APOD: To Scale: The Solar System (2015 Dec 25)

[APOD Robot]

To Scale: The Solar System

Explanation: Want to build a scale model Solar System? A blue marble 1.4 centimeters (about half an inch) across would be a good choice for a scale model Earth. Since the Sun is 109 times the diameter of Earth, a 1.5 meter diameter balloon could represent the Sun. But the distance between the Earth and Sun, 150 million kilometers, would translate to just under 180 meters (590 feet) at the same scale. That would mean the completed project, including the orbits of the outer planets, is probably not going to fit in your backyard. Still, you might find enough room on a dry lakebed. Check out this video for an inspirational road trip through the Solar System to scale.

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[roaringhotvermilion]

I commend these guys on their dedication to the task of actually building (the first ever?) scale model put into motion. The quality of the video was great, too. The inclusion of the Cronkite footage and the astronauts' scale related comments were marvelous touches.

I was slightly disappointed that the first two discovered dwarf planets weren't shown, but I can understand that time available and the number of drivers available were limiting parameters.

Since the movement of the "planets" in the video was clockwise, I wonder why they chose to depict it as seen from slightly below the plane of the ecliptic rather than from above.

[BMAONE23]

I made one of these in virtual space with all bodies and orbits to scale including the orbits of Jupiter's 67 moons and at least 61 of Saturn's moons, Using Autocad.

[Ann]

I made a poor man's (or a poor woman's) real-life version of the inner solar system, using cotton balls, peas and a "home-made" table cloth.

I started off by using my very poor math and some googling to figure out the relative sizes and distances between the Sun, Mercury, Venus, the Earth and Mars. I decided that I could approximate the relative sizes of the Earth and the Sun as 2 centimeters (0.02 meters) and 2 meters, and I could also approximate the distance between them as 200 meters. Nice! I also decided that I could approximate the distance between Mars and the Sun as 300 meters.

Click to view full size image

Finding a 2 centimeter diameter blue ball for Earth wasn't hard. I just went to the the supply room of my school and helped myself to some cotton balls (the school keeps them for the students whose future job will be to take care of and play with children). I took a blue one for the Earth, a white one for Venus (yes, the school has white ones, too) and a red one for Mars. I cheated and decided I would pretend that Mars is comparable to Earth and Venus in size. (Actually I sort of started from the cotton balls, and because they were 2 centimeters in diameter, not 1.5 centimeters, I had to scale everything up from about 1.5 (like the ~150 million kilometer distance between the Earth and the Sun, the ~13 thousand kilometer diameter Earth and the ~14 million kilometer diameter Sun) to 2.)

What about the Moon and Mercury? I couldn't pretend that they were the same size as the Earth and Venus, so I bought myself some yellow peas. They had to stand in for the Moon and Mercury.

Click to view full size image

But getting myself a huge two-meter-in-diameter beach ball for the Sun proved too hard. If by any chance I had found one, I wouldn't have been able to handle it. And it would have been brightly colored in a way that would just confuse people.

So I ended up buying some yellow fabric for the Sun. (Of course it shouldn't have been yellow, but white, but the white color would also have confused people. I cheated, took the easy way out, and settled for yellow.) I then asked a teacher at my school who teaches textile design to sew a round yellow table cloth, two meters in diameter, of the fabric. She did it for me. The 2 meter yellow table cloth would serve just fine as the Sun, if two people held it up for me.

I had calculated the distances to Mercury, Venus, the Earth and Mars, as well as the distance between the Earth and the Moon. (The latter was about 60 centimeters, 0.6 meters, if I remember correctly.) The distance from the Sun to Mercury was about 80 meters, while the distance to Venus was about 140 meters, the Earth was 200 meters away and Mars 300. I just stepped the distances to get the "planets" in the correct position from the "Sun". I think I did fairly well, because the "Sun" looked really quite right in size from a distance of 200 meters!

The guys in today's APOD did a truly great job with their real-life model, and the video is a very fine and instructive APOD!

Ann

[MarkBour]

Cool video, and great to hear of BMoane's and Ann's similar efforts. I'd love to find a place where one could set up a more permanent version of this. A true-to-scale orrery. I guess an American desert might be an ideal place for it. For their project they needed about a 7 mile diameter region, and the earth was still disappointingly small. I wonder where one could build anything larger (on the Earth's land surface) and get a similar excellent clear view such as they had in the place they chose (maybe the Bonneville salt flats?). I wonder how they plotted out the orbits in the sand.

[Whiskybreath]

Terrific. I'd love to do the same, but Northern Ireland doesn't have too many flat, dry deserts...

[RedFishBlueFish]

... a (blue) marble floating in the middle of nothing ...

Nice

Bit of an embarrassment though that there are no women who have seen the earth as a circle, even more of an embarrassment that we are coming up on half-a-century past since anyone has done so.

[Skill57]

Thanks for the terrific Christmas present!

[De58te]

They seem to point out that their scale model is accurate by comparing it to the sunrise. However I think they seems to be in error when Wylie said they needed 7 miles to fit in Neptune's orbit. If in the scale model an Astronomical Unit is 579 feet, (APOD said 590) and Neptune (I have to look it up) is 30.0611 a.u. away (Wikipedia says 30.1 so I'll go with that) then 579 times 30.1 divided by 5280 = 3.3 miles. So that means Neptune's orbit has a diameter of 6.6 miles in the scale model. Sure it is just 2/5th of a mile difference, but that's still bigger than your backyard. I think they just rounded it off, but rounding 6.6 miles into 7 miles is a bit sloppy when they show you a blue marble with the continents on it.

[Greggfla]

Well Done, very very impressive.

[stowaway]

I started making scale models of the Solar System back in the early 80s. I did it with drawings on a large roll of butcher paper but found I still had to draw gaps which represented millions of miles or the roll of paper would have been too large. The scale I used was close to what these guys used; Pluto's mean distance was about 8-1/2 miles. Later I did it on autocad as an earlier person commented they had done. Other methods were to simply establish landmarks for the orbits along my drive to work. Living in Nevada, I always wanted to do what these guys did but I would have wanted to do it where more people could have accessed it, such as somewhere alongside hwy 95. That would not include the circles but just the size and distances. If I remember correctly, on this scale, the nearest star is about halfway to the moon. Lots of fun and also humbling, to be able to visualize how small we are
and how important is Miss-ed Universe

[Onewholooksup]

In Anchorage Alaska, a man designed and convinced the city to build a scale model of the solar system back in the early '80s, if I recall correctly. It still stands. The sun is about 10-12 feet in diameter and rests by the main performing arts center downtown and Pluto is a long walk away at the main airport. Earth is a carefully painted "blue marble" of about an inch in diameter, maybe a bit less. The installation has a placard alongside each planet (which rest on pylons raised to about eyeball height) to explain some basics of the planet. It is amazing to walk the route, though I admit I got tired and turned back at Jupiter. The installation is laid out along a bike trail and runs a course of 6-10 miles, so go in the summer and rent a bike, or take your skis in the winter and see it that way. The scale is approximately one step of a person equals 1 light second of distance.

[Celeste Kent]

While it is clear the mathematics works out, it defies intuition. Given the immensity of space how can gravity so profoundly affect those little specks of matter so far away. Science has yet to explain for us just how gravity actually works, when and if we ever do figure it out it just might offer the human race the most profound boost to our ability to control life for ourselves.

[Chris Peterson]

While it is clear the mathematics works out, it defies intuition. Given the immensity of space how can gravity so profoundly affect those little specks of matter so far away. Science has yet to explain for us just how gravity actually works, when and if we ever do figure it out it just might offer the human race the most profound boost to our ability to control life for ourselves.

Your intuition failure is yours, not science's. In fact, gravity is extremely well understood- one of the greatest triumphs of modern physics. Gravity is an extremely weak force, and it is the product of a distortion of spacetime by mass. A distortion that precisely explains the behavior of those "little specks of matter".

[webolife]

Nice video. I've done scale modeling with students on a half kilometer radius stretch, with a sun about the size of a softball at one end.

Chris, how is gravitationally warped space-time intuitive, for scientists or anyone??

I felt the desert demonstration would have been even better if they had simulated in the relative orbital velocities of the planets in some way, say like driving around Earth's orbit in one minute, then scaling the other planets' speeds to match...

[Chris Peterson]

Chris, how is gravitationally warped space-time intuitive, for scientists or anyone??

Well, that depends on the individual. Certainly, when you have spent time studying a subject, your intuition changes, and things may be very intuitive to you that are not to others.

However, that wasn't my point. The point was that we can have a rich knowledge about something without any intuitive understanding at all. We do understand how gravity works, even if the mechanism is not intuitive for many people (although it is for some).

[ta152h0]

remember the vid describing a voyage at the speed of light from the Sun outward ?

[hamilton1]

Gravity is an extremely weak force, and it is the product of a distortion of spacetime by mass. A distortion that precisely explains the behavior of those "little specks of matter".

Hmmm or maybe the distortion describes the behaviour of matter rather than explains it. The juxtaposition of those two words inherent in many scientific theories is frustrating, but at the risk of venturing into philosophy I'll leave it there.

[wp2n-Craig]

very informative as to the scale of our system, however, all the orbits were going clockwise...
All solar sys objects, not only orbit counterclockwise, but rotate that way as well...
which goes to prove that god, if there is one, is left-handed ...

Peace, Love and Tread softly on our big Blue Marble ...

[Chris Peterson]

very informative as to the scale of our system, however, all the orbits were going clockwise...
All solar sys objects, not only orbit counterclockwise, but rotate that way as well...

Only when viewed from one side, which is completely arbitrary. Viewed from the other side, they rotate clockwise. Since there's no obvious structure on the planet models to define the north or south side of the ecliptic, the direction of rotation is an arbitrary choice. We're simply seeing this model from south of the ecliptic.

[geckzilla]

The solar system where Australia, fed up with north-centric ideals, declared war on the rest of the world and took everyone by surprise, establishing its supremacy and flipping the maps.

[ta152h0]

my right hand rule side is on the right side of me

[DavidLeodis]

The image of the Earth brought up through the "blue marble" link is awesome (just like similar images). I doubt I will ever tire of seeing such wonderful images.

[Visual_Astronomer]

Gravity is an extremely weak force, and it is the product of a distortion of spacetime by mass. A distortion that precisely explains the behavior of those "little specks of matter".

Hmmm or maybe the distortion describes the behaviour of matter rather than explains it. The juxtaposition of those two words inherent in many scientific theories is frustrating, but at the risk of venturing into philosophy I'll leave it there.

Precisely. GR provides a very accurate description of the behavior of matter, but it is a mistake to confuse reality with a mathematical model of it. I have no fear of philosophy!

[Chris Peterson]

Precisely. GR provides a very accurate description of the behavior of matter, but it is a mistake to confuse reality with a mathematical model of it. I have no fear of philosophy!

Or perhaps, it is a mistake to believe there's a difference between the two.