I am writting a novel ( in a world where magic exists, and is evolving every second )

A lucky guy, found the notes of an ancient artificer on a training artifact. The artifact was very easy to make and with him straining the relationships he had with every single person, and visiting many artificers for him to create the small intricate components, he gained some progress ( he didn't raise any suspension, as he was very careful with what he was doing, and he spread rumors of him trying a new crazy idea that was bound to fail, but that he was blinded by the 'what if' he succeeded. Basically half truth half lies, covered up in dirt. )

After almost 3 months of him 'dying' to create the artifact ( with some failures along the way ) he succeeded.

The artifact has 3 stages and wasn't highly ranked in the ancient times.

The first stage could amplify the gravity on a small area by 1,5 times the original ( how small exactly or how big, haven't been decided yet )

The second stage could double the gravity.

And the third stage could effectively triple it.


I don't care much about the second or third stages, but what effects would 1,5 times the gravity have on a human ???

I can explain the second stage by saying that his body was strengthened by the first, and do the same for the third.

I pretty much can predict that he will have a problem with his internal organs, eyes, brain, blood flow and so on.

If anyone though could tell me the effects of that stronger gravity, I would be forever grateful.


The question is indeed quite similar to this But I'm asking for the effects, not survivability.

  • $\begingroup$ Assuming that you weigh 80 kg, put on a 40 kg backpack, carry it around while you do your daily activities and see for yourself how you feel after 12 hours... $\endgroup$
    – AlexP
    Mar 24, 2017 at 23:55
  • 3
    $\begingroup$ Possible duplicate of Would the human body support living on planets with a greater gravity than Earth? $\endgroup$
    – Aify
    Mar 25, 2017 at 0:32
  • $\begingroup$ @AlexP: I've actually done that on occasion, and climbing up mountains, too. But I vastly prefer something closer to 20 kg. Still, once you're in training it's not impossible - probably about the weight of modern combat gear. $\endgroup$
    – jamesqf
    Mar 25, 2017 at 4:45
  • $\begingroup$ When I was young I carried a pack about half my weight through the white mountains. I carried a lot of stuff, a more experienced hiker would have probably carried less. It's not too difficult for the young, skinny and in shape to carry half their weight and hike 10 miles a day. It's tiring but not crazy difficult. $\endgroup$
    – userLTK
    Mar 25, 2017 at 9:40
  • $\begingroup$ Haven't ever tried carrying a backpack that heavy and go hiking... $\endgroup$ Mar 25, 2017 at 10:01

3 Answers 3


Carrying a 40kg backpack, as suggested by one commenter, is not a good analogy. The backpack does not account for the differences in blood pressure, and there are other important differences that we will get to shortly. But let's first consider the blood pressure issue!

A great body (no pun intended) of knowledge about the effects of excess $g$-forces on the human body comes from military research that tries to determine what the limits are for fighter pilots (who necessarily experience high acceleration when they pull tight turns).

From https://en.wikipedia.org/wiki/G-LOC:

High-G training for pilots of high performance aircraft or spacecraft often includes ground training for G-LOC in special centrifuges, with some profiles exposing pilots to 9$g$ for a sustained period.

Of course, this requires a $g$-suit and a lot of training on top of starting with a genetic background that permits a level of physical fitness that is not particularly representative of the capabilities of the average human being. Also, the pilots are sitting, not standing.

Fortunately, the air force also ran a few experiments on untrained people for comparison:

An un-trained individual not used to the G-straining manoeuvre can black out between 4 and 6 g, particularly if this is pulled suddenly.

So, we can safely conclude that 1.5$g$ is definitely not a blackout condition for the average Joe, even in a standing position. The difference between sitting and standing is only a slight one, because sitting does not prevent the blood from rushing from your knees to your feet. It only prevents the pressure differential over the length of your thigh (which is on average about 1/4 of a person's height).

In terms of effort expended to stand and more around, yeah, at 1.5$g$ you will feel 1.5 times your body weight. However, this is not equivalent to carrying a 40kg backpack for an 80kg person because the additional weight is very optimally loaded - it's configured precisely like the load you normally carry around, just 50% higher everywhere in your body. Whereas a backpack will produce a lot of non-uniform loading and be much more cumbersome for the same effective increase in weight.

The limiting factor at 1.5$g$ will probably be the blood oxygen flow to the upper back and neck muscles, needed for maintaining a standing pose. The reduced blood flow, coupled with the increased weight demand at 1.5$g$ would likely prevent the muscles from operating aerobically. Thus, rather than burning oxygen, the muscles would have to generate energy through glycolysis as they do during in an intensive workout. This will result in operating normally for a while but eventually reaching a state of fatigue, probably within 30 minutes or so for the average Joe but likely extendable to a few hours for a physically fit person with training in such an environment.

The fix for our hero, obviously, is to lie down when he is tired and allow his/her back and neck muscles to recuperate under conditions of normal blood flow. If some loss of dignity is acceptable, our hero may also resort to crawling around on all fours and minimizing the amount of time spent standing (since standing causes the bulk of the endurance penalty in our 1.5$g$ environment).

Our hero should also use every opportunity to swim from point A to point B, because being submersed is like wearing an ideal $g$-suit - the pressure differential is approximately the same outside the body as in and blood flow will be close to normal so there would be no endurance penalty for additional $g$s. If our hero gets tired while swimming he or she should definitely not attempt to tread water though - the higher $g$ value will amplify the water pressure, making it much more difficult to breathe since our neat argument of equal submersion pressure doesn't apply the interior of the lungs which are at only air density rather than approximately water density. Instead, our hero should just lie back and relax while floating near the water's surface.

  • $\begingroup$ Quite detailed. $\endgroup$ Mar 25, 2017 at 9:49
  • $\begingroup$ Are you sure treading water is that bad? Scooba divers don't seem to have much trouble breathing and they can be under much greater pressure. $\endgroup$ Mar 25, 2017 at 19:18
  • 1
    $\begingroup$ @PyRulez I'm glad you asked that because I'm actually a PADI certified open water diver and I love to share my knowledge of diving :) The trick to breathing at higher pressure is that the "regulator" you breathe from makes the compressed air in the tank come out at the same pressure as the surrounding water. Thus the air is also consumed more rapidly at depth than near the surface because the breath has the same volume but the air being breathed is that much denser. At 30 meters (a reasonable recreational dive depth), the air pressure and density is three times atmospheric. $\endgroup$ Mar 25, 2017 at 19:36
  • 1
    $\begingroup$ @PyRulez Running out of air on deep dives is not the limiting factor though - at 30m depth you have only 22 minutes to enjoy the surroundings while being able to make a safe ascent at any time. After that, it's recommended to make a short "decompression stop". Beyond 25 minutes, it's no longer open water diving because decompression becomes mandatory and it is no longer safe to ascend immediately in an emergency. $\endgroup$ Mar 25, 2017 at 19:41

I should point out that a person who weighs 1.5 times or 2 times or 3 times normal weight for their size and is reasonably active is experiencing some but not all of the effects that a person of normal weight would experience in 1.5 gs or 2 gs or 3 gs, and for prolonged periods of time.

I once read something that tests about hwo long humans could endure constant higher gravity were ended after a week in 1.25 gs when the test subjects started to show signs of deteriorating health. Thus your character should be able to experience minutes or hours at 1.5 gs or 2gs or 3gs with no problems but could kill himself trying to live in 1.5 gs permanently.

This article indicates that test subjects have experienced 1.5 gs for a week.


  • $\begingroup$ Thanks for the info. I wasn't planning to let him live there indefinitely, but I will be sure to lower the time he gets to spend with higher gravity now. After all I don't want him a walking zombie... $\endgroup$ Mar 26, 2017 at 8:00

The long term effects would include angiological problems such as increased risk of embolies and varicose veins, and accelerated aging of the skin. Also, if there is reproduction under these conditions, children will tend to be quite shorter, as their muscles would have to become very strong at an early age, thus making the lengthwise development of long bones more difficult.

Something to be taken into account is air pressure, which I imagine would be influenced by higher gravity (how does that play if such gravitational increase is limited to a relatively minor area of the planet?)


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