What fraction of a second per how much time? I could imagine this being part of some nerdy thought experiment with completely insignifficant result (something like "ohhhh, did you know it slows the earth rotation by a millisecond every 2 billion years?). As mentioned, I’m not sure it’s actually possible without interaction outside the frame, but rotational momentum is… more complicated than linear momentum, so it might be?
4 Likes
Beware. Google’s AI tells lies. The BBC are very upset about multiple instances of misrepresentation.
4 Likes
Yes. And trump just sealed a deal for a UAE billionaire to build AI centers all across the US. It can only get better, right… … …
3 Likes
Ah. It changing the moment of inertia makes sense, I guess. Basically would mean it’s still the moon doing the slowing down, it just has a slightly easier time of it…
0.06 microseconds per day, that would be… uhm… about 1 millisecond per 45 years? so, roughly 22.2 seconds in a million years… I have to admit, that is more than I would intuitively suspect to be possible, but I don’t know how much water we’re actually talking about. Would have to put that in relation with the earths oceans to make any kind of intuitive guess possible.
4 Likes
I imagine it’s chicken feed compared to the melting of the polar ice sheets. And it’s all happened many times before. We had all those ice ages.
4 Likes
You may not be finding anything because that is old old ‘news.’ It’s real, it’s trivial, and yeah NASA probably put out some sort of ‘warning’ just because it was a cool physics thing that gets people interested in science, at least briefly. Moving mass away from the axis of rotation slows the rotation. Technically, this is a temporary effect because if they were to open the dam and drain the reservoir (move mass towards the axis of rotation) it would speed back up.
To see a good illustration of this effect, find a park with a hanging tire with a swivel so that it spins freely (doesn’t ‘wind up the rope’). Get two good weights (gallon jugs of water work good). Sit on the tire and hold the weights straight out. Have a friend get you spinning as fast as they can, then step back. Pull your arms in close to your body. Be prepared because you are going to spin unbelievably fast. You will find that you have complete control over the spin rate just by moving your arms in or out.
As to the tides, that isn’t the same mechanism because the distribution of mass over distance from the axis of rotation remains constant (high tide here means low tide there). The tidal grind in the earth’s core converts kinetic energy into heat because of friction, and that is what slows the earth’s rotation…permanently.
Melting the polar ice caps is a relevant issue for a couple reasons. The poles by definition are at the axis of rotation. Moving mass from polar ice into tropical ocean takes it away from the axis. However, at least at the south pole, taking all that weight off is expected to lead to a lifting of Antarctica, and the entire shape of the earth could change as a result. Slightly less oblation (the ‘flattening’ of the sphere at the poles) would mean mass moving closer to the axis.
3 Likes
That explains it. Wonder why it is trending again…
Dancers, particularly ice dancers, frequently make use of this effect. They spin on point, then control their speed of rotation by stretching out or pulling in their arms.
4 Likes
Yeah. That’s a great way to see it. The tire is a way to experience it. I showed that to my kids, and thirty years later it’s one of the science lessons they remember best.
3 Likes
Probably one of the articles about research done on Earthquake effects. In this 2005 article, it uses the Three Gorges dam as a comparison for shift of it’s mass of water it holds.
3 Likes
New Glenn - NG-1 (Maiden Flight)
Planned for launch coming Sunday, January 12th, 2025 at 06:00 UTC.
Update: Rescheduled 3hr launch window Monday, January 13th, 2025 at 6:00 UTC
Starship - Flight Test 7
Planned for launch coming Monday, January 13th, 2025. Launch window from 22:00 UTC.
Falcon 9, Kennedy Space Center (39A), Florida
Two payloads are planned for launch coming Wednesday, January 15th, 2025 at 06:11 UTC.
- Primary: Ghost Riders in the Sky
Firefly Aerospace’s Blue Ghost lunar lander
- Secondary: Hakuto-R Mission 2
Resilience lander and Tenacious rover
4 Likes
5 Likes
I have been watching this story and I wonder how long it will take to determine who it belongs to.
Imagine if all the debris up there fell at once…
3 Likes
As it happened, it’s a curiosity that made a dent in a farmer’s field. But that thing is a substantial chunk of steel. Imagine if it had hit a Nairobi office block during business hours - it could have killed hundreds - and it’s pure chance that it didn’t.
3 Likes
2 Likes
Now moved to wednesday.
4 Likes
New Glenn scrubbed after 3 hours. Issues with the subsystem taking too long to allow for a launch within the window.
Update:
We’re moving our NG-1 launch to no earlier than Thursday, January 16. The three-hour launch window opens at 1 a.m. EST (0600 UTC).
Source 
4 Likes
Videos from today’s Falcon 9 payloads below:
Firefly Blue Ghost
iSpace Hakuto-R
Note: Naoko Yamazaki was wearing her 2004 jacket with patches of Astronaut Group 19 (class 2004 see image below) and STS-131 (final Space Shuttle Discovery mission)
2 Likes
6 Likes