Habitable Planet Found Only 22 Light Years From Earth!

[Ideologue]

Would a Jovian moon actually be able to support life?  Wouldn't the planet block the sunlight a lot?  Not to mention the radiation such a gas giant would emit.

Sure; yeah, but not to a significantly greater extent that the Earth blocks light on about half of its surface, and it's a lot better than a planetoid tidally locked to its star; it need not necessarily receive toxic levels of radiation--Titan doesn't, nor does Callisto (more or less).

I think Calisto is the only one that doesn't receive massive daily dosage of radiation, though it is still fairly significant.  How long would a moon be between a gas giant and the sun at a time?  What would the ratio of the moon in the sun and moon not in the sun be?  Using say the Sun, Calisto and Jupiter?

How often is Earth's moon exposed to the sun?  A lot; in fact, practically constantly.

I think you're imagining satellite systems as being insanely close to and constantly shadowed by their primary, when they aren't.  Jupiter is not in constant eclipse of the sun.

[Razgovory]

You are mistaken.
The Orion Project let us achieve 50% of lightspeed.
Ok, maybe 25%.
Still, we can get there.

That's bullshit.  You couldn't even do half that.  The best you could really do is .03 C, which is pretty quick, but would still take much, much longer then a human lifespan to arrive at another star (assuming you also want to stop there.  That is if the damn thing works at all.

[Lettow77]

 Science is like magic. What is needed is monolithic empires, ideological struggle, and triumph of the will. That will get us into space.

[Razgovory]

How often is Earth's moon exposed to the sun?  A lot; in fact, practically constantly.

I think you're imagining satellite systems as being insanely close to and constantly shadowed by their primary, when they aren't.  The far side of the Jovians get more insolation on average, but the point is, the sun is not constantly eclipsed by Jupiter even on Io, which orbits Jupiter at an even greater distance than Luna orbits Earth.

I'm imaging that Jupiter is much bigger then the Earth.  If the primary blocks out the sun for the moon for a quarter of the year it's going to get damn cold.

[Ideologue]

Why would a satellite that orbits its primary every 17 days be blacked out for a quarter of a year?

I mean, it's night here in the Western hemisphere.  Neither one of us have frozen to death yet.

[Razgovory]

Why would a satellite that orbits its primary every 17 days be blacked out for a quarter of a year?

I mean, it's night here in the Western hemisphere.  Neither one of us have frozen to death yet.

We aren't blacked out for three or four days at a time.

[Neil]

We could discover a habitable planet full of billions of nubile, Caliga-approved young ladies orbiting Proxima Centauri, 4-ish light years away...we still wouldn't even be able to imagine reaching it.

Yes we could. Orion Project, baby.

That can get you into space, but not between the stars.  Moving between the stars is an entirely different and more difficult problem then getting from the earth to space.

No, if it could work, it would be fine for interstellar travel.  Sort of.  You just coast, while the radiation flux from the atomic explosions damages the crew and instruments and the explosions themselves damage the ship.

[Neil]

How often is Earth's moon exposed to the sun?  A lot; in fact, practically constantly.

I think you're imagining satellite systems as being insanely close to and constantly shadowed by their primary, when they aren't.  The far side of the Jovians get more insolation on average, but the point is, the sun is not constantly eclipsed by Jupiter even on Io, which orbits Jupiter at an even greater distance than Luna orbits Earth.

I'm imaging that Jupiter is much bigger then the Earth.  If the primary blocks out the sun for the moon for a quarter of the year it's going to get damn cold.

Because the distances involved are very large, it's not as much of a factor as you might think.  If you look at Io, for example, it's only blacked out by Jupiter for a few hours when Jupiter is transiting the Sun, in a 42 hour orbit.  For Amalthea, which is closer still, it is only an hour and a half.  Because of orbital eccentricity, I wasn't able to get Ganymede or Calisto to black out at all, although I'm sure they do at some point.  Even so, the Jupiter transit is extremely brief.

[Razgovory]

Admittedly Jupiter is pretty far from the Sun, so it doesn't matter that much.  I was thinking of a Jovian Giant much closer.  Also, aren't moons around such a big object  tidally locked?

[Neil]

Admittedly Jupiter is pretty far from the Sun, so it doesn't matter that much.  I was thinking of a Jovian Giant much closer.  Also, aren't moons around such a big object  tidally locked?

It depends, but large moons that could bear life tend to be locked in the Solar System.  A life-bearing moon in the Io-Europa range would certainly have some interesting skies, with long days, long nights and a spectacular view of the giant planet.  Tidal locking to a planet shouldn't have much of an effect on the world, although tidal locking to a star would be disastrous.

[Razgovory]

Okay.  These were just things I wondered about.  I don't know much about this, so I'll defer to your and Ide's knowledge.

I do wonder what life would be like on a moon orbiting a gas giant in the habitable zone.

[OttoVonBismarck]

We could discover a habitable planet full of billions of nubile, Caliga-approved young ladies orbiting Proxima Centauri, 4-ish light years away...we still wouldn't even be able to imagine reaching it.

I can imagine quite a lot.

[Ideologue]

Why would a satellite that orbits its primary every 17 days be blacked out for a quarter of a year?

I mean, it's night here in the Western hemisphere.  Neither one of us have frozen to death yet.

We aren't blacked out for three or four days at a time.

Well, like Neil said, the eclipses don't last that long.  Each side will be in night for half its orbital period, but I assume we're talking about an Earthlike moon, with an atmosphere.  That will moderate global temperatures quite a bit.  Assuming Callisto distances (to get away from radiation) and velocity, an eight day night is no big deal.

Neil might know this, though: would the magnetosphere of an Earthlike moon afford sufficient/any protection from the radiation belts of a jovian?  That is, could a larger moon be closer than Callisto and not be a deathtrap?

[OttoVonBismarck]

As for Siege, while it may have seemed like it to the casual observer some 30 years ago, we really aren't in the equivalent of 1412 when it comes to space travel.

There a few major problems that potentially will never be solved. I think most/all of them will be solved, but it still doesn't solve "the biggest" problem.

To break it down:

• The energy requirements are absolutely massive. To make a trip to our closest star you could do it in a "reasonable" time at 10% of light speed. This is thousands of times faster than the fastest spacecraft humans have ever launched; due to the laws of physics this means we will need millions of times the energy used in other craft. I've seen it projected that to accelerate a 1 ton object to 10% light speed will take around 450 petajoules (.45 exajoules.) That isn't an impossible to reach power generation goal, all of human society generates around 474 EJ per year. However in a form to power a space ship isn't a simple problem. The Tsar Bomba which is the most powerful device ever utilized by man only released 210 PJ, so we're talking about some force at least twice as strong as that to knock a one ton object to Alpha Centauri at 10% light speed. In reality even the lightest manned craft to make a journey like that will weigh several times that amount and of course require more energy. Further, this number is just to accelerate the craft, I'm being generous and assuming maybe some crafty means is devised to avoid the necessity to use some sort of fuel to slow the craft down. A few years ago some professor estimated that a realistically sized craft making the journey in a reasonable time would require more than 100 times the energy output of the entire world. This seems plausible because of how the math works, minor increases in weight or desired velocity ratchet up the energy costs.
• Long term radiation exposure would be very damaging to the crew. There is no easy solution for this, moving at 10% light speed you'd get to Alpha Centauri in 40 years, even if we're talking 50% lightspeed it would be 8 years in space, much of it in interstellar space. And of course moving that number up to 50% changes the energy requirements massively as well. Even going up in the shuttle there is some radiation exposure, not a huge deal for short trips or even longer stays in a space station, but 8 years in a craft going through interstellar space I don't know that the health effects would be so minor.
• In the same vein of long term radiation, other minor things present in all space travel would compound immensely on a long interstellar journey. Micrometeroids would slowly cause damage to the craft, long term weightlessness would cause health problems to the crew, further when you're talking about a ship perhaps moving at appreciable percentages of light speed bad things might happen when something that fast is plowing through the interstellar medium, which has lots of dust and gases in it.
• The health concerns and engineering concerns are simply not minor, and solutions are not necessarily right around the corner for any of those, but I don't see any reason they could never be solved. The energy requirements issue is a far bigger problem, but again, I'm not sure we can't ever generate the energy required. We probably could using far more advanced fission-electric or fusion-burst type engines than we can build today. Fission-electric engines have a problem in that they probably would not be able to get a craft to 10% light speed in a reasonable time span, and fusion type drives would require massive, potentially centuries away, improvements to harnessing fusion in this manner because current fusion reactions release much of their energy as neutrons which significantly lessen the amount of energy available to drive the ship. However, let's assume we can solve all the engineering and actual science problems, at best I think we're talking 300-500 years of progress before we're there. But once we are there we're faced with the simple truth that such a voyage will always have massive costs, so high that it is virtually impossible to conceive of anything that would justify the cost. The movie Avatar talked of unobtanium being the reason man traveled to that planet, and priced it at around $20m a kg, in reality assume some magical resource on a planet 4 light years away, it would have to be worth hundreds of billions of dollars per ounce to even come close to justifying the cost required to actually go get any of it. Further, of course, we know the periodic table and the universe well enough to know that it's pure science fiction that some element unknown to man exists in quantity on another planet, any further elements we discover will be of the variety currently in the high numbers of the table which are all transient elements that decay in sub-second periods of time after being created. Now, some naturally occurring alloy or something of that nature could exist on another planet that would have value to human beings and that might not be present in large quantities here on Earth, but any society advanced enough to perform interstellar mining activities would almost certainly have the resources to create just about anything they'd need on their home planet and wouldn't need to expend massive resources on interstellar mining operations.[/i]
  

[The Brain]

Indeed physics is the problem. I see huge breakthroughs in biology/medicine the next few hundred years. I don't see as huge breakthroughs in physics. And building a fast interstellar ship with what we know seems difficult and expensive.