Question

You are describing the solar nebula theory to a friend. You point out that it provides an explanation for the regular motion in our solar system, the division of the planets into terrestrial and jovian types, and an explanation for the origin and nature of comets and asteroids. Your friend agrees that this is all very nice, but that it seems that the solar nebula theory fails the basic criteria for a scientific theory, to make predictions about the natural world that can be observationally tested. In her opinion, all the solar nebula theory does is explain known facts, albeit in a compelling and economical way. How would you answer your friend and make the case that the solar nebula theory is indeed a scientific theory that has passed many observational tests? Can you think of any predictions that the solar nebula theory has made that were confirmed only within the last decade or so?

Answer 1

The Sun and planets Solar System began as a giant cloud of molecular gas and dust.About 4.57 billion years ago, something happened that collapsed the cloud.(could be the aftereffect of a passing star, or shock waves from a supernova).From this gravitational collapse, pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more matter, conservation of momentum caused it to begin rotation.Increasing pressure caused it to heat up. Most of the material ended up in a ball at the center and the rest of the matter flattened out into disk that circled around it. While the ball at the center formed the Sun, the rest of the material would form into the protoplanetary disc.The planets formed by accretion from this disc, in which dust and gas gravitated together and coalesced to form ever larger bodies. Solar Nebular Disk Model (SNDM) model has been successful in explaining the appearance of accretion discs around young stellar objects. Various simulations have also demonstrated that the accretion of material in these discs leads to the formation of a few Earth-sized bodies.

• Stars are born in the dusty gas clouds. Driven by gravity, denser parts of the cloud collapses further to form "cores". False color HST image of a Galactic nebula called M16 is one proof.
• As the gas core collapses on itself due to its own weight, a disk of gas and dust is formed. Gas and dust falls in so quickly with so much energy that sometimes a jet of material is seen being shot out. (false color HST images of nearby young stellar systems are proof.)
• Sometimes strong winds and shocks from the nearby young stars can "blow out" the dusty cover of the young solar systems and reveal the remnants of the forming solar system. (false color HST images of young stellar systems being revealed by the ionizing radiation of the luminous neighboring young stars in Orion Nebula is yet another proof
• When the solar system is finally formed and dust has cleared, remnants of the formation process and outlying material in the solar systems (such as "Kuiper belt objects" and "Oort clouds") can be found surrounding the systems. (false color image of a dusty disk seen around a nearby star named Fomalhaut, imaged in submm/infrared light at James Clark Maxwell Telescope on Mauna Kea, Hawaii can be googled)
• Remnants of the solar system formation can also be seen in visible or infrared light around some of the nearest stars when the bright light from the central star can be blocked out. (false color image of a dusty disk (rocks and ice chunks) seen around a nearby star named beta Pictoris, imaged at European Southern Observatory.)