# The Earth now has 95% of its former gravity, what happens? **URL:** \ **Category:** Factual Questions\ **Created:** [June 8, 2011, 9:39pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786 "2011-06-08T21:39:24Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 9, 2011, 6:31pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/61 "2011-06-09T18:31:56Z")
> [@treis](#): > > Do you have a cite saying that they had difficulty walking, or were specifically training in how to walk? [The Lunar Walking Problem](http://www.wired.com/wiredscience/2009/07/nasaarchive_gravitysimulator/) > [@](#): > > The simulator, located at the Lunar Landing Facility at NASA’s Langley Research Center in Virginia, was described in a 1964 paper titled “Discussion of Existing and Planned Simulators for Space Research”: > > “When the astronauts land on the moon they will be in an unfamiliar environment involving, particularly, a gravitational field only one-sixth as strong as on earth. A novel method of simulating lunar gravity has been developed and is supported by a puppet-type suspension system at the end of a long pendulum. A floor is provided at the proper angle so that one-sixth of the subject’s weight is supported by the floor with the remainder being supported by the suspension system. This simulator allows almost complete freedom in vertical translation and pitch and is considered to be a very realistic simulation of the lunar walking problem.” I don’t see why they would call it the “lunar walking problem” if it wasn’t, you know, a problem. ---
**Author:** ![treis](https://avatars.discourse-cdn.com/v4/letter/t/bc79bd/32.png) [@treis](https://boards.straightdope.com/u/treis)\ **Post date:** [June 9, 2011, 8:05pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/62 "2011-06-09T20:05:16Z")
> [@Fear\_Itself](#): > > [The Lunar Walking Problem](http://www.wired.com/wiredscience/2009/07/nasaarchive_gravitysimulator/)I don’t see why they would call it the “lunar walking problem” if it wasn’t, you know, a problem. It looks like they were looking at stuff like speed, fatigue, etc. I don’t see any indication it was used to prevent astronauts from tripping over their own feet. Up thread there 1% was given as the change in gravity while flying. That’s in the same order of magnitude as the change we are talking about in this thread, and I haven’t noticed any difference walking there. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [June 9, 2011, 8:40pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/63 "2011-06-09T20:40:30Z")
> [@Enilno](#): > > I’m not sure it’ll be quite so dramatic, but I figure there’s going to be a lot of earthquakes and volcanic activity as the surface of the Earth shifts to a new equilibrium. The earth’s small inner iron core IIRC is about 50 percent denser than normal due to all the pressure of the layers above. If gravity dropped by .05 percent my very rough calcs indicate its surface would expand outwards/upwards something like 10 miles. Not only that, but that whole 4 thousand or so miles of material above it also compressed and will expand when gravity decreases. Lets assume on average its only compressed about 5 pecent over normal. That gives you something like another 10 miles of upwards expansion. If that G change happens over just a few seconds, the upward lift of 10s of miles in short order is gonna be bad. And thats ignoring all the massive quakes that would like be set off due to shockwaves bouncing around and causing fault line to release all that energy. And the sloshing water? Oy Veh. ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [June 9, 2011, 9:24pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/64 "2011-06-09T21:24:01Z")
> [@treis](#): > > I don’t see any indication it was used to prevent astronauts from tripping over their own feet. Since NASA didn’t use that precise terminology, it looks like I can’t support my claim. ---
**Author:** ![RaftPeople](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)\ **Post date:** [June 9, 2011, 9:43pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/65 "2011-06-09T21:43:30Z")
Would an airplane in the process of landing be in danger of overshooting the runway? ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [June 9, 2011, 10:30pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/66 "2011-06-09T22:30:22Z")
Look on the bright side—a phenomenal weight-loss program. Dieting? Exercise? Pshaw. Lose weight the easy way. I predict it’ll be a hit in a country as obese as America. But for circus performers who get propelled out of cannons, they would overshoot the net and hit the ground. The force applied to them has to be very precisely calibrated based on their weight and flying distance. Hope they have a chance to recalibrate before performing when the gravity changes, or they’re going to be awfully sorry. There have been tragic errors under the big top that way. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 9, 2011, 11:46pm UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/67 "2011-06-09T23:46:20Z")
> [@Quercus](#): > > You didn’t post elevator speeds; you posted accelerations. I don’t know much about elevators so don’t know if they’re accurate, but the posted accelerations which are all higher than 0.05G. And since I do not usually notice a falling feeling from most elevators, I maintain that I, at least, would not notice a change from standing at 1-G to 0.95-G. There seems to be a ton of confusion on this point. If the Earth lost 5% of it’s gravity, it would not feel like a dropping elevator, and you’d adapt to it instantly, not over “days, weeks, or months.” Your body can’t actually detect gravity. Astronauts in space are still subject to the Earth’s gravity, even though they’re “weightless.” They’re in a prolonged descent - they’re falling at the Earth and missing, so to speak. To get back to the elevator example, what you’re feeling is a sudden decrease in normal forces on your feet. The elevator is moving down, which lessens how much it can press up on you. Your body interprets this decrease in normal force as a decrease in weight. However, the earth is not moving away from you. It’s staying exactly the same size, as per the OP. The ground is exerting a constant normal force to your feet (an equal and opposite reaction to your weight pressing down on the ground), and thus it won’t feel like an elevator. You’ll feel a little lighter on your feet, but standing around will feel exactly the same as standing around at 100% gravity. ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 10, 2011, 12:02am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/68 "2011-06-10T00:02:42Z")
> [@Astral\_Rejection](#): > > If the Earth lost 5% of it’s gravity, it would not feel like a dropping elevator … . No, it would feel [EXACTLY](http://en.wikipedia.org/wiki/Equivalence_principle)like a dropping elevator. In particular, it would feel like the start of the drop where the elevator is accelerating. > [@](#): > > Your body can’t actually detect gravity. But your body CAN detect acceleration, as anyone who has ever ridden in a car can attest. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 12:08am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/69 "2011-06-10T00:08:44Z")
But the earth isn’t accelerating anywhere. It’s staying put. You wouldn’t be accelerating anywhere either. You’re likewise staying put. Acceleration has nothing to do with this. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 12:09am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/70 "2011-06-10T00:09:56Z")
(I mean to say, physically speaking, from our frame of reference the earth isn’t accelerating anywhere) ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 10, 2011, 12:13am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/71 "2011-06-10T00:13:20Z")
> [@Astral\_Rejection](#): > > But the earth isn’t accelerating anywhere. It’s staying put. You wouldn’t be accelerating anywhere either. You’re likewise staying put. Acceleration has nothing to do with this. Read the link. As Einstein showed, gravity and acceleration are _indistinguishable_. If you’re in a sealed room (like an elevator) you can’t tell the difference between a decrease in gravity and a constant downward acceleration. The effects are identical. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 12:27am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/72 "2011-06-10T00:27:02Z")
I think where you’re stumbling is that gravity isn’t decreasing at a constant rate. It’s 95% of our current value, and that’s it. If you went to the moon (roughly 1/6th of Earth’s gravity), it won’t feel like an elevator always going down. A sudden decrease to a flat rate isn’t the same as a constant decrease in gravity. Your link about Einstein is for a different but related subject. ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 10, 2011, 12:41am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/73 "2011-06-10T00:41:56Z")
> [@Astral\_Rejection](#): > > I think where you’re stumbling is that gravity isn’t decreasing at a constant rate. It’s 95% of our current value, and that’s it. If you went to the moon (roughly 1/6th of Earth’s gravity), it won’t feel like an elevator always going down. Think about what would happen if you stood on a scale in an elevator that’s going down. At the beginning of the ride, as you begin to accelerate, the scale will show you weighing less. Then as the elevator reaches its maximum speed the scale will settle back to your normal weight. And at the end of the ride as the elevator decelerates the scale will show you weighing more. That initial part of the trip, when the elevator is getting up to speed, will feel EXACTLY the same as a decrease in gravity. You can’t tell the difference between a decrease in gravity and a downward acceleration. In both cases the scale shows you weigh less. You’ll experience exactly the same physiological effects. Now a typical elevator will accelerate at about 1 m/s/s. The change in gravity described in the OP is about 1/2 that. So the effect will be subtle, but its not inconsequential. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 12:45am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/74 "2011-06-10T00:45:48Z")
I’ll let somebody else tackle this, so for now we have to agree to disagree, but I do want to give a quick counter-example: If you were on the moon, would it feel like you were on an elevator? Mars? Pluto? Each has less gravity than the Earth. Will it feel like you’re standing on an elevator? Why or why not? ---
**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\ **Post date:** [June 10, 2011, 12:49am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/75 "2011-06-10T00:49:51Z")
> [@Astral\_Rejection](#): > > If you were on the moon, would it feel like you were on an elevator? If I were instantly teleported there, yes … until I had a chance to psychologically and physiologically adapt to the new gravitational field. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 10, 2011, 2:39am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/76 "2011-06-10T02:39:17Z")
> [@](#): > > But the earth isn’t accelerating anywhere. It’s staying put. You wouldn’t be accelerating anywhere either. You’re likewise staying put. Acceleration has nothing to do with this. The Earth is staying put, but it’s still accelerating. Every point on the surface of the Earth is accelerating upwards at 9.8 m/s[sup]2[/sup]. The astronauts on the Space Station, by contrast, are not accelerating. It turns out that accelerometers don’t actually lie to you. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 3:03am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/77 "2011-06-10T03:03:18Z")
(psst, you mean downwards) And you’re incorrect anyway. I’m not accelerating downwards. I’m not moving. Gravity is exerting a 9.8 meters per second squared force at all times, which accelerates me downward if I were to jump, starting the second I leave the ground. But once I stop moving, I’m not accelerating anymore, even though gravity is still exerting a 9.8m2 force. The crux of the matter is how it would feel. If the earth exerted a 9.7m2 force, I’d still be just as motionless on the surface, only I’d feel a tiny bit lighter. The earth wouldn’t suddenly be shrinking away from me (like an elevator would), and thus I wouldn’t feel a constant downward motion (like in an elevator). The downward motion feeling is a result of the floor moving away and exerting a smaller normal force on my body. In the elevator, gravity is still 9.8m2, so clearly the “elevator feeling” is unrelated to gravity. ---
**Author:** ![Astral\_Rejection](https://avatars.discourse-cdn.com/v4/letter/a/258eb7/32.png) [@Astral\_Rejection](https://boards.straightdope.com/u/Astral_Rejection)\ **Post date:** [June 10, 2011, 3:04am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/78 "2011-06-10T03:04:53Z")
And to address your astronaut point, do you think gravity stops at the edge of the atmosphere? The Earth’s gravity is most assuredly still pulling on the astronauts, or orbits wouldn’t work. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 10, 2011, 3:30am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/79 "2011-06-10T03:30:06Z")
> [@](#): > > (psst, you mean downwards) > > And you’re incorrect anyway. I’m not accelerating downwards. I’m not moving. No, I mean upwards, and when you’re not moving, you’re accelerating. The only force acting on you when you’re standing on the ground is the normal force of the floor on your feet, and that force is pointing upwards, and thus so is your acceleration. > [@](#): > > And to address your astronaut point, do you think gravity stops at the edge of the atmosphere? The Earth’s gravity is most assuredly still pulling on the astronauts, or orbits wouldn’t work. Of course gravity doesn’t stop at the top of the atmosphere, but it’s not a force, and it doesn’t pull. If something were pulling on the astronauts, they’d be traveling on a curved path, instead of along a geodesic. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [June 10, 2011, 3:33am UTC](https://boards.straightdope.com/t/the-earth-now-has-95-of-its-former-gravity-what-happens/584786/80 "2011-06-10T03:33:31Z")
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