the $$$ used for researching and constructing a space-travelling vehicle that can transport humans to colonize other planet, and the amount of effort to transport people and materials blablablablalbla combined - we might as well use the $$$ to re-condition the earth.

Reconditioning the Earth yes is a good idea. But as u recondition the earth, you might as well think of the ever-increasing human population. Once u've got everything ready, Human population exceeds that of availability. So, why don't we travel to other planet, discover new species, phenomenon or even whole new thing to be added to our advantage to better Earth?

Scientist are also looking for water on Mars - possibility of life form on that Planet.

Let's make it simple.

1) Space travel is hazardous. Radiation levels are greatly elevated, especially in the case of a solar flare, with virtually no shielding other than the spacecraft itself, and research is going into finding different methods of shielding. Now take the distance to the next neighbouring star (which I doubt has planets), which works out to be about 400,000 times further away, and you have an idea of how far it has to go, and see 2) for how long it'll take.

2) Space travel takes ages. Current plans for travelling to Mars will take at the very least 8 months. Add that to shielding and you have big issues.

3) Habitability of other planets, most likely current candidate: Mars. Carbon dioxide dominated atmosphere, so we still have to get spacesuits, and still need sealed compartments. Also the issue of heating, since the atmosphere of Mars is so thin as to make it susceptible to large temperature fluctuations, which means more problems, and its weak magnetic field (approx 10^-4 of Earth's magnetic field) which means even more radiation shielding is required again.

Or put it this way: The problem with space travel is the humans themselves

Probing NASA's Plans For A Lunar Colony
ScienceDaily (Feb. 5, 2007) — The success of NASA's plans for a permanent human outpost on the moon may depend on the availability of technology that exploits the moon's environment and natural resources to obtain essentials like electric power, according to an article scheduled for the Feb. 5 issue of Chemical & Engineering News, the ACS' weekly newsmagazine.

In the article, C&EN associate editor Susan R. Morrissey discusses the ongoing debate about the need for humans to return to the moon, the costs, the scientific benefits of a lunar base and whether it should be in the hands of NASA or private industry.

If the project does move ahead, it may have to rely on technologies that utilize on-site resources to construct and sustain the base, the article notes.

At present, sponsors of the mission would face enormous per-kilogram costs for the solar cells and other gear that will have to be transported from Earth to the moon. Alternative approaches might avoid such sticker-shock, Morrissey notes.

One proposal, for instance, calls for using the lunar rocks and the moon's intense vacuum to make photovoltaic cells on site. Another approach calls for placing long strips of solar cells on the lunar surface, creating a large-scale solar power installation that could provide megawatts of electricity for lunar colonists.

At an altitude of 50 km above Venusian surface, the environment is the most Earth-like in the solar system - a pressure of approximately 1 bar and temperatures in the 0°C-50°C range. Because there is not a significant pressure difference between the inside and the outside of the breathable-air balloon, any rips or tears would cause gases to diffuse at normal atmospheric mixing rates, giving time to repair any such damages. In addition, humans would not require pressurized suits when outside, merely air to breathe and a protection from the acidic rain.

While a space elevator extending to the surface of Venus is impractical due to the slow rotation, constructing a skyhook that extended into the upper atmosphere and rotated at the wind speed would not be difficult compared to constructing a space elevator on Earth.

The main challenge would be using a substance resistant to sulfuric acid to serve as the structure's outer layer; ceramics or metal sulfates could possibly serve in this role.

First Habitable Earthlike Planet Found, Experts Say

James Owen
for National Geographic News
April 24, 2007

The first known planet beyond the solar system that could harbor life as we know it has been discovered, scientists report. The most Earthlike planet yet found, it orbits a red dwarf star and likely contains liquid water, said the European astronomers who made the discovery.

The planet is estimated to be only 50 percent larger than Earth, making it the smallest planet yet found outside the solar system, according to a team led by Stephane Udry of the Geneva Observatory in Switzerland.

Known as Gliese 581 c, the newfound world is located in the constellation Libra, some 20.5 light-years away. The planet is named after the red dwarf star it orbits, Gliese 581, which is among the hundred closest stars to Earth. Because the planet is 14 times nearer to its star than Earth is to the sun, a year there lasts just 13 days. Gravity on the planet's surface, though, may be twice as strong as Earth's gravity.

Despite the close proximity to its parent star, however, Gliese 581 c lies within the relatively cool habitable zone of its solar system. That's because red dwarfs are relatively small and dim, and are cooler than our sun, the team explained. The scientists estimated the planet's surface temperature at between 32 and 104 degrees Fahrenheit (0 and 40 degrees Celsius). "This means water can exist in liquid form," Udry said. "If you want life like our own, then you need water."

The team reports its findings in the journal Astronomy and Astrophysics. The new world could feature familiar, rocky terrains or be completely covered with oceans, the researchers said.

Source: National Geographic

1) Yes very true. Shielding itself is already a big issue to be thought of. With our current technology, we can't even shield nuclear explosion created by us. Well we don't really need to go to neighboring star. We can start off by sending humans to Mars.

It's not shielding explosions, it's shielding cosmic rays, shielding gamma rays. All the solutions that exist today weigh a bloody ton, and since space travel requires a small spacecraft mass for efficiency, you have a big big issue there.

Unless we have the technology to convert thess harmful rays into electrical energy, which would kill two birds with one stone.

i dont think its a source of energy. it aint sunlight.

Unless we have the technology to convert thess harmful rays into electrical energy, which would kill two birds with one stone.

Gamma Rays is a form of energy.