# Age of The Universe!

1. Mar 30, 2010

### NeedPhysHelp8

Hi all,
Hoping you can help with this problem!

1. The problem statement, all variables and given/known data
For a flat universe, show that $$t_{0}=2/3 (H_{0})^{-1}$$ ? Seems like a simple problem I just don't really know where to start.

2. Relevant equations
Hubble's law $$v= H_{0}r$$
and then $$t= 1/H_{0}$$

3. The attempt at a solution
I just need guidance where to start. Flat universe means that expansion is constant in any direction right? What do I do?

2. Mar 30, 2010

### mgb_phys

flat universe means the hubble constant is constant.

Then 1/hubble constant has units time.
Think of the equations for something that doubles/halves with a constant time interval

3. Mar 30, 2010

### NeedPhysHelp8

How about the kinematic equation: x(t)= vt + 1/2at^2
Not sure if this is right and what to do with it? maybe take a derivatives of both sides???

4. Mar 31, 2010

### NeedPhysHelp8

I still can't figure out the answer, can someone give me a hint please