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## Possible Habitable Planet Just 12 Light Years Away420

sciencehabit writes "Astronomers have discovered what may be five planets orbiting Tau Ceti, the closest single star beyond our solar system whose temperature and luminosity nearly match the sun's. If the planets are there, one of them is about the right distance from the star to sport mild temperatures, oceans of liquid water, and even life (paper)."
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## Possible Habitable Planet Just 12 Light Years Away

• #### Re:"JUST" 12 light years? LOL. (Score:5, Informative)

on Wednesday December 19, 2012 @12:00AM (#42333513)

The math is wrong - Voyager I is 0.71 light days away, or 0.0019 light years away. It will take a lot longer than 840 years to get to another star.

• #### Re:Definitely NOT Earth 2 (Score:5, Informative)

on Wednesday December 19, 2012 @12:16AM (#42333591)

Gravity is GM / R**2. Mass is proportional to R**3, which means that Gravity is proportional to R, if the density is the same. Inverting that, Gravity is proportional is M**(1/3), so 4 times the mass is 1.587 times the gravity (for a constant density).

So, I wouldn't rule it out.

• #### Re:"JUST" 12 light years? LOL. (Score:4, Informative)

on Wednesday December 19, 2012 @12:22AM (#42333627)

Even if it managed to get to a blisteringly fast .1c, you're still looking at longer than a human lifespan and generation ships.

• #### Re:"JUST" 12 light years? LOL. (Score:5, Informative)

on Wednesday December 19, 2012 @12:37AM (#42333689)
Um, that's not quite how orbital mechanics works. Helios II started off from the earth - that is, with a lot of potential energy in the sun's gravitational field. It was put into an elliptical orbit around the sun, so on its closest approach, part of that potential energy was converted to kinetic energy (hence the high velocity), but at the most distant point, it's all converted back to potential energy, and there's zero gain. It's a bit like bouncing a rubber ball off the floor: it's surely going to hit the ground at a high velocity, but it's never going to bounce up higher than it started - no free lunch. The reason why slingshotting between planets works is because they move relative to each other. To use the rubber ball analogy again, if you throw a rubber ball at the front of a truck that is rapidly approaching you, the rubber ball will come back with a higher velocity. What you did is subtracting kinetic energy from the truck, just like a slingshotting probe subtracts kinetic energy from a moving planet. The tricks we use to make space probes gain kinetic energy are not unlike bouncing a rubber ball repeatedly between moving walls. To use the sun for slingshotting, one would require a very massive object in a highly eccentric orbit around the sun as a "second wall", which our solar system unfortunately doesn't have. (Or should that be: fortunately for our existence?) One could try to use pluto, but I doubt it's massive, eccentric and fast enough to be worth it.

Disclaimer: the above explanation is obviously somewhat oversimplified.
• #### Re:It goes the other way, too (Score:4, Informative)

<xstonedogx@gmail.com> on Wednesday December 19, 2012 @02:09AM (#42334095)

SETI is looking for intentional signals, not the alien equivalent of Abbot and Costello.

• #### Re:Just like Venus (Score:3, Informative)

on Wednesday December 19, 2012 @02:50AM (#42334287) Journal

No, it isn't. The sun's habitable zone is between 0.9 AU and 1.5 AU. The maximum distance of Venus to the sun is 0.728 AU. So Venus doesn't even come close to the habitable zone.

• #### Vulcans Invented The Prime Directive (Score:5, Informative)

on Wednesday December 19, 2012 @03:10AM (#42334381)

The Vulcans came from the habitable planet that orbited Tau Ceti, according to my Starfleet Technical Manual. Given that they invented the Prime Directive, they probably have to maintain radio silence (frex, using very directional masers where necessary for radio-band communications) to avoid clueing in lesser civilizations.

Plus the Andorians live right next to them and we all know what they are like.

• #### 210 posts and nobody mentioned Asimov? (Score:5, Informative)

on Wednesday December 19, 2012 @04:16AM (#42334625) Homepage Journal

He had foreseen this. The planet around Tau Ceti is called Aurora. It is the home of long-living humans and mind-reading robots.

• #### Re:It goes the other way, too (Score:5, Informative)

on Wednesday December 19, 2012 @05:09AM (#42334811)
No, you do mean the inverse square law. The inverse square law states that the intensity of radio waves (or light) decreases with the square of the distance to the source. The square-cube law is about the surface relative to the volume: The surface increases with the square of the size, while the volume increases with the cube. This means that the same structure at different sizes would not have the same properties. For example, a giant ant would not be able to get enough oxygen, as its ability to get oxygen follows its surface area, while its oxygen demand follows its volume. Likewise, it would be crushed under the weight of its own exoskeleton, as its strength is proportional to the square of the size, while its weight is proportional to the cube.

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