top Massive Volcanic Eruptions Accompanied Dinosaur Extinction
I've never found the antipodal argument convincing. Seismic waves converge at the antipode of an impact only if the target is spherically symmetric and isotropic. In the actual Earth, you have reflections off all kinds of laterally varying boundaries. Also, the sound speed differs substantially between continental and oceanic crust, so the path matters quite a bit.
The Chixulub impact is also not that big (as planetary-scale impacts go). The projectile was what, 10 km? Shock heating is only significant within a few times the projectile diameter.
top Scientists Have Finally Sampled the Most Abundant Material On Earth
It's not liquid, it's not hot, and it's not magma.
top President Obama Backs Regulation of Broadband As a Utility
To be fair, this is basically what's happening.
about a month and a half ago
top Underground Experiment Confirms Fusion Powers the Sun
It goes down every day on its own. They just went way out west and built the lab in the spot where the Sun sets.
top Teaching College Is No Longer a Middle Class Job
What's in your wallet?
top Draper Labs Develops Low Cost Probe To Orbit, Land On Europa For NASA
It's not clear from the summary (or the linked article), but this isn't a mission at this point. This is a
concept selected for Phase I study.
From the NASA Innovative Advanced Concepts (NIAC)
news release: "NIAC Phase I awards are approximately $100,000, providing awardees the funding needed to conduct a nine-month initial definition and analysis study of their concepts. If the basic feasibility studies are successful, proposers can apply for Phase II awards, which provide up to $500,000 for two more years of concept development."
This effort is independent of the ongoing Europa mission studies (e.g. the
Clipper concept.) The Draper concept may end up getting a mission if the results prove promising. Personally, I have doubts that this will prove credible, but that's the whole point of the NIAC studies.
top Humans Not Solely To Blame For Passenger Pigeon Extinction
And for goodness sake, don't let them drive the bus.
top Saturn May Have Given Birth To a Baby Moon
Not the whole ring system. Only the A-D rings are within the Roche limit. But the phenomenon discussed here is happening in the A-ring, so this limitation does indeed apply. I don't understand how a moon could accrete here.
top Stephen Colbert To Be Letterman's Successor
Actually, I always had wanted Stewart cast as Denethor. Not only could he have played the character much closer to how he's portrayed in the book, he'd have been a great foil to McKellen's Gandalf.
top NASA Snaps Shot of Mars-Bound Comet
We certainly will be observing this comet with our Mars spacecraft.
In fact, there was a practice run with ISON last year. I think the goal is to point every telescope in the solar system at this thing during the pass.
top Job Automation and the Minimum Wage Debate
Well, at least the Canadian pennies should stop being such a problem. They stopped making them a couple years ago.
top Quarks Know Their Left From Their Right
A prolate spheroid doesn't taper to points on the end. You'd need an infinite series of spherical harmonics to describe an American football, not just the degree-2 term. Though it's sufficiently elongated that spherical harmonics might not be the best basis set. Bessel functions?
top Americans To FCC Chair: No Cell Calls On Planes, Please
Well, you have to admire the restraint, but I think this calls for a more forceful protest.
top Bill Nye To Debate Creationist Museum Founder Ken Ham
Like how Jor-El sent his only son to Earth to save mankind?
top US Customs Destroys Virtuoso's Flutes Because They Were "Agricultural Items"
I'd also be confused if this site were in my current directory.
top Get Ready For a Streaming Music Die-Off
It's always bothered me when a radio program is called a "show". What exactly are you showing me?
top Should companies start using drones for common tasks, like package delivery?
They should have used Planet Express!
top MAVEN Ready To Launch Today
A few points of clarification.
1. The major heat-producing elements are all lithophiles, preferentially bounding to silicates. So there's virtually no radioactive decay in the core. It's all in the crust and mantle.
2. Thorium is an important heat source now due to its long half-life (14 Gy IIRC). But back in the day, Uranium and Potassium-40 were much more abundant, and produced the majority of the radioactive heating.
3. Assuming the Earth and Mars initially had similar bulk compositions, they would have similar rates of radioactive heating. But Mars surely cooled more quickly. The heat production scales as the mass, and therefore the volume. Heat loss scales as the surface area. So smaller planets have the lower surface to mass ratio and cool more quickly.
top MAVEN Ready To Launch Today
Earth already had its iron core at the time of the Moon forming impact. Most of the impactor accreted onto the Earth and the cores of the two bodies merged (Canup and Asphaug, 2001,
Nature). A fraction of the silicate crust and mantle of the impactor and target was ejected into orbit. That debris accreted into the Moon. Since it is largely made of the silicate portion of the original bodies, it is depleted in metal, and has a relatively small core.
top Hotel Tycoon Seeks Property Rights On the Moon
That's actually not an error. It's a contraction of "Space September", the name of a time unit in the early attempts at a Space Calendar or "Spalendar" that wouldn't be tied to solar or lunar cycles as viewed on Earth. It never caught on, which is too bad, because "Spock-tober" would be awesome.
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