# The Universe scaled down **URL:** \ **Category:** Factual Questions\ **Created:** [August 21, 2004, 10:49pm UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901 "2004-08-21T22:49:45Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Stana\_Claus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stana_claus/32/13874_2.png) [@Stana\_Claus](https://boards.straightdope.com/u/Stana_Claus)\ **Post date:** [August 21, 2004, 10:49pm UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/1 "2004-08-21T22:49:45Z")
I saw a show on TV a while back where some town modelled the solar system in their town. They had the Sun represented by a large sphere placed in the center of the town. Mercury was located _x_ blocks away and was the size of a golf ball, Venus a bit further out and a bit bigger, etc. Pluto was several miles outside of town and quite small, if I remember correctly. So, taking that concept a step further, if the Universe were scaled down to be the size of the Earth, how big would the Earth be? As big as a grain of sand? Smaller than that? And, while we’re at it, how far would our space exploration to date extend in this scale? SC ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 22, 2004, 1:57am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/2 "2004-08-22T01:57:56Z")
1. We don’t know the size of the Universe. We don’t even know for sure whether it is finite or not. (Scaling down an infinite Universe would be a neat trick.) While you might see some references to the Universe being ~14MLYr in radius, that is the _visible_ Universe (from our perspective). 2. See 1. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 22, 2004, 2:24am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/3 "2004-08-22T02:24:51Z")
**ftg** is right. But if we shrink the visible universe to the size of the earth, earth would be about 1/500 the size of a water molecule. The furthest space probe is the Voyager 1, currently around 90 AU away (almost 2x the distance to Pluto); this translates to about 0.6 microns, roughly the size of a very fine smoke particle. The distance to the nearst star would be about 1.8 mm (1/16 inch). ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [August 22, 2004, 2:33am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/4 "2004-08-22T02:33:02Z")
Was the OP thinking of [this](http://www.innovations-report.com/html/reports/physics_astronomy/report-30980.html)? A scale (1:15m) model of the solar system across the UK…the earth and the sun are six miles apart, but pluto is the other end of the country. ---
**Author:** ![Stana\_Claus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stana_claus/32/13874_2.png) [@Stana\_Claus](https://boards.straightdope.com/u/Stana_Claus)\ **Post date:** [August 22, 2004, 2:59am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/5 "2004-08-22T02:59:25Z")
Thanks for the responses folks. I knew we were pretty insignificant in the grand scheme of things, I just didn’t know how much. And **GorillaMan** , the one I saw wasn’t nearly as big as the one you linked to. I’m impressed. So, how about a followup question. Rather than scaling down the entire visible universe, how about just the Milky Way galaxy? If it was the size of the earth, how big would the earth be? SC ---
**Author:** ![Stana\_Claus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stana_claus/32/13874_2.png) [@Stana\_Claus](https://boards.straightdope.com/u/Stana_Claus)\ **Post date:** [August 22, 2004, 3:03am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/6 "2004-08-22T03:03:26Z")
Oops, forgot to add the other question. If the Milky Way was the size of the Earth, how far would Voyager have gotten by now? Thanks again, all. SC ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [August 22, 2004, 3:18am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/7 "2004-08-22T03:18:03Z")
> [@Stana Claus](#): > > So, how about a followup question. Rather than scaling down the entire visible universe, how about just the Milky Way galaxy? If it was the size of the earth, how big would the earth be? Taking a reasonable figure of 25000 light yeras for the Milky Way disc, reduced to the size of the earth, the earth is (I think?!) about 50 picometres wide. ---
**Author:** ![Stana\_Claus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/stana_claus/32/13874_2.png) [@Stana\_Claus](https://boards.straightdope.com/u/Stana_Claus)\ **Post date:** [August 22, 2004, 3:29am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/8 "2004-08-22T03:29:33Z")
And, as long as I’m padding my post count, [here](http://www.bradley.edu/las/phy/astronomy/about_solar.html) is a link to the solar system model I mentioned in the OP. Not as big as **GorillaMan** ’s, but pretty impressive nonetheless. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 22, 2004, 5:25am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/9 "2004-08-22T05:25:33Z")
> [@GorillaMan](#): > > Taking a reasonable figure of 25000 light yeras for the Milky Way disc, reduced to the size of the earth, the earth is (I think?!) about 50 picometres wide. You’re confusing a couple dimensions. The diameter of the Milky Way is normally given as about 100,000 LY. The solar system is believed to be about 26,000 LY from the galactic center. That said, let’s see… If we shrink the 100,000 LY Milky Way to the current size fo the Earth, we end up with Earth being a speck just 1.71 x 10[sup]-7[/sup] meters, assuming I’ve done the math correctly at this late hour. ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [August 22, 2004, 11:49am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/10 "2004-08-22T11:49:51Z")
> [@Q.E.D.](#): > > You’re confusing a couple dimensions. … assuming I’ve done the math correctly at this late hour. Dammit, it was too late to be dealing with light years. 😃 ---
**Author:** ![rippingtons\_fan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rippingtons_fan/32/11767_2.png) [@rippingtons\_fan](https://boards.straightdope.com/u/rippingtons_fan)\ **Post date:** [August 24, 2004, 11:12pm UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/11 "2004-08-24T23:12:52Z")
One scale comparison I heard of a while back is:… If the distance across the little finger represents the distance between the Earth and the Sun, then, on that same scale the nearest star would be 2 miles away!! ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [August 25, 2004, 12:25am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/12 "2004-08-25T00:25:13Z")
The Milky Way is 100,000 light-years in diameter. That’s about 6x10^17 miles. (Yes, I know I should do this in metric. But I remember the length of a light-year in miles and the Earth’s diameter in miles. The units will cancel out anyway in the scaling factor.) The Earth is about 8000 miles in diameter. Voyager 1 is 88 astronomical units (1 astronomical unit or AU = distance from the earth to the sun) or about 8x10^9 miles. The scaling factor for your galaxy model is about 1.3x10^-14. The earth is about 13,000 kilometers in diameter, so in this scale model it is 1.7x10^-10 meters in diameter. That’s on the order of the size of a hydrogen atom :eek: Voyager 1 is about 18 centimeters from the sun in this model (its distance from the earth would vary during the year). I love scale-model solar systems! 😃 ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [August 25, 2004, 12:35am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/13 "2004-08-25T00:35:01Z")
whoops, mixed up my meters and kilometers :o It’s 10^-7 meters, not 10^-10. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 25, 2004, 5:40am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/14 "2004-08-25T05:40:54Z")
> [@](#): > > And GorillaMan, the one I saw wasn’t nearly as big as the one you linked to. I’m impressed. That’s nothing! I once saw a scale model of the Solar System that was millions of times bigger than **GorillaMan** ’s! The comparison I like the best turned the Sun into an orange sitting in a refrigerator in Cleveland, which would make the nearest other fruits, er, stars another orange, a tangerine, and a cherry somewhere in Milwaukee. ---
**Author:** ![hammerbach](https://avatars.discourse-cdn.com/v4/letter/h/73ab20/32.png) [@hammerbach](https://boards.straightdope.com/u/hammerbach)\ **Post date:** [August 25, 2004, 6:02am UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/15 "2004-08-25T06:02:07Z")
One of my favourite essays is Asimov’s _A Matter of Scale_ from the essay collection _Science, Numbers and I_. He addresses exactly this topic. One of the friendlies treatments I’ve come across. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [August 25, 2004, 3:50pm UTC](https://boards.straightdope.com/t/the-universe-scaled-down/260901/16 "2004-08-25T15:50:38Z")
If you modeled the entire universe to the size of the earth, let’s see…borrowing from **Anne Neville’s** figures and somewhat arbitrarily assigning a value of 30 billion light years for the diameter of the universe (I think there start to be problems with the concept “diameter” when applied to “universe”, but I don’t think any objects more distant than 15 billion light years have been discovered…so let’s say our model of the universe will be from just a bit beyond our most distant known object to a point directly opposite that in a sphere…a radius of 15 billion light years = a diameter of 30 billion.) If I’m doing my math right, looks like there’s about 6 trillion miles per light-year. That would put the universe we’re modeling at 180 septillion miles across, and we’re making an 8000-mile spherical model of it, a ration of one to 0.000000000000000000000044444. Our galaxy, 100,000 light years converted to miles = 600 quadrillion, would occupy 0.0000266667 miles. Converted to yards, 0.046933333. Converted to feet, 0.1408. Converted to inches, 1.6896.