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  • Hey guys, Matt here with Science or Fiction.

  • Is there a speed that would harm humans?

  • There are a bunch of human speed records that are going to be broken in the coming decades

  • as we develop the technology to travel thousands of miles in minutes by land, send commercial

  • flights into low-earth orbit, and attempt to get humans to Mars.

  • So with all of these possibilities on the horizon, a question you might be asking yourself

  • isHow fast is too fast?”

  • Well, first of all, wherever you are, no matter what you are doing, you are traveling nearly

  • 67,000 mph around the sun.

  • It just doesn't feel that way because the Earth, and therefore humans, have been traveling

  • at that constant rate for, well, you know, kind of a while.

  • We can actually survive any speed, as long as it remains constant.

  • It's when acceleration enters the equation that things can get pretty tricky.

  • In fact, if you accelerate at a high enough rate, you will pass out and very possibly

  • die.

  • This is because of what happens to the human body when it experiences g-force, or the unit

  • of measure for acceleration.

  • It's based on Earth's gravitational pull.

  • One “G” is the force applied to an object by gravity while on the Earth's surface.

  • It's also the force that determines how much we weigh.

  • So, simply put, if a human experiences three Gs, they experience a force on their bodies

  • that is three times their weight.

  • We can experience the G force in different ways.

  • If we accelerate horizontally like in a car or train, we can experience g-force either

  • front-to-back or side-to-side.

  • We can actually withstand quite a bit of g-force when it's hitting us horizontally.

  • It's when things go vertical, which mostly happens only on airplanes, roller coasters,

  • or during space launches, that things get much more dangerous much more quickly.

  • Vertical g-force can be experienced negatively (foot to head) or positively (head to foot).

  • Both can be experienced in an airplane or rocket, and both can pose serious threats

  • to our health because of what happens to all the liquid in our bodies under these circumstances.

  • With a high level of negative Gs, blood can end up collecting in our heads.

  • Sometimes a “red outwill occur, with the lower eyelids swelling up so much that

  • they cover the pupils.

  • If enough blood pools in the head, which can happen around 2 or 3 negative Gs, a person

  • will lose consciousness.

  • Yikes.

  • And other scary stuff happens when force is applied from head-to-foot and blood starts

  • to pool in the lowest parts of our bodies.

  • At 1 G, or normal conditions, our bodies require 22 millimeters of mercury blood pressure to

  • pump blood from the heart to the brain.

  • That requirement doubles at 2 G, triples at 3 G, and so on.

  • There's a certain point at which our bodies can no longer muster the energy needed to

  • pump the blood, which happens around 4 or 5 Gs.

  • Blood ends up pooling in the feet, and the rest of the body receives such a lack of oxygen

  • that a person first loses vision due to a lack of blood flow to the eyes and then consciousness

  • altogether when the brain loses enough of its blood flow.

  • This phenomenon is known as G-LOC, or G-induced loss of consciousness.

  • Both head-to-foot and foot-to-head vertical g-forces can eventually lead to death if they

  • last long enough.

  • So, given that humankind is on the precipice of breaking many speed records, and given

  • that many of the airplanes and spacecrafts that will be involved could one day fly your

  • average Joe across the country at record speeds, how can we make sure that we, you know, don't

  • die?

  • Pilots do a number of things to train for serious g-s.

  • The better shape they are in, the more able they are to control their body's blood flow

  • with their muscles.

  • Leg and abdominal muscles must be particularly strong so that when pilots tense these muscles,

  • they can keep the blood from draining to their legs while experiencing positive g-force.

  • Well, it's sort of unrealistic to expect everyone to have abs of steel, so other solutions

  • might be needed if we are to expect average people to eventually accelerate at rates currently

  • only safe for fighter pilots.

  • One solution could anti-g suits, which pilots have been using since World War II.

  • They utilize air bladders to keep the blood in our bodies where it should be.

  • Fortunately, we haven't quite reached the point where people like you or me (unless

  • there are a lot of fighter pilots watching this episode, then I take that back) are going

  • to be accelerating at deathly rates.

  • There is still time for us to figure out how to manage all that.

  • For more epic stories of innovation that shaped our future check out THE AGE OF AEROSPACE.COM

  • Did you know we learned a lot about how g-force affects the body from one guy shooting himself

  • down a track in a rocket sled?

  • It's true, check it out here.

  • Before you do that, make sure to subscribe and be sure to keep coming back to Seeker

  • for more videos.

Hey guys, Matt here with Science or Fiction.

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How Much Acceleration Can the Human Body Take?

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    joey joey posted on 2021/04/13
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