What makes up sunlight

Water often appears blue as this color travels the deepest before being absorbed 1. While on land, plants use nearly all of the visible range for photosynthesis. However, even underwater when only blue light is available, photosynthesis can still occur. Solar radiation provides heat, light, and energy necessary for all living organisms.

Infrared radiation supplies heat to all habitats, on land and in the water Light is also provided by solar radiation. Predators would not be able to efficiently hunt prey without light from the sun and prey would not be able to take advantage of dark areas if predators were adapted to dark habitats 1.

Human eyes are adapted to the visible spectrum, though some other species can see ultraviolet light in addition to colors In particular, the level of photosynthetically active radiation PAR that an area receives is important.

This is because different plants respond to different wavelengths of PAR 1. Most plants reflect green wavelengths while absorbing the rest of the visible light spectrum. In addition, shade plants respond to lower levels of PAR while sun plants harvest PAR more efficiently at higher light levels 7. In other words, as solar irradiance intensity increases, sun plants experience higher rates of photosynthesis. The leaves of sun plants are small and thick, with special cells allowing for these higher rates Shade plants conduct photosynthesis at a lower radiation intensity level.

Their leaves are thinner, longer and contain fewer chlorophyll cells. This makes it easier for photosynthesis to occur in low light conditions Although the main benefit of photosynthesis is energy for the plant, it has other important results. Oxygen is a byproduct of photosynthesis 1. The process ensures that more oxygen is produced than is used up by organisms in the surrounding environment. If photosynthesis does not produce enough dissolved oxygen underwater, it can create anoxic conditions where fish and other organisms cannot live 1.

Photosynthesis also consumes carbon dioxide, thus lowering carbon dioxide levels in air and water 1. An relatable way to think about solar irradiance is by looking at the difference between a watt light bulb and a watt light bulb. Both produce visible light in the same wavelengths, but the brightness and intensity are very different. The watt bulb has a higher intensity, or irradiance. The solar irradiance received by a particular location or body of water depends on the elevation above sea level, the angle of the sun due to latitude, season and time of day and scattering elements such as clouds 9.

The higher the elevation, the shorter the path from the atmosphere. This can mean a higher irradiance, though not warmer temperatures. This intense radiation contributes to the arid climates, and the thinner air means more UV radiation reaches the surface at these altitudes. The lower the angle of the sun, the larger amount of ozone the light has to pass through 9.

This is also factor in ultraviolet irradiance. Ozone absorbs UV light and can reduce radiation intensity. The angle of the sun is dependent on latitude, time of year, and time of day. The distance that radiation has to travel will be at its lowest when the sun is directly overhead. This is why the annual net solar irradiance is greater over the equator than over the northern and southern latitudes.

Solar irradiance will decrease as a hemisphere is tilted away from the sun. At greater angles morning and evening solar radiation has to pass through more of the atmosphere, which reduces its irradiance.

This is why sunlight feels less intense in the evening than at noon. Clouds and aerosols in the atmosphere can scatter and absorb all radiation bands 9. As cloud cover increases, the angle of the sun becomes less important when measuring irradiance. This is due to the increase of radiation diffusion scattering Increased cloud cover decreases irradiance, causing sunlight to feel less intense. Under these conditions, humans can become sunburned without realizing the effects until it is too late.

Sunlight is responsible for warming the Earth, oceans and atmosphere through infrared radiation. Both water and land reflect back some of that radiation to warm the atmosphere or other objects in contact with the surface. The darker the object or surface, the faster it will absorb light and heat Air temperature is indirectly dependent on solar radiation. This effect occurs through heat transfer by conduction and convection Earth absorbs infrared radiation and converts it to thermal energy.

As the surface absorbs heat from the sun, it becomes warmer than the surrounding atmosphere. The heat is then transferred by conduction contact from the warmer Earth to the cooler atmosphere Air itself is a poor conductor of heat, so convection, or the rise and fall of warm and cool air, warms the rest of the atmosphere not in contact with the surface The rising warm air is often referred to as a thermal.

As the warmed air rises, cooler air sinks to the surface, where it continues in the convection process. This reflected radiation can be trapped and absorbed by gases in the atmosphere, or re-radiated back to the Earth This process is called the greenhouse effect. Infrared light from the sun is absorbed by bodies of water and converted to heat energy.

This low energy radiation excites electrons and warms the top layer of water. Nearly all infrared radiation is absorbed within one meter of the surface 1. This heat is then transferred to greater depths through movement from wind and convection 1.

While heat is slowly transferred throughout the water column, it often does not reach all the way to the bottom. This is due to water column stratification. In the ocean and many lakes, water can stratify, or form distinct layers of water. These layers are distinguished by their temperatures, densities and often different concentrations of dissolved substances such as salt or oxygen. The different water strata are separated by steep temperature gradients known as thermoclines 1.

Photosynthesis is the process by which plants and other organisms, also known as photoautotrophs, use energy from sunlight to produce glucose. This process can occur both on land and underwater Glucose is a kind of sugar that is later converted into Adenosine Triphosphate ATP via cellular respiration 3.

ATP is an energy-bearing molecule that is used in the metabolic reactions of living organisms. This molecule is a necessity in almost all organisms 4. Photoautotrophs use sunlight, six carbon dioxide molecules, and twelve water molecules to produce one molecule of glucose, six oxygen molecules, and six water molecules.

This reaction reduces carbon dioxide levels in the air or water while producing glucose for ATP. Photosynthesis can occur underwater as long as enough light is available.

In the ocean, significant amounts of photosynthetically active radiation can be detected as deep as m below the surface Within this euphotic zone sunlight zone , photosynthesis can occur.

This process only requires light, carbon dioxide, and water As long as a photosynthesizing organism, on land or underwater, has enough of these molecules, it can produce glucose and oxygen. Photosynthesis is a series of chemical reactions that occur with the help of enzymes.

Enzymes are catalysts in biological processes and help speed up chemical reactions Photosynthesis also requires heat to activate the process. As heat increases kinetic energy causing reactants to bump into one another more often , a higher temperature can speed up chemical reactions in addition to initiating the process Although increased temperatures can speed up photosynthesis, too much heat can be detrimental At a certain temperature, enzymes become denatured and lose their shapes.

Denatured enzymes no longer speed up chemical reactions and instead slow down photosynthesis. Thus temperature is an important factor in photosynthetic production, both in activating and maintaining the process. This is why there are different optimal temperatures for photosynthesis for different organisms 1. Turbidity is a lack of water clarity caused by the presence of suspended particles 1.

These particles absorb sunlight and can cause light to be reflected off the particles in water. The more particles present in the water, the less photosynthetically active radiation that will be received by plants and phytoplankton.

This loss of sunlight decreases the rate of photosynthesis. If the photosynthetic production is limited, the dissolved oxygen level in the water will decrease In addition, turbidity can cause significant damage to water habitats by absorbing infrared radiation and increasing water temperature above normal levels.

Visible light is the only band of light on the spectrum to be considered photosynthetically active. It has the perfect amount of energy to excite the electrons needed to start photosynthesis and not damage DNA or break bonds. Ultraviolet can not be used for photosynthesis because it has too much energy. This energy breaks the bonds in molecules and can destroy DNA and other important structures in organisms 8. When plants and other photoautotrophs attempt to use UV-A nm for photosynthesis, electron transport efficiency is decreased, which in turn decreases the rate of photosynthesis 6.

On the other side of the spectrum, infrared light does not contain much energy. The insufficient energy does not excite electrons in molecules enough to be used for photosynthesis. Infrared light is converted to thermal energy instead 8. The Sun orbits the center of the Milky Way, bringing with it the planets, asteroids, comets, and other objects in our solar system. Our solar system is moving with an average velocity of , miles per hour , kilometers per hour.

But even at this speed, it takes about million years for the Sun to make one complete trip around the Milky Way. The Sun rotates on its axis as it revolves around the galaxy. Its spin has a tilt of 7. Since the Sun is not solid, different parts rotate at different rates. At the equator, the Sun spins around once about every 25 Earth days, but at its poles, the Sun rotates once on its axis every 36 Earth days.

The Sun would have been surrounded by a disk of gas and dust early in its history when the solar system was first forming, about 4. Some of that dust is still around today, in several dust rings that circle the Sun. They trace the orbits of planets, whose gravity tugs dust into place around the Sun.

The Sun formed about 4. As the nebula collapsed under its own gravity, it spun faster and flattened into a disk. Most of the nebula's material was pulled toward the center to form our Sun, which accounts for Much of the remaining material formed the planets and other objects that now orbit the Sun. The rest of the leftover gas and dust was blown away by the young Sun's early solar wind. Like all stars, our Sun will eventually run out of energy.

When it starts to die, the Sun will expand into a red giant star, becoming so large that it will engulf Mercury and Venus, and possibly Earth as well. Scientists predict the Sun is a little less than halfway through its lifetime and will last another 5 billion years or so before it becomes a white dwarf.

The Sun has several regions. The interior regions include the core, the radiative zone, and the convection zone. Once material leaves the corona at supersonic speeds, it becomes the solar wind, which forms a huge magnetic "bubble" around the Sun, called the heliosphere.

The heliosphere extends beyond the orbit of the planets in our solar system. Outside the heliosphere is interstellar space. The core is the hottest part of the Sun. That is approximately 8 times the density of gold Energy from the core is carried outward by radiation.

This radiation bounces around the radiative zone, taking about , years to get from the core to the top of the convection zone. Moving outward, in the convection zone, the temperature drops below 3. Here, large bubbles of hot plasma a soup of ionized atoms move upward toward the photosphere, which is the layer we think of as the Sun's surface.

The part of the Sun commonly called its surface is the photosphere. The word photosphere means "light sphere" — which is apt because this is the layer that emits the most visible light. Hopefully, it goes without saying — but never look directly at the Sun without protecting your eyes.

Although we call it the surface, the photosphere is actually the first layer of the solar atmosphere. It's about miles thick, with temperatures reaching about 10, degrees Fahrenheit 5, degrees Celsius. That is, astronomers should be able to use the helioseismological measurements to calculate the depth of an important boundary layer in the sun where radiation gives way to convection.

This sequence of calculations should predict the same value for the metallicity as spectroscopers measure directly from sunlight. It does not. Video : Join David Kaplan on a virtual-reality tour showing how the sun, the Earth and the other planets came to be. Recently, a weak hint about the solar metallicity has come from fleeting particles emanating from the sun called solar neutrinos.

But Asplund stands by his 1. Correcting for this difference in the standard solar model could bring the helioseismological and neutrino estimates of metallicity down to 1. In the coming years, the Borexino team expects to detect rare solar neutrinos produced in the CNO cycle, a fusion reaction in the sun in which carbon, nitrogen and oxygen atoms serve as catalysts for fusing hydrogen into helium. If it turns out that the sun is, in fact, only 1.