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Robert Scherrer
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73 followers
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An Astronomy Math Puzzle
It's pretty easy to measure the radial velocities of distant stars or galaxies. (The "radial" velocity is the motion of an object directly toward or directly away from us). Astronomers use the Doppler shift, the stretching or compression of light from the m...
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Time Travel Stinks
Time travel is one of the most enduring themes in science fiction, as well as one of the most implausible -- I've discussed the science of time travel  here . But there's one piece missing from almost all fictional discussions of time travel: the smell. Abo...
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Dark Energy: The Final Exam
Where do theoretical physicists get their ideas? That's a hard question to answer. But in the case of my most recent paper, which just appeared in Physical Review D (the preprint version is available  here ), I can tell you exactly where the idea came from:...
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What is the Universe Made Of?
Good question.  I gave a public lecture (more specifically, the Lois McGlothlin Donaldson Endowed Lecture in Physics) on this subject at the University of Memphis last week -- if you are interested you can watch it  here .
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How Did We Survive the 1980s?
I just finished writing a short story that had to be set, for various reasons, in the early 1980s.  And I could feel my characters' pain.  How does one character find out about another one when there's no internet??   I couldn't have anyone type into a comp...
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Stephen Hawking 1942-2018
I met Stephen Hawking a few times over the years -- the most memorable was in the early 1980s when I was a grad student at the University of Chicago. Stephen was visiting the university, but he also wanted to take a side trip out to Fermilab -- a one-hour d...
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Was the Early Universe Lumpy?
When the universe was only a few minutes old, was it smooth, like Cream of Wheat (yum!), or was it lumpy, like oatmeal? (Yuk!)  British cosmologist John Barrow and I explored this question in  this paper , posted yesterday. Most cosmologists think that the ...
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A Bayesian Coin Flip
Anyone who's spent any time at all with the scientific literature has encountered the phrase "Bayesian statistics." What's that all about?  How can there be more than one kind of statistics? Isn't statistics just a branch of mathematics, where everything is...
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Why I am not a Biologist
I diligently avoided biology throughout my high school and college years. Why? Well, for starters biology is the smelly science. Also wet, sticky, and generally disturbing. Contrast that with the clean, crystalline clarity of physics. But I've also come to ...
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Interstate Traffic Jams and Galactic Structure
Last fall I drove up to Williamsburg and Washington with a couple of my kids. It was a pleasant trip, except for the stretch of I-95 between Richmond and Washington. There, on a sunny Sunday afternoon, we encountered a series of sporadic traffic jams. Each ...
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