The History of the Universe in 40 Minutes:

From Big Bang to Heat Death

Michael Bleiweiss
Presented to the Ethical Society of Boston
4 June 2006

Updated 10 August 2019

0. Abstract

13.7 billion years ago, the Universe was formed in the great Big Bang explosion. This led to the formation of galaxies, stars, and planets, including our own little earth. This lecture reviews our knowledge of this history, obtained through centuries of observation and physics theory.

Michael Bleiweiss is a physicist, engineer, and computer professional who has been interested in astronomy since childhood. His favorite places to go were the dinosaur halls and the planetarium in the New York Museum of Natural History.

I. Opening Words

This quotation is from The Hitchhiker's Guide to the Galaxy by Douglas Adams.

"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to he chemist, but that's just peanuts to space."

II. Introduction

In this talk, I will attempt to cover the entire history of the Universe from the Big Bang to Heat Death. Throughout this discussion, I have separated out the more technical background information as footnotes.

Before I begin, I need to give you a quick math lesson. Don't worry, this is all stuff you've already seen back in school. In order to describe the history of the Universe, we will need to use some very small and some very large numbers. Physicists do this using Scientific Notation. In Scientific Notation, numbers are represented as powers of 10.  In a power of ten, a number is written as 10{x}. That x value is called the exponent, where the number in the exponent represents the number of zeros to put after the "1". For example:

10⁰ = 1 followed by no zeros = 1
10¹ = 1 followed by one zero = 10
and so on.

For numbers less than one, a negative exponent is used. This represents the fraction 1/10 to the power. For example:

and so on.

I also need to mention the units that are used to describe distance in the Universe. The primary unit is called a light year, which is equal to the distance that light travels in one year. This comes to 5.88 trillion (5.88 x 10¹²) miles or 9.46 trillion (9.46 x 10¹²) kilometers). You might also hear of a unit called a parsec, which is equal to 3.26 light years 1.

Finally, you will hear references to temperatures in Kelvins. A Kelvin is defined as a temperature scale with degrees the same size as the Centigrade scale (= (°F - 32) * 5/8) and starting at absolute zero, which equals -273°C (-459°F).

The events detailed in this talk were derived from a combination of astronomical observations, calculations based on experiments in particle physics and nuclear physics, and the theory of General Relativity. This has led to a model that is consistent with observations in both fields -- the very large and the very small. That said, many of the fine details are still under contention. Because of time constraints, I will skip over details on the history of these discoveries and calculations.

III. The Big Bang

Current research indicates that the Universe began 13.7 billion years ago (13.7 x 10⁹ in scientific notation) in a cataclysmic event called the Big Bang. It is not known what existed beforehand or why the event occurred when it did 2. Also, we are only able to calculate back to a certain point in time before which our knowledge of physics breaks down.

In the beginning, the Universe was contained in a near single point of near infinite density in a form called a singularity.

At 10^-50 seconds, the Universe was at a temperature of about 10³⁵ K.  At this point, all four known physical forces were all merged into one unified force 3.  These forces were:  the strong (nuclear) force, electromagnetic forces, the weak interaction (which controls the decay of neutrons and muons), and gravity.

At about 10^-42 seconds, the Universe had cooled to 10³² K and gravity "separated" out from the other forces. This is known as "breaking of the symmetry."

At about 10^-37 seconds, it entered a supercooled state, that is, a condition where it would normally have undergone a quantum mechanical phase transition, but couldn't. This created a "false vacuum" -- an energy state higher than the true vacuum of normal space. The energy fields in this false vacuum then caused the Universe to experience a period of extremely rapid expansion called inflation, during which it grew by a factor of 10³⁰ -- from 10^-30 meters to 1 meter in a period of 10^-35 seconds ^{4, 5}. This expansion caused the energy density of the fields to drop until space underwent the phase transition into a true vacuum. The energy released by this phase transition then created all of the particles in the Universe.

However, in order for stars and galaxies to form, we need to have some variations in density on smaller scales so that concentrations of matter can collect under the pull of gravity. It turns out that these were caused by random variations in the rate of inflation that caused it to end at slightly different times in different locations. Where the inflation ended later, matter was slightly denser than where it ended earlier. These differences had a magnitude of only 1 part in 10,000, but that was sufficient to create the complex structures that we observe today.

Inflation has an intriguing implication. The portion of the Universe that we can observe is limited by the distance that light can travel in the time it has existed (about 10 - 20 billion light years). It is likely that, prior to the inflationary period, the Universe was about the size that light would have traveled up to that time. The rapid expansion during inflation implies that the entire Universe might actually be up to 10²³ times larger than what we can see!

There is an alternate model where inflation continues indefinitely. In this scenario, each time the energy density in a local region drops sufficiently, a local universe is created. Here, our Universe might be one of an infinite number in a hyper-universe.

Then, at 10^-34 seconds, when the Universe cooled to about 10²⁷ K, the strong force separated from the electro-weak force. At this point, subatomic particles were able to form, but it was still much too hot for protons and neutrons to exist. All matter existed as a "soup" of quarks 6, leptons (electrons, muons, taus, and neutrinos), and photons (radiation).

At 10^-10 seconds, at a temperature of 10¹⁵ K, the weak and electromagnetic forces separated from each other, so that all four forces were now distinct.

By 10^-6 seconds, at a temperature of 10¹³ K, the Universe was finally cool enough for the quarks to start "condensing" into protons and neutrons. However, the overwhelming bulk of the mass of the Universe was in the form of radiation (as photons). There were also large amounts of other particles including electrons, positrons, neutrinos, and anti-neutrinos.

At 0.1 second after the Big Bang, when the Universe was at 31.5 billion K, the density of the Universe dropped sufficiently for neutrinos to stop interacting strongly with other particles 7 and start traveling freely. Most of these neutrinos are probably still around, but their energy is so low (equivalent to a temperature of 1.95 K) that they cannot be detected. On the other hand, the remaining particles were still interacting with each other quite vigorously, forming, annihilating, and being converted into each other.

By one second, the temperature fell to 10 billion K. At this temperature, the energy ⁸ becomes too low for electron-positron pairs to form so that their mutual annihilation becomes dominant (this process took a while to complete -- another 30 seconds). It was also at this point that the nuclear particles -- protons and neutrons -- became stable and achieved their present-day ratio. However, it was still much too hot for actual nuclei to form.

It should be pointed out that it is still not fully understood why our Universe consists of protons and electrons and not their anti-particles. However, it would only require 1 extra matter quark out of 300 million total quarks to achieve the current amount of matter observed.

Nuclei could finally began to form at around 1 minute, when the temperature dropped below 1 billion K. Only the three lightest elements were produced in measurable quantity -- Hydrogen (75%), Helium (25%), and Deuterium (0.03%) by mass.  At this point, the evolution of the Universe begins to slow down.

By 300,000 years, the Universe had expanded to 90 million light years and cooled enough (4,000 K) for the atomic nuclei and electrons to start combining into neutral atoms. This meant that the radiation (photons) would now stop interacting with the sub-atomic particles and be able to travel freely through space. This is referred to as decoupling. This process lasted until the Universe was about 1 million years old.

The remnants of this are seen in the 2.7 K microwave background radiation that is observed to come from all directions in space 9. The reason that the apparent temperature has dropped is because as the Universe expands, the radiation gets "stretched," making the wavelength longer, which then corresponds to lower frequencies and energy ¹⁰. An alternate way of looking at it is that the Universe cools as it expands. This radiation is almost completely uniform in all directions. Recent, very precise, satellite measurements have detected variations of 1 part in 100,000. This is very important because it provides evidence of the small variations in density that ultimately led to all of the complex structure that now exists.

The blackbody radiation spectrum of the microwave background is shown in Figure 1. A map of the variations in the background temperature, as obtained by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite are shown in Figure 2. A summary of the above discussion is shown in Figures 3.

Figure 1. 2.7K Blackbody Spectrum.      Figure 2. Variations in Microwave Background
                                                                                 Radiation Temperature.
 

Figures 3. Evolution of the Universe.  (Used by permission of Prof. Hale Bradt - M.I.T.)
 

Some may ask, "Doesn't the creation of the Universe violate the law of conservation of energy" (which states that energy can neither be created nor destroyed). The answer to this is that the gravitational potential energy is actually a negative energy. This is because it is "trying" to pull the Universe back in to a point. The sum of the energy contained in the matter (from E = mc²) plus the gravitational potential energy add up to zero.

It should be mentioned at this point that visible matter appears to constitute only 10% of the matter in the Universe. The remaining 90% consists of a mysterious form of dark matter that can only be detected due to its gravitational influence on the visible matter. Indeed, it controls the dynamics of galaxy formation and motion. Galaxies have a "halo" of dark matter that extends out to 10 times their visible extent.

As mentioned previously, there were small variations in the density of matter after inflation. Once decoupling occurred, the attractive force of gravity became greater than the repulsive force due to the pressure of the photons bumping into everything. Therefore, the slightly denser regions started to attract surrounding material into them. These density variations occurred at two scales. The first was at 100,000 times the mass of the sun (referred to as solar mass), which happens to be the mass of a typical globular cluster (clusters of stars that orbit the galaxies). The second was at 10¹² solar masses, which correspond to the sizes of large galaxies and small galactic clusters.

This collapse was not uniform or monotonic. Irregularities in the distribution and velocity of matter would have caused the collapsing clouds to be flattened. Interactions between the gas molecules would have induced turbulence, which would have caused heating. This, in turn, would have caused forming clouds to break up and then reform as the collapse continued. As this progressed, the clouds condensed into galaxies, which then attracted to form clusters of galaxies, and eventually, clusters of clusters (this clustering continues into the present). The first proto-galaxies would have formed when the Universe was about 500 million years old and coalesced over a period of about 100 million years.

There are two modes of galaxy formation. In the first, galaxies of about 10¹¹ solar masses (about the size of our Milky Way) form directly. This is because the physics of collapsing gas clouds favor this size. In this case, non-uniformities in the collapse cause the new galaxies to form as flat disks. Then, tidal forces from nearby forming galaxies combined with gravitational forces from the dark matter halo cause them to rotate and become spiral galaxies.

In the second mode, small, irregular galaxies form that, over time, tend to collide and merge. Here, their respective angular momenta tend to cancel out, causing them assume a more elliptical form 11. These collisions also caused bursts of new star formation as their constituent gas clouds collided, creating regions of high density. Typical spiral and elliptical galaxies are shown in Figures 4 and 5.

Figure 4. Spiral Galaxy Andromeda Galaxy M32.     Figure 5. Elliptical Galaxy NGC 3610.

In both cases, galaxies continue to grow into the present day by accreting new gas from their halos and intergalactic space. Pictures of colliding galaxies are shown in Figures 6. However, there is also an effect counteracting this. As galaxies collide and/or interact, stars in the outer reaches of a galaxy (known as the "halo") and gas are driven out into intergalactic space. This can also be seen in the figure. The force of supernova explosions also drives gas out of the galaxy proper.

                NGC 4038/4039                                 NGC 5426/5427

Figures 6. Colliding Galaxies. (Pictures by the Hubble Space Telescope).

A consequence of this pattern of growth, combined with the initial density distribution, is that galaxies appear to concentrate along filaments and sheets around the universe with large voids occupying much of space. This is shown in Figure 7.

Figure 7. Distribution of Galaxies in the Local Universe (160 Mpc).

When galaxies form, their cores assemble first. In addition, as they evolve, material tends to concentrate at their center. The resulting extremely high density of stars and stellar remnants leads to a high rate of collision. This, in turn, leads to the formation of a massive black hole at the centers of most galaxies. These can range in size from 2 million to 3 billion solar masses. At first, these are very "active" since, as material falls into them, huge amounts of energy in the form of radiation is released. Over time, the immediate vicinity of the black hole is depleted of material and things quiet down.  An image of a black hole at the center of the Galaxy M87 is shown as Figure 8. The galaxy itself is shown in Figure 9. An artist's conception of a black hole is shown in Figure 10.
 

Figure 8. Image of Black Hole at Center Figure 9. M87 Galaxy.
of M87 Galaxy.

Figure 10. Artist's Conception of a Black Hole.

The continuation of this process at smaller and smaller scales within the galactic clouds led to the formation of star-sized aggregations, which then collapsed to form the first stars. The oldest stars detected formed at about 2.5 billion years.

Initially, the high concentration of gas allowed many stars to form over a short period of time. At that early time, the physics of how gas clouds collapse ¹² favored very large, short lived stars. These went supernova, throwing most of their mass back into space. This went on for several generations over about 100 million years until, as the concentration of heavier elements in interstellar space increased, the formation of smaller, longer-lived stars became favored instead ¹³. The Orion Nebula -- a typical star-forming region in our galaxy is shown in Figures 11.

Figures 11. Orion Nebula M42.

The process quickly used up the gas in the galaxies, so that the rate of star formation dropped off radically. Star production seems to have peaked at about 5 billion years and has been dropping off ever since. This is shown in Figure 12.

Figure 12. Rate of Star Formation vs. Age of the Universe.

Over the past couple of decades, precision measurements have identified several thousand planets around other nearby stars (exoplanets), indicating that they are a common phenomenon ¹⁴. That said, only a tiny fraction appear to be capable of supporting life as we know it.

Stars generate their heat and light from nuclear reactions inside their cores.  There they "burn" hydrogen into helium through the process of nuclear fusion. When the hydrogen is exhausted, the star starts burning the helium into carbon, nitrogen, and oxygen. After that, heavier elements are produced up until iron, which is the heaviest element for which fusion will release energy rather then consume it.

The elements heavier than iron are produced during supernova explosions, where a massive star violently throws off most of its mass, forming a neutron star or black hole from the remnant 15. Therefore, all of the elements heavier than helium were produced by stars and released into space by their nova and supernova explosions. A chart of life history of stars as a function of their initial mass is shown in Figure 13.

Figure 13. Fates of Stars as a Function of Mass.  (from The Big Bang by Joseph Silk)

Currently, spiral galaxies are about 3% gas. Most of that is from material thrown off by stars through their stellar winds, novae, and supernovae. In contrast, elliptical galaxies have lost almost all of their gas. This is because stars form sooner there and the violent explosions expel the gas more efficiently. Consequently, star formation there has effectively ceased and their stars are mostly older.

I will mention parenthetically here that our sun system formed when the Universe was about 10 billion years old. As a medium-sized star, our sun is expected to burn for another 5 billion years from now. At that time, it will expand to be larger than the Earth's orbit. Eventually, it will go nova and become a white dwarf.

Recent observations indicate that the expansion of the Universe may be accelerating ¹⁶. This appears to be due to a sort of negative gravity called dark energy ¹⁷, which appears to be due to a sort of potential energy in the fabric of space-time. This acceleration appears to have begun about 5 billion years ago. Up until that time, the force of gravity was stronger than the dark energy. Then the Universe reached a critical size and the strength of the dark energy exceeded that of gravity. It should be noted that this is not universally accepted as established by astronomers.

Figure 14 shows a field of galaxies from the Hubble Space Telescope Deep Field Survey.

Figure 14. Picture from Hubble Deep Field Survey.

So, that brings us up to the present. The Universe is about 14 billion years old and contains an estimated 50 billion of galaxies, each with tens to hundreds of billions of stars. Stars are born and die. But, what lies in our future? Even without the dark energy, the measured mass of the Universe is only a fraction of what would be required for it to collapse again. These two factors mean that the Universe will probably continue to expand forever.

IV. Mid-Lecture Joke

A friend suggested that I keep my audience awake by inserting a joke in the middle of my talk.

I wish to report the tragic death of two particle physicists. They had gone to an Italian restaurant for lunch. One of them ordered pasta. Without thinking, the other ordered antipasto. When their meals arrived, they annihilated, killing them both.

V. Future Evolution

In 1996 a group of physicists at the University of Michigan performed a calculation on the future evolution of the Universe. What follows is highly speculative and strongly dependent on our current theoretical understanding of particle physics. I will try to point these out as I proceed.

We currently live in the Stelliferous Era, the period in which stars dominate the appearance and energy budget of the Universe.

As mentioned previously, the smaller (i.e., lighter) a star, the longer its lifetime. An average star such as our sun has a lifetime of about 10 billion years. To bring the discussion closer to home, our sun is currently about halfway through its lifetime. In about 5 billion years, it will have consumed most of its hydrogen and will expand into a red giant. Current calculations indicate that in the process, it will throw off about 30% of its mass, causing the Earth's orbit to increase enough to move it out of range. Even so, if you have any urgent projects, you should get to them soon.

A star with 1/10 of a solar mass will last about 10¹³ years -- 1,000 times longer than our sun. Such lower-mass stars eventually use up all of their fuel and become white dwarves and then slowly cool into dark stellar remnants.

As stars are created and die, the amount of hydrogen in the Universe will slowly be depleted and replaced with heavier elements. Over about 10¹² years, the abundances will approach the following: hydrogen ~20%, helium ~60%, and other elements ~20% 18. In addition, the amount of gas available for star formation will be depleted as more and more material becomes tied up inside of dead stars (brown dwarves ¹⁹, white dwarves, neutron stars, and black holes). After about 10¹⁴ years, there will no longer be enough material for new stars to form.

The lightest of the last stars to form will live for another 10¹³ years, bringing the end of the period of living stars at about 10²⁷ years.

Again, closer to home, our galaxy and the Andromeda galaxy, which are currently orbiting each other 2.5 million light years apart, will eventually collide. This will probably be at some time between 6 x 10¹⁰ and 10¹² years.

Once star formation has ended, the Universe will enter the Degenerate Era which starts at 10¹⁵ years and lasts until 10³⁰ years. This period is characterized by a number of phenomena.

As stars move in their orbits through a galaxy, occasionally two brown dwarves will collide, providing enough mass for them to ignite into small stars. This effect will be small, though, producing only a few hundred stars per galaxy.

Most stars and stellar remnants will merely pass near each other. Over time, their mutual gravitational influence will tend to "slingshot" them out of the galaxy, so that eventually over 90% of the galaxy will evaporate, leaving just the central core region at about 10²⁰ years. The remaining objects will eventually drop into the central black hole that exists at galactic cores. This will take until about year 10³⁰.

These black holes in the clusters and superclusters of galaxies will undergo a similar effect. Many of them will be ejected from the supercluster and other will merge together to form even larger black holes.

It was mentioned earlier that 90% of the mass in galaxies appears to be a mysterious form of dark matter. One model posits a new type of particle called weakly interacting massive particles, or WIMPs. Over time, these will be slowly absorbed by the stellar remnants until they are depleted at about year 10²⁵. The captured WIMPs will tend to collide with each other and annihilate over time. The energy from this will eventually be radiated away as photons. The theory for this is extremely speculative.

The following is also very speculative. Many grand unified theories assert that the proton is not stable, but will decay over long periods of time. Currently, experiments show the proton half-life to be at least 10³² years ^{20, 21}. Calculations also indicate that this value is probably less than 10⁴¹ years. The paper that this analysis is based on splits the difference and uses 10³⁷ years. Proton decay can take many paths, but the end products are always photons of gamma ray energies ²², electrons, and neutrinos. In addition, the neutrons in the atoms decay into protons, electrons, and (anti)neutrinos.

As protons decay inside a stellar remnant, the emitted photons heat it up, but not by much. For a typical white dwarf, proton decay would provide about 400 watts of power, which will raise its temperature to about 0.06 K. Over time, the star will slowly evaporate until, after about 10³⁸ years, it disappears completely.

Neutron stars undergo a similar evaporation. Neutron stars are not pure neutrons. The outermost layer is ordinary matter. Therefore, the protons that are in this outer shell begin to decay. As it loses mass, the density of the star drops until it is converted completely into ordinary matter. At this point, it follows a similar path as the white dwarves.

The Universe will then enter the Black Hole Era, from 10³⁸ to 10¹⁰⁰ years. During this period, the black holes will also evaporate over time.

This occurs via a mechanism called Hawking Radiation 23. This is a quantum mechanical process where pairs of virtual subatomic particles are spontaneously created at the edge of the black hole ²⁴. Usually, they will almost immediately annihilate. However, sometimes one will fall back into the black hole and the other one will escape, taking its mass with it. The larger the black hole, the longer this process takes. A small, star-sized black hole would disappear in about 10⁶⁵ years. A typical central galactic black hole with a mass of 1 million solar masses would take about 10⁸³ years to completely evaporate.

The result of all of the above processes is that by about 10¹⁰⁰ years, much of the Universe would be made up of photons, neutrinos, electrons, positrons, and the remaining WIMPs. As expansion continues, the density of these particles decreases and the Universe becomes colder and colder until it is a tiny fraction of a degree above absolute zero.

This then leads to the period referred to as the Dark Era. Events during this era become even more speculative and depend on the physical model used.

Space is not completely empty. Despite its name, the vacuum actually contains a sea of subatomic particles that continually come into existence and then almost immediately disappear. This produces an energy field throughout space. If this field is strong enough, then it might push the Universe into another inflationary period. This would have the effect of isolating the clusters of galaxies as they fly apart due to the expansion of space. Depending on the strength of the field, this could occur as early as year 10³⁰.

If inflation does not occur and the mass in the Universe is large enough, then large-scale variations in the structure of space may cause particles to come together to form new black holes that would then emit Hawking radiation. In addition, as subatomic particles such as electrons and positions occasionally encounter each other, they will annihilate, creating small amounts of gamma rays.

VI. Ending Joke

In the movie Hannah and her Sisters, Woody Allen's character as a young boy is troubled about our sun going nova and destroying all life on earth. His mother takes him to a therapist, who tells him that it won't happen for another 5 billion years, so it's nothing that we have to worry about.

VII. Closing Words

This song is taken from the movie "The Meaning of Life" by Monty Python
Analysis     Video Clip

Whenever life gets you down, Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious, or daft,
And you feel that you've had quite enough,

Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the 'Milky Way'.

Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.

The universe itself keeps on expanding and expanding
In all of the directions it can whiz
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.

VII. References

The Inflationary Universe. Alan A. Guth. Addison-Wesley Publishing Co, Inc. 1997.

The Extravagant Universe. Robert P. Kirshner. Princeton University Press. 2002.

An exposition on the history of the discovery of dark energy.

The Big Bang. Joseph Silk. W.H. Freeman & Co. 2001.

A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects. Fred C. Adams and Gregory Laughlin, University of Michigan. Reviews of Modern Physics. Vol. 69, pg. 337-372 (April 1997).

Very Distant Supernovae Suggest that the Cosmic Expansion is Speeding Up. Bertram Schwarzschild. Physics Today, June 1998. pg. 17-19.

Lonely Universe. Ron Cowen. Science News. V 162. 31 August 2002. pg. 139-40.

Cosmic Revelations: Satellite Homes in on the Infant Universe. Science News. V. 163. 15 February 2003. pg. 99-100

For very brief summaries of the future history of the Universe, see:

Hubble Space Telescope Pictures and Information

Hubble Space Telescope Pictures and Information: http://HubbleSite.org

Andy Kravtsov: Distribution of Galaxies and Clusters.

University of Chicago

New date for initial star formation:
Steve Nadis. New Scientist 181.2435 (Feb 21, 2004): p32(4).
 

Images:

Spiral Galaxy: Andromeda Galaxy = M31: Adam Evans
https://upload.wikimedia.org/wikipedia/commons/9/98/Andromeda_Galaxy_%28with_h-alpha%29.jpg

Elliptical Galaxy: NGC 3610: Hubble Telescope
https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2015/2-hubbleviewsa.jpg

Colliding Galaxies NGC 4038/4039: Hubble Space Telescope
https://HubbleSite.org/contents/media/images/1997/34/538-Image.html?keyword=NGC%204038

Colliding Galaxies NGC 5426/5427: Hubble Space Telescope
https://HubbleSite.org/contents/media/images/1997/34/536-Image.html?keyword=NGC%205426

M87* Galactic Black Hole - New Horizons Telescope Collaboration - NSF
https://phys.org/news/2019-04-astronomers-unveil-photo-black-hole.html
 

M87 Galaxy: NASA
https://www.nasa.gov/sites/default/files/thumbnails/image/m87-full_jpg.jpg

Artist's Conception of Black Hole:
Science Made Stupid. Tom Weller. Houghton Mifflin Co. Boston. 1985.

2.7K Blackbody Microwave Spectrum: The Microwave Background. Michael Richmond.
Article: http://spiff.rit.edu/classes/phys240/lectures/cmb/cmb.html
Image: http://spiff.rit.edu/classes/phys240/lectures/cmb/firas_spectrum.jpg

Microwave Background Radiation Variation: NASA
Article: https://science.nasa.gov/ems/06_microwaves
Image: https://smd-prod.s3.amazonaws.com/science-pink/s3fs-public/thumbnails/image/microwave-7.jpg

Evolution of Universe Graphs: Prof. Hale Bradt. Physics Dept. Massachusetts Institute of Technology.

Orion Nebula Full: http://www.astrocruise.com/milky_way/M42_0712.htm - Philip Perkins 12/13/2007

Orion Nebula Close up: http://spaceref.com/astronomy/the-orion-nebula.html
- NASA Spitzer Science Center 07/23/2013

Rate of Star Formation Since Big Bang: NASA & ESA
Article: https://www.SpaceTelescope.org/images/opo9832m
Image: http://cdn.SpaceTelescope.org/archives/images/screen/opo9832m.jpg

 

VIII. Footnotes

1. The parsec is defined as the distance required for an angle of 1" to spread out to a separation equal to the diameter of the Earth's orbit (184 million miles). back

    

2. There is an extension of String Theory that posits a "hyper-universe" containing of a set sheets called "M-branes." The theory states that when two of these collide, it results in a release of energy that causes a universe to form. back

    

3. There are a set of theories called "Grand Unified Theories" (or GUT) that describe the behavior of sub-atomic particles. An essential part of these is the principle that, as particle energy increases, the forces that we observe as separate "merge" together. A branch of thermodynamics known as Statistical Mechanics equates temperature with the average speed of a group of particles (usually atoms and molecules at everyday conditions). Since speed converts to kinetic energy, particle energy can be equated to an equivalent temperature. back

    

4. The energy of the false vacuum was contained in quantum fields called Higgs Fields. These are generated by the recently discovered particle called the Higgs boson, which is attributed with creating the mass of all of the particles. Its estimated mass is 125 GeV, which is at the limit of the world's largest particle accelerator at CERN in Geneva, Switzerland. back

    

5. Intellectual honesty requires me to state that these numbers are only approximate. The values depend critically on the specific Grand Unified Theory that is used in making the calculations. That said, the concept of inflation helps to explain why the Universe is so uniform on a large scale -- if it was approximately uniform to begin with, the rapid expansion enhances the uniformity. back

    

6. A quark can be thought of as a sub-sub-atomic particle. Protons and neutrons are each made up of 3 quarks. The name is derived from a line in the James Joyce novel Finnegan's Wake: "Three quarks for Muster Mark." back

    

7. Neutrinos interact extremely weakly with other matter. It is estimated that a typical neutrino could travel through 3,500 light years of rock before being stopped. back

8. When a sub-atomic particle and it's anti-particle collide, they annihilate each other, releasing a burst of high-energy gamma ray photons. Electrons and positrons have a mass-energy equivalent of 0.511 MeV. back

9. This radiation was discovered in 1964 by Arno Penzias and Robert Wilson at Bell Labs when they were trying to determine the source of "noise" in their radio telescope. It had also been predicted theoretically by a number of physicists in the 1950s and early 1960s. Penzias' and Wilson's measurements provided confirmation to their calculations. back

    

10. For electromagnetic radiation, the energy in a photon = E = h/2(π)(λ), where λ = wavelength and h = Plank's Constant = 6.626 x 10-27 erg-second. back

     

11. This process tends to occur mostly in large clusters of galaxies where there is a massive central galaxy. Spiral galaxies tend to form within sparse groups. It should be noted that small irregular galaxies and globular clusters will also form in these sparse groups. However, here they are much less likely to collide. back

12. As a gas cloud collapses, it heats up. This increases the pressure, which then slows the collapsing process. Hydrogen gas cools very inefficiently. In order to lose energy, their electron must be bumped up to a higher energy state via collisions with other atoms. They will then emit a photon when the electron drops back down into its "ground state," releasing the energy out into space. It turns out that this causes the resulting final stellar cloud to be more massive. back

     

13. As more elements were released into space, more energy levels became available to radiate energy out of the collapsing clouds. This then allowed them to break up into smaller units and form smaller stars. back

14. We cannot actually see planets around other stars. Rather, a dimming of the star's light is observed as a planet transits across its face or the star's position wobbles as the planet orbits around it. back

15. Stars lighter than about 6 solar masses go nova when they have exhausted all of their nuclear fuel, leaving stellar remnants lighter than 1.4 solar masses, becoming white dwarves. These are held up by the natural fermi repulsion between electrons. Stars between 30 and 50 solar masses throw off most of their mass in a supernova, leaving a remnant between 1.4 and 2.2 solar masses, becoming neutron stars. Here, the gravitational forces are so great that the electrons and protons are forced together to become neutrons. They are then held up by the fermi repulsion between the neutrons. Stars heavier than that produce remnants with masses greater than 2.2 solar masses and become black holes, whose gravity is so great that even light cannot escape. back

16. How do we know about how the Universe is expanding? This is done by measuring the spectra of the stars in very distant galaxies. You can think of the Universe as being the surface of a balloon that is being blown up. Points that are further around on the balloon will move away from us more quickly. Also, as they move away from us, the light they emit gets "stretched," causing its wavelength to become longer, which makes it appear redder. This is known as the red shift. We can then tell how far away they are by making various brightness measurements and comparing them to the known brightness of similar objects that are closer. This process would require an entire additional lecture to describe fully. back

     

17. When Albert Einstein first developed the General Theory of Relativity in 1916, it was before Edwin Hubble's discovery in the 1920s that the Universe was expanding. Therefore, Einstein added a Cosmological Constant as a countervailing force to gravity over very large distances to explain why the Universe didn't collapse on itself. He later described it as his "greatest mistake." However, this discovery shows that his initial equation was correct, but for the wrong reason. back

     

18. In astrophysics, any elements heavier than Helium are referred to as metals and their abundance is referred to as metalicity. back

     

19. Brown dwarves are protostars that are too light to begin nuclear fusion, generally < 0.08 solar masses. back

     

20. The tests for proton decay consist of tanks containing tens of thousands of gallons of ultra-pure water buried deep underground where they are shielded from external energy sources such as cosmic rays (high energy nuclei) gamma rays. back

     

21. A half life is the length of time that it takes for half of the nuclei or sub-atomic particles in a sample to decay. back

     

22. Gamma rays from particle decay typically have energies of 5x10⁵ to 5x10⁸ eV. An electron volt (eV) is the kinetic energy possessed by an electron that has been accelerated through a 1 volt potential. back

     

23. Named after British physicist Stephen Hawking, who first advanced the theory in 1974. back

     

24. This phenomenon is due to the Heisenberg Uncertainty Principle. This states that the product of the uncertainty in a particle's energy and lifetime must be greater than Plank's Constant (h = 6.63×10^-34 J·s = 4.14×10^-15 eV·s) divided by 2π. That is ΔE x Δt >= h/2π. The consequence of this is that a particle can spontaneously come into existence without violating conservation of energy as long as it disappears again quickly enough. back

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