The Sun, Moon, and stars have helped
people for thousands of years. When you look
into the sky, you will notice that they follow
certain patterns. This happens most of the
time, but not all of the time. Since most
patterns repeat over and over, they have
helped us keep track of time. These patterns
have also helped us make calendars.
Making calendars was a difficult task. Our ancestors had to decide on the length of a year.
Also, they had to decide on the length of a day. As you know a day takes 24
hours. That is the time that Earth takes to rotate once on its axis. A year is longer and
takes 365 days. This length of time is related to the time that it takes for Earth to go
around the Sun. However, this is not exactly true. Earth’s trip takes 365 days – plus a
fraction of another day. This is what complicates our calendar. We have been able to
solve this problem by adding an extra day in the month of February. Most often, you will
see that February has 28 days. Every four years, February has one extra day. During this
year we end up with 29 days in this month. When this happens, the year is called a Leap
Year. It helps us keep our calendar in order.
Deciding on the length of a month has also been a challenge. Some cultures around the
world have used a lunar calendar. A lunar calendar is based on the Moon’s cycle. The
Moon takes 29 and one-half days to complete one cycle. Then things got a lot harder.
Different cultures start their months at a different time of the Moon’s cycle. For example,
the Hebrew and Islamic calendars start their months when a crescent moon is seen in the
sky. The Chinese start their new months at the new moon phase. These differences have
made it harder for cultures to communicate. Trading with one another has also been hard
for this reason.
As time went by, most countries began to use the same calendar. When this happened in
the twentieth century, trade and communication became a lot easier. Some countries
decided to drop thirteen days from their calendar. This is because their old way of
counting did not match up with the new way.
England had problems with the calendar back in the 1500s. The English decided to divide
their calendar into months. Each month had four weeks. By doing this, one week ended
up being longer than seven days. Also, this resulted in thirteen months to a yea
Answer:
Ligands
Explanation:
Ligands are small molecules that transmit signals in between or within cells. Ligands exert their effects by binding to cellular proteins called receptors.
There are 1.2 moles of KBr found in 3 Liters of 0.4 M solution.
<h3>HOW TO CALCULATE NUMBER OF MOLES?</h3>
The number of moles of a substance can be calculated by multiplying the molarity by the volume.
No. of moles = Molarity × volume
According to this question, 3L of a KBr solution are contained in a 0.4M.
no. of moles = 3L × 0.4M = 1.2moles
Therefore, there are 1.2 moles of KBr found in 3 Liters of 0.4 M solution.
Learn more about no. of moles at: brainly.com/question/14919968
In, 1937 Lawrence, in operating his cyclotron, bombarded a molybdenum-96 foil with deuterium ions (2h), producing for the first time an element not found in nature. He was initially unaware that the radioactivity produced by the "bombarded foil" was not from molybdenum but from a new, artificial element. It was his cooperation with Italian-American physicist <span>Emilio Segrè </span>that allowed the new element to be discovered. The answer is Technetium: Tc
Answer:
Reliability. When a scientist repeats an experiment with a different group of people or a different batch of the same chemicals and gets very similar results then those results are said to be reliable. Reliability is measured by a percentage – if you get exactly the same results every time then they are 100% reliable.
Explanation:
Sorry, I only got one way.
