How to fund several manned missions to Mars

I watched this talk given by Exeter College student, Beth Barnes, a couple of months ago and it’s so good it needs to be shared. It’s only 6 minutes but very powerful and thought-provoking. It has nothing really to do with missions to Mars although she does mention this in her talk. It’s about a movement called effective altruism and how we all have the power to change the world. The spending calculations start at 2:45mins so if you only have time to watch a bit, watch that bit.