Questions / Suggestions

“I want to give the audience a hint of a scene. No more than that. Give them too much and they won’t contribute anything themselves. Give them just a suggestion and you get them working with you. That’s what gives the theater meaning: when it becomes a social act.” –Orson Welles

It’s like that for all forms of storytelling, including the science I write about here. Some of the best conversations happen not because I know something amazing that I want to share with you, but because there’s something you want to know about, and I know something that can help you get to where you want to be. But since the platform migration that happened last year, there hasn’t been an easy way to do it, and yet I would, as Meaghan Smith would sing,

If You Asked Me.

So, do you have questions? Do you have suggestions?


Image credit: Thao Nelson of

Image credit: Thao Nelson of

Well, let’s make it easy; I’ve set up a new email account just for these contacts: startswithabang at gmail dot com. (If you can’t figure it out, you don’t deserve to have your question answered!)

That’s right, it’s the first-ever officially Ethan-approved way to contact me directly, even anonymously (or pseudonymously) as you like. The only catch is that anything you send me may be used by me, on this blog, as I like, as a prompt for however I may respond. And I caution you in advance, that may involve a little bit of…

Image credit: created at

Image credit: created at So watch it.

Our form that we had here previously broke some time ago, so email is the way to go!


  1. #1 j0h
    September 29, 2013

    Please look through my bad english. It is not my native language.

    Here you have mij email. Plz do not spread my email. TY

  2. #2 Lynn T Fergus
    Fillmore Ut.
    December 20, 2013

    I know i’m coming into the discussion late but I can’t find an answer to this question. Since no one knows what dark matter or dark energy are, how can we know if or how they might effect red shift?

  3. #3 Michael Kelsey
    SLAC National Accelerator Laboratory
    December 21, 2013

    @Lynn #2: Ethan has lots of much better explanations than I can provide, but I think this is simple: both dark matter (DM) and dark energy (DE) are _defined_ by how they affect our cosmological observations. That is, DM _is_ “whatever the stuff is that makes galaxies and clusters much more massive than the things we see with light”, and DE _is_ “whatever the effect is that is causing the expansion rate to increase with time, instead of decrease.”

    The big research project is to try to understand what physical stuff is causing those observations.

  4. #4 Lynn T Fergus
    Fillmore Ut
    December 24, 2013

    Michael, That still doesn’t answer how or if they effect red shift.

  5. #5 Michael Kelsey
    SLAC National Accelerator Laboratory
    December 25, 2013

    @Lynn #4: I guess I’m not entirely clear on what you’re asking.

    1) The expansion of the Universe causes us to observe a redshift of light emitted by distant galaxies. To the extent that the expansion rate of our Universe (containing DM and DE) is different from what it would be if it only contained baryonic matter, the redshift we observe is “affected” by DM and DE.

    2) Concentrations of mass cause a _gravitational_ redshift of light leaving their vicinity. We observe this on Earth and on the Sun. I’m not certain whether the effect is large enough to observe for galaxies or clusters (I rather doubt it). However, if the effect is observable, then the DM present will lead to a larger effect than if only the baryonic matter were there.

  6. #6 Sinisa Lazarek
    December 26, 2013

    @ Lynn

    It’s the other way around actually. I will try to use an analogy. Imagine your friend goes to another city by car. And he tells you that he will call you once he arrives. And let’s say that the car is traveling 100km/h and the city is 200 km away. Now, under normal circumstances, you would expect him to call in 2 hours. But he calls you 1:20 min. You know his car can’t go faster than 100km/h and you now when he left, thus the only conclusion you have is that “something” made his car go quicker… or something shrunk the road.

    We observe the red/blue shift. And since “c” is constant, we can only conclude that “something” messed up the wavelenght.

    One other important thing. Redshift caused by dark matter is different than the one caused by dark energy. DE and DM act very differently.

  7. #7 Sinisa Lazarek
    December 26, 2013

    p.s. DM acts as a regular gravitational shift. With lensing and so on. DE is a peculiar one. It acts on spacetime itself.

  8. #8 Lynn T Fergus
    December 26, 2013

    Thanks guys you really cleared it up for me.

  9. #9 Sinisa Lazarek
    December 28, 2013

    I’ve noticed a very interesting optic effect today on my wall. A small object on my coffee table cast a shadow on the wall, but a reflection which is not really visible on the glass, also cast a reflection of same opacity and size at exactly 90 degrees. Table top is not a mirror, but a transparent glass.

    Would appreciate very much if someone could explain what happens to light in this scenario. Question is about reflection casting a shadow in a particular case.

    I tried googling for it, but couldn’t find anything useful. Having read much about QED lately, am really curious how this effect occurs in QED terms. From point of view of the wall and some photons, both object and reflection are really the same, they cast exactly the same shadow. How come reflection’s shadow occurs in the first place, why isn’t it i.e. lighter or darker? But also it’s a transparent glass, yes from some angles a faint reflection is observed, yet it seems there’s an angle where it’s 100% reflected.. weird a bit again..

    here is a drawing I made to help illustrate it.

    Again, thank you if someone can explain in detail, or at least point me to correct articles. Maybe this effect has a technical name, that could help also. 🙂

    And sorry if this isn’t an appropriate topic… 🙂

  10. #10 Sinisa Lazarek
    December 28, 2013

    p.s. sorry… first sentence should read ” but a reflection which is not really visible on the glass, also cast a SHADOW of same opacity and size at exactly 90 degrees, ON THE WALL”

  11. #11 Sinisa Lazarek
    December 28, 2013

    * bump 🙁

  12. #12 J Duffield
    December 29, 2013


  13. #13 crd2
    February 15, 2014

    Bump test.

  14. #14 faisal jaradat
    September 22, 2014

    where can i read answers ?

  15. #15 Denis Thomas
    south carolina
    December 28, 2014

    Scientists often state that they do not know what time is, but know how to measure it accurately, which is an oxymora. Time is a system of information exchange, how God and men relate events with respect to the rotation of the earth: what you plan to do tomorrow; what you did last year; how long Jesus was in the tomb; how long it took God to create the universe; or how fast something travels all relate to the rotation of the earth. While gravity may affect time-measuring instruments, that is not proof that gravity affects time. If it did then two observers of a star, both located at exactly the same latitude but at a different longitude, such that one observer is a mile higher than the other, would observe the meridian containing the star cross their zenith at different times, with that difference in time increasing each year. You should recognize that this is impossible. Time slowing down or speeding up with speed is also impossible, but a concept derived from Einstein’s fallacy. His fallacy, while observing the clock at the train station and imagining the effects of observation of the clock as the train sped up to hypothetical speeds, was to ignore the time taken for the image from the clock to reach the point of observation. The clock did not slow down, nor did time.

  16. #16 dean
    December 28, 2014

    “Time slowing down or speeding up with speed is also impossible,”

    Since gps satellites would not give correct results without accounting for the effects of time dilation, and since it has been experimentally verified in other ways, your comment was demonstrated to be false before you made it.

  17. #17 jerry anning
    deaeborn hts, mi
    February 6, 2015

    when dark matter is discussed, it almost always talks in terms of something being “the” dark matter particle. is there a reason to assume that it’s not a mix of several kinds of particle?

  18. #18 Ragtag Media
    February 22, 2015

    The more agreeable I see the way people agree only tempers my soul to double fact check.


  19. #19 Wow
    February 23, 2015

    No, nothing stops it being multiple types of matter, Jerry. It’s called “Dark Matter” rather than “THE Dark Matter”, except where the context would make it generic, such as “The library is where you go to get a book to read”.

  20. #20 DGM
    April 23, 2015

    I understand that the Inflation Theory has the expansion of the universe being driven by an Inflation field that had negative pressure and hence pushed on space (negative gravity). And that as space expanded more of the field was created which pushed more. Hence the run-away inflation event that flattened the universe.

    But, when the field collapsed to it’s zero energy state (thus releasing all the energy that eventually became matter) space continued to expand. Why? This almost feels like inertia but space itself doesn’t have inertia (does it) and the energy/matter in space would be at rest as it has nowhere to go. So why did the expansion continue?

    I realize that now (12 billion years later) dark energy is starting to dominate and cause the expansion to speed up but what happened in the first few billion years when the matter and energy should have been pulling on space and causing it to contract?

  21. #21 Michael Kelsey
    SLAC National Accelerator Laboratory
    May 30, 2015

    @Ethan — following your Comments of the Week #62, I would find an overview of the different quantum gravity options extremely educational! Please consider this a “Yes” vote 🙂

  22. #22 Jason B
    June 15, 2015

    I understand that the more dense gas clouds collapse to form the largest stars, and that the larger the star, the more short-lived its life.

    My question is how, then, are there still areas that produce massive stars? Are there areas in galaxies that are super dense but have yet to collapse? That seems unlikely. Are they remnants of past supernovae? That doesn’t seem like there would be enough dust.

    What am I missing?

  23. #23 Bpeth
    June 21, 2015

    I wrote up the answer to the weighing puzzle for any number of coins (or men on an island), see

  24. #24 DanielWainfleet
    July 14, 2015

    (1) Does the strong nuclear force cause an attraction between neutrons? (2) A free neutron has a 12-minute half-life. What prevents neutron decay in an atomic nucleus?

  25. #25 AC
    August 14, 2015

    Not sure if the form submission works, all I get is a re-direct message:

    Dear Ethan,

    What comprises the “empty space” outside the nucleus of an atom? If atoms are >99.9% empty space, what exactly is that ‘space’? Is it a vacuum? Is it strictly made up of energy inherent to space itself a.k.a. dark energy? Or is it something else entirely?

  26. #26 Wow
    August 14, 2015

    It’s space like the stuff separating out the stars. The only difference is that it is very close to the constituents of the atom. It is definitely not anything special or unique.

  27. #27 Alex
    September 12, 2015

    Dear Ethan,

    This is more of a thought than a question but I find it quite entertaining, so here it goes:

    Assuming the inherent danger of the contact with a more advanced civilization (I think Steve Hawking has touched on this idea before) and adding to this the speculation from your article would lead to a rather unsettling conclusion: once the thermonuclear power technology is reached that would essentially set off the doomsday clock to the first encounter whether we like it or not. Since the signal is limited by the speed of light it would probably take many centuries until it finally leads to the detection by other neighboring civilizations. The history teaches us that short interest and greed (certainly so, compared to human life span) always prevails over any other consideration so I’m quite pessimistic that any esoteric argument such as staying stealthy in the interest of the security of longer non-discovery by others will be respected UNLESS the technology of “eternal life” (the means of achieving that are still debatable, whether through AI, uploadable consciousness etc.) is developed first!

    To sum it up: as a civilization, we must first mature to the status of continuous consciousness (through “eternal life” technologies etc.) and only THEN indulge (or not) in the use of the controlled thermonuclear synthesis power generation, even though the latter may be achievable earlier technologically than the former! We may need to stand the temptation of virtually free power generation for the sake of self-preservation!

  28. #28 Saul Simhon
    January 3, 2016

    Dear Ethan,

    About the Forbes article (, you mentioned something about special relativity; that a long journey would actually take the traveler less time (20-30 years) because they are traveling close to the speed of light and their time slows down. I am not sure I understand this, does not sound right to me.

    From the earths perspective, it is true that the time will slow down on the ship. But from within the ship’s perspective, time does not slow dows. It does not appear any different. Actually, from the ship’s perspective, time appears to slow down for earth instead. The twin paradox is resolved only when the ship returns and the two me up again to corroborate the information; the ship firing the rockets the other way breaks the symmetry and decides who is actually older when they meet again (since the retuning ships now travels faster wrt the original inertial reference frame to ‘catchup’ to earth that had appeared to be traveling away from the ship prior to the return trip). But as for the travelers themselves, it’s still the same distance covered and the same velocity travelled. How can it take only 20-40 years (that would imply traveling faster than light wrt the ship’s reference frame). Space contraction will not help here, So for the traveler, it would still take the generations to reach the star. Would it not?

  29. #29 Tim Gallimore
    United States
    January 23, 2016

    My opinion, size is infinite. God’s sneeze is our multi-universe. Our sneeze is a multi-universe, and so on. Unprovable but it’s my theory.

  30. #30 Wow
    January 25, 2016

    But what does your opinion have to it other than a complete ass-pull of assertions?

  31. #31 Tim Gallimore
    January 25, 2016

    Sorry, Wow, should have been more specific : Planck era is the earliest period of time in the history of the universe, from zero to approximately 10−43 seconds (Planck time). While there is no proven theory that correctly describes the universe at this period, it is postulated that quantum effects of gravity dominated physical interactions due to the small scale of the universe. During this period, approximately 13.79 billion years ago, gravitation is believed to have been as strong as the other fundamental forces, and all the forces may have been unified. Inconceivably hot and dense, the state of the universe during the Planck epoch was unstable. As it expanded and cooled, the familiar manifestations of the fundamental forces arose through a process known as symmetry breaking.
    Modern cosmology now suggests that the Planck epoch may have inaugurated a period of unification, known as the grand unification epoch, and that symmetry breaking then quickly led to the era of cosmic inflation, the Inflationary epoch, during In the context of time, an order of magnitude is a description of the quantity of a time in respect to comparison between differing magnitudes. In common usage, the scale is usually the base10 or base−10 exponent being applied to an amount, making the order of magnitude 10 times greater or smaller.[1] As the differences are measured in factors of 10, a logarithmic scale is applied. In terms of time, the relationship between the smallest limit of time, the Planck time, and the next order of magnitude larger is 10. which the universe greatly expanded in scale over a very short period of time.[1]

  32. #32 Wow
    January 25, 2016

    “should have been more specific ”

    The following claims you made are completely different from the claim you’d made earlier.

    Did you find more to pull out of your arse?

  33. #33 Ragtag Media
    January 25, 2016

    “The following claims you made are completely different from the claim you’d made earlier.”

    Which is WHY Tim prefaced the next post apologetically: “SORRY, Wow, should have been more specific”


    You then proceed to insult a visitor/patron to Ethans blog:
    “Did you find more to pull out of your arse?”

    Thus proving you are an assclown. Or perhaps I should say arseclown.

  34. #34 Wow
    January 26, 2016

    “Which is WHY Tim prefaced the next post apologetically”

    Which wasn’t clarifying the previous post AT ALL, and was another complete load of vomited ass-gravy unconnected with a working human brain.

    Therefore was not a valid statement.

  35. #35 Dmitry
    June 7, 2016

    Dear Ethan,
    I have a question about holographic principle. It says that all information that could contain in some volume of space is equivalent to the information that contain in sphere surrounding that space. Maximum information contains in black holes and sphere area of black holes is proportional to their mass^2. So we could take many tiny black holes and place them into some volume of space. Theoretically, in space with radius equal 10, volume equal 4186 and area of surrounding it sphere – 1256 we could place about 1000 black holes with radius equal 1. Total area (and information that contains in them) of this black holes is about 12560 (ten times more than area of sphere contained these black holes). I understand that after millisecond all these tiny black holes will merge into one big black hole, but for a small time we destroy the holographic principle, isn’t it?

  36. #36 Yuri
    June 20, 2016

    Dear Ethan,
    I wonder, if photon happens to be on the black hole’s event horizon, and the hole is vaporizing, with its radius reducing, is it possible that at some moment the photon will be located outside of the event horizon and consequentally escape the black hole?

    P.S. I don’t know if someone already mentioned, but your officially-Ethan-approved-way-to-contact form does not work 😉

  37. #37 Wow
    June 20, 2016

    “Scientists often state that they do not know what time is, but know how to measure it accurately, which is an oxymora.”

    Nope, not at all.

    You don’t know how children are born, but you can procreate.

    Though I’m assuming here…

  38. #38 Carl
    June 20, 2016

    Dear Ethan,

    I’ve read recent stories about asteroids that share the Earth’s orbit (2016 HO3, 2003 YN107). Does that mean Earth is a dwarf planet?

    If so, for the sake of Earth’s status as a real planet, do you support an urgent global effort to remove these from our orbit? I know I do.

  39. #39 Vadim Efimov
    Saint-Petersburg, Russia
    June 21, 2016

    Dear Ethan,

    The speed of the universe’s expansion is less then the speed of light. What happens to a photon, emitted towards the boundaries of the universe?

    Thank you!
    Vadim Efimov

  40. #40 Michael Kelsey
    SLAC National Accelerator Laboratory
    June 21, 2016

    @Vadim Efimov #39: The expansion speed depends on how far away you are from whatever you’re observing: the _rate_ is expressed as “speed per unit distance” (73 km/s per megaparsec). If the total distance is large enough, the observed rate of expansion (separation between observer and observed) can exceed the speed of light.

    What happens to an emitted photon is that it gets stretched out (redshifted) according to that expansion.

    The easiest way to do the calculation is to use the speed part of the rate and integrate it until the separation distance has increased from whatever you started at (say, one megaparsec) to some larger value (say, two megaparsecs), the ratio between the two tells you exactly the ratio by which a photon will have had its wavelength stretched during that same time period.

  41. #41 Michael Kelsey
    SLAC National Accelerator Laboratory
    June 29, 2016

    I wonder if you might be willing to do a narrowly-focussed astrophysics “explaining” post, rather than your usual wide-ranging, fate-of-the-universe (and YEC-baiting 🙂 ) pieces. I ran across two competing preprints in the astro-ph arXiv: and

    I think I understand what the various authors mean by a “supernova impostor,” but it would be really cool to get a slightly non-technical explanation of Luminous Blue Variables (surely that’s *someone’s* band name?!?) vs. Wolf-Rayet stars, and maybe some perspective on the really cool timescale these papers talk about — apparently significant stellar evolution over the course of just years or decades.

  42. #42 Michael Kelsey
    SLAC National Accelerator Laboratory
    June 29, 2016

    Ethan, you may not know this, but the “I have a question” Web form at the top of this post no longer works. The form submits to “” (predating your move to Science Blogs?), and then generates an error page “Sorry I can’t send to Is on this server?”

  43. #43 Pavel Kraynyukhov
    Almaty, Kazakhstan
    June 30, 2016

    Dear Ethan,

    Would it be possible to investigate following assumptions:
    1. The space-time has a mass itself
    2. The dark matter we are looking for, is not the matter but the space-time itself

    Do we have any possibilities/tools/frameworks to investigate those assumptions ? Assuming that they have a sense in a first place.

    My question is emerged from problems with understanding of virtual particles those are born and annihilate (for the most part) in vacuum. How oft are they born ? How fast are they annihilate ? Are they represent a significant mass in specific volume of the universe in their lifetime ?
    Is there specific amount of energy we can associate to a virtual particles for their life-time ? I understand that sum of the energies of emerging and annihilating is equal to 0, but what about a time slice when those particles already born and not yet annihilated ?

    I hope my question is not stupid enough to be ignored.
    With best regards,

  44. #44 Aleksander K.
    June 30, 2016

    What is the Universe in a range below the very low frequency?

  45. #45 Wow
    July 1, 2016

    It’s a third of the way to misty mountains, Alek.

  46. #46 Wow
    July 1, 2016

    “I’ve read recent stories about asteroids that share the Earth’s orbit (2016 HO3, 2003 YN107). Does that mean Earth is a dwarf planet?”


    Check the definition, dearie.

  47. #47 Dmitry
    Moscow, Russia
    July 1, 2016

    How to take into account the asteroid belt between Mars and Jupiter , Pluto ‘s orbit after the analysis of the microwave radiation and the red shift ?

  48. #48 Konstantin
    July 6, 2016

    In The Big Bang theory young universe expanded very quickly (cosmic inflation).
    After some time inflation stopped.
    Did speed changed because of the dark energy?
    I mean that in young universe there was much dark energy and the universe inflated.
    At some time almost all dark energy (suddenly) disappeared and inflation stopped.

  49. #49 Michael
    Moscow, Russia
    July 17, 2016

    Hello, Ethan!
    What will happens, when the observer’s event horizon, formed by space expansion rate, will be less, than a Planck distance?
    Thank you!

  50. #50 Rick Maedler
    July 18, 2016

    Strangely, in the video, “Illustris Simulation: Most detailed simulation of our Universe,” (nice music by the way), it says nothing about how many billions of years ago the sound track started.

  51. #51 Wow
    July 19, 2016

    re: #49, the big rip.

    But there may be no definition of time well before then. If a single lepton, presuming it is actually of zero extent and not a compound object, would be unable to determine velocity, time or distance.

  52. #52 Wow
    July 19, 2016

    “In The Big Bang theory young universe expanded very quickly (cosmic inflation).
    After some time inflation stopped.
    Did speed changed because of the dark energy?”

    Dark Energy, whatever it is, is a separate thing from the inflation field’s associated energy.

  53. #53 Jerri
    July 19, 2016

    Hubble’s Law states that the speeds of recession of galaxies are proportional to their distance apart. How then can we use this law to calculate the age of the universe because when galaxies were close then speeds of recession would have to be zero?

  54. #54 Wow
    July 21, 2016

    Yeah. Look up “Acceleration”, Jerri.

  55. #55 Jerri
    July 22, 2016

    Thanks WOW. But I now think the depth of the answer I want will be in these lectures on Cosmology by Leonard Susskind on youTube.

  56. #56 Artyom Ivankov
    August 14, 2016

    Hello, Ethan!
    My question is about gravity.
    As far I know, gravity have wave’s properties and not so far scientists found gravity emitting.
    What you think, whether the gravity have next properties as
    interference, polarization etc?.. Can we create “gravity laser”, for example, or can see gravitational interference?.
    Thank you.

  57. #57 Nick
    August 15, 2016

    As we know, almost each particle has some size and mass. So if all particles came from Big Bang, they all were concentrated at one point. What was the size of that point and what was the mass? Was the mass the same as current Universe’s mass?

  58. #58 Evgeniy An
    Tashkent, Uzbekistan
    August 17, 2016

    Why Black Holes can’t catch their own gravity field ?

  59. #59 Evgeniy An
    Tashkent, Uzbekistan
    August 17, 2016

    Why Black Holes can’t catch their own gravitational field ?
    Why scientist say that Universe expands acceleratingly ?
    Far away stars has more redshift than the nearest ones.
    But we see far away stars more yanger than nearest ones..
    So yanger the stars more redshift we get and expanding was more in the earliar times than now and slowering but not accelerating.

  60. #60 Wow
    August 18, 2016

    Why would they “catch” their own gravitational field? For that to happen, if we take the particle model of gravity, would require that some mass produce a graviton then produce another one to pull it back.

    Because the rate of expansion is seen to accelerate, much like “that dragracer is accelerating” can be detected.

    Far away stars have more space between to show expansion on.

    Since light travels through space, what do you mean by “more yanger [sic]”?

    We don’t see yanger stars (younger I take it) and there’s no method by which a younger star would be redshifted.

  61. #61 Patrick McCormick
    Sarasota, FL
    August 27, 2016

    Why do scientists look at life as an accidental occurrence? Has anyone attempted to prove that Life is generated by a primal force, like the other basic forces; gravity, electromagnetism, strong force or weak force?

    ** Life seems to have a basic “Toolbox”.

    ** Life provides our physical reality with an observer and observation seems to change the behavior of matter.

    What if Life is the reason this reality exists and all the other “Forces” support its development?

  62. #62 Frank
    September 8, 2016

    Today there are arguments, whether time exists, is the Block Universe idea is correct or not. I thought of an experiment which may help for answers and it maybe possible to do in the near future. Imagine 2 super fast cameras side by side taking the picture of the same event. And in that moment one camera is standing still but the other is momentarily traveling at extreme speed. The event they taking picture of could be a screen bombarded by a bunch of electrons and each time an electron hits it creates a glowing spot. I think Relativity says the images should be different and Block Universe is correct. And if the images are the same that would mean only “now” exists, there is no time.

  63. #63 Gennadiy
    KHMAO Nizhnevartovsk
    September 21, 2016

    Hello, Ethan!
    My question is about light.
    What happens with the light at the boundary of the universe’s expansion.He absorbed or reflected?

  64. #64 Ruslan
    September 21, 2016

    Dear Ethan,
    If we had a hole in the center of the moon that we would throw a cent , what speed would develop cent in the center of the moon view of the acceleration value is not constant due to the proximity to the center of the moon . How to measure the acceleration of the acceleration ?

  65. #65 Frank
    Omaha, NE
    September 25, 2016

    I think it is possible to change refraction index of air using (IR/UV?) laser or ultrasound. If so wouldn’t it be possible to use a powerful laser scanner or phased array of ultrasonic emitters to create a giant “virtual” lens on top of an astronomical telescope to increase magnification?

  66. #66 Frank
    September 25, 2016

    I don’t think I ever seen any picture that is an accurate representation of how space around looks to naked eye of astronauts. Is there such a picture anywhere?

  67. #67 Frank
    September 25, 2016

    And wouldn’t it be great if NASA created a naked eye view of all space around Earth as a 360 degree hi-res image?

  68. #68 Brian Regan
    October 2, 2016

    Ethan, I have read your post about why CDM is a much better explanation for dark matter than MOND, and it seems pretty good to me, a layman. However, until the GAIA telescope is in operation, it will be difficult to be sure. What I am curious about is why CDM and MOND should be mutually exclusive. Is it not possible that CDM is strewn widely across the cosmic void, and then falls preferentially into, and aggregates in, areas of “deep” GR curvature, thereby resulting in galaxies? Thank you for considering my question.

  69. #69 Vicky
    November 4, 2016

    Hi Ethan,
    I read your blog regularly and its perhaps the best science/physics blog on the internet – so thank you for sharing your thoughts through this blog!!
    I have a question on black holes – can BH’s have a magnetic field or charge that is due to the matter inside the BH (rather than an accretion disk) and if yes, how is it able to manifest itself outside the BH when nothing can escape it? I have read that there is an alternate proposal to how BH’s are formed – MECO’s (magnetic eternally collapsing objects). Is there a way to test whether this description of BH’s is correct?

  70. #70 Q W Rowe
    New Zealand
    December 11, 2016

    Ethan, I was just reading some of your older articles, and this one got me wondering:

    Is there a quantitative difference in the properties of the inflationary era space-time and that of our future universe scenario’s where the accelerating expansion continues until every particle is causally disconnected, such as in the ‘big-rip’ scenario, or in certain regions of the ‘constant dark energy’ scenario?

    At some point, I imagine, there would be no reference for the space-time to know it is expanding, so I was also wondering how a quantum fluctuation would behave in such an environment?

  71. #71 Wardell J Lindsay
    United States
    December 11, 2016

    There is no difference in the present space and the future space.

    The Universe is not expanding! The Universe is stationary. Current Theory, Big Bang and Inflation and General Relativity are obsolete. The Universe is a Quaternion Space, ala William Hamilton. one real dimension and three vector dimensions. Einstein’s Space Time is 2 reals and one vector ict.

    The real Law of Gravity is
    W=[c,V][,P]=[-v.p,cP]=[-mGM/r, cP]

    The Gravitational Energy W is a Quaternion, the real energy is -mGM/r and the vector energy cP=cmV is the so-called “Dark Energy”.

    The University is Stationary at v=c.
    0=XW=[d/dr,Del][-vp,cP]=[vp/r -cDel.P, cdP/dr – Del vp]

    Hubbles Constant H=c/R=c/cT=1/T , T=Age.

    Using H=62km/s/Mpc= c/R gives R=150GPm and T= 500MGs = 15.844 Gyears.

    The Mass of the Universe is 2.025E53 kg..

    The Density is 60E-27kg/m^3

    There is no Dark Matter, the over rotation in Galaxies is due to electromagnetism, homopolar motor, like wattmeter in homes..

    Dark Energy, the vector energy cP, is the driver of the over rotation, Suns are charged positive; gravity rotation causes the charged suns to create a current. The current creates a magnetic B field perpendicular to the plane. Electrons from inter-space flows into the galaxy and crates a vectro force on the suns.. F=CxP/r =eVxB.
    p=eBt=euI thus mV=euI and
    V=(r/m)uI=176G.1.25u I=220kmI/s thus V=220km/s with i=1 Amp. 250 suns will create 1Amp at 220km/s @8.5kpc.

    Dark Energy is cP and clarifies Physics.
    The Law of Force is
    F= XW=[d/dr,Del][-vp,cP]
    F =[vp/r + cDel.P, cdP/dr – Del vp + cDelxP]

    This force includes point masses, solar systems, galaxies and Clusters and Super clusters.

  72. #72 Sergii K
    December 12, 2016

    Please find my question, I hope it really interesting!

    If we have a hypothetical material that is very durable, in the cube with the size of 10x10x10 meters. To move it, we need to spent X energy.
    But if we form it to the ultra-thin stick, a few light-seconds in length, and will try to move – what happens?
    If we move the stick, its other end will move immediately, or through those few seconds, distorting space?
    Or to increase the amount of energy to be applied?
    Or such a hypothetical material is impossible?
    Or ?

  73. #73 Wow
    December 12, 2016

    There is no difference in the present space and the future space.

    The Universe is not expanding! The Universe is stationary.

    That’s the sort of complete bollocks that is why Trump really isn’t a problem. Compared to many americans living there, trump’s just a normal crackpot, like Wendull here.

  74. #74 Wow
    December 12, 2016


    It will move delayed, because the force, no matter how dense and solid the material, cannot be felt faster than the speed of light.

    But why is that odd to think about? What was obscure that you were surprised at it?

  75. #75 Evgeniy An
    December 12, 2016

    #60. WOW. August 18. 2016.

    … Since light travels through space, what do you mean by “more yanger [sic]”?

    Sorry my English, but my question quite claear – “yanger – younger – more earlier to the past. According to your own Big-Bang theory more distant objects are more earlier to the past .And they have bigger red-shift by Hubble’s law than nearest ones. So the direction of acseleration of expanding is to the past and we have deselerating of expanding to the present.

  76. #76 Wardell J Lindsay
    United States
    December 12, 2016

    Vicky, Black Holes, BH, have a magnetic field. The field is the result of charged masses revolving around the BH. The BH is nothing but the center of the revolving masses.
    The magnetic filed B= uI/r, where the current
    I =sum of charged masses x Velocity/2pi r.. The larger the charges the larger the magnetic field, B. The magnetic field can be intense and electromagnetic jets shoot out of the BH and breakdown matter around the BH.

    Magnetic fields are the result of gravitational rotation of charged masses. Most suns are positively charged masses. Moving charges make magnetic fields, B=uI/r.

    Black Holes are no more or no less than this.

  77. #77 Wow
    December 13, 2016

    ” So the direction of acseleration of expanding is to the past and we have deselerating of expanding to the present.”

    BTW, yes, I did consider it was younger and took it as such, hence I used the word correctly spelt. But it shows an endemic problem that you need to address, and your only option is to go to some native speaker and ask them, because this is yet another claim that is either gibberish because you are unable to communicate fluently in English or gibberish because the idea you have is complete gibberish.

    And the only thing I can go in is the words.

    There is no direction to acceleration in time. There’s past acceleration and future acceleration and you can have the time derivative of acceleration, but the claim you made is nonsensical.

    But to the second part, you are wrong: acceleration is increasing, all information we have now is that it SHOULD be slowing down its acceleration, but it is increasing. And so we posit “dark energy” to fit the evidence, rather than fit evidence to our theories.

    So two things:
    1) Look up dark energy
    2) Discuss first with a speaker of your native tongue. They DO exist on the internet, you’ll have to put your language or country in the search bar, because by default it will use English speaking sites.

  78. #78 Evgeniy An
    December 13, 2016

    #77. Thank you for adressing me to my native language sector of internet. So I haven’t any need to read you foolish comments. Notice , my question was addressed to Eathan, not for you. Or is that you , mr. Eathan ? And I don’t know how you comment appeares in August 18. This time there wasn’t. It appeares rescently.
    You are the only one , who didn’t understand my post.
    You have not you own arguments redirectiring to the other sites.
    And instead the discussing the problem , you speak about my spelling. You are usual trickiman.
    …No direction of the time ?!
    This describes you full.. Sorry. Good by !
    P.S. этот журнал читают не только те , чей родной язык английский. А также и люди из других стран.
    И им наплевать на правильное произношение.
    This journal read people of many foreghn countries, their native language is not english and they don not care of it.
    I wrote my article for open minded people, not for you.

  79. #79 Wow
    December 14, 2016

    “#77. Thank you for adressing me to my native language sector of internet. So I haven’t any need to read you foolish comments”

    Just like we have no need to care whether you get answered or not. We DEFINITELY don’t need to both interpret your language into something coherent AND work out how to mangle our own language so you;ll comprehend the answer.

    If you don’t want to try, don’t.

    But we don’t have to try either.

    Enjoy your deliberately cultivated ignorance because to do otherwise would be too hard.

  80. #80 Frank
    December 18, 2016

    Big question: Inflation and Dark Energy could be the same thing?

  81. #81 Frank
    December 18, 2016

    Big question: If Dark Energy causing Universe to expand, isn’t it getting spent? (How total amount of Dark Energy changed since the Big Bang? Stayed same/increased/decreased?)

  82. #82 Michael Shain
    January 14, 2017

    Not rally a GR question, but you said the graviton, should it exist, will have zero mass and spin two. How can something of zero mass have a spin?

  83. #83 Michael Kelsey
    SLAC National Accelerator Laboratory
    January 15, 2017

    @Michael Shain #82: “Spin” in this context is not like a top spinning around on its tip. It is a quantum mechanical property, a form of intrinsic angular momentum which doesn’t require the entity to have mass (or radius, for that matter).

    Spin only appears in multiples of h-bar/2 (Planck’s constant divided by 4pi). We physicists don’t like carrying around the same constant in all of our expressions, so we drop the h-bar and talk about “spin-1/2”, “spin-1”, “spin-2”, “spin-5/2”, etc.