# Volume of observable universe

1. Nov 25, 2006

### brandon26

This question seems simple but I cannot recall the formula to solve it. I hope someone can help me:

If the age of the universe is 1.4E10 years, estimate the volume of the observable universe?

Urgent help required.

2. Nov 25, 2006

### PMP

Maybe you don't need formula. Think for yourself. That's for what physics exist. If the age of the universe was one year, ...

3. Nov 25, 2006

### brandon26

Maybe not. But how else am I supposed to work this out? Do I need to know the rate at which the Universe expands??

4. Nov 25, 2006

### brandon26

5. Nov 25, 2006

### andrevdh

I think the keyword might be observable.

6. Nov 25, 2006

### brandon26

Ok. I gave it a little thought and worked it out. The volume of the obserbavle universie is 9.73E78 m^3.

But the question carries on. It goes:

A beach is 1km long, 10m across, and 1m deep. One sand grain occupies 1cubic mm. which is the larger number:

The number of stars in the observable universe or the number of grains of sand on the beach?

What about the number of galaxies compared to the number of sand grains?

I worked out the number of sand garins which is 10E13. How do I calculate the number of stars or galaxies??

Last edited: Nov 25, 2006
7. Nov 25, 2006

### brandon26

8. Nov 29, 2009

### lilacpurple

like, do we assume the universe is a sphere or do we assume its flat?

9. Nov 29, 2009

### lilacpurple

apparently its flat, but then how do u calculate the volume?

10. Feb 14, 2011