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Mysterious Force Affects Pioneer 10 & 11 Probes
JabbaTheFart writes "The Guardian is writing that something strange is tugging at America's oldest spacecraft. As the Pioneer 10 and 11 probes head towards distant stars, scientists have discovered that the craft - launched more than 30 years ago - appear to be in the grip of a mysterious force that is holding them back as they sweep out of the solar system.
Some researchers say unseen 'dark matter' may permeate the universe and that this is affecting the Pioneers' passage. Others say flaws in our understanding of the laws of gravity best explain the crafts' wayward behaviour."
exactly what was AFFECTED?
It is also thought that dark matter is at the centre of galaxies Could explain a lot of things, e.g. the expansion/contraction of the universe. Judging by the amount of "tangible" matter in the universe, there is no way to halt the expansion, and it will go on forever. However, if there is dark matter, it could hold enough gravity to halt expansion and force the big crunch. Lots of info on this sort of stuff here
Note to Hemos: The verb is spelled "affect". You know, with an "a". The noun is spelled "effect", but it's the verb needed in the title.
Sorry, don't mean to sound curmudgeonly and grumpy and so forth, but so few people get this right that I can't stand by and let it slide.
I'll put the cantankerous old grouch away now...
Daar is nie 'n lepel nie
Bit of an old story this.
wot no sig
Link to the Physics Web article: http://physicsweb.org/article/world/17/9/3
RELEASE: 03-082HQ PIONEER 10 SPACECRAFT SENDS LAST SIGNAL After more than 30 years, it appears the venerable Pioneer 10 spacecraft has sent its last signal to Earth. Pioneer's last, very weak signal was received on Jan. 22, 2003. NASA engineers report Pioneer 10's radioisotope power source has decayed, and it may not have enough power to send additional transmissions to Earth. NASA's Deep Space Network (DSN) did not detect a signal during the last contact attempt Feb. 7, 2003. The previous three contacts, including the Jan. 22 signal, were very faint with no telemetry received. The last time a Pioneer 10 contact returned telemetry data was April 27, 2002. NASA has no additional contact attempts planned for Pioneer 10.
Bush Lies On the Record.
It is most certainly not radiation pressure from the RTGs. If you would care to read the original 54 page article gr-qc/0104064 at http://arxiv.org/ you would have noticed that the original authors took serious effort to account for the radiation pressure from the RTGs and could make it in no way large enough to account for the anomaly.
Certainly in his anthology "The River of Time" there was a story called " The Crystal Spheres"
I like the following explanation of the anomalous acceleration. No dark matter/20 dimensions/new gravity theory needed here. A small amount of dust in the kuiper-belt that transfers momentum with the probe should be enough to explain the slowdown. Look at: http://www.newtonphysics.on.ca/Anomalous/Accelerat ion.html
Also, quite a few stories require that the spacecraft be a certain distance from the gravity well of the solar system before they can use their FTL engines.
This doesn't quite quench my thirst for information: does this mean the probes are still sending radio waves/signals, or just irradiating passively?
Article at physicsweb says:
When the craft were at distances of between 20 and 70 astronomical units, researchers found that the Doppler frequency of microwave signals that were bounced off the craft drifted at a small, constant rate
So, passive it seems.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" but "That's funny..."'
I have it on the wall over my bench. It helps when the data goes all weird on me.
There is a reason for everything. Sometimes that reason just sucks.
Affect and effect are two different verbs, with related but quite different meanings.
Affect is the more common. To affect something is to alter it, usually but not always in a harmful way.
Effect is less common. To effect something is to cause it to happen. I noticed people starting to use this more commonly about eight years ago. Soon afterwards, people started to use the verb "to effect" instead of the verb "to affect", unaware of the difference in meaning. The difference is so strong that these people often end up saying the opposite of what they mean.
here is a good reference.
It would be hard to imagine that the behavior of light would not change as it crossed these boundaries. I would expect some sort of refraction, etc. as it changed from one medium to another. Observations do not bear this out, although I know of nothing off of the top of my head that would disprove your idea.
For all we know the formula for the gravitational force has a couple more terms. I seem to remember coming across an advanced formula for the electric force that contained a couple of more terms, that were generally insignifcant compared to the main term kq1q2/e^2 that most people recognize. Why not the gravitational too? I have heard some physicists advocate for a 1/r term I believe. Can anybody back up any of what I said about the electric force or arguments for an extra term in the gravitational force?
Let's go Hurricanes!!! 2006 Stanley Cup Champions!!!
Lets assume two objects are spaceship A and spaceship B. To make things simple, lets assume the speed of light is 100 m/s and both the spaceships are travelling at 60 m/s towards each other (relative to a person at rest). But, since they are travelling at high speeds, adding up 60+60 to get 120 doesn't work because spaceship A won't measure the speed of spaceship B to be 60m/s because they are in a different inertial frame compared to the person at rest and will make different measurements. Relativistic equations have to be used in this case to determine what the observer in spaceship A will measure. The equation used is v = v0*sqrt(1-v^2/c^2) So spaceship A will measure the speed of spaceship B to be 60*sqrt(1-v^2/c^2) = 60*sqrt(1-60^2/100^2) = 60*0.8 = 48m/s So that means relative to spaceship A, spaceship B will be travelling at 60 + 48 = 98 m/s.. still less than the speed of light.
No they aren't, and I don't know where people get this idea.
In special relativity, there is a factor called "beta" which is used to calculate time dilation, spacial contraction, relativistic momentum, etc. It's defined like this:
beta = 1 / sqrt(1 - v^2/c^2)
Where v is your velocity as measured w.r.t. some chosen reference frame.
Now, think about time travel. This would be equivalent to a negative time dilation factor (time moving "backwards"). In other words, a negative beta. People seem to just assume that, if v > c, then beta is negative. But it isn't.
If v > c, then the term (1 - v^2/c^2) is negative. What's the square root of a negative number? It's imaginary. So, if you move faster than light, the beta factor becomes imaginary. You aren't moving backward in time -- you are moving in imaginary time.
To sum up, traveling faster than light doesn't make you go backward in time. It's a meaningless concept. Unless, of course, you are willing to accept the existence of "imaginary time."
It is standardly accepted math that a divide-by-zero is absurd but the following is true:
Given the numbers n,m, then for any value of n, as m approaches zero, n/m approaches infinity. As such, this is strictly speaking an asymptopic problem, but it is reasonable to say that a zero volume object with a non-zero mass has functionally infinite density.
"Stumble before you crawl"
Tell that to the neutrino guys I've worked with.
Neutrinos have non-zero rest mass, and hence are known and detectable dark matter. (It's worth noting, though, that they're "hot" dark matter, and "cold" dark matter is more like what you're complaining about. Neutrinos also only account for maybe 20% of the needed dark matter.)