Actually, comets are considered building blocks of the solar system. That's why there's a large push from NASA and the ESA to send spacecraft to comets and land on them and/or gather samples from them. Here are a few links:
I grew up in West Chester, PA, where C64 was based (or at least one of their factories was). I still remember when the factory shut down, our entire school district got thousands of C64's dirt cheap...we had them in all the classrooms, all the libraries. We didn't have a Windows computer lab and an Apple computer lab, but rather a Commodore lab and an Apple lab. I didnt even know what Windows was until 6th grade.
I'm aware of the limits of Newtonian and Einsteinian physics. Back in the day, however, it was believed (or so I hear - someone else wants documentation, which I'm currently looking for) that you could not accelerate an object past the speed of sound in the medium that the object is in. That doesn't mean >Mach 1 speeds were believed to be impossible, because they were aware of speeds of meteorites as they entered our atmoshere. The belief was supposedly that you couldn't accelerate a body past the speed of sound on earth in our atmosphere. For airflight, that meant mach 1 at the time.
They required no novel physics to accomplish their feat, only the application of known physical laws.
However, travel to other stars in less than a human life-time in our frame of reference will require super-luminal speeds. There is no physics known yet that will allow us to achieve this.
True, but it should be pointed out that for decades after that, most scientists thought it was physically impossible to break the speed of sound in an aircraft. There was no physics that allowed > Mach 1 speeds to be achieved. With time, that theory was also proven wrong.
Even at body temperature, the molecules are in their lowest vibrational states. Using the U(x) and T(p) terminology, you're right that U(x) will not be affected by changes in mass. However, T(p), specifically, the vibrational energy levels will be affected by the change in mass. Specifically, they will all drop, but the transition state (or saddle point) energies will drop less than those of the stable state, making the effective barrier along the reaction coordinate larger upon substitution. This larger barrier thereby lowers the reaction rate.
The T(p) is the crucial part of this, and is dependent upon the energy levels occupied. At body temperature, the energy levels occupied are the lowest vibrational levels (and millions of rotational levels of course). Since the Boltzmann distribution depends upon the overall energy of the molecule E, not just U(x), a change in mass affects T(p) which then affects E.
Does that make sense?
This info is coming from a book called "The Tunnel Effect In Chemistry" (I forget the author's name), and it is discussed in chapter 4.
Incidentally, the tunnel effect (which is undoubtedly affected by mass) also plays a role in reaction rates. This is discussed in the second half of the chapter.
This is a great discussion by the way (this is the reason why I ever post on/.)
You are correct, except you need to take into account the idea of a zero point energy.
Specifically, what is U(x)?
In chemical kinetics U(x), or more properly (delta)U(x) is the energy difference between the stable state and the transition state. When a lighter isotope is substituted with a heavier isotope, the zero point vibrational energy levels all lower in energy. The same thing occurs for the transition state, except that the energy drops less in the transition state. This results in a higher effective reaction barrier, thereby slowing the reaction down.
Just following up, the kinetic isotope effect is a consequence of differences in activation energies that are due to differences zero-point energies of stable and transition states. These differences in zero-point energies are a result of the effects of isotopic substitution.
Not necessarily true (I know, hence your albeit)...free neutrons have a halflife of about 15 minutes. The only thing that keeps them stable is interactions within the nucleus.
That puts some parts of north america at the equator, which is impossible, as no parts of NA are one the equator. If you use a program like Celestia, you can actually mimic what the MGS saw (except that it's a clearer image of course), and their assignment is correct. The center of the image is northern south america. Way up high, almost going onto the oher side of the Earth is NA itself
Generally, if you have a pulsed laser (i.e. a Nd:YAG or Ti:Sapph) you measure in energy per pulse, say in mJ/pulse. However, if you have a continuous wave laser, like an Ar+, you measure it in power, like mJ/sec = mW.
For publicity reasons, lot of labs put their pulsed lasers in terms of power. For example, in the lab that I work in, we have a Nd:YAG laser that outputs about 2 mJ/pulse green light. However, all of that happens in about 9 nanoseconds. So if we wanted to impress a visitor, we would say that the power of the laser is 2mJ/9ns ~ 200 kW. Hundreds of kilowatts sound a lot more impressive than millijoules
"The ASI calculates the chance that a person will be hit by falling debris to be one in 2000."
That's right from the story. It means that there is a 1-in-2000 chance that a person will be hit by falling debris. If they meant one out of every 2000 people would be hit, it would say "The chances of being hit are one in 2000" or "there is a one in 2000 chance of being hit" or something like that.
There should be emphasis on "a person". That is, there is a one in 2000 chance of one person being hit.
It is right. It's not saying that one out of every 2000 people will be hit. It means that in this incident, the probability of a person being hit is 1 on 2000. In other words, if 2000 satellites came out of orbit, only one person would be hit by debris. The population density is already taken into account.
It is right. It's not saying that one out of every 2000 people will be hit. It means that in this incident, the probability of a person being hit is 1 on 2000. In other words, if 2000 satellites came out of orbit, only one person would be hit by debris. The population density is already taken into account.
I work in the Pitt chem department (for Dr. David Pratt) on the 6th floor. Sandy Asher's group is on the 7th floor, so we see him all the time. He is one of the most active researchers in the department. Every time we look, he's working on some new, really interesting project. It's nice to see that one of them has made it to the pages of Slashdot:-)
My point is that while you're right that there were less disasters because they were simpler, the shuttle has different goals. It's goals require it to be more complex. Being complex means that more things can go wrong. There's no amount of good design that can go into the shuttle to make it as safe as the capsules were. There's just more stuff to go wrong, and if they need to meet the requirements of the missions, they need to make it more complex than the capsule missions.
As far as given the damage that Apollo had, which would survive, the capsule or the shuttle, neither would have survived. The crew was lucky that the explosion occured on the service module, not on their reentry vehicle, the capsule. If it had happened on their reentry vehicle, then we can compare apples to apples. It would have crashed just like the shuttle. The service module would not have made it through reentry, either.
As far as the actual shuttle program, I don't think most of the American public has noticed the shuttle program turn into a PR campaign/U-Haul. I think that shuttle missions are so common now that there's no more awe associated with sending a human into orbit. This is precisely why a lot of the shuttle missions have turned into PR campaigns, not the other way around. After the Apollo successes, NASA didn't expect the drop in public support. This was a bad prediction on their part. Since then the shuttle missions have spiraled into an overly-expensive program. NASA realizes this, and that's why they're working on newer, more reusable, easy-to-launch, and cheaper vehicles.
I really don't think it's a hallmark of poor design.
The orbiting capsules were intended to go into orbit for a matter of hours and then come back to earth. They were not reusable and were far too small to contain many science experiments. The shuttle is intended to go into space for extended periods of time. This requires more equipment, more moving parts. It is also intended to be a scientific laboratory. This, too, requires WAY more equipment, and a lot more moving parts. It's also intended to be reusable.
This isn't a poor design/good design issue. It's goal oriented issue. The capsules were considerably simpler, because the goals of the missions were considerably simpler. The shuttle is more complex (read: has more moving parts) because the goals of the shuttle missions are more complex.
You may have an argument for the Apollo missions: more complex missions. But Apollo 13 was almost a disaster, and many people in the field consider it a miracle that one of the Apollo missions didn't go wrong.
The shuttle missions can rarely be compared to the early-NASA missions. It was a different world, there were different goals, a different government, and different public support. Yes the missions happen less often than they were originally intended, but then again, there's far less public support of space missions, and Congress cuts NASA's budget practically every year. What do you expect?
I think part of the point is to illustrate how much fine tuning and crafting is behind the design and production of a car. Only the parts of an Accord are used. That's not a coincidence. And they are set up extremely precisely. If just one part was out of place, it wouldn't have worked. The fact that the sequence works so elegantly implies that the same sort of precision work went into the Accord itself, and that it, too, works elegantly.
What is the final ending? All of these bits and pieces work together seamlessly (because they were put together perfectly) to make an Accord run.
So the idea is that there is a lot of precision and hard work that goes into the making of the car, down to the little parts, like bearings.
I presume that the commercial is supposed to make you not only say, "hey that's cool," but also think about how much hard work went into the making of something like an Accord.
It's interesting that you bring up time scales on a different planet - take a look at Mars Pathfinder data sets. All the data is dated in terms of "sols" = 1 Martian Day. No matter what planet you're on, it makes sense to make that planet's day an integral part of the time system, as it's easy to deal with.
Making the time system fit the planet is very nice, as it is kind of just makes sense. The problem with it is that, for example, try switching from the Venusian day to the terrestrial day - it's not so easy...you have some pretty ugly conversions to do.
On the other hand, the decimal time system has the opposite problem. It's universially applicable, but it doesn't match up with any sort of solar or astronomical phenomena.
I like the idea of using a local system for local time and a decimal system for intrasystem use. Current astronomy sort of has that going right now, where instead of having to worry about local time zones, the reference everything to Universal Time (UT). It makes things much easier.
First, I'm curious (maybe someone out there has a link?) about how solar wind affects affects day lengths. It's known and been imaged that bursts of solar wind cause the earth's atmosphere to swell, and I'm curious what this redustribution of mass does to the moment of inertia and rotational speed of the planet.
Second, I find it kind of interesting the change in the way we percieve time. Centuries ago, the earth made a great clock. 24 hours was defined as a day, and if all of the sudden the day became longer, that longer period of time was defined as 24 hours. Now, we see that the earth makes a pretty bad clock (by today's standards), and rather than relying on the earth as our ultimate timepiece, we rely on atomic clocks. It seems strange: we have all of these time units like hours, days, months, years, etc., all defined first by astronomical methods, but now because of our (technological) ability to be more regular than the cosmos, the hour, day, month, year, etc. have sort of lost their origins.
hotornot could really speed up its processing of hotness with this thing! who needs people to look at hot girls/guys and rate their hotness when a computer and some webcams can do it in a few milliseconds?
I was responding to his physics of what would happen if negative mass existed, not to the possibility of negative mass. I'm a physicist, I know that antimatter has positive mass. You may also notice that he referred to negative mass, not antimatter. He, too, was just going through the mathematics of it.
And you may also notice that I agreed with you about your second point about going above c, in which case, thanks for saying it again. I disagreed via thought experiment, you disagreed via established theory. Both approaches are wonderful
I agree up to the point where you can get both up to indefinite speed. So what will happen, once they are at, say, a speed of warp 10, and I toss another positive mass at my negative mass? Poof, they annihilate, and now I have a positive mass that's moving at a smooth warp 10. Or what happens if instead I make the two original masses collide once they're at warp 10?. They annihilate, creating a photon or two, travelling at 10c, which, of course, is impossible. Or what if I'm riding on my positive mass as this acceleration is occuring, then destroy my negative mass. I will be moving at warp 10, and percieve the entire universe as moving at about that speed with respect to me.
I do think there are a few too many conservation laws being broken there.
Slashdot Mirror
Actually, comets are considered building blocks of the solar system. That's why there's a large push from NASA and the ESA to send spacecraft to comets and land on them and/or gather samples from them. Here are a few links:
Stardust
Contour (failed)
Rosetta (to be launched)
I grew up in West Chester, PA, where C64 was based (or at least one of their factories was). I still remember when the factory shut down, our entire school district got thousands of C64's dirt cheap...we had them in all the classrooms, all the libraries. We didn't have a Windows computer lab and an Apple computer lab, but rather a Commodore lab and an Apple lab. I didnt even know what Windows was until 6th grade.
My favorite game was Jumpman Junior...
---
I'm aware of the limits of Newtonian and Einsteinian physics. Back in the day, however, it was believed (or so I hear - someone else wants documentation, which I'm currently looking for) that you could not accelerate an object past the speed of sound in the medium that the object is in. That doesn't mean >Mach 1 speeds were believed to be impossible, because they were aware of speeds of meteorites as they entered our atmoshere. The belief was supposedly that you couldn't accelerate a body past the speed of sound on earth in our atmosphere. For airflight, that meant mach 1 at the time.
They required no novel physics to accomplish their feat, only the application of known physical laws.
However, travel to other stars in less than a human life-time in our frame of reference will require super-luminal speeds. There is no physics known yet that will allow us to achieve this.
True, but it should be pointed out that for decades after that, most scientists thought it was physically impossible to break the speed of sound in an aircraft. There was no physics that allowed > Mach 1 speeds to be achieved. With time, that theory was also proven wrong.
Just out of curiosity, do any Navy/AF fans out there know what sort of maintenance would be required for this thing?
i.e. what would need to be done to keep it afloat and operational, and how much would that cost (ballpark)?
Even at body temperature, the molecules are in their lowest vibrational states. Using the U(x) and T(p) terminology, you're right that U(x) will not be affected by changes in mass. However, T(p), specifically, the vibrational energy levels will be affected by the change in mass. Specifically, they will all drop, but the transition state (or saddle point) energies will drop less than those of the stable state, making the effective barrier along the reaction coordinate larger upon substitution. This larger barrier thereby lowers the reaction rate.
/.)
The T(p) is the crucial part of this, and is dependent upon the energy levels occupied. At body temperature, the energy levels occupied are the lowest vibrational levels (and millions of rotational levels of course). Since the Boltzmann distribution depends upon the overall energy of the molecule E, not just U(x), a change in mass affects T(p) which then affects E.
Does that make sense?
This info is coming from a book called "The Tunnel Effect In Chemistry" (I forget the author's name), and it is discussed in chapter 4.
Incidentally, the tunnel effect (which is undoubtedly affected by mass) also plays a role in reaction rates. This is discussed in the second half of the chapter.
This is a great discussion by the way (this is the reason why I ever post on
You are correct, except you need to take into account the idea of a zero point energy.
Specifically, what is U(x)?
In chemical kinetics U(x), or more properly (delta)U(x) is the energy difference between the stable state and the transition state. When a lighter isotope is substituted with a heavier isotope, the zero point vibrational energy levels all lower in energy. The same thing occurs for the transition state, except that the energy drops less in the transition state. This results in a higher effective reaction barrier, thereby slowing the reaction down.
Does that answer the question?
Just following up, the kinetic isotope effect is a consequence of differences in activation energies that are due to differences zero-point energies of stable and transition states. These differences in zero-point energies are a result of the effects of isotopic substitution.
Not necessarily true (I know, hence your albeit)...free neutrons have a halflife of about 15 minutes. The only thing that keeps them stable is interactions within the nucleus.
Right. Um, I think we're agreeing here, are we not?
That puts some parts of north america at the equator, which is impossible, as no parts of NA are one the equator. If you use a program like Celestia, you can actually mimic what the MGS saw (except that it's a clearer image of course), and their assignment is correct. The center of the image is northern south america. Way up high, almost going onto the oher side of the Earth is NA itself
Generally, if you have a pulsed laser (i.e. a Nd:YAG or Ti:Sapph) you measure in energy per pulse, say in mJ/pulse. However, if you have a continuous wave laser, like an Ar+, you measure it in power, like mJ/sec = mW.
For publicity reasons, lot of labs put their pulsed lasers in terms of power. For example, in the lab that I work in, we have a Nd:YAG laser that outputs about 2 mJ/pulse green light. However, all of that happens in about 9 nanoseconds. So if we wanted to impress a visitor, we would say that the power of the laser is 2mJ/9ns ~ 200 kW. Hundreds of kilowatts sound a lot more impressive than millijoules
First line of the AP article:
"Hundreds of worms from a science experiment aboard the space shuttle Columbia have been found alive in the wreckage, NASA said Wednesday."
"The ASI calculates the chance that a person will be hit by falling debris to be one in 2000."
That's right from the story. It means that there is a 1-in-2000 chance that a person will be hit by falling debris. If they meant one out of every 2000 people would be hit, it would say "The chances of being hit are one in 2000" or "there is a one in 2000 chance of being hit" or something like that.
There should be emphasis on "a person". That is, there is a one in 2000 chance of one person being hit.
It is right. It's not saying that one out of every 2000 people will be hit. It means that in this incident, the probability of a person being hit is 1 on 2000. In other words, if 2000 satellites came out of orbit, only one person would be hit by debris. The population density is already taken into account.
It is right. It's not saying that one out of every 2000 people will be hit. It means that in this incident, the probability of a person being hit is 1 on 2000. In other words, if 2000 satellites came out of orbit, only one person would be hit by debris. The population density is already taken into account.
I work in the Pitt chem department (for Dr. David Pratt) on the 6th floor. Sandy Asher's group is on the 7th floor, so we see him all the time. He is one of the most active researchers in the department. Every time we look, he's working on some new, really interesting project. It's nice to see that one of them has made it to the pages of Slashdot :-)
My point is that while you're right that there were less disasters because they were simpler, the shuttle has different goals. It's goals require it to be more complex. Being complex means that more things can go wrong. There's no amount of good design that can go into the shuttle to make it as safe as the capsules were. There's just more stuff to go wrong, and if they need to meet the requirements of the missions, they need to make it more complex than the capsule missions.
As far as given the damage that Apollo had, which would survive, the capsule or the shuttle, neither would have survived. The crew was lucky that the explosion occured on the service module, not on their reentry vehicle, the capsule. If it had happened on their reentry vehicle, then we can compare apples to apples. It would have crashed just like the shuttle. The service module would not have made it through reentry, either.
As far as the actual shuttle program, I don't think most of the American public has noticed the shuttle program turn into a PR campaign/U-Haul. I think that shuttle missions are so common now that there's no more awe associated with sending a human into orbit. This is precisely why a lot of the shuttle missions have turned into PR campaigns, not the other way around. After the Apollo successes, NASA didn't expect the drop in public support. This was a bad prediction on their part. Since then the shuttle missions have spiraled into an overly-expensive program. NASA realizes this, and that's why they're working on newer, more reusable, easy-to-launch, and cheaper vehicles.
I really don't think it's a hallmark of poor design.
The orbiting capsules were intended to go into orbit for a matter of hours and then come back to earth. They were not reusable and were far too small to contain many science experiments. The shuttle is intended to go into space for extended periods of time. This requires more equipment, more moving parts. It is also intended to be a scientific laboratory. This, too, requires WAY more equipment, and a lot more moving parts. It's also intended to be reusable.
This isn't a poor design/good design issue. It's goal oriented issue. The capsules were considerably simpler, because the goals of the missions were considerably simpler. The shuttle is more complex (read: has more moving parts) because the goals of the shuttle missions are more complex.
You may have an argument for the Apollo missions: more complex missions. But Apollo 13 was almost a disaster, and many people in the field consider it a miracle that one of the Apollo missions didn't go wrong.
The shuttle missions can rarely be compared to the early-NASA missions. It was a different world, there were different goals, a different government, and different public support. Yes the missions happen less often than they were originally intended, but then again, there's far less public support of space missions, and Congress cuts NASA's budget practically every year. What do you expect?
I think part of the point is to illustrate how much fine tuning and crafting is behind the design and production of a car. Only the parts of an Accord are used. That's not a coincidence. And they are set up extremely precisely. If just one part was out of place, it wouldn't have worked. The fact that the sequence works so elegantly implies that the same sort of precision work went into the Accord itself, and that it, too, works elegantly.
What is the final ending? All of these bits and pieces work together seamlessly (because they were put together perfectly) to make an Accord run.
So the idea is that there is a lot of precision and hard work that goes into the making of the car, down to the little parts, like bearings.
I presume that the commercial is supposed to make you not only say, "hey that's cool," but also think about how much hard work went into the making of something like an Accord.
It's interesting that you bring up time scales on a different planet - take a look at Mars Pathfinder data sets. All the data is dated in terms of "sols" = 1 Martian Day. No matter what planet you're on, it makes sense to make that planet's day an integral part of the time system, as it's easy to deal with.
Making the time system fit the planet is very nice, as it is kind of just makes sense. The problem with it is that, for example, try switching from the Venusian day to the terrestrial day - it's not so easy...you have some pretty ugly conversions to do.
On the other hand, the decimal time system has the opposite problem. It's universially applicable, but it doesn't match up with any sort of solar or astronomical phenomena.
I like the idea of using a local system for local time and a decimal system for intrasystem use. Current astronomy sort of has that going right now, where instead of having to worry about local time zones, the reference everything to Universal Time (UT). It makes things much easier.
First, I'm curious (maybe someone out there has a link?) about how solar wind affects affects day lengths. It's known and been imaged that bursts of solar wind cause the earth's atmosphere to swell, and I'm curious what this redustribution of mass does to the moment of inertia and rotational speed of the planet.
Second, I find it kind of interesting the change in the way we percieve time. Centuries ago, the earth made a great clock. 24 hours was defined as a day, and if all of the sudden the day became longer, that longer period of time was defined as 24 hours. Now, we see that the earth makes a pretty bad clock (by today's standards), and rather than relying on the earth as our ultimate timepiece, we rely on atomic clocks. It seems strange: we have all of these time units like hours, days, months, years, etc., all defined first by astronomical methods, but now because of our (technological) ability to be more regular than the cosmos, the hour, day, month, year, etc. have sort of lost their origins.
It seems the robot works more like 'hotornot'
thereby making it the world's first hotornotbot!
hotornot could really speed up its processing of hotness with this thing! who needs people to look at hot girls/guys and rate their hotness when a computer and some webcams can do it in a few milliseconds?
kidding, of course
I was responding to his physics of what would happen if negative mass existed, not to the possibility of negative mass. I'm a physicist, I know that antimatter has positive mass. You may also notice that he referred to negative mass, not antimatter. He, too, was just going through the mathematics of it.
And you may also notice that I agreed with you about your second point about going above c, in which case, thanks for saying it again. I disagreed via thought experiment, you disagreed via established theory. Both approaches are wonderful
I agree up to the point where you can get both up to indefinite speed. So what will happen, once they are at, say, a speed of warp 10, and I toss another positive mass at my negative mass? Poof, they annihilate, and now I have a positive mass that's moving at a smooth warp 10. Or what happens if instead I make the two original masses collide once they're at warp 10?. They annihilate, creating a photon or two, travelling at 10c, which, of course, is impossible. Or what if I'm riding on my positive mass as this acceleration is occuring, then destroy my negative mass. I will be moving at warp 10, and percieve the entire universe as moving at about that speed with respect to me.
I do think there are a few too many conservation laws being broken there.