I'll edit this post as I develop more ideas for my outline
"Space, the final NanoPower frontier"
[Insert badly photoshopped picture of the Enterprise]
0)
Nanotech has potential in all areas of space exploration.
Nanotech will not immediately create new fields/devices, but rather, it has the potential to greatly improve existing devices. (especially in the near future)
0.1) Short overview of why we should be trying to use nanotubes (reference their positive charcteristics)
1) Existing use of nanotech in space
1.1) Space Nanotechnology laboratory at MIT (snl.mit.edu) has used nanotehc to build nanoscale components of NASA observers [Chandra X-Ray and others]
2) Nanoelectrical systems
2.1) Power systems, PMAD [Power Management and Distribution] systems
2.1.1) Applications in nuclear powersystems
2.1.2) Applications in solar powersystems
2.2) MEMS [Microelectromagnetic systems]: Combine microchips with electronics that would use them.
2.2.1) Important spacecraft electronics could be made smaller.
2.2.2) Micro-probes for imaging extraterrestrial objects
3) Nanocomposites as a spacecraft building material
3.1) "Armoring" against space debris
3.2) Useful in dealing with stresses of launch?
4) Types of space exploration; usage of nanotechnologies there
4.1) Deep-space travel
4.2) Colonization of extraterrestrial worlds
4.3) Surface exploration [using nanotech]
4.3.1) by humans
4.3.2) by probes/robots
4.3.2.1) Nanotechnology could enable you to build very small probes.
5) Use of nanotubes to transport stuff from Earth to low-Earth orbit
5.1) A space elevator?
5.1.1) Exciting theoretical possibility, but even the theory isn't completely ironed out yet.
* Many parts of this presentation will reference concepts discussed during Ryne Rafaelle's two presentations way back in Week 2. My notes are on this blog, and I still have access to the powerpoints, so memory of that material shouldn't be an issue.
Wednesday, April 30, 2008
Personal Interest Presentation
This is the "final exam" for the Frontiers of Science class.
The idea here is to zoom on on sub-area(s) of any of the four topics covered, specifically sub-area(s) that especially interest you
I am focusing on the use of nanotechnology and NanoPower in current and future space exploration. To put it more lyrically,
"Space, the final NanoPower frontier"
To be honest, good sci-fi works can have quite a potential to be inspiring as to the course of scientific advancement.
A centerprice of our classroom is a widevision screen that, among other things, could display 4 PowerPoint-type slides at a time, and we have a PowerPoint template file designed to work with that.
The crux of my Personal Interest Presentation s going to be one of those, which is a process I've also used for the three topic summaries I've done to date.
The format is one I understand, and I'm also using it because I'll hopefully be able to focus on content rather on the logistical & production issues of a more exotic format
The idea here is to zoom on on sub-area(s) of any of the four topics covered, specifically sub-area(s) that especially interest you
I am focusing on the use of nanotechnology and NanoPower in current and future space exploration. To put it more lyrically,
"Space, the final NanoPower frontier"
To be honest, good sci-fi works can have quite a potential to be inspiring as to the course of scientific advancement.
A centerprice of our classroom is a widevision screen that, among other things, could display 4 PowerPoint-type slides at a time, and we have a PowerPoint template file designed to work with that.
The crux of my Personal Interest Presentation s going to be one of those, which is a process I've also used for the three topic summaries I've done to date.
The format is one I understand, and I'm also using it because I'll hopefully be able to focus on content rather on the logistical & production issues of a more exotic format
Monday, April 28, 2008
Medical Imaging
X-rays: very good for imaging bone, but not soft tissue
Still useful on kidneys - would see kidney stones
Before Roentgen's X-ray discovery, no way to look at body besides cutting it open
Some medical imaging methods (like X-ray) provide a picture, some (like ultrasound) provide a real-time picture
Where in the electromagnetic spectrum do we look?
Two parameters: resolution and attenuation (attenuation: how the radiation changes as goes through the body during the imaging process). Often, it is a tradeoff between the two.
Both of these parameters are a function of wavelength
We can't medical-image with visible light, since the human body is opaque to it
-How X-rays work-
Tungsten cathode: bombards tungsten target with electrons, the target is hooked up to a copper anode
X-rays produced by the electron/target collision
X-rays are 2D representation of a 3D object; thus aren't good for analyzing abnormal structures where you aren't sure what structure to expect
-Computer tomography-
Uses X-rays
Takes 2D images of a 3D volume (like the human body) - "slices" - target needs to be aligned straight with the beam generator
Several of these images, aggregated into one picture
Backprojection: Looking at the same slice of the body from different angles
-Positron emission tomography (PET)-
Proton --> Neutron + Neutrino + Positron
[Part of radioactive decay: inject radioactive agent during PET to cause this to happen]
Positron + Electron: antimatter annihilation that produces a gamma-ray signature. The latter is detected
Areas of higher metabolism (like cancer tumors) give off a stronger signature
-MRI-
This has been covered before
Hydrogen protons on particular become excited in a strong magnetic field, then turn the field off, which thus changes the signal behavior.
You image based on this.
-Ultrasound-
Useful on pregnant women because it's safe/not radioactive
Has other uses as well
We know the speed of sound in the body because know the speed of sound in water, and the body is mostly water
You image based on the ultrasound's echoes
Doppler ultrasound can image blood flow
Visible Human Project: part of NIH
Gathers data about human body parts that can be use din designing and tweaking these imaging processes
modality: a term for a different medical-imaging process
Often get complementary images from using different processes on the same object
Could look at these images side-by-side or no top of each other
Images often pseudocolored to help humans read + analyze them
Simulated/"phantom" images are often useful for gathering general information
Still useful on kidneys - would see kidney stones
Before Roentgen's X-ray discovery, no way to look at body besides cutting it open
Some medical imaging methods (like X-ray) provide a picture, some (like ultrasound) provide a real-time picture
Where in the electromagnetic spectrum do we look?
Two parameters: resolution and attenuation (attenuation: how the radiation changes as goes through the body during the imaging process). Often, it is a tradeoff between the two.
Both of these parameters are a function of wavelength
We can't medical-image with visible light, since the human body is opaque to it
-How X-rays work-
Tungsten cathode: bombards tungsten target with electrons, the target is hooked up to a copper anode
X-rays produced by the electron/target collision
X-rays are 2D representation of a 3D object; thus aren't good for analyzing abnormal structures where you aren't sure what structure to expect
-Computer tomography-
Uses X-rays
Takes 2D images of a 3D volume (like the human body) - "slices" - target needs to be aligned straight with the beam generator
Several of these images, aggregated into one picture
Backprojection: Looking at the same slice of the body from different angles
-Positron emission tomography (PET)-
Proton --> Neutron + Neutrino + Positron
[Part of radioactive decay: inject radioactive agent during PET to cause this to happen]
Positron + Electron: antimatter annihilation that produces a gamma-ray signature. The latter is detected
Areas of higher metabolism (like cancer tumors) give off a stronger signature
-MRI-
This has been covered before
Hydrogen protons on particular become excited in a strong magnetic field, then turn the field off, which thus changes the signal behavior.
You image based on this.
-Ultrasound-
Useful on pregnant women because it's safe/not radioactive
Has other uses as well
We know the speed of sound in the body because know the speed of sound in water, and the body is mostly water
You image based on the ultrasound's echoes
Doppler ultrasound can image blood flow
Visible Human Project: part of NIH
Gathers data about human body parts that can be use din designing and tweaking these imaging processes
modality: a term for a different medical-imaging process
Often get complementary images from using different processes on the same object
Could look at these images side-by-side or no top of each other
Images often pseudocolored to help humans read + analyze them
Simulated/"phantom" images are often useful for gathering general information
Wednesday, April 23, 2008
Outlines [Vision And Mind example]
This came to mind as I'm working on Topic Summary #3:
An outline is a good way to prep for doing the topic summary, but it's also a good way to think about the topic, in general.
So here goes:
-Vision And Mind-
* the physiology of the vision system
** details on structure of the eye
*** Rods & Cones
** details on the visual cortex and on V1 through V5
*** where it's located compared to the rest of the brain.
** "lateral inhibition", and how it accentuates the edges of an object
** eye movements
*** depends on the size of the object/scene to be visualized (the object/scene to be visualized is counted in degrees squared)
*** oculomotor system
*** saccades
*** various ways of tracing a moving object
** field-of-view vs. acuity conflict
-------------------------------------------------------
* the psychology of the vision system
** How can we visualize brain psychology?
by various medical-imaging techniques:
*** EEG
*** MRI vs. fMRI, differences
** How certain optical illusions work
*** really should be 'neural illusions'?
*** name a few big-name optical illusions & discuss them
----------------------------------------------------------------
* relation to other senses
** brain lobe where inputs from other senses 'meet'
** use of visual system to compensate for other sight loss
** use of other sensory systems to compensate for vision loss
An outline is a good way to prep for doing the topic summary, but it's also a good way to think about the topic, in general.
So here goes:
-Vision And Mind-
* the physiology of the vision system
** details on structure of the eye
*** Rods & Cones
** details on the visual cortex and on V1 through V5
*** where it's located compared to the rest of the brain.
** "lateral inhibition", and how it accentuates the edges of an object
** eye movements
*** depends on the size of the object/scene to be visualized (the object/scene to be visualized is counted in degrees squared)
*** oculomotor system
*** saccades
*** various ways of tracing a moving object
** field-of-view vs. acuity conflict
-------------------------------------------------------
* the psychology of the vision system
** How can we visualize brain psychology?
by various medical-imaging techniques:
*** EEG
*** MRI vs. fMRI, differences
** How certain optical illusions work
*** really should be 'neural illusions'?
*** name a few big-name optical illusions & discuss them
----------------------------------------------------------------
* relation to other senses
** brain lobe where inputs from other senses 'meet'
** use of visual system to compensate for other sight loss
** use of other sensory systems to compensate for vision loss
Halstone's electron-microscope lab
This lab uses TEMs (tunneling electron microscopes)
Can't use glass lenses to focus electron beams; have to use magnetic lenses; this *is* a tradeoff
X-ray microscopes don't have the quality we want yet, gamma-ray microscopes are still atleast a few years down the road
Mosely's law - 1914: hit something w/ electrons and produce X-rays
* Radiation issues inherent
* Depending on the energy level of the X-rays, you can tell what element emitted it
Electron gun fires a beam down the main column
Tungsten filament is excited and
200,000 volts
200,000 kilo-electron volts
Moving at ~ 1/3 the speed of light, need to use Relativity-based equations
Specimen in center of column, on the end of a handle
Whole column has to be under vacuum
One magnetic lens controls spot size of beam; there are several other lenses aswell
Objective lens nearest the bottom of the column; it's what actually produces the image.
^ How do you *see* electrons?
At bottom of column, a screen covered with zinc sulfide...Electrons put some part(s) of that into an excited state, and they flouresce green.
Green-ness caught by film
X-ray detectors chilled to liquid-nitrogen temperatures.
This can be used to analyze what elements ar ein each section of the sample
Specimens extremely small (~3mm diameter, and very thin (<200nm, even thinner for heavy elements))
What is 2,000,000x magnification? A person magnified this much would be two thousand miles tall?
What is a nanometer versus a meter? Size of a golf ball versions the size of the Earth
Electron microscopes very sensitive. Even sound waves form talking, etc. can cause the image to 'jump' a bit
Electron diffraction - electron beam scattered by hitting a crystalline structure. Depending on how they scatter, you can determine what the crystal structure is. Often a ring pattern of some sort.
Lattice planes in asbestos are 9 angstroms (.9 nm) apart
Easy to detect dead space in a crystalline structure vs. the location of the atoms themselves
--------
*Scanning electron microscope*
Shorter column
20k eV up to 30k or 40k eV
Secondary electrons kicked off by the sample itself
Can vary distance between sample and electron beam
General good microscope idea: start at low magnification to get an overview, then zoom in
A high frame rate leads to more noise "static" (spend less time scanning a particular pixel)
Low frame rate - less "noise", but takes longer to produce the image
Low voltage; less penetration; should mean more surface detail [and vice versa]
SEM useful for building a picture of where exactly atoms of element X are located throughout the sample
H, He, Li, and Be can't be detected via this X-ray detector equipment
astigmatism: vertical image in separate focus from the horizontal image
Spehrical and chromatic aberation you need different equipment to correct
---
Halstone uses a srtaightforward same (copper+aluminum disk) to calibrate the settings
---
The material you used to prepare the specimen (gold coat, etc), can screw with the view
Can't use glass lenses to focus electron beams; have to use magnetic lenses; this *is* a tradeoff
X-ray microscopes don't have the quality we want yet, gamma-ray microscopes are still atleast a few years down the road
Mosely's law - 1914: hit something w/ electrons and produce X-rays
* Radiation issues inherent
* Depending on the energy level of the X-rays, you can tell what element emitted it
Electron gun fires a beam down the main column
Tungsten filament is excited and
200,000 volts
200,000 kilo-electron volts
Moving at ~ 1/3 the speed of light, need to use Relativity-based equations
Specimen in center of column, on the end of a handle
Whole column has to be under vacuum
One magnetic lens controls spot size of beam; there are several other lenses aswell
Objective lens nearest the bottom of the column; it's what actually produces the image.
^ How do you *see* electrons?
At bottom of column, a screen covered with zinc sulfide...Electrons put some part(s) of that into an excited state, and they flouresce green.
Green-ness caught by film
X-ray detectors chilled to liquid-nitrogen temperatures.
This can be used to analyze what elements ar ein each section of the sample
Specimens extremely small (~3mm diameter, and very thin (<200nm, even thinner for heavy elements))
What is 2,000,000x magnification? A person magnified this much would be two thousand miles tall?
What is a nanometer versus a meter? Size of a golf ball versions the size of the Earth
Electron microscopes very sensitive. Even sound waves form talking, etc. can cause the image to 'jump' a bit
Electron diffraction - electron beam scattered by hitting a crystalline structure. Depending on how they scatter, you can determine what the crystal structure is. Often a ring pattern of some sort.
Lattice planes in asbestos are 9 angstroms (.9 nm) apart
Easy to detect dead space in a crystalline structure vs. the location of the atoms themselves
--------
*Scanning electron microscope*
Shorter column
20k eV up to 30k or 40k eV
Secondary electrons kicked off by the sample itself
Can vary distance between sample and electron beam
General good microscope idea: start at low magnification to get an overview, then zoom in
A high frame rate leads to more noise "static" (spend less time scanning a particular pixel)
Low frame rate - less "noise", but takes longer to produce the image
Low voltage; less penetration; should mean more surface detail [and vice versa]
SEM useful for building a picture of where exactly atoms of element X are located throughout the sample
H, He, Li, and Be can't be detected via this X-ray detector equipment
astigmatism: vertical image in separate focus from the horizontal image
Spehrical and chromatic aberation you need different equipment to correct
---
Halstone uses a srtaightforward same (copper+aluminum disk) to calibrate the settings
---
The material you used to prepare the specimen (gold coat, etc), can screw with the view
Monday, April 21, 2008
How do they work?
Okay, how do these types of medical imaging work?
* Ultrasound
How it works: Bombardment of sound waves above 20,000 hertz (20khZ), 20khz being the upper limit of human hearing
What is actually measured: Ultrasound actually measures the echoes received by the ultrasound machine after they bounce back from hitting body parts.
An electrical pulse transducer in the machine causes it to vibrate at a certain frequency. Likewise, the echoes cause the transducer to vibrate in various ways, converted into electrical pulses which are then converted into a digital image
Advantages: Light if any side effects, very good at imaging soft tissue (vary frequency for different kinds of soft tissue), can produce a "live video" feed during the procedure
* fMRI (Functional Magnetic Resonance Imaging)
How it works: Images the brain and brain activity, though the method would technically work on other areas of the body
What is actually measured: It does this by detecting the increased blood flow typically associated with neural activity
How does it act as a proxy: Neural activity kicks up blood flow, with the areas of increased blood flow being measured
* SPECT
How it works: Radioisotopes fed into body, and the gamma rays are detected by the SPECT equipment
What is actually measured: The rays received by the machine are measured as 2-D images, but are measured form different angles, enabling a 3D image to be produced
How does it act as a proxy?: See info about 3-D reconstruction method above. Also, the radio decay particles behave differently when passing through different body structures, hence the ability for this to measure anything at all
* electromicroscopy
How it works: Magnifies samples to a much higher degree of resolution than is possible with a light microscope.
What is actually measured: Very small/thin sample bombarded with an electron beam. As electrons go through the object (in tunneling electron microscopy, or TEM), they are recorded as how they were 'behaving' as they come out
How does it act as a proxy?: Impediments inside the sample modify the outgoing electron beam.
* Ultrasound
How it works: Bombardment of sound waves above 20,000 hertz (20khZ), 20khz being the upper limit of human hearing
What is actually measured: Ultrasound actually measures the echoes received by the ultrasound machine after they bounce back from hitting body parts.
An electrical pulse transducer in the machine causes it to vibrate at a certain frequency. Likewise, the echoes cause the transducer to vibrate in various ways, converted into electrical pulses which are then converted into a digital image
Advantages: Light if any side effects, very good at imaging soft tissue (vary frequency for different kinds of soft tissue), can produce a "live video" feed during the procedure
* fMRI (Functional Magnetic Resonance Imaging)
How it works: Images the brain and brain activity, though the method would technically work on other areas of the body
What is actually measured: It does this by detecting the increased blood flow typically associated with neural activity
How does it act as a proxy: Neural activity kicks up blood flow, with the areas of increased blood flow being measured
* SPECT
How it works: Radioisotopes fed into body, and the gamma rays are detected by the SPECT equipment
What is actually measured: The rays received by the machine are measured as 2-D images, but are measured form different angles, enabling a 3D image to be produced
How does it act as a proxy?: See info about 3-D reconstruction method above. Also, the radio decay particles behave differently when passing through different body structures, hence the ability for this to measure anything at all
* electromicroscopy
How it works: Magnifies samples to a much higher degree of resolution than is possible with a light microscope.
What is actually measured: Very small/thin sample bombarded with an electron beam. As electrons go through the object (in tunneling electron microscopy, or TEM), they are recorded as how they were 'behaving' as they come out
How does it act as a proxy?: Impediments inside the sample modify the outgoing electron beam.
Types of Medical Imaging
We'll be investigating some forms of medical imaging in class on Wed. (4/25) and Fri. (4/25)
Now what are the different types of medical imaging?
-Things that analyze brain waves, even though they aren't imaging something visible, are still a form of medical imaging-
* such as electroencephalography (EEG)
Many techniques exist that take images of physical body parts...
* X-rays (Classic!)
* Magnetic resonance imaging (MRI) + fMRI
* Positron emission tomography (PET)
* Computerized tomography (CAT)
* Ultrasound
--
endoscopy
* SPECT
* radioisotope-based techniques: nuclear medicine + flouroscopy
* thermography
* electron microscopy
* Raman spectroscopy
* image guided biopsy
* angiography
Now what are the different types of medical imaging?
-Things that analyze brain waves, even though they aren't imaging something visible, are still a form of medical imaging-
* such as electroencephalography (EEG)
Many techniques exist that take images of physical body parts...
* X-rays (Classic!)
* Magnetic resonance imaging (MRI) + fMRI
* Positron emission tomography (PET)
* Computerized tomography (CAT)
* Ultrasound
--
endoscopy
* SPECT
* radioisotope-based techniques: nuclear medicine + flouroscopy
* thermography
* electron microscopy
* Raman spectroscopy
* image guided biopsy
* angiography
Friday, April 18, 2008
Electron Microscopy
Electron MIcroscopes come in two forms: The Tunneling Electron Microscope (TEM) and the Scanning Electron Microscope (SEM).
What is the difference? Both use beams of electrons.
However, the difference resides in the fact that the different types of machines direct the electron beam differently.
Tunneling Electron Microscopes send an electron beam *through* the object. This means theta they are good at gathering details on the inside of the object (which is especially important with cells), and of the surface of small objects.
Scanning Electorn Microscopes send their electron beams along the outside of objects. They are most effective for analyzing the surface of large/thick objects
The STEM (Scanning transmission electron microscope) combines some of the advantageous features of each, logically enough.
There are online simulators, based on Flash, Java, or the like, that give you an impression of how an electron microscope works. By adjusting settings common to an electorn microscope, and chosing from a premade set of 'samples', you see the resultant image.
http://micro.magnet.fsu.edu/primer/java/electronmicroscopy/magnify1/index.html is an example
What is the difference? Both use beams of electrons.
However, the difference resides in the fact that the different types of machines direct the electron beam differently.
Tunneling Electron Microscopes send an electron beam *through* the object. This means theta they are good at gathering details on the inside of the object (which is especially important with cells), and of the surface of small objects.
Scanning Electorn Microscopes send their electron beams along the outside of objects. They are most effective for analyzing the surface of large/thick objects
The STEM (Scanning transmission electron microscope) combines some of the advantageous features of each, logically enough.
There are online simulators, based on Flash, Java, or the like, that give you an impression of how an electron microscope works. By adjusting settings common to an electorn microscope, and chosing from a premade set of 'samples', you see the resultant image.
http://micro.magnet.fsu.edu/primer/java/electronmicroscopy/magnify1/index.html is an example
Wednesday, April 9, 2008
Questions answered by Andy & Jeff
TMS = transcranial magnetic stimulation
Blinded or blindfolded people - this frees up processing capacity in the visual cortex, some of which is used for other types of sensory processing
In deaf people, the auditory cortex probably does something
Same parts of brain for thinking about something, and perceiving it. So thinking about something during a dream may helpyou perceive it when you're awake
During sleep, the memory-forming hippocampus is more-active
Sleep is mental regeneration (see above), as well as physical regeneration
Cramming - does not work for long-term retention
Eye -->LGN --> V1 --> V2 --> V3 --> V4 --> V5
Not always a linear pathway, there are some connections that skip/go backwards in this chain.
The different V's process somewhat different types of signals (have different capacities), but these roles are interconencted. (Removing V4 doesn't
LGN - laterogenetic nucleus of the thalamus
Allan Cowe - vision experiments on monkeys
The brain is to some extent a dynamic self-repairing system
At a certain point, the things [experiments] we want to do are illegal or unethical - Andy Herbert
Don't overdo the computer analogies here in brain psychology
SOme optical illusions are the result of the brain taking necessary processing shortcuts
"Is what we see really there?" - That gets into philosophy
Integrating the senses is important - Sense A compensates for a weakness of Sense B
Normally, the senses paint a complementary picture...very disorienting when they don't
Contrast sensitivity - vision of shadows vs. vision of discrete objects
Different among different species, because different species need visions systems adapted to their different environment
Can see what capacity is missing when a certain section of the brain is gone.
First started relazing this en masse with Civil War musketball-to-the-head injuries
Cortex has higher-order roles than things like the thalamus. Things liek the thalamus handle basic body functions for the most part.
Drugs,and not just the funky illegal ones - have effect on neurotrasmitters.
Range of visual sensitivity amongst normal humans
This may explain how a lot of drugs produce haalucinations and the like
Blinded or blindfolded people - this frees up processing capacity in the visual cortex, some of which is used for other types of sensory processing
In deaf people, the auditory cortex probably does something
Same parts of brain for thinking about something, and perceiving it. So thinking about something during a dream may helpyou perceive it when you're awake
During sleep, the memory-forming hippocampus is more-active
Sleep is mental regeneration (see above), as well as physical regeneration
Cramming - does not work for long-term retention
Eye -->LGN --> V1 --> V2 --> V3 --> V4 --> V5
Not always a linear pathway, there are some connections that skip/go backwards in this chain.
The different V's process somewhat different types of signals (have different capacities), but these roles are interconencted. (Removing V4 doesn't
LGN - laterogenetic nucleus of the thalamus
Allan Cowe - vision experiments on monkeys
The brain is to some extent a dynamic self-repairing system
At a certain point, the things [experiments] we want to do are illegal or unethical - Andy Herbert
Don't overdo the computer analogies here in brain psychology
SOme optical illusions are the result of the brain taking necessary processing shortcuts
"Is what we see really there?" - That gets into philosophy
Integrating the senses is important - Sense A compensates for a weakness of Sense B
Normally, the senses paint a complementary picture...very disorienting when they don't
Contrast sensitivity - vision of shadows vs. vision of discrete objects
Different among different species, because different species need visions systems adapted to their different environment
Can see what capacity is missing when a certain section of the brain is gone.
First started relazing this en masse with Civil War musketball-to-the-head injuries
Cortex has higher-order roles than things like the thalamus. Things liek the thalamus handle basic body functions for the most part.
Drugs,and not just the funky illegal ones - have effect on neurotrasmitters.
Range of visual sensitivity amongst normal humans
This may explain how a lot of drugs produce haalucinations and the like
Friday, April 4, 2008
(4/4/08) Answers to Thought-Provoking Questions
Why do some stars turn into black holes?
Stars that were massive enough turn into black holes when they die.
A dead star doesn't have enough fuel to keep fusion going.
The fusion reaction produces energy and heat that counterbalances the gravitational pull of the star on itself
This is called "hydrostatic equilibrium"
Objects in a system orbit around the center of mass
Galaxies in a cluster kind of orbit each other rather than expanding and spreading out the way the Hubble pattern would predict. SO they become more inclined to collide.
What keeps smaller object in orbit, rather than falling towards the central mass?
* the energy of the small object itself
* orbit is at a point where energy of object balances the energy of gravitational pull
gravitational tides between galaxies can affect orbits if the galaxies are close enough
During a galactic collision, you're likely to have more material falling into a black hole
Time travel very speculative - all of the discussion is theoretical at this point. Some ways time travel might happen:
*Faster-than-light (back in time)
*Travel through wormhole w/o getting destroyed
* Go to similar parallel universe
* Are parallel universes preexisting, or created by the act of time travel
* If parallel universes exist, there would probably be an infinite amount of them, for each branching-off point. If there was a limited amount,how would it be chosen?
* Parallel universmany not just have different history, but different laws of physics
Standard candle - a group of objects with the same brightness.
Different form units of measure such as "solar luminosity"
Standard rod -similar concept with shape
In astronomy, can measure apparent brightness and apparent size.
apparent brightness, apparent size, actual size, actual brightness and distance - if you knoow some fo these, you can figure out the rest
"Do black holes ever go away?"
The massive ones are around forever,the smaller ones are likely to disappear
The Drake Equation - equation that takes several factors; determines the probability of intelligent life; however, you have to make assumptions
Stars that were massive enough turn into black holes when they die.
A dead star doesn't have enough fuel to keep fusion going.
The fusion reaction produces energy and heat that counterbalances the gravitational pull of the star on itself
This is called "hydrostatic equilibrium"
Objects in a system orbit around the center of mass
Galaxies in a cluster kind of orbit each other rather than expanding and spreading out the way the Hubble pattern would predict. SO they become more inclined to collide.
What keeps smaller object in orbit, rather than falling towards the central mass?
* the energy of the small object itself
* orbit is at a point where energy of object balances the energy of gravitational pull
gravitational tides between galaxies can affect orbits if the galaxies are close enough
During a galactic collision, you're likely to have more material falling into a black hole
Time travel very speculative - all of the discussion is theoretical at this point. Some ways time travel might happen:
*Faster-than-light (back in time)
*Travel through wormhole w/o getting destroyed
* Go to similar parallel universe
* Are parallel universes preexisting, or created by the act of time travel
* If parallel universes exist, there would probably be an infinite amount of them, for each branching-off point. If there was a limited amount,how would it be chosen?
* Parallel universmany not just have different history, but different laws of physics
Standard candle - a group of objects with the same brightness.
Different form units of measure such as "solar luminosity"
Standard rod -similar concept with shape
In astronomy, can measure apparent brightness and apparent size.
apparent brightness, apparent size, actual size, actual brightness and distance - if you knoow some fo these, you can figure out the rest
"Do black holes ever go away?"
The massive ones are around forever,the smaller ones are likely to disappear
The Drake Equation - equation that takes several factors; determines the probability of intelligent life; however, you have to make assumptions
Wednesday, April 2, 2008
E = mc^2
E = mc^2 actually refers to particles without motion, plus the energy of motion
With the energy of motion, you can have mass of 0, and still have energy
Applies to many different areas of the universe
E = mc^2: A recipe for converting matter to energy and vice versa - requires energy to make such a conversion, and a lot of energy
Energy doesn't take up much space, takes up more space when converted into matter
With the energy of motion, you can have mass of 0, and still have energy
Applies to many different areas of the universe
E = mc^2: A recipe for converting matter to energy and vice versa - requires energy to make such a conversion, and a lot of energy
Energy doesn't take up much space, takes up more space when converted into matter
(4/2/08) - From Big Bang to Black Holes
Most of what we know about the universe comes from our analysis of electromagnetic radiation (i.e. light)
Light is like a wave
Electronic wave and magnetic wave oscillate together
Black hole in center of galaxy = 1 million times the mass of the sun
The Sun = a basic unit of measurement
ergs = g*cm^2 / second^2
Solar luminosity = 3.8 * 10^33 ergs/s
Mass: 2 * 10^30 kg
Age of universe: 13.7 billion years
Speed of light = 3 * 10^8 m/s
parsec = 3.26 light years
Special Relativity
2 main components:
* The laws of physics ar ehte same in any inertial frame
* The speed of light is the same for all observers in an inertial frame
Spacetime is 4-dimensional
A frame in which unaccelerated objects move in straight lines is an inertial frame
A globally inertial frame is a frame that covers all spacetime
Addition of speeds
Walking 5 mph, Bus 30mph, difference 25mph
Rocket 100,000km/s, Light 300,000km/s
Difference appears differently because the observers involved see spacetime differently
Time dilation: the time lapse between 2 events changes from one observer to another; it is dependent on the relative speed of the observers
Lorentz contraction - the dimensions of an object as measured by one observer may be smaller than that of another observer
This also has implications for how gravity works
Newtonian gravity: F = G (m1 m2)/r^2
General Relativity: mass-energy causes spacetime to curve
Objects, including light, follow the shortest path in curved spacetime
Gravity = curvature of spacetime
Clocks more slowly the closer they are to a gravitational mass
Sun's gravity would bend light coming from background stars
Time slows near any massive body. Slows down even near Earth. [albeit in very small amounts - 4 parts in 10 billion]
The angular momentum of a rotating body drags space into a tornado-like whirl around it. (small whirl
Will see object differently if a mass is on the way. This is called a "gravitational lens".
When the gravitational lens is perfectly aligned with the background object, the background object is modified into an Einstein Ring
Black holes - so much mass in such a small space that the spacetime warp is extreme
Nothing can escape, not even light
Detect black holes by their gravitational effect on nearby object
Stars, specially those near Galactic Center, are detected orbiting it
Supermassive black holes probably exist at the centers of most galaxies
Called galactic nuclei
Could have come about or become larger during galactic mergers
Collision of two black holes is the most violent event in the universe
* Produces wild vibrations of warped spacetime
Black holes related to their host galaxies: "chicken & egg" problem
* galaxy formation far enough back in time that we can't really tell
* Hypothesis: growing together
What happens in a black hole, stays on a black hole. This is how black holes build mass.
Light is like a wave
Electronic wave and magnetic wave oscillate together
Black hole in center of galaxy = 1 million times the mass of the sun
The Sun = a basic unit of measurement
ergs = g*cm^2 / second^2
Solar luminosity = 3.8 * 10^33 ergs/s
Mass: 2 * 10^30 kg
Age of universe: 13.7 billion years
Speed of light = 3 * 10^8 m/s
parsec = 3.26 light years
Special Relativity
2 main components:
* The laws of physics ar ehte same in any inertial frame
* The speed of light is the same for all observers in an inertial frame
Spacetime is 4-dimensional
A frame in which unaccelerated objects move in straight lines is an inertial frame
A globally inertial frame is a frame that covers all spacetime
Addition of speeds
Walking 5 mph, Bus 30mph, difference 25mph
Rocket 100,000km/s, Light 300,000km/s
Difference appears differently because the observers involved see spacetime differently
Time dilation: the time lapse between 2 events changes from one observer to another; it is dependent on the relative speed of the observers
Lorentz contraction - the dimensions of an object as measured by one observer may be smaller than that of another observer
This also has implications for how gravity works
Newtonian gravity: F = G (m1 m2)/r^2
General Relativity: mass-energy causes spacetime to curve
Objects, including light, follow the shortest path in curved spacetime
Gravity = curvature of spacetime
Clocks more slowly the closer they are to a gravitational mass
Sun's gravity would bend light coming from background stars
Time slows near any massive body. Slows down even near Earth. [albeit in very small amounts - 4 parts in 10 billion]
The angular momentum of a rotating body drags space into a tornado-like whirl around it. (small whirl
Will see object differently if a mass is on the way. This is called a "gravitational lens".
When the gravitational lens is perfectly aligned with the background object, the background object is modified into an Einstein Ring
Black holes - so much mass in such a small space that the spacetime warp is extreme
Nothing can escape, not even light
Detect black holes by their gravitational effect on nearby object
Stars, specially those near Galactic Center, are detected orbiting it
Supermassive black holes probably exist at the centers of most galaxies
Called galactic nuclei
Could have come about or become larger during galactic mergers
Collision of two black holes is the most violent event in the universe
* Produces wild vibrations of warped spacetime
Black holes related to their host galaxies: "chicken & egg" problem
* galaxy formation far enough back in time that we can't really tell
* Hypothesis: growing together
What happens in a black hole, stays on a black hole. This is how black holes build mass.
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