Exploring the Mass Energy of the Universe

In summary, the estimated mass-energy in the observable universe is around 10^70 joules, with stars making up 5% of the total mass. There are different ways to approach this calculation, including considering baryonic matter (4% of total energy density) or all forms of matter including dark matter (26% of total energy density). The total energy density is known to be around 0.85 nanojoules per cubic meter. Considering the estimated radius of the observable universe (46 billion light years) and the volume of a sphere with that radius, the estimated mass-energy comes to around 10^70 joules. However, this includes dark matter and not dark energy, so the estimate for ordinary baryonic
  • #1
chis
51
0
Do you guys how much mass energy is known to be in the Universe?
 
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  • #2
The size of the universe depends on your cosmology model.

The simplest and most accurate figure is for the 'observable universe'.
There are around 10^11 galaxies with 10^11 stars in each, a star has a mass of around 10^30kg. Stars make up about 5% of the mass of the universe according to galaxy dynamics measurements.

so 10^11 * 10^11 * 10^30kg * c^2 * 20 = 10^70 J
 
  • #3
Wey hey how many zeros is that... no in fact what is that! Yes I know nowt, thanks for your patience.
 
  • #4
Jeeze you guy are on it. So the universe has only filled up 5% with known matter?
 
  • #5
there is another way to approach this

mass-energy could be either baryonic matter, which is estimated to be 4% of total energy density

or you could be asking about all matter including dark matter, that comes to 26% of total.

(Maybe you don't want to include dark energy, which makes up the remaining 74%.)

The total energy density is known rather precisely to be around 0.85 nanojoules per cubic meter.

So if you want the mass-energy due to all forms of matter, you take 26% of that
which comes to about 0.22 nJ per cubic meter. (If you only want ordinary baryonic, make that 4%.)

Now you just need to know the radius of the observable universe---the most recent estimate of that, of which I'm aware, is 46 billion LY. And you need the volume of a sphere with that radius, but in cubic meters. So you can multiply by the 0.22 nanojoule figure.

Google calculator did the whole thing in one step. I put in
(4 pi/3)(46*10^9 lightyears)^3 *0.22 nJ/m^3
and it gave me back something like 8 x 10^70 joules. this is comparable to what MGB said!

Actually when I put that in the window and pressed return it came back with
((4 * pi) / 3) * ((46 * ((10^9) lightyears))^3) * (0.22 (nJ / (m^3))) = 7.59505577 × 10^70 joules

Nice thing is it takes care of converting units by itself so you don't have to worry about mixing lightyears and cubic meters.

Since that 7.6 jillion includes dark matter (but not dark energy) if you want to compare with MGB's estimate, which I think was for ordinary baryonic matter, you need to scale down by a factor of 7 or so. It comes to around 10^70 joules.
 
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Related to Exploring the Mass Energy of the Universe

1. What is the concept of mass energy in the universe?

The concept of mass energy in the universe is based on the famous equation E=mc², where E represents energy, m represents mass, and c represents the speed of light. This equation shows that mass and energy are interchangeable and can be converted into one another. It is a fundamental concept in physics and helps explain how the universe works.

2. How do scientists explore the mass energy of the universe?

There are several ways that scientists explore the mass energy of the universe. One way is through experiments conducted in particle accelerators, where particles are accelerated to high speeds and collide with each other, releasing large amounts of energy. Another way is through astronomical observations, such as studying the light and radiation emitted from stars and galaxies. Scientists also use mathematical models and theories to understand the behavior of mass and energy in the universe.

3. What is dark energy and how does it relate to mass energy in the universe?

Dark energy is a mysterious force that is believed to make up about 70% of the universe. It is thought to be responsible for the accelerating expansion of the universe. While it is called "dark," it is not actually visible or detectable, but its existence is inferred through its effects on the movement of galaxies. Dark energy is related to mass energy in the universe because it is a form of energy that contributes to the overall mass-energy density of the universe.

4. Can mass energy be created or destroyed?

According to the law of conservation of energy, mass energy cannot be created or destroyed. It can only be converted from one form to another. This means that the total amount of mass energy in the universe remains constant. However, scientists have observed that the mass-energy density of the universe is not constant and is changing over time, indicating that energy is being converted from one form to another.

5. How does the study of mass energy in the universe contribute to our understanding of the universe?

The study of mass energy in the universe is crucial in helping us understand the fundamental laws and principles that govern the behavior of the universe. It allows us to explain and predict phenomena such as the movement of celestial bodies, the formation of galaxies, and the evolution of the universe. By exploring the mass energy of the universe, we can gain a deeper understanding of the origins and nature of our universe.

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