Is life on Earth possible without?

The sun

Ordinarily, sunlight is broken down into three major components:

(1) Visible light, with wavelengths between 0.4 and 0.8 micrometer.

(2) Ultraviolet light, with wavelengths shorter than 0.4 micrometer.

(3) Infrared radiation, with wavelengths longer than 0.8 micrometer.

The visible portion constitutes nearly half of the total radiation received at the surface of Earth. Although ultraviolet light constitutes only a very small proportion of the total radiation, this component is extremely important. It produces vitamin D through the activation of ergo sterol. Infrared radiation has its chief merit in its heat-producing quality. Close to half of total solar radiation received at the surface of Earth is infrared

The Sun-Earth distance is (of about 150 million kilometers) and the sun mass is (of about 1.9891×1030 kg).

The Sun’s volume would need 1.3 million Earths to fill it.

The Sun has made life on Earth possible, providing warmth as well as energy that organisms like plants use to form the basis of many food chains.

The Moon

The moon diameter is 3,475 kilometers, a bit more than one-fourth (27 percent) the size of Earth. This means the moon has a great effect on the planet and very possibly is what makes life on Earth possible.

Causing predictable rises and falls in sea levels known as tides. To a much smaller extent, tides also occur in lakes, the atmosphere, and within Earth's crust.

High tide results on the side of the Earth nearest the moon due to gravity, and it also happens on the side farthest from the moon due to the inertia of water. Low tides occur between these two humps.

The pull of the moon is also slowing the Earth's rotation, an effect known as tidal braking, which increases the length of our day by 2.3 milliseconds per century. The energy that Earth loses is picked up by the moon, increasing its distance from the Earth, which means the moon gets farther away by 1.5 inches (3.8 centimeters) annually.

The moon's gravitational pull may have been key to making Earth a livable planet by moderating the degree of wobble in Earth's axial tilt, which led to a relatively stable climate over billions of years where life could flourish.

 

Ozone layer

Also called ozonosphere, region of the upper atmosphere, between roughly 15 and 35 km above Earth’s surface, containing relatively high concentrations of ozone molecules (O₃). The ozone layer effectively blocks almost all solar radiation of wavelengths less than 290 nanometers from reaching Earth’s surface, including the two major types of UV light: UVB and UVA and other forms of radiation that could injure or kill most living things.

Ozone layer depletion increases the amount of UVB and UVA that reaches the Earth’s surface. Laboratory and epidemiological studies demonstrate that UVB causes non-melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to the development of cataracts, a clouding of the eye’s lens.

UVA light is even more harmful than UVB, penetrating more deeply and causing a deadly skin cancer, melanoma, and premature aging. The ozone layer absorbs about 98 percent of this devastating UV light.

UV light can penetrate organisms’ protective layers, like skin, damaging DNA molecules in plants and animals.

 

Earth's Atmosphere

According to NASA, the gases in Earth's atmosphere include:

Nitrogen: 78% - Oxygen: 21% - Argon: 0.93% - Carbon dioxide: 0.04%

Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor.

Both nitrogen and oxygen are essential to human life on the planet, they have little effect on weather and other atmospheric processes. The variable components, which make up far less than 1 percent of the atmosphere, have a much greater influence on both short-term weather and long-term climate. For example, variations in water vapor in the atmosphere are familiar to us as relative humidity. Water vapor, CO₂, CH₄, N₂O, and SO₂ all have an important property: They absorb heat emitted by Earth and thus warm the atmosphere, creating what we call the "greenhouse effect." Without these so-called greenhouse gases, the Earth's surface would be about 30 degrees Celsius cooler – too cold for life to exist as we know it. Trace amounts of gases like CO₂ warm our planet's atmosphere enough to sustain life.

 

Special properties of water:

All living organisms depend on water. The characteristics of water make it a very unique substance. The polarity of water molecules can explain why certain characteristics of water exist, such as its ability to dissolve salts,

acids, sugars as well as alkalis and gases. Most cell components including proteins, and DNA dissolve in water making it the basis of life.

These characteristics not only maintain life through biochemical processes, but also create the hospitable environments that sustain life.

At 4°C water expands on heating or cooling. This density maximum together with the low ice density results in:

-      The necessity that all of a body of fresh water (not just its surface) is close to 4 °C before any freezing can occur.

-      The freezing of rivers, lakes, and oceans is from the top down, so   

          permitting survival of the bottom ecology, insulating the water from     

          further freezing, reflecting back sunlight into space and allowing rapid   

          thawing

-      Density driven thermal convection causing seasonal mixing in deeper temperate waters carrying life-providing oxygen into the depths.

The large heat capacity of the oceans and seas allows them to act as heat reservoirs such that sea temperatures vary only a third as much as land temperatures and so moderate our planet's climate.

Water’s high surface tension plus its expansion on freezing encourages the erosion of rocks to give soil for our agriculture.

 

The gravity

 

On Earth, gravity gives weight to physical objects. The force of Earth's gravity is the result of the planets mass and density – 5.97237 × 1024 kg and 5.514 g/cm3, respectively. This results in Earth having a gravitational strength of 9.8 m/s² close to the surface.

Over the past three decades, researchers have carefully teased out how particular kinds of cells and body systems are affected by microgravity.

Brain: Since the 1980s, scientists have observed that the absence of gravity leads to enhanced blood retention in the upper body, and so increased pressure in the brain. Recent research suggests this heightened pressure reduces the release of neurotransmitters, key molecules that brain cells use to communicate.

In the absence of gravity, scientists have found that the type of cells in charge of bone formation are suppressed. At the same time the type of cells responsible for degrading bone are activated. Together it adds up to accelerated bone loss.

Immunity: By comparing astronauts’ blood samples before and after their space missions, researchers discovered that the lack of gravity weakens the functions of T-cells. These specialized immune cells are responsible for fighting a range of diseases, from the common cold to deadly sepsis.

 

References: www.britannica.com   www.epa.gov   www.nationalgeographic.org   www.nasa.gov

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