Posts Tagged ‘space’
Arcturus and Spica
Fire in the Sky
From a letter to a friend shortly after 9/11
Date: Sun, 11 Nov 2001 10:03:47 -0500
To: Dave
From: DeafScribe
Subject: Fire in the Sky
That was 3 hours well spent.
I just returned from the beach. Got the bike out at 3:30, mounted the night light, added a bit of air to the front tire, and set off for the shore. It’s a straightforward trip – one block over to 16th St., then follow that for about 3 miles to the ocean. There’s just one hurdle – the Indian River and the bridge that vaults over it.
As much as I love my Schwinn 10-speed, it has one glaring flaw – the gearshift is old and totally unreliable. Despite the occasional adjustment, it inevitably slips back into a state where shifting gears will lock it up, jam the chain between the chainrings, and force a miserable roadside battle with an stuck chain and grease-coated hands. To avoid this fight, I leave the bike in 10th gear, which is great for keeping my legs strong, but not so fun for honking up a big bridge.
Still, it could be worse. I’m not smoking anymore, so I was able to reach the bridge top without gasping too badly. Sixteenth Street is lined with bright lights nearly the whole way, but even peering through them, I could see the meteors streaking down from the east. Beyond the lights, the conditions could not be better. The sky was crystal clear, the stars were blazing and the night was comfortably cool.
The bridge plays out to A1A, the highway that runs alongside the Florida coast. Crossing that, it’s another 1/2 mile to South Beach park. I could have stopped there, and it would have been a fine choice since it’s very dark, but I pushed north toward Humiston Beach. This meant a winding ride through silent streets unmolested by lights.
I turned off the bike lamp and let the stars light the way. The Big Dipper hung in the northeast, pointing the way to Polaris, the north star. The belt of Orion flew nearly overhead, escorted by Betelgeuse and Rigel, and Capella was a blazing beacon. To the east, where breezes carried the scent of the sea, bright streaks of burning dust and pebbles were flying down like psychedelic raindrops.
I reached Humiston, which was nearly deserted. An elderly couple made their way toward the boardwalk, where a smoker fired up a cigarette and three young girls chattered together, swaddled in sleeping bags. I parked the bike and locked it near Crusty’s, a casual restaurant propped up on posts over the sand. Went directly down to the beach, found a dark spot, and settled back to watch the show. It was 4:30.
The Leonid meteors come from a comet, the Tempel-Tuttle comet. It’s a big dirty ball of ice, a flying mountain about 2.5 miles wide. It swings around the sun every 33 years. As it passes through our neighborhood, the sun warms it and melts some of the ice. All the gravel and dust locked into the ice is released, leaving a long trail of debris in its path, much like the contrail of a jet flying through the sky.
The trail gets pushed around some by solar wind and radiation, but it mostly just hangs there in space. There’s no real wind to break it up and scatter it, so the trail we’re plowing into this year has been hanging around for three centuries, since Tempel-Tuttle passed through in the 1700’s. The comet leaves a long half-donut of dust and gravel around the sun every time it passes through. Some years it dumps more than others, and some years we hit a denser part of it than others. This year the prediction is that we’d hit an especially dense part.
Not all meteors are created equal. Some just skim past the earth in the upper atmosphere, like a flat rock skipping over the surface of water. Some hit the earth at an angle, and some crash in head first. Some come from behind our motion around the sun, catching up to the earth, and almost float into our atmosphere.
The Leonids mostly come screaming in head first. This means they come in very, very fast. There’s no sound on the ground, of course, since these are pretty small meteors and all the action is going on about 60 miles overhead.
If a fireworks show is rock and roll, then a meteor shower is understated classical symphony. It’s not an in-your-face explosion of light and sound. It’s more of a subtle, unpredictable rhythm, one surprise following another on a deep velvet void inlaid with fiery diamonds.
Even when there’s no meteor shower expected, most nights you’ll see 2 or 3 if you watch the sky for a while. The trick to seeing meteors is not to look for them. Just lie back and let your eyes relax, not seeking, not focusing on anything especially. Once you have that trick down, your side vision picks up everything in view that moves, and your eyes will dart in the direction of any movement. That way you seldom miss anything, even the really short, fast meteors.
Tonight, though, it was impossible to miss anything. At 4:30, they were appearing in a steady parade, one at a time, perhaps 2 or 3 each minute. Some were tiny and dim, some were bright and sharp. They left lines of light in varied colors and shades – red, blue, white, purple, even green. Nearly all were wicked fast, ripping by in an eyeblink. Sometimes they burned with the intensity of a welder’s torch, so bright they cast shadows.
In 20 minutes’ time, the parade began to moving faster. They flew down in quick bursts of 4 and 5, appearing within seconds of each other. Mixed in with Leonids were slower meteors coming from other directions. A steady stream of larger green trails were left by slow earth grazers coming from the north. Quick white wands of neon winked on and off past Orion’s belt.
It’s easy to imagine ancient people being awed by nights like this. They must have wondered if the very stars were falling to the earth.
By 5 a.m, the single notes of individual meteors were being replaced by whole chords appearing together. 4-5 would spray down at once, usually entering from different directions, sometimes flying in formation. Seeing 10 to 15 meteors a minute was not unusual. Anywhere you looked, a gentle celestial rain was falling. It would not have been surprising if a rock thudded into the beach and sat there, steaming, a relic possibly older than the Earth itself. Above us, fragments just as old spent their final moments of existence tortured by a sudden impact with an ocean of air, turbocharged fireflies smashing into our atmospheric windshield.
It was hypnotic, relaxing, transcendent, beautiful. Sounds like hype for a trip through a cloud of dust and gravel, but it was all that and a side of fries, too.
At 5:30, meteors were still coming fast and furious while dawn was making itself felt in a ghostly gray light over the waters. It was time to start back for home. I stood and brushed off the beach sand, thinking that many of the meteors that appeared tonight were not much larger, and not so very different, than these same grains.
It’s of a piece, really, what lies out there and what we work with every day. It’s all connected, a tapestry woven from elements forged in the heart of stars.
The rain of fire will return next year.
Be there.
The Inner and Outward Gaze
Ever seen those delightful Russian matryoshka dolls, the ones where each doll opens to reveal another, smaller but identical doll, which opens to reveal yet another smaller, identical doll, and down it goes to a doll the size of a peanut?
Likewise, the films Inception and the Matrix portray realities within realities within realities, scrambling our perception of reality.
There’s an everyday analogue to this – a simple mirror. You gaze at the mirror through your eyes, which are reflected in the mirror, so your view includes the thing you are viewing through.
Both are real, the view and the reflection, and neither can exist without the other.
This image is another example, taken from the International Space Station.
What you see is an orbital sunset, looking out the back view as the ISS circles the globe. Two Russian ships can be seen docked with the sun’s glare between them, a Soyuz crew capsule in the foreground and Progress cargo capsule in the background, with the earth’s horizon outlined by a thin layer of atmosphere.
You can also see the dim outline of a camera lens. This can only be seen when the angle of the sun’s light is such that the transparent cover over the camera acts like a mirror and reflects an image of the camera.
And so it is that the instrument we use to see the earth is mirrored back to us. Our own eyes gaze back at the manufactured eye we ordinarily look out from.
This demonstrates in a concrete way something that a wise man once noted:
Three Bright Lights
Last night the sky over Washington, DC was unusually clear, so we had a spectacular view of three planets low in the pre-dawn east. Venus, Jupiter and Mars were all pointed toward the coming sunrise. It reminded me of one of the early geometry puzzles I sorted through while learning astronomy.
Venus orbits closer to the sun than we do. When we’re on the earth’s night side, it’s orbit is “behind” us. When we look up and out, we’re looking toward the orbits of the outer planets – Mars, Jupiter, Saturn, etc.
So it makes sense that we see the outer planets at night, when we face away from the sun; but how is it we can see them and the inner planet Venus *at the same time*?
If all the planets remained aligned and orbited in lockstep, then that would be an issue. But of course planets are at different parts of their orbits at different times, and this gives us windows when we can see them together.
My phone is most definitely not an astronomy camera. Please accept this simulated view from Stellarium, matching the exact time I saw it last night. The actual view was more impressive. Click on images to enlarge.
Celestia provides real-time simulated snapshots of our solar system. The view below is tilted sideways because you’re standing on a ball looking east. See the string of lights in the middle of the ocean? Hawaiian islands. Top center of Earth, the lights of the California coast. Look up, and what do you see? Same planets, same alignment.
Same image, with orbital paths added:
And an overhead view of the solar system at the same time:
.
..and that’s how you see three planets, one inner, two outer, together on cool fall night.
How to Pop a Parachute on Another Planet
The Martian atmosphere lies low and thin. There’s not enough of it to land softly by parachute alone. But when you come screaming in a little over 3.5 miles per second, it’s almost more like water than air.
The Mars Science Laboratory hit the atmosphere at 13,000 mph and slowed to 900 mph on atmospheric friction alone. Peak heating during this period is twice as hot as melted rock, or lava.
Then it popped a parachute. There’s enough atmosphere at the altitude of six miles – about the same height as a jet airliner over Earth – for a parachute to slow everything down a lot.
Here’s that parachute during indoor testing on Earth:
Even in a very thin atmosphere, popping a chute at 900 mph creates a lot of stress, about 9 Gs. How do you test for that? With a helicopter, a rocket sled and a lot of very strong cable. Watch to 4:00 to see the big picture:
You can do more than see this parachute. You can ride it down. Twenty seconds after the parachute was deployed, the heat shield was dropped while the rover was 5 miles above the surface and falling a bit over 500 mph. That’s where the ride begins:
Images have been captured of the parachute in its final resting place.
It’s still blowing in the Martian winds.
Martian Geology
This image from India’s MOM mission highlights a region with stress fractures – cracks – in Mars’ crust that can run as much as 3 miles deep. They’re called fossa, sometimes grabens, and they exist on Earth too. Yes, you are riding on a cracked surface. Have a good day.
Elsewhere on Mars, there’s a volcano notable for being about the same height as Mount Everest. (It’s tiny compared to other Martian volcanoes). The linked image shows a forked valley sloping down from the volcano.
https://en.wikipedia.org/wiki/Ceraunius_Tholus
Studies of the valleys suggest they were originally formed by lava flows and later altered by water flow. Think about that. It would require an atmosphere that was warm, wet and large enough to rain down into the caldera at the altitude of Everest’s peak.
Obviously the water cycle and atmospheric dynamics are different on a young planet with about 1/3 of earth’s gravity.
The best estimate of when the volcano’s caldera and channels began filling with water date back to the Late Heavy Bombardment, right about the same time bacterial colonies begin to appear in Earth’s fossil record.
http://onlinelibrary.wiley.com/doi/10.1029/JB095iB09p14325/abstract
Influential Prose 