Weight and mass are different.
And all of this talk about interstellar space travel completely neglects space travel in our own solar system! Trips to Mars and the moons of Jupiter and Saturn; trips to exoplanets to mine them for minerals; trips to inner planets even, provided an adequate heat and radiation shield could be developed; they’re all possible with current technologies, and the farther we go, the greater the likelihood that terrestrial development of better technologies increases.
Think about a permanent settlement on the moon to mine 3He. Thousands of jobs would be created in engineering and construction alone. Math and science studies would become obligatory in every school in every country, and generations of kids would grow up to develop technologies that none of could ever imagine.
Think about exploration of Mars. It’s possible we could terraform in very small areas. The use of methanogenes has widely shown to be possible in the Martian atmosphere and could create oxygen in a biosphere. The Martian regolith is so rich in iron that we could develop new technologies and processes to create steel right there on the planet. And none of us can conceive what’s under the surface. There could be enormous veins of copper, iron, coal, and even gold.
Commercial exploration and development of space NEEDS to happen and it needs to happen now. As soon as a commercial venture discovers something of immeasurable value to terrestrial humans, the money will flow like a river and space will colonize.
Yes, it’s all conjecture at this point, but I feel it in my soul that I will see man on the moon and Mars before I’m gone.
We don’t even need to put colonies on Mars or the Moon: stick ‘em in orbit, we’ve got tons of room up there. O’Neill cylinders placed at LaGrange points would give us all the elbow room we need.