Oh I agree that the chances of Deep Impact causing a future collision of the comet with earth are minuscule, it's just that the penalty for being wrong is so immense that gives me pause. When a 747 falls out of the sky it only impacts a small area and can decimate a small village or town, but if Tempel 1 were to impact earth (and if it contains a rocky core rather than being all ice - no one yet knows its mass or composition) it would probably decimate an area the size of a small state and create serious problems worldwide for many years to come.
I did a quick "back of the envelope" worst-case calculation based on conservation of momentum with the assumption that the density of Tempel 1 is the same as earth's (probably an erroneous assumption, but I have to assume something for its density) and that it's radius is 3 Km. Furthermore I assumed that Temple1 was stationary instead of worrying about vectors and orbital trajectories, and that the entire force of the impact is transferred to Tempel 1 (rather than being a glancing blow, or for the "bullet" to completely pierce the comet and exit from the other side). I also used 23,000 mph (37,015 km/hour) as the impact velocity, although I seem to recall reading somewhere that the actual relative impact velocity is more like 10,000 mph.
Under these very simple conditions I found that the Deep Impact "bullet" would impart an incredibly speedy velocity of 0.5304 millimeter/day to Tempel 1!;-) At that rate, it would require roughly 438 billion years to change Tempel's orbit by 0.568 AU (the closest the comet has ever approached the earth in the past), so I guess I don't have to worry about it happening in my lifetime!;-) In fact, IIRC, in a couple of billion years Sol is supposed to become a red giant and engulf the entire solar system.
What is more worrisome to me is what happens in it's next few encounters with Jupiter. According to the JPL Deep Impact web page, Tempel 1 is in a relatively stable but complex orbit which is in "1:2 resonance with Jupiter" (which I assume means that it rendezvous with Jupiter every two Jovian years). I'm sure you're familiar with the concept of "gravity assist." In two years the copper "bullet" would have displaced Tempel's orbit by roughly 39 cm (15 inches), and 78 cm the next visit, etc. Gravity assist can greatly accelerate or decelerate a spacecraft (or comet) depending upon the geometry of the encounter while also changing it's trajectory. If Tempel makes very close passes to Jupiter, might it be possible that this small difference in approach trajectory to Jupiter might be amplified by Jupiter's gravity and orbital motion to the point that Temple's trajectory is radically altered? I don't know the answer to that since I'm not an astrophysicist, but I certainly hope that the project scientists do know the answer, because they are gambling not only their own lives on the outcome, but all of humanities lives as well.
I am all for space exploration, and have in fact written software for several space missions (including Cassini), so I know very well that things can and do go wrong - routinely. Because of that I would prefer a less intrusive method of determining Tempel's internal composition.
Hardly. Tempel 1 has an approximate radius of only 3 kilometers. Earth has a radius of 6,378 kilometers. Even NASA says that "the impact will cause a slight change in the comet's orbit..."
The problem is that most of the comets in our solar system have pretty much settled down into an equilibrium in the sense that any of them that were going to hit earth have already done so long ago (barring perturbations from outside our solar system). Introducing a new variable, even if very small, into that equilibrium would have an unknown future effect - like the proverbial butterfly wings precipitating a hurricane elsewhere.
Re:Cue Warner Bros cartoon...
on
NASA's Deep Impact
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· Score: 2, Interesting
... or where the bullet nudges the comet just enough to perturb its orbit in such a way that it hits earth 15 years from now. I for one would very much like to know more about why this won't happen. It seems to me that the comet's unknown composition would render any predictions of the effect on its orbit meaningless.
They are both partly digital and partly analog, with the ratio depending upon the type of neuron in question (eg; glial neurons are mostly analog I believe).
Yes, BUT in the USA (for example) *I* get to chose which stations I wish to support by watching their commercials, I am not forced to support any government funded stations directly.
They have to do something to earn their bribe money.
United States Constitution, Article II, Section 4 The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors
Why don't the people of your community get together and fund a school for their children themselves (ie; rent a facility, hire the teachers, etc). That way they could hire the type of teachers they want teaching their children and be free of federal regulation. It would surely be cheaper than everyone sending their kids to a private school. Education used to be solely a local function, and there is no reason it can't be again.
"I really don't see the government, at least not with current policy/spending/etc., creating any sort of incentive here."
The State of California will reimburse homeowners who install wind or photovoltaic power approximately 45% of the cost of the system.
In my case, the City of Glendale, California, paid 50% ($21,000) of the total $42,000 cost of having a 4 KW photovoltaic array installed on my roof. What I heard is that they were required to do so by the California Public Utilities Commission. My photovoltaic system is a so-called "net-metered" system that feeds power back into the grid whenever the sun is shining and the system is producing more power than I'm consuming. It provides for almost half of my power usage. During most days my electric meter actually does run backwards.
Since then, I've had "blow-in" insulation installed in the exterior walls of my home (it's an old house and didn't have any insulation in the walls at all!). The odd thing is that although the insulation only cost $1,200 to install, it cut my power bills (most of which are for electric air conditioning during the summer) almost in half - about the same as the photovoltaic system did! I estimate that my electric bills for next year will only be about 25% of what I used to pay.
The 2003 violent crime rate - assault, sexual assault and armed robbery - stood at 22.6 victims for every 1,000 people age 12 and older. That amounts to about one violent crime victim for every 44 U.S. residents.
Given the high rate of voter apathy in the USA, do you think a majority of voters will ever wake up and realize that government is our master rather than our servant? If so, would you care to predict approximately when you think that might happen and what type of event (if any), will portend it?
"...how many of them would be foiled by the owner having a safely stored gun in the house?"
Absolutely correct. That's why I keep my guns loaded and ready to go, and make sure that at least one of them is within easy reach at all times (and no, I don't have any young children at home).
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I did a quick "back of the envelope" worst-case calculation based on conservation of momentum with the assumption that the density of Tempel 1 is the same as earth's (probably an erroneous assumption, but I have to assume something for its density) and that it's radius is 3 Km. Furthermore I assumed that Temple1 was stationary instead of worrying about vectors and orbital trajectories, and that the entire force of the impact is transferred to Tempel 1 (rather than being a glancing blow, or for the "bullet" to completely pierce the comet and exit from the other side). I also used 23,000 mph (37,015 km/hour) as the impact velocity, although I seem to recall reading somewhere that the actual relative impact velocity is more like 10,000 mph.
Under these very simple conditions I found that the Deep Impact "bullet" would impart an incredibly speedy velocity of 0.5304 millimeter/day to Tempel 1! ;-) At that rate, it would require roughly 438 billion years to change Tempel's orbit by 0.568 AU (the closest the comet has ever approached the earth in the past), so I guess I don't have to worry about it happening in my lifetime! ;-) In fact, IIRC, in a couple of billion years Sol is supposed to become a red giant and engulf the entire solar system.
What is more worrisome to me is what happens in it's next few encounters with Jupiter. According to the JPL Deep Impact web page, Tempel 1 is in a relatively stable but complex orbit which is in "1:2 resonance with Jupiter" (which I assume means that it rendezvous with Jupiter every two Jovian years). I'm sure you're familiar with the concept of "gravity assist." In two years the copper "bullet" would have displaced Tempel's orbit by roughly 39 cm (15 inches), and 78 cm the next visit, etc. Gravity assist can greatly accelerate or decelerate a spacecraft (or comet) depending upon the geometry of the encounter while also changing it's trajectory. If Tempel makes very close passes to Jupiter, might it be possible that this small difference in approach trajectory to Jupiter might be amplified by Jupiter's gravity and orbital motion to the point that Temple's trajectory is radically altered? I don't know the answer to that since I'm not an astrophysicist, but I certainly hope that the project scientists do know the answer, because they are gambling not only their own lives on the outcome, but all of humanities lives as well.
I am all for space exploration, and have in fact written software for several space missions (including Cassini), so I know very well that things can and do go wrong - routinely. Because of that I would prefer a less intrusive method of determining Tempel's internal composition.
That's why I use Password Safe .
The problem is that most of the comets in our solar system have pretty much settled down into an equilibrium in the sense that any of them that were going to hit earth have already done so long ago (barring perturbations from outside our solar system). Introducing a new variable, even if very small, into that equilibrium would have an unknown future effect - like the proverbial butterfly wings precipitating a hurricane elsewhere.
... or where the bullet nudges the comet just enough to perturb its orbit in such a way that it hits earth 15 years from now. I for one would very much like to know more about why this won't happen. It seems to me that the comet's unknown composition would render any predictions of the effect on its orbit meaningless.
Nicely put.
What makes you think you or I have a soul? Where is it located and how much does it weight, etc?
What business is it of yours if someone else wants to take drugs? Maybe they don't want to be cured?
They are both partly digital and partly analog, with the ratio depending upon the type of neuron in question (eg; glial neurons are mostly analog I believe).
His estimate was probably based on the common, and incorrect, belief that neurons are purely digital.
We did that in 1977
http://snipurl.com/a2d0
Brand: Compaq
Chip Type: Intel Pentium II
Memory (RAM): 128 MB
Hard Drive Capacity: 10 GB
Primary Drive: CD-ROM
Processor Speed: 400 MHz
Bundled Items: Keyboard, Modem, Monitor, Mouse, Network Card
Yes, BUT in the USA (for example) *I* get to chose which stations I wish to support by watching their commercials, I am not forced to support any government funded stations directly.
Correction: You are being forced to pay for a service you may or may not want.
They have to do something to earn their bribe money.
Why don't the people of your community get together and fund a school for their children themselves (ie; rent a facility, hire the teachers, etc). That way they could hire the type of teachers they want teaching their children and be free of federal regulation. It would surely be cheaper than everyone sending their kids to a private school. Education used to be solely a local function, and there is no reason it can't be again.
Ames Research Center is one of the major internet hubs, so I doubt that they have to worry about bandwidth bills. ;-)
BugMeNot username and password:
Username: registrationsucks1 Password: asdoestheage
The State of California will reimburse homeowners who install wind or photovoltaic power approximately 45% of the cost of the system.
In my case, the City of Glendale, California, paid 50% ($21,000) of the total $42,000 cost of having a 4 KW photovoltaic array installed on my roof. What I heard is that they were required to do so by the California Public Utilities Commission. My photovoltaic system is a so-called "net-metered" system that feeds power back into the grid whenever the sun is shining and the system is producing more power than I'm consuming. It provides for almost half of my power usage. During most days my electric meter actually does run backwards.
Since then, I've had "blow-in" insulation installed in the exterior walls of my home (it's an old house and didn't have any insulation in the walls at all!). The odd thing is that although the insulation only cost $1,200 to install, it cut my power bills (most of which are for electric air conditioning during the summer) almost in half - about the same as the photovoltaic system did! I estimate that my electric bills for next year will only be about 25% of what I used to pay.
Given the high rate of voter apathy in the USA, do you think a majority of voters will ever wake up and realize that government is our master rather than our servant? If so, would you care to predict approximately when you think that might happen and what type of event (if any), will portend it?
Absolutely correct. That's why I keep my guns loaded and ready to go, and make sure that at least one of them is within easy reach at all times (and no, I don't have any young children at home).