Friday, June 3, 2011

Spinning Round and Round

Although the world seems flat, most of us know it ain't flat. Our senses create an illusion of flatness that's not there.

In a very similar way, the sun appears to climb up over the horizon at dawn and sink under the western horizon at sunset. It just ain't so.

When we understand that the earth spins on its axis we can begin to see that the sun is comparatively motionless in the sky. We're simply sitting on a little ball that spins us round eastwardly at about 1,000 miles per hour.  If we could hop on a plane flying east at 1,000 miles per hour,  the sun would stay approximately motionless in the sky. Geosynchronous satellites do this trick up in space.

This is hard to describe, but easy to see in this video clip that appeared on the NASA apod site the other day.



Earth Rotating Under Very Large Telescopes 
CreditS. Guisard & Jose Francisco SalgadoESOBulletpeople.comMusic: Arcadia (License: Kevin Macleod)
Explanation: Why is the Earth moving in the above video? Most time lapse videos of the night sky show the stars and sky moving above a steady Earth. Here, however, the frames have been digitally rotated so that it is the stars that stay (approximately) steady, and the Earth that moves beneath them. The video dramatically shows the actual rotation of the Earth, called diurnal motion, in a clear and moving way, as if the camera were floating free in space. The telescopes featured in the video are the Very Large Telescopes (VLT) in Chile, a group of four of the largest optical telescopes deployed anywhere in the world. A discerning observer of the above time lapse movie may also note the use of laser guide starszodiacal light, the Large and Small Magellanic Clouds, and fast-moving, sunlight-reflecting, Earth-orbiting satellites. The original video, on which the above sequences are based, can be found here.


neighbor said...

nice video :) I like the off-balance feeling it gives to the earth while the cosmos is stable out there.

I was wondering where your sidebar links went to... I sometimes like to click on your other blogger-friends' links and hadn't bothered to bookmark them myself... oops!

Dan Gurney said...

Hi, neighbor, thanks, I enjoyed it, too. It showed so clearly something I have had some difficulty describing.

I removed the sidebar links for several reasons. But an important reason was because I have begun to use Google Reader to keep up with blogs I follow. I want to cut down on my blogging time and concentrate on reading fewer blogs than I have.

Sabio Lantz said...

That was fun.

Dan Gurney said...

I wonder, Sabio, do you have the sensation of standing on a big ball rolling eastward when you see a sunrise? Or does the illusion of the sun climbing up in the sky hold?

neighbor said...

ah, too bad. I mean, good for reducing blogging time if it was becoming too much, but too bad for me :) I also appreciated that sometimes I'd get readers directed my way by your link.

Hope summer promises lots of fun things and good, easy time off. If there are any poetry events in Sebastopol, let me know, maybe we can meet in real life before I move...

Dan Gurney said...

Yes, I need to go on a blogging diet. It would be fun to meet in real life. If you ever come to Sebastpol, email me.

paula devi said...

thank you. It was fun and amazing at the same time. what tiny specs we are.

Dan Gurney said...

Hi, Paula, you are welcome. I am glad you enjoyed the video clip. We can seem insignificantly tiny or just huge depending on what we compare ourselves to. From the point of view of a virus, we are immense; from the point of view of a planet, we are pretty small. It mostly feels to me that we are in between.