this post was submitted on 02 Dec 2024
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Science Memes

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[–] RizzRustbolt@lemmy.world 7 points 1 day ago

How to solve the Three Body Problem.

[–] DaddleDew@lemmy.world 134 points 2 days ago (4 children)

This reminds me of that quote from Mass Effect:

"This, recruits, is a 20-kilo ferrous slug. Feel the weight! Every five seconds, the main gun of an Everest-class Dreadnought accelerates one to 1.3 percent of light speed. It impacts with the force of a 38-kiloton bomb. That is three times the yield of the city buster dropped on Hiroshima back on Earth. That means: Sir Isaac Newton is the deadliest son-of-a-bitch in space! (...) I dare to assume you ignorant jackasses know that space is empty! Once you fire this hunk of metal, it keeps going 'till it hits something! That can be a ship, or the planet behind that ship. It might go off into deep space and hit somebody else in ten thousand years. If you pull the trigger on this, you are ruining someone's day, somewhere and sometime!"

[–] TwoBeeSan@lemmy.world 38 points 1 day ago* (last edited 1 day ago) (1 children)

That first mass effect can't be beat for setting the stage and immersing you in the world.

I can hear the VA in my head lmao

Edit: I like mass effect I don't have a good memory

[–] hikaru755@lemmy.world 23 points 1 day ago* (last edited 1 day ago) (2 children)

That quote is not from the first one though, it's from the second one

[–] TwoBeeSan@lemmy.world 15 points 1 day ago

Balls exposed 🙀🙀🙀🙀

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[–] Seleni@lemmy.world 2 points 1 day ago* (last edited 1 day ago)
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[–] Zwiebel@feddit.org 102 points 2 days ago (5 children)

There is one detail wrong in the first post; that is not the lids speed but rather it's minimum speed.

[–] Reddfugee42@lemmy.world 70 points 2 days ago (1 children)

Notice, children, how the common apostrophe from lid's migrated all the way to its.

Isn't nature amazing?

[–] emmanuel_car@fedia.io 15 points 2 days ago

What makes it more amazing is I understood without even noticing the mistake.

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[–] RememberTheApollo_@lemmy.world 21 points 1 day ago (2 children)

Ive seen this claim a dozen times. It’s a disc shape. How this thing isn’t going to start flipping and curving its trajectory, or just plain old running out of energy due to air resistance, and not making it out of earth’s atmosphere is beyond me.

[–] gens@programming.dev 5 points 1 day ago (2 children)

Take a coin and trow it as hard as you can. The curving is not that much.

[–] merc@sh.itjust.works 1 points 21 hours ago (1 children)

Throw it into water or gelatin. At thousands of metres per second the air is going to seem much more dense.

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If it’s like a frisbee, yeah, but it still curves. Now start it spinning like spinning a coin on edge. The curving will be much more dramatic.

[–] finitebanjo@lemmy.world 12 points 1 day ago (1 children)

It didn't stay solid upon initial blast impact. Probably didn't even stay liquid.

[–] Crashumbc@lemmy.world 7 points 1 day ago (18 children)

Yeah it vanished because it vaporized.

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[–] sp3tr4l@lemmy.zip 35 points 1 day ago (3 children)

Responding to the last comment in the image:

You could literally just do reverse Starship Troopers, the movie at least.

You're a bunch of aliens and blam out of no where the nuclear launched manhole obliterates a holy site on your homeworld, your scientists track the trajectory back to Earth, conclude they must have launched it intentionally, and then launch an interstellar jihad against totally unaware Earthlings.

[–] dragonfucker 22 points 1 day ago (1 children)

That reminds drag of Halo, though significantly more silly.

In Halo, the Covenant are on an interstellar crusade for holy artifacts left behind by the Forerunners. When they discovered the planet Harvest, inhabited by humans, they saw tons of artifacts on their scanners. So naturally, they landed on the planet and started blasting the humans to steal the artifacts. But the more humans they killed, the more artifacts disappeared from their monitors. The humans must be destroying the artifacts out of petty spite! What heresy!

The Prophet of Truth is curious about what kind of artifacts the humans have, so he goes to talk to an ancient Forerunner AI they have in storage, Mendicant Bias. Truth shows Bias the symbol that they keep seeing on human worlds. Bias says "You fool, you've got it upside down. Turn it around, see? It says Reclaimer. It means a person the Forerunners have chosen to inherit their empire. You've just been killing these humans? No wonder the reclaimers keep disappearing, you're the one who's doing it!"

So Truth realises that he's been ordering his troops to kill what should rightfully be considered demigods by his religion, and who he should be worshipping. And he realises that if he reveals this information to the people, he and the other Prophets will lose all their political power since there are Actual Fucking Gods walking around. So naturally, Truth declares a Holy Genocide against humanity so that nobody will ever figure out that he's guilty of Deicide and that their entire religious political structure is a lie.

[–] victorz@lemmy.world 4 points 1 day ago (4 children)

You refer to yourself as "drag" in the third person, rather than just say "me"?

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[–] Earflap@reddthat.com 5 points 1 day ago* (last edited 1 day ago)

Most likely it just evaporated, or disintegrated or something, but I think its pretty unlikely it survived that absolutely bonkers acceleration.

[–] atocci@lemmy.world 44 points 2 days ago (4 children)

Sadly, the cover likely did burn up in the atmosphere at those speeds, like a meteorite in reverse.

[–] ilinamorato@lemmy.world 43 points 1 day ago (2 children)

I'm not so sure.

Let's compare with the Apollo Command Module heat shield, a remarkably close analogue for the bore cap. They're a similar weight (3,000 lb for the heat shield, 2,000 lb for the bore cap) and have melting points within an order of magnitude of each other (5,000°F for the AVCOAT heat shield and about 2,800°F for the iron bore cap). They're even both of a similar shape and aerodynamic profile (disc-shaped and blunt). Both had to travel 62 miles (the distance from sea level to the Karman Line, where atmosphere becomes negligible).

The Apollo CM made that distance in about seven minutes; at 130,000mph, the Pascal B bore cap took at most 1.72 seconds to make the trip.

What was discovered during the development of the Apollo heat shield is that the blunt shape caused a layer of air to build up in front of the spacecraft, which reduced the amount of heating that convected into the heat shield directly. This reduced the amount of heat load that the heat shield needed to bear up under.

Further, it's also worth noting that the Apollo command modules weren't tumbling, which the bore cap likely would have been, allowing brief instants during its ascent for the metal to cool before being subjected again to the heat of the ascent.

But probably most critical at all is the remarkably brief amount of time that the bore cap spent in atmosphere. This person did the math on how much power it would take to vaporize a cubic meter of iron, and the answer is 25,895,319 kJ. Now, the bore cap isn't quite a cubic meter, but we can use all of his calculations and just swap in 907kg (2000lbs):

  • To heat the bore cap to iron's melting point: 0.46 kJ/kg * 907 kg * (1808K-298K) = 630,002 kJ

  • To phase change the iron from solid to liquid: 69.1 KJ/kg * 907 kg = 62,674 kJ

  • To heat the bore cap to iron's boiling point: 0.82 kJ/kg * 907 kg * (3023K-1808K) = 903,644 kJ

  • To phase change the iron from liquid to gas: 1520 kJ/kg * 907 kg = 1,378,649 kJ

So, in total, 2,974,969 kJ. The Apollo heat shield encountered a peak of 11,000 kJ/m^2/s. Since the Pascal B bore cap was about a meter in diameter and was traveling through the atmosphere for about two seconds, we can very neatly estimate that it absorbed a maximum of 22,000 kJ due to atmospheric compression--not even close to enough to get it to melting temperature.

Interestingly, early missiles actually did use solid metal heat shields; not iron, but titanium, beryllium, and copper. They were effective, but abandoned due to their weight.

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[–] very_well_lost@lemmy.world 20 points 2 days ago* (last edited 2 days ago) (2 children)

I'm not so sure... At those speeds, it would've taken under 10 seconds to completely clear the atmosphere. Even with intense compressional heating, I don't think it would've been in contact with the atmosphere long enough to completely vaporize — although it probably didn't look much like a manhole cover anymore by the time it escaped.

[–] troyunrau@lemmy.ca 35 points 2 days ago (3 children)

I don't think melting is the issue here. I think it literally disintegrates at those speeds. Like, this is Mass Effect mass driver level of impact with the atmosphere.

For reference, RICK ROBINSON'S FIRST LAW OF SPACE COMBAT: "An object impacting at 3 km/sec delivers kinetic energy equal to its mass in TNT."

Assuming the lid is travelling 55km/s, it's well beyond that point. The atmosphere it's travelling through is basically a solid at that speed. Even if it isn't heating due to the friction (and waiting for heat flow), it is heating due to the compressive force of being slammed into the atmosphere. It's very likely the whole thing vaporized.

But I could be wrong, and some alien SOB is going to have a bad day when the manhole cover slams into their ship in interstellar space.

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[–] mkwt@lemmy.world 15 points 2 days ago (1 children)

And for reference, the earth escape velocity from the surface is 11.2 km/s or 25,000 mph, not 7,000 mph.

To escape the solar system from the earth surface, the minimum speed is 16.6 km/s, or 37,100 mph. But this assumes that you launch in the correct direction to take the most advantage of the Earth's 30 km/s. If you launch in the most disadvantageous direction, you can add another 60 km/s to escape.

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[–] chuckleslord@lemmy.world 18 points 1 day ago (1 children)
[–] usualsuspect191@lemmy.ca 18 points 1 day ago

I disagree. He did the math assuming all the energy would be dissipated but that's assuming it came to a stop which is the whole debate. Essentially a mathy begging the question.

The jet of hot gasses coming up around and with the cover could've provided a good bit of protection from friction for the first bit (where the atmosphere would have the greatest effect) and ablative effects and the short travel time though the atmosphere could've been enough for a likely slightly smaller and very hot cover to blast into space.

[–] MajorHavoc@programming.dev 19 points 1 day ago

I love the idea that our first message to aliens might be "FRESH WATER ONLY. NO WASTE."

[–] ICastFist@programming.dev 14 points 1 day ago (2 children)

We should test this again, but with a fridge and someone inside it for the nuclear blast. I bet that would work out great

[–] SwordInStone@lemmy.world 5 points 1 day ago* (last edited 1 day ago)

future president of the us perchance?

[–] Hossenfeffer@feddit.uk 4 points 1 day ago (1 children)

Where are we going to get the archaeologist?

[–] ICastFist@programming.dev 1 points 1 day ago

Say there's a college grant inside, easy peasy

[–] user1234@lemmynsfw.com 8 points 1 day ago

The foundry that made that manhole cover has some great potential advertising claims.

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