In this unit we discussed calendars and clocks. Has there been adjustments in either that go beyond the reading material? That is a question for you to answer.
How accurate is the Gregorian calendar? That is, when
will it start producing noticeable errors? For example, you might say
something like: Our calendar will be off by one day in XXX years. Has there been any
official adjustments to the Gregorian calendar
beyond what is presented in the reading material? If so, what are they,
why are they needed, and when will they be implemented (or already have been
implemented)? If no, why not? What are some proposed
minor corrections to the Gregorian calendar. Note: There are a
zillion proposed calendar reforms .... I'm only interested in proposed
adjustments to our present calendar .... minor tweaks.
The Gregorian Calendar is not perfect. You
wouldn't expect it to be since it was proposed in 1582. Any slight
inaccuracies back then would grow in time ... forcing eventual future
adjustments in the calendar. In addition, we know so much
more about the motion of the earth now. For example, no one back then
realized that the tides are slowing down the rotation rate of the earth ...
causing the length of a day to increase. Taken into account, in 4,000
years the Gregorian calendar will be off by .8 to 1.1 days. Some have
proposed to reform the present Gregorian calendar by eliminating
leap years in 4000 AD and every 4000 years hence. This would make the
calendar accurate to within 1 day in 20,000 years. This has not
been adapted mainly because the present rate of deceleration (of the earth's
rotation rate) is not precisely known. It has been well established that
several other variables also change the duration of a day. Climate
change causes a redistribution of water on the earth and that affects the
rotation rate of the earth. Tsunami and earthquakes shifts mass around
causing a similar change. Even convection currents within the earth's core and
mantle mess things up. How do astronomers deal with that? See the
next answer.
Has there been any official adjustments to our clocks that go beyond
what is presented in the reading material? If so, what are they, why are
they needed, and when will they be implemented (or already have been
implemented)?
Were you aware that since 1972, there were several (over 25)
adjustments to our clocks known as leap seconds? These
adjustments are done at not-regular intervals (and planned only 6 moths in
advance) mainly because the change in the earth's rotation rate occurs in
non-regular intervals. Some of the causes are tidal braking (which
is fairly predictable) but also from changes in mass distribution occurring on
the earth from plate tectonics (including earthquakes and volcanoes) and
changes in sea levels due to global warming. One such adjustment occurred on June 30,
2015.
Note: It should be mentioned that the duration of a year is relatively
constant over time. It is when we measure the duration of the year in days
where this becomes a problem (since the duration of a day varies)..