Why do educated Chinese immigrants born before 1970 look down on the legal profession?

I'd go further than Justin Liu and suggest that it isn't a thing. I've known many Chinese immigrants (to the U.S.) and never encountered disdain for law as a profession. Granted, it might not be quite as esteemed as engineering, the natural sciences, medicine or academic disciplines like history among people of the age cohort specified in the question. But even your hardcore "Tiger Mother" isn't going to freak out to hear that her son or daughter is taking the LSAT and applying to law schools the way they might, say, if that child was planning on applying to creative writing programs.
I didn't know that this was a thing, but maybe it is based on the same occupational hierarchy from ancient China as in Why do educated Chinese immigrants born before 1970 look down on the business profession?
Would the US actively defend a non-ally in the event of an isolated alien attack/invasion?

Seems plausible, some (non-aquatic) aliens want an enclave on Earth with the least bother.  Assuming they are not snow-birds enough to pick Antarctica, they might well pick central Africa.  Relatively unpopulated, good if you want fresh water and/or lush vegetation. 

If Earth is 4.5 billion years old, could we look back and see Earth as it was say 2.9 billion years ago?

Umm, sure this is possible, if you could get 2.9 billion light-years from Earth, and have an extremely powerful telescope built for when you get there. Of course, getting 2.9 billion light-years from Earth would kinda take you, at best, 2.9 billion years.So, unless you find some kind of

How do self driving cars think?

Think is a human concept very much driven by emotion . Automatons have a mission andsystems which assist in achieving the mission and other systems which provide self and environment safety.Self driving cars have no emotional context about what they do , they just do it !