I've been having a couple of thoughts on these subjects today and wanted to get input from the more learned, which means stopping by bit. First to cosmology, and specifically quasars. The consensus theory seems to be that they are supermassive black holes in protogalaxys. If we assume that most of the universe looks like most of the rest of the universe then at some point in history there were objects of this luminosity in our neighborhood. I know that most galaxies are formed around supermassive black holes, but obviously they are not emitting energy like the quasars are. The question becomes "What changed?". My understanding is that black holes don't just go away and while I see how they could have sucked in all the matter nearby, it seems odd that they would slow down their "feeding", and hence emitting, so greatly. The second thought I had was spawned by an article about the follow-on to the LHC, an even bigger and more powerful collider. The question is, is there a physical limit to how powerful of a collider can be built? Is it possible to exceed the energy density of the big bang in such a collider, and if so is it possible we could create particles that have never existed before? Would this be similar to the trans-uranic elements created in nuclear reactors? Thoughts?
There is a physical limit simply on size of the unit, but I'm not sure past that. Interesting questions, I have something to ponder.
I don't think there would be a finite upper limit, but rather an exponential increase in the size and energy required. Looking just at special relativity, to accelerate a particle to c requires dividing by zero. It's impossible. We can get it barely below c, but every small increase in velocity requires a huge increase in energy. I do happen to be formally educated in physics, but I specialize in optics and photonics, and my quantum mechanics professor was a drunk and thus my knowledge on particle physics is uncertain
Actually, black holes evaporate. They emit 'black body radiation' (also known as Hawking Radiation). Anything that emits particles reduces in mass therefore the Hawking Radiation process is also known as Black Hole Evaporation. The rate of evaporation is proportional to the cube of it's mass, so smaller black holes evaporate much quicker. Which, by the way, is why it's no big deal if the LHC creates a black hole. Black holes have been created in particle accelerators and colliders on earth before. They have such a low mass that they evaporate almost instantly.
As for quasars, let me tell you right now that there's some weird **** happening in the universe. First, we don't really know what quasars are --the whole super black hole theory is just a theory. Second, every now and then from almost the horizon of the visible universe (i.e. as far as we can see at the moment because light from further away hasn't reached us yet) there comes this absolutely massive short burst of X-ray radiation. Again, we don't know what is causing that but if it happened anywhere near (as in: within a few million light years) of our galaxy all life on Earth would be radiated to death instantly. Current thinking is that it must be caused by very large stars falling into super black holes, but I think that is unlikely because then we should see such radiation bursts emanating from the center of every galaxy now and then. Or not, because we would not exist. Third, there is something even more absolutely massive just beyond the visible horizon pulling our local galaxy cluster, and a whole bunch of other clusters towards it. We don't know what that is (or they are) either, except that it is (or they are) super-duper big. In theory we could build a collider of infinite size, although in practice it would be limited to the circumference of the Earth. My personal little (and totally unsubstantiated) theory is that every new particle we (think we) find is just one of the same group of particles we already know, except in a higher energy state. Hey, I was right when I predicted (well, guessed really) that Neutrinos have mass (just a very tiny one). I think that this Neutrino mass may be all that missing dark matter we're looking for.
Just saw this which you might find interesting: http://motherboard.tv/2010/7/29/a-brief-history-of-particle-accelerators-video I'm actually working in Switzerland at the moment, the place I'm at designed and built a number of components for the LHC.
My understanding of Hawking radiation is that it's caused when a pair of virtual particles pop into existence and one of them gets sucked down the hole, and it's complimentary anti-particle goes flying off into space. If that's so, then how does it lead to evaporation since as much energy goes in as is emitted? That thought occurred to me as well. We can propel particles, mostly protons as I understand, at higher and higher energies into each other, but as you say the energy involved to get them going that fast climbs exponentially. What if we used something besides protons? Perhaps another, more massive particle. Are there heavier stable particles that could be used in place of the garden variety protons?
It's proportional to the cube of the mass of the black hole. This means that for a very large black hole it will absorb more radiation that it emits. Smaller black holes eventually fall below the level of equilibrium and thus they evaporate at an ever increasing rate. This is due to when a black hole radiates away mass the temperature increases exponentially causing it to radiate away more mass faster. The thinking is that the temperature will keep increasing until the black hole dissolves with a burst of gamma rays. Black holes = mind f**k
Okay, hmmmmmmm.... For the Quasars question, it may just be due to the distances involved... Remember that most Quasars are so bright that they are detected even though they are millions (if not billions) of light years away, so any observations are literally looking well into a much earlier era of the universe. Potentially, we could have a similarly advanced (or not) civilisation in that very universe observing a quasar from the Milky Way from their perspective.... For the LHC+ question... then no, I don't believe we'll ever come close to the conncetration of energy in the Big Bang. Remember that the 'seed' of the Big Bang contained all energy / matter that was required to make the whole universe in a tiny space... Just consider that, we're pinging a few baryons about at ~c ! Cheers, Andy
easy "most of the universe looks like most of the rest of the universe" well most of the universe is empty... but aside from that it tends to look fairly different.... this arm of the galaxy looks quite different from the middle etc.... there hasnt been a black hole round here certainly since the sun was around (or it wouldnt be) Space is big and getting bigger so this is not unexpected galaxies may well be built around supper massive black holes but black holes dont just suck in all the matter any more than the sun has sucked the earth in. There is no limit to the energy of a particle as e=mc2 or add energy particle gains mass which can be infinite hence the impossibility of going faster than light - however you do need to get the energy from somewhere....
You still can't go faster than light, as your energy increases your mass increases proportionally, you can theoretically reach the speed of light but you would need infinite energy to do so.
I heard on a physics documentary not long back that even if you for example built a train that could travel at 4 miles an hour or so below the speed of light, and you then ran on the train - so you'd be going faster than the speed of light relative to the Earth or wherever it was built. Time would actually slow down where you are so the distance you traveled divided by this time would be less than the speed of light - consequently you could in theory travel into the future. This would be due to the time that you experienced would be less than the time someone standing outside the train would experience.
Yup that's the one. Its a good series to watch, although there isn't much of Professor Hawking in it.
No, that's a reasoning error. From your perspective you would simply run down a train. Because the train is moving only fractionally slower than you, you would experience the train in the same way as if, say, it was travelling at a more mundane 150mph (30mph on UK railroads ). Similarly, other passengers on the train would just see a guy running down the train. People observing the train shooting by would see (very briefly) a very compressed image of the train with everyone on board, including the runner, practically frozen in time. In theory the runner would appear more slowed down than the sitting passengers but in practice this difference would be as infinitissimally small as you would observe on a train zipping past at its usual 150mph. Nobody on the train would be travelling into the future. Time inside the train would just pass much slower, so from their point of view they'd be fast-forwarding. But when the train arrives at Alpha Centauri Station, it is still in the present --the passengers are just severely lagging behind. In that respect it is just like British Rail.
The train problem is pretty simple special relativity - it's a relative problem between three moving bodies. I'll whip out my textbook later and dig out the formula for you, but basically you just get a bit closer to c than the train relative to the earth, not past it. The limiting size of a particle accelerator atm is the ring size - we haven't got a tunnel big enough to get much better than the LHC. The problem is that we've nearly reached the energy limits that we can provide for the 2TeV beam energy because as your various particles are accelerated around the ring you get synchrotron radiation of higher and higher energies. Using a heavier particle doesn't alter the problem, because the radiated energy is proportional to mass iirc. It's a simple matter of not having a power grid which can cope with supplying so much energy.
Travelling into the future? I can travel into the future in my sleep. I can travel into the future with one hand tied behind my back. I can travel into the future blindfolded. I am travelling into the future right now. While it's technically true, it's not 'time travel' in the science fiction sense. You're not pressing a button on some wacky steampunk machine and popping up hundreds of years in the future. You don't?! Awww... --Nexxo What's happening is that as you approach the speed of light, time is slowing down. Your watch is moving slower than the clocks on earth. What seems to you like a couple seconds could be years on Earth. The joke is "What if you are driving at the speed of light and turn on your headlights?" Any discussion on this subject is incomplete without first having a discussion on reference frames, both inertial and non-inertial. If you are running at the speed of light, on a train moving the speed of light relative to the earth, you are not running at twice the speed of light relative to the earth. You're running at the speed of light relative to the earth, and at the speed of light relative to the train. It gets weird and confusing, but it somehow works out mathematically if you set up the reference frames correctly and manage to avoid ****ting too many bricks.
