Get Bent

2003 Cassini Radio Experiment

On the way to Saturn, NASA ran an experiment to further verify Einstein's theory that gravity bends space. The experiment was a success. I think this image gives very good view of what they were doing.

Via Starts With A Bang!

Killing Titan - Greg Bear

Sunlight glints off of Titan's northern seas this near-infrared, color mosaic from NASA's Cassini spacecraft. Credits: NASA/JPL/Univ. Arizona/Univ. Idaho

Killing Titan is book 2 of a Science Fiction adventure trilogy by Greg Bear, but I didn't figure that out until I got to the end and they start telling me about book 3. There oughta be a law that requires bookstores to keep all volumes of a series on the shelf so you can see what you are getting into, or more importantly, so you can start at the beginning. Whatever.
    There were some very good pieces in this book, but the overall tone of gloom, despair and willful ignorance was a bit much. Our 'hero' has some issues and he spends an inordinate amount of time obsessing about them.
    The giant machines in space and on, or in, Titan are good, as is the mysterious quantum-something space drive that takes them from Mars to Titan in a matter of days. (Cassini took years). We also have machines that grow from 'seeds' and/or finish constructing themselves out of whatever material is at hand. There are some mental shenanigans that seem to be an essential part of space adventures these days. I'm pretty sure that's never gonna happen, but then man was never going to fly either, so what do I know?
    The best part is diving into the liquid methane oceans on Titan. That was pretty cool. NASA is thinking about it.


Titan Submarine: Exploring the Depths of Kraken Mare
You can buy a copy from Amazon for $12. I paid $15 for the one I purchased at Branes & Noble  in Twin Falls, Idaho. You can also buy a copy from Amazon for $80. What's up with that? Who would pay $80 for a $12 book? I've run into out-of-line prices before on Amazon and I still don't have any idea what's going on.

Speed of Gravity

Aug 20, 2015:Dione with Rings and Shadows - Dione hangs in front of Saturn and its rings, captured during Cassini's close flyby of the moon. Saturn is only about a hundred times bigger than this tiny moon.
Nobody understands how gravity works, or if they do, they haven't convinced anyone else that they do. Some people think there are particles involved, kind of like magnetism and neutrinos, but no one has ever figured out what they were.
    I read a science fiction story once about a guy who had invented a graviton conductor. It conducted gravitons much the way a wire conducts electricity. You could clip it onto something and let it hang down to the floor and all the gravitons would drain out of the object. The more gravitons you drained out, the lighter it became. Eventually it would become so light it would just float away. The guy who invented it didn't have much imagination because he used it to give his trucking company a boost. He installed a paddle wheel on the driveshaft of his truck. Once his truck was loaded, he would connect his graviton cable to the load and dangle it above the paddle wheel. Gravitons draining out of the load would strike the paddlewheel and give his truck a boost. It also made his load lighter.
    He couldn't deliver ten tons of corn if it only weighed ten pounds, so just before he got to his destination, he would stop by the base of a cliff and drain some gravitons from the cliff back into the load. It wasn't long before it got out of hand. You'd go to the store to pick up a ten pound bag of potatoes and it would weigh a hundred pounds. That cliff he was draining gravitons out of to reweight his truck loads? It eventually fell into the sky. It was a great story.
    Back to the real world. There is one aspect of gravity that is a little curious. Does gravity have a velocity? The example that is usually used is how soon would the Earth notice if the Sun suddenly vanished? Would it immediately leave orbit, eight minutes before the sunlight disappeared, or would would it wait until there was no more light? The idea is that nothing can travel faster than light, so gravity, if it has any physical substance at all, couldn't travel faster than light, so as long as there is sunlight, the Earth would stay in orbit.
     I always thought that this was a particularly useless example. Matter doesn't just vanish and even when it does (like in an atomic reaction) so much energy is released that any kind of observation you hoped to make is going to be obliterated.
     But then I got to thinking. We are getting pretty accurate with our observations of objects in orbit in our solar system. Maybe we could measure and calculate our way to a conclusion.
    All the objects in our solar system are all pulling on each other all the time. They are also in motion all the time. So when the moon pulls on the Earth, is the pull coming from where it was a second and a half ago, or is it coming from where it is now? The moon is moving pretty quick, but in a second and half it's only going to a go about a mile. We can we tell the difference in the direction of the moon's pull, but can we determine it that accurately? I don't think so.
    On the other hand we have supercomputers and precision instruments and measuring techniques, so maybe running a simulation of the solar system could tell us whether gravity has a velocity or whether it is instantaneous.
    I tend to think gravity is simply a distortion of space. It's kind of like the landscape. It doesn't move, it's just there. But running the simulation might provide some interesting results.

Update January 2017 removed reference to trans.gif, a picture that does not appear.

Uranus - The Other Blue Planet

You can barely see it here. Uranus is the blue dot about one inch from the top left corner of the image. From Cassini, via CICLOPS. Saturn is roughly ten times as far from the sun as the Earth, and Uranus is about twice as far as Saturn. The fact that we even know that it is there should tell you something about how big it is. Cassini took seven years to get to Saturn.

Cosmic

Comrade Misfit posted this picture yesterday, but it took a day for it to sink in. This picture was taken by the Cassini probe that is out orbiting Saturn (see the portion of the rings at the top of the picture). The arrow is pointing to the Earth.
    What do you see when you look at the night sky? Stars, that's what. Occasionally you will see a planet, but you only know it's a planet because it's extra bright. The interesting thing about this picture is that, one, the Earth is visible, and, two, there are hardly any stars visible. Of course, Earth and Saturn cannot be anywhere near in line with the Sun or you wouldn't see anything besides the Sun, which probably means six months of the year (3 months when the Earth is on the far side of Sun, and 3 months when it is on the near side).
    This means that if we ever manage to make a trip to another star system, we should be able to pick out any planets with our naked eyes. Okay, not naked to the pain of space, but you wouldn't need any telescopic assistance.

Cassini

Monster Saturn Storm Created Atmospheric Hotspots | NASA JPL ESA Cassini Infrared HD Video
The LA Times had a story about a storm on Saturn that was discovered by the Cassini probe.

It was an alien storm to dim memories of all others, wrapping all the way around a vast northern portion of Saturn, a planet that could hold about 750 Earths. And it brought with it a spike in temperature never observed before anywhere in the solar system. Think of a violent storm, NASA said, that covers all of North America and continues on around the planet -- a storm from which you could not escape for nine months. - Amy Hubbard

    The video uses false colors to show what was only visible in the infrared. That's understandable, watching a gray storm on a gray planet would be pretty boring. What I found interesting was the time stamp. It is on the left center of the image and a it's a little fuzzy. It's also in a strange format. Oh, that's not a time stamp, that's a calendar stamp. This video compresses a year of watching Saturn into 15 seconds. Geez. Talk about time lapse photography.

Cassini Today

    I got to looking for more info on the probe and I found it got there in 2004 so it's been going around and around Saturn for eight years. Moreover, it took seven years to get there. That took a little planning. One of the reasons it took so long, other than Saturn is a long stinking way from us, is that it had to swing by some planets to pick up enough velocity to make it all the way out there. This voyage is, to me, the most impressive part of this project. I am sure they are doing all kinds of fascinating science there, and the orbital mechanics involved in orbiting Saturn (see picture above) are pretty impressive, but it's the getting there that impresses me.

Rough graph of Cassini's speed (red) versus time. The vertical scale is miles per second. 

The jumps are where it swings by a planet. The vertices on the blue line are the planet's velocities.
The blue line itself is there because my Graphing Fu is weak.

    We start with the launch from Earth back in 1997. As it falls toward the Sun on its way to Venus it picks up a little speed, and then when it gets there it gets a boost of a couple miles per second. Then it goes into orbit for a year, swings by Venus again (1999), gets another boost and then heads out to Earth. The difference in transit times between Earth and Venus must be due to the difference in their relative positions. The velocity difference isn't that great.
    Now we are leaving Earth for the second time, but with about five miles per second more velocity. We coast for a year and a half until we get to Jupiter where we get another little boost, and then it's a long slow slide out to Saturn, three and a half years worth.
    This whole boost thing works because

1. Planets are really big and massive and have strong gravitational fields.
2. Planets have very high velocities. They range from 3 miles per second for outliers like Neptune and Pluto to 30 miles per second for Mercury.
3. Your spacecraft is slower than the planet it is trying to get a boost from. You wouldn't do this if you were going faster, unless you wanted to slow down.
4. Your path must take you very close to the planet as it comes barreling along, kind of like a bicyclist grabbing onto the back of a truck, except it's just the gravitational pull of the planet that is acting on you.

I don't know who was driving, but they were cutting it damn close. Cassini came to 210 miles from Venus and 375 from Earth. If you knew where to look, you probably could have seen it with binoculars. It gave  Jupiter a wide berth: six million miles.

Update November 2016 replaced missing picture, replaced video with similar one from YouTube.