Shortening the day

[pierhogunn]

okay, time for some fun with math and physics

Driving is always a dangerous time, and this last trip was no exception

Here are my questions

How much thrust would it take to change the rotational velocity of the planet

Where would be the best place to put thrusters capable of doing such a hair-brained thing

What would happen if we slowed the planets rotation down

What would happen if we sped the planets rotation up
1. Would we feel less gravity because of the change in our angular momentum? or centripital force slinging us off the planet
2. Would things weigh less?
3. Would a shorter day screw things up...


I know that with current technology this isn't possible, but what if...

[pacwind3]

After giving the above questions some serious thought, I decided: I have no idea.

It did make me wonder what would happen if we did it to the moon.
For the first time, we'd all be able to see the dark side for starters. Maybe humans should consider it to change the view.

[steve-norrell]

Shorten the day?

The population already goes into a dark mourning when the days start getting shorter after June 21 and things don't begin to lighten up until December 21 when the days begin to get longer again. SAD (Seasonal Affective Disorder, aka "Cabin Fever") in winter is a sad, sad thing to see. (Puns intended.)

If you talked about shortening the day during certain times of the year you would incur serious risk in some circles of the Great Land.

Now how about changing the tilt of the earth so the days don't get so short?

Regards, Steve

[docrowan]

Shorten the day?

Now how about changing the tilt of the earth so the days don't get so short?

Regards, Steve

Here, here! Although I went to Costa Rica one time (very near the equator) and it felt sooo wrong for it to be dark by 6:00 in the evening during the summer. Hate the long nights in the winter, but love the long days in the summer.

[BobSch]

How much thrust would it take to change the rotational velocity of the planet

By how much? If you want to get all metaphysical about it, a sneeze will slow down or speed up the Earth. But I defy anyone to measure by how much!

[Hoakie]

I will defer to LCHIEN to do the analysis first. If he makes a mistake I'll correct him

[LCHIEN]

I let Wikipedia do this work for me:

As an example, let us calculate the rotational kinetic energy of the Earth. As the Earth has a period of about 23.93 hours, it has an angular velocity of 7.29×10-5 rad·s-1. Assuming that the Earth is perfectly spherical and uniform in mass density, it has a moment of inertia, I = 9.72×1037 kg·m2. Therefore, it has a rotational kinetic energy of 2.58e+29 J.

converting joules to ft-lbs, 1.9e+29
Now a 747-400 jet engine produces 63,300 lbs thrust
the earths dia at the equator where we need to apply force is 7926 mi
converting for ft, etc the force applied by a 4-engined 747 firmly anchored to the earth and pointed due west would be an impressive 1.06e+13 ft lbs.


So you only need 17,899,999,999,999,999,999 more 747s tied to the earth and running at 100% thrust to bring it to a stop.

If you just wanted to slow it you could use a fraction of that fleet. For instance, slowing it 1 minute per day would only take 12.4 trillion 747's.

The force must be applied at the equator in the west direction (to slow it) or you'll just make it spin on some other axis. That's also where you get the most leverage.

Actually the day is gettling longer due to the friction of the tides sloshing. Each day is getting 1.7 milliseconds longer every 100 years. That may not seem like much but its a lot of nanoseconds!

[pacwind3]

uuhh, ok. What's a: joules ?

[pierhogunn]

I'm sure boeing would love to get that contract

what about speeding up the rotation of the earth, say by 2X ?

[docrowan]

I'm sure boeing would love to get that contract

what about speeding up the rotation of the earth, say by 2X ?

Easy - point them all east!

[LCHIEN]

uuhh, ok. What's a: joules ?

metric unit of energy

[crokett]

uuhh, ok. What's a: joules ?

A guy I used to work with. He is French-Canadian.

[cabinetman]

You don't need no jet engines. This guy can do it.
.

http://www.squibkick.com/wp-content/...0/superman.jpg
.

[pacwind3]

metric unit of energy

I thought it was just under the lower jaw on a pig.
Learn something new everyday.

[poolhound]

2. Would things weigh less?

Yes we would weigh less with less gravity (according to currently calibrated scales) so lets get a bunch of 747s going and I could drop that 10 lbs

Unfortunatley our mass would remain the same so I guess its back to diet and exercise