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Voyager 2 Set to Reach Termination Shock
Invisible Pink Unicorn writes "A computer model simulation developed at UC Riverside has predicted that in late 2007 to early 2008, the interplanetary spacecraft Voyager 2 will cross the termination shock, the spherical shell around the solar system that marks where the solar wind slows down to subsonic speed. At the termination shock, located at 7-8.5 billion miles from the sun, the solar wind is decelerated to less than the speed of sound. The boundary of the termination shock is not fixed, however, but wobbly, fluctuating in both time and distance from the sun, depending on solar activity. Because of this fluctuation, the spacecraft is also predicted to cross the boundary again in middle 2008. The article abstract is available from The Astrophysical Journal."
speed of sound... wait a minute? In which medium? I don't think there is much atmosphere up there...
but can someone describe in layman's term what will that mean for the probe (if anything), will it change course/direction? can this negatively affect the mission/spacecraft itself?
Interesting that the sun can have variation 8 billion miles away, with its power "fluctuating in both time and distance" but Global Warming Alarmists will deny that it has any varying influence a mere 93 million miles away on the Earth. Never mind, buy some carbon credits, and we'll all be safe until the next crisis!
Now that the tailwind has slowed down.
Anyone else notice the related stories on the news site?
Nov. 6, 2003: Voyager Spacecraft Approaches Solar System's Final Frontier
Dec. 19, 2000: Most Distant Spacecraft May Reach Shock Zone Soon
May 25, 2005: Voyager Spacecraft Enters Solar System's Final Frontier
Besides the speculation, will we even know when the boundary is crossed? Do they expect data to indicate a transition, or do we even know if the instruments can detect such a thing?
Dan East
Better known as 318230.
Want to see the actual orbital trajectories of the Voyager probes for yourself in 3d type of thing? Because you can, if you use my nBody modeling software.
If you go here:
http://code.google.com/p/nmod/downloads/list
and get the windows installer or linux source for my nbody modeling kit, and then download this:
http://www.politespider.com/nbo/time_series.zip
And unzip it to save you the bother of having to actually generate your own time series (3d time series model of the solar system), which can take a while. You can then watch both Voyager probes follow their orbits (with 24th august 2006 as their starting date), for 20,000 days of travel time.
This isn't a program with a scrummy easy interface I'm afraid, the viewer is console opengl. But there are instructions here:
http://code.google.com/p/nmod/wiki/nbview
And it's not too hard once you get the hang of it.
The orbits do not take termination shock into account, this is pure Newtonian motion. The dataset for the solar system has taken months to put together. It's incomplete, It only has our moon (zoom in for ages with Earth centred and you'll see it), the others have been tricky to get right.
It's not garbage. The density of matter in space is important, and speed of sound is applicable.
Think of it this way, if your sitting in the next cubicle over and I whisper something and you are unable to hear it, does that mean that the speed of sound doesn't exist, or simply that the amplitude of the signal was too small? Similarly, in order to transmit sound in space I'd need some serious lungs. More to the point the speed of sound is a critical parameter when examining how two flows (such as the solar wind and the interstellar medium) interact. Simply put if the speed of sound in the interstellar medium were undefined it would not interact with the solar wind, and there wouldn't be a termination shock at all. Every particle of the solar wind would not interact with any particles of the interstellar medium.
It's been a while since I've done any fluid dynamics, so some of the details may not be precisely right, and I am not knowledgeable enough on rarefied systems to comment on why the speed of sound is so high in the interstellar medium, but suffice to say that many things behave in counter-intuitive ways for rarefied systems.
A termination shock/shockwave/bore/hydraulic jump occurs when the bulk speed of a fluid drops below the wave propagation speed.
Run a tap in to a flat sink (like a kitchen sink) and you see a circular pattern (if the sink is flat) some distance from around where the water hits the sink. The pattern should have shallow fast moving awater close to where the jst hist the sink, and deeper slower water on the other side of the circle.
The "jump" where the water goes from fast to slow is the same kind of object as a termination shock. For extra fun, stick an object in the slow water, and see how waves propagate ahead of it (against the flow). Then see how it doesn't happen in the fast water.
SJW n. One who posts facts.
Actually no. The spacecraft would have crossed the boundary twice and the boundary would have overtaken the spacecraft once.
You can say you crossed the threshold of a door by walking through it. But if you stand still and the door suddenly flies past you, I don't think you can claim that you crossed the threshold.
Tesla was a genius. Edison however was a overrated hack who liked to torture puppies.
Europeans in general don't understand this, and it's probably true for most of the rest of the world. From where I live I can make it to Mexico in about 12 hours of solid driving, or to Canada in about 20 hours, but in most places in the US it's a day or more of travel time to either country. In most of Europe you can be to another country in an hour or two. Now, I've lived in both Italy and Germany (for about a total of 5 years of my life), and when I'd be talking to people, they'd talk about wanting to travel to the US and all the places they'd like to see. Want to see LA, San Francisco, New York, New Orleans, Grand Canyon, Yosemite Valley, Yellowstone, etc., and expect they could manage this in about two weeks, which, by comparison, is like wanting to travel from Moscow to London and hit all the major points in between in that kind of time frame.
The reason why many Americans speak only one language or don't spend a lot of time in other countries is based in this. For a majority of Americans there is only one language besides English that is of any utility, and that is Spanish. I was once fluent in both German and Italian, but since I've been back in the US I have yet to run into a situation where I needed to speak either language. It's not like we can day trip to France or that most businesses can deliver finished products to a foreign country with a simple truck ride of 3 or 4 hours.
The termination shock fluctuates in distance because it's an interaction between the heliosphere of the sun and the interstellar medium. Parts will experience more drag due to magnetic fields, and thus be closer to the sun than other parts of the shock. It fluctuates in time because the sun's output fluctuates in time -- when the solar winds are stronger, the corresponding parts of the termination shock will be further away. So it fluctuates in both time and distance, and depends upon solar activity. Just as the writeup said.
Fluctuate, by definition involves time. Saying "The price of oil fluctuates wildly" is ok, because obviously you mean it fluctuates over time. Saying "The time and price of oil fluctuates wildly" does not make sense. That's what the summary basically said - I personally thought there were weird time effects being implied about the termination shock. It's just a crap use of a word in TFS that doesn't make sense.
If your talking high culture then yes Manhattan is pretty much our epicenter. I have only been to DC on guided tours, so the only culture I experienced there was tours of the Smithsonian, government building and monuments.
Now in terms of folk culture, you are wrong. First of all the world epicenter of low culture is Queens NYC, possibly the most ethnically diverse area of its size on the planet. Secondly, if you can't tell the difference between different parts of the country then you need to open your eyes. Compare New York and California for example. Even though a small but sizable portion of the population regularly travels between the LA and NY metro areas, the cities have completely different feels. Try finding good grits in the North East, or decent Italian food in the South, minus a few places with significant migration from New York.
I just love when Americans (who know I am foreigner from the other side of the ocean) ask me whether I went back home for Thanksgiving, and I study in one of the top 25 universities in the USA. I can never understand how people can ace Calc IV without studying and yet they are too ignorant to know that Georgia isn't simply a state. It's nation with a 3000 year old history, no less.I have two counter points to that.
First of all good at math does not mean good at history. If they are that good at math, and don't care for geography, they can survive just fine in college. I know a brilliant Mathematicians and programmer that probably didn't know where Prague was until he had to fly there to enter his physics engine into a competition. I would think that brilliant mathematicians in Georgia that do not study overseas have a narrower world view than you do. Also, I'm also sure Americans that study overseas have a firmer understanding of the world then their classmates.
As far as people asking you how your thanksgiving was, we Americans are known for engaging in mindless smalltalk. Most people probably didn't think out their statement. They also probably didn't care about your holiday. Finally how many of these people know you are in this country alone and not with your family.
--- Justin Dearing http://www.justaprogrammer.net/ We're just programmers.
Obviously, you've visited a few cities as a tourist. You've fallen for tourist view of any city, visited landmarks, etc. If you've lived all over the US, you would have realized that large cities have ethnic neighborhoods where English is not always the first language. Polish, Spanish, Italian, Hmong, Irish, etc. Hell, English isn't always understandable from various parts of the country.
I asked my co-worker what she was doing for Thanksgiving. She was going back home... to India. I may even ask her what's she's doing for Christmas even though she's not Christian.
While there are dumb, socially-inept, or culturally unaware Americans, are you sure they know you're from the other side of the ocean? A Georgian (country) accent isn't enough to say you're from another country.