My biggest fear is to lose my family, to lose those who I talk do daily and love. To lose those who always where there for me no matters what and when.
And then I will have to leave alone which is kind of terrifying, that your life are only depending on you, you decide what to do you choose your destiny.
You come back home and the only one who is there is yourself, you have noone to talk to, noone to ask questions and discuss with, you are by yourself.
I think that the biggest company would obviously be Elon Musk's company that is called "SpaceX" although I am not sure if it is the biggest one, Elon Musk is the richest man alive so the company has a lot of money behind and power, and that's kind of make it the biggest or at least one of the biggest companies.
Elon Musk have created a lot of amazing companies as of: Tesla - cars which can be droven by electricity, PayPal - a website to earn and use money at from all over the world, SpaceX - sending human beings to Mars in order to find a better planet to live on.