The radioactive half-life of an element is a measurement that determines how long it takes for half of the atoms in that element to disintegrate. Some elements have a half-life measured in seconds, minutes or days. Others have a half-life measured in thousands or billions of years. How exactly does anyone reliably determine such a figure?
I understand that measurements are generally exact, at least to our limited perception, and using standard equations should result in a particular value. Moreover, if you can see a decent progression happening over a particular window of time, then it should be reasonably simple to come up with a decent guess as to the half-life of an element. The one thing you will need is a constant – or at least an understood – rate of decay.
Even though this rate may seem constant to our measuring techniques, how can anyone think that the rate will remain constant over 4.5 billion years? Assuming that the rate of decay does remain constant, how do we know that some other factor – some outside influence that changes the conditions – won’t alter the rate of decay at some point in the future? While outside influences aren’t generally understood to affect such things, what happens if we find out that they do?
There are just over 2 trillion days in 4.5 billion years – that’s a lot of opportunity for change. Especially interesting because many of the elements that have such a large half life weren’t even known until recent years. Uranium, for instance, wasn’t discovered until 1789, and it wasn’t even isolated until 1841. That’s a lot of advancement – and change – in just 54 years. Why do we think that there won’t be even more in the next 4.5 billion?
Let’s assume that Uranium’s rate of decay had been examined since the day it was discovered. You’re only talking 200-plus years. How can a measurement taken over that small of a sample reliably reflect data for 4.5 billion years? The sample would only be five 10 millionths of the whole – and I feel very confident that the rate of decay hasn’t been measured since discovery!
Recently, the government’s effort to build a nuclear waste facility in the Nevada desert suffered another setback. Now I don’t have anything against the folks in Nevada, and I don’t necessarily think that this is a good idea. But the latest argument against this project is that the designers can only predict how well the facility will hold its contents for the next 10,000 years. The effect on someone living in near proximity to the facility indicates that they will be 60 times over the allowable limit of radiation – in 270,000 years.
I’m all for being environmentally responsible, and I am not necessarily recommending that the government move ahead on this project. What I don’t get is how anyone thinks that we can possibly predict reliably what things will be like 10,000 years from now – much less 270,000. What if the designers come back and say that they’ve altered their plans and that things are all set – and for 500,000 years, the radiation will be well below allowed levels?
What if they are wrong? Who in the world will be liable for the problems that crop up 13,000 years from now? Our country can’t even seem to get over slavery issues – and those ended just 150 years ago. Even if you blame the government, who in their right mind would think that any entity that exists today would be around in any form in that kind of window? Microsoft, sure. But who else? Even Larry Ellison ought to have given up by then.
Assuming that those issues can be handled, what if someone in 20 years – or 200 or 2000 or 20,000 – decides that the allowable raidiation level is a tenth of what they projected? Ooops. I don’t have a problem with science, even though this may come across as such. I’m all for it. However, I don’t see why we think we can predict things so far in the future. Even if the numbers are right, all sorts of things could change between now and then. Just look at the discoveries of the last few hundred years.
To think that the sum of our knowledge will simply stagnate for the next four-and-a-half billion years seems to me to be very narrow thinking – or very egotistical. Perhaps the effort should be expended on trying to make things decay more quickly, develop or discover methods for ridding ourselves of the mess we’ve already produced – or even come up with safer alternatives.