick another way a theory can be shown to be incorrect, if observations pop up that contradict the theory."

Getting a bit of an understanding, Jimbo raised his hand.

"So...Astronomy is the SCIENCE of...astrology? Or like, star...s?"
This subject seemed to be very complicated. Jimbo just hoped he would be able to understand it a lot better when they got more into things.

Trixie frowned slightly. She hadn't actually said a theory was a fact. She had distingushed that bit earlier. "I know sir" she replied with a smile. "I was implying that once a theory had been to a certain extent, proven to be correct, well then could it be considered a fact?" she asked. "Could I use another example? Perhaps that will help me and others understand better?" she asked. "The theory of Evolution" she stated. "It has never been proven to be correct and in fact it probably won't ever be. Science is a complicated matter but even if we are able to provide evidence to this theory, which we can, would it still remain a theory forever? So therefore a theory is basically a scientific explaination and observation that even when provided with evidence, simply cannot be proved?" she asked.

Kevin nodded at the professors answer and said "Thank you sir for clearing that up for me"

"You are very welcome," Risu said. "More questions, I see?" He pointed.

Risu shook his head. "Astronomy is the science that studies the cosmos. The physical reality of the cosmos. Astrology is different." He shrugged, a little helplessly. "I have to admit I don't know too much about astrology - that's something your Divination teacher can tell you more about. But while astronomy concerns itself with, for example, what stars and planets are made of, astrology studies the supposed influence of these stars and planets on humans. Does that clear it up?"

"Well," Risu said carefully, "I still would say that you can never call a theory a fact. At least not when you are speaking scientifically. In science, theories and facts are completely different constructs. If you are speaking colloquially..." He shrugged. "I guess you can call well-tested theories facts, but I wouldn't recommend it. We speak of 'atomic theory', not 'atomic fact'. Using the two words interchangeably just leads to confusion. The kind of confusion, I suspect, we are both having problems with right now."

He paused. "Oh, and another thing that I think will help clear matters up. Theories can never be 'proven'. Not in the way that 1 + 1 = 2 can be proven. Theories are approximations, models of how the world works. For example... Gravity!" He smiled. "Until the 20th century, Newtonian gravity was the be-all-and-end-all of scientific theories for gravity. But there were small variations in the orbit of Mercury that Newton's theory couldn't account for. Along came Albert Einstein with special and general relativity, and his calculations solved the question of Mercury's orbit. His theory is, in that sense, a better theory than Newton's, but relativistic equations are very complex. Newton is still very useful for everyday applications. Theories can be disproved, of course, but there is no way anything can ever be proven one hundred percent in science. That's not how science works."

Risu took a deep breath. "As far as evolution goes... It's a complicated topic. Evolution is both a fact and a theory. The fact is, life on Earth changes." He paused. "That's the fact bit. The theory of evolution offers an explanation as to why life changes, namely because of random genetic mutation and subsequent natural selection. Now," Risu waved his hands, "there are libraries full of evidence that support this theory, but no matter how much evidence we accumulate, it won't turn the theory into a fact. That's what I said earlier - theories and facts are different matters entirely."

Trixie nodded and smiled. She liked this professor a lot. He knew a lot of the things that she wanted answered and he was full of knowledge that greatly interested her. "A theory is a peice of scientific information. It cannot be proved as such but evidence can be provided to perhaps support the theory proposed?" she asked hoping that would be a better definition. At the moment it seemed he and Trixie were the only two truely engaged in a conversation. She decided to suggest something that might help. "Then perhaps you can have some theory's that are essentially more correct then others would be. They would be more reliable in a scientific mind" she said smiling slightly.

Trixie nodded. She wasn't sure whether the professor was just talking to her or directing everything at the other students as well but she didn't mind. This conversation was full of knowledge. "So we can never be certain, even with magic, that a theory can be entirely correct however it is able to be incorrect as long as the evidence stacks up to support the fact that it is incorrect?" she said again.

Trixie nodded. "I thought the Darwin's theory of evolution would be a good example seeing as theory is within the title. It most certainly is a complicated matter, but I won't go into that because it has nothing to do with Astonomy" she giggled.

"That's a workable summary," Risu said with a nod. "A scientific theory cannot be proven, but, as its predictions are confirmed and evidence in its favour accumulates, we can become more and more confident in the theory until it is basically generally accepted. Almost everything in science we regard as self-evident today is a theory at its core. I mentioned atoms. Plate tectonics and the germ theory of disease would be other examples. You proposed evolution, which is similarly well-confirmed."

He sat down on his desk again. "Disproving scientific theories is a wholly different matter, of course. If enough evidence against a scientific theory emerges, then that theory has to re-examined. Sometimes, the theory can be amended or expanded to include the new observations. If that is not the case, it has to be abandoned in favour of a better theory that explains all observations." He smiled at at the girl, wondering if there was a debate club at Hogwarts that could make use of her talents.

Then he looked around at the class. "I can give you an example from astronomy if you want, but then we will have to move on. There are a few other things I want to talk to you about, but we are in danger of running out of time."

Sidney raises her hand. "Is that why sir Pluto is no longer classified as a planet? New evidence was discovered which forced the scientific community to re-evaluate their theories of planets."

Selena took notes quickly. They were moving at a pretty fast pace. She scratched out the notes into her notebook. She looked up and waited for more notes to take. Astronomy was the scientific study of stars, their paths and were used to determine different positions. This class seemed interesting when she first heard of it.

Alex wrote her notes carefully before waiting for the teacher to start again.

ASTRONOMY! Savannah loved astronamy, she CAN NOT wait for class to start.