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We stand on a globe which is rotating around its own axis and which is orbiting the sun (that's common sense - but there are plenty of non-believers out there). Because the earth is so huge in relation to our bodies and most of our direct environment, the desks, trees, houses, mountains, rivers, etc. take on the same movement we do, we hardly realize the rotation.

We can figure out the rotation by calculations alone:

  • the earth has a diameter of some 12.700 km/7,900 mi
  • one 360° rotation takes 23 h 56 min 04 sec
  • it takes a year for one orbit around the sun
  • at the equator the speed of rotation is supersonic and at the pole it is zero.

But these numbers do not really give us a sense of movement.

Let's take a telescope, fix it to the ground and look through it straight to the sky. The Saturn stays almost still in space within this short period of time - just the telescope moves by the rotation of the earth. What we can see is this:

 

 

You need to have a telescope to be able to realize the movement.

You can view this rotation by watching moving shadows caused by moving light sources. This appears to us as a moving shadow cast by a stick fixed in position illuminated by a moving light source. I fact, however, it is the sun which is stationary and the stick, which is attached to the surface of the earth, that is moving. We can observe something like this:

It is precisely this movement that we want to show. To give you a live imagination of sundials around the world - each of them displays 12:00 L.A.T. in real time. After a few minutes automatically the live view switches to the next-westerly sundial. With enought partners worldwide you can watch sundials 24 h per day/7 days a week each showing high noon at their respective location.

As the earth rotaties we can see the virtual movement of the sun across the sky. The aim of the project Earth L.A.T. 12:00 is to visualize this movement.

The local apparent time (L.A.T.) 12:00 is defined as the time the sun appears on the local south meridian – at which point the sun is located directly above / the suns station is at its southmost point. Sundials show L.A.T. by the moving shadow.

Our goal is to produce a 24/7 live video stream of shadows crossing the 12:00 line all over the world. Every few minutes the live stream switches to the next sundial – so one can follow L.A.T. 12:00 as the earth rotates and to get a real sense of our spinning globe.

Anyone can start a sundial which is basically a stick casting a shadow on a flat surface. The hardware required to do this could be e.g. a RaspberryPI+Cam (U$ 100 + U$ 5/month for transfer costs). The system also has to be correctly set up and programmed. The images are then transferred via SFTP to the server, which automatically selects the displayed image.

To do this we need to have as many webcams as possible delivering live images of sundials. The different live images are displayed consecutively at local apparent time 12:00. That is, if no clouds get in the way. This procedure will work automatically.

With regard to the project: There is still a lot to be done!

We already have one partner sundial:
https://KEPLERUHR.eu - you can watch its livestream there or > Live-View.

 

   
© Kurt Niel

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