MovieChat Forums > Science > Really Big Numbers... Is this right?

Really Big Numbers... Is this right?

posted 8 years ago by jubjub_13
5 replies | jump to latest

I made these calculations based on this incredible youtube video;

https://www.youtube.com/watch?v=EMLPJqeW78Q

and this NASA website;

http://htwins.net/scale2/

Lengths or Diameters

how many times bigger the sun is than a grain of sand;

690 000 000 000 times

or six hundred and ninety billion times (I found this particularily hard to believe, I would have thought it would have been a lot more than that.)

how many times bigger an electron is than a string (from string theory);

3 400 000 000 000 000 000 000 000 times

or three point four septillion times

how many times bigger the universe is than a human;

890 300 000 000 000 000 000 000 000 times

or eight hundred and ninety point three septillion times --------- Speaking in terms of length or diameter a 'gamma ray wave length' (which is 20 to 30 times smaller than the smallest atom) is as many times bigger than a string as the universe is bigger than a human.

how many times bigger vy canis majoris (the largest known star; so big that it would engulf the orbit of Saturn if placed in our solar system) is than the sun (an average star);

2 142 times

or two thousand one hundred forty two times

how many times bigger our solar system out to the kuiper belt is than the sun;

10 714 times

or ten thousand seven hundred fourteen times

how many times bigger the milky way galaxy is than our solar system out to the kuiper belt;

77 128 000 times

or seventy seven million one hundred twenty eight thousand times

how many times bigger a human is than a string;

106 250 000 000 000 000 000 000 000 000 000 000 times

or one hundred and six point two five decillion times

how many times bigger the universe is than a string;

94 594 375 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 times

or ninety four novemdecillion five hundred and ninety four octodecillion three hundred and seventy five septendicillion times

My big question is that if the universe is ninety four novemdecillion five hundred and ninety four octodecillion three hundred and seventy five septendicillion times bigger in diameter than a string than about how many string would fit into the volume of the universe? How would I calculate that? That would be a pretty big number I think.

And please don't bother talking about how no one knows the size of the universe and it's expanding and all that. I just took the figure 160 billion light years and used that I know some estimates are less like 93 billion light years is a figure I've often heard, and the visible universe is even less apparently. I just want to know how many strings are in the Universe?

[–] philo_sopher 8 years ago

I would like to recommend a tool called WolframAlpha which provides a huge amount of computable data and is fairly good at understanding plain language. It can calculate a lot of stuff like this automatically.

For example, it can tell you that you can fit about 10^40 grains of sand inside the sun:
http://www.wolframalpha.com/input/?i=(volume+of+sun)%2F(volume+of+grain+of+sand)

or that you can fit of the order of 10^81 people inside the observable universe:
http://www.wolframalpha.com/input/?i=(volume+of+observable+universe)%2F(average+volume+of+a+human)

To answer your question, you can very roughly think that a string occupying what is called a Planck volume, that is, the cube of Planck length which is the distance at which quantum effects of gravity become important and which is often thought to be the characteristic scale of string theory. So in order to find out how many strings can fit in the observable universe you just divide the volume of the observable universe by the Planck volume. The radius of the observable universe is about 46 billion light years or roughly 4.4x10^26 meters. You can get the volume (V) from the radius (r) by using the equation for the volume of a sphere (V = 4*Pi*r^3/3) which gives about 4x10^80 cubic meters for the volume of the observable universe (alternatively you can assume the universe to be a cube to make things easier, the difference isn't important for estimates like these). The Planck volume is about 4x10^-105 cubic meters. So by dividing these two we get about 10^185 strings inside the volume of the observable universe.

If we ask WolframAlpha it will tell us the same thing:
http://www.wolframalpha.com/input/?i=(volume+of+the+observable+universe)%2F(planck+volume)

Of course strings are hypothetical objects and we don't really know their real size of if the even exist.

Also, when you are doing such rough estimates it usually makes little sense to calculate things to very high precision because the uncertainties are very large anyway. So if you know that the radius of the observable universe is roughly 10^61 times the Planck length you can just take the ratio of the volumes to be the third power of that because you know that volume scales as the cube of length.

[–] jubjub_13 8 years ago

Holy thanks for the response I'll get back to you once and IF (big if) I can get my head around all that math (I'm a bit of a lamen or not really that smart to be honest, but this stuff still fascinates me) and also when I get some time. I have work for the next few weeks straight starting tonight. So I might be a while to think about this again.

One question though is - you said the universe is 46 billion light years but this site I pasted says it's 160 billion light years and other place and what I originally thought is it was 93 billion light years?

[–] philo_sopher 8 years ago

The observable universe is the region which the light has theoretically had sufficient time to travel through since the Big Bang. 46 billion light years is the radius of this region, so from us to the "edge". 93 bly is the diameter of this region from "edge" to "edge" (twice the radius). I've put "edge" in quotes because there isn't any real edge at that point, it's a distance we can theoretically observe but the real universe is likely much bigger.

I'm not sure exactly where the 160 billion figure comes from. I suspect it comes from a misreporting of a study by astronomer Neil Cornish and collaborators who tried looking for duplicate images in the sky. Basically the idea is that if the universe curves in on itself then light travelling in one direction would come to the place of its origin eventually just like you end up where you started if you sail around the world. If the universe curves in on itself in a similar manner and if it is small enough then light may have had enough time to travel all the way across since the Big Bang and come out the other side creating a double image of some features. The researchers didn't find such double images and put an upper limit of 78 billion light years for the diameter of the universe. However , this apparently got misreported as the radius and so some sources reported the universe as being 156 billion light years in diameter, which is incorrect.

TL;DR: 160 bly figure is wrong.

[–] Valerian (10484) 2 years ago

if the universe curves in on itself then light travelling in one direction would come to the place of its origin eventually
Experimental data had confirmed that the universe is Euclidean, not curved.

[–] jubjub_13 8 years ago

Wow thanks man the answers right there. I was hurrying and a little overwhelmed by the the math I guess before and missed that lol. Really cool. So that's

100 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 strings.

or 100 sexagintillion strings.