Time Zones and the Coordinated Universal Time

Summary

This script explores the concept of time zones and Coordinated Universal Time (UTC). It explains how the Earth's rotation leads to different solar times based on longitude, with each degree equating to four minutes of time. The video clarifies how time zones, each 15 degrees wide, standardize time across regions, despite local solar time variations. It also discusses UTC as the global reference time, crucial for aviation and ensuring precise timekeeping across different time zones. The script concludes with the importance of sunrise and sunset times for aviation operations, highlighting the need for official tables published by civil aviation authorities.

Takeaways

• 🌞 Time is measured by the Earth's rotation, which takes approximately 24 hours to complete one full revolution, creating the concept of a day.
• 📍 Solar time is determined by the position of the sun in the sky relative to an observer's location, and it varies depending on longitude.
• 🌡 The Earth rotates 15 degrees per hour, equating to 4 minutes per degree and 4 seconds per minute of arc, which affects the calculation of time differences.
• 🕗 Time zones were established to standardize time within a specific region, with each time zone covering 15 degrees of longitude and differing by one hour from its neighbors.
• 🌐 The Coordinated Universal Time (UTC) is the international reference time used in air operations and corresponds to the local mean time of the prime meridian.
• 🔠 Naming time zones can be done by using the central meridian's degree, letters (excluding 'J'), or by their offset from UTC, such as UTC+5.
• 🌍 Large countries may span multiple time zones, leading to non-straight lines dividing time zones to accommodate political borders.
• ✈️ UTC is crucial for coordinating long flights that cross multiple time zones, ensuring everyone refers to the same exact time without needing conversions.
• 🌅 The time of sunrise and sunset is significant for aviation operations and is based on the actual solar time at a specific location, not just the local time zone.
• 📊 Civil aviation authorities publish official sunrise and sunset times for aerodromes, which vary throughout the year and affect the definition of day and night operations.
• 📚 Understanding time zones and solar time differences is essential for effective scheduling, coordination, and communication in aviation and other global operations.

Q & A

How is the passage of time measured on Earth?

The passage of time on Earth is measured by the movement of the sun in the sky, which is actually a result of the Earth's rotation around its own axis.

What is the period of time considered as a day?

A day is considered as the period of time it takes for the Earth to make one complete revolution around its own axis, which is approximately 24 hours.

Why does the current time of day vary depending on our position on Earth?

The current time of day varies because the sun always shines on one side of the Earth while the other side remains in darkness, creating different times of day based on our position relative to the sun.

What is solar time and how does it relate to an observer's position on Earth?

Solar time is the real time relative to the position of the sun and an observer on Earth's surface. It depends on the observer's longitude, as points on the same meridian will have the same solar time.

How is the difference in time between two points on Earth calculated based on their longitude?

The difference in time is calculated by determining the difference in longitude between the two points, then converting this difference into time using the fact that one degree of arc corresponds to four minutes of time.

Why was it necessary to create time zones?

Time zones were created to standardize time within a certain area and to solve the problem of having different local solar times for cities that are geographically close.

How many time zones are there on Earth and what determines their width?

There are 24 time zones on Earth, each 15 degrees wide, corresponding to the Earth's rotation of 360 degrees in 24 hours.

What is the term used for the standardized time within a time zone?

The standardized time within a time zone is known as local mean time, often abbreviated as LMT or simply LT.

What is the difference between Coordinated Universal Time (UTC) and local mean time?

Coordinated Universal Time (UTC) is an international time standard used as a reference, corresponding to the local mean time of the prime meridian, whereas local mean time is the standardized time within a specific time zone.

Why is UTC important in air operations and aviation?

UTC is important in air operations and aviation because it facilitates coordination and commerce, especially on long flights that cross multiple time zones, ensuring everyone is referring to the same exact time without needing to make conversions.

How do civil aviation authorities account for sunrise and sunset times at specific airports?

Civil aviation authorities publish official tables with sunrise and sunset times for each aerodrome throughout the year, taking into account the actual solar time at which these events occur.

Outlines

00:00

🌞 Understanding Solar Time and Time Zones

This paragraph introduces the concept of time measurement based on the Earth's rotation and the position of the sun in the sky. It explains how the Earth's 24-hour rotation creates the day-night cycle and how local solar time varies depending on an observer's longitude. The importance of the prime meridian and the method of calculating time differences based on degrees of longitude are discussed. The paragraph also illustrates how to determine the solar time for two cities, Miami and Berlin, by calculating the time difference resulting from their longitudinal separation.

05:01

🕰 Time Zone Standardization and UTC

The second paragraph delves into the establishment of time zones to standardize time across different regions, despite varying local solar times. It describes how the Earth is divided into 24 time zones, each covering 15 degrees of longitude, to simplify scheduling and coordination. The paragraph also explains the concept of local mean time (LMT) or local time (LT) and how it differs from actual solar time. Additionally, it introduces Coordinated Universal Time (UTC), also known as Greenwich Mean Time (GMT) or Zulu time, which serves as an international reference for air operations and other applications requiring precise timekeeping.

10:02

✈️ Aviation and the Importance of Solar Time

The final paragraph focuses on the relevance of solar time in aviation, particularly for determining operational boundaries between day and night. It emphasizes the need for civil aviation authorities to publish official sunrise and sunset times for aerodromes, which are essential for flight planning and safety. The paragraph highlights the variability of these times throughout the year and the importance of using local time zones as a reference while also considering the actual solar events for specific locations.

Keywords

💡Time Zones

Time zones are regions of the Earth that observe the same standard time due to their longitudinal position. They are a way to standardize time across the globe, making coordination and communication more efficient. In the script, time zones are explained as being 15 degrees wide each, corresponding to one hour difference from the next zone, which helps to maintain a uniform time within a geographical area despite the varying solar times.

💡Coordinated Universal Time (UTC)

Coordinated Universal Time, abbreviated as UTC, is the primary time standard used globally, and it is the basis for civil time and time zones worldwide. The script explains that UTC corresponds to the local mean time of the prime meridian and is used as a reference in air operations, ensuring a consistent time standard for international coordination.

💡Solar Time

Solar time is the time measured by the position of the sun in the sky, which varies depending on an observer's longitude on Earth. The script clarifies that solar time is the actual time relative to the sun's position, and it changes as the Earth rotates, with each meridian having its own solar time.

💡Meridian

A meridian, also known as a longitude line, is an imaginary line that runs from the North Pole to the South Pole, indicating a specific east-west position on the Earth's surface. The script uses meridians to explain how solar time is determined and how differences in longitude result in different local times.

💡Local Mean Time (LMT)

Local Mean Time is the average local time for a specific time zone, based on the solar time of its central meridian. The script mentions that LMT is adopted by all countries and territories within the same time zone, providing a standardized time that is not based on actual solar time.

💡Prime Meridian

The Prime Meridian is the meridian at 0 degrees longitude, which passes through the Royal Observatory in Greenwich, London. It serves as the reference point for time zones and UTC, as mentioned in the script, and is the starting point for measuring longitude east and west.

💡Sunrise and Sunset

Sunrise and sunset are the times when the sun appears to rise and set, respectively. The script discusses the importance of these times for aviation, as they determine the boundary between daytime and nighttime operations, and how they vary throughout the year at different locations.

💡Greenwich Mean Time (GMT)

Greenwich Mean Time is the mean solar time at the Prime Meridian, also known as Z time or Zulu time. The script explains that GMT is another term for the time kept at the Royal Observatory in Greenwich, which is essentially the same as UTC.

💡Aerodrome

An aerodrome is an airport or airfield used for flying activities. The script refers to aerodromes when discussing the importance of official sunrise and sunset times published by civil aviation authorities, which are crucial for航空 operations.

💡Zulu Time

Zulu Time is the time in the Z time zone, which is the same as UTC and GMT. The script uses 'Zulu' as a term for the time zone that corresponds to the Prime Meridian, emphasizing its use in aviation for clear and standardized timekeeping.

💡Rotation of the Earth

The rotation of the Earth refers to the planet's spinning around its own axis, which takes approximately 24 hours to complete one full turn. The script explains that this rotation is what creates the cycle of day and night and the concept of solar time, as different parts of the Earth face the sun at different times.

Highlights

Time on Earth is measured by the movement of the sun in the sky, which is actually due to the Earth's rotation around its axis.

A complete revolution of the Earth around its axis takes approximately 24 hours, which is considered a day.

The current time of day depends on one's position on Earth, with the sun always shining on one side while the other remains in darkness.

Solar time is the real time relative to the position of the sun and an observer on Earth's surface.

Points on the same meridian have the same solar time, which depends on longitude.

The Earth rotates 15 degrees in one hour, correlating degrees, minutes, and seconds of longitude to hours and minutes of time.

East of a position, it will be later, while west will be earlier due to the Earth's eastward rotation.

The difference in solar time between two points can be calculated by knowing their longitude.

Time zones were created to standardize time in a certain area, with the Earth divided into 24 time zones, each 15 degrees wide.

Each time zone adopts the solar time of its central meridian, leading to the use of local mean time (LMT) or local time (LT).

Large countries may have more than one time zone, with lines dividing time zones adapting to territorial limits.

Time zones can be named using the central meridian's number, letters (excluding J), or position relative to the prime meridian.

Coordinated Universal Time (UTC) is the international reference time used in air operations, corresponding to the local mean time of the prime meridian.

UTC is also known as GMT (Greenwich Mean Time) and Zulu Time, all referring to the same time.

Using UTC facilitates coordination and commerce, especially in aviation, where crossing multiple time zones is common.

The time of sunrise and sunset is crucial for air operations and is published by civil aviation authorities for each aerodrome.

The official tables of sunrise and sunset times determine the boundary between daytime and nighttime operations.

Transcripts

today we will talk about time zones and

the coordinated universal time

so before looking at these concepts we

have to see how time is measured

on earth the passage of time is measured

by the movement of the sun in the sky

although in fact it is the rotation of

the earth around its own axis that

produces the effect that the sun moves

in the sky

with this in mind the earth makes one

complete revolution around its own axis

in approximately 24 hours and that

period of time is what is considered a

day

now the current time of day depends on

our position on earth

as we can see in this example the sun

always shines on one side of the earth

while the other side remains in darkness

in this case we can see the line that

divides both sides which is the sunrise

this way in the north coast of colombia

for example it is 3 a.m while at the

same time on the west coast of africa it

is 9 a.m and on the east coast it is

noon

taking this into account we can say that

each position on earth will have a

specific solar time depending on the

relative position of the sun in the sky

now the solar time is the real time

relative to the position of the sun and

an observer at a point on the earth's

surface

one important thing to bear in mind is

that points on the same meridian will

have the same solar time

so in other words we can say that solar

time depends on longitude

so let's relate the degrees minutes and

seconds of longitude to the passage of

time in terms of hours and minutes

as we already mentioned the earth makes

one complete revolution around its own

axis in 24 hours

so we can say that it rotates 360

degrees in 24 hours

this means that it takes one hour for

the earth to rotate 15 degrees

and therefore it takes 4 minutes for the

earth to rotate 1 degree and four

seconds to rotate one minute of

longitude

with this being said to know if it is

later or earlier at a point on the earth

with respect to our position we must

take into account that the earth rotates

from west to east this way in all places

east of our position it will be later

while in places west of our position it

will be earlier

we can see this more clearly in this

example

here we have the lines that represent

noon sunrise and sunset

so let's say that we are in this yellow

point in africa and as we can see

currently it is noon

from this perspective it is more obvious

that in all places to the east of our

position it will be later while in all

places to the west it will be earlier

now the question is how early or how

late is it at a certain point on the

earth with respect to our position

well it is possible to calculate how

different the solar time is between two

points by knowing their longitude

let's see the following example here we

have the coordinates for the cities of

miami and berlin

so the question is if the solar time in

miami is 4 am what solar time will it be

in berlin

well first we have to determine the

difference in longitude which is the

distance between the meridian that

passes through miami and the meridian

that passes through berlin in terms of

degrees minutes and seconds of arc

so as we can see miami is 80 degrees and

11 minutes west of the prime meridian

while berlin is 13 degrees and 24

minutes to the east

now since the points are on different

hemispheres we must add the longitudes

to obtain the difference in longitude

which in this case is 93 degrees and 35

minutes

now that we have the difference in

longitude we must convert it to time

so as we previously mentioned one degree

of arc corresponds to four minutes of

time and one minute corresponds to four

seconds of time

in this order of ideas 93 degrees equals

to 372 minutes of time and 35 minutes is

equal to 140 seconds of time

if we express it correctly it would be 6

hours 12 minutes and 2 minutes 20

seconds

this way the total difference in solar

time between miami and berlin is 6 hours

14 minutes and 20 seconds

now that we know the difference in solar

time between these cities it must be

determined whether to add or subtract

the time difference depending on the

relative positions of the cities

as mentioned before in all places to the

east it will be later and in all places

to the west it will be earlier

this means that if the city is to the

west we have to subtract the time

difference while if the city is to the

east we have to add the time difference

in this case since we have to determine

the solar time in berlin which is to the

east of miami we have to add the time

difference obtaining the current solar

time in berlin which is 10 am 14 minutes

and 20 seconds

with this method it is possible to

determine the difference in solar time

between any two points on the earth

which implies that whenever there is a

difference in longitude however small

there will also be a difference in solar

time

this includes cities within the same

country or even within the same province

here for example we can see the

coordinates of quito and guayakil which

are two cities in ecuador which is a

small country in south america

so let's determine the difference in

solar time between these cities

here since both points are on the same

hemisphere we have to subtract the

longitudes to obtain the difference in

longitude which is 1 degree and 32

minutes

then we convert this into time obtaining

a difference in solar time of 6 minutes

and 8 seconds

so this implies that if for example the

solar time in keto is 8 am we must

subtract the time difference since

guayaquil is to the west obtaining the

current solar time of 7 am 53 minutes

and 52 seconds

as we can infer having time differences

between nearby cities is a big problem

to establish schedules and coordinate

operations so in order to standardize

the same time in a certain area time

zones were created

so for reasons of convenience and

standardization it was decided that the

earth would be divided into 24 time

zones each 15 degrees wide and as we

know 15 degrees equals to one hour so

each time zone differs by one hour

this way the total width of each time

zone is 15 degrees which means that it

extends seven degrees and thirty minutes

to either side of its central meridian

now each time zone adopts the solar time

of its central meridian

this way all countries and territories

within the same time zone will assume

the same standard time which means that

they are no longer based on their actual

solar time

now this standardized time for each time

zone is known as local mean time and is

usually abbreviated as lmt or only lt

in this example the local time for

countries within this time zone will

adopt the actual solar time of the 75

degrees west meridian

however in some cases the countries are

so large that they may have more than

one time zone

a clear example of this is the

contiguous united states which have four

time zones and as we can see the lines

that divide each time zone are not

always straight

since they adapt to territorial limits

in borders

and this not only happens in the us it

actually happens worldwide

since governments have made arrangements

to modify time zones to coincide with

border or territorial boundaries as we

can see here

now there are several ways of naming the

different time zones

we can use the number of its central

meridian for example 60 degrees west

meridian time

we can also use letters from a to z

excluding the j for example the z time

or zulu time

and finally we can use the position of

the time zone relative to the prime

meridian time zone for example utc plus

five here we can see how the different

time zones are named based on these

methods

let's now talk about the coordinated

universal time which is abbreviated as

utc

this is the international time used as

reference in air operations and it

corresponds to the local mean time of

the prime meridian

another names for this utc time are gmt

which stands for greenwich mean time and

zulu time which represents the time zone

z

however in practice they all refer to

the same time so they can be used

indistinctively

now the use of the coordinated universal

time greatly facilitates coordination

and commerce especially on long flights

where several time zones are crossed

and also by using utc everyone can be

sure that they are referring to the same

exact time without having to make

conversions and calculations which

results pretty useful for flight plans

notems radio communications and many

other aviation applications

now an important time to keep in mind is

the time of sunrise and sunset for a

specific airport since some air

operations are limited to daytime

in this case although the local time of

the time zone is used as reference the

actual solar time at which sunrise and

sunset occur at that specific position

is taken into account

and it is also important to bear in mind

that at the same airport the sun will

rise and set at different local times

throughout the year

this is why the civil aviation authority

of each state shall publish official

tables with sunrise and sunset times for

each aerodrome throughout the year as we

can see here

these times will determine the boundary

between what is considered daytime and

nighttime operation

i hope the information presented in this

video was useful

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