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March 22, 2016 | Author: | Posted in geology and geophysics, nature

The orbits of the planets are coplanar because during the Solar System ‘s formation , the planets formed out of a disk of dust which surrounded the Sun . Because that disk of dust was a disk , all in a plane , all of the planets formed in a plane as well

Rings and disks are common in astronomy . When a cloud collapses , the conservation of angular momentum amplifies any initial tiny spin of the cloud . As the cloud spins faster and faster , it collapses into a disk which is the maximal balance between gravitational collapse [banner_entry_middle]

and centrifugal force created by rapid spin . The result is the coplanar planets , the thin disks of spiral galaxies , and the accretion disks around black holes

Due to the varied distances from the sun and the different modes of formation , the outer and inner planets have many unique characteristics For example , the sizes of the inner planets are much smaller than those of the outer planets . This is because the outer planets are in a gaseous state while the inner planets are solid and more compact . Consequently the density of the inner planets is greater than that of the outer planets . Despite the density differences , the mass is smaller for the inner planets than the outer planets . One suggested reason for this is that the rocky planets have a iron core whereas the outer planets may not . Another explanation is that although the outer planets are larger they are primarily composed of gases , which are characteristically less dense than solids

Generally , EM radiation is classified by wavelength into electrical energy , radio , microwave , infrared , the visible region we perceive as light , ultraviolet , X-rays and gamma rays

The behaviour of EM radiation depends on its wavelength . Higher frequencies have shorter wavelengths , and lower frequencies have longer wavelengths . When EM radiation interacts with single atoms and molecules , its behaviour depends on the amount of energy it carries

Spectroscopy can detect a much wider region of the EM spectrum than the visible range of 400 nm to 700 nm . A common laboratory spectroscope can detect wavelengths from 2 nm to 2500 nm . Detailed information about the physical properties of objects , gases , or even stars can be obtained from this type of device . It is widely used in astrophysics . For example , many hydrogen atoms emit radio waves which have a wavelength of 21 .12 cm

EM radiation with a wavelength between approximately 400 nm and 700 nm is detected by the human eye and perceived as visible light

If radiation having a frequency in the visible region of the EM spectrum reflects off of an object such as a bowl of fruit , and then strikes the eyes , this results in our visual perception of the scene . Our brain ‘s visual system processes the multitude of reflected frequencies into different shades and hues , and through this not-entirely-understood psychophysical phenomenon , most people perceive a bowl of fruit

In the vast majority of cases , however , the information carried by light is not directly detected by… [banner_entry_footer]

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