TECHNOPHILIA: Would a cell phone work on a submerged submarine?

TECHNOPHILIA: Would a cell phone work on a submerged submarine?: Cell phone signals use very high frequency radio waves around 800 or 1900 megahertz . They travel in a straight line, are extremely sus...

Would a cell phone work on a submerged submarine?

Cell phone signals use very high frequency radio waves around 800 or 1900 megahertz . They travel in a straight line, are extremely susceptible to interference and break apart as soon as they encounter salty seawater.

Even above the ocean's surface, a submarine would need to be pretty close to shore because cell phones rely on a network of base stations, or cell phone towers, to transmit signals. In theory, a cell phone might be able to communicate with a tower as far as 45 miles (72 kilometers) away, but a signal at this distance would be far from reliable; a range of just a few miles is more typical.

Submarines must stay submerged at a depth of about 200 to 330 feet (60 to 100 meters) in order to avoid detection. For decades, submerged submarines have communicated only through extremely low frequency (ELF) or very low frequency (VLF) radio waves because signals in these very low ranges (300 hertz to 30 kilohertz) are able to travel long distances and penetrate seawater .

But ELF and VLF have extremely limited bandwidth, with data transfer rates ranging from a few hundred bits per second to as low as a few bits per minute. To get reception, submarines must tow large antenna cables and reduce their speed underwater.

In recent years, the U.S. Navy has explored new technologies, such as small communication buoys that can be launched to the surface to establish a connection with military satellites and quantum key distribution, which seeks to use the principles of quantum mechanics to communicate securely with submerged subs .

TECHNOPHILIA: Why Does the Date of Easter Change Every Year?

TECHNOPHILIA: Why Does the Date of Easter Change Every Year?: Why does the date of Easter change every year? Have you ever wondered why Easter Sunday can fall anywhere between March 22 and April 25...

Why Does the Date of Easter Change Every Year?

Why does the date of Easter change every year?

Have you ever wondered why Easter Sunday can fall anywhere between March 22 and April 25? And why do Eastern Orthodox churches celebrate Easter on a different day than Western churches? These are all good questions with answers that require a bit of explanation. In fact, there are as many misunderstandings about the calculation of Easter dates, as there are reasons for the confusion.
What follows is an attempt to clear up at least some of the confusion.

The Short Answer

At the heart of the matter lies a very simple explanation. The early church fathers wished to keep the observance of Easter in correlation to the Jewish Passover. Because the death, burial, and resurrection of Jesus Christ happened after the Passover, they wanted Easter to always be celebrated subsequent to the Passover. And, since the Jewish holiday calendar is based on solar and lunar cycles, each feast day is movable, with dates shifting from year to year. Now, from here the explanation grows more complicated.

The Long Answer

Today in Western Christianity, Easter is always celebrated on the Sunday immediately following the Paschal Full Moon date of the year. I had previously, and somewhat erroneously stated, "Easter is always celebrated on the Sunday immediately following the first full moon after the vernal (spring) equinox." This statement was true prior to 325 A.D.; however, over the course of history (beginning in 325 A.D. with the Council of Nicea), the Western Church decided to established a more standardized system for determining the date of Easter.

In actuality, the date of the Paschal Full Moon is determined from historical tables, and has no correspondence to lunar events.
As astronomers were able to approximate the dates of all the full moons in future years, the Western Christian Church used these calculations to establish a table of Ecclesiastical Full Moon dates. These dates would determine the Holy Days on the Ecclesiastical calendar.
Though modified slightly from its original form, by 1583 A.D. the table for determining the Ecclesiastical Full Moon dates was permanently established and has been used ever since to determine the date of Easter. Thus, according to the Ecclesiastical tables, the Paschal Full Moon is the first Ecclesiastical Full Moon date after March 20 (which happened to be the vernal equinox date in 325 A.D.). So, in Western Christianity, Easter is always celebrated on the Sunday immediately following the Paschal Full Moon.
The Paschal Full Moon can vary as much as two days from the date of the actual full moon, with dates ranging from March 21 to April 18. As a result, Easter dates can range from March 22 through April 25 in Western Christianity.

Eastern vs. Western Easter Dates

Historically, Western churches used the Gregorian Calendar to calculate the date of Easter and Eastern Orthodox churches used the Julian Calendar. This was partly why the dates were seldom the same.
Easter and its related holidays do not fall on a fixed date in either the Gregorian or Julian calendars, making them movable holidays. The dates, instead, are based on a lunar calendar very similar to the Hebrew Calendar.
While some Eastern Orthodox Churches not only maintain the date of Easter based on the Julian Calendar which was in use during the First Ecumenical Council of Nicea in 325 A.D., they also use the actual, astronomical full moon and the actual vernal equinox as observed along the meridian of Jerusalem. This complicates the matter, due to the inaccuracy of the Julian calendar, and the 13 days that have accrued since A.D. 325. This means, in order to stay in line with the originally established (325 A.D.) vernal equinox, Orthodox Easter cannot be celebrated before April 3 (present day Gregorian calendar), which was March 21 in A.D. 325.
Additionally, in keeping with the rule established by the First Ecumenical Council of Nicea, the Eastern Orthodox Church adhered to the tradition that Easter must always fall after the Jewish Passover, since the resurrection of Christ happened after the celebration of Passover. Eventually the Orthodox Church came up with an alternative to calculating Easter based on the Gregorian calendar and Passover, and developed a 19-year cycle, as opposed to the Western Church 84-year cycle.
Since the days of early church history, determining the precise date of Easter has been a matter for continued argument. For one, the followers of Christ neglected to record the exact date of Jesus' resurrection. From then on the matter grew increasingly complex.

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