Posted on 07/30/2004 11:12:50 AM PDT by PatrickHenry
We could be alone in the Universe after all. The discovery during the past decade of over a hundred planets around other stars has encouraged many scientists to think that habitable planets like ours might be common. But a recent study tells them to think again.
Martin Beer of the University of Leicester, UK, and co-workers argue that our Solar System may be highly unusual, compared with the planetary systems of other stars. In a preprint published on Arxiv1 [footnote's link in original article], they point out that the alien planets we have seen so far could have been formed by a completely different process from the one that formed ours. If that is so, says Beer, "there won't necessarily be lots of other Earths up there".
Most of the planets around other stars, known as extrasolar planets, are detected from the wobble that they induce in their own sun's motion. This wobble is caused by the gravitational tug of the planet on the star. Because stars are much bigger than planets, the effect is tiny, and it is only in the past decade that telescopes have been sensitive enough to detect it.
Even then, the wobble is detectable only for giant planets, which are those about as big as Jupiter, the bloated ball of gas in our Solar System. It is not possible at present to detect planets as small as the Earth.
Jupiter is not habitable: it is too cold, and is mostly composed of dense gas. And it is unlikely that extrasolar giant planets would support life either. But astronomers generally assume that if they detect such a planet in a distant solar system, it is likely to be accompanied by other, smaller planets. And maybe some of the smaller planets in these systems are just like Earth.
This is what Beer and colleagues now dispute. They say that the properties of almost all the known extrasolar planets are quite different from those of Jupiter.
Hot Jupiters
There are 110 of these extrasolar planets, at the latest count, and they are all between about a tenth and ten times as massive as Jupiter. Most of them are, however, much closer to their sun than Jupiter is to ours: they are known as 'hot Jupiters'. They also tend to have more elongated orbits than those of Jupiter and the Earth, both of which orbit the Sun on almost circular paths.
Ever since Copernicus displaced the Earth from the centre of the Universe, astronomers have tended to assume that there is nothing special about our place in the cosmos. But apparently our planetary system might not be so normal after all. Is it just chance that makes Jupiter different from other extrasolar planets? Beer and his colleagues suspect not.
They suggest that other planets were not formed by the same kind of process that produced our Solar System, so they might not have smaller, habitable companions.
Different recipes
The planets in our Solar System were put together from small pieces. The cloud of gas and dust that surrounded our newly formed Sun agglomerated into little pebbles, which then collided and stuck together to form rocky boulders and eventually mini-planets, called planetesimals. The coalescence of planetesimals created rocky planets such as Earth and Mars, and the solid cores of giant planets such as Jupiter, which then attracted thick atmospheres of gas.
But that is not the only way to make a solar system. Giant planets can condense directly out of the gaseous material around stars, collapsing under their own gravity. This process, which generates giant planets with a wide range of orbital radii and eccentricities, does not seem capable of producing the rocky planets seen in our own Solar System, which is why it has generally been ignored.
Yet it might account very nicely for the known extrasolar planets. "It wouldn't surprise me if there are two different ways that planetary systems are formed," Beer says. But how can we know if that is the case? "Probably the best way is just to gather more observations," says Beer. Only then can we know how unusual we really are.
There are many assumptions here. IMHO, "Rare Earth" falls in the realm of sensationalism and/or junk science.
I'm not sure I understand what you were trying to say with that statement.
Here was my statement: For the record, I do not believe there are life bearing planets out there; however, I do suspect there are.
What I was trying to say, was that I do not believe in ET. However, I suspect there may be other life out there. In other words, I will let the evidence speak for itself as we continue to learn more about this universe.
I realize that this is not exactly the forum for discussing complicated scientific issues, but I am surprised that you think so little of Brownlee and Ward. My understanding is that they are well respected in their fields. Not every astronomer, geologist, astrobiologist or astrophysicist may agree with their conclusions, but I doubt they would accuse Brownlee and Ward of pushing junk science. I agree that the field is open to speculation because the whole field of astrobiology is rather young, but if Rare Earth is junk science, then so is SETI and the Drake equation.
What I was trying to say, was that I do not believe in ET. However, I suspect there may be other life out there. In other words, I will let the evidence speak for itself as we continue to learn more about this universe.
Thanks for the explanation. That is a reasonable position to take since there is at this time no evidence whatsoever of extra-terrestial life. Since disproving the existence of extra-terrestial life is an impossible task, even if no extra-terrestial life exists, then the logical position to take is to keep an open mind.
Sigh. I was too harsh in my statement. What I am trying to convey is that people seem to latch onto each extreme in this debate. I decided to take a "wait and see" attitude. This is why I think SETI is so important. It is win win science. Either they are all over, or they are damn hard (or impossible because they don't exist/out of range time etc.) to detect. Both cases lend to further defining our place in this universe.
But isn't it just possible that God did not reveal to us absolutely everything that He did in the Bible. It doesn't say in the Bible that He did or He did not create other planets. The singular usage for earth doesn't prove He didn't. Maybe He gave a different name to the other planet(s) that He created. We just don't know at this point. For either religious people or scientists to suggest that we do know is ridiculous.
This has made a lot of people very angry and been widely regarded as a bad move.
Of course, in order for the earth to be the only planet that has life, you have to eliminating 99% of all stars is insufficient. If you assume that the milky way has ~10^8 stars and that there are maybe 10^8 other galaxies out there, then there are 10^16 stars to be considered. If you eliminate 99% of them that leaves 10^14 planets which still could contain life. You'd have to eliminate 99.99999999999999% of the stars. So far, nobody has given convincing evidence for elimination of that high a percentage of stars. Life may not be very common, but it doesn't have to be common for there to be other life besides that on earth.
?
Not at all!!! For example, we used to believe that the force that drove a compass needle, the force that destroys your house when it's hit by lightning, and the force that presses back against you when you push on a wall were all different things. Now as science has advanced and we've learned more, we learned that all of these things (as well as many others) were simply different manifestations of the same thing, namely the electromagnetic force. Furthermore, we learned that all of these phenomena can be described by a set of FOUR EQUATIONS. In fact, adding the equation for universal gravitation, we've learned that most of the phenomena of human experience can, in principle, be described by FIVE equations. The entire history of scientific inquiry has been one of simplification and unification, not one of increasing complexity. It may seem, to a non-scientist, that things are more complex, but to scientists this is not the case.
Is Mars mentioned in the Bible???
In a way, you are proving my point. With things like gravity or lightning, the more we've learned about them, the easier they are to understand. But with things like DNA, the Cell, and the unique congruence of "coincidences" that occur on earth in a way that is capable of sustaining so much life, the more we learn, the more complex things get.
Widey regarded by whom? Did I miss something?
Not only is it possible that God did not reveal to us absolutely everything that He did in the Bible, but I know He didn't.
But that doesn't prove that He did. I can only rely on what He said He did. Not on what He might have done and it looks like the latest science (i.e. this article) seems to support the Bible's perspective that there is only one earth...
"Something with more moving parts would have more degrees of freedom. More degrees of freedom implies more possible configurations at any given time which would lend itself to a stochastic approach"
So a watch (more moving parts) is more likely a result of chance than a tombstone? Obviously both items had a designer... Why does your theory hold true? Because you can back it up by saying stochastic approach? I think you know that the route of the argument is that you don't admit the existence of a creator, therefore you theorize from that point of reference.
So then, God didn't create gravity and lightning??? You can't have it both ways.
But my point was that we really can't claim knowledge of whether or not life exists on other planets, either from a religious or a scientific perspective. I think you've just confirmed that point, at least from the religious perspective. God has given us no reason to believe that there are other planets with life. On the other hand, He has not specifically told us that these other life-bearing planets don't exist.
It's a line from "Hitchikers Guide to the Galaxy."
The other choice is organic. Stochastic or organic.
No, I'm not having it anyway. I believe that God created everything, the simple and the complex. I just happen to believe that the complexity of the universe would lead a reasonable person to see taht it was designed.
Total Non-sequitur...
I don't think that other planets in the solar system is mentioned in the Bible either.
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