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# Astronomy/A Pure-Energy Universe?

Question
If all of the matter universe were converted into energy (or if it began as energy and never became matter), how much energy would that be? What could hypothetically be accomplished with a universe's worth of energy (assuming a civilization could contain and harness that much energy without being destroyed)?

Since the total mass of the Universe is only a fraction of the so-called "critical mass", converting all of it to energy would simply add to the existing Cosmic Background Radiation. It would have no significant effect on the expansion or future of the Universe, as it doesn't matter whether "being" is in the form of matter or energy -- either contributes to the "mass" equally, according to the formula E = m c-squared.

However, since you would like to know if that could be harnessed, I presume you don't actually want to presume everything is converted to energy -- just something close enough to your supposed civilization to take advantage of it. In that case, the energy from the conversion of even a single star into energy would be essentially unimaginable, and only the technology applied to harness and use it would impose any limits on what could be done.

As an example, even just the sunlight that falls on the Earth is many times larger than all the energy ever used by humans, and it is nothing compared to the energy that doesn't fall on the Earth and simply radiates into empty space -- and in the 10+ billion years of the Sun's lifetime, only about 0.7% of its mass is converted into energy, so you'd have to multiply all the lost energy by 10+ billion years times 140 (the reciprocal of 0.7%) to get the amount of energy available if we could just turn the Sun into energy. The result is a gargantuan amount, far greater than anything needed to accomplish wondrous things, or to destroy all life in the Solar System gazillions of times over.

Astronomy

Volunteer

#### Courtney Seligman

##### Expertise

I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.

##### Experience

I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Publications
Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

Education/Credentials
I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)