stupid physics questions

[KlaxonCow]

The evidence that the universe is the inside of a black hole mounts.



Still not definitive, of course, but the more you look into it, the more it weirdly makes more and more sense.

We've already known that the universe has the right density to be a black hole. This new evidence seems to indicate that the universe, in the overall, has some angular momentum to it. It's spinning.

And seeing as my previous "mad sci-fi ideas" are coming scientifically true, let's complete the thought experiment. There's the idea that, inside a black hole, time and space swap places and what you're being gravitationally drawn to is not a point in space, it's a point in time. The singularity is inevitable. You can no more escape it than you can escape tomorrow.

But here's the mad thought. What if "You can no more escape it than you can escape tomorrow" is not an analogy, but an equation?

Why does time inextricably tick forward at 1 second per second? Why does time have a direction?

If we're inside a black hole, then the answer could be that the singularity is a point in the future and we're "falling" towards it. The whole entire universe is "falling" into the future. We're being pulled, gravitationally, towards the future.

Yes, that's completely mad. But that's Einsteinian relativity for you. And this mad thought might answer another question - why is the force of gravity so much weaker than the other fundamental forces of the universe? But the "falling through time" idea could answer that by saying that it's not actually weaker, it's just that most of it is happening on the time axis.

That, on that time axis, we've got the entire universe - space-wise - and it's falling down a well, that's got near vertical sides. You can't go backwards in time, because to climb out of the black hole, you'd have to travel faster than the speed of light (except, of course, we're talking about the time dimension of spacetime, not the spatial dimensions).

This is completely insane, of course. But then so was the idea of the universe being the inside of a black hole, and the more they look, the more people are thinking that might actually make sense.

So, there you have it. The universe is a black hole, and everything inside it is "falling" into the future.

[SuperMappy]

Here's a stupid physics question:

I was looking up the name of a Bugs Bunny cartoon called Baseball Bugs. The Wikipedia page mentions that it includes an example of "cartoon physics" — Bugs throws a pitch from the mound to home plate, then runs fast enough to catch the same ball at home plate. It says this is impossible in real life. Why exactly would that be impossible? Would it just require Bugs to be extremely fast, or is there more physics to it?

[zip accident]

Here's a stupid physics question:

I was looking up the name of a Bugs Bunny cartoon called Baseball Bugs. The Wikipedia page mentions that it includes an example of "cartoon physics" — Bugs throws a pitch from the mound to home plate, then runs fast enough to catch the same ball at home plate. It says this is impossible in real life. Why exactly would that be impossible? Would it just require Bugs to be extremely fast, or is there more physics to it?

it depends on the throw, you can certainly throw a ball and catch it, but it has to go slow and high, which is not a typical baseball pitch as I understand things. The fastest animal is famously the Cheetah, at about 70 mph, which is about twice as fast as a rabbit. I think the speed of a ball that's been thrown hard is about 100 mph (+?). so the Cheetah couldn't catch it. There being an animal that could catch it isn't theoretically impossible I would guess, but we don't know of one. There may be a type of bird that flies that fast, but I think it's too small to lift the ball.

[KlaxonCow]

I don't know that it's provably completely impossible, but it's not so much speed as it is acceleration / deceleration.

So Bugs throws the ball and lets go. Then he has to rapidly accelerate up much faster than the thrown ball for half the distance, then rapidly decelerate on the other end to be in position to bat the ball away.

Such acceleration / deceleration to those sort of speeds over such a short distance would probably pull so many Gs that there's no living thing that could actually survive it. All your internal organs getting crushed up against your rib cage - twice. Like being in a 1000mph car crash two times in a row.

That's the physics for you. Speed itself is not a problem - right now, sitting on planet Earth, you're rotating at 800-1000 mph (depending on latitude) and you don't even notice it. Or, on a plane, you're moving just shy of the speed of sound and, again, no problem.

No, as the joke has it, it's not falling off a skyscraper that kills you. It's that instant deceleration when you hit the ground that kills you. If you could freefall forever, then you'd be just fine, however fast it is.

It ain't the speed, it's always the acceleration / deceleration.

(Indeed, moving at a constant speed, you're in an inertial reference frame and, in that sense, there is no such thing as speed. It's all relative, innit?)

[F-ZeroOne]

I think the speed of a ball that's been thrown hard is about 100 mph (+?). so the Cheetah couldn't catch it. There being an animal that could catch it isn't theoretically impossible I would guess, but we don't know of one. There may be a type of bird that flies that fast, but I think it's too small to lift the ball.

A peregrine falcon would likely exceed that speed - the usual maximum figure given is 186mph - but thats in a dive from height. As they regularly prey on pigeons, a baseball probably wouldn't be much of an issue for it, though how usable it would be afterwards is debatable.

[KlaxonCow]

So we have a big asteroid that, though it's been confirmed it won't hit the Earth, might possibly hit the Moon instead.



This is not good, as it might throw up a massive cloud of debris around the Moon and Earth.

But what are our options for dealing with this?

Well, deflection is considered impractical because you have to do that early - for the asteroid to diverge on its path enough to miss the Moon - and there's the big problem of, if you deflect it wrong, then you could send it straight at planet Earth instead.

Therefore, the second option is to blow it up with a nuke.

But, right now, NASA gave up its space launch capabilities to private companies like SpaceX - who can't reliably get their spaceship into orbit yet - so will we have to rely on Russia or China to launch it? Russia's in the middle of a war with Ukraine right now, and is an international pariah, so that doesn't bode well. While America's being ran into the ground by Trump, who's a fucking anti-science moron.

And maybe it'll actually block out the Sun a little to reduce climate change - which might sound like a good thing initially, until it's used as an excuse to "drill, baby, drill" to the end of oil, making shit vastly worse, once it's all eventually cleared.

We might have to get used to having a cloud of debris in orbit and a lot more "shooting stars" at night.

[venusian]

This is how the world will end: not with a bang or a whimper but with an over-excited science tiktokker doing jolly CGI videos of doom.

[Little stoned kiwi]

Is it wrong that I'm ambivalent to a potential world/life/human ending event?

[Harlequin]

Is it wrong that I'm ambivalent to a potential world/life/human ending event?

This is a rather lovely planet and I would rather like it to continue existing with some forms of life on it. It might also be quite nice for humans to leave behind some current cultural and scientific artifacts and knowledge (preferably in forms that do not require complex transient technologies to access) for other sapient species that may later evolve or visit.

[F-ZeroOne]

Not sure how big this asteroid is, but the oft-suggested solution of "NUKE IT!" is likely not going to be as simple as people usually assume it is. For one thing, nuclear weapons may be incredibly destructive, but they're not anti-matter weapons. Some nuclear warheads are designed not to strike a solid object but instead to detonate above it (an "airburst", such as the ones that were used against Hiroshima and Nagasaki, though some modern warheads are designed to strike the ground).

And even getting the nuke there in the first place is a challenge - most nuclear launch vehicles are ballistic missiles, which means they go up and then down again. Though its true throughout the history of spaceflight some of these systems were successfully adapted into space launch vehicles. But even if you get the thing into space, there haven't been very many actual contacts physical between Earth-launched vehicles and asteroids (I can only think of two off the top of my head). And of course, all space launch systems are subject to malfunction, some of them quite spectacular (though despite what pop culture will tell you, nuclear weapons generally will not go off at the drop of, er, a bomb; they usually have to meet very specific detonation conditions. What you may wind up doing is spreading radioactive material over a wide area, as has happened in Greenland once. And there has been at least one very near miss where - depending on source - an accidentally dropped nuclear weapon nearly did go off... ).

And finally, we don't know as much about asteroid composition as we probably should before setting off a nuclear explosion next to, or on, one. We might end up creating a shotgun-like blast of lots of smaller bodies instead (hey, Atari was right!)...

[KlaxonCow]

Apparently, Brian Cox was asked to speak at COP, where they were discussing action on climate change, and he basically made this astronomical argument that we might be the only intelligent civilisation in the entire galaxy.

Because it effectively took 4 billion years - a third the age of the universe - for intelligent life to form on this planet, and that also requires a planet that's sitting in a relatively safe zone - not straying too close to supernovae, having a single large moon that stabilises various cycles, is often protected from asteroids by the gravity of Jupiter further out, etc. - for all that time, which might be an extreme rarity.

And, heck, we don't know. Maybe 4 billion years is actually on the early side. Maybe this stuff usually takes 8 billion years on the average, but Earth's evolution hit some useful milestones that speeded it up (indeed, mammals only really came into their own, once the dinosaurs were wiped out - and that was a random strike, so would this planet still be dominated by dinosaurs to this day, if KT had missed. They'd been around for hundreds of millions of years, so what's another 66 million in the face of that?).

He laid it all out and - looking those world leaders in the eye - then pointed out that, without climate action and international cooperation against asteroid threats and the like, you could be condemning this planet and its unique residents to a coming extinction that wipes out the very concept of "meaning" for several galaxies all around us, if not an even wider chunk of space, if we're even rarer than we suspect ourselves of being.

I'm with Brian. Fatalism is stupid. Not least because our demise is inevitably guaranteed at some point anyway. You have no idea if, ten years from now, we perfect nuclear fusion and, on the back of abundant free energy, are able to feed and clothe everyone and give them a life worth living, as we move into some Star Trek Utopia of the future.

It could all just work out for the better. This is not unprecedented, as we humans have essentially been doing that all along - I often feel people really have no idea just how fucking horrid and harsh the past was, and just how much like the "God Kings" of old we already exceed, even amongst our poorest members.

The world is too interesting a place, with so much unknown and unanswered. A trillion souls yet to live. An unending horizon to explore. Worlds upon worlds upon worlds. Billions upon billions of childhoods, taking their first steps, their first words, their first loves, and all their achievements. All that love, all that friendship, all that meaning. All that heartbreak, all that art from tortured souls. The whole fucking kit and caboodle. How can you just let forever be?

Don't let go. Never give up. It's such a wonderful life.

[zip accident]

So we have a big asteroid that, though it's been confirmed it won't hit the Earth, might possibly hit the Moon instead.



This is not good, as it might throw up a massive cloud of debris around the Moon and Earth.

But what are our options for dealing with this?

Well, deflection is considered impractical because you have to do that early - for the asteroid to diverge on its path enough to miss the Moon - and there's the big problem of, if you deflect it wrong, then you could send it straight at planet Earth instead.

Therefore, the second option is to blow it up with a nuke.

But, right now, NASA gave up its space launch capabilities to private companies like SpaceX - who can't reliably get their spaceship into orbit yet - so will we have to rely on Russia or China to launch it? Russia's in the middle of a war with Ukraine right now, and is an international pariah, so that doesn't bode well. While America's being ran into the ground by Trump, who's a fucking anti-science moron.

And maybe it'll actually block out the Sun a little to reduce climate change - which might sound like a good thing initially, until it's used as an excuse to "drill, baby, drill" to the end of oil, making shit vastly worse, once it's all eventually cleared.

We might have to get used to having a cloud of debris in orbit and a lot more "shooting stars" at night.

This is a long time in the future. She's talking about it missing everything twice, then coming back a third time and maybe hitting the Moon. The odds are it won't fly that straight. It's not a dinosaur killer. The Moon has been hit before, look at it, it's got craters all over. There will be a lot of fun science if it does hit.

I'm not sure about the debris cloud, that might be a problem, it might not, and it will last hundreds of years at the most, maybe as short as one or two years?

[KlaxonCow]

Reaction from a nuclear physicist, who seems quite chill that it's not that big of a problem. But, if it is, then he approves the plan to nuke it.