[Aeris (OP)]

The physical constants of our universe are a set of values for things such as the strength of the four fundamental forces, the mass of certain particles, the amount of dark energy in our universe and so, so much more. Just about all of the constant are at a value that allows for the formation of stars, galaxies and planets, which in turn allows for the emergence of organic, sentient life.

Here's what I want to know though. Assuming you had the ability to do so (this may or may not require some imagination from the people answering this question), how much could you alter the values of each of these constants before life as we currently know it becomes impossible? Additionally, how much could you alter the values of the constants before any form of hypothetical life becomes impossible as well?

I will admit that, in retrospective, this is an unfathomably pointless question in the grand scheme of things since A) Science rarely ever concerns itself with "What if?" and "What could have been." questions due to the simple notion that they deal with things that can't be tested, observed and supported, and B) Questions like this make a lot of blatant assumptions that most scientists would consider ridiculous (the ability to alter the values of the universe's constants) or presumptuous (the ability to say with absolute certainty that we know the exact value of each of the universe's constants, as well as what would happen if they were altered). I am genuinely curious to know the answer regardless though, so I hope you'll all be understanding enough to treat this question equally to that of other questions on the forum that don't deal with as much speculation.

List of physical constants and their values:
https://en.wikipedia.org/wiki/List_of_physical_constants

List of hypothetical types of biochemistry:
https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry

[Halc]

Assuming you had the ability to do so (this may or may not require some imagination from the people answering this question), how much could you alter the values of each of these constants before life as we currently know it becomes impossible?

Some have a very narrow range in which such emergence can occur, and others only need to be near their observed values to less precision to allow it. I could not find a quick reference, but one I think needed to be precise to like 20 digits or something, else such complex structures would not emerge.

Additionally, how much could you alter the values of the constants before any form of hypothetical life becomes impossible as well?

Who knows what alternate forms of life might be possible with totally different physics (like number of dimensions for instance)? It could well be that there is some completely alternate physics that is tuned for emergence of life, without even protons and such. I really don't think we're capable of imagining them all, so I don't think the question has a reasonable answer.

The usual question asked is, "How does our universe come to have these improbable tunings?", which of course begs a bunch of unstated premises, and cannot be answered without stating them explicitly.

[Aeris (OP)]

Some have a very narrow range in which such emergence can occur, and others only need to be near their observed values to less precision to allow it. I could not find a quick reference, but one I think needed to be precise to like 20 digits or something, else such complex structures would not emerge.

Ok. If you ever remember what those constants specifically were, please could you let me know?

The usual question asked is, "How does our universe come to have these improbable tunings?", which of course begs a bunch of unstated premises, and cannot be answered without stating them explicitly.

Honestly couldn't care less about such a question. If you wanna invoke an all powerful God/Creator, by all means, go nuts. I'm never gonna argue against the beliefs of such people. I on the other hand am perfectly fine with any of the other answers, be it an infinite cycle that doesn't stop until it eventually gets enough of the constants right to support a universe stable enough to hand around for more than a few seconds (if even that), complete luck of the draw or the incredibly reliable, albeit somewhat unsatisfying anthropic principle. 

[chiralSPO]

The anthropic principle may well be muddying the water here.

Life, as we know it, is only possible under extremely stringent conditions, and even then, we don't have any really good theories (let alone experimental evidence) of how life came about, so it would be very difficult to give a reasonable answer here. (the jury is still out on how common life, as we know it, actually is in this universe... it appears to have started very early on earth, suggesting it is relatively a likely outcome in planetary development of earth-like bodies... but we also don't have any solid evidence of extraterrestrial life... so maybe it is rare?)

The other thing here, is that I think we could probably be looking life, not as we know it, straight in the proverbial face, and not even know it. (microorganisms were not proven to exist until relatively recently, and it was only just a few years ago that it became known that lichens are a hybrid of bacteria/fungus/plant organisms. We were once shocked to discover hydrothermal vents at the bottom of the ocean to be teeming with life—now we suspect that to be potentially the origin of terrestrial life and possibly the most common ecosystem in the solar system, as there are similar geochemical processes for sure on Europa and Enceladus, and possibly on other icy geologically active worlds)

Given the extreme phenotypical diversity of life on earth it is easy to think that we understand what diversity is, but even so... all of our life is *very* similar from a chemical perspective, and the physics involved is even more limited (though there is some really cool physics involved in photosynthesis, bioluminescence, biological diffraction gratings etc.).

If we try to expand out definitions to include different even wider temporal and spatial scales, and what pressure/temperature/composition ranges are "conducive to life" I bet there is a lot of cool "life" to be found.

[alancalverd]

Depends on what you mean by "life".

Life As We Know It is a very fragile construct and continuously evolving in all sorts of directions so the term doesn't even have a fixed meaning from one day to the next. But if you chose one characteristic of living things you could probably replicate or simulate it if your universe incorporates something like a hydrogen bond.

[Aeris (OP)]

Depends on what you mean by "life".

Life As We Know It is a very fragile construct and continuously evolving in all sorts of directions so the term doesn't even have a fixed meaning from one day to the next. But if you chose one characteristic of living things you could probably replicate or simulate it if your universe incorporates something like a hydrogen bond.

I quite literally mean life as we as society have evolved and learnt about.

[Colin2B]

I quite literally mean life as we as society have evolved and learnt about.

That’s still quite a broad range from bacteria through plants to humans. There are changes humans would not survive, but bacteria would.
An interesting situation occurred on early earth, atmosphere rich in CO₂ and bacteria which thrived on it. Along comes bacteria which generates O₂, atmosphere changes and CO₂ bacteria die. So a change might favour a new direction for life rather than an extinction. Humans, however might not endure such changes

[alancalverd]

In that case, no chance. Society is the most improbable outcome of organic chemistry so far, and has only existed in a recognisable form for about 10,000 years - a blink.

[evan_au]

There have been several books that have tried to address this question, at least for the familiar water/protein/DNA/hydrocarbon style of life.

I read the one by Martin Rees (UK Astronomer Royal), summarized here:
https://en.wikipedia.org/wiki/Fine-tuned_universe#Examples