Gravity already varies on Earth depending where you are. The pull of gravity on top of Pike’s Peak is stronger than on the Atlantic Coast (on top of the mountain, you have more of the Earth under you; at the base of maountain you’ll some mass above you, and pulling in the opposite direction). So, if you’re really interested, you can go see if people who live at hihg elevations are stronger than people in the lowlands.
Frankly, I would guess we are getting stronger, but not becuase of gravity. I’m stronger than my father at the same age, but then I’m ten inches taller and a hundred pounds heavier, and if increasing gravity were really the cause of my greater strength, then it should have done so without increasing my vertical height and total mass, both of which are maladptions to increased gravity. Increased strength? Chalk up it to better nutrition.
Also about your time traveling idea–be careful where you go–our cousins the chimps, despite being smaller than us, can kick the crap out of a full grown male. I suspect that some of our other non homo sapien sapien ancestors could do the same, and you probably don’t want to pick a fight with some Egyptian who’s been spending ten hours a day moving stone blocks unless you’re in pretty good condition yourself.
(For those interested in one of the original questions, soory for the digression).
O.K. We have wandered off on a tangent here. I don’t want to know if I could kick an egyptians ass (or a chimps for that matter). So let me put this question another way.
You know when you go to the planetarium and stand on the scale that tells you what you would weigh on the moon or on Venus. The bigger the planet, the more you weigh right? Like for example I weighed 1,220 lbs. on Jupiter but only 65 on the moon.
So it would stand to reason that if I took a 900 lb. pyramid stone to the moon it would weigh less than 900 lbs. (also it would give the tabloids some great headlines, ANCIENT STONE WITH ALIEN ELVIS IMAGE FOUND ON THE MOON) and so on.
So I hop in my way-back machine and travel back to ancient egypt at which point the earth was smaller and gravity was lighter. Upon my arrival, I quickly befriend many stone workers and chimps. I start hanging out with a guy named Senefru and after a night of drinking together we decide to lift rocks to celebrate our new found friendship.
Now to him the rock weighs the same as it always did, but to me (future boy from the big heavy version of earth) it weighs less, right?
So here is my question… How much less?
The time difference you’re talking about is only a few thousand years-- not even an eyeblink in geological terms. The change in Earth’s mass over that time might be detectable by sensitive instruments, but you wouldn’t notice any difference.
So if you were to take a 900-pound block of stone from the present, and go back to ancient Egypt with it, you might weigh it at 899.999 pounds. I’d be surprised if the difference was even that much, but in any case you wouldn’t use it to play catch.