Scale in Space

It is difficult to fully grasp the concept of scales that are involved in space. The ratio of empty space to matter is HUGE! The size of planets and even stars is dwarfed when compared to the space between them. We try to understand things and visualize them by comparing them to other things that we know well.

A good introduction to this issue is “The Thousand-Yard Model” which describes our solar system as a model based on a thousand yard radius from the Sun to the orbit of Pluto. This gives a scale of 1 inch = 100,000 miles. Using this scale, here is a list of some familiar objects and their positions:

Sun – distance = 0, size = 8 inch ball (bowling ball)
Venus – distance = 19 yards, size = peppercorn
Earth – distance = 26 yards, size = peppercorn
Mars – distance = 40 yards, size = pinhead
Jupiter – distance = 135 yards, size = pecan
Saturn – distance = 247 yard, size = acorn
Neptune – distance = 777 yards, size = peanut
Pluto – distance = 1019 yards, size = pinhead

Place a peppercorn (Earth) 26 yards away from a bowling ball sized object (Sun) and you can start to appreciate the scale involved.

——Galaxy scale
Once we move beyond our own solar system, the scale ratio has to be greatly increased to handle even greater distances. The Oort cloud is a spherical cloud of comets that surrounds our Sun and extends to distances of around 11 trillion kilometers. The nearest star is Proxima Centauri which is about 40 trillion kilometers away. These numbers are too large to handle easily. The next logical step up is using light years. Proxima Centauri is about 4.3 light years away from us. Our galaxy, the Milky Way, contains about 200 billion stars in a fairly flat, spiral arm configuration that is about 100,000 light years in diameter.

A Sense of Scale

Galaxies combine to form groups, clusters and super clusters. Our Milky Way is in a group of 40 galaxies that we call “the local group”. Groups contain up to 50 galaxies. Clusters contain from 50 galaxies up to few thousand galaxies and more than that is considered to be a supercluster.
There may be ten million superclusters of galaxies in our universe.

If we use light years to compare diameters, we get the following:
Our solar system is 14 light hours across or .002 light years
Our galaxy is 100,000 light years across
Our local group of galaxies is 4,000,000 light years across
Our super cluster of galaxies is 150,000,000 light years across

Large-scale structure of the cosmos

——Solar System scale
A Solar System Scale Model Meta Page

——Asteroid belt scale
To understand the scale of the asteroid belt, it seems convenient to use light minutes to measure the radius of orbital paths. Earth has an orbital path that is about 8 light minutes out from the Sun. Mars is about 13 light minutes out and Jupiter is about 43 light minutes out. The asteroid belt occupies the empty space between Mars and Jupiter and can be described as follows:
Asteroid belt inner edge is about 17 light minutes out
Asteroid belt outer edge is about 33 light minutes out
Asteroid belt height/thickness averages around 7 light minutes

——See also:
Drake equation
Belt Geography

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