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Solution to the Problem of Intergalactic Travel

2 points by Kinnard 11y ago

dalke 11y ago
To start with, the article it titled "The Problems of Intergalactic Travel and Jewish Continuity", not "Solution to the Problem of Intergalactic Travel". Then whoever gave the title (which is often the editor and not the author) doesn't have a sense of scale. Travel to Alpha Centauri is intersteller travel, not intergalactic travel, that is, 4 light years compared to 70,000. The piece considers that the only solution is a generation ship, which leads to a new set of problems. Food is one. It says "There’s sunlight in most of outer space, so algae could be grown on the collected sweat and urine from the humans." That rang alarm bells. Outside of the solar system, the "sunlight" is really "starlight". It's not possible to support people on sun/starlight at that distance. Back of the envelope calculation: "Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1366 W/m2." Which means at 1 light year away (63,241 AU), or 1/4th of the way to Alpha Centauri, the energy density is 1366/63241/63241 = 0.34 µW/m2. Basal metabolism is 100 W, so assuming impossible pure energy conversion, each person needs about 300 sq. kilometers of collection area to provide enough energy. The second one is, how do can it have a stable social system across multiple generations? One professor made the observation "So far as I know, they’re the only group of people who, for thousands of years, have managed to hand down their traditions intact to each new generation." That's another alarm bell. An astrobiologist likely knows little about anthropology. Buddhism, Confucianism, and Zoroastrianism also have passed down traditions 'intact to each new generation', even to the present. Parts of the Vedas are 3,000 years old. Surely we need to look at multiple such systems to see what they have in common, rather than doing what the author of this piece does and examine only the Jewish rabbinic tradition. It then correctly points out that a stable culture isn't enough. But it does so with at best a lay understanding of gravity. "The real problem is that after the first two hours, after the ship leaves the gravitational pull of the earth from that moment on, everyone, for all generations, will live in a weightless environment." Why "two hours"? Will the ship boost for two hours? The most meaningful definition for the 'gravitational pull of the earth' is to be within the Hill sphere of ~1.5 million km. Basic physics says that ship needs to pull about 6 gravities to do that. And why won't the generation ship spin in order to maintain gravity? We know that long-term zero gee is not good for the body. Since this piece isn't meaningfully about the science, I conclude it's more likely written to promote or at least maintain a sort of exceptionalism about the Jewish faith.
whoopdedo 11y ago
So let me see if I have this correct. Did Prof. Greene essentially propose creating a new religion for the preservation of scientific knowledge?

2 points by Kinnard 11y ago

dalke 11y ago

To start with, the article it titled "The Problems of Intergalactic Travel and Jewish Continuity", not "Solution to the Problem of Intergalactic Travel". Then whoever gave the title (which is often the editor and not the author) doesn't have a sense of scale. Travel to Alpha Centauri is intersteller travel, not intergalactic travel, that is, 4 light years compared to 70,000. The piece considers that the only solution is a generation ship, which leads to a new set of problems. Food is one. It says "There’s sunlight in most of outer space, so algae could be grown on the collected sweat and urine from the humans." That rang alarm bells. Outside of the solar system, the "sunlight" is really "starlight". It's not possible to support people on sun/starlight at that distance. Back of the envelope calculation: "Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1366 W/m2." Which means at 1 light year away (63,241 AU), or 1/4th of the way to Alpha Centauri, the energy density is 1366/63241/63241 = 0.34 µW/m2. Basal metabolism is 100 W, so assuming impossible pure energy conversion, each person needs about 300 sq. kilometers of collection area to provide enough energy. The second one is, how do can it have a stable social system across multiple generations? One professor made the observation "So far as I know, they’re the only group of people who, for thousands of years, have managed to hand down their traditions intact to each new generation." That's another alarm bell. An astrobiologist likely knows little about anthropology. Buddhism, Confucianism, and Zoroastrianism also have passed down traditions 'intact to each new generation', even to the present. Parts of the Vedas are 3,000 years old. Surely we need to look at multiple such systems to see what they have in common, rather than doing what the author of this piece does and examine only the Jewish rabbinic tradition. It then correctly points out that a stable culture isn't enough. But it does so with at best a lay understanding of gravity. "The real problem is that after the first two hours, after the ship leaves the gravitational pull of the earth from that moment on, everyone, for all generations, will live in a weightless environment." Why "two hours"? Will the ship boost for two hours? The most meaningful definition for the 'gravitational pull of the earth' is to be within the Hill sphere of ~1.5 million km. Basic physics says that ship needs to pull about 6 gravities to do that. And why won't the generation ship spin in order to maintain gravity? We know that long-term zero gee is not good for the body. Since this piece isn't meaningfully about the science, I conclude it's more likely written to promote or at least maintain a sort of exceptionalism about the Jewish faith.

whoopdedo 11y ago

So let me see if I have this correct. Did Prof. Greene essentially propose creating a new religion for the preservation of scientific knowledge?