How Many Galaxies Are There?

Galaxies — those vast collections of stars that populate our universe — are all over the place. But how many galaxies are there in the universe? Counting them seems like an impossible task. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.

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Tau.Neutrino said:

How Many Galaxies Are There?

Galaxies — those vast collections of stars that populate our universe — are all over the place. But how many galaxies are there in the universe? Counting them seems like an impossible task. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.

more…

> an acceptable range is between 100 billion and 200 billion galaxies

Yep. Close to the number of stars in the Milky Way.

> Would the number of galaxies change with time?

Yep, but slowly.

> What about other universes?

Near infinite number of galaxies. ie. it could be exactly infinite or merely extremely large.

A minimum estimate within our inflationary bubble would be what? (pops out for calculator). The number of galaxies within our inflationary bubble would be close to 10^37 galaxies. Which is a lot bigger than 100 billion = 10^11 galaxies in our observable universe.

Nothing really new in the article, it’s just an ad for the Webb Space Telescope.

mollwollfumble said:

Tau.Neutrino said:

How Many Galaxies Are There?

Galaxies — those vast collections of stars that populate our universe — are all over the place. But how many galaxies are there in the universe? Counting them seems like an impossible task. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.

more…

> an acceptable range is between 100 billion and 200 billion galaxies

Yep. Close to the number of stars in the Milky Way.

> Would the number of galaxies change with time?

Yep, but slowly.

> What about other universes?

Near infinite number of galaxies. ie. it could be exactly infinite or merely extremely large.

A minimum estimate within our inflationary bubble would be what? (pops out for calculator). The number of galaxies within our inflationary bubble would be close to 10^37 galaxies. Which is a lot bigger than 100 billion = 10^11 galaxies in our observable universe.

Nothing really new in the article, it’s just an ad for the Webb Space Telescope.

Surely the answer is more than almost infinite, i.e. actually infinite, or nowhere near infinite, but still very very big.

How did you come up with 10^37?

A factor of 10^26 seems awfully big to be based on observational evidence. Are there perhaps a few assumptions embedded in that number?

The Rev Dodgson said:

mollwollfumble said:

Tau.Neutrino said:

How Many Galaxies Are There?

Galaxies — those vast collections of stars that populate our universe — are all over the place. But how many galaxies are there in the universe? Counting them seems like an impossible task. Sheer numbers is one problem — once the count gets into the billions, it takes a while to do the addition. Another problem is the limitation of our instruments. To get the best view, a telescope needs to have a large aperture (the diameter of the main mirror or lens) and be located above the atmosphere to avoid distortion from Earth’s air.

more…

> an acceptable range is between 100 billion and 200 billion galaxies

Yep. Close to the number of stars in the Milky Way.

> Would the number of galaxies change with time?

Yep, but slowly.

> What about other universes?

Near infinite number of galaxies. ie. it could be exactly infinite or merely extremely large.

A minimum estimate within our inflationary bubble would be what? (pops out for calculator). The number of galaxies within our inflationary bubble would be close to 10^37 galaxies. Which is a lot bigger than 100 billion = 10^11 galaxies in our observable universe.

Nothing really new in the article, it’s just an ad for the Webb Space Telescope.

Surely the answer is more than almost infinite, i.e. actually infinite, or nowhere near infinite, but still very very big.

How did you come up with 10^37?

A factor of 10^26 seems awfully big to be based on observational evidence. Are there perhaps a few assumptions embedded in that number?

The factor of 10^26 comes from the scale factor during cosmic inflation. Objects causally disconnected before cosmic inflation will be about 10^26 times as far away as the present observational horizon.

Um, did I forget to cube that because we’re talking volume rather than distance?

mollwollfumble said:

The factor of 10^26 comes from the scale factor during cosmic inflation. Objects causally disconnected before cosmic inflation will be about 10^26 times as far away as the present observational horizon.

Um, did I forget to cube that because we’re talking volume rather than distance?

So doesn’t that make it the maximum size of the inflationary bubble, rather than the minimum?

The Rev Dodgson said:

mollwollfumble said:

The factor of 10^26 comes from the scale factor during cosmic inflation. Objects causally disconnected before cosmic inflation will be about 10^26 times as far away as the present observational horizon.

Um, did I forget to cube that because we’re talking volume rather than distance?

So doesn’t that make it the maximum size of the inflationary bubble, rather than the minimum?

Um, no. The maximum would include areas before inflation that were causally disconnected.

mollwollfumble said:

The Rev Dodgson said:

mollwollfumble said:

The factor of 10^26 comes from the scale factor during cosmic inflation. Objects causally disconnected before cosmic inflation will be about 10^26 times as far away as the present observational horizon.

Um, did I forget to cube that because we’re talking volume rather than distance?

So doesn’t that make it the maximum size of the inflationary bubble, rather than the minimum?

Um, no. The maximum would include areas before inflation that were causally disconnected.

Why would it? In what sense would they be part of the inflationary bubble?

What reason is their to think this is the minimum size?