Thinking about planetary-sun distance in more every-day terms. I.E., briefly: Will our Sun bake us like a potato?

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Summary: How far is the Earth from the Sun? How far is the Earth from Venus? I try and relate the relative distance between the two by using every day measurements.

Sunday, 15 November 2009

(15:12:28 CST)

Thinking about planetary-sun distance in more every-day terms. I.E., briefly: Will our Sun bake us like a potato?

Last night, I was talking with Sarah about the chance of our solar system suffering a "red giant stage". I know that our star (i.e. the Sun) has a that midline weight (1 solar mass) that is kind of unknown variable. We see clear patterns from greater than one solar mass, and clear patterns with less than one solar mass; but one solar mass seems to be a little but unknown. Currently, it looks like the consensus is that the Sun will achieve a red giant roughly two hundred times its current radius. Its current radius is 6.955x10^8m, so 6.955x10^5km, or (695,500 km =) 433,164 miles. Here's an interesting tidbit for you, as an aside, the Earth's radius is 3963 miles (6378km). That means the Sun is "only" about 109 times the size of Earth in terms of radius (I'll leave volume calculation to your own time). However, 200 times 433,156 miles is 86.63 million miles, which is very close to the AU (astronomical unit, the distance between the Earth and the Sun, 93 million miles). In this regards, the fate of the Earth is essentially unknown. Especially once you calculate shifts in momentum, solar pressure, orbital shifts, and so forth. If the Earth stays where it is, life as we know it will be impossible. Life, itself, may just be fine. For better or worse.

Let's be honest, though, we are talking about measurements and distances so great that we are confused easily by them. Saying "1 AU" means just about nothing. The Sun, 100 Earths wide, becoming large enough that it's radius, in empty space, would take light over 7 minutes to traverse. How safe would Mars be during all of this? While talking with Sarah about this, I tried to give some estimates about it, but I figured it would best to sit down with some some actual data and Google Maps, and try and figure out distances in terms that someone can understand. For the sake of the argument, I am going to take two paths. The first is translated to "feet". Let's pretend the Sun is your kitchen table, for instance, and the Earth was a book on the floor about a foot away. How do the rest stack up? The other variation is UAH (University of Alabama in Huntsville). If my apartment (about 1.4 miles, for simplicity sake) is the measure for 1 AU, how far would the other planets fit. All given measurements (by the way) will be in gigameters and AU. For rough conversion, a km is about 0.62mi so a gigameter is 620,000 miles. Each radius is the "mean radius".

Mercury, the closest planet, is 58Gms away. This is .39AU. If the book was a foot away, Mercury would be a thimble a little less than 5 inches away from the table. In terms of distance, if my apartment is 1.4 miles from UAH, Mercury would be slightly over half a mile, which comes out to be about Quail Pointe (if you take my route home) or around John's Big Brother, if you go down Holmes.

Venus, our "twin" planet (if twins can have conditions unlivable by us) is almost exactly twice as far away from the Sun as Mercury, with 108Gm. This is .72AU. The toy that represents Venus is just a hair short of being 9 inches from the table. On my walk home, I'd be a mile into my trip, give or take, so just crossing Jordan Lane. Heading down Holmes, we are not quite up to Butler High.

Earth, as said, is 1.4 miles and one foot away. Just to keep us on track, this puts us about where Holmes intersects with Triana. A street or so back from that. As, before I move on, let's discuss the Moon. It is about 238,000 miles away from us. In terms of AU, that makes it .0026. In terms of "feet", it would be about 3 hundreths of an inch, about a quarter of an eighth of an inch, or half a sixteenth. It's a speck very close to the book that is the earth.

Mars, the planet we tend to be most obsessed with, is 228 Gms. That's 1.5AU. Assuming I continued my walk down (around) University drive, we are looking at about 2.13 miles. That's somewhere past Meadow St (where the Jet-Pep is). If I was heading down Holmes, we would be heading down under the I-565 overpass. In terms of our table, we are looking at about 18 inches from the table. Now it starts to get big.

The asteroid belt is really hard to narrow down, being, as it was, more than an AU across. We'll skip it and head the king of the Solar System: Jupiter. Jupiter is 778Gms. That's 5.2AU. That's an object over five feet from your dinner table. On my trip down University, we are talking about 7 miles, so we've turned into Pratt and headed up to Monte Sano state park (and overshot it). Holmes, via Five Points, has done rougly the same thing (we've well shot through Downtown). We'll abandon those precise routes for now and go into more general terms down 72.

Saturn, of the rings, is 1430Gms from the Sun, not all that much shy from double that of Jupiter and 9.5 times that of Earth. We are now 9.5 feet from the table, probably at the wall or in a nearby room. In terms of "road" distance, we are 13.3 miles away. That puts us about half way to Grant, maybe somewhere near the Halloween attraction, the Maize.

Uranus, number 7, is 2870Gms! Twice that of Saturn. Slight over 19AU. We are talking nearly 20 feet away from the table, over 10 feet from whatever wall represented Saturn. We are in the next room. Mile wise, we are up to nearly 27 miles away from UAH. We are as far from Saturn as Saturn is from the "Sun". As the crow flies, we are now in Grant. Following 72, we are in Woodville.

Now, Neptune and Pluto (for the sake of the argument, we'll leave Pluto's status to the side) have a complicated orbit and it is possible that Pluto is a moon of Neptune that was stripped. Pluto occasionally swings within Neptune orbit (that's to say that Pluto's perigee is within Neptune's apogee). Going by the mean radius, though, Neptune comes first. At 4500Gms. That's 30AU. As far from Uranus as Uranus is from Saturn, which is as far as Saturn is from the Sun. If you were to stack the distances of the inner planets to the Sun back to back, up through, Jupiter, you would get about 8.9AU. That means, if you had five travellers from the Sun travel to each of the 5 closest planets, their sum travel would be less than the distance from Uranus to Neptune (and, also, less than from Saturn to Uranus). 30AU gives us 30 feet. Depedening on the layout of your house, we are now likely somewhere outside in most directions. Let's say you have a small shed in your backyard, not far from your kitchen. Along the road, we are 42 miles down. We are past Scottsboro and heading North-East, by a few miles.

Pluto's mean is 5900Gms, or an astronomical hair sort of 40AU. 40 feet away from the table, now (the junk behind the shed, maybe). About 56 miles. We are now somewhere around Stevenson, AL, and nearing the stateline. If, instead, we use Pluto's max radius, we are looking at 7380Gms (49.33AU, which is 20 AU from it's minimum of 4447Gms), then we are talking about 50 feet from the table, and we are up to 70 miles in distance. That's about Jasper TN, or maybe turning unto I-24 and heading up towards Chattanooga.

Eris, the largest of the dwarf planets (who are relatively close together considering the large distance to get to them...relatively, and so I skipped the others: ), is 68AU away. That puts us as 68 feet from your dining table, nearly 23 yards. That's 95.2 miles. We are past Chattanooga now and maybe heading down to Atlanta on I-75 (back to the flying crow, we are around Nashville, if we went roughly straight up). Again, that's as far from Pluto's mean orbit (40AU) as more than Uranus is from the Sun. Sedna, currently at 88AU, is likely to be a distant dwarf planet. We are now 88 feet from your table, about a third of a football field, and we are talking about 126 or so miles. Heading south on 65, say, are a handful of miles south of Alabaster. Sedna's mean, however, is believed to be around 500AU, 6 times it's current. We would be off the coast of Florida and somewhere in the Gulf (taking 65, down). In our "Atlanta" bound road trip, we are talking about 700 miles. We could have been there and back a couple of times. Let's say we got to Atlanta and headed south towards Miami. We would have made it! In terms of our dining room table, we are well over a football field away, the inner planets (if you remember) fitting in the space roughly taken up by the line that marks the inzone (Mars, at 1.5 feet, would only be a slight bit past it).

And now we come, finally, to the Oort cloud, the hypothetical cloud of comets and other materials that make up the edge of the Solar System, where the Solar Wind is so weak that it is bowed back, itself, by the overall assault of cosmic rays. The inner edge is roughly estimated to be about 2000AU. Back to our table model, we are talking about 2000 feet just to the inner edge. That's, going back to early moments in this exercise, as far from your kitchen table as our "Mercury", Quail Pointe, was from UAH. In terms of miles, that's 2800. That's roughly the East coast of New York to the West coast of Oregon. It's outer edge, by the way, is just about anybody's guess, but some estimates put it about 50,000AU. 25 times its inner. That makes it as far from your dining room table as the corn Maize is from UAH, assuming you follow the roads. What's more, with 1AU = 8 light minutes (it takes light 8 minutes or so to reach us on the Earth, from the Sun), then 50,000AU = 400,000 light minutes. That's 6667 light hours, 277 light days, and .76 light years. To the edge of the Solar System.

To continue this expansion, we are 271,000AU from Proxima Centauri. 51.3 miles from your dining room table (yes, eagle-eyed readers, that means the Solar System itself, assuming you count Oort in with it, is about 1/5th the way to Proxima Centauri). My walk from UAH would put me at 379.4 thousand miles. I would have walked around the earth 15 and a quarter times. I would be tired. TIRED!

That's the closest star. Sirius, the brightest star and still relatively close, is about ten or eleven times as far from the Sun as the Oort cloud. Some estimates put the Milky Way's center at 26000 light years (1,640,000,000AU if my math holds). I've now completed about 49,000 trips around the Earth. From your dining room table, we are talking about 310,000 miles. That's somewhere past the orbit of the Moon.

And everyone says science is boring.

Si Vales, Valeo


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