TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Questions on physics you always wanted to ask, but were afraid to

Discussion in 'Off Topic' started by Mario Kadastik, Sep 27, 2013.

  1. Mario Kadastik

    Mario Kadastik Active Member

    Joined:
    Sep 5, 2013
    Messages:
    2,043
    Location:
    Rae, Harjumaa, Estonia
    As I've pretty much read through the forum from one end to the other and my Model S will only arrive in January I thought of starting yet another time killer thread (I just can't work...). There are always tons of questions people have and when they hear I work at CERN they offload them to me :)

    Just to start off:

    * Yes, we do make anti-matter
    * No we don't have a ramjet space plane ;)
     
  2. SwedishAdvocate

    SwedishAdvocate Active Member

    Joined:
    Jul 26, 2012
    Messages:
    1,648
    Location:
    Sweden, Earth
    Sure! I got one:

    Any ideas on how to solve this one? :rolleyes:
     
  3. Mario Kadastik

    Mario Kadastik Active Member

    Joined:
    Sep 5, 2013
    Messages:
    2,043
    Location:
    Rae, Harjumaa, Estonia
    That's a tough one. The large part of our protection comes indeed from the magnetic field that sends majority of the solar wind or charged particle flux around the planet. We do still get hit with it plentifully as the field is dynamic and a strong solar wind will "blow away" it partially and modifies it. The main impact of course is cosmic radiation (that partially can be alleviated with a thick atmosphere, especially ozone) and the electrification of the surface. The latter is somewhat of an issue for any power distribution network and is actually an acute hazard for Earth as well (it's only this summer that a major blast from the sun passed by us missing us by a mere two days, it could very well have caused major transformer damages across the whole northern hemisphere with repairs taking months if not a year).

    However we could probably bolster the atmosphere through terraforming (introducing algae that can survive in the martian weather and produce oxygen etc) and build the power grid well enough that it could take the hits without blowing up. It is to an extent a design choice as current grid design is flexible, but susceptible to such damage, but it's not the only design that works. Also, on Mars we'd have an even longer pre-warning of an oncoming solar blast so people could get to shelters and the utilities could take care of the grid. What the proper effect of regular lack of solar wind is on the populace is more a question to someone in biology that I'd defer, but I think natural selection over a number of generations would make us a bit more resilient as well. It's already taken place on earth where people from higher radioactivity regions are a bit less susceptible to the radiation damage due to constant background.
     
  4. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN P65513, Model 3 Res Holder

    Joined:
    Jan 29, 2010
    Messages:
    6,097
    Location:
    Redwood Shores, CA
    Mario, how far are we from controlled Fusion?! What are the impediments? Thanks!
     
  5. Discoducky

    Discoducky Active Member

    Joined:
    Dec 25, 2011
    Messages:
    2,884
    Location:
    Seattle
    I'm interested in your thoughts on Higgs boson and maybe solving the mystery of gravity. You know, coffee table discussion! Thanks for starting the thread!
     
  6. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

    Joined:
    Mar 24, 2013
    Messages:
    4,231
    Location:
    Denali Highway, Alaska
    Well, if you don't have one, how can you possibly live in Estonia yet work at CERN? :)
     
  7. Mario Kadastik

    Mario Kadastik Active Member

    Joined:
    Sep 5, 2013
    Messages:
    2,043
    Location:
    Rae, Harjumaa, Estonia
    Well the classical saying for the past few decades has been that controlled fusion is ca 50 years away :) That statement has been constant with the passage of time which effectively tells us that we don't know for sure. The problem with fusion is not from physics side, we know how it works, we have a stable fusion reactor called the sun working daily and we've already harnessed the power artificially in hydrogen bombs.

    Now to illustrate why this process is so difficult to achieve I'll tell you how the H-bomb works. Basically to detonate the H-bomb and achieve temporary fusion that releases a massive amount of energy one first detonates an atomic bomb as a trigger. The A-bomb explosion compresses the inner core consisting of helium to extreme pressure and temperature (millions of degrees) igniting the fusion reaction that then explodes at an order of magnitude higher energy than the triggering A-bomb. Now to have a stable fusion reactor you need to not just make it happen in a fraction of a second, you'd want it to keep going for hours. This means effectively maintaining a temperature of millions of degrees at absurdly high pressures.

    So the classical fusion reactor design is entirely depending on proper material research as well as developments in strong magnetic fields (as you cannot have the extremely hot plasma touch the surfaces of the reactor, they'd melt instantly). There have been development of computer controlled dynamic fields that might reduce the requirements of stable operations, but it's still a tall order. Another avenue investigated is using high intensity laser beams to create fusion in a tiny space. This is also a promising avenue as we'd not need huge and complex apparatus and keeping the plasma at high intensity, but I can't imagine running this at scale ...

    The holy grail of fusion though is LENR (Low Energy Nuclear Reactor) or cold fusion. This however is still purely speculative. There've been over the years a few claims to observing it, but never conclusively repeated. It's also a field that pulls in tons of crackpots that fizzle money out of investors by promising cheap energy sources and never deliver. The latest is the Rossi e-cat device that according to him is a true cold fusion device and a few preliminary papers seem to indicate that independent research and validation has been done. However closer inspection shows that no true scientific check has been done as he never allows to investigate the core of his device nor run it on independent wiring therefore causing far too many questions that allow duping. My bet is that it's yet another swindling to get investors money and disappear, but we'll see.

    - - - Updated - - -

    Oh the Higgs boson is extremely exciting. When I started at CERN in 2004 I was still doing my BSc and the whole premise of Higgs discovery was on everyones mind. It was the last missing piece of the standard model puzzle, everything pointed to its existence, but it had always eluded detection. The original physics program of my experiment expected to be able to say something about the Higgs after ca 3-4 years of running at design intensity and at design energy. Then the big explosion happened in 2008 and the whole project was delayed for 2 years. People went back to the drawing board and using their skill and cleverness and continued to improve on their analysis until in 2011 we were able to show first evidence that this particle may be within our reach and then finally after many sleepless nights prove its existence conclusively last July.

    You can't imagine what was happening behind the curtains. At CERN there are two main experiments at the LHC that were after the Higgs: CMS and ATLAS. I'm in CMS. There was already years before an agreement that if one experiment has reasonable evidence of a discovery they will tell the other experiment and give them time (~1-2 weeks) to validate. If the other experiment concurs, then a joint press conference is made and papers are submitted simultaneously. However there was still the question of who'd find something first and when the machine was first turned on there was a lot of scrambling to dig through the data for new physics. Rumors popped up and a hundred people spent their easter vacation digging through a petabyte of data that needed to be transferred, reprocessed and analyzed. Most rumors were debunked and forgotten in weeks, but it was still a lot of work. Then in late 2011 the data started to point towards a fluctuation that didn't seem to want to go away. The experiments talked and both were seeing similar things (this was at high level only) so they agreed on a joint status report in December. The result was that both showed ~3 sigma (99.7% probability) evidence for a possible Higgs boson, but in the scientific world 0.3% is still huge (an experiment produces on average hundreds of plots a day, statistically we should see a 3 sigma fluctuation every few months). So in 2012 when the machine resumed running and new data was coming in everyone knew it was a race if it REALLY was the Higgs. Everyone worked 16+h days and all analysis were blinded (i.e. you checked the rest of the plots, but not the expected signal region) until approved. Then a cross check was done when we had ca 20% of new data in comparison to what was presented in 2011. The bump was still there in the new data so the stakes went up even further. People were analyzing the data within days of it coming from the hardware and when a concrete decision point (equal amount of 2011 data) was reached both experiments showed that they expect to be able to see the particle. So the director general announced a press conference. At the time we didn't yet know for sure if we had it. We (the collaboration) saw the results approximately 1 week before the press conference and marvelously it came together to just 5 sigma that is historically the level of discovery. The press pretty much estimated this to be the case when Higgs, Englert etc were invited to CERN for the press conference :) I remember doing a live feed in Estonia of the press conference with local media present, giving interviews to the newspapers and the national TV. It was a fun moment. And since then we've been able to nail the particle down even further. It sure as hell seems to be the Higgs boson.

    Long ramble about the backstory over, the particle itself presents a bit of a conundrum. Its mass of 125.3 GeV is at an odd spot. Namely at this mass it decays to pretty much all particles that it can decay to in rates that makes this mass the experimentalists wet dream as we can measure so many independent channels and glean information from it. Yet this mass is also far higher than pure model stability would allow. At 125 GeV it's about 5-7 GeV above what would make the vacuum stable. Yet there are uncertainties. Whether our universe is stable or not comes down now to the mass of the top quark, the mass of the W boson and the mass of the Higgs. Those three define if the vacuum is stable, metastable or unstable. Right now the central value is in the metastable region. If we can reduce measurement errors with more statistics and better techniques, then we can answer this better. If the universe indeed is metastable, then at some point in the future we may tunnel to the true vacuum and the universe as we know it would be destroyed. This in fact may have happened already somewhere, but the tunneling effect would be propagating at the speed of light so we'd never see it coming. Anyway, it's more likely that there is some high energy phenomena that we've not yet discovered that stabilize the vacuum and make our universe nice and comfy, but right now the discovery answered some, but created a bunch of new questions.

    With regard to gravity, that's a tough boy to crack. The most common idea is that it's really an effect of the spacetime continuum. But there are plenty of hopes to quantify it and merge into other theories. However that's still far out :)

    - - - Updated - - -

    CERN as such employs very few people. There are a few researcher positions, but they are extremely rare. Majority of the research is done through collaborating institutes. So in fact I work for my home institute here in Tallinn, but I'm registered at CERN and work at a CERN experiment (CMS). I regularly fly to Geneva and work there, but a lot of the time I'm in Tallinn. Majority of high energy particle physics these days is extensive data mining and code writing. We've got to analyze ~1 PB of data per year in raw (though the actual processed data + simulation is more like 0.4-0.5PB). And we employ distributed computing with tens of thousands of compute cores and hundreds of PB of storage distributed globally. Some of the stuff we analyze locally and others we send to the Grid (the predecessor of Cloud computing) that computes it where the data is.

    But overall if I need a week at CERN I take a 6 AM flight from Tallinn through Helsinki or Frankfurt and am in Geneva around 10 AM local time. To fly back I take the 7 PM flight on Friday on the reverse route and arrive around midnight. Perfect work week :)
     
  8. NigelM

    NigelM Recovering Member

    Joined:
    Apr 3, 2011
    Messages:
    13,257
    Location:
    Sarasota, FL
    If I fly east to west across the international date line I cross back into yesterday. Given that it's easily possible to circumnavigate the world in less than 24 hrs, if I go around and cross the date line again can I go back to the day before yesterday?
     
  9. Sparky

    Sparky Member

    Joined:
    Aug 13, 2012
    Messages:
    211
    Location:
    Glendale,CA
    #9 Sparky, Sep 27, 2013
    Last edited by a moderator: Mar 13, 2016
    In the weeks leading up to dialing up the LHC to it's rated energy there was much discussion about the creation of microscopic black holes possibly leading to uncontrollable accretion of matter and the destruction of the planet. That evidently didn't happen, since I'm here typing. Can you tell us how seriously the doomsday black hole was considered at CERN and what hypothesis was the basis for it being a non-issue in the minds of those with their finger on the neutron star button?

    At the time, I just couldn't get the Farm Film Report out of my mind.

     
  10. Krugerrand

    Krugerrand Active Member

    Joined:
    Jul 13, 2012
    Messages:
    4,271
    Location:
    California
    I've got this piece of popcorn stuck between a couple of molars and I'm outta floss. What now? :redface:
     
  11. mkjayakumar

    mkjayakumar Active Member

    Joined:
    Aug 18, 2012
    Messages:
    1,736
    Location:
    Plano, TX
    Where does string theory fit into all this ? I haven't heard much around the string theory lately though.
     
  12. RDoc

    RDoc S85D

    Joined:
    Aug 24, 2012
    Messages:
    1,569
    Location:
    Boston North Shore
    So my 1st question is:

    If we go with gravity as space/time being warped by mass, thereby curving the shortest distance between two points, why do two massive objects at "rest" relative to each other accelerate towards each other when released. This is not the same question as why a moving object follows a curved path when passing by another massive object.

    My guess is that both objects are moving through time and their masses warp space/time such that as they move along the time axis they get closer in the space axes. Is that a reasonable model?

    My question B is:

    Consider walking down the street, swinging one's arms and legs. The hands and feet are moving with some velocity relative to the head, so they are subject to time dilation (not much, but > 0). Does that mean that our hands and feet are essentially "behind" us on the time axis and we're looking back down that axis to see them?

    - - - Updated - - -

    Something to consider is that the Earth's magnetic field flips North for South every 100K years or so, it's happened several times within human existence. My understanding is that we may be currently in the process of another flip starting. No one knows how long they take, but it does appear that the magnetic field is at least seriously disrupted and perhaps very weak for decades or a few centuries (or not, no one really knows).
     
  13. ZBB

    ZBB Emperor

    Joined:
    Feb 27, 2013
    Messages:
    1,417
    Location:
    Scottsdale
    Would you be up for a trip to the North Pole to test your theory? We could walk back or forward a year or so in just a few minutes...
     
  14. spaghetti

    spaghetti Member

    Joined:
    May 10, 2013
    Messages:
    245
    Location:
    Silicon Valley
    In an S 85, at what latitude would you be able to go back one month?
     
  15. evme

    evme Member

    Joined:
    Jul 5, 2013
    Messages:
    616
    Location:
    NY
    Liquid fluoride thorium reactor, yes? no?

    What would be easier to teraform, mars or venus?

    What is the theoretical maximum energy density of lithium-ion?

    You said that it is possible that somewhere in the universe, it can be collapsing at the speed of light and we would not notice it. But isn't the universe expanding at the speed of light as well? Considering that we are seeing things that are billions of years old and our planet is billions of years old, would the universe stop expanding at that point?

    At this point, is the big bang still the most prevalent theory?

    How far away are we from a true quantum computer?
     
  16. Mario Kadastik

    Mario Kadastik Active Member

    Joined:
    Sep 5, 2013
    Messages:
    2,043
    Location:
    Rae, Harjumaa, Estonia
    Easy answer: no. The dateline is an artifact of the local time definition. You have the GMT time and +- 12h from it. Crossing the date line artificially puts you into "yesterday" in local terms, but it's not a time function, just local definition. All regions of earth have some form of local time and you define your current time in the reference of your local time. Therefore crossing the date line twice in 24h will not be an actual phenomena because you'll have to cross over to today at some point in the meantime again :)

    - - - Updated - - -

    It was considered thoroughly. If you want you can read the actual safety assessment report: http://lsag.web.cern.ch/lsag/LSAG-Report.pdf

    Not only were black holes considered, but also strangelets and other phenomena that people were worried about. The basics come down to this. The LHC collides particles at basically speed of light. If a black hole were to form (a microscopic one that is) it's evaporate before it could move even an inch. For it to be a problem we'd need to firstly throw out the hawking radiation theory and make the black holes stable. Now even if they were stable they'd be microscopic and for them earth would be almost as empty as empty space, they'd be hard pressed to accidentally stumble on particles to eat up. The second issue is that because the initial particles were moving at the speed of light the probability that the created black hole would have an initial velocity below earths escape velocity is minuscule. And if we stretch the probabilities even further and make them be stopped and have them gravitationally aggregate to earths core it'd still take billions of years for them to gain enough mass to actually start to be felt. If it shot out and went to the sun i.e. velocity below solar systems escape velocity, then that'd have a faster effect, but still billions of years from now.

    And the most relevant piece of data is that the universe has been doing far higher energy experiments with earth for billions of years from cosmic rays hitting earth and we're still here so the whole question is somewhat moot :D Oh and I don't know if you heard at the time, but CERN was taken to international human rights court by some crackpots who thought CERN was putting the whole human race into danger. The case was dismissed though ;)

    - - - Updated - - -

    You wait in basement until your fingernails grow long enough and then use those? ;) Not really a physics question so I'll defer it to others. The physics solutions are plentiful, not necessarily pleasant ones (i.e. hammer and chisel to extend the crack where the piece of popcorn is stuck).

    - - - Updated - - -

    The reason is that string theory as it stands is something for mathematicians to have orgasms about. Its usability in physics hasn't been shown yet. The main reason being that it's too general a theory, it contains so many free parameters, that you could make the theory do pretty much anything you'd like except you have no clue how to tune it to make it do the things we observe in the real world. It's a mathematical generalization that probably has as a subset the current theories, but noone's really able to calculate anything with it and noone's found a way to falsify it (a requirement of any physics theory is a test to falsify it, until that exists it's just mathematics).

    - - - Updated - - -

    I have to admit, I'm not too fluent in general relativity therefore take it with a grain of salt, but in general I'd say that yes this is a correct interpretation. They both warp spacetime and as their fields merge they warp the space axis that connects them to be shorter and they move towards each other. The classical representation of 2D surface that is bent isn't a good illustration of 4D space, but even there the curvature is smaller in the axis between the objects than to the rest of space giving preferential movement towards each other.

    Sure, any objects moving would experience minor time dilation, but it's extremely small. But indeed any object moving faster than other objects would in relative terms be behind in time :) It's an actual effect going to space and coming back etc, but it is an effect that is actually used daily by for example also GPS satellites :) They were going out of sync initially all the time until they incorporated time dilation from their orbital motion :)

    - - - Updated - - -

    Haven't studied it in details, but the fact is that the first and second generation nuclear reactors were basic designs out of necessity and in multiple cases served as multi functional tools to produce radioactive isotopes (for medicine) and weapons grade material for A-bombs. There are various new designs that really are only as power stations, that can "burn" through various materials and are far safer. The only downside is that they've not been built yet so their actual efficiency etc needs to be understood. I've only seen a few vids on the thorium reactors, but they look promising. My personal attitude is that the safest large scale energy production and also the cleanest is nuclear reactors, but they need further work to further increase their safety margins and materials they take. There are for example designs for integral reactors that start from one radioactive compound and the process is repeated many times over in various reactions until the excess material is iron (just too inert to continue) which will be radioactive for a short timeframe, but not excessively long. Also, people have to understand that the tons of material doesn't mean huge piles of material. Uranium is 13x heavier than water so a cubic meter holds 13 tons of it. And that can power a lot of households for quite a while.

    I'd say Mars. All it needs mostly is CO2 into the atmosphere to block in the heat and raise the surface temperature ~10 degrees or so and some oxygen producing plants. Venus is a mess with highly acidic atmosphere and temperatures in excess of 500C. Couldn't even thing how to start there :)

    No clue :D One would have to do some serious math for it and that's far out of my field to answer from the top of my head...

    Universe is not expanding at the speed of light or we'd not see any stars at all. What is expanding is the visible horizon though as in photons from the horizon just about make it to us the first time and they've traveled at the speed of light. The universe itself is expanding at a far slower rate. The Hubble constant for example determines this expansion as 68 km/s / Mpc (68 km/s speed per megaparsec distance to the object we measure so the further out the faster they move away). So the two are not directly related. The causal information between any two points in the universe can interact at the speed of light so if something happens at point A that effect can propagate to point B only at the speed of light. That's why we'd know about our Sun going Nova only ca 8 minutes after the fact (and probably too late as the exploding matter would be hot on the heels of the photons telling us about it).

    Yup, still the best theory there is, all experimental evidence points towards an origin event. However the laws of physics break down ca 10^-43 seconds after epoch so anything before that is something we can't explain and / or observe. Therefore whether there was anything before big bang or what/where/when are hard questions to answer at this point...

    No clue :D Again, this is more of a material science problem than physics problem. From physics point of view it's easy, as is warp drive :) The devil's in the details of the implementation.
     
  17. GSP

    GSP Member

    Joined:
    Dec 28, 2007
    Messages:
    1,996
    Great thread. Thanks Mario. - GSP
     
  18. VolkerP

    VolkerP EU Model S P-37

    Joined:
    Jul 6, 2011
    Messages:
    2,455
    Location:
    Germany
    What type of telescope would we need to detect life on a earth-like planet in, say, 300 light years distance? And, if it is space borne, how many Falcon Heavies to lift it there?
     
  19. Mario Kadastik

    Mario Kadastik Active Member

    Joined:
    Sep 5, 2013
    Messages:
    2,043
    Location:
    Rae, Harjumaa, Estonia
    Well I guess that depends on what you mean under detect life. 300 ly isn't that far so the spacial resolution doesn't have to be too extreme. I'd guess the best bet is finding CO2 and O2 in the atmosphere of a planet and that means we just need to do proper spectroscopy. Now the tough part is that the star will far outshine the planet so measuring spectroscopy of the planet will be tough and if we assume the planet to be in the green zone and similar mass, then it's really tough. So far finding planets is for either super massive (i.e. jupiter like) through wobbling of the star or super close in which case the relative dimming of the star can be noticed in periodic intervals when a planet passes in front of it. Finding smallish planets further out is going to be a really tall order and measuring the spectra of the refracted light through the planets atmosphere is going to be even harder.

    So all-in-all can't say how big exactly, but definitely more precise than anything we've got right now. I know there's a new multi-component satellite with laser guidance that was planned for ~2020 that should have an extremely large effective mirror area (5 satellites with one in the center and four panned out), but not sure if that'll be enough...
     
  20. woof

    woof Model S #P683 Blue 85 kWh

    Joined:
    Apr 30, 2009
    Messages:
    1,149
    Here's a question relevant to recent events.

    A Model S is traveling at highway speeds comes upon a gentle dip in the road, big enough and steep enough so the Model S "bottoms out" as it traverses the dip. Let's assume for argument's sake there is a cast iron man hole and cover at the bottom of the dip, but it's raised up about 1 inch from the bottom. The front of the car clears the man hole, but as it "bottoms out" the man hole impacts the bottom battery plate.

    Assume the Model S plus driver etc. weighs 4800 pounds, the car is traveling at about 65 MPH, and the dip is large/steep enough so the car would just scrape the bottom if the man hole were not there, and the cover sticks out about 1 inch above the road bed.

    What peak force of impact would the man hole cover apply to the bottom of the car? Is it anywhere near the "peak force on the order of 25 tons" Elon Musk says is needed to puncture the armor plate protecting the base of the vehicle? Also, (for extra credit I suppose), what speeds/slopes would be needed to reach 25 tons?

    Thanks in advance!
     

Share This Page