Estimating observable universe volume from its age

[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.

 

[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, ...

 

[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??

 

[brandon26]

errrm. Can someone please be a little more helpful than that?? Please??

 

[andrevdh]

I think the keyword might be observable.

 

[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??

 

[brandon26]

Someone Please Offer Some Advise!

 

[lilacpurple]

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

 

[lilacpurple]

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

 

[CrusaderLee]

Well, even if its flat and based on acceleration, we can assume it is like a cylinder only with a torus edge, or if the dark energy accelerate proportionality into a sphere that would be a lot easier then trying to calculate the volume based on a half cylinder and half torus universe... sorry, I'm a noob here.