Does the universe have zero total energy?

In summary, The conversation discusses Stephen Hawking's theory that the Universe was spontaneously created through a quantum mechanical process and how this is possible if the total energy of the Universe is zero. The questions asked are whether this theory has been studied rigorously and what role dark energy plays in the balancing of universal energy. The conversation also delves into the relationship between dark energy and inflation.
  • #1
DJsTeLF
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Just finished reading Hawking's 'The Grand Design' in which he appears to culminate in saying the Universe was spontaneously created by some sort of quantum mechanical process. He also comments that this is perfectly allowed if the total energy of the Universe is zero, suggesting that mass/energy is balanced with the negative energy associated with gravity.

My questions are therefore:
1/ Can this really be true? Has anyone attempted a more formal/rigorous study of it? (Well, the observable bits anyway.)
2/ What contribution does dark energy have to this Universal energy balancing act?

References / links to papers or articles grately appreciated

I also want to stress that this thread is in no way intended as an opportunity for religous discussion.
 
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  • #2
DJsTeLF said:
Just finished reading Hawking's 'The Grand Design' in which he appears to culminate in saying the Universe was spontaneously created by some sort of quantum mechanical process. He also comments that this is perfectly allowed if the total energy of the Universe is zero, suggesting that mass/energy is balanced with the negative energy associated with gravity.

My questions are therefore:
1/ Can this really be true? Has anyone attempted a more formal/rigorous study of it? (Well, the observable bits anyway.)
2/ What contribution does dark energy have to this Universal energy balancing act?

References / links to papers or articles grately appreciated

I also want to stress that this thread is in no way intended as an opportunity for religous discussion.
A well-known result from taking the Hamiltonian formalism of General Relativity is that the total energy (matter energy + gravitational potential energy) for a closed, homogeneous universe is identically equal to zero. If you want more detail, this is an authoritative paper on the subject:
http://www.springerlink.com/content/357757q4g88144p0/
 
  • #3
Thanks for your response Chalnoth. That paper was very interesting. I also found this article about the 'weight' (density actually) of the universe:
http://scienceblog.com/community/older/2000/D/200003072.html

One aspect is still troubling me a little though; Einstein's equations posit that mass/energy density exactly cancels the gravitational potential only for a zero cosmological constant. I'm under the impression that the current consensus in the scientific community is that the cosmological constant is small and positive. I.e. the dark energy driving the accelerating expansion of the universe that we observe. A few questions therefore arise:

Have I misunderstood this completely?
Is the effect of dark energy assumed to have changed since the point of last scattering?
If so, how could the universe have begun with zero total energy and now have an imbalance?

Finally I wonder if anyone has any insightful comments about the relationship between dark energy and inflation? Again, any references / links would be much appreciated.
 
  • #4
DJsTeLF said:
One aspect is still troubling me a little though; Einstein's equations posit that mass/energy density exactly cancels the gravitational potential only for a zero cosmological constant.
This isn't the case. The cosmological constant was left out because they didn't specify the matter distribution, and the cosmological constant can easily be included within the matter distribution.

DJsTeLF said:
Finally I wonder if anyone has any insightful comments about the relationship between dark energy and inflation? Again, any references / links would be much appreciated.
Well, they're obviously similar in that they both produce an accelerated expansion, but at wildly-different energy scales. There are a number of extremely speculative ideas as to the possibility that they may be the same field (these are usually called "quintessence" models). But so far there is no good reason to believe there is actually a connection.
 
  • #5


I can say that the concept of the universe having zero total energy is a topic of ongoing research and debate in the scientific community. While Hawking's theory in "The Grand Design" is one possible explanation, it is not the only one and there are certainly other theories and studies that have attempted to address this question.

To answer your first question, there have been attempts to study the total energy of the observable universe. However, it is important to note that the universe is a complex and ever-changing system, and it is difficult to accurately measure and calculate its total energy. Additionally, there are still many unknowns and mysteries in our understanding of the universe, so it is difficult to definitively say whether or not the total energy of the universe is zero.

Regarding your second question, dark energy is a topic of ongoing research and is not fully understood yet. Some theories suggest that dark energy could contribute to the balance of energy in the universe, while others suggest it may have no effect on the overall energy balance. Further research and studies are needed to fully understand the role of dark energy in the universe.

As for references or links to papers, there are many scientific articles and studies available on this topic, but it would be difficult to provide a comprehensive list here. I would suggest looking into scientific journals and publications such as Nature, Science, and Physical Review, as well as attending conferences and lectures on cosmology and astrophysics. Additionally, staying up to date on current research and theories in this field can also provide valuable insights into this topic.

In conclusion, the concept of the universe having zero total energy is a complex and ongoing topic of research and debate in the scientific community. While there are theories and studies that suggest this may be the case, it is still a topic that requires further investigation and understanding. As scientists, it is important to continue exploring and questioning these ideas in order to further our understanding of the universe.
 

1. What does it mean for the universe to have zero total energy?

When we say that the universe has zero total energy, we mean that the total amount of energy in the universe is balanced. This means that the positive energy from matter and radiation is cancelled out by the negative energy from gravity, resulting in a net energy of zero.

2. How do we know that the universe has zero total energy?

Scientists have observed the movements and interactions of celestial bodies, such as stars and galaxies, and have found that they follow the laws of thermodynamics. These laws state that the total energy of a closed system remains constant, and through various calculations and observations, scientists have determined that the universe has a net energy of zero.

3. Does this mean that there is no energy in the universe?

No, the zero total energy of the universe does not mean that there is no energy present. It simply means that the positive and negative energies are balanced, resulting in a net energy of zero. There is still energy in the form of matter, radiation, and other energy sources, but they all contribute to the overall balance of the universe's energy.

4. What implications does the universe having zero total energy have?

The fact that the universe has a net energy of zero has significant implications for the future of the universe. It suggests that the expansion of the universe will continue indefinitely, as there is no energy to slow it down. It also has implications for the concept of a "big crunch," where the universe would eventually collapse in on itself due to gravity.

5. Are there any theories that challenge the idea of the universe having zero total energy?

While the idea of the universe having zero total energy is widely accepted in the scientific community, there are some theories that challenge this concept. For example, some theories propose the existence of dark energy, which may have a positive energy and would therefore disrupt the balance of the universe's energy. However, these theories are still being studied and are not yet widely accepted.

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