# How many miles is the universe across?

Dec 22, 2016

The observable universe is approximately $5.4 \times {10}^{23}$ miles in diameter.

#### Explanation:

In one second, light travels about $186000$ miles (in vacuum).

There are $86400$ seconds in each days, so in one day light will travel:

$86400 \cdot 186000 \approx 1.6 \times {10}^{10}$ miles

One year is approximately $365$ days, so in one year light will travel:

$365 \cdot 1.6 \times {10}^{10} \approx 5.8 \times {10}^{12}$ miles

The observable universe is approximately $93$ billion light years across, so:

$9.3 \times {10}^{10} \times 5.8 \times {10}^{12} \approx 5.4 \times {10}^{23}$ miles

That's $540 , 000 , 000 , 000 , 000 , 000 , 000 , 000$ miles