Time Zones and the Coordinated Universal Time
Summary
TLDRThis 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
- đ Time is measured by the Earth's rotation, which takes approximately 24 hours to complete one full revolution, creating the concept of a day.
- đ 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.
- đĄ 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.
- đ 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.
- đ 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.
- đ 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.
- đ Large countries may span multiple time zones, leading to non-straight lines dividing time zones to accommodate political borders.
- âïž UTC is crucial for coordinating long flights that cross multiple time zones, ensuring everyone refers to the same exact time without needing conversions.
- đ 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.
- đ 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.
- đ 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
đ 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.
đ° 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.
âïž 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.
Mindmap
Keywords
đĄTime Zones
đĄCoordinated Universal Time (UTC)
đĄSolar Time
đĄMeridian
đĄLocal Mean Time (LMT)
đĄPrime Meridian
đĄSunrise and Sunset
đĄGreenwich Mean Time (GMT)
đĄAerodrome
đĄZulu Time
đĄRotation of the Earth
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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thanks for watching
[Music]
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