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Old 03-15-2017, 12:00 PM
 
2,713 posts, read 3,002,511 times
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I am trying to come up with a very, very over-simplified equation to answer a question that pops up whenever I read how far away a star is. I think I finally got it but need a confirmation. If I'm wrong, maybe someone can help.

First, what I know because NASA and other experts say:

Proximasad Centauri is 4.3 +/- light yeats away. Voyager 1 travels at an average speed 1/18,000 the speed of light. I have other numbers but I don't think I need them. I think I've been over-complicating things in my effort to prove that it would take Voyager 1 ca 80,000 years to reach proximasad centauri, 80,000 being the number the experts give.

Question: Can I say it's proven if I simply multiply 18,000 by 4.3? That doesn't quite make 80,000 but I am not trying to be exact. I want a very simple equation.

Question: If the answer to the first question is "yes" and if I want to use Voyager's average speed as an estimate of travel anywhere into space, can I say 18,000 times whatever distance in light years the destination is? Ex: If I read that a star is 12 light years away, will multiplying 12 by 18,000 (or close to that) tell me about (stress about - a wild estimation) how long it would take to get there using Voyager's speed?

If the answer is no, can anyone create such an equation for fast estimates to be used when I'm reading?

Thank you.
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Old 03-15-2017, 03:33 PM
 
Location: Somewhere in northern Alabama
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Your idea works.

Vger is going about 11 miles per second. A true interstellar craft would need to go much faster.
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Old 03-15-2017, 03:57 PM
 
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Quote:
Originally Posted by harry chickpea View Post
Your idea works.

Vger is going about 11 miles per second. A true interstellar craft would need to go much faster.
Oh, good. That is going to help much when I'm reading and thinking. Thank you.
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Old 05-24-2017, 04:38 AM
 
Location: PRC
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I remember reading there is a 'problem' with distances due to assumptions made in some calculations. I seem to remember that one distance is somehow related in equations to other 'known' distances to specific points (stars/galaxies/etc) in space.

The 'problem' is, if the 'known' distances are wrong, then others based on that are terribly wrong too.

Maybe I remeber this incorrectly, do I?
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Old 05-24-2017, 06:37 AM
 
2,713 posts, read 3,002,511 times
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Quote:
Originally Posted by ocpaul20 View Post
I remember reading there is a 'problem' with distances due to assumptions made in some calculations. I seem to remember that one distance is somehow related in equations to other 'known' distances to specific points (stars/galaxies/etc) in space.

The 'problem' is, if the 'known' distances are wrong, then others based on that are terribly wrong too.

Maybe I remeber this incorrectly, do I?
I think you are remembering rightly. That is a section of science that is far over my head. Some science writers remind us that nothing is written in stone. These theories are being constantly tested and retested and sometimes tossed out. I am reading a most interesting New Scientist Collections bookazine (media slang for what looks like a magazine and is priced like a book). It is a collection of articles that discuss the pluses and minuses of Einstein's theory as of 100 years later. I don't know if you can get it - or want it. I'm not even sure it is related but: "Relativity: Mind-Bending Universe" (New Scientist: The Collection)

Must hurry off. Hazel
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Old 05-24-2017, 09:07 PM
 
Location: Sol System
1,494 posts, read 2,911,014 times
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Quote:
Originally Posted by ocpaul20 View Post
I remember reading there is a 'problem' with distances due to assumptions made in some calculations. I seem to remember that one distance is somehow related in equations to other 'known' distances to specific points (stars/galaxies/etc) in space.

The 'problem' is, if the 'known' distances are wrong, then others based on that are terribly wrong too.

Maybe I remeber this incorrectly, do I?


I believe you are referring to 'standard candles' , i.e. Cepheid variables , Wolf Rayet stars , pulsars , and other objects along those lines. These are used as celestial 'yardsticks' when measuring distances , usually to distant destinations(relatively speaking). Regarding P. Centauri , if it takes Voyager 80,000 years at current velocity to reach it(provided it was on a course to that system) , and you wish to calculate travel time to a system 12LY away , then you should first divide 12/4.3 , take the answer you come up with , then multiply 80,000 by the aforementioned answer. I could however , be mistaken.
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Old 05-28-2017, 12:40 PM
 
Location: Type 0.7 Kardashev
10,576 posts, read 7,457,429 times
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Quote:
Originally Posted by harry chickpea View Post
Your idea works.

Vger is going about 11 miles per second. A true interstellar craft would need to go much faster.
It would also need to be capable of significant mid-course corrections in interstellar space. The Voyagers, of course, are simple interplanetary devices that keep going because nothing is stopping them - accidental interstellar tourists, so to speak.

Quote:
Originally Posted by ocpaul20 View Post
I remember reading there is a 'problem' with distances due to assumptions made in some calculations. I seem to remember that one distance is somehow related in equations to other 'known' distances to specific points (stars/galaxies/etc) in space.

The 'problem' is, if the 'known' distances are wrong, then others based on that are terribly wrong too.

Maybe I remeber this incorrectly, do I?
You do remember incorrectly.

The distance to Proxima Centauri is easily measured by simple triangulation from stellar parallax. One measures the shift of the apparent position against distant background objects such as galaxies of Proxima Centauri (or other stars) between six-month intervals, during which the Earth is 2 AUs apart - ie, on opposite points in its solar orbit. That roughly 186 million mile difference serves as the baseline. Then with two angles, it's high school trigonometry. In 1838, Friedrich Bessel used the relatively crude instruments of the day to peg the distance to Cygni 61 within 10% of the currently measured value. Hubble's instruments are accurate enough to measure distances to stars out to 10,000 light-years. This, in turn, can be used to calibrate other distance-measuring techniques that are part of the cosmic distance ladder, in the same way for example that carbon-dating accuracy has been calibrated by dendrochronology.
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