You Must Obey The Speed Limit
The universe has a speed limit. In a vacuum, the fastest anything can travel is 299,792,458 meters/second. This speed limit applies to all electro-magnetic E-M waves which includes radio, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.
In subsequent posts, I will describe some of the attempts to measure this incredible speed throughout history. For this post, I will describe some of the earliest ideas people had about light and whether it had a measurable speed. I hope you will join in.
I’m interested. Show me more.
The previous post explained the nature of a total lunar eclipse and what to watch for. The post also described the four consecutive total lunar eclipses we can expect in the next two years, known as a tetrad.
I set the alarm for 2 am. Total eclipse was to begin for my location in eastern Iowa at 2:08 CDT. The camera settings were made the night before. It was already on the tripod. Images were from my front lawn.
For the photographers:
- Fuji FinePix S602 ZOOM at 6x
- ISO 200
- White Balance set to incandescent
- Exposure 2 seconds using the self-timer mode to avoid shake
- Focal Length 47 mm
- White level was set in each of the next four images using the star Spica at lower right
This diagram shows the path of the Moon across the penumbra and umbra of the Earth’s shadow. Times are for the eastern time zone. Times for my images are for central time zone.
© Sky & Telescope
2:09:03 am CDT
About 1 minute after total eclipse started. Note the bright region on the lower right limb of the Moon which was last bathed in direct sunlight moments before.
2:17:52 am CDT
Almost 9 minutes into totality. The lower right limb is a bit less bright.
2:27:52 am CDT
Now nearly 20 minutes into totality. The Moon is showing some signs of redness. It is more evenly illuminated and slightly dimmer.
2:28:53 am CDT
At 21 minutes into totality, I changed the white balance on the camera to shooting outdoors in shade. I was curious what difference it would make in the blood color. Incandescent tends to give better blue tones for star photography. This change did enhance the reds.
While I waited for the Moon to progress through the umbra, I looked around the sky. It was perfectly clear. Almost overhead was Ursa Major, the Big Dipper. Scorpius was peeking over some rooftops as it traversed the south sky. Mars was to the upper right of the Moon and Spica. At this time, Earth and Mars are at their closest as we pass the red planet in our closer and faster orbit. Here is an animation from my planetarium software.
I turned the camera slightly and zoomed out a little to include Mars and the Moon in one image.
Moon – Spica – Mars
If you missed the show this time, North America and the Pacific will get the second total lunar eclipse in the tetrad October 8, 2014.
Joel 2:31: “The sun shall be turned into darkness, and the moon into blood, before the great and the terrible day of the LORD comes.”
That is an ominous sounding excerpt from the bible. Does it have anything to do with the coming lunar eclipse early in the morning of April 15, 2014? The Moon will probably appear red during the totality part of the eclipse. That is about the only thing. Don’t worry about an impending apocalypse. So, why is this lunar eclipse drawing special attention?
What is a Lunar Eclipse?
These occur when the full Moon passes through the shadow of the Earth. It happens on average a couple of times a year. Earth is positioned between the Sun and the Moon. This brief 2 minute video from the folks at the Goddard Space Flight Center will illustrate the mechanics of a lunar eclipse.
As you may have noticed, the Sun is not turned to darkness during a lunar eclipse, at least for us on Earth.
Why is this such a big deal? Tell me more.
The previous post Big Telescopes | Examples of Three Types, describes the refractor, Newtonian reflector, and Cassegrain reflector. Of these, the Cassegrain design is built into the largest diameter and most powerful telescopes in the world. In this post, I focus on the process used to form the mirrors of the Giant Magellan Telescope scheduled for completion in 2019. Each mirror is 8.4 meters across. Those seven mirrors will form a telescope objective of 24.5 meters, or 80 feet. Note the human figure at the lower left in this artistic rendering.
GMTO Corporation 251 S. Lake Avenue, Suite 300 Pasadena, CA
The mirrors need to be as light as possible. They cannot be made of a thick piece of solid glass. Instead, they are built in a honeycomb hollowed out structure. It is a remarkable story of engineering and technology.
This four minute video from the Univ. of AZ Mirror Lab explains some of the rationale for this telescope and the large mirrors being cast for it. More details are found below.
Show me how it is done.