How will we finally image the event horizon of a black hole?

By Ethan Siegel, NASA  JPLSpacePlace_1in.en

One hundred years ago, Albert Einstein first put forth his theory of General Relativity, which laid out the relationship between spacetime and the matter and energy present within it. While it successfully recovered Newtonian gravity and predicted the additional precession of Mercury’s orbit, the only exact solution that Einstein himself discovered was the trivial one: that for completely empty space. Less than two months after releasing his theory, however, the German scientist Karl Schwarzschild provided a true exact solution, that of a massive, infinitely dense object, a black hole.

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How we know Mars has liquid water on its surface

by Ethan SiegelSpacePlace_1in.en
NASA JPL

Of all the planets in the solar system other than our own, Mars is the one place with the most Earth-like past. Geological features on the surface such as dried up riverbeds, sedimentary patterns, mineral spherules nicknamed “blueberries,” and evidence of liquid-based erosion all tell the same story: that of a wet, watery past. But although we’ve found plenty of evidence for molecular water on Mars in the solid (ice) and gaseous (vapor) states, including in icecaps, clouds and subsurface ices exposed (and sublimated) by digging, that in no way meant there’d be water in its liquid phase today.

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Measure the Moon’s Size and Distance During the Next Lunar Eclipse

By Ethan Siegel  SpacePlace_1in.en
NASA JPL

The moon represents perhaps the first great paradox of the night sky in all of human history. While its angular size is easy to measure with the unaided eye from any location on Earth, ranging from 29.38 arc-minutes (0.4897°) to 33.53 arc-minutes (0.5588°) as it orbits our world in an ellipse, that doesn’t tell us its physical size. From its angular size alone, the moon could just as easily be close and small as it could be distant and enormous.

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Solar Wind Creates—and Whips—a Magnetic Tail Around Earth

By Ethan SiegelSpacePlace_1in.en
NASA JPL

As Earth spins on its axis, our planet’s interior spins as well. Deep inside our world, Earth’s metal-rich core produces a magnetic field that spans the entire globe, with the magnetic poles offset only slightly from our rotational axis. If you fly up to great distances, well above Earth’s surface, you’ll find that this magnetic web, called the magnetosphere, is no longer spherical. It not only bends away from the direction of the sun at high altitudes, but it exhibits some very strange features, all thanks to the effects of our parent star.

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On The Brightness Of Venus

By Ethan SiegelSpacePlace_1in.en
NASA JPL

Throughout the past few months, Venus and Jupiter have been consistently the brightest two objects visible in the night sky (besides the moon) appearing in the west shortly after sunset. Jupiter is the largest and most massive planet in the solar system, yet Venus is the planet that comes closest to our world. On June 30th, Venus and Jupiter made their closest approach to one another as seen from Earth—a conjunction—coming within just 0.4° of one another, making this the closest conjunction of these two worlds in over 2,000 years.

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No Surprise! Earth’s Strongest Gravity Lies Atop The Highest Mountains

By Ethan SiegelSpacePlace_1in.en
NASA JPL

Put more mass beneath your feet and feel the downward acceleration due to gravity increase. Newton’s law of universal gravitation may have been superseded by Einstein’s, but it still describes the gravitational force and acceleration here on Earth to remarkable precision. The acceleration you experience is directly proportional to the amount of mass you “see,” but inversely proportional to the distance from you to that mass squared.

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The “G” in GOES Is What Makes It Go

By Ethan Siegel SpacePlace_1in.en
NASA JPL

Going up into space is the best way to view the universe, eliminating all the distortionary effects of weather, clouds, temperature variations and the atmosphere’s airflow all in one swoop. It’s also the best way, so long as you’re up at high enough altitudes, to view an entire 50 percent of Earth all at once. And if you place your observatory at just the right location, you can observe the same hemisphere of Earth continuously, tracking the changes and behavior of our atmosphere for many years.

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Building the Maxx Rack Rocket

William Orvis, LUNAR#309

After building the MicroMaxx Rack rocket couple of years ago, I decided to go in the other direction. C engine rack rockets are pretty standard and D engine racks have also been done, so, it seems like it is time for an E-engine rack rocket. E12-0 engines had just come available and are just the just the ticket for a rack.

fleet

Figure 1. The Rack Rocket Fleet: MicroMaxx, 18mm (C-motor), and Maxx (E-motor).

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Ooops, I Broke a Fin!

Ooops wasn’t the first word that I actually used.

The story of how I got to this point is long and boring. But at the end of that story, I had a nice, all carbon fiber 54mm minimum diameter screamer I was affectionately calling Doppler Shift. I launched it on a J415W at December’s Snow Ranch launch and promptly lost it, despite having a Walston RF tracker onboard.

I was hacked to say the least, but I managed to recruit our club president to go back to Snow Ranch with me on Sunday and hike the acres with the receiver looking for it. As luck would have it he found it, but it managed to find the one rock on that hill and broke a fin.

This is a minimum diameter rocket. The fins are surface mounted, and since it was originally designed to fly on an EX “L” motor, they had to be strongly attached. The original work was done by James Marino, and he used both fiberglass and carbon fiber to attach the fins. Only one fin was damaged, and it was not actually broken, but the fin to airframe attachment was broken. The layups where still intact, and were still holding. So I wondered “What should I do?” This article is about what I did, and how it worked out.

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