How long would it take to terraform Mars?
I'm going to follow the data provided in Robert Zubrin's very interesting book 'The Case For Mars'.Use a giant space mirror 120km across to warm the southern polar cap by 4K. After a few decades, it will completely sublimate, adding about 50-100mbar to the (originally 8mbar) atmosphere. This will warm the planet enough to partially outgas the regolith, but likely not completely. Pumping of around 1000tonnes of perfluoromethane, or CF4, into the atmosphere every day would guarantee enough of a green house effect to outgas the regolith.A 120 square km mirror would weigh 57600 tonnes assuming a space blanket density of 4g/sqm. This is about the same as a large ocean liner, but somewhat simpler. Automated production from an asteroid would be the energetically simplest way to go, though you could also railgun self deploying smaller mirrors from the Martian surface.The planet begins to warm, and a heat pulse travels downward, melting water. This process can be accelerated in a few polar regions with more space mirrors, creating a few wet lakes.Once the atmosphere is up to around 400mbar, the surface is warm enough in some places to seed with ammonia and methane producing bacteria, which help to thicken the atmosphere.Throughout this process, which will take 2-7 decades, convenient comets can be burned up in the atmosphere to increase the availability of water vapor.At this point, the atmosphere is warmish, wet, and plenty of pressure. It's still highly poisonous. Think Pandora. Breathing masks are necessary.Humans can't breath on the surface until there is at least 150mbar of oxygen. Build some factories to produce enough for plants, and they can make the rest. In the meantime, release as much nitrogen as you can find. Unless we have super efficient plants, however, this will take at least a thousand years. Another possibility is solar powered oxygen generators.As CO2 is stripped, more CFCs and other greenhouse gasses need to be produced to compensate.In summary, cold but not vacuum is pretty quick, warm, then warm and wet is still less than a century, but non poisonous is hundreds or thousands of years.
Should I become a doctor or become a lawyer? I’m 16. What's the average salary? How many years of studying does it take? How hard is it get into a program at a respectable university? How hard is it to get a job, and what’s life like, outside work?
Doctors are folk heroes who literally save lives. Lawyers are the butt of endless jokes and derision. Shakespeare did not counsel that we should "first, kill all the doctors". And consider this: doctors are the only people who can actually trump police and tell them "No, you are not going to do that". Try doing that as a lawyer. Doctors are famously bad at financial investments. But consider how it is that they attained this distinction: they make obscene amounts of money that has to be invested. Lawyers, on the other hand ... well, how many cases have you heard of a doctor stealing his patient's money? I am a lawyer and I am proud to be a defender of the Constitution. I love my work and I love every day that I face off against a government intent on trying to intervene in every aspect of our lives. I get tremendous satisfaction from being a lawyer. But I have to admit that doctors hold a more prestigious place in our society, so if that's important to you, there you go. Finally, consider what it means to be on call 24 hours a day on duty as a physician; what it means to have a day full of 10 minute appointments poking at flabby bodies and endless complaints of pain. Consider what life is like in a hospital residency/internship, wandering the halls at night attending to people with every manner of disease and sickness. Consider what it will mean when you are on a plane flight and the flight attendants sound the alarm: "is anyone a doctor"? Yes, you are a folk hero, but you earn your status every minute of every day. And then take a look at the lawyers in their snappy 3-piece suits walking down marble hallways into open oak chambers, spending their day sparring over intellectual issues that can change the lives of many with one stroke of a pen. Consider what it means to be a champion of freedom, of liberty, and to uphold the most noble aspirations of this great social experiment we call the United States of America. For me, the choice was easy. Good luck with yours.