Oct 16, 2020
HOW
DID
EARTH
GET
ITS
NAME?
The answer is, we don't know.
The name "Earth" is derived
from both English and German
words, 'eor(th)e/ertha' and 'erde',
respectively, which mean ground
But, the handle's creator is
unknown. One interesting
fact about its name: Earth
is the only planet that wasn't
named after a Greek or
Roman god or goddess
For example, Saturn was named
after the Roman god of agriculture,
and Jupiter's name comes from
the King of the Roman gods
The Earth truly is a planet of extremes,
from ice-cold tundra to steamy rain
forests, from ocean trenches to snow-
covered peaks
Earth is unique among the known planets: it has an abundance
of water. Other worlds - including a few moons - have atmospheres,
ice, and even oceans, but only Earth has the right combination
to sustain life
PLATE TECTONICS KEEP THE PLANET COMFORTABLEPlate tectonics may be a phase in the evolution of planets that has implications for the habitability of exoplanets, according to new research
published this month in the journal Physics of the Earth and Planetary Interiors
Two of the things that make Earth unique in our solar system are that it
has plate tectonics – with the surface broken up into a number of tectonic
plates that drift around, moving continents and causing earthquakes – and life
Plate tectonics provides a mechanism for this global
thermostat. Most volcanism on the Earth occurs at
plate boundaries in response to plate tectonics. And
the most important volcanic products by mass – by
a large amount – are two greenhouse gases: carbon
dioxide and water. As they move over the Earth’s
surface, some plates get recycled back into the mantle,
at places like the Marianas Trench in the Pacific Ocean
Enormous amounts of water and
carbonate (the mineral form of CO2)
get recycled back into the interior
as they do
(700 to 10000 km)
(80 to 700 km)
(50 to 80 km)
(12 to 50 km)
(0 to 12 km)
Magnetic fields around planets behave
in the same way as a bar magnet. But at
high temperatures, metals lose their
magnetic properties. So it’s clear that
Earth’s hot iron core isn’t what creates
the magnetic field around our planet
Instead, Earth’s magnetic field is caused by a dynamo effect
On Earth, flowing of liquid metal in the outer core of the planet generates electric currents. The rotation of Earth on its axis causes these
electric currents to form a magnetic field which extends around the planet
Earth rotates once in about 24 hours with respect to the Sun,
but once every 23 hours, 56 minutes, and 4 seconds with
respect to other, distant, stars
Earth's rotation is slowing slightly with time; thus, a day
was shorter in the past
This is due to the tidal effects the Moon has on
Earth's rotation
Atomic clocks show that a modern-day is
longer by about 1.7 milliseconds than a
century ago, slowly increasing the rate at
which UTC is adjusted by leap seconds
Analysis of historical astronomical records shows
a slowing trend of about 2.3 milliseconds per
century since the 8th century BCE
At Earth’s equator, the speed of Earth’s spin is
about 1,000 miles per hour (1,600 km per hour)
The day-night has carried you around in a grand
circle under the stars every day of your life, and
yet you don’t feel Earth spinning
sixA sti no etatoR ot sruoH 4 2ekaT t’nseo DhtraE
A tropical year - also called many other things -
is approximately 365 days, 5 hours, 48 minutes,
and 45 seconds long. This equates to 365.242189 days
Tropical years are measured from either an equinox
or solstice to the next. You can measure from the
Vernal or Autumnal equinox, or the Summer and
Winter solstices
In reality, the length of a tropical year is calculated
by the amount of time it takes planet Earth to revolve
around the Sun. It's not exact because it differs from
year to year
A true tropical year can vary in length up to a half hour
For example, the year 2027 will last for 365 days, 5 hours and 39 minutes. Whereas the year 2032 will last for 365 days and 6 hours
- much longer
Furthermore, 100% accuracy is not always possible. When calculating the time of a tropical year from start to end, it's common to be
off by a few seconds or more
A YEAR
ON EARTH
ISN’T
365 DAYS
Earthquake Weather Is a Myth
"Each culture has a its own version of 'earthquake weather' to rationalize when and where a earthquake will hit," seismologist
Dr. Lucy Jones of Caltech tells Popular Mechanics
"Earthquakes are below the surface and need a constant fault to happen and this has nothing to do with weather
"An earthquake is caused by a sudden slip on a fault. Tectonic plates are always slowly moving, but they can get stuck at their edges due to
friction. When the stress on the edge of a tectonic plate overcomes the friction, there is an earthquake that releases energy in waves that
travel through the earth's crust and cause the shaking that is felt
The Pacific Plate consists of most of the Pacific Ocean floor, and also includes Baja California and the California coastline.
The North American Plate comprises most of the North American continent, including the inland parts of California, as well
as parts of the Atlantic and Arctic Oceans' floors. The primary boundary between these two plates is the San Andreas Fault
SEAS COULD RISE 2.5 FEET BY 2100The figures for both pathways are more pessimistic than those outlined by the UN intergovernmental panel on climate change (IPCC),
which predicts the worst possibility is a 1.1-metre rise by 2100
The gap reflects advances in climate science and differences in approach. The IPCC works largely through consensus among scientific
working groups, which tends to produce relatively conservative estimates
By contrast, the new survey – published in the journal Climate and Atmospheric Science – aggregates the views of 106 specialists,
who were chosen because they have published at least six peer-reviewed papers on the subject in major academic journals
As a result, the predictions are more representative of a range of views in the field.
The higher estimates highlight growing concern about the world’s two biggest ice sheets, in Antarctica and Greenland
Satellite data and on-the-ground measurements show these regions are melting faster than most computer models predicted
CLOUDS HELP REGULATE EARTH'S TEMPERATURE
Clouds play an important role in both warming and cooling our planet. Clouds give us a cooler climate on Earth than we would enjoy
without clouds
However, as Earth’s climate warms, we won’t always be able to count on this cooling effect
At any given moment, about two-thirds of our planet is covered by clouds. So it’s not too surprising that clouds play an important role
in Earth’s climate!
Louds affect climate in two major ways
First, they are an essential part of the water cycle. Clouds provide an important link between the rain and snow, oceans and lakes,
and plants and animals
Secondly, clouds also have an important effect on Earth’s temperature. But it’s a bit complicated: Clouds can both cool down and
warm up the temperatures on Earth
Clouds can block light and heat from the Sun, making Earth’s temperature cooler
Clouds within a mile or so of Earth’s surface tend to cool more than they warm. These low, thicker clouds mostly reflect the Sun’s heat.
This cools Earth’s surface
EARTH IS A HEAT ENGINE
Earth Is a Heat EnginThe Earth is a body of stored heat, radiating into space
This heat is associated with two things; one is that the very high temperature of the inner parts of the Earth are very high,
and the other is the result of heat generated due to radioactive decay of material in the deep Earth
Were it not for the second of these factors the Earth would long ago have frozen solid -- it has had plenty of time to cool from
its initial hot state
This internal heat, combined with the fact that we know from several lines of evidence discussed under Topic 2 that the Earth is not
internally rigid, causes the interior to be in continuous motion in a complex pattern of slow upwelling and downwelling that is becoming
clearer as seismic methods (Topic 4) reveal the internal structure of the Earth in increasing detail
THE
FIRST
OZONE
HOLE
IS
STILL
HEALING
Scientific evidence of the depletion of the ozone layer over the Antarctic was first presented in 1985, and in 1987 the Montreal protocol
was signed, binding world governments to reduce and phase out the harmful chemicals identified as causing the problem
The ozone layer is showing signs of continuing recovery from man-made damage and is likely to heal fully by 2060, new evidence shows
The measures taken to repair the damage will also have an important beneficial effect on climate change, as some of the gases that
caused the ozone layer to thin and in places disappear also contribute to warming the atmosphere. Phasing them out could avoid as
much as 0.5C (0.9F) of warming this century
Recovery from the holes and thinning caused by aerosol chemicals has progressed at a rate of about 1% to 3% a decade since 2000,
meaning the ozone layer over the northern hemisphere and mid-latitudes should heal completely by the 2030s, if current rates are
sustained
THE DAYS ARE GETTING LONGER �
BUT VERY, VERY SLOWLY
Scientists used a combination of astronomical theory and geochemical signatures buried in ancient rocks to show that 1.4bn years ago
the Earth turned a full revolution on its axis every 18 hours and 41 minutes
The number means that, on average, the length of the day on Earth has grown by approximately one 74 thousandth of a second per year
since Precambrian times, a trend that is expected to continue for millions, if not billions, of years more
As the Earth’s rotation gradually winds down, the moon moves further away
Writing in Proceedings of the National Academy of Sciences, Stephen Meyers at the University of Wisconsin-Madison and Alberto
Malinverno at Columbia University in New York calculate that over the past 1.4bn years the moon has drifted about 44,000km from
Earth to a distance of 384,400km
hT a s ne Ss tu ari rsV iner to heM Uer nA i v eer r se ehT
An estimated 10 nonillion (10 to the 31st power) individual viruses exist on our planet—enough to assign one to every star in the universe
100 million times over.
Viruses infiltrate every aspect of our natural world, seething in seawater, drifting through the atmosphere, and lurking in miniscule
motes of soil
Generally considered non-living entities, these pathogens can only replicate with the help of a host, and they are capable
of hijacking organisms from every branch of the tree of life—including a multitude of human cells
Yet, most of the time, our species manages to live in this virus-filled world relatively free of illness. The reason has less
to do with the human body’s resilience to disease than the biological quirks of viruses themselves, says Sara Sawyer,
a virologist and disease ecologist at the University of Colorado Boulder. These pathogens are extraordinarily picky about
the cells they infect, and only an infinitesimally small fraction of the viruses that surround us actually pose any threat to
humans
EARTH IS RADIOACTIVE
Uranium, thorium and potassium are the main elements contributing to natural terrestrial radioactivity
The isotopes 228U, 235U, 232Th and 40K decay with half-lives so long that significant amounts remain in the earth,
providing a continuing source of heat
The slow decay of these isotopes also provides the basis for radiometric age dating and isotopic modelling of
the evolution of the earth and its crust
There is a complex interplay between their heat production and the processes involved in crust formation
Phenomena such as volcanism, earthquakes,
and large-scale hydrothermal activity associated
with ore deposition reflect the dissipation of heat
energy from the earth, much of which is derived
from natural radioactivity.
The higher levels of radioactive
elements during the early history
of the earth resulted in higher
heat flow. A l l three of the
radioactive elements are strongly
partitioned into the continental
crust, but within the crust their
distribution is determined by
their different chemical properties
LIFE BELOW THE SEAFLOOR
In fact, water percolating into the crust forms the largest aquifer on earth. This sub-seafloor system contains a whopping two percent
of the ocean’s volume, and scientists believe it may be home to large amounts of microbial life
These tiny microbes are of global importance. Their activity in the sub-seafloor environment shapes the chemistry of the ocean and
its influence on the atmosphere
Little is known about the sub-seafloor environment or the hardy microbes who thrive there, under intense levels of pressure and far
from the rays of the sun
More will be clear soon, however, as Bigelow Laboratory scientists analyze data from an October cruise to the Mid-Atlantic Ridge.
Along this underwater mountain range in the Atlantic Ocean, the Earth’s tectonic plates are slowly spreading apart, providing scientists
with easier access to the rock in the ocean crust
There are thousands of known species of mosses. A hardy plant, it has been found in habitats ranging from the humid tropics to
the polar regions, fallen logs to lakes, rivers, and streams
In fact, moss has been found just about everywhere, except in salt water
Moss is a relatively uncomplicated plant, lacking the leaves, stems, roots, and buds we often associate with “vascular plants"
such as ferns, pine trees, and flowers. As a non-vascular plant, the body of moss has no roots; rather, it uses tiny threads to
anchor itself to the stones, trees, or ground where it grows
People have used mosses for a variety of purposes. During World War II, Sphagnum, a certain variety of moss, was used to
dress soldiers' wounds. In addition to absorbency, it was also found to have mild antibiotic properties. In Mexico, moss is used
as a Christmas decoration, and many Japanese gardeners cultivate mosses to add a sense of age and calmness to their gardens
MOSSES ARE EVERYWHERE
FEI L O NE K EA ARM TT HA
PHOT SS SG IBNI L
H ET
Earth is well equipped as a planet and ideally placed in our solar
system and galaxy to support life as we know it. The product of
some 4.6 billion years of cosmic construction, our planet is flush
with life thanks to a fortuitous set of conditions
The solar system is comfortably nestled in a safe harbor
between major spiral arms, and its nearly circular orbit helps
it avoid the galaxy’s perilous inner regions. There are
relatively few stars near the sun, reducing risks to Earth
from gravitational tugs, gamma-ray bursts, or collapsing
stars called supernovae
Ancient plantlike organisms in the oceans added oxygen to the
atmosphere and created a high-altitude layer of ozone that
shielded early land species from lethal radiation.
Stars more massive than the sun burn hotter and usually
don’t live long enough for planets to develop life. Less
massive, younger stars are often unstable and are prone to
blasting their planets with bursts of radiation
The interstellar cloud of gas and dust that gave rise to
Earth contained enough radioactive elements to power a
churning core for billions of years. This creates a magnetic
field that protects the planet from dangers like solar flares
Earth is tilted with respect to the sun, and teeters as it spins.
This tiny wobble can shift the climate from hot to icy every
41 ,000 years—and might vary more without the
moon’s stabilizing pull