It has been my understanding that Einstein concluded that nothing can be accelerated faster than the speed of light because in order to do that you would need an infinite amount of energy. He did not preclude that particles could have been created in the Big Bang traveling faster than the speed of light. Didn’t scientists theorize such particles, called “tachyons,” but could not either prove or disprove the existence of such matter since they could not interact with the Universe?
No, it’s not just that time appears to be flowing backwards because the light is arriving in the reverse order. Even if you take the signal delay into account, time would still be flowing backwards. Effects would literally happen before causes.
Time isn’t a constant. The flow of time depends on relative movement. If I’m moving relative to you, I’ll measure time differently than you do.
Nothing with mass could be accelerated TO the speed of light since it would require infinite energy. The speed limit of objects with mass is always less than c.
No, you’re not. Einstein was a theory guy. You are evidently a guy who thinks it’s too much trouble to crack a Brian Greene pop sci book, let alone a physics textbook, and yet you still think hey, my opinion is as good as anyone else’s, and who died and made Einstein king?
This is not a case of scientists sitting around a cracker barrel swapping opinions, and the most famous guy wins. Relativity and quantum theory are all laid out in textbooks, from first principles. Countless sophisticated experiments, performed over decades, have confirmed them to the limit of measurement. But since they deal with speeds and sizes that humans don’t directly experience, they contradict “common sense.” Tough. Your PC works anyway.
If you have only average intelligence, you may be simply incapable of understanding them in detail. But if you are really smart (like valedictorian smart), with a good aptitude for math and physics, you can probably become competent in them with six or seven years of full time study. Until then, although you may be entitled to give your opinions about them, nobody should take those opinions seriously.
Sorry, but that’s the way it is.
Actually, a good book can introduce even a schlub like me to the basics of the subject, with no more math than square roots (okay, a little algebra and trig) and in less than a year.
Tensors, on the other hand… (Shudder!)
The basics of special relativity, yes. Competence (i.e., the ability to solve moderately difficult quantitative problems) in GR and QFT, no.
But your point is well taken. Any attempt to actually study science, even at a pre-calc level, is infinitely better than simply saying, “That doesn’t sound right to me.” I don’t see much difference between the OP and a creationist.
And he has a perfect right to be that way. I don’t expect any layman to devote the time and effort it would take to reach that level of competence. What set off my rant was his characterization of himself as a “theory guy,” as opposed (in his mind) to someone who uses math. I’m a (retired) mathematician, and my nephew is a theoretical physicist, and I only wish I could keep up with him.
I didn’t see that as a rant at all, more like a wake up call. I like to sit around and ponder things myself, but I don’t take myself too seriously.
I know a bunch of people have addressed this, but I’d like to try to throw out basically the same answer worded slightly differently.
The wording is the best I can remember from Brian Greene’s The Elegant Universe, and it helped get me over the hump to understanding relativity:
“Physics doesn’t have a good definition of time. It’s just the stuff a clock measures.”
Alas, yep. There is a pretty sharp break between SR and GR. The SR equations are pretty tractable, but the GR equations… Well…
A real mathematician once spent a delightful half hour, giving me the general basis for tensors. I’ve had the usual series of undergraduate calculus, but saw instantly that this was WAY out of my league.
Especially because any decent book on the subject will address the usual objections that newcomers inevitably raise. “What if a ship going .9c fires a torpedo that goes .9c?” Not a stupid question, by any means. But it’s covered in such books as “Relativity Simply Explained” by Martin Gardner.
Yeah…heh…infelicitous phrasing… But, to me, your own comment was the most persuasive one in this entire thread so far: “Countless sophisticated experiments, performed over decades, have confirmed them to the limit of measurement.”
That’s the real killer: this isn’t just “theory.” This is hard-core engineering FACT!
Thank you for replying. I maybe again used the wrong terms. I use the word theory in order to describe postulations I have come up with based upon my limited understanding. I am not and would not put myself on a level with the people who do this for a living, I simply am not very good at math and have never been so all I can really do is look at the work of the masters and try to grasp it and put it in my own words. I have studied the subject extensively though hence why I came to this forum and attempted to ask a somewhat educated question, lol, but apparently I am not looking at it in the right way. I appreciate any help with trying to get my mind around the subject though. I think I have a better idea now of where I was wrong and hopefully I wont ask such silly questions anymore. lol
Hang on, isn’t that the wrong way round?
If you move at a significant percentage of the SOL, your personal time will slow down, won’t it? So, the clock (back on Earth) will seem to run fast, compared to your ship’s time, won’t it?
Nope, the situation is symmetrical. Earth’s clocks are running slow from the ship’s perspective, and the ship’s clocks are running slow from Earth’s perspective.
I think that you’ll do better to read a book about relativity than to try to understand our explanations here. One book that I read recently is How to Teach Relativity to Your Dog by Chad Orzel. Perhaps other posters can recommend other books. The Orzel book simplifies the math as much as possible. I’m sorry, but a certain amount of math is necessary. I think a book-length, popularized text is the easiest way that you’re going to understand what’s going on in relativity.
One of the things that you should understand is that nobody accepted relativity because Einstein was a smart guy and therefore we should all just go along with anything he says. Einstein didn’t do any of the observations that relativity is based on. He didn’t even come up with some earlier equations that sort of accounted for some relativistic effects. The Fitzgerald-Lorentz equation sort of explained some of the effects. What Einstein did was to create an overall theory with special relativity that explained how the world worked in a fairly comprehensible way. He then came up with general relativity, which explained it in an even more comprehensive way.
Relativity is now so thoroughly basic to physics today that it would take a major rehauling of the science if relativity were shown to not be correct. That doesn’t necessarily mean that scientists like it any more than they like quantum mechanics. Einstein didn’t even like some of the implications of quantum mechanics, and he was one of the people who created it. Relativity and quantum mechanics are just so much the heart of physics that dropping them would require completely reformulating it.
That doesn’t mean scientists are adverse to the idea of reformulating their sciences. Some of them are actually thrilled by the idea. That’s why there was so much interest when experimenters at CERN seemed to find particles that traveled slightly faster than light. (It’s now seems that it was a result of bad measurements.) If a scientist proposed a theory that reformulated physics and took account of measurements that showed problems with old formulations, they know that they would become world-famous.
It’s possible that physics will require being completely rehauled a few more times. It’s happened twice before. There was a physical theory that had existed since the time of the ancient Greeks that Newton reformulated because of the observations of Copernicus, Kepler, Galileo, et al. Newtonian physics was then rehauled by Einstein and others with the theories of relativity and quantum mechanics because of further troublesome observations. There are current ways in which physics doesn’t quite hang together (including some contrary implications of relativity and quantum mechanics) that might mean that there will be more reformulations.
If this happens, it does not mean that “Einstein was wrong” (as some news stories about the CERN experiments claimed). A new theory would merely recast physics in a new framework that explained things better. Similarly, Einstein’s theories did not mean that “Newton was wrong.” He merely recast the laws of physics in a better form than Newton. Newton’s theories did not mean that “the ancient Greeks were wrong.” Newton has new observations to take account of that allowed him to recast physics. Einstein had newer observations to take account of that allowe him to again recast it. Science is not about saying, “Nyaah, nyaah, you’re wrong and I’m right.” It’s about understanding all the observations done so far and explaining them in the simplest, most comprehensive way.
Currently, but barbitu8 makes a good point when he mentions tachyons. For a brief period in the 60s scientists accepted that maybe such a thing could exist, precisely because prior to the Big Bang we have no knowledge of what physical state or physical laws governed the proto-universe. However we suspect they were not at all the same as they are now, even the nature of matter was probably different.
However not more than a few years after tachyons were first theorized it seems like physicists came up with a lot of good theoretical reasons why they would not actually exist, and there have been some experiments to try and detect them (none have found any, of course.)
But barbitu8 is correct at least in thinking that prior to the Big Bang different rules applied. As far as we know that’s quite likely true, we have no basis to conclude what things were like, even simulating the universe during the Planck Epoch doesn’t actually give us a glimmer of an idea as to what the universe was like prior to the bang.
Did I miss some qualifier in his response? I don’t think he was talking about the situation at the big bang, much less prior to it (a statement that doesn’t make any sense since there was no time before the big bang).
It seemed to me he was making a statement of the current state of affairs.
Yeah, I misread what barbitu8 had said. I thought he was postulating about something created prior to the Big Bang that could somehow have persisted in our universe until today.
And how doesn’t it make sense to talk about “prior to the big bang?” Yes, the big bang is the exact moment when the universe as we know it begins, and you couldn’t observe anything from before then, but heavy weight physicists speculate about the origins of the initial state and the exact composition and physical laws in that initial state all the time.
Yes, for beings like us in this universe time began with the bang, but there is no reason you can’t use the phrase “before the Big Bang.”
Doesn’t “before the big bang” imply a period of time?
Yes, but if you want to talk about any state prior to the Planck Epoch it becomes difficult to avoid usage of the phrase “before the Big Bang.” There is no scientific consensus on anything prior to the Planck Epoch of which I am aware (and given my non-scientists understanding it is essentially impossible from our perspective in this universe to know anything before that moment except perhaps from exotic types of simulations far beyond anything we can do today.)
One point of view, and Hawking is the biggest proponent, is that you basically had a singularity “prior” to the Big Bang, a singularity of both space and time. Hawking would go on to describe it basically using the exact words you are, that because of the nature of it there is no real “time” before the Big Bang. There is a state that was and then the Big Bang, but that state had no time and no space, just finite space with no boundary and no time. That’s Hawking’s view anyway, some theories posit non-singularity initial states.
But either way to even talk about the initial state and even if you use Hawking’s terminology that time begins with the Big Bang it is difficult to avoid saying “prior to” the Big Bang, and even Hawking does it sometimes.
It becomes especially difficult when you’re trying to explore multiverse theories or brane cosmology theories. Under those theories you can be 100% on board with time beginning at the instant of the big bang within this universe, but you still have to be able to speculate on interactions of things. For example if you’re exploring brane cosmology and you’re one who believes our universe was caused by a collision of branes you would by necessity need to talk about pre-collision events in the bulk which is hard to express without saying “things happening before the Big Bang.” Even though yes, even under such a theory as that time as we know it still begins at the Big Bang.
Well, yes and no… Time, as we experience is, is part of space-time, which does not exist outside of our cosmos. Speaking of “Before the Big Bang” is a little like asking what the “race-time” was before the start of the Indianapolis 500. Before the race starts, there is no race-time. Before the Big Bang, there is no space-time.
Is there a larger meta-cosmos, in which our cosmos is embedded? Might be. Did some external event cause the Big Bang? Might have. Wouldn’t that constitute being “before the Big Bang?” Yes…but only as measured in some sort of meta-time, some higher-dimensional time-like thing. It isn’t “time as we know it.”
(A man once saw a flock of grebes and said to his wife, “They’re ducks…but not as we know them.”)
I feel like I didn’t even post my response to Kinthalis at all, because I basically said nothing that contradicts what you are saying. Within existence as we know it, time only has any meaning once the Big Bang happens. But there is still an initial state which physicists the world over speculate on and while it is akin to talking about the “race-time” of the Indy 500 before the start, it becomes linguistically difficult to speculate on pre-start events without dropping into that sort of word usage.
No one is disputing that “our universe time” or “time as we know it” or “time that has any meaning in our conception of time” began at the moment of the Big Bang, but there was a big bang which was a real event of “creation” as far as this universe is concerned. Pretty much every theory of any repute agrees that the initial state would have essentially been extremely finite and even possibly a singularity, and that either way all of general relativity and its equations break down in such a state. Whatever it was, it was basically incompatible with physical reality and existence as we understand it.
I don’t know that Hawking is a proponent of any specific brane cosmology or multiverse theory but I know he has said there are possibly many universes essentially created from nothing and that because we are living creatures we obviously would only exist in a universe where life was possible. He goes on to suggest there could be other universes where life as we understand it simply could not exist, even things like matter and other universal building blocks of our existence in fact may not exist or may be so foreign as to be incomprehensible. Time as it matters to us might not even exist.
Time is not a universal, so there probably couldn’t be any sort of “metatime” either. But there are obviously changing states. If for example brane cosmology is true and colliding branes explain universe creation then obviously the branes are engaged in some sort of motion or alternating of state. But quite possibly time only has any meaning inside the universes created by these collisions. The theories on brane cosmology I have read have speculated brane-to-brane collisions would be “infrequent” from the perspective from inside a brane but that in the “bulk” time as a concept probably doesn’t exist. As far as we know all of the constants of our universe (including c), and all the field energies could possibly not exist at all, or could all exist in some strange collusive manner that defies anything that we could express in terms that would make sense because our thinking is irrevocably locked into thinking of things in the context of the only reality we know.
Most likely of course if there is any sort of “external multiverse” it is wholly unknowable and inconceivable.