# B Relativity in everyday use

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1. May 9, 2016

### Stephanus

Dear PF Forum,
I'd like to have some opinions here.
A friend of mine says, "From Newton , we got car, airplane, rocket, etc. From Einstein, we got sci fi movies".

Okayy, forget him
Now, what I want to know is, what relativity has direct impact in our everyday life?
There are two things that I know
1. GPS. Is GPS really depend on relativity? I heard that the clock synchronization is not trivia.
2. Nuclear energy.
Are there anything else?
Air conditioner?
Television?
Electric shaver?
Just any everyday devices, not just
"Oh, you see that rocket. Its clock is slowing down by half of our clock, so it rocket must have travelled at 0.866c"

Not that I like Isaac more then Albert.
I know that Einstein got noble price not by relativity but by photoelectric. I'm not asking what photoelectric has to do with our everyday life, but what relativity especially has got to do with our everyday life? (And by that I don't mean Special Relativity ).

2. May 9, 2016

### vanhees71

Everything related to electromagnetism, including optics, is ruled by Maxwell's equations and thus is relativistic. It's the paradigmatic example for a relativistic field theory.

3. May 9, 2016

### A.T.

Still worth noting that human carrying car, airplane, rocket were introduced much longer after Newton, than has passed now since Einstein.

4. May 9, 2016

### Stephanus

Okayyy,
Ford, 1908?
Kittyhawk, 1903.
V2, 1940s, if we can call V2 a rocket, which it was although Goddard had preceded it.
Relativity, 1905
GR, 1915.
Yeah, I've watched Derek Muller in Youtube, he explains that magnetism in a wire is caused by relativity, because there are more electron in one side of the wire, because of length contraction? Even if I haven't fully understood what he taught.
Thanks.

5. May 9, 2016

### Paul Colby

Both relativities are required in GPS systems. Corrections are made due to relative satellite speed (special relativity) and due to gravitational effects (general relativity).

6. May 9, 2016

### Stephanus

Yes, I have read that. But is the correction significantly necessary?

7. May 9, 2016

8. May 9, 2016

### Paul Colby

It certainly is if you want to choose which restroom stall to hit with your ICBM or measure continental drift to centimeter accuracy. How far off would you be for each correction I don't know off hand. For GR the clock rate correction has to be on the order of one part in $10^6$ which is the rough order of magnitude of the metric deviation at sea level. That sounds significant to me.

9. May 9, 2016

### Stephanus

Centimeter? I thought it would be kilometers accuracy that is corrected by the clock synchronization.
But centimeter is good for continental drift.
Hell, you can miss 100 meters from ground zero cafe with a 15 kilo ton bomb in still destroyed capitol hill.
[Edit: And it can still destroy Capitol Hill]

Last edited: May 9, 2016
10. May 9, 2016

### Paul Colby

Centimeter accuracy takes special antennas and likely GPS hardware. One sees these 12"ish diameter half dome things on tripods along the side of the freeways out here in CA. They are real concerned with ground movement because the state is so faulty.

[Mentor's note: A bit of entertaining but off-topic political snark has been removed from this post]

Last edited by a moderator: May 9, 2016
11. May 9, 2016

### mathman

Lasers are based on stimulated emission, first described by Einstein (1905?).

12. May 9, 2016

### PAllen

This was based on Einsein's work as a quantum pioneer, very little to do with relativity (yes, EM radiation is involved, but the distinctive feature is quantum. Einstein remained a significant contributor to quantum theory (despite misgivings about the way it was formulated) till about 1935.

13. May 9, 2016

### pervect

Staff Emeritus
Well, I'd like to grouse a bit about the original observations.

While we can certainly understand cars, airplanes, etc from Newtonian point of view, it doesn't "give them to us". And there are plenty of relativistic phenomenon that are easily observable with significant effects that are not science fiction - man made (such as various particle accelerators) and otherwise. And that's not counting the sensitivity of modern instruments, which can detect relativistic effects in everyday motion - it's not really exotic anymore.

As far as practical applications of relativity, our standard of distance, the meter, is and has been based on relativity for some time now. For details, just look at the SI definition of the meter.

End grousing, it's probably pointless...

14. May 9, 2016

### Stephanus

Yes @pervect
I just want to tell it to his face, but it seemed that I can't recall anything other than GPS then. And as I typed this thread something just came up on my mind. "Nuclear power".
And as @A.T. and you say. Rocket and car were introduced 200 years after gravity.
Btw, it's only 35 years from SR (1905) to Manhattan Project (1940) and 40 years to Little Boy (1945).

15. May 13, 2016

### CalcNerd

Well Stephanus whole areas of technology are owed to Einstein.

One such item IS the Air Conditioner, so to speak. Einstein invented a refrigerator.

https://en.wikipedia.org/wiki/Einstein_refrigerator

He also won his Noble prize for his explanation of the photovoltaic effect (solar cells).

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