Intertellar Space Travel
Interstellar space travel is manned or unmanned travel between stars. The concept of interstellar travel via starships is a staple of science fiction. Interstellar travel is conceptually much more difficult than interplanetary travel. The distance between the planets in our solar system is typically measured in AU, while between the stars it's hundreds of thousands of AU and often expressed in light years. Intergalactic travel, or travel between different galaxies, would be even more difficult.
The difficulties of interstellar travel
The main challenge facing interstellar travel is the immense distance between the stars. This means both great speed and a long travel time are required. The time required by propulsion methods based on currently known physical principles would require years to millennia. Hence an interstellar ship would face many-fold, the hazards found in interplanetary travel, including vacuum, radiation, weightlessness, and micrometeoroids. The even the minimum multi-year travel times to the nearest stars are beyond current manned space mission design experience. The fundamental limits of space-time present another challenge. In economic terms interstellar missions would require several decades before a direct return on investment, though the technologies required to achieve such would have immediate benefits. (Source: image and text wikipedia)
Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins. (Source: image and text wikipedia)
Almost everywhere in the cosmos there is organic chemistry - in interstellar space or in the
If the chemistry behind life is common, perhaps life itself is widespread in cosmos. Only few planets around a sun orbit in the life zone and have a stabilizing moon, so most of them have much more variable conditions for life than on earth.
Interaction of plate tectonics, weathering and biology creates an equilibrium between the gas concentrations in the atmosphere, in the oceans, the biomasses in the rocks over 4 ½ billion years.
That controls the climate, changes landscapes, forces life to adapt. Evolution is an arms race between predators and hunted. Each species has a date of birth, exists a long time on earth and then
dies again sometime. On average a species lives 4 million years.
Will the long road to intelligent life on exoplanets be shorter, are there abbreviations possible? Would life once again have the same development? Climate variability enabled our evolution. Evolution went on not longer by physical adjustment, but homo developed stone tools for grinding food. The type which learned the use of tools had continued to evolve, it evolved to homo sapiens 900 000 years ago. If important factors such as gravity, atmosphere, salinity of the oceans etc. remained the same: it would not have caused humans, but intelligent beings. Wide regions in the Milky Way are uninhabitable. In spherical halo there are old stars that have little of rocky planets.
Earth is in a more moderate zone of the Milky Way, in the thin galactic disk, here the proportion of rock-forming elements is high enough for terrestrial planets. Here supernovae are rare, that means the cosmic radiation has its limits. Where the disc is thicker radiation is not suitable for organic life.
Only 10% of all stars in our galaxy are located in this zone, half of them is older than the sun.
This means, according to Charley Lineweaver of the University of New South Wales, the ecological
niche for exoplanets where life may develop is smaller than it appears. Source: Dagmar Röhrlich- Hi, anyone out there? Spectrum Verlag 2009
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