16 posts · 6,815 views
The mad ramblings of a theoretical astrophysicist.
Brian Koberlein
16 posts
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- December 19, 2009
- 08:44 AM
- 564 views
Non-Singular Black Holes
by Brian Koberlein in Upon Reflection
The basic model of a black hole can be summed up as follows: gravity wins. The root cause of all black holes—be they tiny primordial black holes, solar mass black holes, or supermassive galactic black holes—is gravity. Squeeze enough mass...... Read more »
Mbonye, M., & Kazanas, D. (2005) Nonsingular black hole model as a possible end product of gravitational collapse. Physical Review D, 72(2). DOI: 10.1103/PhysRevD.72.024016
- December 14, 2009
- 11:41 AM
- 503 views
Beyond the Farthest Star
by Brian Koberlein in Upon Reflection
Figure 1: The Orion Constellation. (Source: APoD) When you look up into the night sky, you are seeing into the past. Cosmic distances are so vast that it takes time for light to travel them. Light from the closest star...... Read more »
Zhang, B. (2009) Astrophysics: Most distant cosmic blast seen. Nature, 461(7268), 1221-1223. DOI: 10.1038/4611221a
- February 3, 2010
- 07:45 AM
- 501 views
The Attraction of Curves
by Brian Koberlein in Upon Reflection
Figure 1: Newton's gravity predicts an elliptical orbit for Mercury (similar to the red path). Mercury's orbit actually shifts over time (similar to the path in blue). Mercury's motion agrees with Einstein's model of gravity. (Source: Wikipedia) Last time I...... Read more »
Dyson, F., Eddington, A., & Davidson, C. (1920) A Determination of the Deflection of Light by the Sun's Gravitational Field, from Observations Made at the Total Eclipse of May 29, 1919. Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character (1896-1934), 220(1), 291-333. DOI: 10.1098/rsta.1920.0009
- December 5, 2009
- 10:50 PM
- 447 views
Fiat Lux
by Brian Koberlein in Upon Reflection
Nature, and Nature's Laws lay hid in Night. God said "Let Newton be!" and all was Light.— Alexander Pope In 1671, Isaac Newton submitted a letter to the the Royal Society outlining a new theory of light and color. While...... Read more »
Newton, I. (1753) A Letter of Mr. Isaac Newton, Professor of the Mathematicks in the University of Cambridge; Containing His New Theory about Light and Colors: Sent by the Author to the Publisher from Cambridge, Febr. 6. 1671/72; In Order to be Communicated to the R. Socie. Philosophical Transactions (1665-1678), 6(1), 3075-3087. DOI: 10.1098/rstl.1671.0072
- February 10, 2010
- 03:17 PM
- 435 views
Expanding Universe
by Brian Koberlein in Upon Reflection
Figure 1: Two models of Newton's universe. Newtonian gravity predicts that stars were packed together tightly in the beginning, and expanded out into space. Over time, the stars either would collapse back together or expand forever. (Source: John D. Norton)...... Read more »
Hubble, E. (1929) A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae. Proceedings of the National Academy of Sciences, 15(3), 168-173. DOI: 10.1073/pnas.15.3.168
- April 2, 2010
- 01:23 PM
- 428 views
It Goes to Eleven
by Brian Koberlein in Upon Reflection
Note: This entry is a bit different from most of my posts. It is more mathematical, and uses MathML extensively to display equations. If you see gibberish instead of equations, then your browser isn't capable of viewing them. If you...... Read more »
Geraci, A., Smullin, S., Weld, D., Chiaverini, J., & Kapitulnik, A. (2008) Improved constraints on non-Newtonian forces at 10 microns. Physical Review D, 78(2). DOI: 10.1103/PhysRevD.78.022002
- February 17, 2010
- 07:10 PM
- 420 views
Pop Goes the Pulsar
by Brian Koberlein in Upon Reflection
Note: This entry is a bit different from most of my posts. It is more mathematical, and uses MathML extensively to display equations. If you see gibberish instead of equations, then your browser isn't capable of viewing them. If you...... Read more »
HEWISH, A., BELL, S., PILKINGTON, J., SCOTT, P., & COLLINS, R. (1968) Observation of a Rapidly Pulsating Radio Source. Nature, 217(5130), 709-713. DOI: 10.1038/217709a0
- January 19, 2010
- 11:01 AM
- 419 views
Dark Materials
by Brian Koberlein in Upon Reflection
Figure 1: A plot of the speed of stars in the Milky Way vs their distance from the galactic center. The top line represents the actual speed distribution of stars, while the bottom line represents what the motion should be...... Read more »
Law, D., Majewski, S., & Johnston, K. (2009) EVIDENCE FOR A TRIAXIAL MILKY WAY DARK MATTER HALO FROM THE SAGITTARIUS STELLAR TIDAL STREAM. The Astrophysical Journal, 703(1). DOI: 10.1088/0004-637X/703/1/L67
- December 17, 2009
- 11:22 AM
- 418 views
Don't Try This At Home
by Brian Koberlein in Upon Reflection
Electricity plays a central role in our modern lives. It lights our homes, starts our cars, and runs the computer from which you read this journal. It's hard to believe that not long ago we knew almost nothing about this...... Read more »
Franklin, B. (1753) A Letter of Benjamin Franklin, Esq; to Mr. Peter Collinson, F. R. S. concerning an Electrical Kite. Philosophical Transactions (1683-1775), 47(1), 565-567. DOI: 10.1098/rstl.1751.0096
- December 29, 2009
- 02:37 PM
- 416 views
Point of View
by Brian Koberlein in Upon Reflection
Figure 1: Tycho's model of the cosmos. The solar system revolves around a fixed Earth, which is all surrounded by the celestial sphere of stars. (Source: Wikipedia) When you look at the night sky it is easy to imagine that...... Read more »
Miller-Jones, J., Jonker, P., Dhawan, V., Brisken, W., Rupen, M., Nelemans, G., & Gallo, E. (2009) THE FIRST ACCURATE PARALLAX DISTANCE TO A BLACK HOLE. The Astrophysical Journal, 706(2). DOI: 10.1088/0004-637X/706/2/L230
- December 7, 2009
- 11:12 AM
- 413 views
Black Holes, Brownian Motion
by Brian Koberlein in Upon Reflection
If you've ever watched dust-motes dancing in a sunbeam then you've observed Brownian motion. It is the jerky, fluttering motion of particles in fluids such as air or water. The botanist Robert Brown first described the motion in detail. He...... Read more »
Merritt, D., Berczik, P., & Laun, F. (2007) Brownian Motion of Black Holes in Dense Nuclei. The Astronomical Journal, 133(2), 553-563. DOI: 10.1086/510294
- January 6, 2010
- 07:52 AM
- 401 views
Astronomical Units
by Brian Koberlein in Upon Reflection
Figure 1: Aristarchus measured the angle between the Sun and the Moon when the moon was half full, then used trigonometry to measure the distance to the Sun. (Source: Wikipedia) In an earlier post I wrote about how astronomers can...... Read more »
Hirst, W. (1769) Account of Several Phaenomena Observed during the Ingress of Venus into the Solar Disc. By the Reverend W. Hirst, F. R. S. in a Letter to the Astronomer Royal. Philosophical Transactions (1683-1775), 59(1), 228-235. DOI: 10.1098/rstl.1769.0031
- December 15, 2009
- 05:38 PM
- 400 views
Time Traveller
by Brian Koberlein in Upon Reflection
Figure 1: Ron Mallett. (Source: UConn Advance) Ron Mallett wants to build a time machine. He's wanted to build one for a long time, ever since his father died of a heart attack when Mallett was 10 years old. Since...... Read more »
Mallett, Ronald L. (2003) The Gravitational Field of a Circulating Light Beam. Foundations of Physics, 33(9), 1307-1314. DOI: 10.1023/A:1025689110828
- January 13, 2010
- 07:40 AM
- 389 views
And Yet It Moves
by Brian Koberlein in Upon Reflection
Figure 1: A painting of the trial of Galileo, by Cristiano Banti. (Source: UMKC) A famous story in the history of science is that of the trial of Galileo Galilei. Galileo believed that the Earth moved around the Sun, but...... Read more »
Foucault, M. (1851) Physical demonstration of the rotation of the earth by means of the pendulum. Journal of the Franklin Institute, 51(5), 350-353. DOI: 10.1016/0016-0032(51)90993-3
- January 11, 2010
- 07:41 AM
- 345 views
Some Like It Hot
by Brian Koberlein in Upon Reflection
Figure 1: Sir Charles Blagden. (Source: Wikipedia) We humans are warm blooded creatures. This mammalian characteristic helps us to live in a range of environments from warm to cold, but it also means our bodies must have a way to...... Read more »
Blagden, C. (1775) Further Experiments and Observations in an Heated Room. By Charles Blagden, M. D. F. R. S. Philosophical Transactions (1683-1775), 65(1), 484-494. DOI: 10.1098/rstl.1775.0048
- December 11, 2009
- 01:42 PM
- 316 views
A Shot in the Arm
by Brian Koberlein in Upon Reflection
Cold and flu season has hit the Rochester area recently, as evidenced by the recent uptick in the number of students missing class on account of colds and flu. Fortunately there are ways to minimize your chances of getting a...... Read more »
Sloane, H., & Birch, T. (1755) An Account of Inoculation by Sir Hans Sloane, Bart. Given to Mr. Ranby, to be Published, Anno 1736. Communicated by Thomas Birch, D. D. Secret. R. S. Philosophical Transactions (1683-1775), 49(1), 516-520. DOI: 10.1098/rstl.1755.0073
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