The Core Accretion model receives more abuse rhetorically from proponents of the GI model than accretion seems to give in return. This is due to the observational evidence that scientists have obtained which can potentially invalidate the accretion model - while still being too limited to validate the newer GI model. A major advocate for the GI model, Alan Boss, describes the failure of the accretion model by explaining that “the disk lifetimes appear to be too short for the commonly accepted mechanism” while utilizing more assured statements such as “Disk instability, the competing mechanism, can form giant planets” which works to heighten the appeal for GI (“Response” 462). In another article, GI supporters write of the accretion model as being “extremely sensitive” and highlight statements that “provided the planet survives” then perhaps accretion would work (Santos et al. 252). Their use of rhetoric in this manner works to emphasize the potential failure of the accretion model in light of new observations. However, the GI model is largely based upon a computer simulation – which means it too could potentially be refuted with additional observational evidence.
This need for observational evidence is exactly what the advocates for accretion highlight in order to downplay the validity of the GI theory. Author Jane Greaves admits that “the instability model produces planets very quickly”, however she is quick to note that it “requires a substantial disk, which is rarely observed” (Greaves 70). Until further evidence can be obtained, accretion advocates make case against the computer simulations used to illustrate this new model. Gregory Laughlin is an astrophysicist that does not advocate the GI model, and he explains that “computer simulations show that for fragments to form and persist as planets, the rate of cooling in the disk must be extremely efficient” (Laughlin 422). He also emphasizes that the “numerical experiments indicate that long before a disk attains sufficient mass for self-gravitation…it will form waves that act to push gas out” (Laughlin 423), taking away the necessary components of planet formation. The lack of observational evidence puts more weight on the rhetorical persuasion to cast doubt on the newer GI model and to remind readers that the core accretion model is still “the best guess currently” (Laughlin 423).
This need for observational evidence is exactly what the advocates for accretion highlight in order to downplay the validity of the GI theory. Author Jane Greaves admits that “the instability model produces planets very quickly”, however she is quick to note that it “requires a substantial disk, which is rarely observed” (Greaves 70). Until further evidence can be obtained, accretion advocates make case against the computer simulations used to illustrate this new model. Gregory Laughlin is an astrophysicist that does not advocate the GI model, and he explains that “computer simulations show that for fragments to form and persist as planets, the rate of cooling in the disk must be extremely efficient” (Laughlin 422). He also emphasizes that the “numerical experiments indicate that long before a disk attains sufficient mass for self-gravitation…it will form waves that act to push gas out” (Laughlin 423), taking away the necessary components of planet formation. The lack of observational evidence puts more weight on the rhetorical persuasion to cast doubt on the newer GI model and to remind readers that the core accretion model is still “the best guess currently” (Laughlin 423).