What is the Bakken Formation?

The extent of the Bakken Formation, a subsurface formation within the Williston Basin. Credit:

There has certainly been a lot of talk over the past few decades about this thing known as the “energy crisis”. In essence, we’re being told that fossil fuels are running low, that we need to start thinking green and about alternative fuels and renewable resources.

However, there’s also been a lot of discussion about places like Alberta Tar Sands and other North American oil deposits, and how these might meet our energy needs for the foreseeable future. One such deposit is the Bakken Formation, a rock unit occupying about 520,000 km² (200773 square miles) of the Williston Basin, which sits beneath parts of Saskatchewan, Manitoba, Montana, and North Dakota.

On the geologic timescale, the rock formation is believed to date from the late Devonian to Early Mississippian age – from roughly 416 to 360 million years ago. It was discovered in 1953 by a geologist named J.W. Nordquist and named after Henry Bakken, owner of the Montana farm where Nordquist first drilled.

Schematic north-south cross section showing the Bakken and adjacent formations in 2013. Credit: USGS
Schematic north-south cross section showing the Bakken and adjacent formations in 2013. Credit: USGS

This rock formation consists of three members or strata: the lower shale, middle dolomite, and upper shale. Oil was first discovered there in 1951, but pumping it met with difficulties. This is due to the fact that the oil itself is principally found in the middle dolomite member – roughly 3.2 km (two miles) below the surface – where it is trapped in layers of non-porous shale, making the process both difficult and expensive.

While it was postulated as early as 1974 that the Bakken could contain vast amounts of petroleum, it wasn’t until Denver-based geologist Leigh Price did a field assessment for the U.S. Geological Survey (USGS) in 1995 that official estimates were made. Price estimated in 1999 that the Bakken Formation contained between 271 and 503 billion barrels of petroleum.

Impressive, yes? Well, keep in mind that the percentage of this oil that could actually be extracted is debatable. In 1994, estimates ranged from as low as 1% to Price’s estimate of 50%. A more recent report filed in 2008 by the USGS placed the amount at between 3.0 to 4.3 billion barrels (680,000,000 m3), with a mean of 3.65 billion.

Number of Bakken and Three Forks wells in the US as of 2013. Credit: energy.usgs.gov
Number of Bakken and Three Forks wells in the US as of 2013. Credit: energy.usgs.gov

By 2011, a senior manager at Continental Resources Inc. (CLR) raised that estimate to an overall at 24 billion barrels, claiming that the “Bakken play in the Williston basin could become the world’s largest discovery in the last 30–40 years”.

But reports issued by both the USGS and the state of North Dakota in April 2013 were more conservative, estimating that up to 7.4 billion barrels of oil could be recovered from the Bakken and Three Forks formations using current technology.

Still, this represents a significant increase from the estimates made back in 1995. Horizontal well and hydraulic fracturing technology have helped, adding about 70 million barrels of production in 7 years in Montana and North Dakota. By 2007, Saskatchewan was also experiencing a boom, producing five million barrels in that year, which was up 278,540 barrels in 2004.

Consistent with the US’ policy of achieving “energy independence”, analyst expect that an additional $16 billion will be spent to further develop the Bakken fields in 2015. The large increase in tight oil production is one of the reasons behind the price drop in late 2014, and keeping prices low is always politically popular.

North Dakota oil production. Credit: eia.gov
The North Dakota “oil boom”, represented by the state’s production per month and year. Credit: eia.gov

As more wells are brought online, production will continue to increase in places like North Dakota. While the rate of production per well appears to have peaked at 145 barrels a day since June of 2010, the number of wells has also doubled in the region between then and December of 2011.

The increase in oil and natural gas extraction has also had a profound increase on the economy of North Dakota. In addition to leading a reduction in unemployment, it has given the state a billion-dollar budget surplus and a GDP that is 29% above the national average. However, there has also been the resulting rise in pollution and the strain that industrialization and a population surge has put on the states’ water supply.

Will any of this solve the “energy crisis”? Hard to say. Because of the highly variable nature of shale reservoirs and shale drilling, and the fact that per-well rates seem to have peaked, it seems unlikely that total Bakken production will grow much further or affect the imports of foreign oil.

And given how the price of alternatives like solar, wind, geothermal and tidal energy are dropping all the time, one can expect that a fossil fuel-economy will become something of a fossil itself someday!

We have written many articles about the Bakken Formation for Universe Today. Here’s an article about Alternative Energy Sources, and here’s an article about harvesting solar power from space.

If you’d like more info on the Bakken Formation, check out the U.S. Geological Survey 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.

http://en.wikipedia.org/wiki/Bakken_Formation – cite_note-usgs.gov-3

What Is Solar Energy

Morning Sun

What is solar energy? Solar energy is the radiant energy produced by the Sun. It is both light and heat. It, along with secondary solar-powered resources such as wind and wave power, account for the majority of the renewable energy on Earth.

The Earth receives 174 petawatts(PW) of solar radiation at the upper atmosphere. 30% of that is reflected back to space and the rest is absorbed by clouds, oceans and land masses. Land surfaces, oceans, and atmosphere absorb solar radiation, which increases their temperature. Warm air containing evaporated water from the oceans rises, causing convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds and causes rain. The latent heat of water condensation increases convection, producing wind. Energy absorbed by the oceans and land masses keeps the surface at an average temperature of 14°C. Green plants convert solar energy into chemical energy through photosynthesis. Our food supply is completely dependent on solar energy. After plants die, they decay in the Earth, so solar energy can be said to provide the biomass that has created the fossil fuels that we are dependent on.

Humans harness solar energy in many different ways: space heating and cooling, the production of potable water by distillation, disinfection, lighting, hot water, and cooking. The applications for solar energy are only limited by human ingenuity. Solar technologies are characterized as either passive or active depending on the way the energy is captured, converted, and distributed. Active solar techniques use photovoltaic panels and solar thermal collectors to harness the energy. Passive techniques include orienting a building to the Sun, selecting materials with thermal mass properties, and using materials with light dispersing properties.

Our current dependence on fossil fuels is slowly being replaced by alternative energies. Some are fuels that may eventually become useless, but solar energy will never be obsolete, controlled by foreign powers, or run out. Even when the Sun uses up its hydrogen, it will produce useable energy until it explodes. The challenge facing humans is to capture that energy instead of taking the easiest way out by using fossil fuels.

We have written many articles about Solar Energy for Universe Today. Here’s an article about harvesting solar power from space, and here’s an article about the energy from the sun.

If you’d like more info on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We’ve also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.

Wise Geek

What Is Mechanical Energy

Millennium Force roller coaster Credit: Cedar Point
Millennium Force roller coaster Credit: Cedar Point


The straight forward answer to ‘what is mechanical energy’ is that it is the sum of energy in a mechanical system. This energy includes both kinetic energy(energy of motion) and potential energy(stored energy).

Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position. A few examples are: a moving car possesses mechanical energy due to its motion(kinetic energy) and a barbell lifted high above a weightlifter’s head possesses mechanical energy due to its vertical position above the ground(potential energy).

Kinetic energy is the energy of motion. An object that has motion, vertical or horizontal motion, has kinetic energy. There are many forms of kinetic energy: vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another).

Potential energy is the energy stored in a body or in a system due to its position in a force field or its configuration. The standard unit of measure for energy and work is the joule. The term “potential energy” has been used since the 19th century.

Because of the different components of mechanical energy, it exists in every system in the universe. From a baseball being thrown to a brick falling off of a ledge, mechanical energy surrounds us. Defining what is mechanical energy is easy, but finding examples of it are even easier.

We have written many articles about mechanical energy for Universe Today. Here’s an article about how generators work, and here’s an article about what is energy.

If you’d like more info on Mechanical Energy, check out a Discussion on Energy, and here’s a link to an article about Momentum.

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

What Is Light Energy

Lighting Up the Night
Lighting Up the Night


Just asking ‘what is light energy’ opens you up to a flood of other questions trying to narrow down the context that you are asking the question in. In photometry, luminous energy is the perceived energy of light. It can also be defined as the electromagnetic radiation of visible light. Since light itself is energy, then another definition is relevant: light is nature’s way of transferring energy through space.

The speed of light is about 300,000 km/s. To put that in perspective, when you watch the sun set, it has actually been 10 minutes since that light left the Sun. Light energy is measured with two main sets of units: radiometry measures light power at all wavelengths and photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception. Photometry is useful when measuring light intended for human use. The photometry units are different from most units because they take into account how the human eye responds to light. Based on this, two light sources which produce the same intensity of visible light do not necessarily appear equally bright.

Light exerts a physical pressure on objects in its path. This is explained by the particle nature of light in which photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by the speed of light. The effect of light pressure is negligible for everyday objects. For example, you can lift a coin with laser pointers, but it would take 1 billion of them to do it. Light pressure can cause asteroids to spin faster by working on them like wind pushing a windmill. That is why some scientist are researching solar sails to propel intersteller flight.

Light is all around us. It has the ability to tan or burn our skins, it can be harnessed to melt metals, or heat our food. Light energy posed a huge challenge for scientist up to the 1950’s. Hopefully, in the future, we will be able to use light energy and solar wind to travel among the stars.

We have written many articles about light energy for Universe Today. Here’s an article about the prescription for light pollution, and here’s an article about where visible light come from.

If you’d like more info on Light Energy, check out NASA’s Page on Atoms and Light Energy. And here’s a link to an article about How Photovoltaics Work.

We’ve also recorded an episode of Astronomy Cast all about Energy Levels and Spectra. Listen here, Episode 139: Energy Levels and Spectra.

Johns Hopkins University

What is a Joule?

When we raise an apple up to a height of one meter, we perform approximately one joule of work. So what is a joule?

Joule is the unit of energy used by the International Standard of Units (SI). It is defined as the amount of work done on a body by a one Newton force that moves the body over a distance of one meter. Wait a minute … is it a unit of energy or a unit of work?

Actually, it is a unit of both because the two are interrelated. Energy is just the ability of a body to do work. Conversely, work done on a body changes the energy of the body. Let’s go back to the apple example mentioned earlier to elaborate.

An apple is a favorite example to illustrate a one joule of work when using the definition given earlier (i.e., the amount of work done ….) because an apple weighs approximately one Newton. Thus, you’d have to exert a one Newton upward force to counteract its one Newton weight. Once you’ve lifted it up to a height of one meter, you would have performed one joule of work on it.

Now, how does energy fit into the picture? As you perform work on the apple, the energy of the apple (in this case, its potential energy) changes. At the top, the apple would have gained about one joule of potential energy.

Also, when the apple is one meter above its original position, say the floor, gravity would have gained the ability to do work on it. This ability, when measured in joules, is equivalent to one joule.

Meaning, when you release the apple, the force of gravity, which is simply just the weight of the body and equivalent to one Newton, would be able to perform one joule of work on it when the apple drops down from a height of one meter.

Mathematically, 1 joule = 1 Newton ⋅ meter. However, writing it as Newton ⋅ meter is discouraged since it can be easily confused with the unit of torque.

Particle physics experiments deal with large amounts of energies. That is why it is also known as high energy physics. If you liked our answer to the question, “What is a Joule?”, you might want to read the following articles from Universe Today:

Rare Binary Pulsars Provide High Energy Physics Lab
New Particle Throws Monkeywrench in Particle Physics
Physics World also has some more:
Particle physics: the next generation
To the LHC and beyond
Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:
The Large Hadron Collider and the Search for the Higgs-Boson

University of Wisconsin
University of Virginia

Electron Volt

Fermi mapped GeV-gamma-ray emission regions (magenta) in the W44 supernova remnant. The features clearly align with filaments detectable in other wavelengths. This composite merges X-ray data (blue) from the Germany/U.S./UK ROSAT mission, infrared (red) from NASA’s Spitzer Space Telescope, and radio (orange) from the Very Large Array near Socorro, N.M. Credit: NASA/DOE/Fermi LAT Collaboration, NASA/ROSAT, NASA/JPL-Caltech, and NRAO/AUI
Fermi mapped GeV-gamma-ray emission regions (magenta) in the W44 supernova remnant. The features clearly align with filaments detectable in other wavelengths. This composite merges X-ray data (blue) from the Germany/U.S./UK ROSAT mission, infrared (red) from NASA’s Spitzer Space Telescope, and radio (orange) from the Very Large Array near Socorro, N.M. Credit: NASA/DOE/Fermi LAT Collaboration, NASA/ROSAT, NASA/JPL-Caltech, and NRAO/AUI

From the name, electron volt, you might guess that this has something to do with electricity. Well, you’d be right, it does … but did you know that the electron volt is actually a unit of energy, like the erg or joule?

The symbol for the electron volt is eV – lower case e, upper case V. Like the meter, and parsec, the electron volt can have a prefix, so lots of electron volts can be written easily, so there’s a kilo-electron volt (keV, one thousand eV), mega-electron volt (MeV, one million eV), giga-electron volt (GeV, one thousand million eV), and so on.

About the energy the electron volt represents: if you accelerate an isolated electron through an electric potential difference of one volt, it will gain one electron volt of kinetic energy. Now a volt is a joule per coulomb, so an electron volt is one electric charge times one, or approx 1.6 x 10-19 joules (J).

Astronomers use electron volts to measure the energy of electromagnetic radiation, or photons, in the x-ray and gamma-ray wavebands of the electromagnetic spectrum, and also use electron volts to describe the difference in atomic or molecular energy states which give rise to ultraviolet, visual, or infrared lines, or limits. So, for example, the Lyman limit – which corresponds to the energy to just ionize an atom of hydrogen – is both 91.2 nm and 13.6 eV.

Now particle physicists use the electron volt, as a unit of energy too; however, confusingly, they also use it as a unit of mass! They do this by using the famous E = mc2 equation, so 1 eV – the unit of mass – is equal to 1 eV (the unit of energy) divided by c2 (c is the speed of light). So, for example, the mass of the proton is 0.938 GeV/c2, which makes the GeV/c2 a very convenient unit (= 1.783 x 10-27 kg). By convention, the c2 is usually dropped, and masses quoted in GeV.

Oh, and in some branches of physics, the eV is also a unit of temperature!

Would you like to read more on the electron volt? Try Energetic Particles (NASA), and How Big is an Electron Volt? (Fermilab).

Universe Today has many stories in which the electron volt features; here is a sample: Is a Nearby Object in Space Beaming Cosmic Rays at Earth?, Gamma-ray Afterglow reveals Pre-Historic Particle Accelerator, and Gamma Ray Bursts May Propel Fast Moving Particles.

The Astronomy Cast episode Gamma Ray Astronomy is a good example of electron volts in action.

NASA Science
GSU Hyperphysics

Martian Settlers May Need Chickens To Conquer The Red Planet

If humanity ever intends upon on settling Mars (by settling I mean a one way trip with no plans on returning back to Earth), they are going to need a whole lot of chickens if they want to survive–let alone thrive–upon the red planet.

Aside from providing an excellent source of protein, chickens could help future settlers raise not only crops (such as wheat, barely, etc.) upon the barren Martian soil, but also help colonists keep the lights on through a very useful by-product (aka chicken dung).

Unlike Earth, Martian dirt is very hostile towards plant life. Unless we can genetically alter plants to grow upon the red planets soil, future settlers will have to heavily rely upon the home world for their daily bread.

Future scientists could help reduce or (even better) eliminate that need by using chicken manure, which (as far as animal dung goes) has one of the highest concentration of nutrients available, making it a perfect choice for raising plants on Mars.

But providing food for plants isn’t the only reason why future Martian colonists will probably choose these ugly (yet useful) creatures, as chicken dung can also be used for energy as well.

Using an old scientific process called pyrolysis (which is cooking biomass like manure without the presence of oxygen), future settlers could turn this smelly chicken manure into biochar (which is a charcoal like product).

Just like many farmers on Earth, future colonists could turn biochar into bio-fuel, helping to power their future  space settlements along with Martian solar panels (or an underground nuclear reactor).

While other types of animals manure could also be used for raising crop or keeping the lights on, it would be much easier (not to mention cheaper) transporting chickens en mass than larger animals.

This is mainly due to the fact than an egg (averaging about 57 grams), weigh much less than say, a baby calf (which would weigh 32 kilograms at birth), making chickens the logical choice as far as future space animals go.

Although humans may eventually import other animals to Mars (whether for food or as pets), it may not be surprising to see chickens accompany future explorers in their quest to conquer the red planet.

Image Credit: Andrei Niemimäki via Flickr

Sources: New York Times, Ezine Articles, Wise Geek

Will Bio Fuels Power Martian Colonies Instead Of Solar?

If I told you that your great, great, great grandkids would be building houses on that crimson world known as Mars, what would be the first thought to enter your head?

Rovers? Check! A comfy Martian house? Check! Power cutting rock tools? (for us guys) Double check! A bio fuel gas tank? Che–huh?!

You’re probably wondering “what power on Earth would motivate you to bring bio fuels to Mars?” The answer: a slightly altered cyanobacterium that may help us power future Martian rovers, homes–and yes–power tools with good ol’ biofuel.

The problem with settling Mars is this: despite its dazzling desert environment (if you consider frozen dry tundra’s dazzling), Mars is not the most ideal location when it comes to the energy department.

The red planet receives approximately half of the sunlight Earth does, which may dim a green geeks hope of a solar powered outpost offworld.

Worse, even if solar panels received 100% of the energy from the Sun, those big, bad global dust storms could make solar panels useless for weeks or months at a time.

The only thing “big red” has to offer future settlers is rust, dust and lots of CO2–the latter which can be converted into fuel thanks to our new best (microscopic) friend cyanobacterium.

Scientists have been studying this little creature and have found that with a “few” alterations, cyanobacterium can take CO2 (the gas that can easily kill you) and turn it into a biofuel called isobutanol.

Converted, isobutanol could help colonists power rovers, Martian settlements–and yes, even power tools (as cutting rocks with lasers is going to require lots of energy folks!) without the need to depend upon the Sun or an underground miniature nuke (which might be too expensive for small outposts).

Since bio fuels can’t openly burn in the carbon atmosphere, future rovers, houses and power tools will need to be altered to also carry oxygen as well (which we could extract from the ever abundant Martian ice).

By having an inexpensive and (hopefully) cheap fuel, establishing homes and traveling the Martian globe could become a reality without the heavy (and sometimes “helpful”) hand from governments and mega-corporations.

Image Credit: Paul Hudson via NASA

Sources: Alternative Energy News, Physorg.com

Mini Nuclear Reactors Could Power Space Colonies

Growing up on Star Trek, I was always told that space was the final frontier. What they never told me was that space is about as friendly to the human body as being microwaved alive in a frozen tundra–in essence, shelter is a necessity.

Like any Earthen home or building, an off world shelter on the Moon or Mars will need energy to keep its residents comfortable (not to mention alive), and power outages of any sort will not be tolerated–unless a person desires to be radiated and frozen (which is probably not a great way to “kick the bucket”).

While some may look towards solar power to help keep the lights on and the heat flowing, it may be wiser instead to look at an upcoming “fission battery” from Hyperion Power Generation to power future colonies on the Moon, Mars, and perhaps an plasma rocket powered starship as well.

Originally created by Dr. Otis Peterson while on staff at the Los Alamos National Laboratory in New Mexico, Hyperion Power Generation (which I’ll call HPG for short) has licensed Dr. Peterson’s miniature nuclear reactor which are actually small enough to fit inside a decent sized hot tub.

Despite their small stature (being 1.5 meters by 2.5 meters), one of these mini-reactors could provide enough energy to power 20,000 average sized American homes (or 70 MW’s of thermal energy in geek speak) and can last up to ten years.

Since HPG is designing these mini-nuclear reactors to require little human assistance (the “little” having to do with burying the reactors underground), these “nuclear batteries” would enable NASA (or a wealthy space company) to power an outpost on the Moon or Mars without having to rely upon the Sun’s rays–at least as a primary source for power.

HPG’s mini-reactors could also help power future star ships heading towards Jupiter or Saturn (or even beyond), providing enough energy to not only keep the humans on board alive and comfortable, but provide enough thrust via plasma rockets as well.

Scheduled to be released in 2013, these mini-reactors are priced at around $50 million each, which probably puts it outside the price range of the average private space corporation.

Despite the cost, it may be wise for NASA, the European Space Agency, Japan, India and (if the US is in a really good trusting mood) China to consider installing one (or several) of these mini-reactors for their respective bases, as it could enable humanity to actually do what has been depicted in scifi films and television shows–seek out new homes on new worlds and spread ourselves throughout the universe.

Source: Hyperion Power Generation, Inc., Image Credit: NASA

How Many Atoms Are There in the Universe?

A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).

It’s no secret that the universe is an extremely vast place. That which we can observe (aka. “the known Universe”) is estimated to span roughly  93 billion light years. That’s a pretty impressive number, especially when you consider its only what we’ve observed so far. And given the sheer volume of that space, one would expect that the amount of matter contained within would be similarly impressive.

But interestingly enough, it is when you look at that matter on the smallest of scales that the numbers become the most mind-boggling. For example, it is believed that between 120 to 300 sextillion (that’s 1.2 x 10²³ to 3.0 x 10²³) stars exist within our observable universe. But looking closer, at the atomic scale, the numbers get even more inconceivable.

At this level, it is estimated that the there are between 1078 to 1082 atoms in the known, observable universe. In layman’s terms, that works out to between ten quadrillion vigintillion and one-hundred thousand quadrillion vigintillion atoms.

And yet, those numbers don’t accurately reflect how much matter the universe may truly house. As stated already, this estimate accounts only for the observable universe which reaches 46 billion light years in any direction, and is based on where the expansion of space has taken the most distant objects observed.

The history of theA billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions.universe starting the with the Big Bang. Image credit: grandunificationtheory.com
The history of the universe starting the with the Big Bang. Image credit: grandunificationtheory.com

While a German supercomputer recently ran a simulation and estimated that around 500 billion galaxies exist within range of observation, a more conservative estimate places the number at around 300 billion. Since the number of stars in a galaxy can run up to 400 billion, then the total number of stars may very well be around 1.2×1023  – or just over 100 sextillion.

On average, each star can weigh about 1035 grams. Thus, the total mass would be about 1058 grams (that’s 1.0 x 1052 metric tons). Since each gram of matter is known to have about 1024 protons, or about the same number of hydrogen atoms (since one hydrogen atom has only one proton), then the total number of hydrogen atoms would be roughly 1086 – aka. one-hundred thousand quadrillion vigintillion.

Within this observable universe, this matter is spread homogeneously throughout space, at least when averaged over distances longer than 300 million light-years. On smaller scales, however, matter is observed to form into the clumps of hierarchically-organized luminous matter that we are all familiar with.

In short, most atoms are condensed into stars, most stars are condensed into galaxies, most galaxies into clusters, most clusters into superclusters and, finally, into the largest-scale structures like the Great Wall of galaxies (aka. the Sloan Great Wall). On a smaller scale, these clumps are permeated by clouds of dust particles, gas clouds, asteroids, and other small clumps of stellar matter.

Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.
Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.

The observable matter of the Universe is also spread isotropically; meaning that no direction of observation seems different from any other and each region of the sky has roughly the same content. The Universe is also bathed in a wave of highly isotropic microwave radiation that corresponds to a thermal equilibrium of roughly 2.725 kelvin (just above Absolute Zero).

The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle. This states that physical laws act uniformly throughout the universe and should, therefore, produce no observable irregularities in the large scale structure. This theory has been backed up by astronomical observations which have helped to chart the evolution of the structure of the universe since it was initially laid down by the Big Bang.

The current consensus amongst scientists is that the vast majority of matter was created in this event, and that the expansion of the Universe since has not added new matter to the equation. Rather, it is believed that what has been taking place for the past 13.7 billion years has simply been an expansion or dispersion of the masses that were initially created. That is, no amount of matter that wasn’t there in the beginning has been added during this expansion.

However, Einstein’s  equivalence of mass and energy presents a slight complication to this theory. This is a consequence arising out of Special Relativity, in which the addition of energy to an object increases its mass incrementally. Between all the fusions and fissions, atoms are regularly converted from particles to energies and back again.

Atom density is greater at left (the beginning of the experiment) than 80 milliseconds after the simulated Big Bang. Credit: Chen-Lung Hung
Atom density is greater at left (the beginning of the experiment) than 80 milliseconds after the simulated Big Bang. Credit: Chen-Lung Hung

Nevertheless, observed on a large-scale, the overall matter density of the universe remains the same over time. The present density of the observable universe is estimated to be very low – roughly 9.9 × 10-30 grams per cubic centimeter. This mass-energy appears to consist of 68.3% dark energy, 26.8% dark matter and just 4.9% ordinary (luminous) matter. Thus the density of atoms is on the order of a single hydrogen atom for every four cubic meters of volume.

The properties of dark energy and dark matter are largely unknown, and could be uniformly distributed or organized in clumps like normal matter. However, it is believed that dark matter gravitates as ordinary matter does, and thus works to slow the expansion of the Universe. By contrast, dark energy accelerates its expansion.

Once again, this number is just a rough estimate. When used to estimate the total mass of the Universe, it often falls short of what other estimates predict. And in the end, what we see is just a smaller fraction of the whole.

We’ve got a many articles that are related to the amount of matter in the Universe here in Universe Today, like How Many Galaxies in the Universe, and How Many Stars are in the Milky Way?

NASA also has the following articles on the universe, like How many galaxies are there? and this article on the Stars in Our Galaxy.

We also have podcast episodes from Astronomy Cast on the subject of Galaxies and Variable Stars.