Interstellar travel

Interstellar travel is still possible, but as far as we know, the best option is to think fairly local for now. The nearest star system to us
is Alpha Centauri. In 2016, scientists discovered an Earth-size planet in the habitable zone of one of Alpha Centauri’s stars, a red
dwarf called Proxima Centauri. (There’s debate about whether Proxima Centauri’s stellar activity has too much radiation for life to
exist on its planet, but the jury is still out on that.)
Alpha Centauri is close enough to be intriguing: just about four years away if you travel at the speed of light. But at slower speeds,
it’s still pretty far. If the Voyager 2 spacecraft (which launched in 1977 and breached interstellar space in 2012) had gone in that
direction, it wouldn’t reach Alpha Centauri for another 75,000 years. We’ll need a quicker solution.
Back in 1998, one of Landis’ interstellar concepts was funded by NASA’s Innovative Advanced Concepts (NIAC) program; NIAC
examines far-out ideas for space exploration that may not be used for decades. In essence, Landis’ proposal suggested using
lasers to push a spacecraft equipped with sails, building on ideas published by physicist Robert Forward in 1984. The concept was
later picked up by the Breakthrough Starshot group, which in 2016 announced that it hopes to eventually send mini-spacecraft to
Alpha Centauri.
Landis said his idea would work for people, but unless you made the spacecraft very small (as Breakthrough proposes doing), you
would not get to Alpha Centauri quickly. It’s only if you “send a very small probe,” he told, “that you could make it
smaller and faster, and perhaps get to the nearest star in something less than a lifetime.”
NIAC continues to fund interstellar studies, as it did in 2017 when it awarded a Phase 1 grant to Heidi Fearn at the Space Studies
Institute in Mojave, California. The type of interstellar spacecraft propulsion studied in this grant might use Mach effects to move
across the universe. The term “Mach effects” refers to how the rest masses of objects vary as they accelerate, with changes
occurring to their internal energies

Several consistent medical problems have been encountered by astronauts during space flights.
These include vestibular dysfunction, weight loss, increase in height, upward fluid shift, anemia,
cardiovascular deconditioning, muscle atrophy, and bone loss. Almost all of these alterations can
be attributed to the absence of gravitational force. Most are adaptive in nature and therefore
reversible, but readaptation after returning to earth may cause further problems (e.g., in the case
of vestibular dysfunction). The most recalcitrant and disturbing of all these problems is the
relentless bone loss associated with negative calcium balance. This problem appears to be
irreversible, and critical demineralization can occur after two years in a weightless state. Unless
its mechanism is elucidated and preventive measures are taken, the bone loss may prove to be
the medically limiting factor for the duration of space flight.

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