Assessment of astronomical numbers like those of Proxima Centauri

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Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).


Is the image accurate?
 

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  • #2
phinds
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Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).
OK. What's your point?
 
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Orodruin
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OK. What's your point?
Apart from that, OP is using way too many significant digits. You cannot say that 4.2 lightyears is 24,673,274,438,400 miles. There just isn’t sufficient precision for 12 significant digits (which would be essentially knowing your length at the precision of an atom...
 
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PeroK
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Is the image accurate?
Aren't Jupiter and Saturn slightly further apart than that?
 
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OK. What's your point?
My point is wanting to know the accuracy of the numbers in the op.
 
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Aren't Jupiter and Saturn slightly further apart than that?
Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
 
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Ibix
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Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
Well - what are the radii of the planets and the Sun? Wikipedia is a good enough source for straightforward stuff like this, and they usually cite nasa.gov links if you want to check. And how big is each of the planets and the Sun in the image? Do you know how to work out the scale factor?
 
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PeroK
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Proxima Centauri is 4.2 light years away. That is 24,673,274,438,400 miles. Going at the speed of the Sun through the Milky Way, 492,150 miles per hour, it would take 5,723 years to get there. In 100 years the Sun has only gone 431,123,400,000 miles, or 7 percent of 1 light year (5,874,589,152,000 miles).
I'm not sure I see the purpose of this calculation. The Sun and Proxima Centauri are moving relative to each other, but not at the speed you quote. The closest approach is calculated to be 3.1 light years about 27,000 years from now. You can read about here:

https://en.wikipedia.org/wiki/Proxima_Centauri

You could also calculate how long the Voyager spacecraft would take to reach Proxima Centauri and ponder the immense difficulty of interstellar space travel.
 
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phyzguy
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Yes. But I want to know if the sizes are to scale and if those planets could fit between Earth and Moon.
What do you get when you add up the diameters of those 4 planets and compare the result to the radius of the moon's orbit?
 
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They can't be to scale.

The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
 
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phinds
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They can't be to scale.

The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
That's not what "to scale" means here. The fact that all the planets are lined up like that is understood to be bogus. It's the relative sizes that are the point in question.
 
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  • #13
Drakkith
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Is the image accurate?
Yes, it accurately depicts the relative sizes of the planets and the Sun compared to one another. All of the other planets could fit between the Earth and the Moon, with a bit of room to spare.
 
  • #14
Bandersnatch
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The orbits of Jupiter and Saturn are approx. 400 million miles apart. So there is no vantage point from which both would sho a visible disk at the same time.
There certainly is such vantage point, and we're living on it. One simply has to wait until the planets line up in their orbits so that they both are opposite of the Sun on the sky.
And since they're both in opposition as of this month, one can see both showing their full discs if one goes out and looks at the sky tonight.
And if one waits until December of this year, the two planets will even be so close together to fit inside the picture in the opening post - they'll pass each other at approx. 6' of angular separation, which is approx. 1/5th of the width of the disc of the Sun.

What they can't ever be is in front of the Sun as seen from Earth, but as was already explained the picture is just to illustrate the relative (physical, not angular) sizes.
 
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That's not what "to scale" means here. The fact that all the planets are lined up like that is understood to be bogus. It's the relative sizes that are the point in question.

Sorry. In that case I'd say (I haven't tried to actually measure) that they *are* pretty much to scale.
 

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