Jump to content

Leaderboard


Popular Content

Showing content with the highest reputation on 06/10/20 in all areas

  1. 1 point
    The video depicts a finite number of elements of a finite height. It says that a dimension is small, “almost zero small” which is wrong I don’t see why “infinte” should be mentioned at all. Don’t subject yourself to this video any further. Someone else on youtube must have done a better job.
  2. 1 point
    You're both welcome. A couple of things more. First, I just wanted to add that Fermi was no idiot, of course. But the assumptions he made date back to 1950. We know much more about planets now. Something we know now, for example, is that the Earth-Moon system is far from typical. The Moon is an unusually large satellite and has a rather bigger than normal stabilizing effect on the Earth's tilt. To the point that astronomers are starting to look upon the Earth-Moon system as a binary planetary system, rather than a standard planet and its small satellite or group of satellites. The huge tidal effect that the Moon has on the Earth is believed to have played a major part in the origin of life at least during the first billion years, stirring the chemicals dissolved in water and thus triggering volume reactions (much quicker and efficient) rather than surface effects. https://www.space.com/12464-earth-moon-unique-solar-system-universe.html Another factor is the presence of outer giants like Jupiter and Saturn, for billions of years playing the role of shuttles for asteroids from the Kuiper belt, etc. Water and amino acids in the asteroids are also thought to have been very important. In case any of these factors were found to be essential to the appearance of life, it could be a basis to estimate the number of solar systems in the Milky Way that satisfy similar conditions. Would other different sets of conditions be just as good, or maybe even better? I don't know. I don't know if anybody knows. Drake's equation came later than Fermi's argument (in 1961). Actually, I think Drake's equation is a more promising ground for estimating the chance of there being intelligent life forms, among other things, precisely because, although ambitious, it's a much less assuming parametrization of the probability, rather than an equation or a "closed" calculation. There is room for re-estimating the factors as we learn more about the phenomenology of galactic (or extra-galactic) solar systems. Plus the last factor is, if I'm not mistaken, the probability that a civilization will be able to send signals, rather than travel to Earth, which significantly increases the odds. Fermi was concerned with interstellar travel, AFAIK. The detection of signals with a message in them will probably be the first evidence, if there ever is one, of some form of intelligent life besides us in the universe, rather than the flight of UFOs. But here's the bad news, IMO: Take a look at this table with time gaps separating the appearance of new levels of organization: First prokaryotes (from Earth's formation): 1 billion years First eukaryotes (from prokaryotes): 800 million years First multicellular eukaryotic organisms (from single-celled eukaryotes): 2 billion years First intelligent life (from multicellular eukaryotes): 700 million years Average for the appearance of a new level of organization: 1.125 billion years Now suppose there's a planet out there with something like eukaryotes (cells with a nucleus). You're going to have to sit there waiting for 1.1 billion years for you to see anything interesting to happen if the above table is anything to go by. That's the problem.
  3. 1 point
    Perimeter is a one dimensional attribute, while area is two dimensional. IOW, you need one piece of information for one and two for the other. That allows for considerable ( infinite ) variation.
  4. 1 point
    This will help you better understand those above spacetime diagrams they look to be very similar to the ones produced by Lineweaver and Davies. The other factor you must also remember is the radius change of the observable universe. This gives the illusion of a curved worldine. However the worldline itself is close to flat. The volume changes are incorporated into these diagrams. Hope this helps https://arxiv.org/abs/astro-ph/0310808 One of the main problems with these diagrams at higher z scales is that the time period between z=10 and Z=1100 is that the time period between that change is rather miniscule due to the non linearity of the Z scale. So it is incredibly difficult to show this on graph.
  5. 1 point
    Consider a rectangle that is 100m long by 1cm: its area will be 1 m2. and its perimeter is about 200m. This is the same as a square 1m x 1m, but that has a perimeter of only 4m. Why? Because one is long and thin and the other is square. A circle is even more "efficient" than a square and so has a shorter (the shortest) perimeter for a given area.
  6. 1 point
    Nice post. On the same stance: Inside versus Outside: a past light cone spreads always outside. The past is always far away from the observer (The galaxies are several million years in the past) and the more you get closer the more you reach present time (our Moon is only a few seconds in the past. Ultimately, the present will be reached when contacting the observer. The direction of time is from the outside (Past) to the inside (Present) Now maybe you can equate "big" with "outside", I'll have to think about it.
  7. 1 point
    You beat me to it. I was going to post this under the title "Good things can come in small packages". The annual death toll from malaria runs just under half a million. Great to see a potential solution. Some more information on malaria in general here. (It's from the WHO, so Trump supporters should look away now.)
  8. 1 point
    I'm no expert, but you should be taking this very seriously. Gloves, masks, regular washing of hands, social distancing should all be adhered too. Granted, it's easier to say than it is to do, do you even has access to face masks and gloves? I don't nor can I get any. The moderator Charon Y is a good person to follow on this subject. Very knowledgeable and informative. Try reading through the corona virus mega thread. Take care. Stay safe. 🙏🏻
  9. 1 point
  10. -1 points
    As a philosophical point, how can you say that a photon with a different wavelength and (in some cases) polarisation is not "new"? (Also, learn to spell fluorescence).
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.