Sunday, February 26, 2012

The Moon, Venus and Jupiter

Today (26-Feb-2012) The Moon was between Venus and Jupiter. The distance between them is still large enough so we will not call this setup a conjunction but rather an alignment. Nonetheless, it was very nice to see all three celestial bodies close together (They will look much closer next month!)
The first photo still in twilight, Venus at the bottom and Jupiter at the top.
The moon, Venus and Jupiter
The moon, Venus and Jupiter
 The second is just a closeup of the crescent moon
The Moon 4.5 Days old
The Moon 4.5 Days old
And the third photo will show all three bodies again with some earthly background
The moon, Venus and Jupiter
The moon, Venus and Jupiter



Thursday, February 23, 2012

New Moon

Tonight (23 Feb 2012) It was the first opportunity to see the new moon of Adar. The Hebrew calendar is a lunar calendar and the beginning of each month is decided by the moon. For the last 1600 years the calendar is calculated but before that, it was necessary to see the new moon, and to testify about it. Today, it is just nice to see the new moon each month. This month it was quiet easy, but sometime it is a real challenge.
As a bonus Mercury was near the new moon, but very hard to see. You can see it easily in the photo tough. Mercury is below and to the left of the moon. Also look how noticeable is the Earth-shine, making us see the entire moon. Rays from the sun are reflected from Earth, to the entire near  side of the moon and reflected back to US. For this reason we see the entire moon, and even some details.



Take a look at the video started from 17:38, just minutes after sunset and still in daylight. As it gets later, the moon sets, more lights are on in the far buildings. Finally the moon vanishes before it sets below the horizon. The video is from 17:38 until 19:00. I am sorry for the video degradation. If you know better ways to make a video out of many individual photos please share as comments, and I will remake it.



Tuesday, February 21, 2012

Carnival of Space

The Carnival of Space is a community of interest blog carnival bringing together the best and brightest Astronomy & Space Blogs at a single point in space and time (commonly referred to as a web address) each week.

This week Carnival of space is hosted by  Christopher Crockett and is full of astronomical news and articles.



Previous Carnival of space:


Week 255 was hosted by Vintage Space

Week 253 was hosted by Next Big future

Week 252 was hosted by the Venus transit me

Week 251 was hosted by Chandra blog


Week 250 was hosted by Vintage Space

Week 249 was hosted by Riding with robots

Week 248 was hosted by  Dear Astronomer

Week 247 was hosted by  Next Big Future

Week 246 was hosted by Links through space

Week 245 was hosted by Vintage Space

Week 244 was hosted by Next Big Future

Week 243 was hosted by me

Week 242 Was hosted by  Dear Astronomer

Week 241 was hosted by StarryCritters

Week 240 was hosted by links through space

Week 239 was hosted by Vintage Space

Week 238 was hosted by  Next big future

Week 237 was hosted by Universe Today

Week 236 -  was hosted by Peter Lake at the AstroSwanny blog

Monday, February 20, 2012

ISS and Orion

The ISS is the brightest unnatural objects in the skies, brighter even than Jupiter, and in rare occasions even from Venus. You can compere its brightness to the well known constellation of Orion. The photo is from 2008 and since than the ISS got bigger so it is even brighter!
The ISS and Orion

Additional ISS articles


London bookshops

Every time that I am in London (Which doesn't happen often enough) I spent some time at London's bookshops. There are plenty of bookshops in London with huge variety, on many subjects. Books exist on any subjects but I look first for interesting second hand astronomy books in bargain prices.


The largest shop in London (and maybe in the entire world) is Foyles located at the center of London and open till 22:00 or eve 23:00. There are books on any subject, but there are only new books there so the prices are high. I came there mostly to look.

Some of the astronomy book at Foyles
A huge bookshop with lots of second hands and bargain books is Waterstone. There are many small brancehs, but you need to go to the main branch at Gower street. You can spend some hours there browsing between new books, bargain books and second hand books

astronomy books
Astronomy shelves at Waterstone
In my last visit I stayed at Bloomsbury area which has many fine bookshops. most of them will give additional discount to students. Skoob is a great shop (which holds just a bit of the stock) with the books are arranged more or less by subjects, and like many second hand bookshops you need to check them one by one. I got there with some great books such as Spring it Forward: The Annual Madness of Daylight Saving Timeastronomy books which deals with the daylight saving time.

Not very far is Judd Books which does not have a huge selection of science book and yet I found Earthrise which deals with the first photos of Earth from space. Of course, the famous British library is nearby at Euston street. Seven floors with undergrounds warehouses and 14 Million books. Must visit. Just opposite it two interesting bookshops. In the first the maximum price is 2 pounds and the second has many other cheap books.

This is a very small selection. The Guardian newspaper has an article with a longer list, you would like to print it for your next trip to London. Enjoy your reading.



Thursday, February 16, 2012

Visual Feedback

A feedback is when the output of the process become its input. When giving feedback to someone we expect him to use the feedback and change something according to it. In the following example of visual feedback, a camera is photographing a TV screen which broadcast what the camera photographs. This create an infinite closed loop with very strange results. Notice the colors, the patterns, the repetitions, the multiple clocks changing one after another. I even manage to create a galaxy shaped figure after zooming and tilting the camera. It felts like being a choreograph .
Another known example of the feedback effect is when a microphone is too close to the speaker creating an audio loop which ends in a very loud noise. this is the reason I left only the visual channel and removed the audio channel. But the amplification exists in the visual film as well, as the center of the photo get whiter and whiter.



If you are a teacher, you can repeat this little experiment in class. The kids will love it for sure.







Tuesday, February 14, 2012

Earth from Space

How the Earth looks from space? Until recently no one could see the earth from space. Although it was known for many years that the earth is round, It was not possible to reach the requires heights to see it. Surprisingly you do not need to go far to see the curve of Earth. Twenty kilometers (14 Miles) upward will be enough, but regular airlines never reach this high, and only few army jet pilots ever reached so high.
In this page I will present many photos of Earth from space:

GOES-16 is the first of a new generation satellite which will monitor Earth from GEO (geostationary orbit, like communication satellite). Their height is around 36000km which is high enough to see the entire Earth. The satellite launch was in November 2016 and the first images are from January 2017. Here is a sample of two images.
The first is a selfie on the Earth and moon. The moon looks more or less as it is from Earth but the Earth as a background is unique
GOES-16 Earth and moon. Credit: NOAA/NASA
GOES-16 Earth and moon. Credit: NOAA/NASA
The second ones shows both Americas
GOES-16 Earth  . Credit: NOAA/NASA
GOES-16 Earth  . Credit: NOAA/NASA
More of the first GOES-16 photos are here.


MRO mission is orbiting Mars and from time to time needs to calibrate its HiRise camera. The best object to perform this calibration is the moon. The next photo shows Earth and moon together. there are many details and Australia, aAntarcticaand southeast Asia are clearly seen. this is a composite image, but the scale between the Earth and the moon sizes and distance is kept. Photos were taken on Novemeber 20th, 2016.
Earth and moon from MARS. MRO NASA/JPL-CALTECH/UNIV. OF ARIZONA 20/11/2016


LRO mission is flying above the moon mapping it in high resolution. but the scientist decided to turn its camera to Earth and got that results! The photo was taken during October 2015, when the Earth was fully illuminated frrom the moon. You can even see Israel at the top left!
Earth frrom moon.
The Earth from the moon. LRO 10/2015. Nasa
Taking this photo was not simple at all. It is made of many seperate photo and required complex maneuvers of the spacecraft and lots of image processing. the result is stunning. Read more about this picture in UniverseToday.

Hayabusa 2 is a Japanese mission to sample an asteroid and return the sample to Earth for further analysis. This will take sometime and after a year in space (The launch was at Dec-2014) the spaceship returns to a flyby around Earth to accelerate toward its target, and not missing the opportunity to take a photo (26-Nov-2015) of the Earth and the moon from 3,000,000 KM.

Earth and moon - Hayabusa2
Earth and moon - Hayabusa2 26-Nov-2015. Jaxa




The latest photo from  July 2015 will become common. DSCOVR spaceship is in special orbit and will photograph he entire lit Earth every two hours. One of the first published photos shows earth and the far side of the moon together. Read more about this magnification photo in a dedicated article.

Earth and moon. DSCOVR. NASA
Earth and moon. DSCOVR. NASA

The following photo is from October 2014 taken by the Chinese Chang'e 5 T1 mission. It is an interesting photo showing a large moon and small earth. Obviously. most of the moon surface is from the far side, never seen from Earth,
Earth and moon from Chinese Chang'e 5 TI mission. Credit: Chinese space agency


The next video from NASA MESSENGER spaceship which orbit Mercury showing a complete lunar eclipse from a very unusual point of view. Nothing less than amazing.


An interesting photo is from the surface of Mars. The rover Opportunity took this photo 80 minutes after local sunset on January 31st, 2014. Clean your screen from dust and enlarge the photo to see tiny earth. The zoom-in section shows that the moon also appears in the photo.
Earth from Mars
Earth from Mars. Source: NASA/JPL/CALTECH


The next photos are from Juno mission to Jupiter. Juno fly by Earth on October 2013 to get just one last gravity assistance in the long way to Jupiter and took some photos of the earth and the moon. NASA made a video from it. Watch and listen.

The following is a mosaic of all photos.
A mosaic of images of the Earth and Moon taken by the incoming Juno spacecraft as it flew past Earth in October 2013.
A mosaic of images of the Earth and Moon taken by the incoming Juno spacecraft as it flew past Earth in October 2013. Credit: NASA/JPL

This is nothing less than stunning. You can see how the moon orbit the Earth, the Earth rotation around its axis and how they both gets bigger. Juno's mission is not started and we get so much from it already! There is another photo from Juno below with links to articles about the missions so continue reading.


Lets move on to the newest two pictures of earth from space by NASA satellite Suomi NPP which was launched not long ago, and sent back these two picture of earth from space

Space from Earth - Americas. Credit:NASA

This photo can (and shall) be compared to the famous blue marble picture of Apollo 17. Personally I like the old soft photo, as the new photo seems to sharp and digital. Compare for yourself later at this article.
Space from Earth - Africa and Middle east . Credit:NASA

However, the more interesting photos are not from Low Earth Orbit, but from spaceship far far away on wither sides of the earth (Close to the Sun or at the edge of the solar system). Let's start with a recent photo.
Juno mission to Jupiter was launched at August 5th 2011, Just 3 weeks after the launch, Juno turned back and photographed Earth and the moon. While it is a simple photo of lots of black and two dots, this photo is very interesting. It is clearly seen that the moon is darker than Earth (Check the article about the moon brightness). Earth is covered with clouds and water which are more reflective than the dark soil of the moon. Also, it is very easy to compare the size of the Earth and the moon. If all you see in the pictures are two dots on a black background, please think again.

כדור הארץ מהחלל כפי שצולם על ידי חללית יונו ממרחק עשרה מיליון קילומטרים
Earth and Moon from space. Credit: NASA

One of the most famous pictures of earth from space is from Apollo 8 mission. The astronauts of this mission were the first to saw the far side of the Moon with their own eyes, and they submitted the famous "Earthrise" photo. Before that, and on the way to the moon they photographed the Earth. It was the first time that the whole earth was photographed from space. The astronaut who photographed it was probably Bill (William) Anders, who flight to space only in this mission

First picture of the whole earth - Apollo 8 Credit: NASA
This is the less famous Earthrise photo, just in the moment of rising.
Earth-rise - Apollo 8 Credit: NASA

And this is the more famous photo. Judge for yourself which you like more.
Earthrise - Apollo 8 Credit: NASA

However, Apollo 8 was not the first to photograph  Earthrise, an unmanned mission, Luna orbiter, did it in 1966, In black and White poor resolution.
The first earthrise photo.  LUNA ORBITER. Credit: NASA
 As you probably notice, Earth has phases just like the moon, depending on their angle from the sun. the first photo of the Full earth was captured by the last of Apollo missions, Apollo 17, and was nicknamed "The blue marble"
The full earth from space - The Blue Marble - Apollo 17. Credit: NASA
During 2003, Mars was quite close to Earth (Just 55 Million km). It was a great opportunity to observe Mars, but it was also a chance to photo the Earth from Mars. Mars Global Surveyor took this amazing photo of the Earth and the Moon.


The Earth and the Moon from Mars. Credit: JPL MARS GLOBAL SURVEYOR NASA

Another very famous photo is the "pale blue dot". It is an amazing photo because it give you proportions about us, the earth and the size of the universe. Our planet is merely one pixel in this photo taken by Voyager 1 from 6.4 Billion km (4 Billion miles).

Earth from Saturn! The earth is a pale blue dot in one of the white stripes (at the right side of the photo). Taken by Voyager 1. Credit: NASA.
Cassini is orbiting Saturn sending amazing pictures day after day. This is a photo showing Earth through the rings of Saturn. Please enlarge the photo and see Earth as a little dot at the left side of the rings.
The earth through Saturn rings. Cassini. Credit: NASA
Next photos are from the Rosetta which is on its way to visit some asteroids in 2014. Its trajectory was designed to save energy and it included an approach to earth, on which the following sequence was taken.

Earth from Rosetta. Credit: ESA


The last photo is from Mercury. Messenger mission took this photo in August 2012 from 183 Million km (115 Million miles) and capture The Earth and the moon as a double star (Binary star) in the sky.

Earth and moon photographed by MESSENGER. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Sunday, February 12, 2012

Moon Perigee

My impressions from the last (2012-05-05) are in the following article

The moon orbit around earth is quite ecliptic and the moon distance can vary a lot within a lunar month. At perigee, which is the nearest point in its orbit to Earth, the distance is about 367,000 Km. The point of greatest distance is called apogee and it was more or less 402,00Km . The perigee and apogee points' distances change each month and the minimal perigee is 356,000 Km while the maximal apogee is 406,000Km. Again, the cause for the distance difference is the moon orbit which is not circle but, like all other orbs, elliptical.
This distance's difference make the moon looks slightly bigger in its perigee. However it is very hard to notice this difference with the naked eye. The perigee and apogee point are in different moon phases, and there is no easy way to compare them, but taking photos and put them side by side. 
Even that is not so simple. The moon is in different phase, and in different angle. The best option is to wait until a full moon apogee and a full moon perigee. Patience is needed but the result will be better as demonstrated by Anthony Ayiomamitis photo  which shows the difference very well.
Here are two photos from February 2012. The moon at perigee (the right photo) and the moon 10 days before it (A little after its apogee). Can you see the difference? Try and calculate it and see what are the results. Take into account the fact that when the moon is low in the skies it is a little further (Add some of the radii of the Earth) to the distance. This difference can be about 1-1.5%
Moon at Perigee and Apogee. try to compare the size
Moon at perigee and apogee. try to compare the size

Also, do not mistake a perigee moon with the large moon illusion or the orange color of  a rising moon which are different (and in my opinion, more interesting)
Orange moon rising. It looks large to the naked eye due to the large moon illusion. It is also a supermoon.


During 2012 the moon will be full at perigee on May 6 2012. The moon will be exactly full on its minimal distance of only 356953 Km and in apogee on 28th of November (406364Km). These dates are the best to take photos and compare the moon size.
Here is the Moon from May 5 2012 - Known as Supermoon of 2012. The comparison photo will wait a few months.
Supermoon May 2012
Supermoon May 2012


Friday, February 3, 2012

Astronomy and Poetry

What are the relationships between poetry and astronomy? Both are very ancient, from the dawn of the civilization, and seem to be very different. Astronomy is very scientific while poetry is about expressing feelings. Harvard university hosts a series of art lectures every summer. In 1967, Jorge Luis Borges was invited to give 6 lectures. The lectures were later forgotten for a long time, but eventually they were found and published in an audio book and as a regular book whose name is "This craft of verse".

The citation  which is related to our topic appears at the beginning of the book:

"Whenever I have dipped into books of aesthetics, I have had an uncomfortable feeling that I was reading the works of astronomers who never looked at the stars."
Borges might have referred to this cartoon, showing 3 astronomers debate which one of them looks the least at the skies.
The physician Richard Feynman however has a very different attitude:
"What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?"
However many poems and songs are about stars, and most astronomers and astrophysicist take a look at the stars and enjoy this.
Lets start with Space Oddity, the famous hit by David Bowie. There are lots of cover versions for this song.



The following song is in Hebrew, but I am adding a short translation of my own, even if you do not speak Hebrew you will enjoy the tune and identify some of the names. You can also try and Google translate the following page



Milky way Ballad
Venus send a smile to Jupiter
Hey Jupiter, lets go out
A cappuccino cup in the Milky way
And drop by Cassiopeia
Grab the dipper, little or big
This night is terrific

It's quite a bit, Jupiter and Venus alone
Going out hand in hand 
hand in hand in the heavens...

Lets jump for an hour to the north star
With a light breeze blowing
Just don't be like Plato
Those I do not like
Without a notice, on the tail of a comet,
we will sit for a moment

It's quite a bit...

Jupiter and Venus going higher
The stars wink to them
And Orion said without doubts
What a couple
And only Mars become jealousy red
She will leave him soon in the future...

Let's continue...

Robert Burnham was a professional astronomer and his work "Burnham's celestial Handbook" (BCH) is a must be in every  astronomy library. His handbook (3 large volumes with more than 1000 pages) is a result of thousands of hours of work prior to the era of digital photography. And although the photos look old, and many amateurs get better results today, the books are still valuable with tons of information. Burnham's story is tragic, and mentioning his work is important. An important part of his books were the poems he wrote between the chapters. There are people who bought the books only for the poems. If you do not own a copy of the BCH, get one today (All 3 volumes).


Another good example would be the poet Robert Frost, with his poem Canis Major (The greater dog).

Canis Major

by Robert Frost


The great Overdog
That heavenly beast
With a star in one eye
Gives a leap in the east.

He dances upright
All the way to the west
And never once drops
On his forefeet to rest.

I'm a poor underdog,
But to-night I will bark
With the great Overdog
That romps through the dark.


And for dessert listen to this one: 'Drops of Jupiter" by Train.


So it seems that both Borges and Feynman were wrong, and astronomy and poetry go together hand in hand at least as Jupiter and Venus.
I am sure that there are plenty more poems and songs. Please add your favorites (to the comments area).

What is the size of Mars

What is the size of Mars? How big is Mars? The Radius of Mars is 3,389.5 km (About half of the radius of the Earth). Its circumference is 21,344 km (Not a big surprise, this is also about half of the circumference of the Earth). The volume of Mars is 1.63116 X 1011 km3 and the mass of Mars is 6.4169 x 1023 kg.
Although Mars is smaller than Earth its surface area (38% of earth) Is Almost identical to earth LAND space (Since there are no oceans on Mars).
A common hoax is about the moon and Mars being equal in size. The hoax started back in 2003 when in august 27th Mars was in opposition to earth (Minimal distance) of about 55 Million KM. When Mars was in conjunction with the moon (A planet-moon conjunctions occurs once in a month), the message was that looking at Mars through75X magnification telescope will results in a size similar to a moon. While this is more or less correct, the hoax removed the telescope and the magnification leading people to think that Mars will be as big as the moon to the naked eye. This is of course a complete rubbish. Also the year 2003 was left out and that hoax continues for a year after a year starting mid June and ending After august. Any email that you see with a subject that includes "27th August" is a candidate for the hoax. but don't despair, simply reply with link to this articles and help a little to fight the hoax.
To kill the Hoax completely look at my own photo of Mars and the moon from 24-Dec-2007. There was no occulation (The moon did not cover Mars), but they were extremely close to each other. Mars red color is quite distinctive. You might need to enlarge the photo to see the small disc (It is clear that this is a disc and not a dot of a star) of Mars just under the Moon. Look closely. It is there (around 7 o'clock). Mars was not as close as 55Million KM, but still the difference in size is huge. I took the photo in the early morning. Notice the nice flock of birds to the right.
Mars size
Mars size compared to the moon
Mars distance from Earth varies a lot. The distance can be as short as 55M kilometers or as far as 350M kilometers. During the times that Mars is far, it is quite dim, and its red color almost unnoticeable to the naked eye. It is best to observer it when it is close, and with a good telescope with 100X magnification, you will see many details on it.

Sunspots demonstrate Earth's rotation

How to observe and photograph sunspots
Sunspots are regions on the sun on which the surface temperature is slightly lower. These regions emit less visible energy and from earth they look as dark spots. When looking at the sun with proper eye protection (glasses which are suitable for solar eclipse) the spots are clearly seen.
Warning: Looking directly at the sun, or photographing it without protection is dangerous and can cause permanent eye damage.

This article focuses on how to photograph sunspots. I've used a regular camera with 35X zoom and a special sun-blocking filter which blocks 99.99% of the sun rays (and also blocks UV and IR radiation). Photographing sunspots requires using a dedicated filter, it is not possible to improvise and use for example an exposed films for this purpose!
Sunspot AR1429 6-Mar-2013 morning and evening
Sunspot AR1429 6-Mar-2013 morning and evening


The spots can be seen easily. Looking through a telescope (again, a proper and dedicated filter is a must, using a telescope focuses the sun's energy into a single spot and using a non-proper filter will lead to immediate and permanent damage to your eye) will show even finer details, while looking through a special solar telescope will show details on the sun limb as well.

sunspots
Sunspot

sunspots
Sunspot
Both pictures show the same sunspots (sunspots are officially numbered and these two are 1203 and 1204 in case you wonder). The first photo was taken in the morning and the second just before sunset, and you can see that the location of the sunspots is very different. Why is this? It is not due to the daily movement of the sun (actually it is the earth which moves). It is also not due to the rotation of the sun around its axis (the sun rotates around its axis, and this rotation changes the location of the spots, however, the change is visible after a day or two and not just after several hours). The reason is simply the rotation of earth around its axis. To further explain this, look below at the same photos as above, only now I have drawn in the sun's axis. You will see that the spots are in the same place, relative to the axis, and what has changed is the angle at which we, on earth, observe the sun.

sunspots
Same sunspots in Sunrise (right) and Sunset (left)

To summarize the issue, please watch the following video.



Albedo effect on the moon's brightness

A full moon is very bright. So bright that you can read a book by its light. The moon the day before or after is almost as bright, at least it seems to be perfectly round and only a fraction of a percent is not lit, so how much can the brightness change? Actually a lot. Similarly, half moon, is not half the brightness of a full moon but much much less. We will see how the albedo effect influence the moon brightness over a period of a lunar month.

We will present the graph first, and then try to understand the reason for this strange phenomenon, which seems to defy logic.
The changes in the moon brightness during a single lunar month. Notice the big daily differences.
The changes in the moon brightness during a single lunar month. Notice the big daily differences.

First, lets give some explanations on the measurement of magnitudes of stars. Brightness of stars is measured in logarithmic scale. Any change of 5 units in the magnitude is a 100-fold change in brightness. The lower the magnitude,  the higher the brightness of the star. One magnitude unit represents a difference of about 2.5 times. As a reference star, Vega's magnitude is defined as zero. The magnitude of the sun is -26. The magnitude of the full moon is -12.7, much less than the sun but still the second brightest object in the sky.

The graph above shows the brightness of the moon in percent from its peak (100%). Please note, that  the actual peak is not reached every month, since it depends on the moon's distance from Earth (the moon is a little brighter when it is closer to earth), but the surprise is the curvature of the graph. You can zoom into the graph and see how even the day before full moon, the brightness is only 75%, three days before full moon the brightness is half (While to the eye the circle of the moon looks nearly perfect as more than 90% of the moon is illuminated). The brightness of the half moon is only eight percent of the full moon, and the brightness measured at the beginning of a lunar month is less than a promil of a percent.
Why does this happen? The difference in brightness is due to several reasons. One intuitive. The less the phase of the moon, its brightness decreases. For example, for a half moon, this reason explains half of the decline (but not the other 85% of the decline).

The moon, like everything, has an Albedo. Albedo means the amount of light which is reflected from an object. The Albedo of the moon on average is 0.12 meaning that it returns only 12% from the light that it gets from the sun (this is relatively a low Albedo compared to other planets). But even this little reflection is made only when the moon is lit directly, what happens in the middle of the month. Mid-month light hits the moon at an angle and some of the light does not come to us, in addition to the lunar surface is not smooth but very rough. When the light comes to the moon at an angle (however minor), many areas of the moon surface are not lit and thus, do not reflect light at all. When the angle increases, the percentage of these parts increases, and the moon returns less and less light, resulting in overall decrease of the brightness .

Even when the moon is full, its brightness does not reach a peak (even at maximum closeness to earth). There's always an angle between us and the moon (the moon is not on the same plane as the sun and Earth) and when there is no angle and the moon can indeed return 100% of the light, the Moon will be the shadow of the Earth, we will experience a marvelous full lunar eclipse, and we will not observe the moon at all.

If you have a camera that allows you to control the setup you can test the moon brightness for yourself . Set the camera to measure light from the middle only (Spot). In this way the camera measures light only from the moon (of course put the moon in the middle of the frame). Set the aperture  to be fixed (on 5.6 for example) and the ISO (on 100) and let the camera adjust the speed according to the amount of light exposure. Compare the exposure data of a half moon to a full moon over several nights and observe the differences. Full moon exposure time will be the shortest. Please note that the measurement of light must be of the same specific spot on the moon. Even the moon itself has brighter and darker areas.

Even so, the moon, from the second day of the month, is the brightest object in the sky (except for the sun of course). Even then it casts a faint shadow (must be a dark place to see a pale shadow), as the moon waxes it becomes more noticeable, easier to pay attention to its shade. As an exercise, try to stand in dark places on different days of a month and see if you recognize the moon shadow yourself. The moon can be seen in daylight. Note the moon in the daytime and the same moon at night. The bright moon of the night seems so pale in the day and  hardly more prominent than the surrounding clouds. The brightness of the moon did not change at all  but the  brightness of the day sky makes it look paler. An additional factor is that the brightness of the moon relates to its entire area in the skies, while usually for stars and planets the brightness is measured for a little dot. This explanation would clarify why Venus in the photo below looks much brighter than the Moon, despite the fact that the moon's brightness is higher.
The moon and Venus. Venus looks brighter than the moon although the moon's brightness is higher
The moon and Venus. Venus looks brighter than the moon although the moon's brightness is higher

Measuring the speed of light with microwave

in this experiment we will measure the speed of light with microwave and chocolate . This is a great experiment for kids. One way is to measure how long it takes, from opening a packet of chocolate to the moment the kids finish it. This is indeed very high speed but still less than the speed of light. The speed of light is one of the most important constants of nature science in general and astronomy in particular but measuring it was a challenge which required complicated experiments.

Today you can conduct an experiment and obtain a very accurate value for the speed of light using nothing but a domestic microwave oven and chocolate bars. The experiment is suitable for children of all ages. First we will describe the experiment and then explain the physics behind it.
Required equipment:
Microwave oven – Almost any microwave will be suitable. Microwaves in which the revolving plate cannot be removed or have more than one radiation source, do not qualify. You must check the frequency of the oven. The frequency usually appears on a sticker at the back of the oven. Most ovens work at a frequency of 2450MHz but it is worth checking anyway.
Note frequency (2450)
Note the frequency 2450Mhz


To perform the experiment you must be able to remove the revolving plate from the microwave and place the chocolate bar on a plate in parallel to the door as sjhown in the following picture:
The chocolate lying in the microwave


Start the microwave at maximum power for half a minute to let some of the chocolate melt, remove carefully and put on a flat surface.
Please note that there are places that the melting is observable (three places) and other places did not melt at all. Find the distance between two places which have not melted at all. From the photo, the distance is about 6cm (2.362 inches)
Measure between two non-melted places in the chocolate

All that's left to do is simple arithmetic:
(Distance * 2 * frequency) divided by (100,000) KM/Sec which is to be used if the distance is measured in centimeters
Or
(Distance * 2 * frequency) divided by (77,335) Miles/Sec which is used for distance in inches

In our example (sorry U.S. guys, the metric system rules!):
(6*2*2450,000,000)/100,000 = 294,000 KM/second (~182000 Miles/Sec). Amazing.
Why does it work?
Electromagnetic waves are moving at the speed of light (almost, it is little less due to the air, but it really does not matter for the experiment). Microwave structure causes the wave to be a standing wave.
Standing wave - Source: Wikipedia
Notice the red dots on the wave, which always remain at the same height. Where there is no movement there is no heat and energy. Also, there are the peaks of the wave, at which the warming will be greatest. For this reason there are rotating plates in the microwave so the food will be evenly heated.
The photo shows that the distance between two points with zero energy is exactly equal to half of the wavelength. These are the places where the chocolate has not melted at all. The Wave formula says that the wave length * number of waves (frequency) = wave speed.
So we get the frequency from the microwave manufacturer, the wavelength, we measured with the chocolate. All we need is to put them into the formula (division is to transfer from centimeters to kilometers) and get an amazing precise result for the speed of light.


A rockect and a sundog

Sometimes, unexpected things happens. During a quite ordinary Launch of the Solar Dynamic Observatory (SDO), an important mission to research the Sun, the rocket passed near a sundog when it reached a supersonic speed and broke it apart. Notice the shock-wave created by the rocket. The video was taken by 13 years old Anna Herbst.
Sun dogs are an atmospheric phenomenon which due to ice crystals in the clouds creates a bright image on both sides of the Sun (Hence the terms dog). It is not often visible from Israel since it is regularly not cold enough here, but If you observe carefully you will see them from time to time.

SDO has a close encounter with a sundog. Movie formats: 10 MB Quicktime, 1 MB mpeg-4. Credit: Anna Herbst of Bishop, California.
Another video showing the entire launch and the shock-wave:

Thursday, February 2, 2012

The Space Shuttle

The space shuttles were designed as a continuation of the American space program after the Apollo program ended officially in 1975. Unlike the Apollo spaceships which were designed for a single use (most of the Apollo spacecrafts remained in space or burned in the atmosphere. The remaining capsules were distributed to several museums), the shuttles were designed to be launched as a rocket and to land just like an airplane. The first space shuttle took off in 1981. Its commander was John Young. His name is unknown to many, but he is a veteran astronaut and has a very long career at NASA. John Young was an astronaut in Gemini, two Apollo flights, one of them (Apollo 16) he commanded and landed on the moon, and was a natural choice for the first pilot of the new spacecraft. The shuttle Columbia first flight was a success.

The first flights were mainly for research purposes or for placing satellites in orbit. With the beginning of the construction of the International Space Station, most tasks were to build the station. The shuttles brought parts to the stations and the astronauts connected them to the station in space walks (known as EVA – External Vehicle Activity). With the development of the space station, more and more tasks are performed by external robots.
The first shuttle disaster was in 1986, when just seconds after the launch of the Challenger (live broadcast of course) the shuttle exploded in the air. I remember myself as a child watching the launch live and the shock that then struck everyone. After the disaster the shuttle was grounded for a few years while the investigation committee wrote long and detailed reports. A member of the investigation team was Richard Feynman, whose personal report was published as an appendix to the official reports and regarded as a masterpiece worth reading in its own right. The report revealed many flaws in NASA activities and the shuttle program resumed only after a long time.

The shuttles achieved many successes, but another disaster, the Columbia disaster which killed Ilan Ramon, was the sign of the beginning of the end. Colombia was launched successfully, but the launch video images already pointed out that there was a problem in the isolation of the shuttle. Investigation reports have shown after the disaster that there were failures in transferring the information, the decision making process of executives and complacency of "to me, it will not happen". During the return to Earth, the shuttle insulation was defect and heat generated due to large atmospheric friction dissolved the Columbia, causing an explosion. The excitement in the country during the launching mission was hard to forget, many of us saw the live launch, and the entire State of Israel was in grieve mourning. 
Seated in front are astronauts Rick D. Husband (left); Kalpana Chawla and William C. McCool. Standing are (from the left) astronauts David M. Brown, Laurel B. Clark, Michael P. Anderson, and Ilan Ramon


After grounding the shuttle program yet again, it was decided to take all shuttles out of service by 2010. After the Challenger disaster, a new shuttle was built (Endeavor), but no new shuttle was built after the Columbia disaster, and the three remaining shuttles' (Discovery, Atlantis and Endeavour) schedules changed and many missions were canceled. Today, as only 5 shuttle missions are left, the shuttles are offered for sale for a modest sum of $ 29 million (excluding transfer costs)


Another high-profile mission of the shuttle was STS-125 service mission to the Hubble Space telescope. Many modules of the telescope were outdated, and parts had to be replaced in order for the telescope to function. The mission was approved under pressure from the public, because the importance of Hubble to science and to the entire human culture in general. There has not been another telescope which has enriched our world so much. Despite the risk and cost, the mission was approved and was extremely successful mission. Hubble space telescope will now serve us at least until 2015.


The shuttles always take off from Florida from one of two launching pads (now only one is active, the other has been transformed to use for the next generation of space vehicles). The shuttle is built and integrated in a huge structure. The building is the tallest one story building in the world with the world's tallest doors. The shuttles are transported from that building to the launch pad on a special vehicle at the amazing speed of, hold tight, half a mile per hour. The shuttle is connected to a huge external fuel tank and two booster accelerators. Both the shuttle’s engines and the boosters are active during the launch to create tremendous thrust, and two and a half minutes later the boosters are cut off and fall back to the Atlantic. The shuttle continues on its engines for another eight minutes and the external fuel tank then disconnects and falls to the Indian Ocean.
After that the space shuttle carries out the tasks or connects to the space station. To land, the shuttle just slows down and begins to fall to earth (slowing of 200 mph is enough). Once this process begins it cannot be stopped. The beginning of the reentrance is determined by the exact landing location. The most desirable location is back in Florida, but this depends on the weather in California. Shuttles landing in California make their way back to Florida on a special Boeing 747 at a cost of another million dollars. Around the world there are more airports where a shuttle can theoretically land, in case there is failure requiring emergency landing immediately after launch. In practice, a landing has never taken place outside the United States.