Water is distributed on Earth through the never-ending water cycle. The heat from the Sun keeps the water cycling through the various stages. The Sun heats water into a vapor, which later cools and forms into the billions of droplets that make up clouds. The moisture in clouds falls back to Earth as rain, snow, hail, or sleet. The water that falls back to Earth can be absorbed into the ground or fill lakes, ponds, oceans, and other bodies of water. The topography of the land affects the amount of precipitation that the area receives. Each site has variations in elevation, and the Earth is shaped differently, which changes the amount and type of precipitation. The process of the water cycle continues with no beginning or end, and it does not have to follow the stages in a specific order or pattern.

What is the term for the stage in the water cycle where the water cools and forms droplets?

True or False: Water can be found on Earth in three different states of matter.

Which stages of the water cycle add water directly to the oceans?

Water is distributed on Earth through the never-ending water cycle. The heat from the Sun keeps the water cycling through the various stages. The Sun heats water into a vapor, which later cools and forms into the billions of droplets that make up clouds. The moisture in clouds falls back to Earth as rain, snow, hail, or sleet. The water that falls back to Earth can be absorbed into the ground or fill lakes, ponds, oceans, and other bodies of water. The topography of the land affects the amount of precipitation that the area receives. Each site has variations in elevation, and the Earth is shaped differently, which changes the amount and type of precipitation. The process of the water cycle continues with no beginning or end, and it does not have to follow the stages in a specific order or pattern.

What is the term for the stage of the water cycle where water is heated by the Sun and turns into a vapor?

Mrs. Johnson's class is investigating the brightness of stars. Mrs. Johnson sets up the investigation, and the students begin working. The first two student volunteers held identical flashlights at an equal distance from the whiteboard. The class decides after noting the lights on the board look the same that when two stars are at an equal distance, they have the same actual brightness. For the second part of the investigation, two student volunteers held the identical flashlights at two different distances. Students observed than the flashlight that is closer to the whiteboard appears to be brighter than the flashlight that is further away from the whiteboard. Their observations are recorded in the data table below.

What inference can the students draw from this demonstration?

Four students are making claims about stars and their apparent brightness.

• Ursula: "The star that appears brightest to us is the Sun because it is the largest in the galaxy."
• Gretel: "The Sun appears to be the brightest star because it is the closest to Earth."
• Hansel: "The Sun is the brightest star when looking from Earth because it is the hottest."
• Phoebe: "I have seen brighter stars than the Sun; it isn't that great."

Their teacher shares the following information from NASA, "Of course, the star that appears the brightest to all of us on Earth is the Sun. Although it is a rather typical star, not all that different from many of the ones you see at night, we live so close to it that it outshines everything else. Even the next closest star is more than a quarter of a million times farther from Earth, so it is not surprising that the light from the Sun overwhelms that from other stars."

Which student's argument is supported by the teacher's research?

Source: https://spaceplace.nasa.gov/review/dr-marc-space/brightest-star.html

NASA gives background information on the brightness of stars, "To find out the true brightness of a star; scientists need to know how far it is. Although there are some very clever ways of gauging the distances to stars, they generally work well only for stars that are in the Sun's neighborhood of the Milky Way galaxy. The more distant stars are just so fantastically far from us that measuring their distances accurately is too difficult. Making it still harder to know how bright a star is, there is a kind of patchy fog between the stars - space is not truly empty. Although it is not the same as the fog on Earth, gas and dust in space can dim the light of stars. Without a good way to know how much of this interstellar fog is blocking the light, there is no reliable way to discover the true brightness of a star."

Which piece of text evidence supports the claim that it is possible to measure the actual brightness of stars?

Source: https://spaceplace.nasa.gov/review/dr-marc-space/brightest-star.html

Dot makes a statement to her teacher. "The Sun is the brightest star in the galaxy and no other star can compare." She provides this evidence from NASA to support her argument, "Although we don't know which star truly is the brightest, we know some are remarkably bright. You can see one of them any clear night this summer. Deneb is northeastern of the three stars that form a large and easily seen grouping called the Summer Triangle. While Deneb shines the brightest in the constellation Cygnus, 17 other stars glow brighter in our night skies. But Deneb is much farther from Earth than most of the other stars you see, and this giant is around 100,000 times brighter than the Sun. If Deneb were the same distance from Earth as Vega, another star in the Summer Triangle, not only would it outshine all the stars and planets visible at night, but it would even be bright enough to see in the daytime!"

Dot's argument and evidence are in sync.

Source: https://spaceplace.nasa.gov/review/dr-marc-space/brightest-star.html

"To find out the true brightness of a star, scientists need to know how far it is. Although there are some very clever ways of gauging the distances to stars, they generally work well only for stars that are in the Sun's neighborhood of the Milky Way galaxy. The more distant stars are just so fantastically far from us that measuring their distances accurately is too difficult. Making it still harder to know how bright a star is, there is a kind of patchy fog between the stars - space is not truly empty. Although it is not the same as the fog on Earth, gas and dust in space can dim the light of stars. Without a good way to know how much of this interstellar fog is blocking the light, there is no reliable way to discover the true brightness of a star." - NASA

Which piece of evidence from NASA's passage describes a complication with measuring a star's actual brightness?

Source: https://spaceplace.nasa.gov/review/dr-marc-space/brightest-star.html

Besides the Sun, all other stars appear to be pin-pricks of light. Why do the other stars appear so small?