# Could the Eath's gravity have increased since the dinosaurs? **URL:** \ **Category:** Factual Questions\ **Created:** [August 15, 2006, 11:36pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889 "2006-08-15T23:36:23Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![beowulf573](https://avatars.discourse-cdn.com/v4/letter/b/8e7dd6/32.png) [@beowulf573](https://boards.straightdope.com/u/beowulf573)\ **Post date:** [August 16, 2006, 4:12pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/21 "2006-08-16T16:12:00Z")
There used to be a post to talk.origins, who may still be there AFAIK, who truly believe the Earth once orbited Saturn pole first. Because of the proximity to Saturn the ‘felt-effect’ of gravity was lessened and that’s why dinosaurs grew so big. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [August 16, 2006, 5:28pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/22 "2006-08-16T17:28:28Z")
> [@beowulf573](#): > > There used to be a post to talk.origins, who may still be there AFAIK, who truly believe the Earth once orbited Saturn pole first. Because of the proximity to Saturn the ‘felt-effect’ of gravity was lessened and that’s why dinosaurs grew so big. Ted Holden, IIRC. He was quite a trip. When I first saw this thread I was almost expecting to see a reference to Kaz, TH’s favorite weight lifter. ---
**Author:** ![tim314](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim314/32/3468_2.png) [@tim314](https://boards.straightdope.com/u/tim314)\ **Post date:** [August 16, 2006, 5:43pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/23 "2006-08-16T17:43:13Z")
I’ve frequently read that the reason there could be no science fiction style “giant humans” (i.e., huge but in normal proportions), is that weight scales at a different rate than strength. I.e., how much you weigh is related to your volume, so it scales with size cubed. Whereas, how strong your bones are (i.e., how much weight they can support) is related to their cross-sectional area, which scales with size squared. So if you scaled a human up to giant size, their weight would grow faster than the strength of their bones, and eventually their bones would snap. Roughly, this explains why big creatures like elephants have thick legs, and tiny creatures like spiders have little spindly legs. What does this have to do with the question asked? Well, my point is that **if you know how big an animal is, you can (roughly) predict how much it weighs, and based on that you can predict how thick its bones must be to support it.** But if gravity were weaker in the dino-age, then dinosaurs would weigh less than our size-based estimate, and they’d have smaller bones than we’d otherwise expect. So far as I know, massive dinosaurs all had appropriately thick bones, which is evidence that gravity was about the same for them as it is for us. But if we ever found a huge dinosaur with little spider legs, maybe we’d need to revisit this conclusion. (Of course, there are plenty of other reasons to think gravity is constant. But the point is, just because something’s big doesn’t mean it lives in low gravity – the relevant question is, is it big compared to its structural strength? If we ever find lifeforms on a smaller planet than ours, they might very well be big but fragile-looking.) ---
**Author:** ![saoirse](https://avatars.discourse-cdn.com/v4/letter/s/5daacb/32.png) [@saoirse](https://boards.straightdope.com/u/saoirse)\ **Post date:** [August 16, 2006, 5:48pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/24 "2006-08-16T17:48:11Z")
> [@Harmonious Discord](#): > > This is a subject that posed a question I wonder about. How much more of our gravitational attraction was nutralized by the faster rotation of the earth during the age of dinosaurs? What was the rotational period of the Earth at that time? This all became a question when reading claims that dinosaurs couldn’t have lived on the Earth, if the gravity hadn’t been less. It was rotating faster; that was closer to the least time God stuck his foot out and kicked off. When the Earth’s rotation slows down enough. He’ll stop giggling and kick off again. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [August 16, 2006, 6:16pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/25 "2006-08-16T18:16:40Z")
\*Case opens… > [@tim314](#): > > I’ve frequently read that the reason there could be no science fiction style “giant humans” (i.e., huge but in normal proportions), is that weight scales at a different rate than strength. I.e., how much you weigh is related to your volume, so it scales with size cubed. Whereas, how strong your bones are (i.e., how much weight they can support) is related to their cross-sectional area, which scales with size squared. So if you scaled a human up to giant size, their weight would grow faster than the strength of their bones, and eventually their bones would snap. Roughly, this explains why big creatures like elephants have thick legs, and tiny creatures like spiders have little spindly legs. > > What does this have to do with the question asked? Well, my point is that **if you know how big an animal is, you can (roughly) predict how much it weighs, and based on that you can predict how thick its bones must be to support it.** But if gravity were weaker in the dino-age, then dinosaurs would weigh less than our size-based estimate, and they’d have smaller bones than we’d otherwise expect. > > So far as I know, massive dinosaurs all had appropriately thick bones, which is evidence that gravity was about the same for them as it is for us. But if we ever found a huge dinosaur with little spider legs, maybe we’d need to revisit this conclusion. > > (Of course, there are plenty of other reasons to think gravity is constant. But the point is, just because something’s big doesn’t mean it lives in low gravity – the relevant question is, is it big compared to its structural strength? If we ever find lifeforms on a smaller planet than ours, they might very well be big but fragile-looking.) …case closes.\* Uhp. Case closed! Any _other_ questions?? ---
**Author:** ![beowulf573](https://avatars.discourse-cdn.com/v4/letter/b/8e7dd6/32.png) [@beowulf573](https://boards.straightdope.com/u/beowulf573)\ **Post date:** [August 16, 2006, 7:38pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/26 "2006-08-16T19:38:25Z")
> [@Telemark](#): > > Ted Holden, IIRC. He was quite a trip. When I first saw this thread I was almost expecting to see a reference to Kaz, TH’s favorite weight lifter. Yep, that’s him. I read his posts during college and they made me realize just how truely nutty some folks could be. ---
**Author:** ![Cervaise](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cervaise/32/16693_2.png) [@Cervaise](https://boards.straightdope.com/u/Cervaise)\ **Post date:** [August 16, 2006, 7:44pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/27 "2006-08-16T19:44:27Z")
> [@chorpler](#): > > Besides, everybody who’s read Robert J. Sawyer’s book [_End of an Era_](http://www.amazon.com/gp/product/0312876939/sr=1-1/qid=1155687189/ref=pd_bbs_1/104-7530769-9165522?ie=UTF8&s=books) knows why the gravity was REALLY lower. 😉 Y’know, the only problem with being a member of a smart and literate message board is that even the obscure and offbeat references are immediately taken. 😛 ---
**Author:** ![scottnic](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@scottnic](https://boards.straightdope.com/u/scottnic)\ **Post date:** [August 16, 2006, 7:58pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/28 "2006-08-16T19:58:41Z")
> [@Zsofia](#): > > How _could_ they have invented chairs? They wouldn’t even be able to use them! They had tails and stuff. They’d have to invent stools. [Looks like they did.](http://boards.straightdope.com/sdmb/showthread.php?t=383433) 😉 ---
**Author:** ![Schuyler](https://avatars.discourse-cdn.com/v4/letter/s/54ee81/32.png) [@Schuyler](https://boards.straightdope.com/u/Schuyler)\ **Post date:** [August 16, 2006, 7:59pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/29 "2006-08-16T19:59:46Z")
> [@tim314](#): > > **if you know how big an animal is, you can (roughly) predict how much it weighs, and based on that you can predict how thick its bones must be to support it.** But if gravity were weaker in the dino-age, then dinosaurs would weigh less than our size-based estimate, and they’d have smaller bones than we’d otherwise expect. You, sir (or madam) win the award for best answer. Nice job. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [August 16, 2006, 8:35pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/30 "2006-08-16T20:35:30Z")
\*Case opens… > [@tim314](#): > > I’ve frequently read that the reason there could be no science fiction style “giant humans” (i.e., huge but in normal proportions), is that weight scales at a different rate than strength. I.e., how much you weigh is related to your volume, so it scales with size cubed. Whereas, how strong your bones are (i.e., how much weight they can support) is related to their cross-sectional area, which scales with size squared. So if you scaled a human up to giant size, their weight would grow faster than the strength of their bones, and eventually their bones would snap. Roughly, this explains why big creatures like elephants have thick legs, and tiny creatures like spiders have little spindly legs. > > What does this have to do with the question asked? Well, my point is that **if you know how big an animal is, you can (roughly) predict how much it weighs, and based on that you can predict how thick its bones must be to support it.** But if gravity were weaker in the dino-age, then dinosaurs would weigh less than our size-based estimate, and they’d have smaller bones than we’d otherwise expect. > > So far as I know, massive dinosaurs all had appropriately thick bones, which is evidence that gravity was about the same for them as it is for us. But if we ever found a huge dinosaur with little spider legs, maybe we’d need to revisit this conclusion. > > (Of course, there are plenty of other reasons to think gravity is constant. But the point is, just because something’s big doesn’t mean it lives in low gravity – the relevant question is, is it big compared to its structural strength? If we ever find lifeforms on a smaller planet than ours, they might very well be big but fragile-looking.) …case closes.\* Uhp. Case closed! Any _other_ questions?? ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 17, 2006, 2:14am UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/31 "2006-08-17T02:14:45Z")
> [@tim314](#): > > So far as I know, massive dinosaurs all had appropriately thick bones, which is evidence that gravity was about the same for them as it is for us. They had appropriately thick bones where it counted, as well as having relatively [light and airy bones](http://www.psjournals.org/paleoonline/?request=get-abstract&issn=0094-8373&volume=029&issue=02&page=0243) which likely helped reduce overall weight. Ma Nature is much better at building critters than most folks give her credit for. She knows how to build 'em big without resorting to gravitational anomalies or alternate-reality physics. ---
**Author:** ![AncientHumanoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ancienthumanoid/32/278_2.png) [@AncientHumanoid](https://boards.straightdope.com/u/AncientHumanoid)\ **Post date:** [August 17, 2006, 6:21pm UTC](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889/32 "2006-08-17T18:21:53Z")
Dinosaurs invented Ikea, you know. As for the Earth gaining mass thru the eons, doesn’t it also _lose_ mass? I seem to recall reading somewhere, in my long and varied life, that Earth loses mass thru the rarification, or ionization, or some sort of \_\_\_\_tion, of atmospheric gasses, but that the accumulation of cosmic dust bunnies makes up for the loss, leading to some sort of equilibrium. True? Part true? Way off? Help me out here, Science Dudes. [Previous page](https://boards.straightdope.com/t/could-the-eaths-gravity-have-increased-since-the-dinosaurs/368889.md?page=1)