One point of evidence in support of dark matter is the way in which the speed of stars, gas and dust in a galaxy varies with their distance from the center of the galaxy, known as the galactic rotation curve. Most of the visible matter of a galaxy is concentrated near the center of a galaxy, so we would expect that more central stars should move much faster than stars on the outer rim. Thus the rotation curve should decrease with distance. However most galaxies have a fairly flat rotation curve, meaning outer stars move about as fast as inner stars. This and other evidence as led us to develop the theory of dark matter. But new research on galactic rotation curves has found an odd correlation, and it could mean that dark matter is wrong after all. Read More
Vaccines, Meteors, And Why Details Matter
It’s flu shot season, which means an annual popup of anti-vax memes in my social media feeds. Most of the memes this year are of the “OMG! The flu shot contains mercury!” variety. While it’s true that some versions of the flu vaccine do contain trace amounts of mercury, such a statement is largely meaningless. Read More
Dark Beginnings
Dark matter is one of the great unsolved mysteries of modern astronomy. We’ve reached the point where we know most matter in the cosmos is made of matter that interacts weakly with light if at all, but drives much of the gravitational interactions between galaxies. While it’s often portrayed as a modern idea added simply to shoehorn observations into the standard model, it actually has a history spanning more than a century, and the theory of dark matter has been refined and improved as we’ve learned more about our Universe. Read More
Ignorance Peddling In The Age Of YouTube
Devil’s tower, a laccolithic butte in Wyoming, is the stump of an ancient silicon tree. This amazing fact was sent to me by a reader complete with YouTube link for proof. If only I would watch the video with an open mind, I would learn the error of my scientific ways. Read More
Encyclopedia Galactica
A popular dream of science fiction has been the creation of a vast database containing all known information about the galaxy, an Encyclopedia Galactica. It would list the characteristics of stars in the Milky Way, their planets, and even the history of human alien civilizations. While still a dream in most ways, the foundation of such a cosmic Library of Alexandria is being laid with the first release of data from the Gaia spacecraft. Read More
Planet X-Ray
Pluto is emitting x-rays, and we don’t know why. Read More
Jupiter Rising
The Juno spacecraft has captured detailed images of Jupiter’s north pole for the first time. It’s churning, mottled patterns are quite different from the familiar Jovian clouds. Read More
The Constant Of Time
When Edwin Hubble first demonstrated the Universe was expanding in 1929, you could do a simple calculation to determine the age of the Universe. Take the rate at which galaxies expand from each other (known as the Hubble constant H) and set it equal to the inverse age of the cosmos (1/t). This simple model assumed that the Universe expands at a constant rate, thus Ht = 1. When this was first proposed within the context of the big bang model, it actually raised a few questions. Early measurements of the Hubble constant were much higher than the current accepted value, which gave a cosmic age that was actually younger than some stars. Read More
The Enemy’s Gate Is Down
I’ve been getting a flurry of emails and comments recently from folks who don’t believe the Earth is round. It’s pretty straightforward to demonstrate to yourself that the Earth is indeed round, but this time the argument is about gravity and Earth’s (supposed) rotation. Water droplets on a ball will fly off if you rotate the ball due to centrifugal force. If the Earth rotates once a day, then stuff on the equator is moving at over 1,000 mph, while stuff near the poles is barely moving. How can gravity be strong enough to keep things from flying off the equator without simultaneously crushing things at the poles? Read More