Q:

What's the difference between "travel through time", "travel in time"?

What's the difference between "travel through time", "travel in time"? I am wondering if both mean the same thing or can be used to mean the same thing as "time travel".
For example:

He traveled through time to see his dead brother.
He traveled in time to see his dead brother.

A:

They’re both essentially the same meaning. However, I would go with “travel through time,” as it indicates more of a movement and is slightly more accurate. Note that with “he traveled in time to see his dead brother,” in time also has a nuance of before it was too late. 
In other words, it could then be said that “he traveled in time to see his dead brother (before they buried him),” or something of the sort. I hope this makes sense. 

