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spartan45

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Everything posted by spartan45

  1. Omnifarious, I like your post’s curiosity and determination to find answers, but you have brought up too many points for me to cope with so I thought I’d start with gravity. Gravity is intriguing; the best description of its nature I recently found is from the reference below the summary from that reference titled ‘Does the influence of gravity extend out forever?’ ‘In summary, the influence of gravity only extends to the edge of each gravity group. Beyond that, spacetime no longer behaves like gravity. It's not that the gravitational attraction of a star simply gets too weak to noti
  2. Apollo 14 (1971) Astronaut Alan Shepard describes what he sees after disembarking from the ‘Antares’ lunar module “-Look up in the black sky, there’s no reflection no diffusion and seeing another planet; planet Earth.” “It certainly is a stark place here; I think it’s made all the more stark by the sky being completely black.” REF: The TV documentary ‘Moon Shot’ from the Smithsonian Channel (2020). Apollo 16 (1972) Mission science experiments included The Far Ultraviolet Camera/Spectrograph which took pictures and spectra of astronomical objects in ultraviolet light. The Far Ultravio
  3. As others have already stated the visible universe is finite and just does not have enough stars to light up all of the sky. I did wonder if dust clouds between the stars might be absorbing a lot of the starlight so it wouldn't shine through to us. But apparently scientists tell us that the dust itself would absorb so much energy from the starlight that eventually it would glow as hot and bright as the stars themselves. So I guess dust the dust cloud idea is a non-starter. For a good comprehensive answer to this post’s question, I recommend the reference below. https://spacepla
  4. TomBooth; thank you for posting this interesting topic, very brave of you to challenge both the second law of thermodynamics heat flow statement: ‘Heat flows spontaneously from a substance at a higher temperature to a substance at a lower temperature and does not flow spontaneously in the reverse direction’ and also Carnot’s principle, (An alternative statement of the second law of thermodynamics), ‘No irreversible engine operating between two reservoirs at constant temperatures can have a greater efficiency than a reversible engine operating between the same temperatures. Furthermore, all rev
  5. I appreciate the Sun is a star. I must admit the question and wording ‘at what altitude can stars been seen in daylight?’ does seem a bit weird, but then so does the seemingly black void witnessed by astronauts and visual spectrum cameras above the Earth’s atmosphere from spacecraft and the International Space Station when the Sun is not blocked by the Earth. I am now curious how the Hubble Space Telescope overcomes the problem of seeing stars (other than the Sun which it must not look at because it is so bright it would destroy its sensitive instrumentation) in daylight, all I can think of is
  6. The existence of the Hubble Space Telescope is used as proof that stars can be seen in daylight above the atmosphere. The Hubble ST uses 3 spectral ranges, the near-UV (pivoted at 300nm), Visual light (380nm-740nm) and a limited infra-red (800nm-2500nm) capability. Here’s the thing; can the Hubble ST see stars in daylight using the normal human visual light spectral range (380nm-740nm), or does it have to resort to using the near-ultra violet spectral range ( pivoted at 300nm) to see stars in daylight? The only other optical space telescope I’m aware of is the Chang’e 3 Lunar-based ultraviol
  7. Special relativity means moving clocks run slow. The challenge is which clock is moving, so I hope this experiment (Keating) carried out in the 70’s using an aircraft heading W and then repeating the procedure heading E, while carrying atomic clocks synchronised with a master atomic clock at an observatory in the United States helps make sense of it: The clock on the W bound aircraft was travelling against the East bound spin of the Earth, (rather like a person walking the wrong way along a conveyor and not moving very much), while the master atomic clock in the United States was moved faste
  8. It is my understanding that an additional chip was fitted to the power steering, before leaving the factories, to detect if there was any movement of the steering wheel whilst the car was moving. If there was none, it would put the car into ‘clean’ mode to cheat the rolling road emission test, reverting back to ‘dirty’ mode when it detected steering wheel movement at the end of the test. I was amazed at how simple, but effective, this method of foiling the world’s diesel car emissions regulations appears to have been. We need to be watchful.
  9. Does anyone know if an individual is allowed to describe how the emissions test was cheated?
  10. Uranium is in short supply on the Moon. Ref: https://www.space.com/8644-moon-map-shows-uranium-short-supply.html Thorium (Th) is plentiful at Mare Imbrium on the near side and on the Moon where the lander Chang’e 3 and its rover, Yutu (Jade Rabbit) landed (44.12 deg N, 19.51 deg W) on 14 December 2013. Thorium is also plentiful in the south-pole Aitken Basin region on the far side of the Moon within which lies the Von Karman crater where the lander Chang’e 4 and its rover Yutu 2 (Jade Rabbit 2) landed (44.8 deg S, 175.9 deg E) on 3 January 2019. Ref: http://www.planetary.org/blogs/emily-lakdaw
  11. True. Thank you for correcting me; indeed, it was not astrology.
  12. Apologies for posting this after OceanBreeze has answered so well but I’d already written it and I need clarification on the Doppler Red shift equation. Special relativity means moving clocks run slow. Alice’s clock is moving in respect to Bob’s clock on Earth. The time dilation equation is: ∆t0 = ∆t√ 1 – v2/c2 ∆t0 = Alice’s spacecraft time interval (in light years for this example) ∆t = Bob’s Earth based time interval in light years = 3/0.6 = 5 v = spacecraft velocity 0.6c c = speed of light (2.99792458x108 m/s) (3.0x108) rounded (Cancels out in this example) ∆t0 = ∆t√1 –
  13. I just noticed these posts of 2016 which I think are interesting. Is this an example of noble intentions to promote further education, (also see the titles of other papers then downloaded), while testing even my view that astrology is not fiction; below are extracts (two short sections of text) from: NBER WORKING PAPER SERIES SEASON OF BIRTH AND LATER OUTCOMES: OLD QUESTIONS, NEW ANSWERS Kasey Buckles Daniel M. Hungerman Working Paper 14573 http://www.nber.org/papers/w14573 NATIONAL BUREAU OF ECONOMIC RESEARCH 1050 Massachusetts Avenue Cambridge, MA 02138 December 2008 ‘We find that women g
  14. With reference to 8 April 2017 post above, low sunspot activity seems to cause pessimism, so markets fall. The various world financial falls are approximately in line with the low sun spot activity start point of October 2018: Ref: https://www.spaceweatherlive.com/en/solar-activity/solar-cycle There are many articles about world stock markets falling in October 2018: Ref: https://edition.cnn.com/2018/10/31/investing/stocks-markets-october/index.html Ref: https://www.marketwatch.com/story/why-the-dow-tumbled-600-points-and-the-nasdaq-fell-into-correction-territory-for-the-first-time-in-2-years-
  15. (1) No, I simply wanted to keep the question short. (2) Venus has an apparent magnitude of about -4.8, brighter than the estimated -2.2 of the sky as seen from the ground in daylight, so may be visible then. Jupiter is too close to the Sun and too dim at -1.74. Sirius -1.47, not present during daylight and too dim anyway, Mars 0.05, too dim. Except for the estimated -2.2 of the sky from ground level, apparent magnitude and relative position of the planets and star listed will vary with time and location so only valid 5th Dec 2018. Ref: https://www.timeanddate.com/astronomy/night/usa/jefferso
  16. Here is an interesting 1965 documentary ‘BBC Horizon, 1965 Man in Space’ The space race was about the halfway point. Interest in space exploration was intense and yet it appears no answer was found to what altitude can stars be seen in daylight because at about two minutes into the ‘BBC Horizon, 1965 Man in Space’ documentary Frank Borman states ‘During the daytime we were unable to see the stars, this confounds the scientist, but perhaps it was due to light scattering on our windows or perhaps it was due to the Earthlight reflection. We were unable to see the stars in the daytime.’ The int
  17. On 20th November 1984 a new legal entity was born in California called the SETI Institute. Its roots were Project Cyclops: A Design Study for a System of Detecting Extra-terrestrial Intelligence in 1971. A project to search for artificially generated radio signals from a distance of up to 1,000 light-years. SETI states ‘Our mission is to explore, understand, and explain the origin and nature of life in the universe, and to apply the knowledge gained to inspire and guide present and future generations. We have a passion for discovery, and for sharing knowledge as scientific ambassadors to the p
  18. The gore numbers are driven by 4 factors: · Fabric width (usually only a factor in vertically cut balloons – which have gone out of fashion) · Aesthetics · Load tape strength · Panel length · Cost o Fabric Width: if you cut the balloon with vertical panels then the number of gores must greater than balloon diameter / fabric width o Aesthetics: Smooth balloons are better for putting artwork onto. The gores need a bit of “bulge” to shed the load into the vertical tapes, so more gores means a smoother balloon. o Load tape strength: One load tape pe
  19. To capture stars using a still camera it is usual to employ a 15sec exposure but a camcorder records at either 30 (NSTC ) or 25 (PAL) frames per second so a camcorder is better suited than a normal still camera to use from a moving spacecraft. In this post I’ll show that even with a little light pollution, thin low clouds and a high half Moon at night here on Earth, stars that can be seen easily with the naked eye can also be captured using a camcorder like the Sony DCR-DVD handycam. The Sony has ’NightShot’, super ’SteadyShot’, 20x optical zoom (other models have more) and the ability to disa
  20. I am not so sure that cross-sectional area should be used as a variable as the object could be tumbling or start tumbling so perhaps it is better to use object density instead. The 300 km for low density and 240 km for high density height at which objects appear to start experiencing a sharp 10 fold increase in orbit decay is too vague because it is dependent on varying solar wind and environmental conditions; Earth orbital velocity of satellites could be reduced by the solar wind in various ways. It is well documented how the solar wind pushed balloon satellites around during their life in s
  21. The SAT exam is not really a proper measure of intelligence because it only tests knowledge of relatively simple concepts and ideas; further, its capacity to measure a student’s ability in the use of accumulated specialised knowledge is limited. The bottom line is SAT scores are a limited measure of cognitive abilities and can also vary considerably due to a student’s level of preparation and educational experiences. That said; the scores are probably the best means available to the education system. If I may be so bold, I would like to add that SAT scores can be useful to evaluate ones stre
  22. Not wanting to burst your bubble, but I first experienced this level of A.I. in November 2015 during an international call. It surprised me then, but not much does now. A 2001 computer magazine predicted that A.I. (which had the intelligence of a spider then) would be equal to man in 2020; a very accurate prediction in my opinion. The movies have the downside of advanced A.I. well covered, but benefits probably include progressing medicine, energy, transport and security. I’m not sure if this is relevant, or indeed appropriate to ask here, but if machines become self-aware, I wonder if they mi
  23. I liked the fact you kept it simple, yet it did lead the user to explore possibilities (Bangladesh's capital Dhaka for example had a former name and there appears to be spelling options). So I liked the app and believe in this could be fun and useful as a learning tool. This is just my personal opinion of course.
  24. To anyone interested in true story space adventure, I recommend ‘Secret space escapes’ (2015).The part of this series relevant to this post is ‘shipwrecked P2’at 12m26s through to 13m where astronaut Mike Foale mentions ‘you can’t see the stars during the day’ when describing how the stars were used as reference points for stabilizing the Mir space station’s tumbling spin. Not really surprising because of the Sun’s glare, but reinforces that even at an altitude of about 270 miles, stars cannot be seen in daylight.
  25. Thanks for the feedback. The wiki ref. on my first post showed what looked like a bright star parallax tracking in front of the background stars. Turns out this was an animation of infrared light data and the brown dwarf 'star' cannot be seen in visible light. The reference below from NASA makes it clearer. https://www.nasa.gov/jpl/wise/spitzer-coldest-brown-dwarf-20140425
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