Spreading life through the galaxy (travel) + Returning to starting point in space

C C Offline
Comet-like objects could be spreading life from star to star throughout the Milky Way

EXCERPT: When the U.S. football field–size, cigar-shaped object ‘Oumuamua entered our solar system last year, it didn’t just give us our first glimpse of an interstellar piece of rock. It also bolstered the plausibility of space rocks spreading life among the stars by ferrying microbes between distant star systems, according to a new study. [...] The idea, known as panspermia, has been around for centuries. Some astronomers have even speculated that life on Earth was seeded by microbes that hitched a ride on debris ejected from another life-harboring world in the solar system, perhaps on meteorites from Mars. But it seemed improbable that life could have come from interstellar space.

[...] In the new study [...] astrophysicists [...] calculated the chances of such objects delivering life to an alien world. A binary star such as Alpha Centauri would ensnare a few thousand rocks of ‘Oumuamua’s size every year, and our solar system might snag one a century [...] researchers then multiplied this capture rate by the number of stars an interstellar object will encounter before whatever bugs it carries all die. If the objects move, like ‘Oumuamua, at a velocity of 26 kilometers per second through interstellar space, 10 million of them will be captured somewhere in the Milky Way in a million years. “If you look at the galaxy as a whole, you expect this to happen fairly often,” Ginsburg says.

Astronomer Jason Wright of Pennsylvania State University in State College says the analysis has merit: “For reasonable numbers, this suggests that planets and asteroids are commonly exchanged between stars.”

But astronomer Ed Turner of Princeton University says the authors may be reading too much into the single example of ‘Oumuamua. “There’s no rigorous mathematical argument you can write about one event evaluated a posteriori,” he says.

And even if our galaxy is thick with ‘Oumuamuas, they are unlikely vectors of panspermia, Melosh says. ‘Oumuamua is way too big to have been ejected from an inhabited planet, he says....

MORE: https://www.sciencemag.org/news/2018/10/...-milky-way

If you traveled far enough through space, would you return to your starting point?

EXCERPT: . . . could it be the case, just as the Earth has two dimensions we can move in on it [minus drilling equipment], that the Universe might be a higher-dimensional structure like a hypersphere or a hypertorus where the various dimensions are closed and finite, curving back on themselves? If that were the case, if you could travel in a straight line for long enough, you would wind up right back where you started.

[...] If the Universe were finite and closed on itself — if parts of it repeated in other places — the cosmic microwave background would hold the evidence. [...] We've searched exhaustively for it, and that evidence simply isn't there. But the lack of such a detectable, repeating structure doesn’t necessarily mean that the Universe doesn’t have this type of topology. It only means that if the Universe does repeat, if it is a closed hypersurface, and if we could theoretically re-emerge in the same spot after traveling in a straight line for long enough, it is so on a scale that’s larger than the part we can observe. Given that we’re limited to how far light can travel in 13.8 billion years, there’s plenty of room for this to still be the case.

But there’s a catch. [...] the expansion of the Universe — accelerating as it is — forbids us from ever completing a single “circumnavigation” of the Universe and returning to our origin. Because of the combination of:

the finite age of the Universe,
the finite speed of light,
the expansion of the Universe and
the presence of dark energy [acceleration],

we may never be able to know whether our Universe is infinite or not, and what its true topology is. We can only see what we have access to, and that doesn't appear to be enough to be decisive concerning scales larger than what we can observe...

MORE: https://www.forbes.com/sites/startswitha...ing-point/
Zinjanthropos Offline
Don't know if it's ever been considered but what are the chances that some of the necessary ingredients for life are contained in many clumps of rock/matter since the BB? Eventually one of these drifting bodies smashes into a planet where it just so happens there's an abundance of necessary chemicals required to finish the life casserole. Add water, stir and cook in the heat of a star. No true life travels intergalactically, only a part of the recipe. My two cents.

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