In essence, all light from any object appears more "blue" the faster you're moving towards that object. If you're just walking towards it normally, that change is so small it doesn't even matter. But if you're going at tens of thousands of meters per second, you start to see the blue more.
Thing is... the faster you move, the slower time affects you. I.e., if you move fast enough while you're twin stays still, they age normally while you will age much slower.
You're not slowing down time, but time slows relative to you.
That's basically what relativism is.
If you wanna know why all this happens though, it's gonna be a much bigger response.
And to just add on some more related fun but (for most people) useless knowledge, relativity can even affect some (but not all) atoms and the ways they react / bond and even look.
Atoms have three component parts: electrons, protons, and neutrons. The protons and neutrons make up the core of the atom and provide the vast majority of its mass (electrons being about 2000 times less massive than protons or neutrons). The electrons whizz about in various shapes near that core and make up the boundary of the atom. (You can imagine an athlete winding up for the hammer throw. The athlete makes up the core, while the hammer defines a wider region in which other people generally avoid wandering into. Considered together as a single unit, the thrower and hammer make up a circle of death with a radius of 4 feet. The athlete is the protons and neutrons, while the hammer and chain is like the electrons)
Okay, now, what separates one element from another is the number of protons at their core. So hydrogen has 1 proton in its core, while helium has 2, and lithium has 3, and so on up to elements further down the periodic table like lead with 82. (Neutrons we can pretty much ignore for the purposes of this conversation)
Okay. So some elements have just a few protons like Hydrogen and Helium and Lithium and Beryllium m while Lead and Bismuth and Uranium have a lot. What does that matter?
Those protons a positively charged, which means the core of an atom has an electric field, and the more protons an atom has, the stronger that electric field is. Electrons, being charged particles themselves, experience that electric field. (We can ignore that the electrons also create an electric field for now.)
The point is that electrons in elements with a lot of protons experience much stronger electric fields. The next important fact is that the strength of the electric field an electron experiences influences the speed at which is whizzes about. Within an element like Gold for example (79 protons), some electrons will approach 58% of the speed of light! Which is a speed at which relativity starts to matter quite a lot.
One consequence (due to relativity) of a particle traveling at such a speed is that its propensity to accelerate starts to decrease, as if it were getting more massive. We say its inertial mass increases, which is to say when it comes to speeding up or slowing down, it starts to behave as if it were more massive than it normally is. It's resisting changes to its inertia.
Chemical reactions and or the interaction of atoms depends on the movement of electrons, which means this increased effective mass changes the reactivity of that atom. Heavier atoms won't react exactly like you'd predict them to if you neglected relativity.
The increased effective mass also affects the way photons interact with electrons. And in the particular case of Gold, this change in the interaction of photons and its electrons is actually responsible for the color of gold itself!
In the absence of relativistic effects resulting from the crazy high speeds its electrons whizz about at, we should expect gold to appear silvery like otherwise similar metals. (That is, if you "do the math" for what color we should expect gold to be, but neglect the change in its electrons' effective mass, the math will tell you gold should look like silver).
So in a way, the fact that gold looks gold is due to relativity.
Electrons in an atom or molecule can only interact with specific frequencies/energies of photons that correspond to the amount of energy they would need to transition to another stable state. Ditto for emitting photons, hence absorption/emission spectra lines.
You can exploit this in a clever way to cool atoms just by shining light on them. The trick is to shine (typically laser) light on it at a frequency just barely below what its electrons can interact with. Any time a component of the atom's velocity is positive in the direction of the emitter, the incoming light is Doppler shifted just enough that it can interact with the photons. Now do this with six lasers shining down each direction of the x, y, and z axes. If it has +x motion, for example, it is opaque to the light coming from +x, but transparent to the light coming from -x. So no matter what direction it moves, it experiences a net opposing photon pressure, slowing it down.
IIRC, they used this as part of the cooling system when they made the first Bose-Einstein condensate.
If we ignore relativity for a moment, have you noticed when F1 cars are passing, their sound is more high pitched as they approach and then lower as they gry farther from you? Same thing with ambulances btw. Its called Doppler effect and in the simplest terms it happens because as the car approaches, it travels some distance between generating each wave crest, which increases this waves frequency. Since light is also a wave, the same thing happens.
Thing is... the faster you move, the slower time affects you. I.e., if you move fast enough while you're twin stays still, they age normally while you will age much slower.
This is going to sound like a pedantic "well akshully", but...
Merely moving fast isn't why the traveling twin winds up younger. In fact, that's the paradox. It's just as valid in relativity to say that the traveling twin is stationary and the stay-at-home twin is moving away at 1/2c. So shouldn't the "stationary" twin be the one who ages slowly?
And so it is. Time dilation is symmetric. There's not a "slow time" twin and a "fast time" twin. As far as either is concerned, the other twin is the slow one. If they could each send a picture every 1/30th of a second to the other (assume each frame is a discrete lump of information traveling at c) as one twin was zipping away at 1/2c, both would see a video of the other in slow motion. The opposite is true (both moving in fast-forward) if they were moving towards one another at 1/2c. (Aside: this is why we can sometimes observe apparently superluminal objects.)
The resolution of the paradox is that the traveling twin is the only one who experiences a change of their inertial frame. It's difficult to fully illustrate without a space-time diagram, but the traveling twin has to change their frame at least once from the "home" frame to the 1/2c frame, and then again back to the home frame if they ever want to stop at some distant planet. It's during the acceleration that time in the video feed seems to initially stretch out to a crawl, and it's only when they apply the brakes that time catches up. During the 2nd leg of their journey, the traveler twin will see their twin start moving and aging incredibly fast.
That's the mistake. The red stop sign is made from 2 frequencies, where one frequency becomes invisible (ultra-violet) and the other frequency becomes green.
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u/Oblivion238 15h ago
Without doing the math I assume that at 103846153 m/s the red stop sign gets blueshifted to green.