One night a meteor impact occurred over the Pacific and a strange green glow sweeps across the entire globe, in that moment our body can no longer age in fact this phenomenon seems to only affect mammalian species. I am wondering would we instantly recognize that we don't age anymore? How long before someone notice it and what kind of evidence would be required to show this is happening?

P.S: there is no human casualties from the impact, thanks god but stupidity still kills!

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    $\begingroup$ Do our hair and fingernails still grow? Can we still learn new things? Do the bacteria in our guts still digest food? Asking because which signs will become visible first depends on which natural processes still occur, which do not, and what "magical" processes have begun to intervene. $\endgroup$
    – Tom
    Feb 2 at 3:31
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    $\begingroup$ Am I medically correct to define stopped aging as the cessation of shortening of telomere, like a buffer to protect DNA from harm during the process of replication? Thanks to Tom pointing out some of the signs which may indicate aging but I want to take it to another level... nanoscale ;D $\endgroup$
    – user6760
    Feb 2 at 6:40
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    $\begingroup$ Toms questions are correct. If bacteria stop aging, they probably stop being helpful, too $\endgroup$
    – Anderas
    Feb 2 at 6:49
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    $\begingroup$ @user6760 Suffice to say people are a little confused by what you consider aging versus maturing. You may want to clarify so as to get the best answers for your needs. As a biologist, I can tell you most people use the term "aging" pretty loosely. It's one of those things we have a hundred definitions for depending on context. $\endgroup$
    – DWKraus
    Feb 2 at 14:17
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    $\begingroup$ Do injuries heal too? Because some aspects of ageing are linked to healing. $\endgroup$
    – Graham
    Feb 2 at 16:52

The first to smell something fishy will probably be those who are caring a newborn who happened to be born shortly before the impact.

With no age progress the baby will not gain weight, will not stop looking like a wrinkled potato, will not get out of the 3 hours eat-sleep-poop cycle.

The pediatrics following these babies will notice that it's not just a single occurrence but a systematic event. From there observation will extend to children and adults.

For the first observations on babies to happen I think it will be a matter of one-two weeks.

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    $\begingroup$ Aging=/=growth. Although I understand it might be used for more or less the passage of time, by my knowledge aging is more or less defined by the adverse effects of growing old. A baby isn't growing old, it's maturing. Growing memory also isn't aging. For each aging can happen, but it is a different process. $\endgroup$
    – Trioxidane
    Feb 2 at 8:23
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    $\begingroup$ 1-2 weeks?! I'd expect 24hrs! The hospital in my city births 20 new-borns per day, several follow-up check happen in the first 24hrs and if they all came up with unexpected results the alarm would get raised much quicker. $\endgroup$
    – David258
    Feb 2 at 13:54
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    $\begingroup$ Or the same with lab mice: some scientist working with large numbers of mice is going to notice that they aren't aging properly pretty quickly. $\endgroup$ Feb 2 at 14:08
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    $\begingroup$ For that matter, does this apply to unborn fetuses? Do they just stay at whatever stage of development they were at when the incident occurred? Are all women who were pregnant at the time doomed to remain so forever? Or would they have to give birth to not-fully developed children? Would this prevent anyone from ever getting pregnant again in the future, since the zygote could never age up to full birth weight? This starts to sound like a horror story now... $\endgroup$ Feb 2 at 14:36
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    $\begingroup$ @Ash I am pretty certain the three hour cycle is biological. Newborn stomachs are the size of a cherry, and grow to walnut sized in a week or so. Three hours is about the time it takes for the baby to get a full stomach of milk moving along the digestive tract. $\endgroup$ Feb 3 at 5:27

Aging and death

I'll use ageing as the process of the damage we accumulate over time from normal growth.

When we don't age, it'll be difficult to see for most. Ageing is a slow and often unpredictable process. Our stamina decreasing, dementia or just our skin wrinkling are thing we would only notice over longer periods and not day to day. You can easily attribute ageing changes that are day to day to your daily routine or just to your mood, as you see things differently day to day. After you slept bad you might look into the mirror and see an old wrinkly thing staring back, while the next day you see a still young person still able to make a difference.

There are however times it is more noticeable. Especially at the latest (terminal) stages of ageing it can be easily visible from day to day. Think dementia, failing hearts or failing immune systems. Some might still die, as the heart failure can still occur over time without further ageing, but a lot of others will stay alive. This is the first indication we've stopped ageing. From one source on the internet about 100.000 people die from age related causes. With such a large population, we would find large deviations from people not ageing really quickly. Although the first day it might be seen as a curious thing to investigate, from day two we would put more effort into it. By day three we would probably know something weird is happening.

How quickly we would find out it's ageing that stopped is a difficult question. Maybe we notice in the cultures we make to see (ab)normal growth in cells that they don't age any more. The theories might come quick, but evidence will take a while for us to empirically prove it.

A rough estimate would be between a month and half a year for the scientific community to come to this conclusion more or less unanimously.

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    $\begingroup$ I expect the first people to notice will be scientists testing anti-aging drugs, who will all suddenly think they've found the holy grail when their telomeres stop shortening, and I expect news of the weirdness will spread out from there. $\endgroup$
    – Kaz
    Feb 3 at 9:37
  • $\begingroup$ @Kaz: There are two problems with that: 1) Real, working, clinically tested anti-aging products largely don't exist. It looks like some labs are at least trying to make them, but I don't know that we've reached the point where anything genuinely promising is being given to humans (yet). 2) They would see the same results in the placebo group, and quite possibly attribute it to "we don't know how aging works, more studies needed, etc." $\endgroup$
    – Kevin
    Feb 4 at 8:15
  • $\begingroup$ @kevin true. But I think a lot of them will see some really weird results. So you have about until the next relevant conference or maybe sooner before they start realising something really weird is going on. $\endgroup$
    – Kaz
    Feb 4 at 8:28
  • $\begingroup$ Yes. The anti-ageing drugs don't need to work, all that needs to work is the scientists' tests of telomere length while they try to get them to work, and I think they can do that. Each group will think something's gone wrong with their experiment when they see that neither group's telomeres have shortened the way they have in all their previous experiments, but it would only take one group to grumble about this to another and get the reply "Neither have ours!". $\endgroup$
    – A. B.
    Feb 5 at 8:36
  • $\begingroup$ P.S. @Kaz, you should make this an answer, that and your remark about laboratory shrews. $\endgroup$
    – A. B.
    Feb 5 at 8:43

So... when does life begin anyway?

So to answer your question we need to know when life begins. Given pro-choice vs anti-abortion debates this is not clear and resolved with any consensus. I'm giving 3 answers depending on when you decide life begins. Does it begin;

  • at sperm and egg?
  • at conception?
  • at birth?
  • at age 12 when telomeres start to shrink?

The answers for the last 2 are the same.

Fertility lab techs (next day), supermarket inventory managers (within a week), women trying to buy pregnancy tests (within a week).

In one extreme interpretation (ova and sperm are alive), all periods may stop (depending on how alive an ova in an ovary is considered), and all sperm are immature, so the first to notice will be Male fertility clinics, after every test returns failure for the same reason - underdeveloped, or missing, sperm.

Periods stop globally, and that's notable to each individual woman, but before that's correlated; inventory managers will notice that pads and tampons are no longer selling from supermarkets. These have a steady predictable rate of sale so it will be extremely suspicious when they're not moving.

Pregnancy tests will be sold out planet wide within a few days too.

Women who are 8.99 months pregnant, and retrenched maternity staff (within a week)

If life begins at conception, all embryos and fetuses will stop developing - because they're alive.

I'm greatly simplifying childbirth here, but if a baby is expected to be due in the next week, and it never finishes aging to the point that it's ready, I'd say it's very suspicious. Expectant mothers are going to held in suspense as their immortal fetus settles in for the long haul.

Birthing suites are expensive, there'll be scheduled c sections pre booked, and some will be induced chemically, but if they're still idle for a few days, or everyone is getting induced, that will raise some questions.

Or scientists working with surprisingly eternal shrews. (Within 6 weeks)

If due to magic the wave can differentiate between fetus and born, or you declare life begins at birth, then newborns will stop developing. This could take first time parents unfamiliar with what to expect a few months to realize, especially if behavior changes still occur from learning. (Repeat parents may get suspicious after a few weeks). I suspect parents taking infants a few months old to the doctor afraid their not gaining weight will be the first clue we have about it in humans.

If, as your recent comment implies, for the purpose of anti-aging ray life doesn't start until age 12, then adolescents will get stuck in early puberty. That sounds horrible, and may take a year to recognize or more, but there's a faster way if we go to non human mammals.

Your wave only affects mammals, and these mammals have a life span of about 6 months.

Any immortal affect is 100 times more noticeable on these than on humans. The scientists who are running tests on shrews and are waiting for some notable event in their development (puberty, death, litter, etc.) will be held in suspense until they start investigating.

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    $\begingroup$ Let me tell you a little secret - when a baby is overdue, the labor is induced artificially. There's no medical "litmus test" to tell when the baby is ready to come (apart from the labor itself). But, if suddenly 100% of pregnancies are induced (or scheduled c-section), that would look indeed very suspicious. $\endgroup$
    – Alexander
    Feb 2 at 5:57
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    $\begingroup$ Newborn double their size and weight in the first few weeks. It is VERY noticeable if that doesn't happen. Poor parents! $\endgroup$
    – Anderas
    Feb 2 at 6:57
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    $\begingroup$ @Anderas I'd expect repeat parents to know that and get suspicious, but after watching friends of mine become parents and have their minds scrambled by the process, a first time mother, sleep deprived and exhausted, I'd suspect will need it pointed out by a 3rd party. $\endgroup$
    – Ash
    Feb 2 at 7:13
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    $\begingroup$ "Expectant mothers are going to held in suspense as their immortal fetus settles in for the long haul." This is a great line. Feels like the start to a short story. $\endgroup$
    – ceejayoz
    Feb 2 at 12:31
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    $\begingroup$ I've rejected an edit as it is incorrect. "Anti-Abortion" is a more accurate description of the point of view and not the same as the misnomer "Pro-life". Examples are numerous: several US right wing politicians are pro death penalty but anti-abortion - there 5 countries who'll let a mother die rather than abort their child, the bombings of planed parenthood clinics, anti-abortion activists have killed at least 11 people in the usa. I can think of nothing disqualifying the term "pro-life" more than committing actual murder. $\endgroup$
    – Ash
    Feb 3 at 6:59

I assume that with “don’t age anymore” you mean that mammals would still grow up into full adulthood but don’t start (or continue) the long decline and decay into old age, right? So at some point (after all biologically old humans have died of various causes) all humans who aren’t still growing up would look like ~18 year olds.

In that case I think we’d first notice it in short-lived mammals like mice or rats which often have a lifespan of less than 3 years.

In general I think we’d notice a steady drop in age-related deaths.

Depending on the mechanism, maybe some biology lab looking at DNA and telomeres over time would notice that they suddenly don’t change anymore.

  • $\begingroup$ Would it be 18? It obviously depends on what exactly "aging" is anyway, but I was under the impression that people aren't really fully matured until about 25 or so. $\endgroup$
    – Kaz
    Feb 3 at 9:38
  • $\begingroup$ @Kaz: Yeah, I didn’t really know which number to use here. Sexual maturity is fully reached at 15–17 years and most people have also reached their full height at that point. After that, are there any changes which don’t fall under decline&decay (i.e. aging)? Some people already get wrinkles or baldness in their twenties. $\endgroup$
    – Michael
    Feb 3 at 9:55
  • $\begingroup$ I'm probably thinking of brain structure. I want to say there are parts of the brain that aren't fully built out until your mid-20s. Something about decision making, but that might be apocryphal. $\endgroup$
    – Kaz
    Feb 3 at 9:57
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    $\begingroup$ people with testosterone are going to look grizzlier and grizzlier over the decades, there are plenty of ways bodies change over time that aren't degeneration $\endgroup$
    – amara
    Feb 3 at 10:14
  • $\begingroup$ @amara: Yeah, I was thinking about that as well. Also other things: For example (afaik) baldness is caused by a byproduct of testosterone killing the hair follicles over time. Do we consider that aging? Is skin getting worse due to age (or cell duplication (defects)) exclusively or can it also happen through environmental damage (UV light etc.)? $\endgroup$
    – Michael
    Feb 3 at 11:20

I see a couple of answers here assume that "maturing" and "degenerating with age" are the same thing, or that both are affected. Biologically, the processes are very different. The biology of aging is still debated, but by at least some theories, "aging" is basically the opposite of "maturing". As a baby grows into an adult cells divide and multiply. When an old person starts falling apart, one theory is that cells are FAILING to divide and multiply to replace dead cells. The body can no longer replenish itself -- exactly why is another subject that I won't get into here, but look up "telomeres" for one theory -- and so dead cells cannot be replaced and the body starts to fail.

If we assume you mean that this phenomenon affects aging but not maturing, I'd say it would take months before anyone would notice, and longer for most people. I'm 62. I can tell that I'm getting little aches and pains and don't have the energy I used to have and so forth. But it's not like this happens on some strict schedule. I mean, it's not like someone could write in a book, "When you reach 60 years, 8 months, and 14 days, you will experience your first sign of arthritis." Some get it sooner and some later. Look at pictures of a bunch of people who are all, say, 60 years old. Some could easily pass for 40. Others you might think are 90.

If I stopped aging tomorrow, how would I know? I might notice that all these little aches and pains aren't getting any worse. But how fast do I expect them to get worse? I don't know. It would be literally years before I was sure that something odd was happening.

My guess is that the first people to notice would not be old people who realize they are not aging any more, but doctors or medical researchers who are studying human or animal patients every day with a microscope, and see that the progressive deterioration has stopped.

If, on the other hand, you are supposing that babies no longer mature, then people would notice very fast. Parents would likely notice within weeks that their child was not maturing properly. Babies in the womb would suddenly stop developing and there would be a massive number of miscarriages. After a couple of months, every baby would be a miscarriage. And doctors would start to notice that there was no longer any sign of new pregnancies.

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    $\begingroup$ I was thinking the same thing. Some of the other answers treat aging as running out a clock that has a set number of days on it... it's really more like becoming gradually more susceptible to environmental noise, until even everyday stresses like climbing stairs or using the toilet are enough to trigger the aneurysm/heart attack/stroke/etc that finally finishes you off. If people stopped getting older tomorrow, there'd still be a lot of infirm people (not only elderly!) who are just one bad day away from a fatal accident. And the question doesn't presume that people stop having bad days. $\endgroup$
    – trentcl
    Feb 2 at 21:45

It depends on what you mean by "aging"

If "aging" includes human growth and development, then L. Dutch's answer has you covered and I feel sorry for all new parents in that scenario. Having a permanent baby sounds awful. (or worse, permanent pregnancy)

However, if "aging" excludes the process of human development, i.e. babies grow into adults but remain in their prime forever (similar to elves in Tolkienesque lore), it may take decades to notice. Any differences in how people age will be subtle enough to be reasonably attributed to improvements to medicine. Athletes will still retire relatively young due to all the stress on their bodies and non-aging celebrities will merely seem to be the subject of camera magic. Arthritis will slowly taper off as treatments repair joints. Alzheimer's clinics will mysteriously have no new patients for 15 years. It will seem miraculous, but it likely won't cross anyone's mind that it was because aging stopped existing.

Things won't start seeming unusual until 15-20 years later. All the 40 year olds will look like plucky college grads. 50 year olds will have no signs of wrinkling. 60 year olds will have no sign of gray hair and men with a genetic predisposition for baldness will have universally dodged the bullet. With all the telltale signs of aging gone across the board, people will eventually conclude that the meteor was the cause.

... And now two new problems arise (assuming no aging implies living longer since "death by old age" is no longer a thing): overpopulation and pensions.

And then I noticed this:

seems to only affect mammalian species.

This probably decreases the time to detection. People's cats and dogs will live much longer and show no signs of slowing down. A dog will break the record by a landslide for the oldest dog ever. Veterinarians will see a slight decrease in business from the elimination of aging, but still see plenty of sick visits. News will report things like "cats seem to have become immortal", and "Dog God?" It will become more important than ever to neuter and spay your pets. People may not make the logical leap to human aging for a year or two, but given the evidence in dogs and cats, it will become apparent humans were affected before long.

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    $\begingroup$ I think we'd notice within the year. There are enough science experiments being done at any given time that will start showing absolutely unprecedented results that the scientific community will realise something very weird is going on inside of a couple of months. $\endgroup$
    – Kaz
    Feb 3 at 9:41
  • $\begingroup$ @Kaz that may be true, but it's going to take decades before the average Joe notices or believes it. And of course there will be all sorts of people who think it's a conspiracy. $\endgroup$
    – Beefster
    Feb 3 at 16:24
  • $\begingroup$ It wouldn't take long at all before we noticed that fewer and fewer people were dying of natural causes. Some would still already be dying of organ failure even if they weren't aging, but soon the normal pattern of people's health declining would cease to occur $\endgroup$
    – Kevin
    Feb 4 at 23:24
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    $\begingroup$ I'd expect scientists and people who believe in science would generally believe in it within a year or less, but it might take a decade or so for it to really filter to the "common people" so to speak. Great grandma sure is living a long time, Fido made it into his 20s, etc, etc. Enough of these accumulate across enough people, and we'd notice. And the pension issue could be easily solvable - give people a pension for a decade or two after a certain amount of years of work. Let them retool, relax, etc, and come back to the workforce refreshed. $\endgroup$ Feb 5 at 6:05

Unlike the assumption in some other answers, aging is not necessarily tied to growth and development.

There are a lot of natural examples of species unable to age (none of them, AFAIK, mammals).

There are quite a hints that growth and programmed aging are two antagonistic mechanisms making complex organisms somewhat stable. Growth and development without aging will probably lead to oncology, the reverse will not work in the first place.

As for when we will notice - we'll probably need months or even years until aging-related medical condition start to be displaced by cancer-related.

There are a lot of diverse and non-preprogrammed aging mechanisms, like cholesterol buildup, that will more or less survive the impact - they will probably keep the society ballanced at slightly different equilibrium.


Pediatricians will notice that some of their patients have grown no taller over several months. This will be especially noticeable among those who ought to be going through puberty but aren't showing those signs.


We wouldn't be able to ever tell we've stopped aging because aging is necessary to store new memories.

You'd have a world full of Alzheimer's patients unable to recall even one second of life post-meteor.

Even if a single person managed to have a single "aha!" moment they wouldn't be able to spread that information fast enough.

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    $\begingroup$ Depends on how we define aging or how OP’s miracle cure works. If it’s some kind of nanobots which take a “snapshot” of all mammals at time 0 and then automatically and immediately reset them to that snapshot every second then you are correct of course. $\endgroup$
    – Michael
    Feb 2 at 19:25
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    $\begingroup$ Huh? Most of us go through several decades of life - say from 20s to 50s - without noticable aging, yet are perfectly able to form new memories. $\endgroup$
    – jamesqf
    Feb 2 at 23:40
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    $\begingroup$ "We wouldn't be able to ever tell we've stopped aging because aging is necessary to store new memories." Citation needed. $\endgroup$
    – Beefster
    Feb 2 at 23:46
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    $\begingroup$ @jamesqf I don't know about you, but I definitely notice a difference at 35 than I was at 20. $\endgroup$
    – DKNguyen
    Feb 3 at 0:11

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