Say, one day, Earth’s gravity fell five percent from where it’s at now. So it’s at 95% of what it usually is. Here’s a bunch of questions: How long would it take the average person to notice? How long would it take a scientist to notice? I mean, a scientist for whom gravity is important? Engineers? Would it be immediately obvious that a reduction in gravity was responsible for whatever they were seeing? How would it affect how we operated in the world? How planes are built, maybe? Or how we conceive of major (or even minor) engineering projects? What other difficulties would arise as a result?
Everyone would notice at the same time, when we all suddenly started tripping over our own feet. Walking is a lot more complicated than most folks realize; we’re just really practiced at it.
Airlines would notice it immediately, I imagine. Thousands of flights every day, and they’re going higher than the thrust says they should be. I’d guess about 30 seconds before someone notices something’s up, 5 minutes before they realise it’s happening everywhere, 10 minutes before someone figures out gravity has changed.
Americans would get even fatter!
A significant portion of the atmosphere would disappear into space, so it would have a profound effect on the biosphere, from the ozone layer that protects us from ultraviolet, to oxygen and carbon dioxide levels that sustain life.
How would the orbit of the moon change? I assume it would become more elliptical.
Could you elaborate on what is meant by gravity reducing?
Do you mean the earth will lose mass? (It’s actually gaining mass, I believe) Or that the Gravitational Constant will somehow get smaller.
I’m not debating the validity of it happening - but I believe there are different mechanisms that will have different results.
If it happened very quickly pretty much everybody would be killed and most things destroyed as the surface of the earth sprung up many feet in a short period of time. I’ll let somebody else calculate how many feet/miles the spring up is.
I’m going to ignore cataclysmic effects like billfish mentioned, or the loss of the atmosphere, etc. I don’t know enough about the earth’s equilibrium to say anything about that.
I don’t think it would be all that easy to notice, especially if it happened over a period of minutes or hours. Everything weighs 5% less, but still has the same inertia. That’s not a huge effect.
My car, instead of weighing 3500 pounds, weighs 3325. Instead of weighing 200 pounds, I weigh 190. I can carry a 10-pound backpack without even noticing it, as can most people I suspect.
Pilots would conclude that they miscalculated their passenger/cargo/fuel load, if they even noticed at all.
I suspect some physicist doing an experiment would notice first, but it would take several hours before he concluded that it was not simply an error in his measurement apparatus.
Of course, anyone can test the strength of gravity for himself by weighing a known volume of water on a kitchen scale.
I don’t know. I kept my hypothetical purposefully vague in that regard simply because I don’t know a whole lot about gravity. When I wrote the question, I had in my mind’s eye an image of the Earth that retained its size and shape. The gravitational change was localized to Earth, too. No other planetary bodies experienced anything similar, though whatever effect Earth’s change has on them is fair game.
Pound cake recipes around the world would suddenly become unworkable or even worse, toxic. Kilogram cakes who knows? (that wacky metric system)
Several folks have mentioned the atmosphere. IMO if the change in gravity was slow enough, it would not have an immediate or tragic effect or probably not even noticible. Long term might be a different story.
I disagree with some of the predictions, it would take a very long time for any signifcant evaporation of the Earth’s atmosphere to occur if Earth were to lose 5% of it’s mass and a compartively heavy gas like ozone would feel this effect less than other gases, ditto carbon dioxide.
In terms of the the effct it would have on my weight it would be like losing just over 10 pounds for me, which I think I may feel but then again the effect would not be drastic.
The volume of the Earth’s atmosphere would immediately become greater as the atmosphere expanded, even if no gas was lost to space. This would result in an immediate decrease in the density of the atmosphere, and immediate lowering of the concentrations of the various gases. No gas has to leave the atmosphere for this to happen; the volume of the atmosphere just gets larger as a result of lower gravity.
everyone would think they were wearing Keds sneakers
Even this is a relatively minor effect - the air density at 1500 feet above sea level is approximately 95% of that at sea level. People live just fine at 5,500 feet in Denver, where the air is about 20% less dense than at sea level, and at 10,000 feet in Leadville, where it’s maybe 35% less dense.
That is true I did not account for pressure, but accounting for that and assuming the Earth’s atmosphere is an ideal gas (which of course it isn’t) that still only means an instantaneous increas of volume of about 5.3%
You say “only” 5.3%, when we really don’t (I don’t, anyway) know whether that is insignificant or not. For all I know, 5.3% is the difference between abundant life and catastrophe. Yes, life exists at 5500 feet, but most of the oxygen in atmosphere is generated in the rain forest and other large green areas at much lower altitudes that do not thrive at that altitude. Global warming is predicted to be cataclysmic at an average global increase of only 2 degrees; thinking globally, only a small change in air pressure could have similar calamitous effects on the biosphere as a whole.
From a common man’s point of view.
Any pendulum clocks would be off by about 5 percent. Or the square root of five percent (I forget). Thats more than an hour a day. That kind of error would be noticable pretty quick to any person with such a clock. So, even if it was a gradual change its not like it would take a guy in a lab to notice it.
You’d feel it instantly in the pit of your stomach.
A drop in gravity of 5% would feel just like standing in an elevator accelerating downward at about 1.5 ft/s^2. Most real-world elevators have accelerations in the range of 2 to 5 ft/s^2, so the feeling of the floor dropping out from under you would be definitely noticeable.
No, you wouldn’t notice this, as you don’t accelerate anywhere when you are standing on the floor.
Ignoring the catastrophy of the Earth springing into a larger shape, I don’t think it would be that noticeable. I wonder what would happen to a loaded structure, such as a suspension bridge?