The Moon Illusion

As mentioned in the previous post, had you been watching the Lunar Eclipse along a flat, clear horizon, you may have seen the eclipsed Moon at the same time as the eclipsed Sun.  This is phenomenon that rarely occurs.  How is it possible though?  It has to do with the Earth’s air acting as a lens and bending the light of the Moon, to make it look as if the Moon were still over the horizon even after it has physically set.  And how is it that this is possible?  It seems to relate to the perceived inflation of the Moon as it sets in the sky.

The perception that the Moon inflates as it is setting in the sky is known as the Moon Illusion.  I credit Phil Plait for the information I am going to summarize concerning this illusion.  He thoroughly describes the Moon Illusion in one of his many posts concerning space on his blog Bad Astronomy.

The Moon Illusion is closely related to the Ponzo Illusion.  Such an illusion occurs when an object of equal size of another object is perceived to be farther than the second object and is thus assumed to be larger in size.  The “farther” object then actually looks larger in size compared to the second object.  The following images are simple examples of the Ponzo Illusion:

Notice how the top yellow bar in the left image appears to be larger in size than the bottom bar, and how the block furthest to the right in the right image appears to be taller than the other two blocks.  This is due to the human brain’s perception of those objects being farther than the others, and are thus thought and seen to be larger.

The Moon Illusion is in part due to this same effect, but it is also our perception of the sky that creates this illusion.  Though most people describe the sky above their head to be in the shape of a hemisphere, nearly everyone perceives the sky as an inverted bowl that is flat at the top.  Because of this perception, the horizon looks to be farther than any point above our heads.  When the Moon is on the horizon, your brain thinks it is far away, much farther away than when it’s overhead, and so the Ponzo Illusion kicks in and your brain sees the Moon as being huge.

Oddly, the Moon is indeed farther along the horizon than than when it’s overhead.  Such a fact is illustrated by the following image (image credit: Phil Plait):

Evidently, it seems the perception that the Moon is farther along the horizon than when it is overhead is true and not an illusion.  The illusion is that the Moon appears to be larger in size along the horizon than when it is overhead.  I understand what causes this illusion, but the reason of how/why our brains see the Moon “inflating” as it sets in the sky escapes me.  It is our brains’ deceitful perceptions that are the main causes for this illusion.

Saturday’s Lunar Eclipse

(image credit: Phil Plait)

This previous Saturday a Lunar Eclipse occurred in the early hours of the morning; the Moon passed into the Earth’s shadow and plunged into the ruddy darkness.  During the time period between 0445 hours and 0606 hours Pacific time, the Moon had completely slipped behind the deepest part of the Earth’s shadow.  The deepest eclipse was approximately 25 minutes after the Moon had completely moved into the shadow of the Earth.

For those of you with a flat, clear horizon, you may have had the opportunity to witness the eclipse of both the Sun and the Moon.  Normally such an event is not possible because by definition an eclipse occurs when the Moon and the Sun are directly opposite each other.  However, due to a quirk in geometry and atmospheric physics, such an event is possible.  (The following information I learned from a Bad Astronomy blog post) The Earth’s air is able to bend the light of objects at the horizon because it acts as a lens.  Because of this effect, you can see the moon for a couple of minutes after it has physically set; “its light is bent ‘around the corner’, so to speak, so both it and the Sun will be over the horizon for a short amount of time.”

Here is the link to a time-lapse video shot in Santa Fe, New Mexico of the Lunar Eclipse over Los Alamos, New Mexico:  What an amazing sight to see.

Boeing Update

While reading through the blog posts of a Boeing blog I follow, I read a blog concerning recent news.  This previous Thursday 01 Dec 2011, the first Boeing 787 Dreamliner, ZA001, was decommissioned after flying from Seattle’s Boeing Field to Palmdale, CA.  This was nearly 2 years after its delayed maiden flight.  In a report by Flightblogger, the Rolls-Royce Trent 1000 engines will be removed and the aircraft will be placed in storage until it finds a place in a museum.

So why did Boeing decide to decommission the 787 Dreamliner?  Unfortunately, I could not really find information other than that disclosed on the blog post, and there was not that much information on the blog post.  According to EETimes, the first flight of the 787 Dreamliner was delayed 6 months in Jun 2009, announcing it needed to reinforce the areas where the wings met the side of the aircraft.  Also, the reworking of the planes destroyed their commercial values, which clearly resulted in a decline in commercial profit.  So, from what I have read and presented to you, it seems that the 787 Dreamliner brought some economic and technological hardship to Boeing.  I guess that is why Boeing decided to ultimately decommission the 787 Dreamliner.

Why Retire the Space Shuttle Programs?

For this post, I want to discuss the reasons the government decided to retire the Space Shuttle programs.  From the information I was able to gather, it seems that two large factors leading to the retirement of the Space Shuttles involved economic and technological disadvantages.  The two historical failures of the Space Shuttles (the Challenger and the Columbia tragedies) did not help the help the case of keeping them around either.

The Challenger

28 Jan 1986, the Space Shuttle Challenger exploded 73 seconds after lift-off, resulting in the deaths of 7 crew members.  The cause of this failure was the malfunction of an O-ring in the right solid rocket booster of the shuttle.  This resulted in a breach in the solid rocket booster joint it sealed, which allowed pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent solid rocket booster attachment hardware and external fuel tank. This led to the separation of the right-hand solid rocket booster’s aft attachment.  In summary, all this led to the structural failure of the external tank.

The Columbia

01 Feb 2003, the Space Shuttle Columbia disintegrated shortly before it was scheduled to complete its 28th mission, killing the seven astronauts who made up its crew.  The failure of the Columbia was a result of damage sustained during launch.  A piece of foam insulation the size of a small briefcase broke off from the Space Shuttle external tank under the aerodynamic forces of launch. The debris struck the leading edge of the left wing, damaging the Shuttle’s thermal protection system and leaving it vulnerable to the intense heat generated from atmospheric friction.

Economic Disadvantages

Though the initial goal for the Space Shuttle programs was to provide access to space as a routine and inexpensive activity, access to space remained (and still remains) a highly expensive and highly inflexible activity.  The price to launch a payload aboard the Space Shuttle is still $10,000 per pound, a figure that has not gone down in over a decade.  It is the versatility of the Space Shuttles and their ability to perform multiple roles that made them so expensive.

Technological Disadvantages

NASA has always regarded crew safety as its number 1 priority; however, a long-standing drawback to the Space Shuttles was the crew escape system.  The requirements for the 2nd generation Reusable Launch Vehicle were a 1 in 1000 Loss of Vehicle and a 1 in 10000 Loss of Crew over the entire flight profile, which implied a 90 percent confidence in the Crew Escape system.  Unfortunately, the technology of the Space Shuttles only generated a 75 to 80 percent confidence in the system according to the data of the Naval Aviation Center.  The Crew Escape system only operated when the shuttle is in a controlled gliding flight after reentry and is unable to reach a runway.  It was thought to be pointless to pursue further advancements in an aging technology when the cost of these begins approaching the cost of developing a replacement for the whole system.

The J-2X Engine

I thought this week I ought to describe to you the new engine which will be used for human travel in space.  The J-2X engine is a variation of the J-2T engine, which was a variation of the J-2S engine.  NASA began construction of the engine in 2007 at the Stennis Space Center.  Nine test of the heritage J-2 engine components were conducted in preparation for the design of the J-2X engine.  The J-2X was chosen for the Project Constellation manned lunar landing program.  Though the project was cancelled by the President, development of the J-2X has continued for its potential as the second stage engine for the heavy-lift Space Launch System.

Analysis of Discourse Material

I have decided to momentarily break off from my usual agenda of informative material, and have decided this week to analyze some blog material I read.  One of the blogs I follow, Bad Astronomy, wrote a post concerning a meteor which will pass the Earth on its orbital path on 08 Nov 2011 (“A city-block-sized asteroid will swing by Earth on November 8“).

The blog post talks about an asteroid which will pass the Earth on November 8.  This asteroid will pass on its orbital path 320000 kilometers from the Earth.  Though the asteroid is not dangerous, in the sense that it could potentially strike the Earth, it has still been labeled a Potentially Hazardous Asteroid because its orbit is the same as Earth’s.  Because it has been labeled as such, astronomers will be observing the asteroid.

The blog post is an interesting read.  The voice is informal in order to form a better connection with the readers.  It uses different medias which are visually engaging, and it uses hyperlinks in order to connect with outside resources, which further validate the information in the blog.  It is clearly a well written because there have been multiple views and numerous comments to the blog post.

What Now?

Now that the space shuttle programs have been terminated, what is there left for NASA to do?  With no more space shuttles, will we no longer be able to explore space?  Was space travel not the main mission of NASA?  According to the NASA website, the ending of the shuttle programs is not at all necessarily a bad thing.  It is not the end of NASA or even human space travel.  “NASA has a robust program of exploration, technology development and scientific research that will last for years to come,” (What’s Next For NASA?).

So what really is next for NASA?  NASA is going to be continuing work in the following areas:

  • exploration- NASA is working on developing a new flight vehicle (Space Launch System rocket) to transport humans beyond the orbit of Earth.  Engineers are also working to construct other technologies necessary for human exploration, such as solar electric propulsion, refueling depots in orbit, radiation protection, and high-reliability life support systems.
  • International Space Station- It is the centerpiece of human flight in low Earth orbit.  The International Space Station acts as an experimental station for exploration technologies and as a national laboratory, where crew members have committed to scientific research.
  • aeronautics- NASA is researching methods of constructing aircraft which is safer, more efficient, quieter, and environmentally responsible.  They are working to create traffic management systems that are safer, more efficient, and more flexible.  Technology is being developed to improve routing during flights and to give aircraft the ability to climb to and descend from their cruising altitudes with ease.  NASA promises to continue to validate new, complex aircraft and air traffic control systems to ensure they meet extremely high safety levels.
  • science- NASA is conducting missions that will seek new knowledge and understanding of Earth, the solar system, and the universe.  NASA’s science vision encompasses questions that are all practical, enticing, and profound.