Quote:
Originally Posted by lagtight
The vast majority of astrophysicists believe that our solar system is billions of years old. We have comets in our solar system, and it is believed that a comet will "burn out" in about 100,000 years. In that case, where do "new" comets come from? The "billions of years" crowd have a rescuing device which is the existence of what they call an Oort Cloud. The Oort Cloud occasionally produces new comets. Unfortunately, to date there is no physical evidence for the Cloud, hence it is essentially a rescuing device. (Btw, there is nothing inherently wrong with rescuing devices; they are to some extent unavoidable.)
A scientific hypothesis is not a "rescuing device". The ability of humans to directly observe astronomical phenomena is obviously extremely limited. We can see some small percentage of the stars and some other objects, such as nebulae, galaxies, and the like, using our eyes and optical devices. And we can use various scientific instruments to detect such phenomena as various forms of radiation, cosmic rays, ions, etc.
So there's going to be plenty of things in the universe that exist but where there isn't some piece of evidence observable to humans that you would count as "physical evidence". Nonetheless, we can figure out what some of these things are, by using inductive reasoning. For instance, by definition, we can't directly observe a black hole. It's black! No light escapes from it. But we can hypothesize the existence of black holes based on known, observable facts about such things as mass and gravity, and the observed life cycles of large stars. And then we can look for evidence that confirms the hypothesis, such as accretion disks where matter is being sucked into a black hole, and objects whose paths are affected by the proximity of a black hole, etc.
At no point in that process is anything used as a rescuing device. Rather, data is examined, hypotheses are developed regarding what COULD explain what is being observed, and then additional observation and testing allow us to confirm, reject, and/or refine the hypothesis or to develop new hypotheses.
The Oort cloud isn't a rescuing device in any sense. It is an explanation for certain observed phenomena, including the paths of comets, and it is consistent with various observations. As any scientific hypothesis is, it is subject to additional refinement and even to falsification. It's highly unlikely that the Oort cloud is completely incorrect as a hypothesis, but science leaves open the possibility that astronomers at some point make some new observation that points to a different explanation for the phenomena that produced the Oort cloud hypothesis.
You are using a term-- "rescuing device"-- that more properly applies to the various moves that religious believers use to explain away conflicts between science and religion. "God made it look like the rocks are millions of years old when they weren't" is a rescuing device. So is "God created the world by starting the causal chain that was human evolution and directed it at every stage". Those are devices deployed to rescue religious beliefs from some inconvenient truths that science has discovered about the world.
But science doesn't use rescuing devices.