Guide to Space Archives

December 10, 2010December 24, 2015 by Jerry Coffey

What Causes Wind?

Oxygen is a valuable biosignature because Earth is oxygen-rich, and because life made all that oxygen. But if we find oxygen in an exoplanet atmosphere does that mean life made it? Or is there an abiotic source of oxygen? Image Credit: NASA

It was not until recent memory that what causes wind was understood. Wind is caused by air flowing from high pressure to low pressure. The Earth’s rotation prevents that flow from being direct, but deflects it side to side(right in the Northern Hemisphere and left in the Southern), so wind flows around the high and low pressure areas. This movement around is important for very large and long-lived pressure systems. For small, short-lived systems (outflow of a thunderstorm) the wind will flow directly from high pressure to low pressure.

The closer the high and low pressure areas are together, the stronger the pressure gradient, so the winds are stronger. On weather maps, lines of constant pressure are drawn(isobars). These isobars are usually labeled with their pressure value in millibars (mb). The closer these lines are together, the stronger the wind. The curvature of the isobars is also important to the wind speed. Given the same pressure gradient (isobar spacing), if the isobars are curved anticyclonically (around the high pressure ) the wind will be stronger. If the isobars are curved cyclonically (around the low pressure) the wind will be weaker.

Friction from the ground slows the wind down. During the day convective mixing minimizes this effect, but at night(when convective mixing has stopped) the surface wind can slow considerably, or even stop altogether.

Wind is one way that the atmosphere moves excess heat around. Directly and indirectly, wind forms for the primary purpose of helping to transport excess heat in one of two ways: away from the surface of the Earth or from warm regions(tropics) to cooler regions. This is done by extratropical cyclones, monsoons, trade winds, and hurricanes. Now, you have the answer to what causes wind and its primary function on our planet.

We have written many articles about the wind for Universe Today. Here’s an article about wind energy, and here’s an article about how wind power works.

If you’d like more info on wind, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

December 10, 2010September 25, 2016 by Jerry Coffey

What did Isaac Newton Invent?

Isaac Newton, Father of Classical Mechanics

Sir Issac Newton is best know for his laws of motion. Many people’s knowledge of his scientific contributions stops there. Issac Newtons inventions contributed a great deal to our current understanding of subjects from optics to theology and how early scientists were able to view their world.

In mathematics Isaac Newton inventions included laying the ground work for differential and integral calculus. His work was based on his insight that the integration of a function is merely the inverse procedure to differentiating it. Taking differentiation as the basic operation, he produced simple analytical methods that unified many separate techniques previously developed to solve apparently unrelated problems such as finding areas, tangents, the lengths of curves and the maxima and minima of functions.

Issac Newton inventions in mechanics and gravitation were summarized the Principia. His discoveries in terrestrial and celestial mechanics showed how universal gravitation provided an explanation of falling bodies on Earth and of the motions of planets, comets, and other bodies in the heavens. He explained a wide range of then unrelated phenomena: the eccentric orbits of comets, the tides and their variations, the precession of the Earth’s axis, and motion of the Moon as perturbed by the gravity of the Sun. This work includes Newton’s three famous laws of motion, fluid motion, and an explanation of Kepler’s laws of planetary motion.

Isaac Newton inventions in optics included his observation that white light could be separated by a prism into a spectrum of different colors, each characterized by a unique refractivity. He proposed the corpuscular theory of light. He was the first person to understand the rainbow. He was the first person to use a curved mirror in a telescope to prevent light form being broken up into unwanted colors.

Isaac Newton inventions and contributions to science were many and varied. They covered revolutionary ideas and practical inventions. His works in physics, mathematics and astronomy are still important today. His contributions in any one of these fields would have made him famous; taken as a whole, they make him truly outstanding.

We have written many articles about Isaac Newton’s inventions for Universe Today. Here’s an article about celestial mechanics, and here’s an article about Newton’s laws of motion.

If you’d like more info on Isaac Newton’s inventions, check out How Stuff Works for an interesting article about Isaac Newton’s inventions, and here’s a link to Isaac Newton’s Biography.

We’ve also recorded an entire episode of Astronomy Cast all about Gravity. Listen here, Episode 102: Gravity.

Sources:
How Stuff Works
University of Virginia
NASA

December 9, 2010December 24, 2015 by Jerry Coffey

Largest River In The World

[/caption]The largest river in the world can be hard to calculate. Many factors come into play: the source, the identification of the mouth, and the measurement of the river length between source and mouth. As a result, the measurements of many rivers are only approximations. So, there has been disagreement whether the Amazon or the Nile is the world’s largest river based on the inclusion of estuaries.

The mouth of a river is hard to determine in cases where the river has a large estuary that gradually widens and opens into the ocean. The source of some rivers starting in farming areas can be difficult to determine, if the river is formed by the confluence of several farm field drainage ditches which only contain water after rain. Similarly, in rivers starting in a chalk area the length of the upper course which is dry varies with how high the water table is. How large a river is between source and mouth may be hard to determine due to issues of map scale. Small scale maps tend to generalize more than large scale maps. In general, length measurements should be based on maps that are large enough scale to show the width of the river, and the path measured is the path a small boat would take down the middle of the river.

Given, and despite, this ambiguity, the Nile has been determined to be the largest river in the world followed by the Amazon and the Yangtze. The Nile is a north-flowing river in North Africa. It is 6,650 km long. It has two major tributaries, the White Nile and the Blue Nile. The Blue Nile is the source of most of the water and fertile soil in the system. The White Nile is longer and rises in central Africa beginning in Rwanda. The two rivers meet near the Sudanese capital of Khartoum. The northern section of the Nile flows almost entirely through desert. Most of the ancient civilizations of the area were centered along the river’s banks. The Nile ends in a large delta that empties into the Mediterranean Sea.

The debate over which is the largest river in the world seems to be over for now. The Nile is 250 km larger than the Amazon. Both rivers have played important roles in the evolution of the civilizations that sprang up around them and will continue to do so for centuries to come.

We have written many articles about rivers for Universe Today. Here’s an article about the world’s widest river, and here’s an article about the longest river in the world.

If you’d like more info on rivers, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:
http://news.nationalgeographic.com/news/2007/06/070619-amazon-river.html
http://news.bbc.co.uk/2/hi/6759291.stm

December 8, 2010April 26, 2016 by Jerry Coffey

Deepest Hole In The World

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The deepest hole in the world is on the Kola peninsula of Russia near the Norwegian border. This hole is being drilled for scientific study purposes and is currently over 12,200 meters deep.

In 1926, Harold Jeffreys hypothesized that a transition zone within the crust, identifiable on seismic records as a “jump” in seismic velocity, could be attributed to a change in rock type from granite to a denser basalt. The deepest hole in the world being drilled at the Kola well has now penetrated about halfway through the crust of the Baltic continental shield, exposing rocks 2.7 billion years old at the bottom. One of the more fascinating scientific findings to emerge from this well is that the change in seismic velocities was not found at a boundary marking(Jeffreys’ hypothetical transition from granite to basalt), but it was at the bottom of a layer of metamorphic rock that extended from about 3.5 to about 9.8 km beneath the surface. This rock had been thoroughly fractured and was saturated with water. Free water should not be found at these depths. This could only mean that water which had originally been a part of the chemical composition of the rock minerals themselves had been forced out and prevented from rising by a cap of impermeable rock.

This discovery has an impact on geophysical sciences and there is a potential economic impact. This water is very highly mineralized, and is a primary concentrating agent for most ore deposits. The technology for mining at these depths is not yet available. In order to get their single drill hole down as far as they did, the Soviets had to resort to experimental methods. Their chief innovation was that, instead of turning the drill bit by rotating the stem, in the Kola well the bit alone was turned by the flow of drilling mud.

As drilling continues at the deepest hole in the world many scientists are hoping for additional discoveries and a greater understanding of the inner workings and makeup of our planet.

We have written many articles about the deepest hole in the world for Universe Today. Here’s an article about how far the center of the Earth is, and here’s a forum discussion about the drillings through the Earth’s crust.

If you’d like more info on the Earth’s deepest hole, check out the 10 amazing holes in the Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Source: Wikipedia

December 5, 2010September 16, 2016 by Jerry Coffey

What Causes Earthquakes?

False-color composite image of the Port-au-Prince, Haiti region, taken Jan. 27, 2010 by NASA’s UAVSAR airborne radar. The city is denoted by the yellow arrow; the black arrow points to the fault responsible for the Jan. 12 earthquake. Image credit: NASA

The two main answers to ‘how earthquakes happen’ is: as a result of tectonic plates colliding and volcanic eruption. The shock waves associated with nuclear weapons testing and other man-made explosions. To be considered an earthquake a shock wave has to be of natural origin.

Earthquakes Caused By Tectonic Plates:
The theory of plate tectonics explains how the crust of the Earth is made of several plates, large areas of crust which float on the Mantle. Since these plates are free to slowly move, they can either drift towards each other, away from each other or slide past each other. Many earthquakes happen in areas where plates collide or slide past each other. The Elastic Rebound Theory applies to these quakes.

Major earthquakes are sometimes preceded by a period of changed activity. This might take the form of more frequent minor shocks as the rocks begin to move,called foreshocks, or a period of less frequent shocks as the two rock masses temporarily ‘stick’ and become locked together. Following the main shock, there may be further movements, called aftershocks, which occur as the rock masses settle into their new positions. Aftershocks cause problems for rescue services because they can bring down buildings that were weakened by the main quake.

Earthquakes Caused By Volcanoes:
Volcanic earthquakes are far less common than tectonic plate related ones. They are triggered by the explosive eruption of a volcano. When a volcano explodes the associated earthquake effects are usually confined to an area 16 to 32 km around its base.

The volcanoes which are most likely to explode violently are those which produce acidic lava. Acidic lava cools and sets very quickly when it contacts air. This chokes the volcano’s vent and blocks the escape of pressure. The only way a blockage can be removed is by the pressure building up until it literally explodes the blockage outward.

The volcano will explode in the direction of its weakest point, so it is not always upward. Extraordinary levels of pressure can produce an earthquake of considerable magnitude. The shock waves have been known to produce a series of tsunami in some instances.

There you have the answer to ‘how earthquakes happen’. Keep in mind that there have been man-made shock waves following large explosions, but they are not considered earthquakes because of their artificial origin.

We have written many articles about earthquakes for Universe Today. Here’s an article about the biggest earthquake, and here are some pictures of earthquakes.

If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

Sources:
http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php
http://www.geo.mtu.edu/UPSeis/where.html
http://www.geo.mtu.edu/volcanoes/hazards/primer/eq.html
http://news.discovery.com/earth/are-volcanoes-and-earthquakes-related.html

December 4, 2010December 24, 2015 by Matt Williams

Chromatic Aberration

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Some colours just can’t keep up with the others! Well, that’s probably the simplest way to put it. But when scientists talk about the characteristics of light, it would be more accurate to say that different colours of light propagate at different speeds, orhave different wavelengths, and therefore refract differently. A well-known example of this is the prism effect, where a beam of white light is broken into a rainbow of colours. The result of this is that when objects are viewed through a simple lens, light will refract (bends) at different angles, meaning that it will not image all in the same place. A distortion results in which “fringes” of color appear along the boundaries that separate dark and bright parts of the image. This effect, known as Chromatic Aberration, can be a real pain for astronomers, surveyors, photographers, or just about anyone who wants to view an object (or objects) through a lens and needs to do so clearly!

Sir Isaac Newton was the first to demonstrate this effect some two-hundred years ago when he discovered that light was composed of multiple wavelengths. These colours refract unevenly, with blue-appearing light refracting at shorter wavelengths and red-appearing light refracting at longer, with green refracting in the middle. Since that time, scientists, astronomers and opticians have come to identify two basic kinds of aberration. The first is axial (or longitudinal) where different wavelengths are focused at a different distance because the lens in unable to focus different colours in the same focal plane. The second is transverse (or lateral) aberration, where different wavelengths are focused at different positions in the focal plane and the effect is a sideward displacement of the image. In the former case, distortion occurs throughout the image whereas in the latter, distortion is absent from the centre but increases towards the edge.

There are many ways to remedy Chromatic Aberration. During the 17th century, telescopes had to be very long in order to correct for colour distortions. Sir Isaac Newton remedied this problem by creating the comparably compact, reflecting telescope in 1668 that used curved mirrors to get around this problem. The achromatic lens (or achromatic doublet) is another; a double lens that uses two kinds of glass that focuses all white light coming in at the same point on the other side of the lens. Many types of glass, known as low dispersion glasses, have been developed to reduce chromatic aberration, the most notable being glasses that contain fluorite.

The discovery of Chromatic Aberration and the development of corrective lenses were major steps in the development of the optical microscope, the telescope; which in turn was a boon for astronomers and biologist who were able to gain a greater understanding of the universe and the natural world as a result.

We have written many articles about chromatic aberration for Universe Today. Here’s an article about optical aberration, and here’s an article about achromatic lens.

If you’d like more info on Chromatic Aberration, check out Hyperphysics for a great article on chromatic aberration, and here’s a link to Wise Geek’s discussion about chromatic aberration.

We’ve also recorded an entire episode of Astronomy Cast all about Choosing and Using a Telescope. Listen here, Episode 33: Choosing and Using a Telescope.

Sources:
http://en.wikipedia.org/wiki/Chromatic_aberration
http://toothwalker.org/optics/chromatic.html
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/aber2.html
http://www.yorku.ca/eye/chroaber.htm
http://www.yorku.ca/eye/achromat.htm

December 4, 2010October 18, 2016 by Jerry Coffey

What are the Different Types Of Earthquakes?

There are two main types of earthquakes: natural and man-made. Naturally occurring(tectonic) earthquakes occur along tectonic plate lines(fault lines) while man-made earthquakes are always related to explosions detonated by man.

Tectonic earthquakes will occur anywhere there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. Plate boundaries move past each other smoothly and aseismically if there are no irregularities or asperities along the boundary that increase the frictional resistance; however, most boundaries do have such asperities that lead to stick-slip behavior. Once the boundary has locked, continued relative motion between the plates leads to increasing stress and stored strain energy around the fault surface. The energy increases until the stress breaks through the asperity, suddenly allowing sliding over the plate and releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating, and cracking of the rock, which all adds up to an earthquake. This process is called the elastic rebound theory. It is estimated that only 10 percent or less of an earthquake’s total energy is radiated as seismic energy. Most of the earthquake’s energy is used to power the fracture growth or is converted into heat generated by friction.

Occasionally, naturally occurring earthquakes happen away from fault lines. When plate boundaries occur in continental lithosphere, deformation is spread out over a much larger area than the plate boundary, so earthquakes occur away from the plate boundary and are related to strains developed within the broader zone of deformation caused by major irregularities in the fault trace. Also, all tectonic plates have internal stress fields caused by their interactions with neighboring plates and sedimentary loading or unloading. These stresses may be sufficient to cause failure along existing fault planes, giving rise to intraplate earthquakes.

The other type of earthquake is the artificial or man-made quake. This type of quake has been felt all over the world after the detonation of a nuclear weapon. There is very little actual data that is readily available on this type of quake, but, of the two types of of earthquakes it is the only type that can be easily predicted and controlled.

We have written many articles about earthquakes for Universe Today. Here’s an article about how earthquakes happen, and here’s an article about famous earthquakes.

If you’d like more info on earthquakes, check out the U.S. Geological Survey Website. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded related episodes of Astronomy Cast about Plate Tectonics. Listen here, Episode 142: Plate Tectonics.

Sources:
Types of Earthquakes
http://en.wikipedia.org/wiki/Earthquake
http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php

December 3, 2010December 24, 2015 by Jerry Coffey

How Do Magnets Work

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We have all played with magnets from time to time. Every time you do, you have asked yourself ‘how do magnets work?’ Many of us understand that magnets have two different charges and that like charges repel each other, but that still does not explain how a magnet works. Below is an attempt to explain the basics behind the secret inner workings of the mysterious magnet.

A magnet is any material or object that produces a magnetic field. This magnetic field is responsible for the property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. Materials that can be magnetized, which are strongly attracted to a magnet, are called ferromagnetic. Although ferromagnetic materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field.

Some facts about magnets include:

the north pole of the magnet points to the geomagnetic north pole (a south magnetic pole) located in Canada above the Arctic Circle.
north poles repel north poles
south poles repel south poles
north poles attract south poles
south poles attract north poles
the force of attraction or repulsion varies inversely with the distance squared
the strength of a magnet varies at different locations on the magnet
magnets are strongest at their poles
magnets strongly attract steel, iron, nickel, cobalt, gadolinium
magnets slightly attract liquid oxygen and other materials
magnets slightly repel water, carbon and boron

The mechanics of how do magnets work really breaks right down to the atomic level. When current flows in a wire a magnetic field is created around the wire. Current is simply a bunch of moving electrons, and moving electrons make a magnetic field. This is how electromagnets are made to work.

Around the nucleus of the atom there are electrons. Scientists used to think that they had circular orbits, but have discovered that things are much more complicated. Actually, the patterns of the electron within one of these orbitals takes into account Schroedinger’s wave equations. Electrons occupy certain shells that surround the nucleus of the atom. These shells have been given letter names K,L,M,N,O,P,Q. They have also been given number names, such as 1,2,3,4,5,6,7(think quantum mechanics). Within the shell, there may exist subshells or orbitals, with letter names such as s,p,d,f. Some of these orbitals look like spheres, some like an hourglass, still others like beads. The K shell contains an s orbital called a 1s orbital. The L shell contains an s and p orbital called a 2s and 2p orbital. The M shell contains an s, p and d orbital called a 3s, 3p and 3d orbital. The N, O, P and Q shells each contain an s, p, d and f orbital called a 4s, 4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 6f, 7s, 7p, 7d and 7f orbital. These orbitals also have various sub-orbitals. Each can only contain a certain number of electrons. A maximum of 2 electrons can occupy a sub-orbital where one has a spin of up, the other has a spin of down. There can not be two electrons with spin up in the same sub-orbital(the Pauli exclusion principal). Also, when you have a pair of electrons in a sub-orbital, their combined magnetic fields will cancel each other out. If you are confuse, you are not alone. Many people get lost here and just wonder about magnets instead of researching further.

When you look at the ferromagnetic metals it is hard to see why they are so different form the elements next to them on the periodic table. It is generally accepted that ferromagnetic elements have large magnetic moments because of un-paired electrons in their outer orbitals. The spin of the electron is also thought to create a minute magnetic field. These fields have a compounding effect, so when you get a bunch of these fields together, they add up to bigger fields.

To wrap things up on ‘how do magnets work?’, the atoms of ferromagnetic materials tend to have their own magnetic field created by the electrons that orbit them. Small groups of atoms tend to orient themselves in the same direction. Each of these groups is called a magnetic domain. Each domain has its own north pole and south pole. When a piece of iron is not magnetized the domains will not be pointing in the same direction, but will be pointing in random directions canceling each other out and preventing the iron from having a north or south pole or being a magnet. If you introduce current(magnetic field), the domains will start to line up with the external magnetic field. The more current applied, the higher the number of aligned domains. As the external magnetic field becomes stronger, more and more of the domains will line up with it. There will be a point where all of the domains within the iron are aligned with the external magnetic field(saturation), no matter how much stronger the magnetic field is made. After the external magnetic field is removed, soft magnetic materials will revert to randomly oriented domains; however, hard magnetic materials will keep most of their domains aligned, creating a strong permanent magnet. So, there you have it.

We have written many articles about magnets for Universe Today. Here’s an article about bar magnets, and here’s an article about super magnets.

If you’d like more info on magnets, check out some cool experiments with magnets, and here’s a link to an article about super magnets by Wise Geek.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Sources:
Wise Geek
Wikipedia: Magnet
Wikipedia: Ferromagnetism

December 3, 2010December 24, 2015 by Matt Williams

Charles Law

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For most people, the words “ideal gas” might conjure up the image of some kind of super fuel, perhaps a near-inexhaustible kind that creates zero air pollution! Sadly, this is not what is meant by ideal gas. In reality, an ideal gas is a theoretical gas composed of a set of randomly-moving, non-interacting point particles. At normal conditions such as standard temperature and pressure, most real gases such as air, nitrogen, oxygen, hydrogen, noble gases, and some heavier gases like carbon dioxide behave like an ideal gas and can be treated as such within reasonable tolerances. It is only when they are treated with higher temperatures and lower pressure that they deviate from this trend. Once they get into this territory, experimental gas laws, such as Charles’s Law, come into play.

Also known as the law of volumes, Charles’s Law is an experimental gas law which describes how gases tend to expand when heated. It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles, hence the name. This law applies generally to all gases, and also to the vapours of volatile liquids if the temperature is more than a few degrees above the boiling point. Given the interest in hot air balloons at the time, it is certainly understandable why Gay-Lussac, Charles and other scientists around the globe were so interested in the relationship between volume, pressure and temperature when it came to gasses.

In lay terms, the law states that: at constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature on the absolute temperature scale (i.e. the gas expands as the temperature increases). This can be written as: V? T, where V is the volume of the gas; and T is the absolute temperature. In mathematical terms, the law can also be expressed as: V100 – V0 = kV0, where V100 is the volume occupied by a given sample of gas at 100 °C; V0 is the volume occupied by the same sample of gas at 0 °C; and k is a constant which is the same for all gases at constant pressure. Gay-Lussac’s value for k was ½.6666, remarkably close to the present-day value of ½.7315.

Combined with Boyle’s law, these laws make up what is known as the “Ideal Gas Law” which was first stated by ÉmileClapeyron in 1834.

We have written many articles about Charles’s Law for Universe Today. Here’s an article about the Combined Gas Law, and here’s an article about Boyle’s Law.

If you’d like more info on Charles’s Law, check out a discussion about Charles’s Law, and here’s a link to an article about Charles’s Law by the Glenn Research Center.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:
http://en.wikipedia.org/wiki/Charles%27s_law
http://en.wikipedia.org/wiki/Ideal_gas
http://www.chm.davidson.edu/vce/gaslaws/charleslaw.html
http://www.grc.nasa.gov/WWW/K-12/airplane/glussac.html
http://en.wikipedia.org/wiki/Ideal_gas_law

November 19, 2010January 16, 2017 by Matt Williams

What is Planck Time?

What is the smallest unit of time you can conceive? A second? A millisecond? Hard to say seeing as how time is relative. Under the right circumstances, hours can fly by and seconds can feel like a lifetime. But unfortunately for physicists, time is not something that can be dealt with so philosophically. And since they deal with cosmological forces both infinitesimally large and small, they need units that can objectively measure them. When it comes to dealing with the small, Planck Time is the measurement of choice. Named after German physicist Max Planck, the founder of quantum theory, a unit of Planck time is the time it takes for light to travel, in a vacuum, a single unit of Planck length. Taken together, they part of the larger system of natural units known as Planck units.

Originally proposed in 1899 by German physicist Max Planck, Planck units are physical units of measurement defined exclusively in terms of five universal physical constants. These are the Gravitational constant (G), the Reduced Planck constant (h), the speed of light in a vacuum (c), the Coulomb constant 1/4??0 (ke or k), and Boltzmann’s constant (kB, sometimes k). Each of these constants can be associated with at least one fundamental physical theory: c with special relativity, G with general relativity and Newtonian gravity, ? with quantum mechanics, ?0 with electrostatics, and kB with statistical mechanics and thermodynamics. They were invented as a means of simplifying the particular algebraic expressions appearing in theoretical physics, especially in quantum mechanics.

Ultimately, Planck time is derived from the field of mathematical physics known as dimensional analysis, which studies units of measurement and physical constants. The Planck time is the unique combination of the gravitational constant G, the relativity constant c, and the quantum constant h, to produce a constant with units of time. They are often semi-humorously referred to by physicists as “God’s units” because eliminate anthropocentric arbitrariness from the system of units, unlike the meter and second, which exist for purely historical reasons and are not derived from nature. Some challenges to Planck’s Time have been mounted. For example, in 2003 during the analysis of the Hubble Space Telescope Deep Field images, some scientists speculated that where there are space-time fluctuations on the Planck scale, images of extremely distant objects should be blurry. The Hubble images, they claimed, were too sharp for this to be the case. Other scientists disagreed with this assumption however, with some saying the fluctuations would be too small to be observable, others saying that the speculated blurring effect that was expected was off by a very large magnitude.

A unit of Planck Time can be expressed as follows:

Planck Time

We have written many articles about Planck Time for Universe Today. Here’s an article about the Big Bang Theory, and here’s an article about astronomical units.

If you’d like more info on the Planck Time, check out Wikipedia, and here’s a link to Physics and Astronomy Online.

We’ve also recorded a Question Show all about Black Hole Time. Listen here, Question Show: Galileoscope, Black Hole and What Exactly is Energy?.

Sources:
http://en.wikipedia.org/wiki/Planck_time
http://en.wikipedia.org/wiki/Max_Planck
http://en.wikipedia.org/wiki/Planck_units
http://scienceworld.wolfram.com/physics/PlanckTime.html
http://en.wikipedia.org/wiki/Dimensional_analysis