# Proton-electron mass ratio; changed? how much?

## Main Question or Discussion Point

On the subject of our 'finely turned universe', I have read that the proton-electron mass ratio can not deviate more than 1:1037. In other readings, the allowable deviation was stated as 1% ("If the neutron were very slightly less massive, then it could not decay without energy input. If its mass were lower by 1%, then isolated protons would decay instead of neutrons, and very few atoms heavier than lithium could form."

Scientists using a Effelsberg 100-m radio telescope have determined that the ratio has changed "by only one hundred thousandth of a percent or less over the past 7 billion years"; alternatively, the change is written as 10^-7.

My question is: Is the change in the ratio (one hundred thousandth of a percent, 10^-7) greater or less than 1:1037?

[1:1037 is 1:10 to the 37th power]

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On the subject of our 'finely turned universe', I have read that the proton-electron mass ratio can not deviate more than 1:1037.

[1:1037 is 1:10 to the 37th power]
I'm sorry, but that is simply not correct.

Has the maximum deviation of the protron-electron mass ratio been calculated? If so, what is it? Is it something less than 1%?

jtbell
Mentor
Where?

that the proton-electron mass ratio can not deviate more than 1:1037.
Do you mean 1037 (one thousand thirty-seven), or 1037 which is a really really really big number, or 10-37 which is a really really really small number?

(Tip: to write exponents correctly, highlight them with the mouse, then click the "x2" icon in the toolbar at the top of the message editor.)

My lack of physics/math background is showing.

The number would have to be small since the article I read was speaking on the subject of a finely tuned universe and how a slight deviation in the ratio would not support the creation of the universe as we know it.

This would seem to be the equation, 1:10-37.

Thanks, jtbell, for the tip.

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