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Jan
12
answered 3D glasses giving the opposite effect to that expected
Dec
6
comment Does the universe emit Hawking radiation?
@JohnRennie, There is nothing magic about a time like 100 Byr that will suddenly change our current universe into an exactly de Sitter universe. Because of the accelerated expansion caused by dark energy, the ordinary and dark matter content will continuously approach zero but will never magically become zero, so if there will eventually be a horizon, why isn't there already a horizon?
Nov
21
awarded  Popular Question
Nov
17
comment The Sun as a gravitational lens
@tomh - According to wolframalpha.com/input/… it would take 3 days 4 hours 14 minutes 12.63 seconds :-) But note that this is the time from when the radio waves just graze the Sun to when they are received at the radio telescope. So that number doesn't mean much. The waves have been travelling in space for many many years (depending on the distance in light years of the source).
Nov
1
awarded  Generalist
Nov
1
comment How do we know Dark Matter isn't simply Neutrinos?
@HarryMacpherson - There are nine general classes of evidence for DM: 1. Galaxy rotation curves, 2. Velocity dispersions of galaxies, 3. Galaxy clusters and gravitational lensing, 4. Cosmic microwave background, 5. Sky surveys and baryon acoustic oscillations, 6. Type Ia supernovae distance measurements, 7. Lyman-alpha forest, 8. Structure formation, 9. Bullet Cluster. Each of these classes includes MANY individual measurements. If that is NOT overwhelming evidence for DM then I don't know what could possibly convince you. I give up. You can get the last word in. I quit.
Oct
19
comment How do we know Dark Matter isn't simply Neutrinos?
@HarryMacpherson : The exact particle that is the DM particle is unknown and is being searched for and it's properties have not been determined. However, it is known that the DM must exist and that is must be particles. That is what there is a huge amount of evidence for.
Oct
19
comment Are we increasing the gravity of Earth with our population?
@LightnessRacesinOrbit - Today I cannot find the source on the web for the 10 tons per day of meteors, but I did find a source for 5 tons: onlinelibrary.wiley.com/doi/10.1029/2000GL012621/full - the number per year gives about 5 ton per day. Also, the 250 tons of atmosphere loss per day is from Wikipedia: en.wikipedia.org/wiki/Atmospheric_escape - 3kg/sec of hydrogen gives 250 tons per day.
Oct
18
comment Are we increasing the gravity of Earth with our population?
@trichoplax - I see you already have answers to the question Chris White added for you. To those answers, I would just add that the products of photosynthesis will increase the mass of the output products compared to the inputs since some of the Sun's energy goes into the bonds - in other words it is enothermic reaction - the question Chris White added for you is about exothermic reactions. The effect will be unmeasureable, but it must exist.
Oct
18
awarded  Necromancer
Oct
17
awarded  Nice Answer
Oct
16
answered Are we increasing the gravity of Earth with our population?
Oct
12
comment How do we know Dark Matter isn't simply Neutrinos?
@HarryMacpherson You are wrong. There is a HUGE amount of evidence behind the Standard Model of Cosmology and the standard model says DM = 5 x Ordinary Matter. See en.wikipedia.org/wiki/Lambda-CDM_model . The CMB alone is a huge part of the evidence, but there are many other sources also. That amount of evidence is FAR beyond the level of "conjecture".
Oct
12
comment Could the acceleration of universe expansion be caused by gravity itself?
@frodeborli It just will not work - gravitational fields are ONLY spherically symmetric about the source of gravity (the BH). At any other point (like us) it will be very non spherically symmetric.
Oct
10
comment Could the acceleration of universe expansion be caused by gravity itself?
@frodeborli - that would not work. The amount that a light ray is bent is larger for rays that passes close to the BH when compared to light rays that passes further from the hole.
Oct
10
comment Could the acceleration of universe expansion be caused by gravity itself?
@DrunkenCodeMonkey - that would not result in an isotropic universe - the direction towards the black hole would be different than the direction perpendicular to that line.
Oct
6
awarded  Yearling
Jul
20
awarded  Nice Answer
Jul
17
revised Why do neutrino oscillations imply nonzero neutrino masses?
Added latex
Jun
29
awarded  Nice Answer