Answer:
The astronomical model created and published by Nicholas Copernicus in the year 1543 is called Copernican heliocentrism. The model set the Sun in immobile position near the center of the solar system with Earth, as well as the other planets, spherical, epicycled and at consistent frequencies around it.
By the admiring tone that the writer has for the gift that she/he received, it is clear that there's a lot of imagery. The writer also described the rose as "perfect", "scented dew still wet", and "pure", which further supports the idea that he/she is describing the gift.
We would have to search at least 5,000,000,000 (5 billion) stars before we would expect to hear a signal.
To find out the number of stars that we will need to search to find a signal, we need to use the following formula:
- total of stars/civilizations
- 500,000,000,000 (500 billion) stars / 100 civilization = 5,000,000,000 (5 billion)
This shows it is expected to find a civilization every 5 billion stars, and therefore it is necessary to search at least 5 billion stars before hearing a signal from any civilization.
Note: This question is incomplete; here is the complete question.
On average, how many stars would we have to search before we would expect to hear a signal? Assume there are 500 billion stars in the galaxy.
Assuming 100 civilizations existed.
Learn more about stars in: brainly.com/question/2166533
Answer:

Explanation:
h = Planck's constant = 
c = Speed of light = 
E = Energy = 
Wavelength ejected is given by

The maximum wavelength in angstroms of the radiation that will eject electrons from the metal is 
Answer:
reflection is the act of reflecting or the state of being reflected while echo is
reflection of sound waves from a surface back to the initial listener