Cosmology is the area of physics that studies the universe in and of itself. Through the use of incredible and ingenious methods of experimentation, cosmologists attempt to discover how the universe began, how it is developing, and how or if it will end. Questions regarding the Big Bang, dark matter, dark energy, the cosmic background radiation, and the initial formation of the fundamental particles can be placed into this category.

3,306 Questions

Is the Big Rip theory true?

At the moment The Big Rip is still a hypothesis. It is all to do with the amount of dark energy in the Universe. Until this is confirmed, it is impossible to say whether it is true or not.

The ultimate fate of the Universe is not entirely known. We know that the universe will continue expanding at an accelerating rate, but it is unknown what this will result in. It is very possible that the outward expansion will result in all particles flying apart from one another as the force of expansion will overcome the forces holding atoms together. However, that will depend on exactly what Dark Energy is. Dark Energy is responsible for the expansion of the universe, but this is just a placeholder name for what really causes it- the nature of dark energy is currently unknown.


What are the types of galaxies?

The main types of galaxies are Spiral galaxies, Elliptical galaxies, Lenticular galaxies, and Irregular galaxies.

  • Spiral (and Barred-Spiral) galaxies are shaped like pinwheels, with arms that spiral outward. The barred spiral has an elongated bar shape across the middle. Examples of the spiral are our own Milky Way and Andromeda. A barred spiral is the Sculptor Galaxy.
  • Elliptical galaxies look like flattened spheres rather than the thinner spiral form. They are observed to have comparatively little interstellar matter. An example is the Maffei 1 galaxy.
  • Lenticular galaxies are flattened galaxies without an obvious spiral structure. An example is the Spindle Galaxy in Draco.
  • Irregular galaxies do not have any of the common shapes, and may have been disrupted by various forces. These include Hoag's Galaxy (a ring), the Magellanic Clouds, and NGC 1427A (which is speeding toward the Fornax cluster).

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What cosmological inference can you draw from the darkness of the night sky?

This is another way of asking about "Olbers' Paradox", developed in the 19th century byan astronomer named Heinrich Olbers.He sought to answer: (back when this was widely held to be true) if the universe is both infinite in space and eternal in time, why is the night sky dark?

Given our SpaceTime, it is possble that eventually everywhere you look should have a star (like looking into a sufficiently large grove of trees and seeing trees in all directions). Yet there are limitations to such observations. First, the universe appears to be of finite age and that light from stars at an infinite distance would not have reached us in the age of the universe. Second, we observe that the universe is expanding and that stars further away from us are receding at a faster rate. The result of this expansion is that the light from more distant stars is Doppler shifted more toward the red and beyond a certain distance would not contribute significantly in the visible region of the electromagnetic spectrum.

If the Universe were to be consideredaccording to Steady State Theory, thenwe should be able to see a star anywhere in the night sky, and so the sky should have the same brightness everywhere; every point in the night sky should have a star, or cluster of stars there to put out enough light to rival daylight. From the absence of such nocturnal light :

You could infer that the stars are not evenly distributed throughout the universe, but must be 'clumped', with voids between the clumps, and thatevery line of sight could only terminate on the surface ofthese stars.

You could also infer that the universe is not consistent with the Steady State Theory.

Comment: The "standard" explanation is based on the Big Bang Theory.
Without going into the details of the argument, these are the most important
facts that are involved:

1) The Universe began about 13.7 billion years ago (according to data extrapolated from measurements on our small portion ofthe observable universe)
2) The Universe is expanding (according to data extrapolated from measurements on our small portion of the observable universe)
3) The speed of light is finite according to the Theory of Relativity

However, this problem still causes some disagreement amongst astronomers
and there are "minority" viewpoints that differ from the majority opinion.
Details of the arguments are given on Wikipedia under "Olbers' Paradox".


Is Dark Matter good for building muscle?

Dark Matter has got nothing to do with building muscle! It's "stuff" that may not even exist!

It's usually ok, just be careful of spontaneous black holes and blinking out of existence.

Another view: If dark matter does exist and has the properties postulated by cosmologists, then it would be no good for building muscle. It interacts so weakly with ordinary matter that you would be unable to lift it - it would pass right through you.

Earth Sciences
Nuclear Physics

What are the stars all about?

The sun we have is a star. Just the closest to us.


What is the density of a stony iron meteorite?

Iron meteorites account for about 5% of all meteorites that fall to earth, they are likely to be either Kamacite or Taenite. The density of these minerals is 7.9 and 7.8-8.22 g/cm3 respectively.

Black Holes

Are black holes high density objects?

Yes and No - While the current measure for the mass of a black hole is based on an indirect measuring of the speed of the orbiting material, there is no direct measuring of the density of a black hole.

Density is a concept involving mass divided by volume. While one can abstract the mass of a black hole, measuring the volume is a little tricky. We know there is a boundary at the Schwarzschild radius (Schwarzschild horizon) and this is also called the event horizon. Bascially, anything that happens beyond that point is unknown to us. Supermassive black holes have properties which distinguish them from lower-mass classifications. First, the average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be less than the density of water in the case of some supermassive black holes. This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object (such as the event horizon of a non-rotating black hole) is directly proportional to the cube of the radius, the density of a black hole is inversely proportional to the square of the mass, and thus higher mass black holes have lower average density.

To complicate things even more, space-time is highly distorted around a black hole, so even asking how big it is, adds further complexity to this answer. Nonetheless, black holes have a mass and size. However one can not know if the mass inside is accreted all at one point or more spread out and distibuted. It appears the inner dynamics of the black hole provide for a plasma like accretion disk, which that pretty much changes (or distorts) our traditional dimensional frame of reference. It could be that the black hole merely suspends acquire mass in a medium of energy state. Consequently this medium of energy may preclude its growth or shrinkage.

India Colleges and Universities
All India Engineering Entrance Examination AIEEE

Do there is any course of cosmology in IITs?


Big Bang Theory (scientific model)

What was the Big Bang and when did it occur?

The Big Bang occurred an estimated 13.7 billion years ago.

It was not a giant explosion into existing space, as many people are lead to believe. Rather, it was the very rapid expansion of the fabric of the Universe known as "spacetime." The irony is that the "Big Bang" was neither big nor loud by conventional standards.

Prior to the Big Bang, our Universe existed in an extremely small, hot and dense state known as a singularity. We don't know how or why the Universe came into existence, but that is not what the Big Bang is about. Instead the Big Bang was the event that happened immediately after this singularity somehow came into being.

Anyway, the Universe was so hot that the four fundamental forces we know of today (gravity, electromagnetism, the strong and weak nuclear forces) behaved the same way and functioned as one "Superforce." Suddenly, for reasons yet unknown, gravity split off from this force, triggering the Universe's extremely rapid expansion. In less than a second, the Universe grew from smaller than an atom to the size of the Solar System, and expanding ever larger.

As the Universe grew it became cooler and less dense as energy spread out. Energy was converted into quarks, electrons, and other subatomic particles, which further came together to form atomic nuclei. Eventually the Universe cooled down enough for electrons to become bound to the nuclei forming the first true atoms. The Universe was now filled with vast clouds of hydrogen and helium, the lightest and most abundant elements. These clouds would eventually coalesce through gravity to form stars and galaxies.

The question was, how could the Universe be so tiny, smaller than an atom? Einstein's theory of general relativity discovered that spacetime is collapsible, and can actually be warped and folded around itself. To visualize inflation, picture a paper map crumpled into a tiny ball. Then imagine the map is suddenly pulled out in all directions so that it unfolds and becomes a flat sheet. That's what the Big Bang was: the expansion and flattening of spacetime.

There is abundant evidence that the Big Bang occurred and it fits the full range of observations made by astronomers. Most commonly mentioned are the expansion of the Universe and the cosmic microwave background. For the full range of evidence, see the related link below. Today the Big Bang theory is the most widely accepted model in the scientific community for the early development of the Universe.

For more info see the related questions and links


An Alternative Theory -- Steady State Theory

There is also another Theory, which Maxwell, Einstein, Hoyle, and hundreds of other Astrophysicists and Astronomers believed in wholeheartedly, known as the Steady State Theory. A theory which you probably have never heard of in your many years of public education.

In the Big Bang Theory all known laws of physics have to be thrown out, and a new Superforce, Exotic Matter, Dark Matter, and dozens of Alternate Dimensions had to be invented to make the theory work properly. And even with throwing out all of the known laws of physics - it still does not work, because the Universe is not old enough to explain the universal standardized temperature throughout the universe. In short: the temperature should not be this uninformed, or this cold.

In the Steady State Theory the Universal Primordial Atom (the singularity) was not a single super-hot atom-sized point of existence, in an non-existent universe. Instead, it is a Universe sized atom of Bose/Einstein Condensate: Known as the Ether.

Bose/Einstein Condensate is liquid Hydrogen frozen at absolute zero Kelvin. When Hydrogen is frozen at absolute zero Kelvin, all molecules begin to vibrate in unison, and acts, reacts, and behaves as one single atom - regardless of the size of the condensate (a singularity).

The Big Bang, under the Steady State Theory, happens when an impurity in the condensate (such as an unstable element's decay) causes the Condensate to warm, melt, and outgas. This outgassing causes expansion.

If the heating and outgassing is sufficiently large enough, a Nebula, Solar Nursery, and solar system protoplanetary disk is created, forming Gas Giants, which become suns - once they reach critical mass. This causes more heating, outgassing, and expansion: resulting in more solar systems.

In the theory of stellar nucleosynthesis all other elements and matter are created in the massive gravity and superheated conditions found within the heart of these new suns. As suns die and explode, these elements are scattered across the universe.

Eventually, some suns grow so massive, that they develop a gravity so great, that light itself cannot escape. These are known as Black holes.

According to the Steady State Theory, all matter in the Universe will eventually fall into a Black Hole, and these Black Holes will collide and merge into a single, or a small number of, Black Holes in the universe. These Black Holes strip atoms down to their base elements... Tearing them down into Hydrogen again, and eventually down into a soup of electrons, neutrons, and protons: which are the only thing small enough, and moving fast enough, to escape the polar regions of the Black Holes - filling the Universe with the raw elements needed to form the Hydrogen which then cools to absolute zero again to form a Bose/Einstein Condensate Primordial Atom again.

According to the Steady State Theory, the accidental discovery of cosmic microwave background radiation in 1965, by Arno Penzias and Robert Woodrow Wilson, is not hearing the Big Bang - but rather hearing the continued outgassing of the Bose/Einstein Condensate along the outer rim of the universe, as the outgassing causes the universe to continue to expand.

It explains the extra energy causing the continuation of expansion, which the big bang theory cannot without inventing exotic matter.

It explains why the universe's temperature has reached uniformity, and such a cold temperature. By starting out at absolute zero Kelvin, the universe did not have to lower its temperature by 100's of thousands of degrees, it simply had to rise three degrees Kelvin.

It also allows for wormholes, without the need of multiple dimensions and the folding of space in upon itself (Research: "fountains in Bose/Einstein Condensates"). And opening a wormhole would only require the power from a transistor battery: Not hundreds of suns. Making interstellar space travel not only possible, but simple.

It also throws great disparaging results on red shift methods of measurements. A Bose/Einstein Condensate has the ability to slow light down to one mile an hour, without changing any elements of the light itself. So if you are measuring how far away a star is, based on the red shift of the light from the star, and that light is passing through Bose/Einstein Condensate during its journey, the light is no longer traveling at the speed of light: It may be traveling a hundred years at one mile an hour. So, the light's red shifts one hundred years, but it never traveled 100 light years to get here...

Which explains why, when our satellites look back at our own Sun from out near Neptune, our sun is barely able to be seen. If the light fades so quickly within a fraction of a single light year - why can we see any light at all from stars hundreds of light years away? Could it be they are millions of times closer than we think? Because Bose/Einstein Condensate slowed the light to one mile an hour, for hundreds of years...

And finally, under the Big Bang Theory, the Universe will end in a BIG RIP: where the suns will eventually run out of fuel, the galaxies will all go dark, the galaxies will all drift apart, and the Universe will grow cold and die.

Under the Steady State theory, the Universe will never die. The local galaxies will eventually fall into the Black Holes in the center of each Galaxy. The Black Holes will strip the Electrons, Neutrons, and Protons from all matter, and spew them out into the Universe, to be recycled back into a new Condensate.

In the meanwhile, the Universe continues to expand, creating new solar nurseries: so while one hemisphere dies off and is recycled, another hemisphere of the Universe is thriving and continually expanding. This means the Universe is in a steady state of existence.

From a religious standpoint: If light is introduced to a Bose/Einstein Condensate - it causes warming, outgassing, and the creation of the Universe... So, the Universe could have easily been created by the simple introduction of "Let there be light."


Does dark matter exist on earth?

With our present understanding of dark matter -- ie, we don't exactly what it is -- we would have no way of knowing how much dark matter exists within the confines of our planet. Because dark matter has (by definition) almost no interaction with the stuff our Earth is made of, we can't detect its presence here. If and when we find out what the stuff is, we can then make a reasonable determination of how much is here on our planet.

Well dark matter is what cause our fabric of space time that cause gravitational pull of our earth eventually dark matter is everything!!

Planetary Science
Planet Earth

What causes Earth's day and night cycle?

The rotation of Earth about its axis.

Related Information:

Each day, Earth spins one full turn. So the part that faces the sun is always changing. While the sun is shining on one half of the earth (day), the other half is shaded from the sun (night).

Nuclear Physics
Electromagnetic Radiation
Thermodynamics and Statistical Mechanics

What are the best physics project topics?

The best physics project topics to study depends on what you find interesting.

If you find everyday things like motion, pendulums, and collisions interesting, study mechanics.

If you find things like optics, circuits, and electricity interesting, study electromagnetism.

If you find things like statistics, temperature, and entropy interesting, study thermodynamics.

If you find things like time dilation, the speed of light, and black holes interesting, study relativity.

If you find things like the universe, dark matter, and star formation interesting, study cosmology, astrophysics, and nuclear physics.

If you find things like particles, accelerators, atomic bombs and unified force theories interesting, first study quantum mechanics, then study nuclear and particle physics.

If you meant what are the best physics project topics to do as a science experiment, use the guidelines I stated above, but stick to the first three topics; mechanics, electromagnetism, and thermodynamics.


How many stars are in the universe?

Based on current estimates, there are between 200 - 400 billion stars in our galaxy (The Milky Way). There are possibly 100 billion galaxies in the Universe. So taking the average of our galaxy, gives approximately 3 x 1024 stars. So about 3 septillion. This has been equated to the same number of grains of sand that are on Earth.

One source (BBC) stated that there are about 1,000 stars to every grain of sand on Earth!! There are an estimated 100 to 200 billion galaxies.

So taking a conservative number of 100 billion stars per galaxy gives an approximate total of 10,000,000,000,000,000,000,000 stars. (Which is 10 sextillion)

The newest estimates gained by the Hubble space telescope places the estimate of 500 billion Galaxies each with about 300 billion stars for each galaxy.

Big Bang Theory (scientific model)

Did God exist before or after the Big Bang?

God has existed ever since people began to believe in him. Like all gods, when there is no one to believe in him, God would cease to exist.


How large is our universe is it endless?

In a sense, yes Its impossible to conceptualize how large the universe is. Our Galaxy contains over 400 billion stars and its diameter is about 100,000 light years. There are hundreds of billions of Galaxies in our universe and its constantly expanding. Its impossible to really know how large the universe, is but for all intents and purposes, yes it is endless.

Modern cosmology also believes there is no edge, and speculates that it may wrap around on itself. Just like you can walk forever on a globe without hitting an edge or turning.


What conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

The actual presence of the gas cloud's contents will absorb certain wavelengths of Light, preventing the passage of certain photons through the cloud, that results in that Light not reaching us - producing a blank line in the observed spectrum.


What is unit of light called?

A unit of light is called a photon.



Dark energy is an unexplained force that is causing?

Dark Energy is an unexplained theoritical mathematical quantity that is proposed to account for the apparent steady increase in the rate of expansion of the universe.


How the age of the universe can be calculated using the big bang model?

By noting how rapidly galaxies are flying apart from each other, and how far apart they are now, we can calculate how far back in time it was that they started to fly apart. No different than the question, "Since the time Pat and Sam both began their journey at the same point on the highway, they have traveled at a speed of 100 kilometers per hour. They are now 200 kilometers apart. How long have they been traveling apart from each other?"

The present calculations of the age of the Universe by this method -- about 13.7 billion years -- agree quite well with other calculations, that were derived in a totally independent manner.


What is everything known about the universe and the method used to explain them and is in one word?

Cosmology is defined as

the science of the origin and development of the universe.

an account or theory of the origin of the universe.

Job Training and Career Qualifications
College Degrees
Bachelors Degrees

What is the educational requirement for a cosmology?

Cosmology falls under the fields for Physicists and Astronomers. Therefore, the following is written by and according to the U.S. Department of Labor and particular to the education and training required for Physicists and Astronomers.

Because most jobs are in basic research and development, a doctoral degree is the usual educational requirement for physicists and astronomers. Master's degree holders qualify for some jobs in applied research and development, whereas bachelor's degree holders often qualify as research assistants or for jobs in other fields where a physics background is good preparation, such as engineering and technology.

Education and training. A Ph.D. degree in physics or closely related fields is typically required for basic research positions, independent research in industry, faculty positions, and advancement to managerial positions. Graduate study in physics prepares students for a career in research through rigorous training in theory, methodology, and mathematics. Most physicists specialize in a subfield during graduate school and continue working in that area afterwards.

Additional experience and training in a postdoctoral research appointment, although not required, is important for physicists and astronomers aspiring to permanent positions in basic research in universities and government laboratories. Many physics and astronomy Ph.D. holders ultimately teach at the college or university level.

Master's degree holders usually do not qualify for basic research positions, but may qualify for many kinds of jobs requiring a physics background, including positions in manufacturing and applied research and development. Increasingly, many master's degree programs are specifically preparing students for physics-related research and development that does not require a Ph.D. degree. These programs teach students specific research skills that can be used in private-industry jobs. In addition, a master's degree coupled with State certification usually qualifies one for teaching jobs in high schools or at 2-year colleges.

Those with bachelor's degrees in physics are rarely qualified to fill positions in research or in teaching at the college level. They are, however, usually qualified to work as technicians or research assistants in engineering-related areas, in software development and other scientific fields, or in setting up computer networks and sophisticated laboratory equipment. Increasingly, some may qualify for applied research jobs in private industry or take on nontraditional physics roles, often in computer science, such as systems analysts or database administrators. Some become science teachers in secondary schools.

Holders of a bachelor's or master's degree in astronomy often enter an unrelated field where their strong analytical background provides good preparation. However, they are also qualified to work in planetariums running science shows, to assist astronomers doing research, and to operate space-based and ground-based telescopes and other astronomical instrumentation.

Many colleges and universities offer a bachelor's degree in physics. Undergraduate programs provide a broad background in the natural sciences and mathematics. Typical physics courses include electromagnetism, optics, thermodynamics, atomic physics, and quantum mechanics.

Approximately 190 universities offer Ph.D. degrees in physics; more than 60 additional colleges offer a master's as their highest degree in physics. Graduate students usually concentrate in a subfield of physics, such as elementary particles or condensed matter. Many begin studying for their doctorate immediately after receiving their bachelor's degree; a typical Ph.D. program takes about 6 years to complete.

About 75 universities grant degrees in astronomy, either through an astronomy, physics, or combined physics-astronomy department. About half of all astronomy departments are combined with physics departments, while the remainder are administered separately. With about 40 doctoral programs in astronomy, applicants face considerable competition for available slots. Those planning a career in the subject should have a strong physics background. In fact, an undergraduate degree in either physics or astronomy is excellent preparation, followed by a Ph.D. in astronomy.

Many physics and astronomy Ph.D. holders begin their careers in a postdoctoral research position, in which they may work with experienced physicists as they continue to learn about their specialties or develop a broader understanding of related areas of research. Initial work may be under the close supervision of senior scientists. As they gain experience, physicists perform increasingly complex tasks and achieve greater independence in their work. Experience, either in academic laboratories or through internships, fellowships, or work-study programs in industry, also is useful. Some employers of research physicists, particularly in the information technology industry, prefer to hire individuals with several years of postdoctoral experience.

Other qualifications. Mathematical ability, problem-solving and analytical skills, an inquisitive mind, imagination, and initiative are important traits for anyone planning a career in physics or astronomy. Prospective physicists who hope to work in industrial laboratories applying physics knowledge to practical problems should broaden their educational background to include courses outside of physics, such as economics, information technology, and business management. Good oral and written communication skills also are important because many physicists work as part of a team, write research papers or proposals, or have contact with clients or customers who do not have a physics background.

Certain sensitive research positions with the Federal Government and in fields such as nuclear energy may require applicants to be U.S. citizens and to hold a security clearance.

Advancement. Advancement among physicists and astronomers usually takes the form of greater independence in their work, larger budgets, or tenure in university positions. Others choose to move into managerial positions and become natural science managers. Those who pursue management careers spend more time preparing budgets and schedules. Those who develop new products or processes sometimes form their own companies or join new firms to develop these ideas.

For the source and more detailed information concerning your request, click on the related links section (U.S. Department of Labor) indicated directly below this answer section.

How To

How to study the dark region of universe?

The only way we can study distant parts of the universe is through photons emitted from those regions.

By definition, if it is "dark" then we cannot study it. W can only study its interactions with light that we can see.

Big Bang Theory (scientific model)

How was the big bang theory tested?

The theory predicts an omni-present, isotropic microwave radiation with a spectrum equal to that of a 3.7 K black-body. That is exactly what we detect, and no other hypothesis can explain it other than saying, "It's there but I have no way to explain why."

It predicts that far away galaxies will be much younger than those close to us. This is indeed what we observe.

It predicts a specific ratio of hydrogen to helium to deuterium in every part of the Universe. What we see is exactly as predicted. Again, all other hypotheses can only say, "That's the way it is, but I can't explain why."


Where can you buy big bang Pegasus?

It will be released in the future at Walmart or target and toys r us or if you want to get it right now.... you can buy it at Ebay or Amazon


How does the big bang theory serve as an unifying theme in cosmology?

It accounts for the beginnings of both space and time in the universe.


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