What does two trillion galaxies mean?

Perspective on our observable universe.

Hubble eXtreme Deep Field (XDF). Credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team
Hubble eXtreme Deep Field (XDF)⩘  – Image credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team


Think about our Milky Way galaxy and its 200 million stars.

Start by picturing our sun
(a relatively small star):

Now picture ten times as many suns:

✶✶✶✶✶✶✶✶✶✶

And ten times as many again.

✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶

And ten times as many again.

✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶
✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶ ✶✶✶✶✶✶✶✶✶✶

And ten times as many again, and again, and again, and again, and again.

And then double that.

Here's another way of looking at it:

1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000

200,000,000


With that in mind, think about our universe and its two trillion galaxies.

Start by picturing our galaxy and its 200 million stars again
(a relatively small galaxy).

Now picture ten times as many galaxies.

⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖

And ten times as many again.

⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖
⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖
⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖
⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖
⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖

And ten times as many again.

⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖ ⌖⌖⌖⌖⌖⌖⌖⌖⌖⌖

And ten times as many again, and again, and again, and again, and again, and again, and again, and again, and again.

And then double that. And then double that again.

1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
10,000,000,000
100,000,000,000
1,000,000,000,000

2,000,000,000,000

4,000,000,000,000


That's just our observable universe.

And that's just our universe …