The western media are at it again, pushing the panic and the apathy buttons all at once.
Here are some informed, well-written, intelligible discussions on what the WHO was calling swine flu and is now calling A(H1/N1):
1) Interview with the US CDC virus chief.
2) Explanation of the WHO's pandemic scale
3) More intelligent discussion of the epidemic
4) Science Insider look at the activity of health agencies around the world
What should you do?
Stop reading or listening to NBC, CBS, CNN, etc. Seriously.
Start reading the posts on the CDC's site:
http://www.cdc.gov/h1n1flu/index.htm
the WHO's site:
http://www.who.int/csr/disease/swineflu/en/index.html
The US government site set up just for this:
http://www.pandemicflu.gov/
Seriously, stop using the major cable and broadcast agencies for news; they're for entertainment, not news.
Here are some reasons for concern:
1) This particular strain has not been seen in humans. Therefore, no humans have built an immunity (although there may be unexpected sources of an immunity in random people). There are many reasons this lack of immunity would not cause every infected person to die.
2) The spread of this virus is faster than we've seen before.
3) In the US, if this does go pandemic (which seems to be the expectation), we don't have the health care infrastructure to handle a lot of sick people all at once.
4) H1N1 has started migrating between humans. If it is or becomes efficient enough in transferring, we may be too far behind the curve to do more than mitigate its effects.
5) Relatively young, healthy people are succumbing to this. Usually only the elderly, the already ill, and the very young die from influenza.
6) The people most likely to get sick (low income workers, part-time workers, and mothers of school-aged children, etc.) are also the least likely to have any paid sick-leave. Therefore, they're the most likely to continue to go to work (and send their children to school) even if they are sick. Guess who is at the very bottom of the paid sick leave ladder...food service workers.
Here are some reasons for hope:
1) Cleanliness is the best prevention, and cleanliness is easy.
2) The CDC in the US and the WHO and its member states are as aware and on top of this as they can be.
3) Most cases outside of Mexico have been relatively mild. It's not clear why.
Some Dos and Don'ts:
Do:
Wash thoroughly; keep clean.
Stay home if you feel sick.
Stock up at least two weeks worth of food and water. Seriously.
Make sure your prescriptions have recently been filled.
Make sure you are stocked on other medications.
Learn how you can help in a public health emergency. Contact your local/county/state health agency if you think you might have anything at all to contribute.
Don't:
Don't listen to Joe Biden.
Don't panic about pork. If you like pork, cook it well and eat it.
Don't rush out to buy antibacterials. Influenza is a virus, antibacterials won't do anything to stop it.
Don't panic. Prepare.
Thursday, April 30, 2009
Monday, April 27, 2009
Are academic institutions out-dated and in need of complete overhall?
A question was raised by this op-ed in the NY-Times. Basically, they question the validity of the current (and well-established) method of educating graduate students and undergraduate students in the US and probably western societies. Right now (generally), graduate students focus so narrowly that they cannot actually find a job after graduation other than with their graduate advisor or someone with whom they've already worked very closely. I've seen many of my graduate student colleagues move into industry, where they can actually find a job, can be paid something reasonable, but do something completely different from their graduate work.
In many ways, that's all fine and dandy.
I was working on a proposal the other day and my supervisor's supervisor told me, "while you're writing this, think about what the community will lose if you aren't funded." Hmm.... Honestly, the scientific community will lose little, and the general community will lose less. The work I do is rather narrowly focused (although it is less narrow than some of my colleagues' work) and not generally applicable to the problems of society as a whole.
While I strongly feel that the pursuit of knowledge for knowledge's sake is a necessary aspect of human nature, I don't feel that what I do will fundamentally alter anyone's life (except my own, my wife's, and my son's---simply because I do contribute some little bit of money for food to this familial experiment).
That's not to say I couldn't contribute more directly to society. For instance, my research requires a pretty strong understanding of energy transfer. If I could find a position that would allow me to apply that understanding to, say, alternative energy applications, I'd jump on it in a heartbeat because my knowledge could be applicable to peoples' daily lives.
And therein's the rub. In the US---and I suspect many other societies---we as a whole, expect knowledge to be instantly applicable to daily life. If that knowledge is not, we denigrate those scientists or engineers who pursue it for its own sake. Even some of the seekers are uncomfortable when there is no obvious short-term benefit from the knowledge. Of course, the long-term benefits of pure research are much greater than is generally imagined, but it's hard to see so far into the future when there are so many short-term problems to solve.
Back to the original question: are our education institutions out-dated and useless?
I don't think they're useless, but I do think there are things that need to be corrected, and I agree with a lot that is said in the article. The changes suggested are drastic but this is definitely something to think about.
In many ways, that's all fine and dandy.
I was working on a proposal the other day and my supervisor's supervisor told me, "while you're writing this, think about what the community will lose if you aren't funded." Hmm.... Honestly, the scientific community will lose little, and the general community will lose less. The work I do is rather narrowly focused (although it is less narrow than some of my colleagues' work) and not generally applicable to the problems of society as a whole.
While I strongly feel that the pursuit of knowledge for knowledge's sake is a necessary aspect of human nature, I don't feel that what I do will fundamentally alter anyone's life (except my own, my wife's, and my son's---simply because I do contribute some little bit of money for food to this familial experiment).
That's not to say I couldn't contribute more directly to society. For instance, my research requires a pretty strong understanding of energy transfer. If I could find a position that would allow me to apply that understanding to, say, alternative energy applications, I'd jump on it in a heartbeat because my knowledge could be applicable to peoples' daily lives.
And therein's the rub. In the US---and I suspect many other societies---we as a whole, expect knowledge to be instantly applicable to daily life. If that knowledge is not, we denigrate those scientists or engineers who pursue it for its own sake. Even some of the seekers are uncomfortable when there is no obvious short-term benefit from the knowledge. Of course, the long-term benefits of pure research are much greater than is generally imagined, but it's hard to see so far into the future when there are so many short-term problems to solve.
Back to the original question: are our education institutions out-dated and useless?
I don't think they're useless, but I do think there are things that need to be corrected, and I agree with a lot that is said in the article. The changes suggested are drastic but this is definitely something to think about.
Friday, April 17, 2009
Fast-twitch, slow-twitch, dark meat, white meat...
At Easter supper, DF-i-L explained to DS that the dark meat from the turkey he was consuming is from slow-twitch muscles while white-meat is from fast-twitch muscles (or at least that's the way I remember it). DGpJ said he didn't think DF-i-L knew what he was talking about, so I was asked to look it up and settle the controversy.
DF-i-L is correct.
Definitions:
Slow Twitch (Type I)
The slow muscles are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.
Fast Twitch (Type II)
Because fast twitch fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force.
A turkey or chicken stands on its legs all the time but doesn't do much more than that. It needs slow, endurance-trained, efficient muscles in its legs. The dark meat in the legs contains lots of blood vessels that the muscles need for near-continuous operation.
The white meat (breasts in a turkey, for example) muscles require quick bursts of activity, but not much in the way of the oxygen-carrying myoglobin necessary for long-term usage.
By the way, flying birds (dove, pigeon, wild geese, etc.) have dark meat in pretty much all of their bodies. If you like the white meat of fowl, you'll have to look for chicken, turkey, pheasant, etc. If you like dark meat from fowl, you'll find leaner meats in geese (not domesticated; avoid the skin where all the fat is stored), duck (not domesticated; avoid the skin where all the fat is stored), or other migratory game bird.
DF-i-L is correct.
Definitions:
Slow Twitch (Type I)
The slow muscles are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.
Fast Twitch (Type II)
Because fast twitch fibers use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed than slow muscles. However, they fatigue more quickly. Fast twitch fibers generally produce the same amount of force per contraction as slow muscles, but they get their name because they are able to fire more rapidly. Having more fast twitch fibers can be an asset to a sprinter since she needs to quickly generate a lot of force.
A turkey or chicken stands on its legs all the time but doesn't do much more than that. It needs slow, endurance-trained, efficient muscles in its legs. The dark meat in the legs contains lots of blood vessels that the muscles need for near-continuous operation.
The white meat (breasts in a turkey, for example) muscles require quick bursts of activity, but not much in the way of the oxygen-carrying myoglobin necessary for long-term usage.
By the way, flying birds (dove, pigeon, wild geese, etc.) have dark meat in pretty much all of their bodies. If you like the white meat of fowl, you'll have to look for chicken, turkey, pheasant, etc. If you like dark meat from fowl, you'll find leaner meats in geese (not domesticated; avoid the skin where all the fat is stored), duck (not domesticated; avoid the skin where all the fat is stored), or other migratory game bird.
Tuesday, April 14, 2009
Bloody morning
MOM!!!
It's ~1 AM and this instant-alert sounds through the house. (Better than a fire alarm, I assure you.)
Last night was her turn, it's my turn now.
MOM!!! I HAVE A BLOODY NOSE!!!
I'm there, shuffling the boy into the bathroom where the floor can be cleaned, the light can be lit, and the tissue paper can be had. Yep, he has a bloody nose.
After calming the panic, the solution is easy. Pinch the nose, cool and contract the blood vessels with wet tissue paper. And more calming. Calming is the most important.
"What causes a bloody nose?"
Oh, boy. We'll look it up tomorrow. Sometimes it's because you haven't had enough water, sometimes it's because you're picking your nose too much, sometimes it's because you rub your nose too much, sometimes it just happens.
Calmed, cleaned, and shirt changed. Time to go back to bed.
I wonder if I can ever make those deep breathing exercises actually put me to sleep....
I HAVE A BLOODY NOSE AGAIN!
It's 3:30 AM. He is much more calm about it this time. Calm, pinch, wet, calm, clean, back to bed. We'll look it up tomorrow.
"What if the government people who make the computers didn't know what causes bloody noses when they made the computers?"
Oh, boy. So many things to clarify. Not enough sleep. Explain a little about the internet to a 6-year-old at 3:30 AM after two bloody noses and too little sleep.
7:00 AM. We only have 38 minutes to get dressed, make breakfast, and get to the bus stop. For any normal human, this is entirely possible with extra time to read the morning news and maybe even comment on someone's blog. For a super-inquisitive, overly-tired, 6-year-old, it's barely enough time to change into clothing. For a twice-waked 32-year-old grouch, it's barely enough time to get out of bed. I did get my caffeine made without doing anything too stupid, which means I've accomplished a fair amount and may take the rest of the day off.
Enough with the theatrics. Why the bloody noses?
How to stop a bloody nose? If it's just a one-time (or occasional) bloody nose that isn't due to injury, nothing more than keeping the nose elevated above the heart, cooling and compressing the ruptured blood vessels (to encourage clotting), and, probably most importantly, staying calm is required.
Do not tilt the head back, as this will allow the blood to flow into the sinuses, into the airway, and down the throat; none of those are places blood should be. Do not tilt the head too far forward, as this will allow more blood to flow, discouraging clotting. Do NOT lower the head below the level of the heart, as gravity will work against instead of with you and allow even more blood to flow, keeping the blood vessels warm and the coagulation from happening.
Literally and figuratively, keep a level head, and compress and cool those blood vessels.
If more than the occasional bloody nose is experienced, there are some home remedies that may or may not work. As a child, we used goldenseal for all kinds of clotting needs. Some people use (by imbibing or by topical application) chili pepper to open up their sinuses, relieving excess pressure. Just avoid excessive response; a little bit of something will help, but too much may cause other irritations or worsen the problem.
If nose bleeds are a regular part of your life, it may be a good idea to speak with your doctor about the problem.
It's ~1 AM and this instant-alert sounds through the house. (Better than a fire alarm, I assure you.)
Last night was her turn, it's my turn now.
MOM!!! I HAVE A BLOODY NOSE!!!
I'm there, shuffling the boy into the bathroom where the floor can be cleaned, the light can be lit, and the tissue paper can be had. Yep, he has a bloody nose.
After calming the panic, the solution is easy. Pinch the nose, cool and contract the blood vessels with wet tissue paper. And more calming. Calming is the most important.
"What causes a bloody nose?"
Oh, boy. We'll look it up tomorrow. Sometimes it's because you haven't had enough water, sometimes it's because you're picking your nose too much, sometimes it's because you rub your nose too much, sometimes it just happens.
Calmed, cleaned, and shirt changed. Time to go back to bed.
I wonder if I can ever make those deep breathing exercises actually put me to sleep....
I HAVE A BLOODY NOSE AGAIN!
It's 3:30 AM. He is much more calm about it this time. Calm, pinch, wet, calm, clean, back to bed. We'll look it up tomorrow.
"What if the government people who make the computers didn't know what causes bloody noses when they made the computers?"
Oh, boy. So many things to clarify. Not enough sleep. Explain a little about the internet to a 6-year-old at 3:30 AM after two bloody noses and too little sleep.
7:00 AM. We only have 38 minutes to get dressed, make breakfast, and get to the bus stop. For any normal human, this is entirely possible with extra time to read the morning news and maybe even comment on someone's blog. For a super-inquisitive, overly-tired, 6-year-old, it's barely enough time to change into clothing. For a twice-waked 32-year-old grouch, it's barely enough time to get out of bed. I did get my caffeine made without doing anything too stupid, which means I've accomplished a fair amount and may take the rest of the day off.
Enough with the theatrics. Why the bloody noses?
- Dry air causes the membranes in the nose to dry out and crack. The blood vessels are right at the surface, so they too dry out and crack.
- Picking or excessive rubbing the nose, especially when dry, will cause the blood vessels to burst.
- High altitude
- Other issues related to actual medical problems.
- Injury
How to stop a bloody nose? If it's just a one-time (or occasional) bloody nose that isn't due to injury, nothing more than keeping the nose elevated above the heart, cooling and compressing the ruptured blood vessels (to encourage clotting), and, probably most importantly, staying calm is required.
Do not tilt the head back, as this will allow the blood to flow into the sinuses, into the airway, and down the throat; none of those are places blood should be. Do not tilt the head too far forward, as this will allow more blood to flow, discouraging clotting. Do NOT lower the head below the level of the heart, as gravity will work against instead of with you and allow even more blood to flow, keeping the blood vessels warm and the coagulation from happening.
Literally and figuratively, keep a level head, and compress and cool those blood vessels.
If more than the occasional bloody nose is experienced, there are some home remedies that may or may not work. As a child, we used goldenseal for all kinds of clotting needs. Some people use (by imbibing or by topical application) chili pepper to open up their sinuses, relieving excess pressure. Just avoid excessive response; a little bit of something will help, but too much may cause other irritations or worsen the problem.
If nose bleeds are a regular part of your life, it may be a good idea to speak with your doctor about the problem.
Saturday, April 11, 2009
Compact Fluorescent Lights: Bad for the environment or just more posturing by boneheads?
I'm sure you can guess the answer from the title of this post, but I should still go through the motions. :)
I saw this article today, which argues that CFLs are not as good for energy consumption as advertised due to the way certain components within the bulb affect the actual power draw vs the observed power draw. In short, CFLs take a little less than 100% more energy than claimed because of the way the electronics are built. This is mostly true (I haven't checked the actual values, just the basic physics/electronics), but you won't see the cost; it's a loss to the power company.
Does this mean the CFLs are another "greenwashing" for all us gullible fools out there who don't know anything and just glom onto whatever feel-good behavior is the fad-of-the-hour?
We can use math to answer this question.
Let's take the example of a 100 watt incandescent bulb most of you probably have in your house somewhere. I can easily find a 23 W CFL that outputs as much light as a 100 W incandescent. The CFL costs $2.00 per bulb, while the incan costs $0.28. The CFL is rated to last 8,000 hours. The incan is rated to last 1950 hours.
Assuming typical usage of 3 hours/day, we can expect the CFL to last 7.3 years and the incan to last 1.78 years. The difference in rated hours means the cost of replacing those incans would add up to $1.15 over the life of the CFL.
Let's go back to that article and assume the actual power usage of the CFL is 46 W instead of 23 as advertised. 46 W *8000 hours = 368000 Wh over the lifetime of the bulb. That's 368 kWh. For the incans, the usage would be 100 W * 8000 hours (assume we instantly replace the incan after it burns out and use the next ones until we reach 8000 hours of use) = 800000 Wh, 800 kWh.
The average cost of electricity in the US is about $0.11/kWh. The lifetime cost of the electricty (of which you'll only see ~50%) CFL is $40.48, giving a total cost of $42.48 (except your cost is only $22.24 because the extra power is dissipated in the power lines). The incan electricity cost is $88.00 (you'll see all of this cost), giving a total cost of $89.15.
Okay, great, so a CFL still uses less energy and the problem with the power can be fixed with a couple of additional electronics---if you're handy with a soldering iron, you could do this yourself.
What about the mercury problem you've heard so much about recently?
Well, a first generation CFL has about 4 mg of mercury, none of which is released to the environment if the bulb is not broken. For comparison, old thermometers contain about 500 mg of mercury. Newer CFLs have 1.4 to 2.5 mg of mercury per bulb. Incandescents have none.
Does this mean we should stop allowing CFLs because of the mercury problem?
No. Once again, some simple math can answer the problem.
First, as the CFL is used, the mercury vapor becomes chemically bound to the glass, leaving only about 14% to be released, assuming breakage, at the end of the life of the bulb. The EPA (this links to a PDF) estimates that if all 290 million CFLs sold in 2007 were destroyed in a landfill (each one broken), they would add about 0.16 metric tons of mercury to the environment. That's 0.16 per cent of the mercury released by humans.
Electricity generation is the main source of mercury emissions in the US. The average mercury emissions from electricity generation in the US is 0.012 mg/kWh. The CFL above would, if broken and assuming 4 mg of mercury in the original bulb, add about 0.012*368+0.14*4 = 4.98 mg mercury. The incandescent bulbs would produce 0.012*800 = 9.6 mg mercury. Here, the total electricity use of the CFL should be used, rather than the 23 Watts advertised.
Again:
There's absolutely no reason not to go to CFL. Also, many places are recycling the CFLs for free now, which takes care of the "mercury problem" as well. The bright (ha!) ones among you will notice that even if you broke the CFL right after you bought it (using zero electricity), you won't reach the amount of mercury released due to electricity generation needed to run the incandescent bulb for 8000 hours. Even if you were a moron and bought two CFLs, broke one and used the other, you'd still release less mercury.
Note that I have not discussed the energy costs in producing the bulbs. I don't know those numbers and don't feel like looking them up right now. I am sure it takes more energy to make the CFLs right now, but am NOT sure that extra energy cost is enough to make up the difference in energy or mercury costs compared with the incandescent bulbs.
I saw this article today, which argues that CFLs are not as good for energy consumption as advertised due to the way certain components within the bulb affect the actual power draw vs the observed power draw. In short, CFLs take a little less than 100% more energy than claimed because of the way the electronics are built. This is mostly true (I haven't checked the actual values, just the basic physics/electronics), but you won't see the cost; it's a loss to the power company.
Does this mean the CFLs are another "greenwashing" for all us gullible fools out there who don't know anything and just glom onto whatever feel-good behavior is the fad-of-the-hour?
We can use math to answer this question.
Let's take the example of a 100 watt incandescent bulb most of you probably have in your house somewhere. I can easily find a 23 W CFL that outputs as much light as a 100 W incandescent. The CFL costs $2.00 per bulb, while the incan costs $0.28. The CFL is rated to last 8,000 hours. The incan is rated to last 1950 hours.
Assuming typical usage of 3 hours/day, we can expect the CFL to last 7.3 years and the incan to last 1.78 years. The difference in rated hours means the cost of replacing those incans would add up to $1.15 over the life of the CFL.
Let's go back to that article and assume the actual power usage of the CFL is 46 W instead of 23 as advertised. 46 W *8000 hours = 368000 Wh over the lifetime of the bulb. That's 368 kWh. For the incans, the usage would be 100 W * 8000 hours (assume we instantly replace the incan after it burns out and use the next ones until we reach 8000 hours of use) = 800000 Wh, 800 kWh.
The average cost of electricity in the US is about $0.11/kWh. The lifetime cost of the electricty (of which you'll only see ~50%) CFL is $40.48, giving a total cost of $42.48 (except your cost is only $22.24 because the extra power is dissipated in the power lines). The incan electricity cost is $88.00 (you'll see all of this cost), giving a total cost of $89.15.
Okay, great, so a CFL still uses less energy and the problem with the power can be fixed with a couple of additional electronics---if you're handy with a soldering iron, you could do this yourself.
What about the mercury problem you've heard so much about recently?
Well, a first generation CFL has about 4 mg of mercury, none of which is released to the environment if the bulb is not broken. For comparison, old thermometers contain about 500 mg of mercury. Newer CFLs have 1.4 to 2.5 mg of mercury per bulb. Incandescents have none.
Does this mean we should stop allowing CFLs because of the mercury problem?
No. Once again, some simple math can answer the problem.
First, as the CFL is used, the mercury vapor becomes chemically bound to the glass, leaving only about 14% to be released, assuming breakage, at the end of the life of the bulb. The EPA (this links to a PDF) estimates that if all 290 million CFLs sold in 2007 were destroyed in a landfill (each one broken), they would add about 0.16 metric tons of mercury to the environment. That's 0.16 per cent of the mercury released by humans.
Electricity generation is the main source of mercury emissions in the US. The average mercury emissions from electricity generation in the US is 0.012 mg/kWh. The CFL above would, if broken and assuming 4 mg of mercury in the original bulb, add about 0.012*368+0.14*4 = 4.98 mg mercury. The incandescent bulbs would produce 0.012*800 = 9.6 mg mercury. Here, the total electricity use of the CFL should be used, rather than the 23 Watts advertised.
Again:
| CFL (26 W) | Incan (100W) | |
| Hg (mg) | 4.98 | 9.6 |
| Electricity (kWh) | 368 | 800 |
| Cost ($) | 42.48 (or $22.24 if we only count your costs) | 89.15 |
| Lifetime (hours) | 8000 | 1950 |
There's absolutely no reason not to go to CFL. Also, many places are recycling the CFLs for free now, which takes care of the "mercury problem" as well. The bright (ha!) ones among you will notice that even if you broke the CFL right after you bought it (using zero electricity), you won't reach the amount of mercury released due to electricity generation needed to run the incandescent bulb for 8000 hours. Even if you were a moron and bought two CFLs, broke one and used the other, you'd still release less mercury.
Note that I have not discussed the energy costs in producing the bulbs. I don't know those numbers and don't feel like looking them up right now. I am sure it takes more energy to make the CFLs right now, but am NOT sure that extra energy cost is enough to make up the difference in energy or mercury costs compared with the incandescent bulbs.
Thursday, April 9, 2009
Raindrops falling on my windshield
Son (in the car, watching the raindrops roll up our windshield as we travel on the freeway):
"Why do the rain drops roll up the windshield instead of down?"
Answer:
Because of the 70 miles per hour winds blowing over the windshield put more upward force on the drops than gravity does.
We can calculate the force this fluid (air) has of the object on the windshield (raindrop). I'm not going to bother doing the calculation right now, but it can be done. We can also calculate the down-ward force applied by the acceleration due to gravity.
The force applied to the rain drop by the wind moving past is larger than the force applied by the acceleration of gravity on the mass of the rain drop. Therefore, the raindrop moves in the direction the wind-force is being applied (there may be other forces, but the are so minor that I'm going to ignore them).
Son's follow-up: "Why do some raindrops go further up than others?"
Because some are larger than others (and therefore catch more wind and do not dry out as quickly), some find a cleaner path than others, some have more wind-force applied to them because of their position on the windshield (not blocked by the wipers, for example).
"Why do the rain drops roll up the windshield instead of down?"
Answer:
Because of the 70 miles per hour winds blowing over the windshield put more upward force on the drops than gravity does.
We can calculate the force this fluid (air) has of the object on the windshield (raindrop). I'm not going to bother doing the calculation right now, but it can be done. We can also calculate the down-ward force applied by the acceleration due to gravity.
The force applied to the rain drop by the wind moving past is larger than the force applied by the acceleration of gravity on the mass of the rain drop. Therefore, the raindrop moves in the direction the wind-force is being applied (there may be other forces, but the are so minor that I'm going to ignore them).
Son's follow-up: "Why do some raindrops go further up than others?"
Because some are larger than others (and therefore catch more wind and do not dry out as quickly), some find a cleaner path than others, some have more wind-force applied to them because of their position on the windshield (not blocked by the wipers, for example).
Tuesday, April 7, 2009
Why is the speed of light what it is?
Question from Son: Why isn't the speed of light different from what it is? Why isn't it faster or slower?
Hmm... Good question.
First, let's get something straight. The "speed of light" almost invariably refers to the speed of light in a vacuum. The speed of light through glass is different from that through a vacuum, and it's different through water (et cetera, et cetera, et cetera). The speed of light is dependent on the medium through which it passes. In general, a vacuum is the medium we're speaking of when we talk about "the speed of light."
Then let's first talk about the speed of light in a vacuum. That speed is approximately 300,000,000 meters per second. Here's the NIST definition (by way of the definition of the meter):
But, WHY?
Some of the brightest minds in physics have been asking this question for as long as the speed of light has been known.
Paul Dirac had a theory called "Large numbers hypothesis", which noticed that some very large numbers in physics were similar in magnitude. There's no reasoning behind his theory besides arguing that because they're both very large and have a similar scale, they must be related. In particular, he argued that the strength of gravity decreases as the age of the universe increases. There's no observational evidence for this, and most physicists consider the LNH to be numerology rather than physics.
There has been some speculation that the mass of a photon (the particle that makes up light) is not zero. A massive photon could allow variability in the speed of light; the speed of light would vary depending on its wavelength (color). Some studies have reported that the rest mass of a real photon is less than 10^-63 kg. That's pretty close to massless.
Again, this doesn't seem to answer the questions: Is the speed of light constant and why does the speed of light have the value it has.
First, a rest mass of zero does limit the speed of light to being constant, in our current paradigm. In the well-tested theory of Relativity, the speed of light is required to be constant.0
Second, a massless photon does not tell us WHY the value of c is 300,000,000 m/s, just that the speed doesn't vary.
So, WHY is it 300,000,000 m/s? Well, for one, because that's how a meter is defined. ;)
That's a lame answer, but it might help to understand that maybe we should move to a more fundamental unit. (here's a hint: Unfortunately, at some point in this discussion, we may just throw up our hands and say, "because that's the way it is and we don't know why, yet.")
According to quantum physics, there's a smallest size anything can be. This size is called the planck length and is about 1.6x10^-35 meters or about 10^20 times as small as the diameter of a proton. Quantum physics claims that there is nothing that is smaller.
There is another fundamental unit called the planck time, which is the time it takes for a photon traveling at the speed of light to travel the distance of the planck length. This is about 10^-43 seconds. There is no smaller unit of time. Now, if you pay attention to the units here (time and length), you'll notice that the speed of light (length/time) is fundamental to the definition of space-time (length and time). That is, the maximum rate at which information can travel (speed of light) through a medium is fundamentally dependent on the minimum size of the medium through which it is traveling (space-time).
So, why 299,792,458 m/s ?
Well, because our every-day units are in no way directly related to the quantum size of the universe. They need to be something we can understand in our day-to-day lives.
Hmm... Good question.
First, let's get something straight. The "speed of light" almost invariably refers to the speed of light in a vacuum. The speed of light through glass is different from that through a vacuum, and it's different through water (et cetera, et cetera, et cetera). The speed of light is dependent on the medium through which it passes. In general, a vacuum is the medium we're speaking of when we talk about "the speed of light."
Then let's first talk about the speed of light in a vacuum. That speed is approximately 300,000,000 meters per second. Here's the NIST definition (by way of the definition of the meter):
Okay. That's close enough to 300,000,000 m/s for right now.The metre is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second.
But, WHY?
Some of the brightest minds in physics have been asking this question for as long as the speed of light has been known.
Paul Dirac had a theory called "Large numbers hypothesis", which noticed that some very large numbers in physics were similar in magnitude. There's no reasoning behind his theory besides arguing that because they're both very large and have a similar scale, they must be related. In particular, he argued that the strength of gravity decreases as the age of the universe increases. There's no observational evidence for this, and most physicists consider the LNH to be numerology rather than physics.
There has been some speculation that the mass of a photon (the particle that makes up light) is not zero. A massive photon could allow variability in the speed of light; the speed of light would vary depending on its wavelength (color). Some studies have reported that the rest mass of a real photon is less than 10^-63 kg. That's pretty close to massless.
Again, this doesn't seem to answer the questions: Is the speed of light constant and why does the speed of light have the value it has.
First, a rest mass of zero does limit the speed of light to being constant, in our current paradigm. In the well-tested theory of Relativity, the speed of light is required to be constant.0
Second, a massless photon does not tell us WHY the value of c is 300,000,000 m/s, just that the speed doesn't vary.
So, WHY is it 300,000,000 m/s? Well, for one, because that's how a meter is defined. ;)
That's a lame answer, but it might help to understand that maybe we should move to a more fundamental unit. (here's a hint: Unfortunately, at some point in this discussion, we may just throw up our hands and say, "because that's the way it is and we don't know why, yet.")
According to quantum physics, there's a smallest size anything can be. This size is called the planck length and is about 1.6x10^-35 meters or about 10^20 times as small as the diameter of a proton. Quantum physics claims that there is nothing that is smaller.
There is another fundamental unit called the planck time, which is the time it takes for a photon traveling at the speed of light to travel the distance of the planck length. This is about 10^-43 seconds. There is no smaller unit of time. Now, if you pay attention to the units here (time and length), you'll notice that the speed of light (length/time) is fundamental to the definition of space-time (length and time). That is, the maximum rate at which information can travel (speed of light) through a medium is fundamentally dependent on the minimum size of the medium through which it is traveling (space-time).
So, why 299,792,458 m/s ?
Well, because our every-day units are in no way directly related to the quantum size of the universe. They need to be something we can understand in our day-to-day lives.
Friday, April 3, 2009
Why Science kicks ass: Observation, Theory, Prediction, Verification
Some 300 years ago, Kepler and Tycho Brahe made some observations of planetary motion. Kepler came up with the three laws of planetary motion:
These three laws were consistent with the Copernican idea that the Earth is not the center of the universe and earned Kepler a lot of scorn from the various Churches. 100 years or so later, Newton was able to derive Kepler's laws from his own, more fundamental laws of motion:
Together, you can derive Kepler's three laws of planetary motion (until you get too precise and then you need General Relativity). I won't bore you with any more details by doing so.
What you can also derive is the motion of any object passing by the Earth, for example.
Way back in October, a near-earth asteroid a few meters across with a trajectory very likely to bring it into contact with the Earth was detected. Very shortly after the detection, observers realized that the object would hit the earth, and the knowledge of physics allowed the observers to predict that it would impact somewhere over Sudan. The prediction was that it would break up in the atmosphere.
It did. The atmospheric impact was detected and the energy release was measured.
Pieces of that asteroid-turned-meteor-turned-meteorite have been recovered.
I posted a blurb where I did the math to estimate the density, and therefore the properties of the asteroid. Let's see if I was right... :)
Before we do that, I just want to point out how wonderfully strong science is in doing what it's meant to do: explain how things in our universe work.
The typical scientific method is something like this:
We make some observations: Planetary motion observed by Brahe and Kepler.
We make a prediction: Kepler's laws of planetary motion and Newton's laws of motion.
We test that prediction: Discover new planets by observing their gravitational influence on the known planets, and then accurately predicting the new planets' orbits and looking in the right place.
We make adjustments to the prediction based on new data: Mercury's orbit, light curves, Einstein's General Relativity.
We repeat.
Observation: There is a rock out there that has a certain trajectory.
Prediction: this rock will impact Earth's atmosphere somewhere over Sudan.
Test: We observed that rock impacted Earth's atmosphere somewhere over Sudan.
And yet again:
Observation: The energy released was about 4*10^12 joules.
Prediction: The asteroid would have a density of 1800 kg/m^3.
Prediction: The asteroid was mostly rock and emptiness between the rocks.
Test: Pick up pieces of the rocks that fell to Earth and measure density.
Well, here's the paper discussing the work of the meteorite hunters.
They reported a density of between 2100 and 2500 kg/m^3. That's higher than my prediction, but the energy released from the air blast has been updated to be about 6.7*10^12 joules, the asteroid diameter was increased to be about 4.1 m in diameter instead of the 3 meters I used, and the least dense parts of the rock burned up in the atmosphere while the most dense survived.
Here are some pictures. Much of what you see is the ablation crust, but you can also see into the interior of the rock in (d). It's not solid throughout. In fact, the measured porosity is on the order of 10% to 25%. A rubble pile. The recovered bits only account for about 0.005% of the initial mass of the impactor (the rest burned up in the atmosphere).
This is the first time the meteorites from an object first seen in space have been recovered. This is a big deal because usually we have to rely on reflected light to tell us about the rocks in space. That is fraught with problems and having a rock on the earth that came from a known object in space is going to help immensely.
It is also fortunate that we detected the asteroid and made the prediction of where it would explode in the atmosphere; the kind of material this is made of does not survive the weather on the Earth for very long and we have never found this kind of meteorite on the ground.
The authors of the recovery paper have backtraced the orbit of the object and have found a likely candidate asteroid for the source of this rock.
- The orbit of every planet is an ellipse with the sun at a focus
- A line joining the planet and the sun sweeps out equal areas during equal intervals of time
- The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit
These three laws were consistent with the Copernican idea that the Earth is not the center of the universe and earned Kepler a lot of scorn from the various Churches. 100 years or so later, Newton was able to derive Kepler's laws from his own, more fundamental laws of motion:
- There exists a set of inertial reference frames relative to which all particles with no net force acting on them will move without change to their velocity. That is, a body in motion stays in motion and a body at rest stays at rest if no external force acts on the body.
- Observed from an inertial reference frame, the net force on a particle of constant mass is proportional to the time rate of change of its linear momentum. That is, force is mass times acceleration. The net force acting on a body is the body's mass multiplied by its acceleration.
- Whenever a body, A exerts a force on another body, B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. These two forces act along the same line. That is, for every action there is an equal and opposite reaction.
- Every point mass attracts every other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses:
- F = G m1*m2/r^2
Together, you can derive Kepler's three laws of planetary motion (until you get too precise and then you need General Relativity). I won't bore you with any more details by doing so.
What you can also derive is the motion of any object passing by the Earth, for example.
Way back in October, a near-earth asteroid a few meters across with a trajectory very likely to bring it into contact with the Earth was detected. Very shortly after the detection, observers realized that the object would hit the earth, and the knowledge of physics allowed the observers to predict that it would impact somewhere over Sudan. The prediction was that it would break up in the atmosphere.
It did. The atmospheric impact was detected and the energy release was measured.
Pieces of that asteroid-turned-meteor-turned-meteorite have been recovered.
I posted a blurb where I did the math to estimate the density, and therefore the properties of the asteroid. Let's see if I was right... :)
Before we do that, I just want to point out how wonderfully strong science is in doing what it's meant to do: explain how things in our universe work.
The typical scientific method is something like this:
We make some observations: Planetary motion observed by Brahe and Kepler.
We make a prediction: Kepler's laws of planetary motion and Newton's laws of motion.
We test that prediction: Discover new planets by observing their gravitational influence on the known planets, and then accurately predicting the new planets' orbits and looking in the right place.
We make adjustments to the prediction based on new data: Mercury's orbit, light curves, Einstein's General Relativity.
We repeat.
Observation: There is a rock out there that has a certain trajectory.
Prediction: this rock will impact Earth's atmosphere somewhere over Sudan.
Test: We observed that rock impacted Earth's atmosphere somewhere over Sudan.
And yet again:
Observation: The energy released was about 4*10^12 joules.
Prediction: The asteroid would have a density of 1800 kg/m^3.
Prediction: The asteroid was mostly rock and emptiness between the rocks.
Test: Pick up pieces of the rocks that fell to Earth and measure density.
Well, here's the paper discussing the work of the meteorite hunters.
They reported a density of between 2100 and 2500 kg/m^3. That's higher than my prediction, but the energy released from the air blast has been updated to be about 6.7*10^12 joules, the asteroid diameter was increased to be about 4.1 m in diameter instead of the 3 meters I used, and the least dense parts of the rock burned up in the atmosphere while the most dense survived.
Here are some pictures. Much of what you see is the ablation crust, but you can also see into the interior of the rock in (d). It's not solid throughout. In fact, the measured porosity is on the order of 10% to 25%. A rubble pile. The recovered bits only account for about 0.005% of the initial mass of the impactor (the rest burned up in the atmosphere).
This is the first time the meteorites from an object first seen in space have been recovered. This is a big deal because usually we have to rely on reflected light to tell us about the rocks in space. That is fraught with problems and having a rock on the earth that came from a known object in space is going to help immensely.
It is also fortunate that we detected the asteroid and made the prediction of where it would explode in the atmosphere; the kind of material this is made of does not survive the weather on the Earth for very long and we have never found this kind of meteorite on the ground.
The authors of the recovery paper have backtraced the orbit of the object and have found a likely candidate asteroid for the source of this rock.
Thursday, April 2, 2009
Google is geeky cool.
Have you ever wondered what, exactly, "once in a blue moon" really means?
Try this:
Go to google's search page and enter:
Once in a blue moon
as your search term.
The result:
1/(once in a blue moon). You get 2.71542689 years. That is a blue moon (two full moons in one month) happens once every 2.71... years.
Or, try this:
(number of horns on a unicorn + the answer to life the universe and everything) / once in a blue moon
Or:
e^(i*Pi) + 1
(0), which is correct and happens to be one of the coolest identities in all of mathematics.
e^(i*Pi) + 1 = 0
This is called Euler's equation. It uses five of the most important constants in mathematics and the mathematical sciences (e, Pi, i, 1, and 0). It also uses three of the most important operations (addition, multiplication, power) and THE most important relation (=). I've already mentioned this, but it's such a cool equation that you need to see it again and again. :)
Try this:
Go to google's search page and enter:
Once in a blue moon
as your search term.
The result:
1.16699016 × 10-8 hertz
That is, once every 10 to the negative 8 seconds. Or, to better under stand the result, enter this:1/(once in a blue moon). You get 2.71542689 years. That is a blue moon (two full moons in one month) happens once every 2.71... years.
Or, try this:
(number of horns on a unicorn + the answer to life the universe and everything) / once in a blue moon
Or:
e^(i*Pi) + 1
(0), which is correct and happens to be one of the coolest identities in all of mathematics.
e^(i*Pi) + 1 = 0
This is called Euler's equation. It uses five of the most important constants in mathematics and the mathematical sciences (e, Pi, i, 1, and 0). It also uses three of the most important operations (addition, multiplication, power) and THE most important relation (=). I've already mentioned this, but it's such a cool equation that you need to see it again and again. :)
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