Arxiu del dimarts , 29/01/2019

La métrica de Alcubierre

dimarts , 29/01/2019

La métrica de Alcubierre es una solución para las ecuaciones del campo de Einstein en el marco de la Teoría General de la Relatividad, que describen la relación profunda que existe entre la materia-energía y la geometría del espacio-tiempo. La métrica de Alcubierre permite la construcción matemática de una nave interestelar más rápida que la luz.

  • Según Einstein, la presencia de materia, o energía concentrada, que acaba siendo lo mismo, curva el espacio. Es decir, en la vecindad de una gran masa, el espacio se arruga y los objetos que por él transitan, siguen trayectorias curvas. Esto es lo que ocurre en la Tierra: si lanzo un balón, poco a poco seguirá una curva, en este caso una parábola, hasta llegar al suelo. La Tierra impone la trayectoria curva al balón.
  • Alcubierre le da la vuelta al asunto. ¿Y si quiero mover el balón como yo quiera? Tendría que inventarme una “Tierra“, es decir, una distribución de masa, que impusiera una trayectoria y además a la velocidad que nos interese. La masa que curva el espacio, en vez de ser un dato  de entrada del problema, como en el caso de un planeta o una estrella, es algo que podemos diseñar.

Este es el planteamiento básico del motor de curvatura de Alcubierre, conocido también por su nombre en inglés warp drive. En las últimas aproximaciones al problema, lo que se plantea es distribuir en anillo cierta cantidad de materia de masa negativa que genera una burbuja de curvatura de espacio-tiempo alrededor de la nave. Esta burbuja de curvatura se diseña para que consiga velocidades superlumínicas. Esto se hace contrayendo el espacio por delante de la nave y expandiéndolo por detrás. Se suele explicar como ir “montado en una cinta transportadora hecha de espacio-tiempo“.

Sí, masa negativa; encontrar o producir suficiente materia con estas propiedades es un reto, y quizá una de las complicaciones más importantes para la construcción real  de una nave interestelar siguiendo las propuestas de Alcubierre. Pero de momento, la posibilidad está ahí.

 

 

Dr. Christopher Kerr

dimarts , 29/01/2019

Dr. Christopher Kerr share his research about end-of-life experiences, supported by some real interviews, with the hope that we would hear what he have heard from the dying. “Their words are compelling and relevant,” he said, and they might leave open the possibility that end-of-life experiences affirm rather than deny life.

Dr. Christopher W. Kerr is the Chief Medical Officer at The Center for Hospice and Palliative Care, where he has worked since 1999. His background in research has evolved from bench science towards the human experience of illness as witnessed from the bedside, specifically patients’ dreams and visions at the end of life. Although medically ignored, these near universal experiences often provide comfort and meaning as well as insight into the life led and the death anticipated.

Transcript

I read a recent survey, and the title was, “Survey on American Fears,” ¶

and what Americans fear most is public speaking and dying.

In other words, my TEDx talk.

(Laughter)

If that weren’t tough enough, tonight’s topic is illumination, and the question is really: can dying be illuminating?

What we know of dying is based on what we have observed as witnesses.

We have all seen grim, physiological decline and suffering, and we’ve all felt profound loss.

0:49 – 0:52

So, if there is light within the darkness of dying, it’s in the experience not in the observing.

So tonight, I’m going to share with you the words and experience of dying patients.

And my hope is that you hear what I have heard: the dying often describing their end of life

in ways that are actually life-affirming, and rich with meaning, love, and even grace.

1:13 – 1:16

Before I go any further, I need to give a few disclaimers.

If it looks like I cannot stand still and I’m pacing, it’s because it’s true.

(Laughter)

The second is that, aside from my mother, nobody has ever described me as particularly spiritual or for that matter, enlightened.

And trust me, this talk has nothing to do with the paranormal.

A much harder truth for me is that I have a deep aversion to the non-physical, spiritual aspects of dying

that goes back to my childhood.

On August 6, 1974, I was 12 years old, and I was standing over the bed of my dying father, who was 42.

1:54 – 1:55

As he lay in there, he reached out and started playing with my buttons on my shirt,

and he said we had to hurry; we had to catch a plane.

We were going to go up north and fish like we had before.

And that was the last time I saw him.

My point here is I didn’t choose this topic of dying;

I feel it has chosen or followed me throughout my life, personally and professionally.

Like my father, I became a doctor.

This may sound strange, but if you have an aversion to dying, medical schools are a pretty safe place to be.

2:26 – 2:31

They never mention dying, let alone the experiencing of it.

Medical training is learning how to defy death, and when you can’t defy it, you deny it, in whole or in part.

This approach to medicine worked for me when I was doing things like working in emergency rooms.

But in 1999, through a series of unusual events, I ended up at this place called hospice.

At hospice, the curative science has not only failed the patient but has abandoned the doctor

who is, eventually, compelled to be present.

And when I was present at the bedside of the dying,

I was confronted by what I had seen and tried so hard to forget from my childhood.

3:07 – 3:10

I saw dying patients reaching and calling out to mothers, and to fathers, and to children, many of whom hadn’t been seen for many years.

But what was remarkable was that so many of them looked at peace.

In April of 1999, I was in the room of a patient I was particularly fond of.

Her name was Mary.

She was nearing the end of her life, and her four children were also present.

3:33 – 3:37

One day, Mary starts cradling a baby that nobody can see.

She refers to him as Danny – a reference nobody understands.

The next day, Mary’s sister arrives from out of town, and explains that Danny was, actually Mary’s first child, who was stillborn.

The loss was so deep that Mary was unable to speak of it during her life.

3:55 – 3:59

Yet, while dying, this indescribable loss returns to her in some manner of tangible warmth

and tangible love.

Mary, like so many dying patients, had physical wounds that could not be cured, yet her spiritual wounds were [being] tended to.

4:12 – 4:16

A few weeks later, I went and saw a young man named Tom.

I came out to the nurse’s station, and I said, “I think Tom has more time if we just give him some IV antibiotics and some IV fluids.”

Without so much as looking up, a nurse named Nancy says, “Nope, he’s dying.”

4:27 – 4:28

I say, “Why?”

She says, “Because he’s seeing his deceased mother.”

I say, “I don’t remember that class from medical school!”

She says, “Son, you missed a lot of classes!”

Anyways…

(Laughter)

Tom ends up dying.

What Nancy knew that I did not know was that Tom’s end-of-life experiences had meaning.

They were significant, and not just to him, but to those of us entrusted with his care.

So, if I were to have any worth, I needed to understand, I needed to learn.

4:57 – 5:01

I learned that end-of-life experiences are the subjective experiences of the dying

and often refer to pre-death dreams and visions.

Such experiences have been reported throughout history and across cultures.

5:10 – 5:14

They are mentioned in the Bible, Plato’s “Republic”, Shakespeare.

In our culture, the richest and most thoughtful discussions have always come from the humanities and never medicine

but from poets, playwrights, and philosophers.

5:23 – 5:25

These observers have commented that end-of-life experiences are so frequent they are essentially intrinsic to the process of dying.

They’re characterized as real, intense, meaningful; provide comfort, insight, and in so doing, help alleviate the fear of dying.

5:43 – 5:45

So why does medicine has so little to say about something that’s so meaningful,

and actually, potentially therapeutic, not just for the patient but for the patient’s loved ones?

In part, it’s because end-of-life experiences can easily be dismissed as confusion.

And it’s true; many dying patients experience confusion as they go through the process.

6:03 – 6:04

However, in contrast to patients’ experience with end-of-life dreams and visions,

confused patients are detached.

They have disorganized thinking.

They’re unable to figure out their surroundings, and they are more often than not terribly agitated and anxious.

6:21 – 6:25

The distinction is best [understood]

by listening to a patient.

The patient you are about to see in this video – her name is Jeanne -

was nearing the end of her life; and she has since passed.

(Video starts)

6:34 – 6:36

Jeanne: I was lying in bed, and people were walking, very slowly, by me.

The right hand side, I didn’t know, but they were all very friendly, and they touched my arm

or my hand when they went by.

But the other side, were people that I knew.

My mom and dad were there, my uncle;

Everybody I knew that was dead was there.

And they passed and did the same thing.

I thought it was a good dream, but boy, I remember seeing every piece of their face.

I mean, I know that was my mom and dad, and uncle, and my brother-in-law.

I have seen my mother, recently, more.

Interviewer: How do you feel when you see her?

Jeanne: Oh…! Wonderful!

I can’t say that my mother and I got along all those years, but we made up for it, at the end.

(Video ends)

7:43 – 7:45

Christopher Kerr: Jeanne isn’t confused, and it would be dehumanizing her

to label her as such.

But she shows us so much more.

She shows us that dying is this paradox: she is physically declining, yet, emotionally and spiritually, she’s vivid; she’s alive, and she’s present.

7:59 – 8:03

End-of-life experiences are not only tied to our personal meanings

but they are tied to some of our greatest needs: the need to love, to be loved,

nurtured, forgiven.

End-of-life experiences also represent a rich inter-connectivity between body and soul, between the realities we know,

and those we don’t, between our past and our present.

But most importantly, end-of-life experiences represent continuity

between and across lives, both living and dead, so that mothers like Mary can hold their long-deceased children,

and children like Jeanne can be reunited and comforted by their long-deceased mothers.

8:44 – 8:46

So, again, the question: why are the words of the dying not worthier of our consideration?

I don’t have all of the answer, but it’s true we live in a time where seeing is believing,

and where data and evidence are requisites for both understanding and acceptance.

Unfortunately, when it comes to end-of-life experiences,

most of the reports were based on anecdotal reporting.

In other words, nobody had asked patients directly or attempted to quantify or measure.

So that’s what we’ve done, and to date, we have over 1,400 interviews with dying patients.

In our first study, we spoke with 66 patients every day, until their death, and gathered 450 interviews.

What we found was a vast majority, over 80%, reported at least one pre-death dream and vision,

described as more real than real, and distinct from normal dreaming.

The next question is: what were they dreaming of?

We found out that 72% dreamed of the deceased: family, relatives, or pets,

59% of this theme of going or preparing to go [somewhere],

29% of the living, and 28% of past meaningful experiences.

So the next question was this: did different dream content provide different levels of comfort?

10:04 – 10:08

Here’s comfort on a zero to five scale, with five being the highest.

And of all the dream types, seeing the deceased was associated with the greatest degree of comfort.

The next question was: were there changes over time in either the content or frequency of dreaming as patients approached death?

Essentially, the Nancy question; could you almost predict death based on changes of these variables?

Of course, again, Nancy’s right.

Frequency is on the y-axis, weeks before death are on the x-axis.

As patients approach death, they’ve a dramatic increase in the frequency of their dreaming.

10:41 – 10:44

They are dreaming, specifically, of the deceased,  which is associated with the greatest comfort.

So, the next question we wanted to ask in our next study

was what did these mean to the dreamer?

Were there common themes?

Were there common meanings?

The most common theme was that of a comforting presence.

Seeing the dead or seeing the living was overwhelmingly positive

provided a sense of reunion, and the feeling that one was not alone.

Maggie, for example, was in her 80s.

She had been harmed greatly by a childhood friend, later in life.

And before she dies, she dreams of this friend, who comes back to her and says,

“Sorry, you are a good person.

If you need help, just call my name.”

Kenny was 88 years old.

He lost his mother as a child.

And before he dies, he dreams he’s a child again.

He is in his mother’s kitchen, and he says, “I smell her perfume,” and hears her soothing voice say, “I love you!”

11:44 – 11:47

Sandy was raised by her sister Emily.

And before she passes, Emily returns to her in a dream and says,

“Remember what I taught you.”

Many patients reported seeing the presence of others, and they’re described as simply being there, watching.

Little is said, but much is understood.

This next video is Paul.

Paul has a terminal illness.

In fact, he dies three weeks after this video.

But he’s talking about his deceased wife.

 (Video starts)

12:13 – 12:15

Paul: I dream in color, most times.

And she always wears a beautiful light blue.

It could be a suit.

It could be a gown. It could be a dress.

But it’s always light blue.

A couple of times, she’s giving me the little beauty pageant wave.

And a couple of times, she, sort of, greets… always with a smile.

Only once or twice have I ever heard her voice.

She always lets me know that she’s fine.

I get that feeling after a dream like that.

(Video ends)

CK: As I said, 60% dreamed of this theme of travel.

Jimmy sees many deceased friends and relatives and says,

“I haven’t seen some of these people in years.

I know we are going somewhere, but I don’t know where.”

Others dreamed of the deceased just there, waiting for them.

Sarah says, “There were six dead family members in my room waiting for me.

It’s good to see them.”

Less frequently, people had distressing dreams.

These are often relived, past, traumatic events, such as war.

And here again is Paul.

 

(Video starts)

13:14 – 13:19

Paul: Another thing I’ve dreamed of quite often, not lately,

is I’m back in the service.

I’m at Fort Devens up in Massachusetts,

where they were forming this company we were going to oversee; a new company.

The guys are all young. They’re like…

I remember them! And I am old.

And I’m trying to tell them, “Guys! I’ve been here. I’ve done this.

I’m not going to do it again!”

And they’re arguing with me!

(Video ends)

(Laughter)

CK: I have the deep privilege of hearing many people’s life stories which tend to emerge or come to surface at the end of life.

Sometimes, I’m saddened by the amount of trauma and tragedy people have endured.

But more often, I’m inspired by the strength of the human spirit,

and its endless quest to heal what is harmed, and what is broken.

And this brings me to the story of Mack.

I met Mack in 2011.

When I walked into his room and started to talk to ask him what was wrong, he gave me three words, and he said,

“A war problem.”

His family explained that Mack never spoke about the war, but in the last few weeks, he was unable to close his eyes without reliving the horror.

14:30 – 14:34

He couldn’t sleep that’s why he was coming into our facility.

Mac went on to explain that he was a World War II vet.

He was very proud to be from Texas and serve on the USS Texas.

14:42 – 14:47

At the age of 17, he was involved in the invasion of Normandy, in June, 1944.

He was a gunner on a landing craft that went from the ship to the shore.

But his nightmares were about the return from the shore to the ship.

Because that’s when he was transporting the dead and the dying.

He called these nightmares terrifying and realistic.

15:04 – 15:08

He says, “There is nothing but death… dead soldiers all around me.”

A few days later, Mack was completely transformed.

He looked comfortable and at peace. He could sleep.

He said the horrifying dream had quieted, and in its place were two types of dreams.

15:23 – 15:26

There were comforting dreams and neutral dreams.

In the comforting dreams,

he gets to relive the day he got his discharge papers from the military.

In the neutral dream, a dead soldier comes up to him on a beach.

He doesn’t know who he is, and he says,

“Soon, they, your fellow soldiers, are going to come and get you.”

15:46 – 15:51

Mack was rescued by the dead soldiers he had tried so hard to save.

He had closure. He could close his eyes. He could rest.

He died peacefully, and he died with his dignity.

But just think about it.

The human spirit and that courageous 17-year-old boy fought for 67 years to be free, to be released from that enormous obligation, from that pain,

from that horrible injustice.

His end-of-life experiences didn’t deny his reality, didn’t deny him his war,

but it recast it in such a way that he was finally granted his hard-earned peace.

16:26 – 16:27

I want to end where I began:

my hope was that you’d hear what I have heard from the dying.

Their words are compelling and relevant.

And I hope they leave open the possibility that there is light within the darkness of dying.

Look back on your own life.

16:41 – 16:44

Think of your greatest loss, your greatest comfort, and your greatest wonder

- loss of someone you loved, the familiar, warm hug of a grandparent,

the birth of a child.

What if, at the end of your life, at some appointed hour, the lost return,

distant feelings become familiar,

and meaning is restored?

If any of that is true, then dying is illuminating.

Thank you.

(Applause)