CT How did Vader knew that Luke is his son?

In your dreams maybe?

Expanded Universe already answered that. Vader did a research and traveled around the galaxy to find the identity of this pilot. By the time of TESB he knew very well who this rebell pilot was. Because of that he captured Lukes Friends and set a trap for him.

 

Ok i didn't know that the "how is that possible" is a recent addition . . .
That just confuses things further lol

The movies work a lot better if you ignore most of that, especially Splinter of the Mind's Eye

In my opinion

Yes he knew his name and what he was doing etc but it's never really made clear in the film that he knew that Luke Skywalker was his son until the Emperor told him, in fact the opposite seems to be the case

 

I'm mostly OK with it, since Vader knows at least that his name is Skywalker before the Emperor mentions who he's related to.

 

In Splinter in The Mind's eye, Vader knows that Luke is his son long before his hologram conversation with the Emperor.

With the help of his spies, Vader tracked down a rebel pilot, and the rebel told Vader that the last name of the pilot that destroyed the Death Star was Skywalker.

At this point, Vader knew that Luke was his son.

 

Nope- The Rise & Fall of Darth Vader mentions that. And makes it clear that knowing that the pilot's name is Skywalker, is not enough to have Vader know for certain that the pilot is his son- he needs to know their precise relationship, and sharing the same name is not enough in itself.

This bit of the book is after he's interrogated the pilot, but before his confrontation with Luke on Mimban:

Even while inspecting his nearly completed flagship, the Super Star Destroyer Executor, at the Starship Yards of Fondor, Vader could not get Luke Skywalker out of his mind. He silently chewed on the name, and considered the fact that the boy had been born three years after the death of Shmi Skywalker. To the best of his knowledge, Anakin Skywalker had been his mother's only living blood relative.

Could there have been other Skywalkers from Tatooine? Vader allowed the possibility. After all, it wasn't an entirely uncommon name in the galaxy.

But Anakin and Padme Amidala had been expecting a baby nineteen years ago.

Nineteen standard years.

It's not possible, Vader thought. I killed Padme. The baby died with her.

Not for the first time, he wondered if the Emperor had told him the whole truth about Padme's death. But I remember choking her ... seeing her collapse on Mustafar. I was so angry with her. And yet ...

Luke Skywalker exists.

Vader refused to believe the notorious Rebel's surname was merely a bizarre coincidence. If he had possessed any other name, Vader would not have hesitated to report what he had learned to the Emperor. But for purely selfish reasons, Vader kept the young Rebel's name to himself. To him, Luke Skywalker was more than a mystery to be solved.

He is ... an opportunity. As strong with the Force as he may be, he is an opportunity ... an opportunity for even greater power.

But who is he? Who were his parents? Could he have been Obi-Wan's son? But then why was he named Skywalker and raised by the Lars family? Or was he merely trained by Obi-Wan?

Because Obi-Wan Kenobi, Shmi Skywalker, Owen and Beru Lars, and Padme Amidala were dead, there was only one way Vader could discover the truth. He would have to ask Luke Skywalker himself. All he had to do was find him.

 

I meant Vader was at least suspicious that Luke might be his son at that point, but not he wasn't 100% sure.

 

Yes. He still managed to be surprised by the Emperor's statement.

Apparently when he told Luke "Search your feelings, you know it to be true" he was recalling the Emperor's use of similar words, and figured if it works with him, it'll work with Luke.

 

It's implied that the Emperor found out about it through the Force.

He said, "I have no doubt this boy is the offspring of Anakin Skywalker", and in The Rise and Fall of Darth Vader, Vader was merely suspicious.

Vader got to his conclusion that Luke could possibly be his son the same way a cop solves a crime in a detective case-by putting the facts together. But the Emperor confirmed it through the Force, the same reason that Luke knew Vader wasn't lying.

 

Seems reasonable. The Emperor could have somehow had a spy obtain Luke's DNA, and compared it to Vader's (preserved after some of his medical operations)- but that seems a bit too convoluted- The Force probably makes more sense in this context.

 

Yeah. Luke didn't ask Vader for a DNA test, he just knew the truth with the Force. "Search your feelings, you know it to be true".

Star Wars is science fantasy, not science fiction; not everything has to be explained to us through science.

 

When Splinter of the Mind's Eye was written, Vader wasn't Luke's father. He was the guy who killed Luke's father.

 

My assumptions are usually correct..

If Skywalker isn't an uncommon name, why haven't we seen any others even in the eu? We have seen at least three unrelated people with the name of Antilles, but no other Skywalkers. It would make since that there are others since we never knew where Shmi was really from, but a book saying that, doesn't make much difference if we don't see the evidence of other Skywalkers. It just sounds like Vader being in denial so Anakin doesn't resurface.

 

If Goerge Lucas says Skywalker is a common name . . . it is a common name

first rule of Star Wars

 

No **** bud. Skywalkers who are strong in the force are more rare than normal Skywalkers, so Vader is a fool or in denial for not knowing that the kid hanging with Kenobi isn't his son .

 

I'm guessing a mixture of "denial" and "unwilling to make conclusions without proof" play a part.

 

No spamming, please-Darth Boba

 

Who needs absolute proof when you have the force to give one insight into the truth. Anyways might as well agree to disagree on this topic, because my mind is made up.

 

The fact that Vader shared the same last name? Isn't that quiet obvious.

 

You got this one man! One more though, Darth and The Emperor mentioned a tremor in the force. They felt Luke. Why not Leia? Simple, Luke had meet Obi-Wan and began his training. Leia had no contact with jedi of any kind till just seeing Obi-Wan. She didn't start training. So there, pretty simple when you think about it.