Atoms can release some of their energy, in discreet packets of photons. They pay for this release by having the outer shell of electrons drop down into an orbit closer to the nucleus. They can also receive energy first, in the form of electrons or photons, and then re-release the energy as photons – that is how flashlights and lasers work.
Photons are totally weird. Two or more can occupy the same time and space, and when separated, they are so romantically entangled as to still behave as if they were one. Spin one, and the other will spin, no matter how far away it is.
And they tunnel through time. Take the point of view of a photon. As it is emitted, no time occurs at all until it it causes a reaction to another atom, no matter how far away. If you glance up to see a star that is 1 million light years away, that light took 1 million years to travel, however from the point of view of the photon, no time elapsed. If you were able to hitch-hike along on the back of the photon, you would experience no time elapsing from the moment you departed the star, until the moment you arrived on earth.
And photons are not even things. They aren’t shaped like balls, or cubes, or bicycles. They travel through two slits at the same time, yet react with stuff in discreet positions of time and space, as if they were things.
And they don’t respect the idea of speed. If I’m zooming down the highway at 100 miles per hour, and I have a slingshot that can release a marble at 100 miles per hour, if I shoot it ahead of me, the bullet will leave the car at 200 miles per hour, relative to the highway. If I shoot behind me, it will fall straight down, bounce a few times, and sit there quietly minding its business. Not so photons. No matter how fast my car travels, the photon will zoom out from the front of the car at the same speed as it leaves the rear. Photons make a mockery of the idea of relative speed.
If I were to accelerate an atom to near the speed of light, and send it out towards a detector located 4 light years away near the star Betelgeuse, and then after two light years this atom releases two photons – one aimed towards the detector near Betelgeuse, the other towards a detector on earth, both photons will arrive at both detectors at the same time. The photon arriving at Betelgeuse will arrive at nearly the same time as the atom; the time difference coming because the atom is travelling just under the speed of light, as it would take an infinite amount of energy to accelerate an atom to 100% of the speed of light.
If you accelerate matter close to the speed of light, it also starts to tunnel through time – the closer you get to the speed of light, the less time you will experience passing – so if you left earth on a rocket and zoomed about for a distance of 100 light years at 99% the speed of light, when you arrived back on earth it would be about 101 years later, and you would have only experienced about 1 year of travel.
Light totally messes with time and space. This means that time and space are also totally weird. Photons can entangle, and affect each other at any distance, making the distance of space meaningless. Fom their perspective they take no time to travel, yet from the perspective of photon detectors, they travel at a constant speed. They have no discreet location and behave like a wave, yet interact only in discreet packets of energy with discreet location and time.
We can only describe how light behaves, and what it does. We aren’t able to visualize it as a thing. Things require locations – they occupy a specific shape and volume of space. A photon (or packet of energy) occupies a range of space all at once, a range that is as wide as its wavelength, which can be from really small (one plank length of 10 to the minus 35 meters) up to hundreds of thousands or more miles wide, but when it interacts with anything, the photon disappears and gives up its energy to whatever absorbs it, usually by either bumping off an electron from an atom, or raising an electron up to a higher orbit around the nucleus. The photon didn’t bump into the electron, like a billiard ball might bump into a beach ball. It was a wave front that crashed onto a beach full of beach balls, and instantly disappeared after moving one random beach ball.
And different wavelengths of light react with different types of beach balls. Visible light travels through glass, while infrared will be absorbed by it, making the electrons move faster and so heating it up. X rays go through wooden walls, but not lead. Each frequency reacts differently with different types of matter. They also travel relatively faster or slower through space than each other, with a short frequency that occupies less space, like gamma radiation, moving fast, with a long frequency with a wider wave-front, like infrared, moving slower.
If I were an atom of plutonium, I’d be feeling too cranked up, and want to wind down a bit. I’d let off little excess energy by sending out a photon. Ah, now I’m less hot, more relaxed, less energetic. The photon ripples through space/time, travelling in a direction and with a wave-front-width, passing through and past barriers, until one particularly sexy atom catches it’s attention, at which point it disappears in orgasmic union with the atom, imparting its energy as hyped up heat.
This is where the idea of entropy comes from. That there is a finite amount of atoms and photons, and all that they can do is radiate into each other. After billions of years of atoms orgasming into each other, all the atoms will be at the same temperature – none hotter than the other. Since energy can only be extracted from a difference in temperature, there would be no more possible chemical or energetic reactions. Everything would be at just slightly above absolute zero in temperature, with no more photons being released, and no more chemical reactions. Entropy means that we can move matter and energy around, but doing so mushes up the average temperature, until we have no temperature difference left with which to use to move stuff around. On earth we can get around entropy by bringing in an outside source of energy; the sun. Without that the best we could do is burn matter into heat to keep our houses warm, until we’d have to resort to burning our own houses.
If there were some way to get energy from outside the universe, then it could sustain life forever. Some physicists believe that since space itself is a quantum foam of particles coming into being and falling back into non-being, it may be possible to extract energy from the background potential-of-being that empty space possesses. Vacuum energy is no more preposterous than the big-bang.
Space is weird – it entangles with each other across limitless distances, boils with particles coming out of nothing and going back to it, warps itself into strange shapes that make time slow down, and limits the maximum speed at which objects and information can travel. And weirdest of all is that it allows for us to have subjective experience; a knowingness aspect to our sense perceptions.