Hydrogen fusion converts 0.007% of its mass into energy when the hydrogen atoms arr turned into helium. But if it was 0.006% or 0.008%.?

Question

It would be disastrous. I'm reading "A short history of nearly everything" and this is not explained in the book. It claims that if the fusion converted only 0.006% of the hydrogen's mass, we would have a world only of hydrogen, and if it converted 0.008%, there would be no hydrogen left. I think this 0.007% mass converted into energy is just a leftover from the fusion, but not necessary to make the fusion happen. Can someone elaborate? I'm new to this.

Answer 1

I can't elaborate because people make claims all the time. Usually the claims are false or at best misleading.

I have no idea of what arguments he uses but one possible approach would be to claim that if the sun had the same mass and the hydrogen produced less energy then the temperature of the sun would be different, it aging would be different .

And therefore at the time the planets were spun off from the sun there would have been a much greater fraction of hydrogen in the earth at that time.

However all of this is only speculation.

Answer 2

I've had this same thought about gravity. If our universe had gravity effect objects at a different ratio than what it currently is (even my a small percentage) nothing would exist. I think the author is trying to say the same kind of thing. We must remember that math (even simplified down to a single number) is just how we view it. So the author is just trying to say that if the amount of hydrogen's mass converted by fusion was just off by a little bit, everything we know would be different.

Answer 3

I strongly recommend you download and read "The Cosmic Landscape" by L. Susskind. He goes deeply into something called the constants of nature, of which there are just over twenty. The exact number depends on what is included and what is not in the list. There is no agreement there. But that there are more than twenty, that's the consensus.



We are all familiar with some of those constants: Planck's Constant, the universal gravity constant, the speed of light, pi, the electro static constant, and so on. And a large number that only a few who dabble in such things are aware of...like alpha that determines the rate at which photons are sloughed off electrons with changing momenta.



And here's the deal. Our unique universe with it's own laws of physics is defined precisely by the values of all those constants. You tweak just one constant by a small amount and you change the universe from what we have to something totally different with its own unique set of physics laws. Tweak one or more and our universe as we know it no longer exists.



Susskind claims there are 10^500 possible universes, each with its unique laws of physics, each defined uniquely by a different set of values for the constants of nature. For example, a universe the size of a grapefruit, a universe where time runs backward to our timeline, a universe totally devoid of planets and star, etc. etc. etc. 10^500 of them are possible, each one different from ours and unique.



That so many, an uncountable number really, unique universes are possible gives some credence to the multiple universe hypothesis. Or, more dramatically, we are not alone. The down side, maybe, is that none of those other universes is like ours.



The universal gravity constant, G = 6.67E-11, is a good example of what can happen when a value of a constant of nature is altered. Let's tweak and get G' = 1.01G a constant that's just 1% stronger.



This then changes κ = 8πG/c^4 to k' = 8πG'/c^4 = 8.08πG/c^4 where k is the proportionality constant in the general theory of relativity tensor G_{\mu\nu}' = k'T where G_{\mu\nu} is the Einstein geometric tensor and T is the energy.momentum tensor.



This is probably not meaningful to you, but what it shows is that the forces of gravity throughout the universe, as exemplified by G_{\mu\nu}', would be increased universally by that 1%.



[So space dust would clump more readily and tightly. Moderate stars would become super bright dwarfs, galaxies would be tighter and more readily swallowed by their black holes, etc. Our solar system would likely have no planets as they'd become the star in the middle.] Note, this is all WAG; one would need to do an in depth rigorous study to figure out what that 1% increase would do. But you get the idea...our universe as we know it now would not exist.