Dark Matter
What do scientists look for when they search for dark matter? We cannot see or touch it: its existence is implied. Possibilities for dark matter range from tiny subatomic particles weighing 100,000 times less than an electron to black holes with masses millions of times that of the sun (9). The two main categories that scientists consider as possible candidates for dark matter have been dubbed MACHOs (Massive Astrophysical Compact Halo Objects), and WIMPs (Weakly Interacting Massive Particles). Although these acronyms are amusing, they can help you remember which is which. MACHOs are the big, strong dark matter objects ranging in size from small stars to super massive black holes (1). MACHOs are made of 'ordinary' matter, which is called baryonic matter. WIMPs, on the other hand, are the little weak subatomic dark matter candidates, which are thought to be made of stuff other than ordinary matter, called non-baryonic matter. Astronomers search for MACHOs and particle physicists look for WIMPs.
Astronomers and particle physicists disagree about what they think dark matter is. Walter Stockwell, of the dark matter team at the Center for Particle Astrophysics at U.C. Berkeley, describes this difference. "The nature of what we find to be the dark matter will have a great effect on particle physics and astronomy. The controversy starts when people made theories of what this matter could be--and the first split is between ordinary baryonic matter and non-baryonic matter" (10). Since MACHOs are too far away and WIMPs are too small to be seen, astronomers and particle physicists have devised ways of trying to infer their existence.
MACHOs
Massive Compact Halo Objects are non-luminous objects that make up the halos around galaxies. Machos are thought to be primarily brown dwarf stars and black holes (2). Like many astronomical objects, their existence had been predicted by theory long before there was any proof. The existence of brown dwarfs was predicted by theories that describe star formation (7). Black holes were predicted by Albert Einstein's General Theory of Relativity (11).
Brown Dwarfs. Brown dwarfs are made out of hydrogen--the same as our sun but they are typically much smaller. Stars like our sun form when a mass of hydrogen collapses under its own gravity and the intense pressure initiates a nuclear reaction, emitting light and energy. Brown dwarfs are different from normal stars. Because of their relatively low mass, brown dwarfs do not have enough gravity to ignite when they form (7). Thus, a brown dwarf is not a "real" star; it is an accumulation of hydrogen gas held together by gravity. Brown dwarfs give off some heat and a small amount of light (7).
Black Holes. Black holes, unlike brown dwarfs, have an over-abundance of matter. All that matter "collapses" under its own enormous gravity into a relatively small area. The black hole is so dense that anything that comes too close to it, even light, cannot escape the pull of its gravitational field (11). Stars at safe distance will circle around the black hole, much like the motion of the planets around the sun (7). Black holes emit no light; they are truly black.
Detecting MACHOs
Astronomers are faced with quite a challenge with detecting MACHOs. They must detect, over astronomical distances, things that give off little or no light. But the task is becoming easier as astronomers create more refined telescopes and techniques for detecting MACHOs.
Searching with Hubble. With the repair of the Hubble Space Telescope, astronomers can detect brown dwarfs in the halos of our own and nearby galaxies. Images produced by the Hubble Telescope, however, do not reveal the large numbers of brown dwarfs that astronomers hoped to find. "We expected [the Hubble images] to be covered wall to wall by faint, red stars," reported Francesco Paresce of the Johns Hopkins University Space Telescope Science Institute in the Chronicle of Higher Education (5). Research results are disappointing--calculations based on the Hubble research estimate that brown dwarfs constitute only 6% of galactic halo matter (12).
Gravitational Lensing. Astronomers use a technique called gravitational lensing in the search for dark matter halo objects. Gravitational lensing occurs when a brown dwarf or a black hole passes between a light source, such as a star or a galaxy, and an observer on the Earth. The object focuses the light rays, causing the light source to brighten (13). Astronomers diligently search photographs of the night sky for the telltale brightening that indicates the presence of a MACHO.
Wouldn't a MACHO block the light? How can dark matter act like a lens? The answer is gravity. Albert Einstein proved in 1919 that gravity bends light rays (13). He predicted that a star, which was positioned behind the sun, would be visible during a total eclipse. Einstein was right--the gravity of the sun bent the light rays coming from the star and made it appear next to the sun.
Friday, January 26, 2007
Sunday, September 10, 2006
FORTUITOUS DREAM
Not for the first time I forgot my car keys in my office. As usual I returned from the lift and picked it. It was a Saturday evening. That was a usual day but along the way back to home I met Miss Margaret. She had grown older, her rustier eyes, lean and rough skin indicated that. She had sold her home after their death and went to New York.
After some other talks we bid good bye each other. I was home at nine. I had been living in a cottage since I got a job. I had spent all nights, wandering along the corridors and watching the sky. But in that night I didn’t have any time to usual work. I just ate some sausages and went to bed. Something disturbing was flying around my mind. Exactly the sleep wasn’t a comfortable one. In its middle I went back to my school days, in to my higher secondary school. I saw myself standing among a number of students. It was the school day. I was watching the play.
"Hay Elude where’s nick? He’s not found anywhere."
Asked a pale-red faced gentle guy. He had blue eyes, golden brown hair and an intellectual look.
He was one of my best friends, Peter Clowding and the one whom he enquired was his twin brother, Nick Clowding. Both of them were my dearest friends, like my treasure.
"Well I don’t know. I didn’t see him today. Pete don’t worry he’ll be there at right time. I’m sure." I consoled him
"But you know Elude I don’t want him to lose his prize for music." Said he
"Yes I know"
Hm….. Ok, now we’ll wait him." Said he
"Hay guys what you two are doing there. Come on you need to be here. It’s my turn."
We looked around for the owner of the sound. It was Nick. In sight he was same as Peter except the eyes. He had golden brown eyes.
"Nick, where were you from morning?" enquired I
"Him I was in the mess."
"Mess?"
"Yes not for eating, for practice."
"You! And practice?"
"Oh! I can’t believe." Exclaimed I
"I couldn’t, but that Jack boy he persuaded me and was guarding me too. So I couldn’t escape." Said he
"Well he’s trying you to get the first prize, but it’s already yours." Said I
That was correct. As usual he got the first prize. He was good at every games and arts. Peter was also good at all these, but he didn’t want to compete.
***********
All of us enjoyed our life as best as we could and were perfect in our studying too. In those days I was with my uncle who was a teacher and helped us in studying.
Peter’s and Nick’s parents were in New York. They had business there. They wanted both of them to shift to New York, but they liked to stay with Miss Margaret, daughter of their father’s older sister.
***********
Months passed. It was the time of final exam. All lessons settled, revised a lot. One Saturday morning we made a visit to my house
My father was an architect and mother was a professor and I had a little sister too.
Early in the morning we reached my house. We spent the day time, playing with Catherine, my sister. In the evening my mother wanted me to stay. So I went with them to the bus stop which was opposite to my house. There was heavy traffic on the road. We had to wait a long time. After seeing the signal we started to cross. At that time when we reached the middle a bus came against traffic rules. I could only hold Peter. Nick was beyond my reach. I pulled Peter to the road side we two fell down. My head hit in the footpath side and fainted.
***********
I felt someone was calling me like a whisper. A sharp pain was lurking beneath my head. I slowly opened my eyes; saw myself lying in a hospital bed. Mom and dad were near me. I examined myself; found a thick bandage on my head. It was the day after the accident. I was anxious to know about Peter and Nick, especially about Nick. I asked to mom
"Mom, what about Peter and Nick?"
"Well…………they……………"
"What mom?"
"Elude you need rest so take rest. I’ll tell you later." Said she
"No mom. Please………………"
But they left me alone in that room I was sure something bad happened. The effect of medicine and the severe pain made me sleep for hours. But my mind was a disturbing one like a sailor. I was looking for answers, sailing around my mind without any aim.
I woke after along sleep. The pain had reduced. Mom gave me food; I wanted to ask about them, but wasn’t dare enough.
A couple of days passed. Miss Margaret came to see me. It seems that someone stole all her happiness. She looked older than she was. She asked
"How’re you feeling?"
"Better"
"Miss Margaret I need to pay the bill. I’ll be back." Said my mom
When she left I dare to ask Miss Margaret. I asked
"Please tell me what happened to them?"
She suddenly burst in to tears and hugged me tightly
"Oh! Elude they left me. They left me alone."
I felt that something sharp one just cut my mind. A sharp pain, that couldn’t be curable.
"But I pulled Peter. He couldn’t be dead."
"Yes he couldn’t, but he lost himself."
"You mean mad?"
"Yes mad."
"Oh no"
That was enough for us to bear. She left the room trying to hide her tears and agony.
After two days I returned home. There was only a fortnight for the exam. I wasn’t prepared. I was very dull and sad. Catherine tried a lot to cheer me up, but I always made angry words to her. She cried a lot saying, "Mamma Elude isn’t speaking to me."
"Cate, shut up don’t disturb him." Said she
Mom knew my mental pain. So she didn’t ask me anything. But she persuaded me to study for it was a public exam. I wasn’t dare enough to meet Peter. So I remained in my house as long as the exam lasted.
In the evening of the last exam I set out to Peter’s house. I was wandering in my thoughts, seeking an answer for how to face him. I reached his house, their parents behaved as if I’m a hero. I entered in to Peter’s room. He was sitting in the bed, holding Nick’s picture and was anxiously looking into it. His eyes were full of tears. For a moment I thought he was perfectly alright. Suddenly he threw the picture in to floor and laughed clapping his hand. I couldn’t bear more, left the house.
***********
I passed the exam with a good mark but not so high because of the perceived shock. After that I joined for higher studies in New York. But I put aside a day or two per month to visit Peter. I was staying in a hostel. He was recovering himself and after one year seemed to recognize me. Another year gone. I was studying well, but the fact was I couldn’t make any friends in that large campus in two years. The only satisfaction was my monthly visit to Peter, which gave me all the memories a man could have in all his life about his everlasting friends.
One Saturday morning I was just going outside then heard someone say.
"Elude a call for you"
I attended the phone. It was mom
"Elude, how’re you?"
"I’m fine. Mom, what’s the matter in this morning?"
"We all are fine, but I’ve a bad news for you."
"Bad news, for me?"
"Yes Peter, he’s dead."
I put the phone back. I couldn’t hear more. I felt my heart hitting my ribs and my head rolling around me. It was the last time, I felt, what the pain of losing a dear friend was.
***********
Suddenly I woke up with a heavy breath. It was a dream. Not a dream, a real thing happened in my life. It’s been years; still I could feel the fresh pain. Later I thought about the dream. What made me to see such a dream? I hadn’t seen any dreams related to me yet. I sought an answer too. It might be the meeting with Miss Margaret made it.
Next day I woke up right at my regular time, six and involved in my regular routine. I didn’t even think about that realistic dream before I wrote this.
***********
After some other talks we bid good bye each other. I was home at nine. I had been living in a cottage since I got a job. I had spent all nights, wandering along the corridors and watching the sky. But in that night I didn’t have any time to usual work. I just ate some sausages and went to bed. Something disturbing was flying around my mind. Exactly the sleep wasn’t a comfortable one. In its middle I went back to my school days, in to my higher secondary school. I saw myself standing among a number of students. It was the school day. I was watching the play.
"Hay Elude where’s nick? He’s not found anywhere."
Asked a pale-red faced gentle guy. He had blue eyes, golden brown hair and an intellectual look.
He was one of my best friends, Peter Clowding and the one whom he enquired was his twin brother, Nick Clowding. Both of them were my dearest friends, like my treasure.
"Well I don’t know. I didn’t see him today. Pete don’t worry he’ll be there at right time. I’m sure." I consoled him
"But you know Elude I don’t want him to lose his prize for music." Said he
"Yes I know"
Hm….. Ok, now we’ll wait him." Said he
"Hay guys what you two are doing there. Come on you need to be here. It’s my turn."
We looked around for the owner of the sound. It was Nick. In sight he was same as Peter except the eyes. He had golden brown eyes.
"Nick, where were you from morning?" enquired I
"Him I was in the mess."
"Mess?"
"Yes not for eating, for practice."
"You! And practice?"
"Oh! I can’t believe." Exclaimed I
"I couldn’t, but that Jack boy he persuaded me and was guarding me too. So I couldn’t escape." Said he
"Well he’s trying you to get the first prize, but it’s already yours." Said I
That was correct. As usual he got the first prize. He was good at every games and arts. Peter was also good at all these, but he didn’t want to compete.
***********
All of us enjoyed our life as best as we could and were perfect in our studying too. In those days I was with my uncle who was a teacher and helped us in studying.
Peter’s and Nick’s parents were in New York. They had business there. They wanted both of them to shift to New York, but they liked to stay with Miss Margaret, daughter of their father’s older sister.
***********
Months passed. It was the time of final exam. All lessons settled, revised a lot. One Saturday morning we made a visit to my house
My father was an architect and mother was a professor and I had a little sister too.
Early in the morning we reached my house. We spent the day time, playing with Catherine, my sister. In the evening my mother wanted me to stay. So I went with them to the bus stop which was opposite to my house. There was heavy traffic on the road. We had to wait a long time. After seeing the signal we started to cross. At that time when we reached the middle a bus came against traffic rules. I could only hold Peter. Nick was beyond my reach. I pulled Peter to the road side we two fell down. My head hit in the footpath side and fainted.
***********
I felt someone was calling me like a whisper. A sharp pain was lurking beneath my head. I slowly opened my eyes; saw myself lying in a hospital bed. Mom and dad were near me. I examined myself; found a thick bandage on my head. It was the day after the accident. I was anxious to know about Peter and Nick, especially about Nick. I asked to mom
"Mom, what about Peter and Nick?"
"Well…………they……………"
"What mom?"
"Elude you need rest so take rest. I’ll tell you later." Said she
"No mom. Please………………"
But they left me alone in that room I was sure something bad happened. The effect of medicine and the severe pain made me sleep for hours. But my mind was a disturbing one like a sailor. I was looking for answers, sailing around my mind without any aim.
I woke after along sleep. The pain had reduced. Mom gave me food; I wanted to ask about them, but wasn’t dare enough.
A couple of days passed. Miss Margaret came to see me. It seems that someone stole all her happiness. She looked older than she was. She asked
"How’re you feeling?"
"Better"
"Miss Margaret I need to pay the bill. I’ll be back." Said my mom
When she left I dare to ask Miss Margaret. I asked
"Please tell me what happened to them?"
She suddenly burst in to tears and hugged me tightly
"Oh! Elude they left me. They left me alone."
I felt that something sharp one just cut my mind. A sharp pain, that couldn’t be curable.
"But I pulled Peter. He couldn’t be dead."
"Yes he couldn’t, but he lost himself."
"You mean mad?"
"Yes mad."
"Oh no"
That was enough for us to bear. She left the room trying to hide her tears and agony.
After two days I returned home. There was only a fortnight for the exam. I wasn’t prepared. I was very dull and sad. Catherine tried a lot to cheer me up, but I always made angry words to her. She cried a lot saying, "Mamma Elude isn’t speaking to me."
"Cate, shut up don’t disturb him." Said she
Mom knew my mental pain. So she didn’t ask me anything. But she persuaded me to study for it was a public exam. I wasn’t dare enough to meet Peter. So I remained in my house as long as the exam lasted.
In the evening of the last exam I set out to Peter’s house. I was wandering in my thoughts, seeking an answer for how to face him. I reached his house, their parents behaved as if I’m a hero. I entered in to Peter’s room. He was sitting in the bed, holding Nick’s picture and was anxiously looking into it. His eyes were full of tears. For a moment I thought he was perfectly alright. Suddenly he threw the picture in to floor and laughed clapping his hand. I couldn’t bear more, left the house.
***********
I passed the exam with a good mark but not so high because of the perceived shock. After that I joined for higher studies in New York. But I put aside a day or two per month to visit Peter. I was staying in a hostel. He was recovering himself and after one year seemed to recognize me. Another year gone. I was studying well, but the fact was I couldn’t make any friends in that large campus in two years. The only satisfaction was my monthly visit to Peter, which gave me all the memories a man could have in all his life about his everlasting friends.
One Saturday morning I was just going outside then heard someone say.
"Elude a call for you"
I attended the phone. It was mom
"Elude, how’re you?"
"I’m fine. Mom, what’s the matter in this morning?"
"We all are fine, but I’ve a bad news for you."
"Bad news, for me?"
"Yes Peter, he’s dead."
I put the phone back. I couldn’t hear more. I felt my heart hitting my ribs and my head rolling around me. It was the last time, I felt, what the pain of losing a dear friend was.
***********
Suddenly I woke up with a heavy breath. It was a dream. Not a dream, a real thing happened in my life. It’s been years; still I could feel the fresh pain. Later I thought about the dream. What made me to see such a dream? I hadn’t seen any dreams related to me yet. I sought an answer too. It might be the meeting with Miss Margaret made it.
Next day I woke up right at my regular time, six and involved in my regular routine. I didn’t even think about that realistic dream before I wrote this.
***********
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