How many atoms are in the observable universe?

[Admin]

Atoms are the building blocks of all matter in the universe, but how many are there in the part of it we can see from Earth?

How many atoms are in the observable universe? : Read more

 

[rod]

"This gives us 10^82 atoms in the observable universe."

The answer according to the article. How the problem is solved presented too, very good here. The Universe is said to be some 46 x 10^9 light-years radius. Using the volume of a sphere, this is 4.08 x 10^32 cubic light years. What is the mean number of atoms per cubic light year in the Universe now?

 

[Jan Steinman]

All matter in the universe — no matter how big, small, young or old — is made up of atoms.

Wow, you lost me on the first sentence!

What about dark matter? We don't really know what it is made of, right?

What about neutron stars and black holes? They no longer consist of "atoms," as they've been crushed by gravity into something that is decidedly non-atom-like. Since every galaxy is thought to be centred upon a black hole that is as massive as billions of stars, they would seem to take up a significant portion of the total, no?

Perhaps the article goes on to explain that assumption, but I find it difficult to read an article that starts out with such an easily disproven statement!

 

[Atlan0001]

Don't miss or mistake the key reference in the article! "The observable universe"( the observed, therefore relative, universe in the light... the light physics connected universe hologram)! As opposed to the unobserved -- the unobservable -- simultaneous or future universe (simultaneous, and 'relativity' speaking, 'future' universes?).

 

[rod]

Atlan0101 brings up a good point in post #4. The actual observable universe using BB model is presently limited to about 13 billion light years or so because of Special Relativity and light travel time. The 46 billion light year figure used in the article comes from extrapolating the distance to the CMBR where redshift about 1100 is used today. We do not see galaxies or objects out there at such a distance but much smaller redshift values like z=11 or so. The volume of spherical space then shrinks to about 9.2 x 10^30 cubic light years using radius 13 billion light years.

 

[Helio]

I think their result is a reasonably close number. But I doubt the average mass for a star is as high as the amount used. But there are likely a little more no. of galaxies since recent studies show about 2 trillion. But, the more distant number are smaller in star members due to their immaturity.

It’s at least amusing that we are close to Avogadro’s no. (galaxy no.)

 

[Jan Steinman]

Don't miss or mistake the key reference in the article! "The observable universe"

Okay, I'll grudgingly give you a pass on that.

But certainly, we can observe neutron stars and black holes by their immediate effect on their surroundings, so I'd argue that they are "observable."