Until 17 February 1998, the heliocentric radial distance of Pioneer 10 has been greater than that of any other manmade object. But late on that date Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year.
I have tried to get some people at NASA Advanced Concepts interested in a voyage to Sedna (now near perihelion at ~ 89 AU). Sedna is especially interesting because of its orbit - there is a chance it is an interloper from another solar system. It's so far away that a trip in a reasonable time would require a higher velocity than Voyager.
Note, by the way, that the next double Jupiter - Saturn orbital assist would require Jupiter passage ~ 2018 and Saturn passage in ~ 2019. These only repeat every 19.87 years, so we better get to it. With a double gravity assist and ion propulsion, we could get to Sedna in a reasonable time.
The two Voyagers are gyroscope stabilized, so they don't need fuel for attitude control.
They are powered by Plutonium 238 RTG's, and that power is steadily declining as the Plutonium decays and the thermocouples age. I think that is what the article is referring to. I wouldn't call them fuel.
It would be nice to think that one day we'll reach a technological level that allows us to overtake Voyager 1. I'm not that hopeful though. I think that the head start Voyager 1 has means that it always will be more remote from Earth than anything else constructed here. Excluding Pioneer 10, that is.
If you look at this picture, it sure does look like Voyager 1 may have left the solar system (in a plasma sense) in late August. (In other words, it is no longer seeing protons from the solar wind, which means it may be outside of the Sun's bubble of plasma, and into the interstellar medium.
So that the people finding big things in the Kuiper belt don't get to call the ones bigger than Pluto planets, and thus give us a solar system with 15 or 20 planets.
(Hey, I didn't say it was a good reason, but that is what I heard drove it.)
One tiny problem with that, though: Ceres is a bit further out from the sun than Mars... as in way the hell out there.
It does have potential for fueling an orbital colony or, well, any colony that isn't at the bottom of a big gravity well. OTOH, if Mars is a screamer of a target to hit, I can only imagine what it would take to hit a relatively microscopic-sized target that's way further out, and somewhat surrounded by asteroids.
Sounds like fun, though.
Should be no problem, especially once Dawn gets there and nails down the orbit.
Note, however, that there is plenty of water on Mars, a good deal of it accessible from the surface at the poles.
Frame dragging and gravitational wave production can be straightforwardly calculated and are very small. These are pretty well understood effects of well tested theories so, no, I don't find it easy to imagine (how to get the desired effect).
I also don't see how any of this can evade the Messenger results, which should see a huge signal and doesn't.
There are multiple distance measures in cosmology - they are all in principle exact (at least, if you know all your cosmological parameters), but they differ significantly once you start getting above about 1 billion light years. Much above that, and they can differ incredibly much. Some of these measures are based on idealized measurements, others on the physics directly.
Some measures used in cosmological work are,
- proper motion distance (the distance a parallax measurement would give you) - luminosity distance (the distance you would infer from the apparent brightness of a standard candle) - angular diameter distance (the distance you would infer from the apparent angular size of a standard sized object). The angular diameter distance is notorious for getting smaller if you get far enough away in many cosmologies (including, apparently, the one we live in). - look back distance (if you imagine that everyone has a clock synchronized at the big band, the difference between your time and the time you would read on the remote clock, if you could read it). This is also called the light travel time. - proper distance (what some long yardstick would read). - comoving distance (the proper distance divided by the scale factor - 1 plus the redshift, z - for the remote observer, to get a distance that doesn't change with cosmological time).
And, finally, each cosmological model will have a coordinate distance (the difference between the coordinates of two different places), which need not have a simple relation to any of the above.
It is fair to say that one of the easiest ways to make a fool of yourself in cosmology is to mix up distance scales. (As an additional cause of mixups, only proper distances can be subtracted - for the rest, the distance between A and B is NOT the difference of the distance to A and the distance to B, even if A and B are on a straight line as seen from the Earth.)
In this case, the Gamma Ray Burst 090510A was at a red shift of 0.897. Go to the Cosmology Calculator and you find that that
For Ho = 71, OmegaM = 0.270, Omegavac = 0.730, z = 0.897
It is now 13.666 Gyr since the Big Bang. The age at redshift z was 6.376 Gyr. The light travel time was 7.290 Gyr. The comoving radial distance, which goes into Hubble's law, is 3053.8 Mpc or 9.960 Gly. The angular size distance DA is 1609.8 Mpc or 5.2505 Gly. The luminosity distance DL is 5793.1 Mpc or 18.895 Gly.
The proper distance is (1+z) times the comoving distance, or 18.89 Gly.
I am not qualified to comment on the accuracy of the findings and their subsequent interpretation of the data. However, as the senior scientist Giovanni Amelino-Camelia suggested, "But the claim that their analysis is proving that space-time is 'smooth with Planck-scale accuracy' is rather naive." (He was the first one to theoretically suggest methods with which one could test for the "discreteness" of space-time)
Is it the artifact of the social media/e-news and the ever growing need for public attention to science (which translates into the elusive funding dollars), that lately a lot of discoveries are being touted as "physics defying", "life altering" etc before they are scrutinized thoroughly?
Maybe, but I don't think so in this case. Note that Amelino-Camelia is not saying that they can't be right, just that there is some more due diligence that needs to be done. That is rather different from, e.g., the superluminal neutrino case (which actually, note, disagreed with neutrino speed estimates from the 1987-A supernova). This particular case has actually been building for a while (this is not the first look at the dispersion of spacetime over cosmic distances).
If you ask, at what scale do virtual particles (the stuff continually popping in and out of existence) get so massive that they have gravitational effects (i.e., form little mini black holes), you get the Planck mass, and the Planck length and time come from that. It is, however, very hard to see how you can reconcile these experimental results with the notion that mini-black holes really are popping in and out of existence at the Planck scale. That may mean no space-time foam (what is supposed to result from this violent behavior at the Planck scale).
This is not a problem for General Relativity, but it is a problem IMHO for quantum gravity. The old question, at the Planck scale does General Relativity become more like quantum mechanics, or does quantum mechanics become more like General Relativity, may get an answer that the quantum mechanicians do not like.
I believe that was Michael Faraday, in London. If you search you will find various versions of this quote and its setting (that he said it to the Prime Minister, for example), but I heard that he said it at the Friday Evening Lectures at the Royal Institution, which he started and was very popular at. These included demonstrations, and it wouldn't surprise me much if that was a regular question, to which he had a regular answer.
...for donations over $10.000.000 you will get to place yourself in the path of the beam, hopefully developing superpowers (and hopefully not supercancer or super radiation poisoning)".
I think that the outgassing from the vaporing flesh would ruin the vacuum containment system.
Slashdot Mirror
Well,V1 had only 2 gravity assists...
And, as I posted above, the Jupiter-Saturn dual gravity assists come up every 19.87 years - the next will be at the end of the decade.
Sorry, but wrong. Voyager I overtook Pioneer 10 in 1998 :
Until 17 February 1998, the heliocentric radial distance of Pioneer 10 has been greater than that of any other manmade object. But late on that date Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year.
I have tried to get some people at NASA Advanced Concepts interested in a voyage to Sedna (now near perihelion at ~ 89 AU). Sedna is especially interesting because of its orbit - there is a chance it is an interloper from another solar system. It's so far away that a trip in a reasonable time would require a higher velocity than Voyager.
Note, by the way, that the next double Jupiter - Saturn orbital assist would require Jupiter passage ~ 2018 and Saturn passage in ~ 2019. These only repeat every 19.87 years, so we better get to it. With a double gravity assist and ion propulsion, we could get to Sedna in a reasonable time.
The two Voyagers are gyroscope stabilized, so they don't need fuel for attitude control.
They are powered by Plutonium 238 RTG's, and that power is steadily declining as the Plutonium decays and the thermocouples age. I think that is what the article is referring to. I wouldn't call them fuel.
It would be nice to think that one day we'll reach a technological level that allows us to overtake Voyager 1. I'm not that hopeful though. I think that the head start Voyager 1 has means that it always will be more remote from Earth than anything else constructed here. Excluding Pioneer 10, that is.
Voyager 1 is currently the most distant man-made object, and is more distant than Pioneer 10.
If you look at this picture, it sure does look like Voyager 1 may have left the solar system (in a plasma sense) in late August. (In other words, it is no longer seeing protons from the solar wind, which means it may be outside of the Sun's bubble of plasma, and into the interstellar medium.
If so, it has impeccable timing.
So that the people finding big things in the Kuiper belt don't get to call the ones bigger than Pluto planets, and thus give us a solar system with 15 or 20 planets.
(Hey, I didn't say it was a good reason, but that is what I heard drove it.)
One tiny problem with that, though: Ceres is a bit further out from the sun than Mars... as in way the hell out there.
It does have potential for fueling an orbital colony or, well, any colony that isn't at the bottom of a big gravity well. OTOH, if Mars is a screamer of a target to hit, I can only imagine what it would take to hit a relatively microscopic-sized target that's way further out, and somewhat surrounded by asteroids.
Sounds like fun, though.
Should be no problem, especially once Dawn gets there and nails down the orbit.
Note, however, that there is plenty of water on Mars, a good deal of it accessible from the surface at the poles.
How can an asteroid of only 330 mile wide have volcano that spewed out lava ?
Lot's of radioactive Aluminum-26, which melted all sorts of things in the very early solar system. (Vesta is thought to be near-primordial.)
Frame dragging and gravitational wave production can be straightforwardly calculated and are very small. These are pretty well understood effects of well tested theories so, no, I don't find it easy to imagine (how to get the desired effect).
I also don't see how any of this can evade the Messenger results, which should see a huge signal and doesn't.
Argh - a typo - there is both a parallax distance and a proper motion distance, and they are not the same.
Neither are used much as we can't measure proper motions or parallaxes at cosmological distances... yet.
Mine was, but his was 16:45.
I didn't see any spelling... And, 53 seconds in, he calls himself "a Doctor," not "the" Doctor.
There are multiple distance measures in cosmology - they are all in principle exact (at least, if you know all your cosmological parameters), but they differ significantly once you start getting above about 1 billion light years. Much above that, and they can differ incredibly much. Some of these measures are based on idealized measurements, others on the physics directly.
Some measures used in cosmological work are,
- proper motion distance (the distance a parallax measurement would give you)
- luminosity distance (the distance you would infer from the apparent brightness of a standard candle)
- angular diameter distance (the distance you would infer from the apparent angular size of a standard sized object). The angular diameter distance is notorious for getting smaller if you get far enough away in many cosmologies (including, apparently, the one we live in).
- look back distance (if you imagine that everyone has a clock synchronized at the big band, the difference between your time and the time you would read on the remote clock, if you could read it). This is also called the light travel time.
- proper distance (what some long yardstick would read).
- comoving distance (the proper distance divided by the scale factor - 1 plus the redshift, z - for the remote observer, to get a distance that doesn't change with cosmological time).
And, finally, each cosmological model will have a coordinate distance (the difference between the coordinates of two different places), which need not have a simple relation to any of the above.
It is fair to say that one of the easiest ways to make a fool of yourself in cosmology is to mix up distance scales. (As an additional cause of mixups, only proper distances can be subtracted - for the rest, the distance between A and B is NOT the difference of the distance to A and the distance to B, even if A and B are on a straight line as seen from the Earth.)
In this case, the Gamma Ray Burst 090510A was at a red shift of 0.897. Go to the Cosmology Calculator and you find that that
For Ho = 71, OmegaM = 0.270, Omegavac = 0.730, z = 0.897
It is now 13.666 Gyr since the Big Bang.
The age at redshift z was 6.376 Gyr.
The light travel time was 7.290 Gyr.
The comoving radial distance, which goes into Hubble's law, is 3053.8 Mpc or 9.960 Gly.
The angular size distance DA is 1609.8 Mpc or 5.2505 Gly.
The luminosity distance DL is 5793.1 Mpc or 18.895 Gly.
The proper distance is (1+z) times the comoving distance, or 18.89 Gly.
I would not go against the good Dr..
I assumed, however, he was talking about the macro scale, not the micro.
Supposed to be, on purely theoretical grounds. This is evidence against that notion.
I am not qualified to comment on the accuracy of the findings and their subsequent interpretation of the data. However, as the senior scientist Giovanni Amelino-Camelia suggested, "But the claim that their analysis is proving that space-time is 'smooth with Planck-scale accuracy' is rather naive." (He was the first one to theoretically suggest methods with which one could test for the "discreteness" of space-time)
Is it the artifact of the social media/e-news and the ever growing need for public attention to science (which translates into the elusive funding dollars), that lately a lot of discoveries are being touted as "physics defying", "life altering" etc before they are scrutinized thoroughly?
Maybe, but I don't think so in this case. Note that Amelino-Camelia is not saying that they can't be right, just that there is some more due diligence that needs to be done. That is rather different from, e.g., the superluminal neutrino case (which actually, note, disagreed with neutrino speed estimates from the 1987-A supernova). This particular case has actually been building for a while (this is not the first look at the dispersion of spacetime over cosmic distances).
Yes, I think you are right (and that they were sloppy about their orders of magnitude).
If you ask, at what scale do virtual particles (the stuff continually popping in and out of existence) get so massive that they have gravitational effects (i.e., form little mini black holes), you get the Planck mass, and the Planck length and time come from that. It is, however, very hard to see how you can reconcile these experimental results with the notion that mini-black holes really are popping in and out of existence at the Planck scale. That may mean no space-time foam (what is supposed to result from this violent behavior at the Planck scale).
This is not a problem for General Relativity, but it is a problem IMHO for quantum gravity. The old question, at the Planck scale does General Relativity become more like quantum mechanics, or does quantum mechanics become more like General Relativity, may get an answer that the quantum mechanicians do not like.
" theories suggest the pixels should measure the size of the "Planck length," or about a billionth of a billionth of the diameter of an electron"
I thought electrons and all truly elementary particles had no size whatsoever, they were ideal points
Not on the Planck scale (or ,at least, it was assumed, not on the Planck scale). Nothing should be ideal (i.e., a point) on the Planck scale.
I believe that was Michael Faraday, in London. If you search you will find various versions of this quote and its setting (that he said it to the Prime Minister, for example), but I heard that he said it at the Friday Evening Lectures at the Royal Institution, which he started and was very popular at. These included demonstrations, and it wouldn't surprise me much if that was a regular question, to which he had a regular answer.
The innovation at CERN came from government funded money. You cannot dispute that.
All high energy experimental physics since roughly 1940 has been government-funded research.
Oh, they've got themtoo.
...for donations over $10.000.000 you will get to place yourself in the path of the beam, hopefully developing superpowers (and hopefully not supercancer or super radiation poisoning)".
I think that the outgassing from the vaporing flesh would ruin the vacuum containment system.
The smoking gun will be shocked quartz.