What's the most stupid thing you've been told?

LeftyJason

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  • Mar 8, 2017
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    No. If you watch the video closely, it looks like he shot it through the eyes. But, I bet this wouldn't have to contact your body to kill you:
    Supersonic object - pressure wave
    There is a very very big difference between that and a bullet namely the mass of the air in front for the size of the object creating the shockwave.

    There is a big difference between a pea going supersonic vs a building going supersonic. Bullets are tiny.

    For example a 0.5" diameter circle has an area of 0.196 square inches. A 10' dia circle has an area of 11,309 square inches. An object going supersonic has to force all of that air out of the way around the sides.

    Doing a little quick research. Check this out.

    According to that most people are killed at a 10 psi overpressure (294mph wind) and fatalities approach 100% at 20 psi (502 mph wind) . Putting that in terms of a nuke according to a book that I have (that was checkout able in my high school). A 200kt nuke will put out a 20psi overpressure out to a mile, 10 psi out to 1.4 miles.

    The book.
    20210219_013630.jpg

    Most damage that I think I've ever heard from supersonic aircraft is glass is cracked or shattered. That is a 1psi overpressure (38 mph wind). Same nuke as above will do that at 5.9 miles away.
    20210219_013522.jpg

    Taking all of this info and doing a gut scaling common sense check along with the experimental testing with the 50 bmg like in the video posted in post 1530 shows why this is so stupid.

    Edit: and no I'm not an engineer. I have common sense.
     
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    slowworm

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    Common sense is far from common. If a 50 cal passing close by can damage you, why aren’t people close to the weapon injured when firing it. Why isn’t a muzzle safe radius drilled into gunners so that don’t injure their brothers in arms. For something so “well known” the armed forces certainly seemed to have missed regulations and training for it. For a group that has a field manual that tells you how to wipe you butt properly, that’s hell of an oversight.

    I’m sure someone has been underneath a 50 on a hummer when it let off. Did they die? No, they went deaf and got royally pissed off that it happened.

    It‘s like people saying a 45 acp will knock you off your feet. So why can I stay standing and fire rapid strings with it then? Hello basic physics....

    I‘m always saddened that people glom onto a single statement and don’t do anything to look at it more broadly and see that it makes no sense. But it does explain why the country is in the mess it’s in.
     

    Tokay444

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  • Jun 24, 2019
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    From my original post:
    "If the pressure wave is close enough and powerful enough, it could do some damage."

    Do you disagree with this?
    I do, yes.
    How much closer, or more powerful does the, “pressure wave” need to be to knock over that house of cards?
     
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    Praetorian_6

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    No paypal, no credit card, no other form of buyer's protection. Just send me thousands in cash or money order, and maybe if this stranger-to-you is actually a good person, I'll send you this rifle/optic/accessory in the condition I said it was in or at all. Don't worry. You can trust me. A group of other complete strangers, or maybe bots, said I was a great seller.
     

    Downtown

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  • Mar 1, 2013
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    From my original post:
    "If the pressure wave is close enough and powerful enough, it could do some damage."

    Do you disagree with this?
    Man, I really hate to weigh in on this. The pressure wave from even a large bullet is small enough and weak enough that you can't get close enough to do any damage. Even a few fractions of an inch isn't close enough. Now I hate myself for stating something so obvious outloud.
     

    slowworm

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    Man, I really hate to weigh in on this. The pressure wave from even a large bullet is small enough and weak enough that you can't get close enough to do any damage. Even a few fractions of an inch isn't close enough. Now I hate myself for stating something so obvious outloud.
    Yup. So often people confuse the potential gradient with the capacity to do useful work. Like those plasma balls where the plasma trails follow your hands as you touch the globe. The plasma is at a temperature of thousands of degrees, but you feel nothing. Huge potential gradient, zero capacity for useful work. A match is frigid by comparison, but no way am I sticking my finger in the flame...
     

    Praetorian_6

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    This is the stupidest fuggin thing to argue about. Just imagine for a second that there was a cylinder of air 1/2" in diameter next to your skin and it was a COMPLETE vacuum. Air pressure is 14.7 psi. That's the pressure of everything around you and your skin trying to fill that void. Imagine hanging a 7.5 lbs weight for every inch of the length an object is glued to your skin. Will it tear? No. So, if the vacuum can't reasonably do it, what about the pressure on the leading edge of the bullet?

    Again, no. The pressure wave pushes that cylinder of air out to the area around it, but it doesn't all go to one side. It goes to the entire circumference of the bullet. Once it fills the same volume outside of the cylinder as the volume of the bullet inside of the cylinder, and again assuming the PERFECT vacuum in the cylinder and air displaced to the area outside of the cylinder, which is an assumption that's not even close but highly favors the near-miss destruction argument, it would double the pressure -- twice the air molecules in the same amount of space. So, how far from the edge of the bullet would that be? I've done the math: it would be 0.207 extra inches. So, if a bullet passed just 2 tenth of an inch from you, you would not feel more than 14.7 psi extra. Put a 15 lbs weight on a 1"^2 area of your skin. Maybe it would be uncomfortable. Damage? No.

    The physics may support that at some razor-thin distance from a bullet without actually touching the skin, you might tear the skin ever so slightly.... maybe. Or maybe the incoming shockwave would just push the skin enough away that it wouldn't tear at all. At a distance that close, though, you might as well just say the bullet hit you, for all practical purposes.

    If none of that makes any sense to them, or they're one of the anti-intellectual knuckle draggers that like to deny facts and science, then just invite them to watch:
     
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    eastexsteve

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    That's not a pressure wave.

    View attachment 7561286

    That's not a pressure wave.

    View attachment 7561286
    One way to understand it, is to find someone who has an airplane. It doesn't even have to be fast. I do this all the time for kids. An airplane at a speed of 100 knots or more is fast enough. Maintain level flight and altitude, then initiate a 20 to 25 degree bank turn left or right about 45 to 60 degrees and be careful to maintain altitude. You will eventually fly through the pressure waves you were creating before you turned. It feels just like you are running over your own boat wake if you were in a boat. The only difference is the pressure waves are air and not water.
     
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    lash

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    One way to understand it, is to find someone who has an airplane. It doesn't even have to be fast. I do this all the time for kids. An airplane at a speed of 100 knots or more is fast enough. Maintain level flight and altitude, then initiate a 20 to 25 degree bank turn left or right about 45 to 60 degrees and be careful to maintain altitude. You will eventually fly through the pressure waves you were creating before you turned. It feels just like you are running over your own boat wake if you were in a boat. The only difference is the pressure waves are air and not water.
    So, turbulence then. 😉
     

    slowworm

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    One way to understand it, is to find someone who has an airplane. It doesn't even have to be fast. I do this all the time for kids. An airplane at a speed of 100 knots or more is fast enough. Maintain level flight and altitude, then initiate a 20 to 25 degree bank turn left or right about 45 to 60 degrees and be careful to maintain altitude. You will eventually fly through the pressure waves you were creating before you turned. It feels just like you are running over your own boat wake if you were in a boat. The only difference is the pressure waves are air and not water.
    That's a turbulent wake. In a light aircraft mostly caused by propwash and a little bit from the tip vortices. The bow wave is long gone by the time you cross your own wake.
     

    Johnny00K

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    I love it when these types of people back every thing up very scientifically with “it makes sense”. I guess looking around then the earth is flat, after all it “makes sense”.
    I survey with gyroscopes for a living. Their measurements come from the rotation of the earth. I absolutely love flat earthers, some of the most entertaining people on earth.
     
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    hereinaz

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    One way to understand it, is to find someone who has an airplane. It doesn't even have to be fast. I do this all the time for kids. An airplane at a speed of 100 knots or more is fast enough. Maintain level flight and altitude, then initiate a 20 to 25 degree bank turn left or right about 45 to 60 degrees and be careful to maintain altitude. You will eventually fly through the pressure waves you were creating before you turned. It feels just like you are running over your own boat wake if you were in a boat. The only difference is the pressure waves are air and not water.

    Explain how a 50 cal, or any bullet really, only leaves bullet sized holes in paper if it can kill a deer with the "pressure wave".

    Also explain why this massive pressure wave powerful enough to kill the deer without hitting it doesn't blow the fur off a critter it actually hits.

    I really have a feeling this is an epic troll in this thread...
     

    308pirate

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    One way to understand it, is to find someone who has an airplane. It doesn't even have to be fast. I do this all the time for kids. An airplane at a speed of 100 knots or more is fast enough. Maintain level flight and altitude, then initiate a 20 to 25 degree bank turn left or right about 45 to 60 degrees and be careful to maintain altitude. You will eventually fly through the pressure waves you were creating before you turned. It feels just like you are running over your own boat wake if you were in a boat. The only difference is the pressure waves are air and not water.

    I'm a private pilot. And an engineer.

    But thanks anyway........
     

    BullGear

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  • Nov 29, 2017
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    Call it what you want. Anything flying through the air displaces the air and causes a momentary differential in the air pressure.

    Not the UFO I saw last week. No air pressure difference for over 10k miles. I calculated it to be flying at Mach 9.327460819.
     

    eastexsteve

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    Explain how a 50 cal, or any bullet really, only leaves bullet sized holes in paper if it can kill a deer with the "pressure wave".
    Again, from my original post:
    "If the pressure wave is close enough and powerful enough, it could do some damage."

    Now, I don't know if a .50 BMG would be up to the task. Also, as I said earlier, I think he shot the deer through the eyes.
     

    lash

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    Call it what you want. Anything flying through the air displaces the air and causes a momentary differential in the air pressure.
    At the risk of repeating something already said, it’s fluid dynamics. Can’t remember whether 101 or 102. When you remember how water creates wake and turbulence, you’ll realize that it not a pressure wave, but turbulence. Those are not two different ways to say the same thing. They are different.
     
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    eastexsteve

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    At the risk of repeating something already said, it’s fluid dynamics. Can’t remember whether 101 or 102. When you remember how water creates wake and turbulence, you’ll realize that it not a pressure wave, but turbulence. Those are not two different ways to say the same thing. They are different.
    The effect as I described is the same. In both instances, you are experiencing a change in pressure. Do you think turbulence exists without momentary or rapid changes in air pressure? And, the object doesn't have to be traveling at supersonic speed to create this. Just stand next to the road as a big truck at highway speed passes close by.
     

    Longshot231

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  • Mar 8, 2018
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    "I would never treat you the way your ex-wife treated you."

    Okay. Okay. That's more of a lie than something stupid. On the other hand, I was stupid enough for believing it!

    Don't laugh. Some of you have been taken in by that statement. You know who you are.
     
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    Tokay444

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    Call it what you want. Anything flying through the air displaces the air and causes a momentary differential in the air pressure.
    I call it what it is.
    Because air is a fluid.
    Again, just please stop.
     

    slowworm

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    Are we still going on about a fucking 50 doing damage even if it doesn't hit its target? FFS.
    It's the bear pit. Of course we are still at it.

    Edit: Just noticed we are actually in the advanced marksmanship section. Hmmmm....:sneaky:
     
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    gimpy

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    Back in ‘03, outside the airbase near Balad, some Nasty Guards must’ve been asleep in their watch tower and never heard our mortars announce they were coming by on a dismounted patrol.

    Needless to say, someone in the guard tower noticed people walking in the dark several hundred yards out and decided to engage. The squad hit the dirt, but one of the guys caught a glancing blow just at the edge of his plate.

    He lived to show what was left of the plate, and had a massive bruise on one side of his back. I never realized how lucky he was to have survived the sonic boom 🤯 🤣
     

    theLBC

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