Make a global shift from dumping trash in landfills to using recycling and compost 100% of the time. Create new polymers and plastics so that nothing has to be trashed.
Make a global shift from fossil fuels to nuclear power and renewable energy. Convert all non-renewable sources to uranium-based nuclear power and incorporate solar, wind, and tidal power wherever possible. Eventually, start a transition to thorium-based nuclear power and cold fusion. Use organic radical batteries to store energy to allow the world to become 100% renewable-based.
Make all meat and animal product producing farms adhere to rules that eliminate bacteria and infectious disease transmission. Convert all naturally created meat to lab-based animal products through biopsies.
Eliminate extreme poverty in the world, which will cost $175 billion a year to provide healthcare, education, food, water, internet, etc. to all people. Use microbial and hydrogen fuel cells to make our cars cleaner and the water potable.
Destroy all forms of terrorism and violent crime.
What major should I choose, and how should I go about my career path? Should I consider graduate school in research or even law? I am interested in becoming an astronaut eventually, but I need a strong career first to be considered? Should I go into politics or scientific research?
Hopefully, someone can help me become more clear as to how I should go about my life.
best route to astronaut historically has been Naval Aviator - but long shot for anyone.
Still truth to making a difference in your sphere of influence to make the world a better place. Lot’s of majors that lead to careers that do that but they typically don’t pay well. Based on your list, environmental engineering.
Other possibilities:
Political science.
International relations.
Environmental engineering.
Sociology.
Anthropology or ethnic studies.
Agriculture.
Economics.
Law or criminal justice.
Or, since there is no one major that teaches all of the things you want to accomplish, perhaps you could major in creative writing or film and learn to use the media to inspire others to join the causes you care about.
You can major in virtually anything to ‘change the world’ or ‘make the world a better place’. There are LOTS of things the world needs to make it better - from scientists to engineers to writers to ethicists and all kinds of other things. For example:
Environmental science, industrial engineering, materials science, business/health policy and management, industrial design, epidemiology/biomedical science/biostatistics (to make sure that the new plastics and polymers aren't harmful to human beings and animals), urban planning (where are the new recycling and compost centers going to go?), marketing/sociology/psychology (how are we going to get people to adhere to the new recycling and compost requirements?)
Nuclear engineering; physics and/or chemistry; atmospheric science/earth science/geology. But also potentially political science and economics (to study economic and political impact of these shifts and how to convince world powers to make them as well as fund it) and epidemiology or biostatistics (what effects may this have on people's health?) or even sociology/anthropology/psychology (what's the effect on the world and it's people to make these transitions?)
Agricultural science, agricultural economics, and other kinds of food science majors like dairy science; environmental science again; chemistry, biology, biomedical science; but again, economics and political science and epidemiology and biostatistics (because there are bound to be some health effects that need to be studied on using lab-based animal products). And psychology/marketing/business and sociology to understand the effects and how to persuade people to eat it (because people are going to be crowing soylent green! People already don't want to eat GMOs.) Even philosophy, like health/medical ethics of feeding people artificially made foods.
OMG, anything. That's going to take a variety of different kinds of jobs to work out, including things you may not think about like accounting and finance, software development, civil engineering (for infrastructure and transportation development), urban planning/design, community health educators...so you can major in anything. Again, even something like history works here (what worked in the past, and what didn't? What were the problems that happened last time we tried to do this that we can avoid) and philosophy (what are the ethical issues with redistribution of wealth and resources? Because some of that has to happen in order for this to work).
Similarly...anything. Even something like philosophy (there are likely ethical decisions to be made...what counts as terrorism? What should we do to these terrorists and violent criminals?)
So think about your interests and the kinds of tasks you want to do. Do you want to be working on the scientific discoveries that will be necessary to pull these things off? Do you want to be applying the science to create tools and inventions that will help? Do you want to understand how these endeavors will affect people, their health, the environment, geopolitical status? Do you want to help figure out how to accumulate and manage the finances and manpower necessary to get these things done? Do you want to go into law/political science/economics to help pass the national and global policies necessary to get these things done? And so on and so forth…there are so many different pieces that is less about what you want to get accomplished and more about which piece of the puzzle you want to be responsible for.
Also…just spitballing here…but I’m going to guess that eliminating extreme poverty is going to cost more than $175 billion a year.