Ganymede and Callisto are similar in size and are made of a similar mixture of ice and rock, but data from the Galileo and Voyager spacecraft show that they look different at the surface and on the inside. Just like Earth and Venus, Ganymede and Callisto are twins, and understanding how they were born the same and grew up to be so different is of tremendous interest to planetary scientists.
Ganymede and Callisto’s evolutionary paths diverged about 3.8 billion years ago during the Late Heavy Bombardment, the phase in lunar history dominated by large impact events. Impacts during this period melted Ganymede so thoroughly and deeply that the heat could not be quickly removed. All of Ganymede’s rock sank to its center the same way that all the chocolate chips sink to the bottom of a melted carton of ice cream. Callisto received fewer impacts at lower velocities and avoided complete melting. Ganymede is closer to Jupiter and therefore is hit by twice as many icy impactors as Callisto, and the impactors hitting Ganymede have a higher average velocity.
Image Credit: NOAA/GSD
A plug for a buddy of mine!
Announcing the publication of *Science and Religion: 5 Questions* edited by Gregg D. Caruso—a collection of interviews with thirty-three of the world’s leading philosophers, scientists, theologians, apologists, and atheists.
Description: Are science and religion compatible when it comes to understanding cosmology (the origin of the universe), biology (the origin of life and of the human species), ethics, and the human mind (minds, brains, souls, and free will)? Do science and religion occupy non-overlapping magisteria? Is Intelligent Design a scientific theory? How do the various faith traditions view the relationship between science and religion? What, if any, are the limits of scientific explanation? What are the most important open questions, problems, or challenges confronting the relationship between science and religion, and what are the prospects for progress? These and other questions are explored in Science and Religion: 5 Questions—a collection of thirty-three interviews based on 5 questions presented to some of the world’s most influential and prominent philosophers, scientists, theologians, apologists, and atheists.
Contributors: Contributors include a Nobel Prize winning physicist, three Templeton Prize winners, two “Humanist of the Year” winners, the “Most Influential Rabbi in America” (Newsweek, 2012), “the leading American expert on Tibetan Buddhism” (New York Times), a National Humanities Medal winner, a National Medal of Science winner, a Star of South Africa Medal winner, a Carl Sagan Award winner, a National Science Board’s Public Service Medal winner, a MacArthur Fellow, a Lakatos Award winner, an Erasmus Prize winner, a “Friend of Darwin Award” winner, a “Distinguished Skeptic Award” winner, the first Muslim to deliver the prestigious Gifford Lectures, and many more.
Simon Blackburn, Susan Blackmore, Sean Carroll, William Lane Craig, William Dembski, Daniel C. Dennett, George F.R. Ellis, Owen Flanagan, Owen Gingerich, Rebecca Goldstein, John F. Haught, Muzaffar Iqbal, Lawrence Krauss, Colin McGinn, Alister McGrath, Mary Midgley, Seyyed Hossein Nasr, Timothy O’Connor, Massimo Pigliucci, Rev. John Polkinghorne, James “The Amazing” Randi, Alex Rosenberg, Michael Ruse, Robert John Russell, John Searle, Michael Shermer, Victor Stenger, Robert Thurman, Michael Tooley, Charles Townes, Peter van Inwagen, Keith Ward, Rabbi David Wolpe
Now available at Amazon:
Dr. Gregg D. Caruso
The Great Andromeda Galaxy, M31
The Andromeda Galaxy is a spiral galaxy and it the closest large galaxy to the milky way (this is not including dwarf galaxies). It is approximately 2.5 million light-years away in the constellation Andromeda and is listed as the 31st object in Messier’s catalog of large night-sky objects.
Andromeda is one of the easiest objects to spot in the night sky. It can be seen on a clear night with the unaided eye as a faint smudge of light about 3 times the apparent length of the moon. This makes the Galaxy a great viewing/imaging target if you have a pair of binoculars or a telescope.
Like our milky way galaxy, the Andromeda galaxy has smaller satellite galaxy, known as dwarf galaxies, that orbit it. One of these dwarf galaxies can be seen in the above images as a small smudge below Andromeda’s galactic disk.
The top image shows a wide field view of the Andromeda Galaxy. The next two images show wide field views of the galaxy in infrared and ultraviolet light and the last two are infrared and ultraviolet images taken recently by the Spitzer space telescope.
The day I stop learning is the day I stop breathing.
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Astronomical prints of the solar system, c. 1760-1825
“11 Quotes From Authors On Censorship & Banned Books" (via Buzzfeed)
What’s your opinion? Maybe these dangerous books will inspire you…
I found a cocoon from a Cecropia Silkmoth at the bog today, so I brought it home and am waiting for it to pop out… in a month or so. The pictures at the bottom show what the caterpillar looks like (they’re huge caterpillars) which turn into huge moths.