We can’t speculate?
Let’s say I am getting reaaaaalllly close to the speed of light. We know length contracts the faster I go. Things in front of me seem to get closer. As I approach lightspeed is the universe pulling in towards a point or line or plane (or something else)?
Should be approaching a point the faster you go. A 2D line doesn’t really make sense.
And it’ll be weird. As you approach c, you should start being able to see things “behind” you.
I thought it would be a point too but then if length only contracts in the direction of travel isn’t the universe that is at 90 degree angles to my forward motion completely “uncompressed” (for lack of a better word)? So, above and below and to my right and left the universe is still sprawled out?
(I’m really asking…just walking through it in my head)
Can you explain why GPS works if real-world technicians don’t read that article but continue to rely upon the answers given by relativity?
Could you then supply equations that answer my earlier question about faster-than-light travel?
Doing some Googling, I found that the contents of this post are from Tom’s Problems with Relativity. It is also remarkably free of equations explaining his alternative to relativity.
They’re all derived from the same formulas. The decrease in length and dilation of time are derived correctly, while the increase in mass is derived incorrectly.
This is all correct. The mistake in saying that mass increases is in attaching that gamma to the mass, and saying that gamma*m_0 is the “true relativistic mass”, instead of much more logically attaching the gamma to the v, to form the “proper velocity”. Which, coincidentally, is the actual topic of this thread.
Kind of hard to describe this, because we have to break something. In reality, it’ll look really, really white to us (simultaneously literally cooking us) because all that light in front of us would enter our eyeballs (and the rest of us) instantly.
We wouldn’t ‘see’ anything in the conventional sense. But say we did. How does rain look as it hits your windshield as you drive? It seems to come at an angle, even if, from the outside, it may look like it’s falling straight down. The same thing is going to happen to an extreme degree from all directions.
As you get close to ‘c’, you should see everything in front of you getting ‘smaller’ to a point in front of you but the bits that aren’t directly in front in the point will ‘smear’ and ‘stretch’ to fill the rest of your visual field (again, ignoring that it will go super white and blind you long before this). At the limit, the ‘stretch’ is infinite and everything in front goes down to that point in front of you. So, sort of a blindingly white pointy plane? But not something we can describe in a conventional Euclidean sense.
I’ll reiterate the point I made above, but expand things a bit.
There is a lot of lies to children in popular understanding of relativity. Some this comes to bite us when things like relativistic mass is talked about. You get multiple conversations, some talking about relativistic mass, some talking about Lorentz factors. We do need to fess up that there was realignment in the conventional way we talk about special relativity, and when one confuses things from the relativistic mass era to the more modern era of describing special relativity it gets confusing. It isn’t that the idea of relativistic mass is wrong, it is now generally considered not to be the most helpful way of describing what happens. We need to be consistent.
The average light speed sceptic (and I include tomh4040) is coming into these conversations not actually understanding what special relativity is. There is a mish-mash of misunderstood pop-science and confused ideas about what Einstein said. Further there is a misunderstanding about what mathematics is. It isn’t arithmetic.
It isn’t clear to me that you ever get anywhere playing whack a mole with these sorts arguments, as you never make enough progress in common understanding, as the basic definitions of what is being discussed are too ill defined.
Perhaps tomh4040 could usefully explain what he thinks special relativity is, and when everyone agrees that he actually understands what it is, he might explain where the problem is. Because right now it is clear he doesn’t know what it is. There is just the usual mess of pop-science and lies to children and the residue of the changes in nomenclature used in physics that confuses things.
Of course the math doesn’t care, since the result is the same. But for my own edification, wouldn’t the appropriate parameter to which one would conceptually attach the gamma factor (Lorentz factor) depend on one’s frame of reference?
If you’re in a fast-moving spaceship, proper velocity is something you actually observe and can measure. You also observe that mass remains constant.
But if you’re in a different frame of reference, whatever v you observe is always going to be less than c, and if the same amount of thrust continues to be applied, you observe c being approached asymptotically. Thus from that frame of reference, it appears as though the Lorentz factor is being applied to mass, since the spaceship acts as if its inertial mass is increasing. I think the mistake that is often made is in thinking that the spaceship’s rest mass has increased in some magical way.
From a non-accelerating frame of reference, as you watch this ship with its unobtanium drive thrust away constantly, you would measure the thrust decreasing. On the ship, the thrust stays the same, but from your non-accelerating observer, that thrust is coming over a longer period of time, so is becoming less powerful.
The ship appears to slow its acceleration not because it becomes more massive, but because the thrust decreases.
That’s a good counterpoint to that particular example, and shows that there are often equivalent ways of conceptualizing the same thing. But what about particles like protons in a particle accelerator? They’re propelled by oscillating electric fields. Their proper velocity is something we can infer and calculate, but not directly observe. What we observe, instead, is that as their energy level increases, they asymptotically approach c, and when they collide with another particle, their momentum and kinetic energy are observed to be much higher than Newtonian physics would predict. What other conclusion is there, from our particular frame of reference, other than that their inertial mass has increased?
It just struck me as particularly apt in this context.
On the best days, answering questions from these sorts helps me clarify my own thinking, so I understand things better (and perhaps can explain them better to someone genuinely interested in learning the basics).
On the worse days - deep frustration.
The Straight Dope has been fighting ignorance since 1973. Occasionally, ignorance wins.
Andy L. I know what perpendicular means, but in the picture you sent, the two rulers were not set one perpendicular to the other, they were at about 45 degrees. So my statement stands. I even did it on my PC screen with your rulers. I drew my lines parallel, as that is the only way which makes any sense. Labeling the rulers A and B for clarity, A2 goes to B3 and B4 goes to A3 .
The case which Einstein did not consider (you can check this in his work) is the reciprocal. IE, he looked at IFR2 and calculated that it’s clock ran slower that IFR1’s, but he did not did do the same calculation for IFR1. If he had, he would have seen the contradiction.
Einstein said that these effects are real, not appearances. That statement in no way contradicts the paragraph above.
Tom Hollings
Wolfpup, I have pointed out the contradictions. SRT may well be a mathematically sound theory, but that is all. The “real world” can always be described by mathematics (what is true in the real world can be expressed mathematically). That statement cannot however, be turned round. What is true mathematically does not always correspond to the real world.
Tom Hollings
Would you be prepared to provide a citation for this. Not a paraphrase or someone else saying he said this, but a citation to words actually written by Einstein?
RitterSport, you are nearly correct. Think about what have just written. “It’s done by taking relativity into account and adjusting the time on board.” This refers to the satellites. Then you agree that the time at the receiver is not used, but that time at the satellites is used. Therefore whether the satellites’ clocks run fast or slow would not make any difference. That is exactly what that website says.
Sure. The problem is that it is you that is providing a mathematical structure that doesn’t fit the real world as measured experimentally. The mathematics Einstein provided has been validated experimentally uncounted numbers of times, and has never yet been proven wanting.
If you believe that acceleration to faster than light speeds is possible you need to provide a coherent theory that isn’t contradicted by experiment. Vigorous assertion does not count. Your theory needs to be predictive, not simply qualitative. If we put numbers from an experiment into your theory, the as measured answers should pop out. Einstein’s does? Minimally you need to match that.
You might like to simply start with the Michelson-Morley experiment. If you can’t manage that you are already a non-starter.
Attention to detail is important if you’re going to criticise something (actually this might be the entirety of your problem with relativity). Nobody except you said anything about the rulers being perpendicular to one another. Here’s what @Andy_L actually said:
And here’s what (I think) @Andy_L meant
https://1drv.ms/u/s!Ar4eOUAx-yGwiKtqf8nzHsyEnXT_Vg
So, you agree that the clocks on board the satellites are adjusted. The are adjusted so that they match each other and the time in Colorado (I believe). Why do you think that is? Why do the satellite clocks have to be adjusted?