Submit your physics questions, win cool prizes


160 Responses to “Submit your physics questions, win cool prizes”

  1. Nick Reynolds says:

    Is the future of renewable energy in genetics?  Energy is a potential that exists within all things right?  Why not develop a battery that acts like a fat cell?
    –Nick Reynolds
    –Durang0, Co.

  2. Tom says:

    Fucking magnets. How do they work?


  3. The equatorial speed of the earth is approximately 1000 mph.  The speed of rotation at the pole is 0 mph.  General relativity tells us that this difference in relative speed should cause someone (or something) at the equator to age slower than at the pole.   Over time, this would suggest that the age of the earth’s surface differs based on distance from the equator, and that this spin causes swirling and twisting of space time itself.  Is this the case?  Are the poles older than the equator?
    -San Francisco

    • jon_anon says:

      to John Olmstead – the surface of the earth is moving around (fucking tectonic plates), so there is no part of the surface that has always been at a pole, or always been at the equator. Presumably this averages out the differences in age, which in any case would be very very tiny since the Earth is not rotating at relativistic velocities.

    • Ross Mayo says:

      Yes. The poles are older than the equator. But the speeds the earth moves at are so incredibly slow compared to ‘relativistic’ speeds the difference is tiny, even for the whole time the earth has been around.

  4. ericM says:

    Speaking of ‘Fabric’: There’s a lot of common reference in astrophysics and popular culture to something called “Space-Time Fabric.” With the ongoing speculation about extra hidden dimensions and other components (dark matter / energy), do you [the panel] feel, like me, that the term is somehow “Two-Dimensionally” misleading and outmoded, and would any of you have a more appropriate or newer term to suggest? Thanks for thinking! (I’m local in NYC)

  5. litrs says:

    If I go in a locked room without any air. If I fart, can I breath it? Or the room stays without air.


  6. Jim Saul says:

    That sounds like a great event… Greene’s books are very accessible, but Leonard Susskind is one of my all-time favorite lecturers, up there with Feynman for making being a towering genius seem like a hell of a lot of fun.

    As for a question, why do our models assume that the ratios and relationships between the 4 fundamental forces are static through time (after the first seconds)?  

    And speaking of the first few seconds, is inflation undermined at all by recent discoveries (dark matter, dark energy, and accelerating expansion)?

    (edit – I’m not near NY. Covington, KY. Just interested in the questions.)

  7. Ardreeves says:

    Bell’s hypothesis and the subsequent experiments showed that information can be processed faster than light (or in other words there are no local hidden variables). I have always been intrigued by this and would love a better explanation of how this theory and the experiments worked in laymen’s terms. Can this be described without going too in-depth into calculus/linear algebra?

    I live in Boston…

  8. Anthony Valcic says:

    What explanations for dark matter have been ruled out and why? For example, we know that according to the uncertainty principle, virtual particle – antiparticle pairs briefly come into existence, and I assume that would add up to a great deal of mass at any given moment on a universal scale. Does it? and how much? Is it dark matter?

    What about dark matter existing in some or all of the extra dimensions that have been proposed by various theories? How would we rule that in or out?

    (not in New York area)

  9. Rich Keller says:

    Okay, so, the universe is expanding. But if the universe is everything, then, what is it expanding into?

    I live in Wisconsin.

  10. Marc Anthony Guzman says:

    Dr. Greene im currently enjoying your book “the elegant universe” but speaking with a friend lastnight (10-31) i thought up a pretty logical assumption that im sure has been thought of before anyhow, my question is: that based on the supposition(s) that the universe is spherical and indeed is still expanding would it be safe to assume that if/when this bubble we call the universe does indeed pop, much the way a soap bubble pops, that it may “peel” back to a pretty exact but non-uniform point (envision a soap bubble or balloon popping in extra-slow motion) where all matter, mass and energy would all collect and meet at that exact, non-uniform point and if it does indeed meet at that point, colliding violently could it give birth to a new separate universe, adding yet another facet to the “multiverse”?

  11. roromano says:

    — If the Universe expands, where?
    I’m in NYC.

  12. Ben Chatterton says:

    In your opinion, is the No-communication Theorem in quantum mechanics correct? Or will we eventually be able to communicate faster than light using quantum entanglement?

    Ben Chatterton
    Phoenix, AZ

  13. Angry Chief says:

    It is often said that the universe is constantly expanding at an ever increasing rate. When I hear that I can picture the galaxies, the open space and the motion of pushing outward but I cannot wrap my head around what physical thing the universe is pushing out into. Some would say the fabric of space time but that really doesn’t cut it. What is beyond the edge of the Universe? And what does it look like?

    -Jesse Cranford aka Angry Chief
    -Denton, TX

  14. Tyler Strause says:

    What is the explanation of the Pioneer anomaly?

  15. Jesse Tokarz says:

    Are Many Worlds / Multiverse -type theories compatible with the idea that there are many more dimensions than the standard four of time-space? If multiple universes exist, in what way do they exist?

    Also, what’s the latest thought on what dark matter is? Can dark matter be absorbed into a black hole?

    (Not in the NYC area, but just interested in stuff like this. Sounds very cool.)

  16. Tom Dzolan says:

    What exactly is “dark energy” and will we ever be able to harness it?
    (From the NYC area)

  17. dexter121uk says:

    I do not live in NYC…

    I’ve wondered this before but i think its more theoretical and sounds kind of daft when saying it:

    if you were at the edge of our solar system, and could make a really big pole made of some very dense material that was as long as to Alpha Centauri and had the energy to poke one end of the metal pole, would the other end move at the same time?. I dont think it would, but am not sure what forces would come into play.


  18. Is a mega structure like a Dyson sphere a realistic outcome of energy needs? Or will it remain purely in the realm of science fiction. 

    -New York City

  19. david bailey says:

    where did all the anti-matter go?

  20. mlm8513s says:

    Does the universe exapand with equal force in all directions. And what role does gravity play in the slowing or speeding up of the expansion. Will it increase in its speed of expansion given that less and less gravity will be acting upon it with greater expanse of empty space. With the expansion creating less of anything throughout that space can the speed of light fluctuate.

  21. mennonot says:

    I’m endlessly fascinated by the concept of the multiverse, but is there any possible way that discoveries or technology related to the multiverse could impact me in my lifetime (I’m 30 years old)?

    I do not live in the New York area.

  22. John Smolik says:

    If our sun were to suddenly disappear, the light would continue to shine upon the earth for about 9 more minutes because we’re 9 light minutes away from the sun.  The lack of mass on the other hand would be apparent immediately, and the moment the sun disappeared Earth would be “free” of the sun’s gravitational pull and just continue in a straight line out into the depths of space. 

    Does gravity (or the effects thereof) travel faster than light?  
    In what ways can this principle be applied to time travel, even if it’s just information making the trip? 
    If I could make a sizable quantity of matter “pop” in and out of existence around Proxima Centauri, could I Morse-code Earth with those pops and transmit a message faster than the 4.3 light-years it would take light to reach the same place?

    John , Austin TX

  23. Ed Smiley says:

    In 4+ dimensional theories, such as those seen in String Theory and M Theory, the extra dimensions are compactified, leaving 4 dimensions, 3 of space and one of time, at a macroscale.

    My question is this:

    Why are only the “traditional” spacetime dimensions the only ones to be subjected to the expansion of the universe, where the “hidden” (compactified) dimensions retain their microscale? Is there any mathematical model that achieves this feature naturally?  Or is the assignment of compatification entirely ad hoc?

    I do not live in New York City.


  24. beforewepost says:

    I’ve frequently heard gravity explained as “objects move along space-time. Space-time is warped by matter so objects are deflected by matter.” Rubber tarps with stars and planets dimpling the tarp is a popular visual aide to explain the idea.

    What I have never seen is an explanation as to why matter warps space time. How does space-time know matter is there to warp it?

    Near NYC.

  25. Kevin Harrelson says:

    I do NOT live anywhere near NY, so I cannot attend.  However, I have always wondered the answer to this question…

    Assume, for now, that the universe is steady-state (which it isn’t).  We know that stars crank out massive amounts of neutrinos, which rarely interact with matter.  At some point, the neutrino density will increase such that the neutrinos are destroyed (interactions with matter) at the same rate that they are created (call this “neutrino equilibrium”).  What would the universe look like if this happened?  Would these constant reactions with ordinary matter be enough to split apart DNA and make life impossible?

    Now, given that the universe is NOT steady-state, could this still happen?

  26. jon_anon says:

    So “dark energy” is said to be the thing that is causing the expansion of the universe to accelerate. But we don’t know what “dark energy” is. My question is: how is calling the unknown cause of the acceleration “dark energy” any different or any better than just saying we don’t know what is causing the apparent acceleration of the expansion of the universe? (I don’t live in NYC)

    • Ross Mayo says:

      It’s 2 words (dark energy) vs eight words(we don’t know where this energy came from)?

      It’s because it sounds a hellova lot cooler on a grant application.

  27. GP says:

    Okay, so I am probably misunderstanding something in coming up with this question but here we go anyway. 

    The way the Discovery Channel explains it, in quantum physics, a particle can occupy more than one place at the same time (at last, you can not accurately measure a particle’s time and place in one go) Supposing I didn’t misunderstand this idea, how can we be sure that the universe contains more than one particle? Why isn’t every particle the same one, manifesting itself time and time (and place and place) again? Oh, and I am not from New York City.

    • dlbancroft says:

      Some scientists think this might actually be the case, with electrons at least!

  28. jon_anon says:

    So there are models of the universe (string theory models) that work well in 10 or 11 dimensions, but since we only see 3 around us plus one time dimension, we assume the others are each rolled up at a very tiny scale. My question is: the 6 or 7 dimensions that are assumed to be too tiny for us to experience, are they thought to be spatial-dimension-like, or could they be other time-dimensions, or could there even be other kinds of dimension we haven’t thought of because they’re too tiny to experience? (In other words, add to the question of why are there only 3 spatial dimensions, the question: “why are there only two kinds of dimensions (space and time)”).  (I still don’t live in NYC)

  29. k_v says:

    What is the significance of carbon chain formation in moderate-density interstellar clouds? 

    I do not live in NY, and I ask because a friend used to be in ISM and his answers were always too vague. 

  30. Ted Garbeff says:

    How does light “know” which path to take?

  31. lorq says:

    (I don’t live in NYC; I live in Buffalo.)

    The recent announcement from Italy of evidence for neutrinos traveling faster than the speed of light, and the firestorm of commentary, controversy, and speculation that followed it, centered on a key postulate of Einstein’s Special Theory of Relativity: that the velocity of light was a constant in all frames of reference, and could not be exceeded.  This postulate has been borne out repeatedly by experiment, which is why the announcement from Italy came as such a shock.

    I have always been puzzled by the “invariance of light-speed” postulate.  Since the Special Theory was formulated in part to address the empirical evidence for the invariance of the speed of light, isn’t the postulate in some sense “assuming what we’re trying to explain”?  

    Another way of formulating the question would be: what is the *scientific status* of the postulate of the invariance of light?  Does the postulate fit into the Special and General Theories in a way that *provides* a scientific explanation (just in a way I haven’t understood yet), or is it a postulate that *implies* or *invites* a scientific explanation (just one that hasn’t been discovered yet)?

    More simply: is the invariance of the velocity of light a scientific mystery, or a scientifically explained phenomenon?

  32. Benjamin Loeffler says:

    In an interview with Robert Krulwich, you once discussed the (un)compatibility of physics and freewill.  Can you elaborate on this and explain if this results in a form of predetermination?

  33. Jim Saul says:

    If you create a Bose-Einstein condensate, could a neutrino (or anything else) pass through it without collapsing it back into solid matter?

    • Ross Mayo says:

      Yes. A B-E condensate is sort of like taking the tight waveform of one piece of matter and making that wave synchronize across many atoms. If you shot a neutrino through it, it would do nothing, since the neutrino has no charge and wouldn’t warp the condensate at all.

      • Jim Saul says:

        Since the neutrino is affected by weak nuclear force, and probably has a non-zero mass wouldn’t there be an interaction?  Or are you sure that electromagnetism the only force that a Bose-Einstein Condensate interacts with?

  34. Ambiguity says:

    I’ve read conflicting things by competent cosmologists on the concept of the “multiverse.”
    While such discussions are inherently speculative at this point, some cosmologists believe that we’re coming close to the point where rival speculations may have testable implications, allowing us to start doing some real science in the domain. Other cosmologists feel that any talk of multiverses will of necessity fall outside the realm of science for the foreseeable future, if not longer.
    What’s your take on it? Are we approaching a time where we can start to distinguish between the various proposed models of the multiverse?
    (Not too far from NY, but probably too far to participate in the ticket draw.)

  35. If the rate of spacial expansion (as expansion of the universe)  were somehow “tied” to gravity, so we were sort of “falling down our own local well” – so that the universe appeared to expand at a “universal rate” from the observer’s standpoint – how would you create an experiment to determine non-uniform expansion. 

  36. Luke Nieman says:

    If basic principles of string theory is true, that all matter is linked via quantum strings, then could it be true that so called “soul-mates” could be scientifically proven because the two people are vibrating at the same quantum wavelength?

  37. Kathryn Loeffler says:

    my first thought is: in your opinion, how accurate is the physics presented in a wrinkle in time? should we be able to tesseract?
    second: No seriously, you don’t believe in free will? Really? is infiniteness and lack of free will the same as predestination?

    third: I live in NYC

    fourth: re:4th dimensions, blind people have reported the ability visualize more than 3 spatial dimensions, isn’t it arrogant to assume that because we can’t experience them they are compacted and too small to experience and/or non-spatial dimensions? What if they are just beyond our limited abilities to perceive?

  38. Is it possible the dark matter is just “off to the left” and that’s why we can’t see it?  Simplifying the universe to flatland, gravity of objects on a 2d plan would be in nice circles and ellipses… but if a mass somewhere on the Z-axis came along – but never intercepted the 2D plane, flatlander would be able to sense its presence similar to how we sense dark matter.  But most of the explanations I see don’t seem to every take this thought into account.  Is it possible the exceeding the speed limit C might end up pushing some matter into this “other axis” – say like hawking radiation or similar?

  39. HorsePunchKid says:

    This might be one of those questions that is not actually valid and just indicates my lack of understanding, but I’ve been wondering: What is the total mass/energy of the cosmic microwave background? My understanding is that there was some total amount of (light) radiation left bouncing around after recombination (when the universe became “transparent” to light), so that radiation presumably has some total energy that we can estimate. On that topic, I know the temperature varies, but is that the same as the “density” of photons varying? I picture that the density would vary just as you see caustics at the bottom of a swimming pool, but I gather the temperature we see (e.g. in the WMAP CMB map) is a measure of the wavelength of the microwave light, rather than the number of photons being detected. (I am in NYC and would love to attend!)

  40. SkylerNelson says:

    Many of the questions in this thread could be answered by most working physicists, or even working non-physicists (such as myself, if I had any free time) so  “Ask a physicist” would be a pretty interesting BB feature.

    Anyway, I’ll bite, from California.
    I’d like to hear Leonard Susskind talk about how the concept of information is used by physicists.  The mathematical formulation of information seems strongly model dependent, not very localizable and dependent on a priori probability distributions.  So I don’t understand why some physicists (I’m thinking of Wheeler, most specifically) want to treat it as a fundamental quantity.  In particular, some tout the holographic principle as providing a bound on the amount of information in a finite volume.  How’s this supposed to work?  And how does information loss imply heat generation in black hole scenarios?  I understand entropy and heat are linked and information and entropy are supposed to be connected (we measure them similarly) so you’re not supposed to be able to lose information without generating entropy.  But I don’t understand how the Hawking-like scenarios of black holes eating information is physically supposed to generate heat.  I know it would result in an increase in entropy because it’s irreversible, but I don’t see where the heat comes from.

    • Jim Saul says:

      Awesome suggestion.  I’d be happy to hear anyone answer my questions, though Perlmutter must have thought about the inflation one, given that it’s his work that even makes it possible to ask it!

  41. I don’t live in the NYC area.

  42. Bill Shipman says:

    Could it be that the macro-scale of the universe and the micro scale of subatomic particles are the same, merely a difference in perspective?  Visually in the vein of Men in Black scene scene looking out of a locker but more to the point of the breakdown in standard theory between QM and general relativity.  Black holes condense matter down to a single point could this all be a physical manifestation of a Klein Bottle /Mobius Strip.

    Excellent questions, I’d like to hear more on the question re: Quantum Entanglement and super-luminal communications and the question about the identity of particles given the contraints of the uncertainty principle.

    I don’t live in NYC much to my chagrin today, I’m a proud son of The Old North State!

  43. lorq says:

    Whoops, forgot: I don’t live in NYC.  (I live in Buffalo.)

  44. eFarther says:

    What if Albert Einstein’s theories (or pick your favorite physics theorist) were theoretically correct and provable as he expected, but 180 degrees out of line with reality? I don’t mean to say that there’s a parallel world, but that sometimes the math can provide a correct absolute answer when viewed from the other direction. What if?

    I don’t live in NY.

  45. eFarther says:

    Does time move smoothly, or does it skip ahead like the second hand of a cheap watch? If it skips, what happens during the interim period?

  46. KrisM says:

    Lately I’ve been thinking about Schrödinger’s cat and wondering about the expanding universe. If the universe is expanding at an ever increasing rate does this tell us anything about what’s outside the universe (i.e.,the Schrödinger’s cat thought experiment seems to imply that the observation matters so if the universe is expanding at an ever increasing rate does this mean that there is nothing outside the universe that is observing us?)? . . . ???
    No where near New York.

    BTW, no more anonymous posting? :(

  47. lerdos says:

    Is there such a thing as centrifugal force? Or are physics teachers just messing with us?I’m in NYC

  48. Jeff Dannaldson says:

    Is it possible that since closed-loop strings like the graviton could leak out of our 3-brane into neighboring branes via the hidden dimensions, that one could theoretically communicate between “universes” by encoding a message into graviton pulses (i.e. gravity waves)? 

    Granted, it would take a very advanced technology to generate such powerful gravity waves, possibly by manipulating neutron stars or black holes, but I’m assuming that such a civilization could exist.

    In other words, should we be looking for ET with gravitational telescopes in addition to radio telescopes?

    I live in the middle of the cornfields, i.e. not NYC.

  49. Tess Alexanian says:

    So, because ignorant physics questions are great: If mass increases as you approach the speed of light, did the neutrino that was, at least, near the speed of light in the recent experiments have a really large mass?  Did it exert any significant gravitational force?

    Also, why is our universe made of matter instead of anti-matter, if matter/anti-matter is generated in pairs? (I know we don’t have a solid theory on this- thanks, Wikipedia article on Baryogenesis- but it would be nice to hear some of the theories in non-technical language.)

    Not near New York.

  50. Jerry Sneed says:

    When I wear sunglasses, and the light hits just right, I can see the inside of my eye in the specular highlight coming off the frame. What I mean by the inside of my eye is, I see the floaters that would normally be blurry, but they are crystal clear. I know this isn’t one of the “big” questions, but something interesting is definitely happening here.

    I don’t live in NY.

  51. Nick Johnson says:

    Do you think we’ll find the Higgs boson before end of 2012? If at all? If not the Higgs, what mechanism do you think gives particles mass? Not in New York :(

  52. Rob says:

    Considering the size of the constantly expanding universe, and that I live in Toronto, at what distance from earth would an observer consider me to be in the New York City area? 

  53. markitect says:

    Is there any validity to the idea of multiple temporal dimmensions?  Why only one dimmension of time.  What about perpendicular time or cubic time.

  54. markitect says:

    Not in the NY area, so sad.

  55. B B says:

    What does Physics, as a discipline, need from society?  What are the effects of collapsing university budgets and diminished public endowments on the progress of our understanding of the universe?

    I do not live in NYC.

  56. SomeGuyNamedMark says:

    If “dark energy” is responsible for cosmological expansion and it is accelerating could it ever get to the point where individual atoms are torn apart?  And from there could it reach the point of subatomic particle and quark pairs being pulled apart?  But if it got to that point the energy required to separate quarks increases with distance until the energy input equals the mass of a new quark pair.  Could this suddenly cause the expansion to stop in a massive burst of new matter and possibly even tip it towards collapsing?

    Not in NY – QQ

  57. Tim Mankowski says:

    If the higgs boson is found how would it change everyday life?I’m in NYC!

  58. We know that the heavier elements in our bodies, like C, O, and N, come from supernovae.  Where and when was the supernova that is responsible for life on earth?  How did the material get from there to here?

    Belmont, CA

  59. Utenzil says:

    I have too many questions, sorry, but this is my chance to get these things understood.

    It is my understanding we are awash in neutrinos, particularly solar neutrinos: an incredible number of these stream through our bodies and our brains, it is my understanding that they pass through matter as if it wasn’t there. Before the concept of atmosphere was understood, it was not understood as being beneficial to life, even though humans were surrounded in it.

    In a similar way, we are just beginning to understand that we swim in a sea of neutrinos. Could neutrinos, especially solar neutrinos,  somehow be essential to life, or be required on some incredibly small level by living tissue? Our brains seem to be a lot like neutrino detectors in the way that they are designed, floating in liquid and encased in a dome. Could there be any interaction between neutrinos and the functions of the brain and/or our perception of time?  Also, if neutrinos travel faster than light, wouldn’t their mass change?

    I don’t live in NYC…

  60. Utenzil says:

    oh, and in the article after this one, if the lion puked while going around the wall of death, where would the puke go?

  61. w. m. says:

    I don’t live in New York City.

    Here’s my question…

    If you were to take a tube composed entirely of completely-reflective material, and were able to insert a beam of light into the tube (i.e. sealed off from the rest of the universe) would the light be reflected within the container ad infinitum?

  62. tomandersen says:

    Why does string theory still get studied, when after decades of research by hundreds of very smart people, nothing of substance has been discovered? 

    ref: Not Even Wrong, by Peter Woit, also look on the internet about it. Its a real question, that has answers that anyone can understand, as it revolves around sociology, not physics.

  63. Darden Swain says:

    If the universe expanded in all directions at the Big Bang and is continuing to expand, why can’t we tell where the exact center of the universe is?

    Not in NY

  64. rigo01 says:

    Is this scenario possible:    Lets say there is this star at point “A”, a huge star at point “B”, and Earth at “C” like this > “A”—————”B”—————”C”.  If star “B” is big enough can it bend the light going from “A” to “C” in a matter that light rays passing  above “B” bended to “C” ,and bellow “B”  bended to “C” so when it hits “C” (Earth) we may actually see two representations of “A” at the same time?

    Not in NY

  65. Adam Kaplan says:

    I work in New York City, and live in the greater metropolitan area.

    I have two related questions:
    As an undergrad I learned in Quantum Mechanics that particles exist in a superposition state until they are “observed” and their wave-functions “collapse.”  What does it mean to “observe” a particle?  Do physicists today have a better understanding of what happens when the wavefunction collapses than when this idea was first proposed and accepted?

  66. kullervo says:

    I’m about as far from NYC as you can get without a passport…

    Something about the expansion of the universe has always puzzled me. Leaving aside inflationary expansion for the moment for the sake of clarity, let’s imagine that the farthest object we can theoretically see is about 13.7 billion light years away. In the simple geometry of human awareness, we seem to be in the middle of a balloon, the “skin” of which is made of the oldest parts of the universe. But then that’s actually backwards, because those oldest parts belong to the youngest, smallest universe. So are we somehow looking inward onto that young universe and all those ancient objects are actually closer to each other than they appear, is time somehow flowing backward, or is the geometry just much much more complicated than my mind can grasp?

  67. milx mirukuchan says:

    Time travel. Since that the group of time travelers of the future practice Fight Club rules, we never get to know either time travel works or not, because if they do, they are here, now.
    If matter can’t travel through time, can consciousness, mind or spirit do so? How does consciousness works, and if it is ever a “matter” how will it look like?
    Human body may grew old and withered, but idea, mind and soul can be forever.
    milx, Kuala Lumpur, Malaysia

  68. libelle says:

    I don’t live in NY city nor state.

    Does modern physics assume time/space is continuous, or is there any good reason to believe it may be quantized?

    Why do people talk about the double slit wave/particle experiment as showing the dual nature of light as waves/particles. I’m certainly not trying to argue against quantum here, but it this experiment could be completely explained by a wave-only theory by anyone who has experience with slot antenna design.

    How the hell can I try to grasp M theory without getting graduate degrees in math?

  69. Peter Schotland says:

    err… what happens if you measure the position of a particle while simultaneously measuring the momentum of its entangled partner?  Does a hell mouth open up?

  70. I do not live in NYC – or near enough to attend; but I would love to be entered into the drawing.

    My question is: I have heard that Physics might not actually work the in the same way all across the universe. As in we might not actually know what happens to physics in deep space, or as we get to the far reaches of the universe. How is this possible? What does this even mean?

  71. Bloo says:

    Can’t attend – but one question that went round and round at work one time was:

    What freezes faster? Hot water or cold water?

    Some maintained the hot water, having molecules moving faster, lost energy more quickly.
    The rest of us maintain that the hot water has to cool first to the temperature of the cold water, then cool to freezing, so that the hot water takes longer.

  72. CGulow says:

    Why are so many physicists chasing String Theory when, after 30+ years, there is still no means of testing it?

  73. It seems to me (as an interested layperson) that all the recent attempts to find the Higgs boson are failing. Is this accurate? If so, what implications does this have for the future of physics? 

  74. Gardiner Moody says:

    Thought experiment/Question:
    1) A vessel breaks orbit with the Earth with a crew aboard
    2) The vessel remains as stationary as possible
    3) The vessel waits for the Earth to make one revolution around the sun
    4) How would time be percieved aboard the vessel? Slower? Faster?

    Since they’d be staying still, wouldn’t time slow down for them? It’d also be interesting to know just how much longer one Earth year would feel to stationary astronauts.

    Would combating the gravity of the sun (in order to remain in one position) be enough to keep time somewhat in sync with Earth? What if we removed the sun’s gravity from the equation?

    P.S. I do not live in or around New York City

  75. Mark Fletcher says:

    I don’t live in New York.

    I’ve been trying to answer a question that has been bugging me for a while about the EM spectrum – are there ends to it? I’ve been able to find heaps of resources about the ‘components’ (ie what wavelengths constitute microwaves for example) but nothing definitive about outer limits or boundaries at the radio and gamma ray ends.
    So there are a few parts to this question.
    1. Is there a theoretical lowest possible frequency wavelength that can be generated? (eg maybe we cannot have wavelength greater than width of universe, as no way to generate it).

    2. Is there a practical lowest possible frequency wavelength that can be generated? (ie cannot have a wavelength greater than ‘l’ because the energy of this photon would be indistinguishable from random quantum noise or something). I guess a subset of this question concerns detection – what is the lowest frequency we could detect.

    3. If there is a lowest possible frequency (theoretical or practical) what happens as spacetime stretches? What happens if this lowest possible frequency is redshifted a little bit, by being viewed by a moving observer? (this question ‘goes away’ if the maximum wavelength is determined by some metric of spacetime itself I guess).
    4. Is there a theoretical highest possible frequency wavelength that can be generated? (eg maybe we cannot talk about a photon having a wavelength smaller than the Planck length).

    5. Is there a practical highest possible frequency wavelength that can be generated? (ie cannot have a wavelength smaller than ‘x’ because energy required to generate this photon exceeds ‘y’, and there is no way to do that).

    6. If there is a highest possible frequency (theoretical or practical) what happens if that photon is measured by an observer travelling towards it at an appreciable fraction of C? Ie, if this highest possible frequency is blue shifted a little bit, what happens?

  76. just1n says:

    Is there an answer to zeno’s paradox, and if so, does it require that the universe be discrete? 

    Is the measurement of either matter/energy or space/time infinitely divisable in any given dimension, or is there some physical limit that constrains future divisability (e.g., the planck length/time?).  Is it possible for the answer to be different with respect to matter/energy vs. space/time (i.e., if space/time were discrete, I would assume matter would also have to be discrete, but if space/time were continuous, matter could still be discrete)?
    When Achilles tries to move a distance shorter than the planck length, does he disappear into the quantum foam, thus losing the race to the tortoise?
    In NYC

  77. shivas says:

    One thing that I have wondered about for some time and have never seen addressed by scientists is how much Earth changes over time due to accretion. Every space body that we have observed is pocked with craters from large chunks that have rained down, and in addition to this we are bombarded by many more smaller particles that do not make craters. Since the dinosaur age, 600 million years ago or so, how much has our planet changed by accretion. Is it significant enough to have a different gravity, and consequently a different atmosphere? Would it explain why there were large flying reptiles in the past, but no birds of comparable size now? Just wondering.

    John Dafoe, Vancouver, BC

  78. Hamm says:

    1st What are the best guesses to explain why gravity exists and how it works?
    2nd Can omnipotence possibly occur in our universe?
    3rd What good can better knowledge of the Higgs boson be for 7 billion people?

  79. Vlad Zabrodskiy says:

    1. Is time expanding as well as space? Is there a connection between time time expansion and “arrow of time”?

    2. Hypothetically speaking, what would be B.G. favorite hypothesis to explain “superfast neutrinos”?

    Live around NYC 

  80. We hear a lot about gravity being posisbly particle based (i.e. the “Graviton”).  what are some other ideas/theories as to how gravity might be conveyed?

    I am in the NYC area would love those VIP seats!

  81. Emory Anderson says:

    Not only do I live in NYC, I believe I went to the same high school as Brian Greene, though I graduated a year later. I was, however, previously a physicist myself (femtosecond optics), and in part 3) of my question below, you’ll see why I’m asking Brian (a theoretical physicist) this question.

    1) (More or less rhetorical) Given the age of the universe (approx 13.7 billion years) and its size (100s of billions of galaxies), what is the likelihood that species have arisen that are in possession of technological capabilities far in excess of what humans are currently capable of?

    2) (Not rhetorical) Do you believe there’s an upper limit to what advanced technological societies could do?

    3) (Very not rhetorical) Given the possibility of the existence of species that can impact the greater spacetime geometry of the universe, are there any fundamental constants that, based on superstring or Brane or other theories, one might suspect are no longer what they should be ‘naturally’, but may actually have been engineered by said advanced species?

    4) (Extra credit) Can you imagine tests that would detect whether fundamental constants or other measureables may have been impacted by extremely advanced engineering? To what purpose?

    • Jim Saul says:

      Would it count if, instead of an intelligence in our spacetime, one applied energies in a calculated way when she created the black hole the event horizon of which marks the outer boundaries of our spacetime?

      “If you take Pi out to enough digits it becomes a binary message” ;-)

      A question that’s been on my mind for years is related, though less ambitious than yours…

      If the LHC, Tevatron, ELI Ultra-High Field laser and other projects “generate conditions not seen in nature since the birth of the universe” are there potential signatures of such experiments in, perhaps, particular patterns of gravity waves, that might hypothetically tell us that someone, somewhere else in the galaxy, achieved what seems impossible to us primates – they managed to sustain long term public support and funding for fundamental research.

  82. Brandon Horn says:

    1. Why does our macroscopic universe have 3 space dimensions? Fewer get ruled out by the Anthropic principle, would more get ruled out as well? Keeping the elementary charge the same, how would an electron behave in a 4D hydrogen atom? Would hydrostatic equilibrium allow for star-like objects that could fuse heavier 4D atoms, or is 3 dimensions the only universe that works for building complexity?

    Can’t use tickets, just DVDs

  83. Cameron Popp says:

    1) What is the relation, if any, to dark matter and dark energy?  And would Einstein’s E=mc^2 be applicable here?

    2) How feasible is it to create a particle that would ‘decay’ into dark matter?
    3) Given the multiple dimensions suggested by string theory, is there any realistic method of showing these other dimensions exist?

    I live in Ohmygod, Nebraska.

  84. franka_645 says:

    1) Are there any universally applicable units for time or length (or any anything else) which could eliminate the need for some of the constants in calculations? 

    2) With more advanced instruments would it ever be possible to measure both the momentum and position of an electron?

    3) What would be the research applications if absolute zero were to be achieved?  Is this possible?

    (not in NY)

  85. tkinsman says:

    How does electron entanglement work?  how can one particle affect the actions of a second at a remote location?

  86. r matt says:

    Long-time reader, first time commenter! I live in New York City, and would really love to get to go to this!

    My question: 

    How does four-dimensional space differ from spacetime? Is spacetime simply a specialized theoretical instance of a four-dimensional space, much like how a bourbon can be thought of as a more specialized iteration of a whiskey? How does n-dimensional space function, and interrelate to String Theory? It’d be great if you could explain these things to me like I am five. 

    Finally, and perhaps most crucially: if there are n-dimensional beings, are they both squamous AND rugose, and would their non-Euclidean geometry qualify as ‘eldritch horror?’ 

  87. Kevin Dick says:

    I’ve always envisioned particles as the nodes on a standing wave (or the peak of an oscillation) of energy moving through spacetime. Is this a helpful, if oversimplified, way to envision how we can have “solid” particles with wave-like activity? Would anti-matter be the bottom of the oscillation in this case?

    Not a physicist, so keep the snickering to a minimum.

  88. BK says:

    Chemists don’t account for the accelerated expansion of space in the universe when they calculate the structure and motion of molecules, but cosmologists take it into account when they describe the structure and motion of the large scale universe.  Is it possible that dark energy/matter has trouble interacting on small scales as opposed to large ones?  Or is it instead known with certainty that other forces simply wash out any observable effects of the expansion of the universe on the scale of atoms and molecules?   For example, should we expect that one day we will have to take into account the expansion of space in order to understand something about the vibrational spectrum of molecules, or might dark energy abhor such smaller spaces between atoms in a molecule? 

  89. Brian,
    Regarding the entropic explanation of gravity that has garnered a lot of press attention; you mentioned on Science Friday that it has many of the features that you would expect from a theory of everything, but you were unconvinced that it is a worthwhile theory. Why not? Is there experimental evidence pointing in one way or another, does anyone have any predictions for or against it, or is there some other reason that it seems less interesting as an avenue for research than string theory, or other ideas you have championed?

  90. Steve Clark says:

    I drill a hole at the North pole, all the way down to the South pole. I drop a brick down it. What happens to the brick? Let’s ignore friction from air.
    I live in London. Have a great time in New York.

    • florb63 says:

      It will oscillate! If I remember the numbers correctly it makes the trip from pole to pole in about an hour and a half.

  91. Bryan Lewis says:

    I’ve always wondered this:

    If I was on a hypothetical airplane going faster than the speed of sound, and then yelled a sentence out of the window, would someone in front of me hear that sentence backwards? (Assuming that they could hear the sentence over the noise of the airplane…)
    Don’t live in New York

  92. Timothy Ealey says:

    With The LHC being up and running for several years ( & at high energy levels) & not finding proof for the graviton, Higgs boson or supersymmetry, Do any of the physicist on the panel believe that their is fundamental lack of knowledge but these do exist or that they do not actually exist? And Does the cost of the LHC (taking note of its failure to observe those “phantom particles”)give you pause in supporting new expieriments with high price tags & basic lack of theory?

    Timothy Ealey

  93. stephen davidson says:

    What would a creature who could move freely in the 4th dimension need to be like?

    Not in NY, sadly

  94. IceCream says:

    To the astonishment of physicists around the world, the Large Hadron Collider has unleashed a new force that is threatening to destroy the Earth.  The only hope for humanity is to understand the physics of this new, unforeseen force and reverse the steps that led to its creation.

    You have the power to clone three physicists from the past to help you save the world.  The clones will be created instantly, with a full understanding of modern physics, and they will function at their intellectual prime.

    Who do you choose to clone?


  95. trent1492 says:

    Dr. Pearlmutter,

    You are one of the co-authors of a paper just submitted for peer review that reconfirmed the existence of Global Warming.  Yet,  Dr.Judith Curry, another co-author, is  now saying that in fact a cooling trend is underway.  Could you clarify what the findings actually are?

  96. Ian Brooks says:

    Weird idea I came up with when I was a kid about the near infinite nature of the universe. I long ago reconciled the belief in extraterrestrial life because of the sheer number of stars and planets out there, mathematically speaking even given the extreme number of variables that had to come together on earth for life to thrive, odds are it’s happened over and over and over again. In fact, it could possibly have happened several million or billion times over. So what are the odds it could have all happened somewhere, exactly the same way it happened here, down to the thing you had for breakfast yesterday and the time and date we discovered fire? 
    -Anchorage, AK

  97. Neng Lee says:

    14 Billion years ago, the edge of the universe was not very far from the location which would eventually be occupied by planet earth.  The distance certainly wasn’t 14 billion light years (let’s say 1 light year).  Why is the light from there that is now reaching earth 14 billion years old, when it could have reached “pre-earth” in 1 year?

  98. Gregory Payne says:

    Humans have been by far the most dominant species to inhabit the earth. Many people believe that according to the second law of themodynamics, “things” become less orderly with time and thus the useful energy available dissipates. What is it about evolution that drives continued complexity, defying the path of nature?

  99. gmillerg says:

    If space = time and matter = energy, could time = energy and space = matter?

    • Gregory Payne says:

      I’ve never heard of someone relating space and time like matter and energy. What do you mean by that?

      • Antinous / Moderator says:

        Space, time, matter and energy only exist as expressions of the relationships between the others. Time doesn’t need to exist unless matter or energy move in space, and matter and energy are, in a sense, movement.

      • gmillerg says:

        Well space and time have been shown to basically be two different sides of the same thing.  Space doesn’t exist without time and time doesn’t exist without space.  And matter and energy are interchangeable as well (E=mc2).  So I’m wondering if there is a similar relationship between time and energy, space and matter, or even time and matter.

        • Antinous / Moderator says:

          So I’m wondering if there is a similar relationship between time and energy, space and matter, or even time and matter.

          Space isn’t a thing in and of itself; it’s a description of (spatial) relationships between things (matter and energy.) Time is a description of (temporal) relationships between things. If you remove all matter and energy, space and time don’t exist. Conversely (and somewhat more intuitively) matter and energy don’t exist without space and time. All four are dependent on the others for existence.

        • Gregory Payne says:

          Oh I see what you mean. Isn’t that like saying I can’t exist without oxygen? How can I be related to oxygen in the way that space is related to time?

  100. Gregory Payne says:

    I realize my first question wasn’t exactly related to physic’s so I have another one:
    Many people claim that space and time are continuous. Could you give a simile or metaphor to make this easier to understand intuitively? Why can’t space and time be quantized? If they can, could they behave like photons, having a wave-particle duality?

    Greg Payne
    Columbus, OH

  101. Daniel Thron says:

    if every point in the universe is expanding, could gravity simply be the effect of the inertia of being ‘scaled up’ like this?  Like if a person were standing on an expanding sphere, the sphere would push them upward as it expanded — even if they were expanding up at the same rate.  Their relationship would be the same, but the inertia would make them ‘stick,’ right?

    I don’t live in NYC.

  102. iaasacu says:

    Imagine I shoot an electron through a non-homogenous magnetic field to a screen with two slits in it. I should be able to do this in such a way that all the spin up electrons go through one slit and all of the spin down electrons go through the other slit. However, since it is unknown whether each electron is spin up or spin down, there should still be an interference pattern.

    Now, imagine that each electron that I shoot at the screen is entangled with another electron that I keep back at my lab, in such a way that for each spin up electron I shoot at the screen, the corresponding electron back at my lab is spin down, and for each spin down electron I shoot, the corresponding electron is spin up. Since I can now determine which  slit each electron went through, I should not get an interference pattern.

    Now imagine that I take all of the electrons from my lab and give them to you, and you travel a large distance away (say, to another galaxy). If you measure the spin on your electrons around an axis at right angles to the axis we have been discussing so far, you will have destroyed any information about the spin of my electrons around what has until now been the significant axis. If you do this before I shoot the electrons at the screen, it will be impossible to determine which slit each electron went through, and I will get an interference pattern. If you do not destroy information about the spin, I will not get an interference pattern. In other words, by destroying or not destroying the information about the spin of my electrons, you will be sending me a bit of information instantaneously (at faster than the speed of light). My question: where is the fallacy?

    I live in NYC

  103. Janet McKenney says:

    Do you think more of the world’s problems can be solved by applied or theoretical physics?  Can you explain the difference for the layperson.

    I’m in Maine.

  104. Alison Harmon says:

    There are four main physical LAWS: electromagnetism, gravity, strong force and weak force. The idea of a unified field theory like String Theory is to create an overall language to encompass all of these. As you add dimensions with lower energy laws like these pop out. But if there are only four main laws that we are looking for, why are as many as 10 or 12 dimensions posited?

  105. flagler23 says:

    Are we living in Schrodinger’s box?  That is, if according to inflationary cosmology no particle or information can pass from one universe across the inflaton field into another universe, then for an “observer” in one of the other universes, is our entire universe not then completely described by quantum mechanical probabilities scaled up-where nothing at all has collapsed to a definite state?  If so, how does that reconcile with the fact that I am very definitely asking this question, and not some other question?

    I don’t live in NY

  106. Michael Hood says:

    If we can prove the existence of multiple dimensions, then we must know something about them, right? I mean what is in these other dimensions? Or what does having extra dimensions even mean?

  107. flagler23 says:

    I don’t know if my previous question went through.

    Are we living in Schrodinger’s box?  That is, if according to inflationary cosmology no particle or information can pass from one universe across the inflaton field into another universe, then for an “observer” in one of the other universes, is our entire universe not then completely described by quantum mechanical probabilities scaled up-where nothing at all has collapsed to a definite state?  If so, how does that reconcile with the fact that I am very definitely asking just this one question, and not all possible questions at the same time?

    I don’t live in NY

  108. swd1 says:

    I don’t live in NY and I’m not a physicist.  This is part question and part request to discuss the boundary between the quantum realm and classical/macroscopic realm.  I question how you can extrapolate from the quantum realm to the classical realm and claim there are
    multiple universes.  In the quantum realm, a particle, mass or massless, appears to be in multiple locations at the same time until the particle reacts with the environment and “decoheres” by then appearing to be located at a specific point (as in the common double split experiment using light, electrons, bucky ball etc.).  Two prevailing views of how this occurs include the following:  1. the probability wave collapses and the wave character of the particle suddenly transforms itself (mechanism unknown) into the particle character of theparticle and 2. each potential point that the particle could be located in as expressed by the probability wave when it decoheres represents a separate universe thereby generating countless offshoot universes.  And by countless I mean countless especially when you consider circumstances of this type occurring every nanosecond in an already expansive universe.  In the macroscopic realm the wave character of an object is nill and the particle character of an object reigns supreme.  This cuts down the probability of being in two places at the same time considerably.  How could a macroscopic being ever be in a circumstance in which it finds itself splitting into different universes?  Schroedinger demonstrated the folly of this thinking with his famous/infamous thought experiment with the mouse (just kidding).  True, we are composed of quantum entities, but aren’t they in a decoherent state?  It’s not easy keeping quantum particles in a coherent state; ask anyone trying to develop a quantum computer.  Therefore if we are composed of particles in a coherent state and our mass makes our wave nature negligible, how could we ever find ourselves in a circumstance where we are splitting into different universes?

  109. Peter Xu says:

    I live in NYC.

    If a multiverse existed, and if alternate realities actually branched off each time a decision was made, there would be an infinite number of worlds. Is there a theoretical limit to how much the cosmos can hold? What prevents it from becoming over-inflated with information?


  110. florb63 says:

    Is it possible that the answer to the dark matter mystery lies in a new theory of gravitation for extremely large scales, just as quantum mechanics supplies a new theory for the very small? If so, there need be no mysterious particles hiding out there but the same old particles acting according to a ‘more general’ general theory of relativity. Or is the general theory already established for these galactic scales?

    I live near NYC.

  111. On the subject of dark energy: is it conceivable that the reason for the accelerating expansion of the universe is not some form of mysterious energy, but in fact an artifact of relativity? If space were curved in a particular way, such that after the Big Bang the mass-energy followed that gradient, it would be possible that it would appear to the observer that everything was accelerating due to some invisible impulse, but in fact, was just following the curvature of space. Does this sound reasonable?

  112. BodyJCount says:

    Will advances in genetics and the medical sciences continue to increase the average life expectancy of humans? Is there a theoretical limit? Earth’s human population recently topped 7 billion, do scientists have any expectation of when population growth will become unsustainable end even possibly collapse?

    Not in New York :-(

  113. Technoangina says:

    Is it possible that within a multiverse there would be naturally existing connections between the two or would the distances between universes be too great to traverse without universal collision? 

    I do not live in NY.

  114. moonglum says:

    If there are an infinity of universes, how large is that infinity. Aleph null, aleph one, or what? And if there are an infinity of multiverses, how large is that infinity?

    I live in Austin (not NY), and like DVDs.

  115. If CERN’s recent test of a superluminal neutrino proves to be true and accurate, how would this effect fundamental properties of the universe such the red or blue galactic shifts?

  116. MarkS says:

    Can you explain why particles have ‘spin?’ and why quarks have flavors? What is spin, does it have effects on human scaled objects or on Galaxy sized objects? Is it related to other dimensions or forces or  is it the result of  certain events?

    I have doubts about the cosmic redshift. Not that it exists, but that the explanation is as simple as a dopler shift. Have other theories been mooted and what were the results? Here’s a theory: time is two dimensional and the matter that appears red is on a divergent vector. Another: Space-time has a “color” that distorts wavelengths of light, redder and redder the further  you look into it. Could we do without a big bang?

     How does an atom get a “field?” Isn’t that empty space between one atom and another? Magnetism is passed like light, in quanta, but how do the packets of quanta know where to go? Do they shoot out in all directions like pollen and only register if they hit their mark?

    Newton  described gravity with elegant equations. The math describes what happens between the things gravity acts on, but it doesn’t explain what it is; gravity is just assumed.    Are we in an similar situation with Einstein’s equations and the thing called the fabric of space-time? Is there a thing that we’re all swimming in? An Ether?

    I’m in LA, trying not to be a crank

  117. iris nelly gomez-lopez says:

    what are your expectations of the public that will have access to this kind of science? Is marketing influencing the way you make science?

  118. JD Fekula says:

    A century from now, how do you think future scientists will regard the last 25 years of physics?

    (I’m in the NYC area)

  119. reikonyc says:

    What is the connection between time and matter? Time is linear and the universe is expanding. If the universe contracts, would time reverse? 

    Reiko (I live in NYC)

  120. Neil Franciotti says:

    If you were in the position to choose one grand scale project to put a great amount of money and brainpower behind, modeling the exceptionalism of say the Manhattan Project, what would it be, or what area of science would you grant the project to?

  121. catonpalm says:

     If a person go out exploring space, get too far, time become distorted from Earth time, would that affect the person?

    I’m not anywhere near NYC.

  122. Peter says:

    What causes inertia

  123. Penter says:

    If E=mc2 does g=m/c2?

    I do not live on the East Coast.

  124. Penter says:

    If static electricity causes electrons to be exchanged upon contact, does this mean when I pet my cat, there is a transfer of cat electrons to me?  

    Perspiring minds want to know.  

    I still do not live on the East Coast.  Neither does my cat.

  125. teufelsdrochk says:

    The yield of corn has undergone radical improvements through breeding. 

    Is it possible to breed the inedible oilseed-producing plants (jatropha, pongamia, moringa, etc) to produce oil from wasteland?

  126. teufelsdrochk says:

    The Stirling Engine produces electricity from heat, particularly solar heat. Can the price per watt of a Sterling engine be brought down below $1/kW via mass production? In particular, can a $100, 1kW dish-solar Stirling Engine be produced?

  127. Andreas Beer says:

    If I had a snapshot in time of a swinging door, is there any way to determine in which direction it is swinging? I never got this “kinetic energy” part.

    • Jim Saul says:

      I totally get what you mean by your example, and it’s a great question, but because the door is hanging on several hinges, which support different amounts of the door’s weight and are not frictionless, you probably could tell from a photo by the angle of the door to plum, perhaps even by a microscopic amount of flexing in the material of the door.

      Now a door hurtling through a vacuum you couldn’t… hey… is that image in the opening of twilight zone or outer limits?

  128. Sabrina Ahmed says:



    I am SUCH  big fan!! :D

    How is your son??!!

    (I apologize for the unrelated post! I’m not sure about what to ask you since I don’t feel that I know enough!! I just couldn’t help it!! I wish this  could be my first Brian Greene event!! I live 30 minutes away from Columbia too!!! Sighs…) 

  129. Charee Peters says:

    Based off of recent discoveries in high energy/particle physics, we have quite a few constraints on what dark matter should be particle-wise. Doesn’t it seem odd though that we still have yet to detect this at all? Especially if there is so much of it in the universe.
    Also we know that all other fundamental forces work at different ranges, except for gravity.
    So why are so many people ruling out the idea that there is something wrong with the way that we view gravity?
    I think I know a decent answer to this question, but I really like to ask people to see how they explain it. :)

    (Nashville, TN)

  130. Momma Bear says:

    Does light move faster or slower in a dark hole?  (hypothetically.. of course)

Leave a Reply