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Ags

The stars go out...

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As a kid you have an 8 inch dob, but by your middle age you only have a 5 inch mak. By your retirement all you are left with is a 3 inch tasco.

Well, swap millimeters for inches and that is what happens to your pupil size. The aperture loss with age for naked eye astronomy is dramatic. A partial biological explanation for aperture fever?

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The aperture loss with age for naked eye astronomy is dramatic.

But the odd thing is that - in terms of naked eye limiting magnitude - you hardly notice; certainly not 1.5 mags loss (half the aperture) by age 60. 0.5 mags I'd believe ... but even then I think it's at least as likely to be a brighter sky due to increased light pollution.

I do find I need brighter light to read comfortably than I used to, but I don't think there's been much change in my perception at the dim limits of vision.

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I also have not noticed the light loss so far... But the physics is inescapable. And I doubt that my retina is improving with age, so it is a mystery to me.

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When cells replicate, why do they replicate into an older form of the organism and not simply keep it young/as it was before?

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When cells replicate, why do they replicate into an older form of the organism and not simply keep it young/as it was before?

Organisms have evolved to propagate genes.

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When cells replicate, why do they replicate into an older form of the organism and not simply keep it young/as it was before?

A very deep question ... probably the best answer that exists at the moment is that, if they did, there would be nothing to stop cancers - cell aging and death starts almost as soon as embroyological development & seems to be essential to the process of normal development and life of all earthly multicellular organisms.

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A very deep question ... probably the best answer that exists at the moment is that, if they did, there would be nothing to stop cancers - cell aging and death starts almost as soon as embroyological development & seems to be essential to the process of normal development and life of all earthly multicellular organisms.

Of course, cells replicate and die - but what tells them to replicate and act in a different way to they were before? I'm sure i read something about this before, where 'scientists' (broad term that that is) were researching if it would be possible to stop/reverse this.

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what tells them to replicate and act in a different way to they were before?

Look up "Hox genes". Not the whole answer for sure; telomers (apparently unused bits of genetic information) probably also have a considerable influence, as these frequently get changed during replication, usually shortening progressively as the cell "ages".

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Telomeres are a 'hack' used by nature to get around the problem of replicating our DNA. Bacteria have DNA in rings and the replication system is designed to work with rings. Eukaryotes have DNA starnds, not rings, so the side effect of replicating strands is that a bit on the end of the strand is lost. The telomeres are padding on the ends of the strands that can be safely lost during replication.

Edited by Ags

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Yep. My current foray into astronomy was partly motivated by the thought that my pupils will be getting smaller. I have heard many people say that it makes less difference than you imagine. I expect the main reason is that as your pupils get smaller you dark adapt more. Even a dark sky is still bright (in the UK at least) so you are really limited by contrast. One of my favourite eyepieces is the 14mm which will only have a 3mm exit pupil!

Wandering into the realm of fantasy, I'm saving up for a eye packed with rods and a tapetum lucidum, see here.

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