|
Top Document: [sci.astro] ET Life (Astronomy Frequently Asked Questions) (6/9) Previous Document: F.04 What is the Fermi paradox? Next Document: F.06 How far away could we detect radio transmissions? See reader questions & answers on this topic! - Help others by sharing your knowledge Yes, although present observations can do so only under optimistic assumptions. Radio and optical searches currently underway are aimed at detecting "beacons" built by putative advanced civilizations and intended to attract attention. More sensitive searches (e.g., Project Cyclops) that might detect normal activities of an advanced civilization (similar for example to our military radars or TV stations) have been proposed but so far not funded. No funding of these is likely until the search for beacons is far closer to being complete. Why get involved with the difficult until you are done with the easy? Ordinary astronomical observations are most unlikely to detect life. The kinds of life we speculate about would be near stars, and the light from the star would conceal most signs of life unless a special effort is made to look for them. Within the solar system, the Viking landers found conditions on the surface of Mars unlikely to support life as we know it. The mass spectrometer found too little carbon, which is the basis for organic molecules. The chemistry is apparently highly oxidizing as well. Some optimists have nevertheless argued that there still might be life on Mars, either below the surface or in surface regions not sampled by the landers, but most scientists consider life on Mars quite unlikely. Evidence of surface water suggests, however, that Mars had a wetter and possibly warmer climate in the past, and life might have existed then. If so, there might still be remnants (either living or fossil) today, but close examination will be necessary to find out. Other sites that conceivably could have life include the atmosphere of Jupiter (and perhaps Saturn) and the presumed liquid water under the surface ice of Jupiter's satellite Europa. Organisms living in either place would have to be very different from anything we know on Earth, and it's hard to know how one would even start to look for them. Concepts for specialized space missions that could detect Earth-like planets and return spectral information on their atmospheres have been suggested, and either NASA or ESA may launch such a mission some time in the next two decades (see <URL:http://techinfo.jpl.nasa.gov/www/ExNPS/HomePage.html> and <URL:http://ast.star.rl.ac.uk/darwin/>). The evidence for life would be detection of ozone (implying oxygen) in the planet's atmosphere. While this would be strong evidence for life---oxygen in Earth's atmosphere is thought to have come from life---it would not be ironclad proof, as there may be some way an oxygen atmosphere could form without life. For more information, see references at the end of F.06. Also, check out the SETI Institute Web site at <URL:http://www.seti-inst.edu>. User Contributions:Comment about this article, ask questions, or add new information about this topic:Top Document: [sci.astro] ET Life (Astronomy Frequently Asked Questions) (6/9) Previous Document: F.04 What is the Fermi paradox? Next Document: F.06 How far away could we detect radio transmissions? Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
|
with stars, then every direction you looked would eventually end on
the surface of a star, and the whole sky would be as bright as the
surface of the Sun.
Why would anyone assume this? Certainly, we have directions where we look that are dark because something that does not emit light (is not a star) is between us and the light. A close example is in our own solar system. When we look at the Sun (a star) during a solar eclipse the Moon blocks the light. When we look at the inner planets of our solar system (Mercury and Venus) as they pass between us and the Sun, do we not get the same effect, i.e. in the direction of the planet we see no light from the Sun? Those planets simply look like dark spots on the Sun.
Olbers' paradox seems to assume that only stars exist in the universe, but what about the planets? Aren't there more planets than stars, thus more obstructions to light than sources of light?
What may be more interesting is why can we see certain stars seemingly continuously. Are there no planets or other obstructions between them and us? Or is the twinkle in stars just caused by the movement of obstructions across the path of light between the stars and us? I was always told the twinkle defines a star while the steady light reflected by our planets defines a planet. Is that because the planets of our solar system don't have the obstructions between Earth and them to cause a twinkle effect?
9-14-2024 KP