I once heard there are more stars in the universe than grains of sand on earth. Bloody impossible I say??

Question

Anyone????

Answer 1

That's a tough call. But let's take a look anyway.

Our galaxy alone contains somewhere in the neighborhood (no pun intended) of 300 to 400 billion stars. Now the estimated number of galaxies in the Universe is around 125 billion. Now let's do some math (based upon the assumption that the Milky Way is an average sized galaxy):

(3.5 x 10^11) x (1.25 x 10^11) = 4.375 x10^22

Thats 43,750,000,000,000,000,000,000

So are there more grains of sand on the Earth? Probably... but some of the above answers lead me to believe that it's a close race. You do have to keep in mind that the Universe is expanding constantly.

Also, some have mentioned that the Universe is infinite. However, if you subscribe to the idea that the Universe is expanding then I would like to point out that you cannot believe it is infinite. The two ideas are incompatible.

Answer 2

And why do you say that? (The correct saying is there are more stars than sand in all the beaches on the earth)

There are about 100 billion stars in our galaxy and about 100 billion galaxies which means there is somewhere around 10,000,000,000,000,000,000,000 Stars - which is quite a lot.

Let's say a grain of sand in a tenth of a millimetre across. If there were the same number of stars as grains of sand the sand would have a volume of 10 billion cubic kilometres which is more sand than on all the beaches on earth.

Extra.
katjha2005's - there is only ONE star in the solar system and that's the sun. Oh and the universe is NOT infinite just really big

Extra Extra

I noticed another comment about how do I know that the universe isn't infinite. Well given the Big Bang is correct (and if you want to can can explain why) and the universe has expand from a point from then on, the universe must have a finite size. Because all the matter was created in the big bang there must be a finite number of stars.

Hope that clears that up for everyone.

Answer 3

A couple corrections to the above.

There's a lot more than one sand grain per cubic millimeter---depending on the size of the sand grain, somewhere between 50 and 1000. Let's say it's 100. Then to equal the number of stars in the Milky Way, you need about 10 cubic meters of sand---the capacity of a single truck.

The surface of the Earth is about 4x10^14 square meters, so the total amount of sand is maybe 10^15 to 10^17 cubic meters.
That's about 10^14 galaxies worth of sand. Maybe less, if you mean really nice, clean beach or desert sand.

There aren't 10^14 galaxies between us and our event horizon 13.7 billion lightyears out, there are (as people have pointed out) only about 10^12. But it's close.

However, the Universe is definitely bigger than our event horizon. We see one light-day further each day, and that light-day of stuff is just like the other stuff we see already. How much further does it go on? The current best guess, based on inflationary Big Bang models, is LOTS and LOTS---at least 10^20 times further, and possibly much more than that. Maybe infinite. That would argue that there are "now" at least 10^72 stars in the Universe, out to the point that was once in causal contact during the early inflation. Way, way more than all the grains of sand on the Earth.

Answer 4

Well, lets do some back of the envelope math, because these numbers are just way to big for any person to just say, "That sounds about right" or, "That sounds way wrong."

The Earth is about 6000 km in radius, or 6000000 meters. The surface area would be 4 * pi * 6000000^2 or about 4.5E14. If we can guess that there are enough sand grains to cover the Earth 1 meter deep, that is 4.5E14 cubic meters of sand. If a sand grain is 1mm, then there are 1000 cubed or 10E9 grains in every cubic meter, so there are 4.5E23 grains of sand on Earth.

Now the Milky Way galaxy is estimated to have 100 billion stars, or 10E11 stars. It is also estimated that there are 100 billion galaxies in the universe, again, 10E11. So multiplying those numbers gives 10E22 stars. That is 45 times less than 4.5E23. Now maybe you say that only 1/100 of the Earth is covered by sand 1 meter deep. Then there are more stars in the universe than sand grains on Earth. Of course all these numbers are not very well known, especially the number of sand grains on Earth, but the numbers do seem to be in the same ballpark.

Answer 5

That's a question I would consider an "imponderable". I think that the comparison of stars in the universe to grains of sand on the beaches is just a figure of speech to give the average person an inkling of just how enormous the universe is.

While it may not be "infinite", as some people have posited, it is certainly a size that is beyond the reach of the most creative imagination.

It is good to see people putting so much thought into questions like this!

Answer 6

I can't say I know that for a fact, because I'm not thinking someone has actually gone and counted every grain of sand and every star in the universe but if you look at the larger picture.. the Earth is actually very small so what seems like a lot to you in the bigger picture may not be that much. The universe is never ending - there are millions of stars just in our solar system alone much less the universe. There are different size star also, so some are "babies" and you can't see them... then you have stars the size of the sun that are obvious... so looking at the big picture I would have to say there's a good chance that it is probably an accurate statement.

Answer 7

This might help. This is a picture from the Hubble telescope called the Hubble Deep Field. It's a picture of all the galaxys that show up in a segment of sky that is only the size of a grain of sand if you hold about an arms length away. It's an incredibly small area, yet there are about 10,000 galaxies in it. Galaxies contain between ten million to one trillion stars. Estimates of the number of grains of sand are about 2000 billion billion, max.

Answer 8

There are 1,000,000,000,000,000,000,000 stars in our universe

mathematicians at the University of Hawaii tried to guess how many grains of sand are on the world's beaches. They came up with 7,500,000,000,000,000,000, or seven quintillion five quadrillion grains of sand.

1,000,000,000,000,000,000,000 stars
7,500,000,000,000,000,000 grains of sand

so to every 1 grain of sand there is 133 stars

the universe is a wee bit on the large side, if i think about to much i get a pain in the head. thank god you didn't ask for how many atoms are in the universe?

Answer 9

true the universe is ever growing and there's a theory that the universe started growing when the big bang happened and eventually its just going to stop growing and like a elastic band retract and destroy everything like it created everything as it grew so until the universe stops growing more and more stars will be created but on earth were basically stuck with the same amount of sand

Answer 10

There are over 600 billion stars in our Galaxy and then there are over 50 billion Galaxy's and that's just the ones that we can just see with Hubble and other space telescopes.
If you do the math that's one hell of allot stars and earth the place we live on its tiny!. We are nothing compared to the size of the universe.