Chapter 11 Concepts

It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
Explanation: One major drawback to the idea that the Sun stayed hot due to gravitational contraction was that it did not explain how the Sun could maintain its high rate of energy production for such a long time. Additionally, the theory could not account for the observed changes in the Sun's brightness over time.

It was important when the Sun was forming from a shrinking interstellar cloud of gas.
Explanation: Gravitational contraction is an important energy generation mechanism for the Sun because it is the mechanism by which the Sun converts its gravitational potential energy into heat and light. Gravitational contraction is the process by which a star or other gravitationally bound object contracts under the influence of its own gravity. As the object contracts, its gravity increases and its potential energy decreases. The potential energy is converted into heat and light, and the object becomes smaller and hotter.

There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
Explanation: Gravitational equilibrium is a state of balance between the inward pull of gravity and the outward push of the Sun's pressure. The Sun is in gravitational equilibrium because the force of gravity is equal to the force of the Sun's pressure.

As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
Explanation: The Sun shines because it is a star that is powered by nuclear fusion.

The Sun's mass is about 300,000 times the mass of the Earth.
Explanation: The Sun's mass is about 333,000 times Earth's mass.

Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
Explanation: The Sun emits most of its energy in the form of visible light because visible light has the most energy of all the colors in the electromagnetic spectrum.

We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
Explanation: The Sun is a star that is constantly undergoing nuclear fusion. This nuclear fusion creates a lot of heat and energy. The Sun's surface seethes and churns with a bubbling pattern because the heat and energy from the nuclear fusion is constantly causing the surface to move around.

The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
Explanation: Nuclear power plants work by using nuclear fission to generate heat, which is then used to produce steam, which in turn drives turbines that generate electricity. The Sun's energy generation process is similar, except that it uses nuclear fusion to generate heat, which is then used to produce steam, which in turn drives turbines that generate electricity.

converted to an amount of energy equal to 4 million tons times the speed of light squared
Explanation: The remaining 4 million tons of mass is converted into energy.

Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
Explanation: Nuclear fusion is the process of two nuclei coming together to form a single, heavier nucleus. In order for this to happen, the nuclei must be brought extremely close together so that their strong nuclear forces can overcome the electrostatic repulsion between them.

The core would heat up, fusion rates would increase, the core would re-expand.
Explanation:Nuclear fusion is the process of two nuclei coming together to form a single, heavier nucleus. In order for this to happen, the nuclei must be brought extremely close together so that their strong nuclear forces can overcome the electrostatic repulsion between them.

Fusion in the Sun's core creates neutrinos.
Explanation: The Sun emits neutrinos because it is constantly undergoing nuclear fusion reactions. In these reactions, hydrogen atoms are combined to form helium atoms, releasing energy in the process. Some of this energy is in the form of neutrinos.

Fusion reactions in the Sun have ceased within the past few minutes.
Explanation: If the Sun suddenly stopped emitting neutrinos, we might infer that the Sun had undergone a sudden change in its composition or structure.

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
Explanation: Sunspots appear dark in pictures of the Sun because they are cooler than the surrounding area. The Sun is so bright that when an area is cooler, it appears darker.

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
Explanation: The chromosphere and corona are best observed using special instruments called coronagraphs and spectrographs. These instruments block out the bright light from the Sun's surface, allowing the much fainter light from the chromosphere and corona to be seen.

extremely hot plasma flowing along magnetic field lines
Explanation: The intricate patterns visible in an X-ray image of the Sun generally show areas of high and low density. The high density areas are typically where the Sun's magnetic field is strongest, and the low density areas are typically where the Sun's magnetic field is weakest.

By looking for the splitting of spectral lines in the Sun's spectrum
Explanation: There are a few ways to measure the strength of magnetic fields on the Sun. One way is to use a magnetometer, which is a device that measures the strength of a magnetic field. Another way is to use the Zeeman effect, which is a way to measure the strength of a magnetic field by looking at how it affects the light coming from an object.

Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
Explanation: Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because the increased solar activity during this time can cause more space debris, which can then collide with and damage satellites.

We can send a space probe into the Sun's photosphere.
Explanation: There are four main ways that we can study the inside of the Sun: through helioseismology, through studying solar neutrinos, through studying the solar wind, and through studying the Sun's magnetic field. Of these, helioseismology is the only one that can directly probe the interior of the Sun. The other three methods can only indirectly infer information about the Sun's interior.

Neutrinos rarely, if ever, interact with your computer.
Explanation: A solar neutrino shield is not a real thing and would not protect your computer from anything. The salesman is likely trying to take advantage of you and your lack of knowledge on the subject.