This topic contains a solution. Click here to go to the answer

Author Question: Explain the reasoning that leads astronomers to believe that our galaxy is surrounded by a cloud of ... (Read 52 times)

laurencescou

  • Hero Member
  • *****
  • Posts: 593
Explain the reasoning that leads astronomers to believe that our galaxy is surrounded by a cloud of dark matter.
 
  What will be an ideal response?

Question 2

Explain why the spring and neap tides occur periodically.
 
  What will be an ideal response?



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
Marked as best answer by a Subject Expert

asdfghjkl;

  • Sr. Member
  • ****
  • Posts: 323
Answer to Question 1

Stars rotate around the galactic center in ways that are controlled by the way the mass of the galaxy is distributed. A star that has distributed matter inside and outside of its orbit will orbit according to one principle, a star that is orbiting outside of the mass will follow another (Keplerian) principal.
We observe that the orbital periods of stars follows the pattern of an orbit inside of a distributed mass, rather than changing to a Keplerian orbit pattern after crossing the boundary of visible matter. This means that there must be mass outside of the visible region of the galaxy. This mass does not emit or absorb photons of electromagnetic energy, so it is termed dark.

Answer to Question 2

Gravity is universal, so the Sun also produces tides on Earth. The Sun is 27 million times more massive than the Moon, but it lies almost 400 times farther from Earth. Tides on Earth caused by the Sun are less than half as high as those caused by the Moon. Twice a month, at new moon and at full moon, the Moon and Sun produce tidal bulges that add together and produce extreme tidal changes: At those moon phases, high tides are exceptionally high, and low tides are exceptionally low. Such tides are called spring tides. Here the word spring does not refer to the season of the year but to the rapid rising up of water. At first- and third-quarter moons, the Sun and Moon pull at right angles to each other, and the tides caused by the Sun partly cancel out the tides caused by the Moon. These less extreme tides are called neap tides, and they do not rise very high or fall very low.




laurencescou

  • Member
  • Posts: 593
Reply 2 on: Jul 27, 2018
Thanks for the timely response, appreciate it


marict

  • Member
  • Posts: 304
Reply 3 on: Yesterday
Great answer, keep it coming :)

 

Did you know?

Stevens-Johnson syndrome and Toxic Epidermal Necrolysis syndrome are life-threatening reactions that can result in death. Complications include permanent blindness, dry-eye syndrome, lung damage, photophobia, asthma, chronic obstructive pulmonary disease, permanent loss of nail beds, scarring of mucous membranes, arthritis, and chronic fatigue syndrome. Many patients' pores scar shut, causing them to retain heat.

Did you know?

More than 150,000 Americans killed by cardiovascular disease are younger than the age of 65 years.

Did you know?

The longest a person has survived after a heart transplant is 24 years.

Did you know?

Serum cholesterol testing in adults is recommended every 1 to 5 years. People with diabetes and a family history of high cholesterol should be tested even more frequently.

Did you know?

According to the American College of Allergy, Asthma & Immunology, more than 50 million Americans have some kind of food allergy. Food allergies affect between 4 and 6% of children, and 4% of adults, according to the CDC. The most common food allergies include shellfish, peanuts, walnuts, fish, eggs, milk, and soy.

For a complete list of videos, visit our video library