When do stock price goes up?

When companies release products that would likely to make a huge profit their stock price goes up? Products like new PlayStation, Iphone, movies, video games. Not only manufacture, retail store's stock will go up also. Highly expected products have a chance they will fail to make good sales. But the chance is low.

How about war? When a big war starts, arms industry's stock price goes up?

Companies like Google, Facebook, electricity, gas, they are difficult to know when their stock price goes up, and they don't sell very different new products. Isn't it difficult to know their changes in their stock price?

Stock price goes down when a company is not making a profit well?

Alot of reasons, their are entire courses on this. It won't be consolidated into 1 sentence here.

You have asked a question that students at Harvard Business School would spend 2 years discussing and debating.

Like an antique lamp in an auction, the more people willing to pay an increasingly larger amount for the item, the higher price it will eventually command.