Biology Exam - 6
Correct Answer both B and D
How do we know what goes on under the surface of the Sun? We have sent probes below the surface of the Sun. Astronomers create mathematical models that use the laws of physics, the Sun's observed composition and mass, and computers to predict internal conditions. We have X-ray images from satellites of the interior of the Sun. By measuring Doppler shifts, we observe vibrations of the Sun's surface that are created deep within the Sun. Correct Answer both B and D
half-life
In radioactive dating, the measure scientists use to note how long (on average) a particular radioactive nucleus will take to decay is called its: radioactive ratio parent-daughter criterion half-life geological activity Tinder activity
4 billion years
According to modern science, approximately how old is the Sun? 25 million years 10,000 years 4 billion years 400 million years
revolve around the Sun in the same direction
All the planets (without exception) have solid surfaces have atmospheres much thicker than Earth's have satellites orbiting around them revolve around the Sun in the same direction rotate on their axes in the same direction that they revolve around the Sun
True
Although the Sun does not generate energy by gravitational contraction today, this energy-generation mechanism was important when the Sun was forming. True False
green
Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun's surface? orange yellow blue green red
causing huge cyclones around the equator of the Earth
Coronal Mass Ejections from the Sun have many serious effects on or near the Earth. Which of the following is NOT one of these effects? disrupting the electronics of satellites heating the ionosphere and thus expanding the extent of our planet's atmosphere causing power surges and power outages in parts of the Earth near the poles causing huge cyclones around the equator of the Earth exposing astronauts and airplane passengers to increased amounts of radiation
heavier materials sink to the centers of molten planets
During the process of differentiation, satellites separate from the parent planets and go into their own orbits the faster planets move further out from the Sun heavier materials sink to the centers of molten planets the atmosphere of a planet changes from oxidized to reduced the surface of a planet changes to resemble Bayonne, New Jersey
the solar nebula
Our best evidence and theoretical calculations indicate that the solar system began with a giant spinning system of gas and dust that scientists call: the Titius-Bode cloud the solar nebula a planetesimal the asteroid belt he beltway
about 4.5 billion years
Radioactive dating techniques have revealed that our Earth and Moon are approximately how old? about 6,000 years about 2 million years about 100 million years about 4.5 billion years
False
The Sun generates energy primarily by nuclear fission. True False
False
The Sun is a ball of gas that is on fire. True False
False
The Sun is a relatively young star, near the beginning of its life. True False
5 billion years.
The Sun will exhaust its nuclear fuel in about 5 billion years. 5000 AD. 50 billion years. 5 million years.
True
The Sun's rate of fusion is gradually increasing over time. True False
photosphere
The Sun's surface, as we see it with our eyes, is called the core. corona. photosphere. chromosphere.
False
The chromosphere is the layer of the Sun that we see as its visible surface. True False
nuclear fusion of hydrogen into helium.
The fundamental nuclear reaction occurring in the core of the Sun is radioactive decay. nuclear fusion of hydrogen into helium. nuclear fusion of helium to carbon. nuclear fission.
it was so hot where the inner planets formed that the lighter materials evaporated
The inner planets are made mostly of rock and metal because: lighter materials cannot orbit the Sun; they would fall in immediately the Sun is made mostly of rock and metal and the inner planets are closest to the Sun it was so hot where the inner planets formed that the lighter materials evaporated
hundreds of thousands of years ago.
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about a thousand years ago. hundreds of thousands of years ago. tens of thousands of years ago. a hundred years ago. a million years ago.
a few hundred thousand years ago.
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about one thousand years ago a few hundred thousand years ago. one hundred years ago. three days ago.
planetesimals
The material that would eventually make all the major bodies in our solar system first gathered together as smaller pieces which astronomers call: planetesimals nebuloids satellites differentiated objects jovians
the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.
The proton-proton chain is an alternative way of generating energy that is different from the fusion of hydrogen into helium. the linkage of numerous protons into long chains. another name for the force that holds protons together in atomic nuclei. the specific set of nuclear reactions through which the Sun fuses hydrogen into helium.
only on internal processes within the atoms; nothing external matters
The rate at which a collection of the same radioactive atoms will decay depends on: the amount of radio waves falling on the material the amount of light falling on the material the temperature of the material the size of the planet or moon on which the material is located only on internal processes within the atoms; nothing external matters
Comets
The smaller objects in the solar system composed mainly of ices (frozen gases) that usually orbit far from the Sun are called: snowroids comets asteroids satellites jovians
nuclear fusion.
The source of energy that keeps the Sun shining today is gravitational contraction. nuclear fission. nuclear fusion. chemical reactions.
Oxidized
Today, the chemistry of the terrestrial planets does not include a lot of free hydrogen. Chemists call the chemistry in places like the Earth: reduced expanded silicate oxidized comet-like
70% hydrogen, 28% helium, 2% other elements
What is the Sun made of (by mass)? 50% hydrogen, 25% helium, 25% other elements 70% hydrogen, 28% helium, 2% other elements 90% dark matter, 10% ordinary matter 100% hydrogen and helium
70 percent hydrogen, 28 percent helium, 2 percent other elements
What is the Sun made of? 50 percent hydrogen, 25 percent helium, 25 percent other elements 98 percent hydrogen, 2 percent helium and other elements 70 percent hydrogen, 28 percent helium, 2 percent other elements 100 percent hydrogen and helium 70 percent helium, 28 percent hydrogen, 2 percent other elements
10 million K
Which is closest to the temperature of the core of the Sun? 1 million K 10,000 K 10 million K 100,000 K 100 million K
photosphere
Which layer of the Sun do we normally see? corona photosphere radiation zone chromosphere convection zone
granulation
Which of the following is not part of some active regions on the Sun? sunspots flares plages prominences granulation
False
Energy from the core of the Sun first travels slowly through the convection zone and then much faster through the radiation zone. True False
core, radiation zone, convection zone, photosphere, chromosphere, corona
From center outward, which of the following lists the "layers" of the Sun in the correct order? core, radiation zone, convection zone, corona, chromosphere, photosphere core, corona, radiation zone, convection zone, photosphere, chromosphere core, radiation zone, convection zone, photosphere, chromosphere, corona core, convection zone, radiation zone, corona, chromosphere, photosphere
hotter and denser than the surface.
The core of the Sun is composed of iron. constantly rising to the surface through convection. at the same temperature and density as the surface. at the same temperature but denser than the surface. hotter and denser than the surface.
False
The core of the Sun is at a temperature of about 20,000 K. True False
True
The corona and chromosphere are hotter than the photosphere. True False
4 H ⇒ 1 He + energy.
The overall fusion reaction by which the Sun currently produces energy is 3 He ⇒ 1 C + energy. 4 H ⇒ 1 He + energy. 4 H ⇒ 4 He + energy. 6 H ⇒ 1 He + energy. 3 H ⇒ 1 Li + energy.
4 H becomes 1 He + energy.
The overall result of the proton-proton chain is p + p becomes 2H + energy. 4 H becomes 1 He + energy. 6 H becomes 1 He + energy. Individual protons are joined into long chains of protons.
plasma
The phase of matter in the Sun is solid. liquid. plasma. gas. a mixture of all of the above
Mercury
The planet closest to the Sun in the solar system is: Mercury Pluto Venus Neptune
use computer models to predict interior conditions.
To estimate the central temperature of the Sun, scientists monitor changes in Earth's atmosphere. send probes to measure the temperature. use hot gas to create a small Sun in a laboratory. use computer models to predict interior conditions.
The moons of Neptune
A future interplanetary tourist whose parents kept him too warm as a baby asks for your help to find a "really cold place" in the solar system. Which of the following would be the coldest place to take him? the Earth's polar regions The moons of Neptune e moons of Mars (which are captured asteroids) Halley's Comet when it is closest to the Earth in its orbit the deep atmosphere of Jupiter
Jupiter
A planet in our solar system whose composition resembles that of our Sun is: Earth Mercury Jupiter Pluto
is made entirely of hot gas
As astronomers have learned more about the structure of the Sun, they have found that it has a small solid core inside is made entirely of liquid, with a tiny bit of hot gas on the outside is solid throughout, but with a large very hot atmosphere is made entirely of hot gas is made of billions of individual pieces of hot rock, all orbiting around each other in a whirling arrangement
all of the above
Astronomers have found that the level of the Sun's activity varies over the centuries. How did they come to realize that this is so: historical records of the number of sunspots seen on the Sun measuring the amount of radioactive carbon in tree rings historical records of auroral activity all of the above
helium, energy, and neutrinos.
At the center of the Sun, fusion converts hydrogen into helium, energy, and neutrinos. radioactive elements like uranium and plutonium. plasma. radiation and elements like carbon and nitrogen. hydrogen compounds.
core, radiation zone, convection zone, photosphere, chromosphere, corona
From the center outward, which of the following lists the "layers" of the Sun in the correct order? core, radiation zone, convection zone, corona, chromosphere, photosphere core, radiation zone, convection zone, photosphere, chromosphere, corona core, convection zone, radiation zone, photosphere, chromosphere, corona core, convection zone, radiation zone, corona, chromosphere, photosphere core, corona, radiation zone, convection zone, photosphere, chromosphere
nuclear fusion
How does the Sun generate energy today? chemical reactions gravitational contraction nuclear fission gradually expanding in size nuclear fusion
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
How is the sunspot cycle directly relevant to us here on Earth? The sunspot cycle strongly influences Earth's weather. The sunspot cycle is the cause of global warming. The Sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on Earth. Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
4 million tons
How much mass does the Sun lose through nuclear fusion per second? 600 million tons 600 tons 4 tons 4 million tons Nothing: mass is conserved.
solar neutrinos
Humans have not sent a spacecraft into the interior of the Sun to confirm any models of the interior. What evidence then do we have to support our current ideas about the solar interior? solar flares sun spots solar neutrinos X-ray observations that penetrate the gas We have no evidence, just informed guesses.
millions of degrees.
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of trillions of degrees. billions of degrees. millions of degrees. thousands of degrees. any temperature, as long as gravity is strong enough.
Hydrogen
If you were to take a large sample of the four giant planets, the most common element you would find in them is: iron hydrogen oxygen silicon
just a little after 2 hrs
In a bad late-night science fiction film, a villain is using a large collection of rare radioactive atoms as energy for a weapon to threaten the good guys. The atoms have a half-life of 1 hour. The villain has 4 kilograms of the radioactive material now, and he needs a minimum of 1 kg. for his weapon to work. After how much time will the weapon no longer be a threat? just a little after 1 hr just a little after 2 hrs just a little after 4 hours just a little after 16 hours
its atmosphere (whether it has one and how thick it is)
In general, the further planets are from the Sun, the cooler they are. What other factor can have a significant influence on a planet's surface temperature? its atmosphere (whether it has one and how thick it is) the number of large moons that are close to the planet how fast the planet is spinning (the length of its day) whether its core has a lot of iron in it
is roughly proportional to the age of the surface we are examining
In studying the surfaces of solid bodies in the solar system, astronomers have learned that the number of craters (per unit area): is about the same on every world greater as you get closer to the Sun s greater as you get further and further from the Sun is roughly proportional to the age of the surface we are examining follows no discernible rules or relationships at all
the four terrestrial planets must once have been hot enough to be molten (like a liquid)
In the four terrestrial planets, the densest, heaviest materials are at the center and not evenly distributed throughout the planet. Scientists interpret this observation to mean that: the four terrestrial planets must once have been inside the Sun the four terrestrial planets must once have been hot enough to be molten (like a liquid) the four terrestrial planets must have formed where Jupiter and Saturn now are the four terrestrial planets must have collided with each other many times
The chromosphere is the source of ultraviolet light, and the corona is the source of X-rays.
Most of the energy produced in the Sun is released in the form of visible light from the photosphere. However, some energy is released from the upper layers of the solar atmosphere. Which of the following best describes where other forms of light are released? The chromosphere is the source of X-rays, and the corona is the source of radio waves. Radio waves can pass directly through the gas which allows us to see the core. The chromosphere is the source of infrared light, and the corona is the source of ultraviolet light. The chromosphere is the source of ultraviolet light, and the corona is the source of X-rays.
False
Nuclear power plants on Earth create energy in the same way as the Sun. True False
Venus
Of the following planets, which do NOT have satellites (moons)? Mars Venus Earth Jupiter you can't fool me, all the planets have satellites
The Moon
On Earth, we can get the age of various parts of our planet by finding rocks that contain radioactive atoms. Which other world do have a good number of rocks from to do this kind of age analysis? Venus The Moon Halley's Comet Jupiter
you can't fool me; there is no other planet on which we could survive unprotected
On which of the planets (other than Earth) could a human being step out of a spacecraft and survive without any protective gear (special suit, oxygen tanks, etc)? Venus Mars Jupiter Neptune you can't fool me; there is no other planet on which we could survive unprotected
Venus
On which planet (besides the Earth) do we still see a high level of geological activity on the surface today? Jupiter Mercury Neptune Venus none of the above
finding circumstellar disks of material around nearby stars
One piece of evidence that can help astronomers sort out how the planets in our solar system formed is discovering other galaxies of stars beyond the Milky Way counting the number of moons around each planet in our own solar system finding circumstellar disks of material around nearby stars counting the craters on the surface of Jupiter, Saturn, Uranus, and Neptune suring variations in the amount of snowfall in northern Canada during this century
True
Sunspots are cooler than the surrounding region of the Sun's surface. True False
strong magnetic fields slow convection and prevent hot plasma from entering the region.
Sunspots are cooler than the surrounding solar surface because magnetic fields lift material from the surface of the Sun, cooling off the material faster. magnetic fields trap ionized gases that absorb light. there is less fusion occurring there. they are regions where convection carries cooler material downward. strong magnetic fields slow convection and prevent hot plasma from entering the region.
Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal.
Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen? Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal. The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size. Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal. Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star.
5,800 K.
The Sun's average surface (photosphere) temperature is about 37,000 K. 5,800 K. 1,000,000 K. 1,000 K
areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind
What are coronal holes? regions on the photosphere where magnetic lines poke through, creating the cooler areas of the sunspots holes in the corona of the Sun that allow us to see the photosphere areas of the corona where magnetic field lines project into space, allowing charged particles to escape the Sun, becoming part of the solar wind tunnels in the outer layers of the Sun through which photons can escape more quickly than through the radiation zone all of the above
watts
What are the appropriate units for the Sun's luminosity? Newtons kilograms watts meters joules
watts
What are the appropriate units for the Sun's luminosity? kilograms watts joules Newtons
They are all strongly influenced by magnetic fields on the Sun.
What do sunspots, solar prominences, and solar flares all have in common? They all occur only in the Sun's photosphere. They are all shaped by the solar wind. They are all strongly influenced by magnetic fields on the Sun. They all have about the same temperature.
Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
What happens to energy in the Sun's convection zone? Energy is produced in the convection zone by thermal radiation. Energy is produced in the convection zone by nuclear fusion. Energy is transported outward by the rising of hot plasma and sinking of cooler plasma. Energy slowly leaks outward through the radiative diffusion of photons that repeatedly bounce off ions and electrons.
Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
What happens to energy in the convection zone of the Sun? Energy is conserved so while the gas moves up and down, there is no net transport of energy. Energy is consumed in the convection zone by the creation of electrons and positrons. Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma. Energy slowly leaks outward through the diffusion of photons that repeatedly bounce off ions and electrons. Energy is produced in the convection zone by nuclear fusion.
the bubbling pattern on the photosphere produced by the underlying convection
What is granulation in the Sun? another name for the way sunspots look on the surface of the Sun dust particles in the Sun that haven't been turned into plasma elements in the Sun other than hydrogen and helium lumps of denser material in the Sun the bubbling pattern on the photosphere produced by the underlying convection
counting craters
What is one way that astronomers have actually gotten an idea of the age of the surfaces of terrestrial planets other than the Earth? looking at the colors different surfaces show bringing back samples and run radioactive dating tests counting craters measuring the thickness of the atmosphere above each surface looking in the instruction manual that comes with each planet
6,000 K
What is the average temperature of the surface of the Sun? 10,000 K 6,000 K 1 million K 100,000 K 1,000 K
Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath
What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker? Sunspots are holes (less dense regions) in the Sun's photosphere, through which we can see the darker regions of the Sun below Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath Sunspots are regions where carbon clouds high above the photosphere gather and these dark clouds block the light from underneath them Sunspots are regions in the upper chromosphere where there is a lot of coronium, which absorbs light Sunspots are so mysterious and difficult to explain, astronomers really don't have idea what causes them
we have been able to send spacecraft to gather information about planets and moons up close
What is the most important reason that astronomers have learned more about our planetary system in the last 30-40 years than all of history before then. astronomers today are a lot smarter than astronomers were earlier the Hubble Space Telescope we have been able to send spacecraft to gather information about planets and moons up close radio telescope arrays allow astronomers to make out details on the planets that they have never been able to see before the planets (moving in their slow orbits around the Sun) happen to be closer to the Earth in the last 30 years than at any previous time in human history
a stream of charged particles flowing outward from the surface of the Sun
What is the solar wind? a stream of charged particles flowing outward from the surface of the Sun the strong wind that blows sunspots around on the surface of the Sun the uppermost layer of the Sun, lying just above the corona the wind that causes huge arcs of gas to rise above the Sun's surface
We see many sunspots on the surface of the Sun.
What observations characterize solar maximum? The Sun rotates faster at the equator. The Sun becomes much brighter. The Sun emits light of longer average wavelength. We see many sunspots on the surface of the Sun. all of the above
the winding of magnetic field lines due to differential rotation
What processes are involved in the sunspot cycle? variations of the solar thermostat wave motions in the solar interior the winding of magnetic field lines due to differential rotation the interaction of the Earth's magnetic field with that of the Sun gravitational contraction of the Sun
outward pressure and inward gravity
What two forces are balanced in what we call gravitational equilibrium? outward pressure and inward gravity the strong force and gravity the strong force and kinetic energy the electromagnetic force and gravity outward pressure and the strong force
the inward pull of gravity and outward pressure
What two physical processes balance each other to create the condition known as gravitational equilibriumin stars? the inward pull of gravity and surface tension the strong force and the electromagnetic force the strong force and the weak force the inward pull of gravity and outward pressure
when the Sun was being formed from a collapsing cloud of gas
When is/was gravitational contraction an important energy-generation mechanism for the Sun? when the Sun was being formed from a collapsing cloud of gas only during solar maximum right after the Sun began fusing hydrogen in its core when the Sun transports radiation through the convection zone only during solar minimum
the Sun consists of gas in which many or most of the atoms are ionized (missing electrons).
When we say that the Sun is a ball of plasma, we mean that the Sun consists of gas in which many or most of the atoms are ionized (missing electrons). the Sun is roughly the same color as blood. the Sun is made of material that acts like a liquid acts on Earth. the Sun is made of atoms and molecules.
When a star contracts in size, gravitational potential energy is converted to thermal energy.
Which of the following correctly describes how the process of gravitational contraction can make a star hot? Heat is generated when gravity contracts, because gravity is an inverse square law force. Gravitational contraction involves nuclear fusion, which generates a lot of heat. When a star contracts in size, gravitational potential energy is converted to thermal energy. Gravitational contraction involves the generation of heat by chemical reactions, much like the burning of coal.
Jupiter
Which of the following is NOT a terrestrial planet? Mars Earth Jupiter Venus Mercury
The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
Which of the following is not a characteristic of the 11-year sunspot cycle? The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle. The Sun's entire magnetic field flip-flops at the end of each cycle (at solar minimum). The number of sunspots on the Sun at any one time gradually rises and falls, with an average of 11 years between the times when sunspots are most numerous. the likelihood of seeing solar prominences or solar flares is higher when sunspots are more common and lower when they are less common.
a small asteroid
Which of the following places is most likely NOT to be differentiated? a small asteroid Earth Jupiter Venus, because it is so hot Ganymede, the largest satellite in the solar system
The rate of nuclear fusion in the Sun peaks about every 11 years.
Which of the following statements about the sunspot cycle is not true? The rate of nuclear fusion in the Sun peaks about every 11 years. The number of sunspots peaks approximately every 11 years. With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak. The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle. The number of solar flares peaks about every 11 years.
astronomers think that flares are connected with sudden changes in the magnetic field of the Sun
Which of the following statements about the violent events on the Sun called flares is FALSE? flares happen more often during solar maximum, and sometimes during those periods, there can be several in one day a flare can release energy equivalent to a million hydrogen bombs flares originate in the upper part of the corona, in the regions called coronal holes astronomers think that flares are connected with sudden changes in the magnetic field of the Sun the visible light we see from a flare is only a tiny fraction of the energy it releases
jovians (being larger) rotate significantly more slowly than terrestrials
Which of the following ways that jovian (giant) planets differ from the terrestrial planets is NOT CORRECT? jovians have more mass than the terrestrials jovians are further from the Sun than terrestrials jovians are made of lighter elements on average than terrestrials jovians have rings while terrestrials do not jovians (being larger) rotate significantly more slowly than terrestrials
you can't fool me, spacecraft have visited all the planets in our solar system
Which planet in the solar system has not been examined by spacecraft instruments that have either flown by or orbited them? Earth Neptune Venus Saturn you can't fool me, spacecraft have visited all the planets in our solar system
The Sun rotates at different rates at different latitudes on the Sun
Which statement about the Sun's rotation is TRUE? The Sun does not rotate; only planets rotate The Sun rotates once a day The Sun rotates at different rates at different latitudes on the Sun The Sun rotates only at the equator, where the sunspots are found; the rest of the Sun does not rotate Only the atmosphere of the Sun rotates, not the main body of the Sun
They have a tendency to pass through just about any material without any interactions.
Why are neutrinos so difficult to detect? They have a tendency to pass through just about any material without any interactions. They have no mass. They are extremely rare. No one knows: this is the essence of the "solar neutrino problem."
They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun.
Why do sunspots appear dark in pictures of the Sun? They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun. They emit light in other wavelengths that we can't see. They are too cold to emit any visible light. They are tiny black holes, absorbing all light that hits them. They are holes in the solar surface through which we can see to deeper, darker layers of the Sun.
Fusion reactions decrease the overall number of particles in the core, causing the core to shrink, converting gravitational potential energy into thermal energy, and increasing the rate of fusion.
Why must the Sun's rate of fusion gradually rise over billions of years? The rate of fusion is not rising; it is actually decreasing over time. Fusion reactions decrease the overall number of particles in the core, causing the core to shrink, converting gravitational potential energy into thermal energy, and increasing the rate of fusion. The Sun gets heavier as it gets older, and the stronger inward pull of gravity increases the fusion rate. The Sun becomes less efficient and must increase the rate of fusion to produce the same amount of energy.
Mercury
You are the captain of an interplanetary tour ship and a wealthy tourist from Texas asks you to take him to see only the "largest darn planets" in the solar system. Which of the following would you NOT include in your tour? Mercury Jupiter Saturn Neptune Uranus
