This website is kept for archival purposes only and is no longer updated.
 | |
| ||||| Friday, March 01, 2002 - 09:15 am How far away will Hubble now take images of the cosmos: How far will Hubble be from earth - the farthest point? Then, how many miles beyond will Hubble take images? Will Hubble be capturing images North, South, East, West etc. of the Sun (as a guide)? Appreciate your thoughts on this as I feel it can assist in capturing a better 'feel' of the work Hubble is performing. Good Luck. | |
| ||||| Friday, March 01, 2002 - 09:26 pm "Miles" ?? On a scientific mission? No one there uses "miles"; no one should anywhere else, either; "miles" and their relatives all belong on the scrap heap of history. | |
| ||||| Saturday, March 02, 2002 - 09:50 am I beg to differ! The orbital insertion altitude/ inclination of the space shuttle are posted in nautical miles! | |
| ||||| Saturday, March 02, 2002 - 11:20 am I have inquired about this and was told that the reason that NASA uses miles is that the procedures and software for the STS program were developed before 1988. That was the year that NASA officially went metric, except in a few isolated instances (and those required waivers). I can understand then why they manage their flight control work in miles since we don't want people converting units "on the fly". What this does not excuse is the exclusive use of non-metric units in material released to the public. NASA has plenty of time to do the unit conversions for these, which of course makes them more universally understandable. The Inspector General took them to task recently for failing to comply with their own Metric Directive and since then we've seen more frequent inclusion of metric units in STS reports, though certainly not as often as we should. Of course, there is no reason in this day and age to use non-metric units at all in public materials. Americans watch (and participate in) Olympic events which measure distances in meters and kilometers. Americans run thousands of races in kilometers. Instead of putting metric equivalents in parentheses, NASA should be putting all their releases exclusively in metric units. On the rare occasion that they think someone might have slept through that science class, they could put the non-metric equivalent in parentheses. If NASA has to endure working with obsolescent units for these older programs as a cost-cutting measure, there is no reason why the American public (or the rest of the world), needs to suffer right along with them. J.R. Frysinger, CAMS Dept. of Physics and Astronomy College of Charleston Charleston, SC 29424 http://www.cofc.edu/~frysingj | |
| ||||| Saturday, March 02, 2002 - 03:46 pm Getting back to Betty's original questions: The Hubble Space Telescope can take images of large items such as galaxies as far away as approximately 10 billion lightyears or 60 thousand, billion, billion miles. The Hubble Space telescope orbits the earth and this orbit is nearly a circle. Therefore, it is always roughly the same distance from earth, approximately 353 miles in altitude. This orbit degrades (altitude drops) slowly (a few miles) over a period of years, and the Space Shuttle is used to "reboost" the telescope during servicing missions to help maintain the altitude. This small change in altitude has no effect on how far the telescope can see. Over the course of a year the Hubble Space Telescope can image anywhere in the sky. | |
| ||||| Saturday, March 02, 2002 - 06:42 pm WHEN TAKING OFF INTO SPACE, WHAT KEEPS THE SHUTTLE FROM HITTING ALL THOSE SATELLITES? ARE MOST SATELLITES AROUND 22K MILES? | |
| ||||| Saturday, March 02, 2002 - 07:08 pm Although there are literally thousands of objects in orbit, most of them are fairly small and located over a large span of orbits. 22K miles (36,000 km or 36Mm) is a popular communications satellite altitude (geostationary), but satellites are distrubuted at a variety of altitudes and inclinations. It might seem pretty crowded, but most satellites are smaller than a telephone booth (HST is considered enormous, the size of a bus), and the earth is pretty big. Consider this: At any given time there are about 4000-7000 airplanes in the skies above the earth, but you can often look up without seeing one. | |
| ||||| Sunday, March 03, 2002 - 02:13 am 'Old Codgers' information is useless. Are you using statute or nautical miles? This proves once again how confusing American units are and I support what Jim and Carleton stated in their messages. | |
| ||||| Sunday, March 03, 2002 - 09:53 am Thank you all so much for this input - it is all so very interesting. I am interested in researching a point raised in the Srimad Bhagavatam wherein it states that we have a circumference of the solar system, i.e. 4 billion miles of which the sun, vertically is 2 billion miles in the center-- and I wondered how far Hubble could take us! The circumference is, according to the Srimad Bhagavatam surrounded by a mountain (Lokaloka) - this mountain evenly distributes the sun's rays. The mountain is so tall that beyond the mountain the sun cannot reach, and therein lies planets and so on without light and therefore without life. Far-fetched? Who knows - maybe Hubble does! Food for thought. It appears Old Codger answered my question and it appears not to matter too much whether it is nautical or statute at this point. Again, thanks so much. Have a great day. | |
| ||||| Sunday, March 03, 2002 - 01:35 pm I was reporting in statute miles in answer to Betty's question. However, Let me ask: Is lightyears an accepted SI unit? | |
| ||||| Sunday, March 03, 2002 - 06:04 pm Strictly speaking, the lightyear is not an SI unit. Actually, a year is not an SI unit. There are two types of units: basic and derived. The basic units are meter, gram, second, ampere, kelvin, candela, and mole. Other units, like joule, watt, newton, etc. are derived units built from the basic units. Apart from using prefixes like kilo, centi, etc. there is only one unit for each type of measurement, and for length that unit is the meter, not the lightyear. | |
| ||||| Sunday, March 03, 2002 - 06:08 pm old fart messed up. he means to say that a light-year is the DISTANCE that light travels in one year. he also means to say "cubit" rather than "cubics". i don't know whether this is because his neurons are ossified, or whether his arthritis makes typing difficult. he also refers to a "larry". there is no one here by that name. clearly he is also hallucinating. | |
| ||||| Monday, March 04, 2002 - 06:24 pm Glad to see you have a sense of humor, OldFart. (grin) Dave's pretty close to the mark about the SI and the light year. The seven base (not basic) units are the meter, kilogram (not gram), second, ampere, kelvin, mole, and candela. With those seven base units and their derived units you can measure just about everything but true love. As Dave said, there are 22 specially name derived units and some which have no special name (such as m/s). Actually, most people need to know fewer than a dozen of these. You already know and use some of them, such as the second. The volt, ampere, and watt come to us from 19th century studies of electricity and magnetism, in which U.S. scientists played a big role. There are also some non-SI units that are allowed for use with the SI, such as the minute (min), hour (h, not hr), and day (d). But the week, month, and year are out. The month and year each come in several different sizes so that makes sense. The meter, kilogram, and degree Celsius are about all you need to know along with the ones just mentioned. If you want, you can throw in the liter which is just a special name for 1 dm3, or a cube 10 cm on an edge. That beats trying to learn the more than 2000 non-SI units that Americans have used in the past! Here are some handy metric thumb rules for you. The Earth is 150 Gm from the Sun and 1 Gm = 1 000 000 km. The Earth's circumference is 40 000 km. The Earth travels at 30 km/s around the Sun and the Moon travels at 1 km/s around the Earth. Most "shooting stars" are traveling at 40 to 60 km/s when they hit our atmosphere to cause that quick streak of light. And light travels through spacd at 300 Mm/s or 300 000 km/s. The nice thing about all of this is that I used only two units, the meter and the second. All the rest was dealt with with prefixes, which do the same thing to any other unit they are attached to. No new unit names are needed when going from small to big sizes, as are needed with our series inch, foot, yard, fathom, pole, furlong, mile, and league; the meter and the standard prefixes handle all that and more. | |
| ||||| Monday, March 04, 2002 - 07:01 pm So, what do we do about units of time? Are we also to abandon our clocks in favor of some new base ten equivalent? | |
| ||||| Monday, March 04, 2002 - 09:58 pm For scientific purposes, the proper unit is the second. Also kiloseconds. Can't recall using megaseconds or gigaseconds, but it would be proper. Due to tradition (not just american) we use minutes, hours, days, and years. | |
| ||||| Monday, March 04, 2002 - 10:37 pm Time and angle measurements are the two areas where the Babylonians' legacy will live on for a very, very long time. Decimal time was tried two hundred years ago and never caught on. Decimal angle units (right angle = 100 grads) seem to have a very limited appeal. In those two areas I foresee no change for another century or two, at least. But, for technical work, scientists do indeed use things like kiloseconds and radians. The latter are not even decimally related to the circle or to a right angle, but there are overriding mathematical reasons for using the radian. Won't be seen at Home Depot, though! J.R. Frysinger, CAMS Dept. of Physics and Astronomy College of Charleston Charleston, SC 29424 http://www.cofc.edu/~frysingj | |
| ||||| Monday, March 04, 2002 - 10:41 pm What's the matter with the radian??? I think all of our units should be base pi. It's more intuitive that way. | |
| ||||| Monday, March 04, 2002 - 10:48 pm Have a ball Metric Man. Sell it to the CGPM and to the 6 billion people who are hooked on metric. You'ld have a better chance selling it to Americans who already use awkward units, though. What are your prefixes going to be? Blueberry, apple, and pumpkin? | |
| ||||| Monday, March 04, 2002 - 11:00 pm Sorry JRF, perhaps I should use the metric unit of sarcasm, you didn't seem to catch the American one. By the way, 100 grads per right angle yields a 400 grad circle. Shouldn't that be base 10? | |
| ||||| Monday, March 04, 2002 - 11:09 pm Can't say for sure regarding the grad, Metric Man, since I wasn't around then. Near as I can figure, the French committee considered that they were using one quadrant of the Earth's circumference (equator to north pole) as the basis for 10 000 000 m so they decided to use a quadrant (right angle) as the basis for 100 grad. That's the only hypothesis I can come up with that makes sense to me. Of course, the grad is then within spitting distance of the degree and one might be tempted to point out that the meter is within spitting distance of the yard. The hole in that theory is that the French, 200 years ago, had been using the toise, which was closer to a fathom than to a yard. I get a kick out of the history of development that led to the SI but I haven't seen anything factual about the grad to support or deny my hypothesis. | |
| ||||| Monday, March 04, 2002 - 11:32 pm The grad (or grade in french) is an interesting unit. The word means "degree". What's even more interesting is that a common subdivision is the centigrade (1/10,000 th of a rt. angle). This was the metric angle but it didn't catch on very well. Calculators have been able to compute in grads for years, but I have never found a need for this functionality. | |
| |
