Does relativity have any day to day life applications?

[goodabouthood]

Can you use any of these theories in daily life? Or how can you?

 

[mrspeedybob]

Depends on your definition of "use" and also on who you are and what you do.

If by "use" you mean that relativistic effects affect you or that you can directly observe or use the effects then the answer is yes.

If by "use" you mean that an understanding of relativistic effects will help you achieve a goal then the answer depends on who you are and what you do. If you don't already know then you are probably a carpenter or attorney or something besides an engineer or scientist. In that case the answer is no. If you were an engineer or scientist then you would already know that the answer was yes.

As for how, you need to pick your definition of "use" before I can answer that.

 

[HallsofIvy]

Every gps unit has to take relativity into consideration.

 

[phyzguy]

Magnetic fields exist because of relativity. So just about every electric machine you use depends on it.

 

[Naty1]

It depends on your 'daily life".

Billions upon billions of people live and die without knowing anything about relativity. The very successful Roman legions didn't need it to conquer much of the known world. If a lion is chasing you on a savannah, relativity is a rather unimportant theory. And you don't need to know about it to watch TV or make popcorn.

On the other hand, if you were thinking about trying to define absolute rest, or how fast information can be transmitted, or how relative speed or gravitational potential affect the passage of time, or how acceleration and gravity are similar, it could save you many years of effort.

 

[pervect]

There are also a lot of things you use , without thinking about it, that were designed by people who did understand relativity and used the theory of relativity when they were doing design. But you don't need to understand relativity to push the off/on switch.

IT's rather interesting though, that people who claim to not believe in relativity don't usually seem to have any problem pushing the off on switch. They simultaneously claim the people who designed the device in question were wrong, while using the device in question (say, GPS) as if it were trustworthy, rather than regarding it as some faulty ill-designed bridge, liable to malfunction or fall down at any minute.

 

[ghwellsjr]

Yes, and we are fortunate to have different ways to know what time it is (and therefore what day it is) whether that be by getting time from a television, radio or internet broadcast, or from our cell phone, or from a GPS receiver, or even from a clock plugged into the wall, without the experts taking care of the details, it couldn't be done without them understanding relativity.

 

[LGram16]

Unless you are amish or an amazonian indigenous tribe the yes.

 

[mrspeedybob]

Unless you are amish or an amazonian indigenous tribe the yes.

By that definition even they depend on reletivity. Reletivity provides the fundamental speed limit of causality. Without this limit everything that has ever or will ever happen would have happened all at once. The universe would have been over at the big bang.

 

[juanrga]

Can you use any of these theories in daily life? Or how can you?

Gold glows because of relativity

 

[Prof Niemand]

TVs aren't built using CRTs anymore, but when they were, the electrons in the picture tube were accelerated to a sufficient percentage of the speed of light that the design engineers had to take relativistic effects into account, to ensure that the electron would hit the intended spot on the screen.

 

[homeomorphic]

Magnetic fields exist because of relativity. So just about every electric machine you use depends on it.

Yeah, but the engineers didn't necessarily take it into account. It might help their understanding of electromagnetism, but that's it.

The only major application I'm aware of for general relativity is GPS. Also, the orbits of bodies moving around the sun will have slight relativistic corrections, so I imagine that ought to have some practical significance for predicting the trajectories of asteroids and comets. That's rather important, since it is inevitable that one day the Earth will be hit by a big one, and we had better know as soon as possible.

With special relativity, it's a different story. Lots of applications. One example would be nuclear physics. Nuclear power, nuclear weapons. Even in chemistry, you have to take relativity into account. Molecules may be moving very fast if the temperature is high. That means things have slightly more mass as they heat up. I'm sure there are many more. It's pretty far-reaching, actually, even though it's probably relatively rare overall in engineering that you can't get away with classical approximations.

A full understanding of spin in quantum mechanics depends on relativity, and many other very fundamental things. The relativistic view of quantum mechanics is, of course, much more complete. And, even from the very beginning of quantum mechanics, starting with de Broglie, relativity played a role.

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/debrog2.html

So, you might be able to argue that any application of quantum mechanics is an application of relativity in that sense.

 

[LGram16]

TVs aren't built using CRTs anymore, but when they were, the electrons in the picture tube were accelerated to a sufficient percentage of the speed of light that the design engineers had to take relativistic effects into account, to ensure that the electron would hit the intended spot on the screen.

Hm. Didn't know that. Sounds way to overcomplicated compared to now, although technology at the time of CRT TVs didn't allow for that, but still.

 

[juanrga]

With special relativity, it's a different story. Lots of applications. One example would be nuclear physics. Nuclear power, nuclear weapons. Even in chemistry, you have to take relativity into account. Molecules may be moving very fast if the temperature is high. That means things have slightly more mass as they heat up. I'm sure there are many more. It's pretty far-reaching, actually, even though it's probably relatively rare overall in engineering that you can't get away with classical approximations.

The main reason which special relativity is taken into consideration in chemistry is not because molecules move very fast at very high temperatures (probably most molecules would dissociate before being accelerated to speeds comparable to that of light), but because inner electrons move very fast in heavy nuclei.

In #10 I said that gold glows because of relativity; this is a typical relativistic quantum chemical effect.

 

[homeomorphic]

The main reason which special relativity is taken into consideration in chemistry is not because molecules move very fast at very high temperatures (probably most molecules would dissociate before being accelerated to speeds comparable to that of light), but because inner electrons move very fast in heavy nuclei.

I may have said "very" fast, but it would be a mistake to interpret that as saying that they move near light speed. I didn't make that claim. The claim was just that they move faster, hence they have higher relativistic "mass".

If I am wrong about this, it's my chemistry prof's fault, since this is essentially exactly what he told us. But at least I was right that relativity has a role in chemistry.

 

[juanrga]

I may have said "very" fast, but it would be a mistake to interpret that as saying that they move near light speed. I didn't make that claim. The claim was just that they move faster, hence they have higher relativistic "mass".

If I am wrong about this, it's my chemistry prof's fault, since this is essentially exactly what he told us. But at least I was right that relativity has a role in chemistry.

Well, by «speeds comparable to that of light» I did not mean «near light speed», but speeds v<c for which special relativistic effects cannot be ignored. Notice that for v=0.05c typical terms as 1-(v/c)² = 0.9975 ≠ 1 and relativistic corrections are relevant by the needed quantum chemical precision {*}

As said, it is not needed to accelerate molecules to observe relativistic effects. They are already observed in the inner electrons of heavy atoms (as those of Gold) at rest.

Some scientists continue using the old concept of relativistic mass, which varies with speed; however, the tendency in modern relativistic physics is to use invariant mass m≠m(v)

{*} For high-precision computation, special relativity is not enough and QCD corrections are needed.

 

[chrisbaird]

Relativity seriously impacts my daily life. Without it, I would not have as many interesting educational videos to watch.

 

[homeomorphic]

Well, by «speeds comparable to that of light» I did not mean «near light speed», but speeds v<c for which special relativistic effects cannot be ignored. Notice that for v=0.05c typical terms as 1-(v/c)2 = 0.9975 ≠ 1 and relativistic corrections are relevant by the needed quantum chemical precision {*}

Well, I was more or less aware of that. I wasn't saying it's normally needed in chemistry. It was my impression that it could come up, not that it's something that's normally necessary, and I was well aware it wouldn't be relevant in the vast majority of chemical situations.

Somehow, I'm lazy about getting a sense for exact numbers and quantities, though. I don't know what kind of molecular velocities would ever come up normally in chemistry. But, let's say your gamma is 1.000001. If you have 1000 kilograms of stuff move at a speed giving you that gamma, you get that the relativistic mass increases by 1 gram. I'm no chemist, but it's conceivable that if you wanted a lot of precision in a high temperature kind of thing, maybe you would care. But I don't know.

As said, it is not needed to accelerate molecules to observe relativistic effects. They are already observed in the inner electrons of heavy atoms (as those of Gold) at rest.

Ok.

Some scientists continue using the old concept of relativistic mass, which varies with speed; however, the tendency in modern relativistic physics is to use invariant mass m≠m(v)

Actually, I was recently won over to the side of the invariant mass just a few days ago because of another thread here, the point being that the invariant mass is what is relevant for gravitational purposes. Up until then, I was never really sure which to use. I still think it helps to think of the other mass as an "apparent mass" in some situations.

 

[homeomorphic]

Relativity seriously impacts my daily life. Without it, I would not have as many interesting educational videos to watch.

Good one. I don't know about videos, but any theory that is interesting enough and fun to learn about has a daily life application of just being fun in its own right.

I can even impress women with my knowledge of physics on occasion. I told an ex about time dilation once and she seemed pretty surprised. I don't even know if she believed me or not. Short-lived relationship. Not much opportunity to follow up on it.

 

[juanrga]

Well, I was more or less aware of that. I wasn't saying it's normally needed in chemistry. It was my impression that it could come up, not that it's something that's normally necessary, and I was well aware it wouldn't be relevant in the vast majority of chemical situations.

Somehow, I'm lazy about getting a sense for exact numbers and quantities, though. I don't know what kind of molecular velocities would ever come up normally in chemistry. But, let's say your gamma is 1.000001. If you have 1000 kilograms of stuff move at a speed giving you that gamma, you get that the relativistic mass increases by 1 gram. I'm no chemist, but it's conceivable that if you wanted a lot of precision in a high temperature kind of thing, maybe you would care. But I don't know.

I have two questions:

(i) How many precision you think that we can measure mass? Hint look to the display of a modern high precision balance

(ii) Did you read the note {*} in the message that you are replying?

Actually, I was recently won over to the side of the invariant mass just a few days ago because of another thread here, the point being that the invariant mass is what is relevant for gravitational purposes. Up until then, I was never really sure which to use. I still think it helps to think of the other mass as an "apparent mass" in some situations.

It is not true that the invariant mass «is relevant for gravitational purposes» only. When solving the Dirac equation in relativistic quantum chemistry and atomic physics, you must input the invariant mass of the electron.

 

[epenguin]

The best examples would be where there is a contrast between something with relativity effects and a similar example where they are weaker or negligible.

I am told (and must follow up sometime ) that gold has the colour it has, different from silver, because of a relativistic effect. This has been known for some time. But more recent - I do not know how definitive, but for our puposes it suffices that it is reasonable, that calculations support it - the working of lead batteries. Those are certainly everyday."To put it bluntly, classical chemical theory predicts that cars should not start in the morning.

Which is where Einstein comes in. For, according to Dr Pyykko’s calculations, relativity explains why tin batteries do not work, but lead ones do."

http://www.economist.com/node/17899724

 

[homeomorphic]

I have two questions:

(i) How many precision you think that we can measure mass? Hint look to the display of a modern high precision balance
(ii) Did you read the note {*} in the message that you are replying?

Originally Posted by homeomorphic View Post

Look, I already dropped the issue. Was just explaining what I was thinking originally. It was just that it came up in my chemistry class. I didn't think it through enough. So, your questions are not relevant.

It is not true that the invariant mass «is relevant for gravitational purposes» only. When solving the Dirac equation in relativistic quantum chemistry and atomic physics, you must input the invariant mass of the electron.

Did I SAY it was relevant for gravitational purposes only?

 

[juanrga]

It is not true that the invariant mass «is relevant for gravitational purposes» only. When solving the Dirac equation in relativistic quantum chemistry and atomic physics, you must input the invariant mass of the electron.

Did I SAY it was relevant for gravitational purposes only?

What you said is enclosed between guillemots «», the word only is outside of them; therefore, the answer must be obvious.

 

[joris_pixie]

:) well a part of your electricity is probably made by nuclear power.
The idea of nuclear power comes from relativity

Also the atom bombs you explode in your garden

 

[bcrowell]

P. 5 of this paper http://arxiv.org/abs/gr-qc/0506075 attempts comprehensive list of applications, but most of them are not applications in daily life. Nuclear power and nuclear weapons don't really qualify IMO because all forms of energy (e.g., chemical energy in gunpowder) are equivalent to mass, and relativistic effects in low-energy nuclear structure are basically things you don't worry about because you use nonrelativistic models in which the parameters are adjusted in ways that end up taking care of the small relativistic effects. You could argue that the abundances of the elements are something that has a big effect in daily life, and that you need relativity to understand them properly (e.g., the lightest ones are from big-bang nucleosynthesis).

 

[michelcolman]

TVs aren't built using CRTs anymore, but when they were, the electrons in the picture tube were accelerated to a sufficient percentage of the speed of light that the design engineers had to take relativistic effects into account, to ensure that the electron would hit the intended spot on the screen.

Either that, or they just fiddled with the dials until the picture looked right. I'm not an expert on the subject, but I think that's more likely. Especially since the CRT was invented in 1897...

In more recent models, the electronics managed the fine-tuning but I would bet they did it by measuring the result and adjusting the parameters to reach the intended result, without any relativistic formulas. Obviously, if you would look at what those parameters turned out to be, they would confirm relativity. But you don't need relativity to set them up.