I say that not in a million years could one person alone create a smartphone from scratch. My friend disagrees. Which one of us is right?

No, I don't believe it would be possible even in a million years, Take for example the hardware.

The main chip on the phone (The SoC) to build a relatively modern SoC you need to design, simulate and verify the chip. And to do that you need a more powerful computer with a specialized set of tools that you'll also need to make and to make these computers you'll need less powerful computers to develop them.

The last computers that could be designed by hand with out the a machine aided help where around the 80's.

Since then it took multiple millions of man years of work to mature the industry enough to develop a modern chip.

So she'd basically need to repeat all this work just to get to this chip.

To put things into perspective it is estimated to take around 6000 man years to build the Linux Kernel and that is just part of an operating system.

/r/AskScienceDiscussion Thread