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[Great Order]

The How Did You Last *Own* thread has been derailed (Predominantly by me) with talk of space, decompression, holding your breath, strangulation and so on, so to redirect the conversation...

Maybe everybody else holds their breath, and that's why they die so quickly.

Your characted exhales instead, and thanks to that they get that 0.5 minute of consciousness.

I mean, in reality I think you get about 10 seconds because that's how long it takes the deoxygenated (Because in vacuum your lungs start scrubbing gas out of your blood) blood to reach the brain, and the brain goes lights out almost immediately when that happens.

Actually it's between 45-90 seconds for most people, and that's just the "time of useful consciousness" i.e. the time before you start losing cognitive function. Unconsciousness takes a couple of minutes, and permanent brain damage begins at about 5 minutes without oxygen supply.

It depends on how and what you were breathing before getting decompressed but that's how long NASA estimates an astronaut to be able to operate in a completely depressurized environment. Assuming you don't slightly explode due to rapid decompression, that is.

Personally I find that doubtful, when someone's successfully strangling you you get about 10 seconds before you go floppy so 60-90 for useful consciousness and 120 for unconsciousness seems very optimistic to me.

Of course, you're gonna die regardless. Your lungs will be torn up simply by the pressure differential between your blood and the vacuum, you'll be at least temporarily blind from the decompression damage to your eyes, your mucous membranes are gonna burst, you'll have bruising everywhere, and if you're orbiting the sun there'll be enough unfiltered radiation to give you a nice sunburn in the brief stint outside.

Actually why do we want to go into space again? I forget.

There aren’t many people in space to strangle you.

Also, if all it took was 10 seconds of holding your breath for unconsciousness, swimming would be a particularly brutal sport.

That's the difference, when you hold your breath there's still oxygen in your lungs, it's just getting steadily replaced by carbon dioxide. There's a reason that mouth-to-mouth works to provide oxygen. In space because there's only vacuum, dissolved and loosely bound gas molecules will actually get yanked out of your lungs and into the void so you've got almost no oxygen in the blood any more.

[King Zultan]

In space no one can hear you scream, because the vacuum of space kills you before you can.

[Quarque]

From what I read, you'd pass out in space in about 10-15 seconds, but it takes surprisingly long (about 2-3 minutes) before you actually die. There are far more deadly things in space. Close to Jupiter, radiation is worse than Chernobyl during the accident; it kills you horribly within 10 seconds. Close to the sun, the heat burns you to death in like 1 second. Close to a magnetar, the magnetic field is so ridiculous that every atom in your body is shredded in a fraction of a second. If you'd be insane enough to jump into a black hole, every elemental particle down to quarks is converted into pure energy in an amount of time that becomes hard to calculate or understand because spacetime itself is basically shredded there too.

[Great Order]

From what I read, you'd pass out in space in about 10-15 seconds, but it takes surprisingly long (about 2-3 minutes) before you actually die. There are far more deadly things in space. Close to Jupiter, radiation is worse than Chernobyl during the accident; it kills you horribly within 10 seconds. Close to the sun, the heat burns you to death in like 1 second. Close to a magnetar, the magnetic field is so ridiculous that every atom in your body is shredded in a fraction of a second. If you'd be insane enough to jump into a black hole, every elemental particle down to quarks is converted into pure energy in an amount of time that becomes hard to calculate or understand because spacetime itself is basically shredded there too.

OK, so with black holes I have a question:

Does anything actually enter them? Surely at the event horizon, because of gravitational time dilation, time doesn't flow any more? So functionally if you fell into one and avoided being blasted by radiation, spaghettified, etc. etc. from your perspective the universe would speed up to a ludicrous amount then the black hole would explode as it finally evaporates, leaving you in a dead universe as all the stars will have, by this point, gone out?

Also for the sake of the conversation, lets assume you're in earth orbit.

[Il Palazzo]

The time dilation on approach to the event horizon is frame-dependent. If you're hovering in empty space far away from the hole and are looking in, you see the horizon and objects progressively more redshifted and frozen in time as they near the horizon. But the time dilation doesn't exist from the point of view of an infalling observer, who reaches the singularity in finite time (counted in minutes* of proper time from crossing the horizon).

ed: *sorry, that's more like seconds, apparently

[Great Order]

Except black holes don't last forever, so like I said surely from your perspective the universe just speeds up (and gets blue shifted into hyper-energetic radiation) before the black hole evaporates and explodes (Because they apparently do that when they evaporate)? And if they lasted forever, how does entering the horizon work? If time doesn't flow at the horizon, you'd never hit the singularity, but if from your perspective time flows normally and the black hole's around for eternity, then you'd enter it.

Or is that another one of those "this is where the theory breaks down" parts of reality?

[Il Palazzo]

The theory is solid in this part, just counter-intuitive. It doesn't matter for the infalling observer if the black hole lasts forever or not, because for that type of an observer the infall time is short. There is no simple symmetry of perspectives here - that a particular class of observers sees time infinitely slow down at the horizon doesn't mean the universe's time infinitely speeds up for the infalling observer. The infalling observer actually sees the universe redshift and slow down. The symmetry is there if you were to consider an observer hovering just above the event horizon - that one would indeed see the rest of the universe blueshift and speed up.