Distances Not Named

dj13 · Feb 20, 2005

A simple question. Is there a common term in relative general use which describes some distance between an A.U, and say a Light Day. In particular I am wondering about a term describing either the radius or the diameter of our solar system. Is there perhaps a SSU (solar system unit)? Once I get the answer to that question I will feel a bit better using such a term in asking the next question I have, which will be "Is there any way to superimpose over some of the esquisite photos available in the world some image which would show that SSU so that the viewer might gain a better idea of the relative size of the object being viewed?" Like a picture of a bug vs a picture of a bug next to a dime. I can guess that on most of those pictures an A.U. would probably not be visable, but perhaps it would, and that would be very interesting to know and understand.

qzzq · Feb 20, 2005

There is no common term to describe a certain unit of distance inbetween a Astronomical Unit and a light year/day. An AU is about 8 light minutes. An Solar System Unit? Well, I like the idea, but the difficulty will be in determining our solar system's size. It varies due to changes in solar wind intensity. It's not a perfect sphere, far from it. And the outer edge would be at approximately one light day...so the current scale suffices. <div class="Discussion_UserSignature"> *** </div>

Saiph · Feb 20, 2005

as qzzq said, there isn't an official unit. You can say something is about the size of the solar system (commonly considered out to pluto, despite the fact there is other stuff out there and it is an incorrect boundry). The best method is to use light-units. Light seconds, minutes, hours, days, months, years. They all work, and give plenty of flexibility. In almost all images in astronomy, even a unit the size of a solar system would be way to small. Take the famous Eagle Nebulae (the pillars of creation hubble image). Each finger is, IIRC, 25 light years long. Compared to the few light hours (at most) our solar system is...that's huge. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

alokmohan · Feb 21, 2005

qzzq where are you hiding?I agree with your views.I remain humble asteroid for ever.

aaron38 · Feb 22, 2005

Pluto's about 40 AU out and that is basically what the general public considers the edge of the solar system. So round up to 50 and call the diameter of the solar system 100 AU Then one can use metric conventions. I don't know if it's kosher or not, but one could say that the diameter of the solar system is 1 hecto-AU. On second thought that'd probably just confuse people because hecto isn't much used.

dj13 · Feb 22, 2005

Thank you for the info, I like aaron38's reply best. I understand the Oort Cloud is considered part of our Solar System, perhaps the diameter of the average outer marker to that cloud might be something to name an O.U (for Oort Unit), or S.U. (System Unit). Imagine how much easier and more relatable it might be to use such nomenclature. But the real point to my question was to find a way to get relative sizes associated with the lovely pics we all admire. Without having to take an astornomy course, or dig deep into existing literature. The problem with light years, or light months, or days, or hours is that they mean nothing to the average person except they are all very long distances. Until we start measureing the speed of our cars, or the distance to the 7-11 in light seconds we as simple humans need to deal with relatable concepts. About the largest unit we deal with currently and can actually imagine is the A.U. and by now most folks have an idea it is around 8 minutes light speed. But the A.U. still relates more to actual miles than the distance a photon travels. Somehow it would be beneficial to the populace which pays the taxes to fund the research to have that relative size info available. With the persistance shown of late it will not be long before actual planets around other stars might be photographed. When that happens a standardized way to simply impart the relative size of our solar system will be most welcome. Like the photo of a bug with a dime in the picture, vs the same bug in a picture alone. That image of the dime speaks volumns.

Saiph · Feb 22, 2005

The problem that arises with using system units is a similar one. People rarely have a solid grasp of the size of our solar system. Only slightly more often do they grasp the distance to our own moon, let alone the sun (or pluto!). Also you run into the problem of very large numbers. If I tell you the moon is 384,000 km from earth, it doesn't really hit home how far that is. If I say that's about the width of 30 earths, side by side, you begin to see it. Then you say the sun is ~1 million miles across, or a bit over twice the distance to the moon (~100 earths!). The distance to the sun is 1 AU, or 93 million miles, or 93 sun's side by side (which is 9,300 earths away). You have to do all that to build up to an AU. Only after you do that, does the size of the solar system often hit home. But I understand your point. I've often said a light year is the distance light travels in a year, or ~6 trillion miles. And the object we're looking at is x ly away. My audience says, "Is that out past pluto?". So I understand completely. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

spayss · Feb 23, 2005

"Also you run into the problem of very large numbers...' Excellent point. Large numbers are for mathematical use and not perceptual comparison. Even in a group of scientists, remove a decimal from a number that describes the physical size of the universe and nobody will probably notice even though you've reduced all of existence by 10 times. We are products of our physical evolution and our perceptual skills are limited by our senses. Senses that aren't evolved to deal with items smaller than a grain of sand or farther across than a few weeks walking.

glutomoto · Feb 23, 2005

Thank you all for reminding me of the following link, which is a great illustration of Distances Not Named. View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons. Welcome to OnlineConversion.com Convert just about anything to anything else. Over 5,000 units, and 50,000 conversions. <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

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