A Perfect Vacuum, Not

I recall the movie “Alien” had a tagline along the lines of ‘In space, no one can hear you scream’. Why? Because space is a vacuum, and sound (as in screaming) cannot travel from point A to point B if there’s a vacuum in-between. But the question really is, is space a perfect vacuum? Can one achieve a perfect vacuum? If not, why not?

One of the big scientific oops often depicted in Hollywood (and other country’s equivalents) sci-fi space operas is an external view of spaceships, etc. in deep space chug-chug-chugging along with all appropriate sound effects, and/or blasting away with laser cannons or photon torpedos, ditto with appropriate sound effects. Of course, if you really were an external viewer, what would you actually hear? - Absolutely nothing. It would be, or should be, like viewing a silent film from the pre-talkies era. But, for the sake of dramatics, Hollywood (etc.) ignores the physics of it all. ‘Artistic licence’ is what it’s called I believe. 

However, in the physics classroom, where artistic licence isn’t allowed, I’m sure we can all recall from our student days a demonstration of the ringing alarm clock inside the bell jar. As the air was pumped out from the bell jar, the ringing got softer and softer and softer until you heard nothing at all, even though the alarm clock was still jangling away. Of course the science teacher or physics professor told you there was now a total vacuum inside the bell jar and thus no sound could travel from point A – the alarm clock inside the vacuum inside the bell jar, to point B – your ears which were outside the bell jar.

Of course it should be obvious to blind Freddy that there was no such thing as a total or perfect vacuum inside the bell jar. Firstly, no pump is good enough or efficient enough or strong enough to remove each and every last molecule of air from the bell jar. [Of course there is no such thing as a molecule of air, rather atoms and molecules of the various substances that together make up what we call air, but for the sake of simplicity let’s make believe there are molecules of air.] Even discounting those rarefied air molecules left within the bell jar, molecules few and far enough in-between as to prevent the sound of the alarm clock from reaching your ears, the inside of the bell jar still wasn’t a total vacuum.

Why? Well assuming the bell jar was made of glass; light was pouring through the bell jar, and light is a something. The inside of the bell jar was full of visible light. Okay, let’s make the bell jar out of solid lead. That blocks out the light – right? Wrong. Visible light is but a small part of the entire electromagnetic spectrum. Radio waves (a form of non-visible ‘light’) will probably pass through the leaden bell jar, or gamma rays. Even if you succeed in blocking out all of the wavelengths and frequencies of the electromagnetic spectrum, there are still cosmic rays. If you make the leaden bell jar thick enough you might block out all of the cosmic rays, but that still leaves neutrinos, and in order to block all of those, you’d need a bell jar that had a lead thickness of hundreds of light years. Neutrinos can pass through leaden walls as easily as Casper the Friendly Ghost – even easier!

Okay, so you’ve got a perfect pump to remove all the air molecules and sufficient shielding to prevent even neutrinos from entering and passing through. That’s that; now you have your perfect vacuum – right? Wrong again.

You still have gravity not only surrounding but inside the otherwise perfectly shielded bell jar. Even if there were no other matter in the entire Universe, the bell jar itself is made of matter and has its own gravity which resides inside the jar as well as extending to infinity outside of it. Since nothing we know of can block the force of gravity, well that alone puts the kibosh on the perfect vacuum. Gravity is really a real thing, and if you doubt it, I invite you to try to leap tall buildings at a single bound!

Now a perfect vacuum would have to have a temperature of absolute zero, given the total absence of any material substance within. Temperature of course is just a measurement of the average molecular or atomic motion of molecules, atoms, even their fundamental particles. No stuff means a temperature of absolute zero. However the Universe isn’t lacking in stuff which moves around from place to place

For quite another reason however, absolute zero, zero degrees on the Kelvin scale, (or minus 273.15 degrees Celsius or minus 459.67 degrees Fahrenheit) is only theoretical and can never be obtained. That’s because the concept of absolute zero violates the Heisenberg Uncertainty Principle which states that it is impossible, no matter how good your measuring instruments are, to simultaneously know the position and momentum of anything, because the very act of measuring something must alter both parameters. That’s because something must bounce off what you are trying to measure and hence interact with your measuring device, but that bounce alters the position and momentum of that in which you are interested. At a theoretical absolute zero, nothing moves and thus you would know both the position and momentum of that or any object, even say an electron, with absolution precision. The momentum is zero and thus your object is in, and stays in, a fixed location – and besides, there’s nothing to bounce off it anyway, because that something (usually a photon) must also have zero energy and is thus at rest.

And thus we have the concept of the vacuum energy, or quantum fluctuations or the quantum jitters. That is to say, at the extreme micro level, there is always activity and thus motion and thus temperature above the theoretical minimum of absolute zero - thus, no perfect vacuum is possible. Even the best vacuum will have the quantum jitters. Oh, and by the way, the quantum jitters or the vacuum energy has been experimentally verified.

So, if you were somehow expecting that there was such a thing as a perfect vacuum, you’re out of luck, not that that I’m sure will cause anyone any loss of shuteye. However, that doesn’t alter the fact that in space, no one can hear you scream! You don’t need a perfect vacuum for that to be true.

Can Black Holes Evaporate? Part One

While there is a constant transfer of matter and radiant electromagnetic energy (photons) between bodies throughout the cosmos, there are sinks, ultimate final resting places where matter/energy can retire to and be removed from the rest of the cosmos. These cosmic sinks are Black Holes. But is that retirement permanent, or can stuff re-enter the cosmic workforce? Can Black Holes evaporate? The theoretical short answer is “yes”; the long answer is “no”.

Black Holes are astrophysical objects that are so massive, that have gravity so high, that their escape velocity (some seven miles per second on Earth) exceeds the ultimate cosmic speed limit – the speed of light (186,000 miles per second). Since nothing can travel faster than the speed of light, nothing (matter and/or energy) once inside a Black Hole can ever get out again – or so the seemingly ironclad logic went.

However, that’s all according to classical physics. A physicist by the name of Jacob Bekenstein came up with the idea of applying quantum physics to Black Holes (upon a suggestion by his mentor John Wheeler – who incidentally coined the phrase “Black Hole”), and once that was done, well lo and behold, Black Holes apparently exhibited entropy, and therefore had a temperature and therefore must radiate and therefore can vomit out stuff. His ideas were mulled over and over again and finally agreed to and expanded on by the celebrated astrophysicist/cosmologist Stephen Hawking. That stuff that a Black Hole can regurgitate now goes under the name of Hawking radiation, or to give credit where credit is due it is technically Bekenstein-Hawking radiation. However, it’s usually just called Hawking radiation so I’ll stick with that convention.

Of course if Black Holes have a temperature, then they must follow the same laws of thermodynamics as any other object with temperature. One key point in thermodynamics is that energy exchanges between objects are at least partly determined by one object’s temperature compared to another object’s temperature. The temperature of a hot cup of coffee will stay hot longer the higher the temperature of the environment that surrounds that hot cup of coffee. A Black Hole’s temperature must be compared to whatever temperature surrounds the Black Hole when considering the fate of the Black Hole. So how does a Black Hole get temperature?

In retrospect, how this happens is obvious (as are all great ideas when applying hindsight).

There is no such thing as the perfect vacuum. That could only be achieved at a temperature of absolute zero where and when everything is 100% frozen stiff. Alas, such a state violates one of the most fundamental principles of quantum physics – the Heisenberg Uncertainty Principle – where it is impossible to know both the momentum and position of anything with 100% precision. If something were at absolute zero, frozen stiff and standing still, you’d know both the momentum (which would be zero) and position (at a standstill) of that something with absolute precision.

Since there is always a minimum state of energy anywhere in the Universe (something above absolute zero), and since energy and mass are equivalent (Einstein’s famous formula/equation), then that energy state, the false not-quite-absolute-zero vacuum, the vacuum energy*, can generate mass – virtual particles. However, the particles come in matter-antimatter pairs, which usually immediately annihilate and return to their former pure energy state. BUT, and there is always, a BUT – there’s an exception to the rule – that normal state of affairs can be thwarted.

The vacuum energy, that which can generate particle-antiparticle pairs, exists everywhere where existence has any meaning. Part of that existence is an area called the event horizon**, which is a concept related to the concept we call Black Holes. All Black Holes have an event horizon which surrounds them.

The event horizon surrounding a Black Hole is that somewhat fuzzy region that separates the region (below the event horizon) from which gravity rules over the speed of light, and that region (above the event horizon) where gravity’s escape velocity can’t quite dominate that speed of light velocity. I say its “fuzzy” since it’s not razor sharp, albeit nearly so.

The vacuum energy is part and parcel of the space surrounding the event horizon, above, below and spot-on. Now, what if that vacuum energy generates a pair of virtual particles, one each popping into existence above the event horizon; one below the event horizon. Then, the particles will be unable to annihilate and recombine into pure energy. One will stay within the Black Hole. The other, being above the event horizon, can be dealt a ‘get out of jail’ card. And thus, slowly, ever so slowly, but ever so surely, the Black Hole loses mass, thus energy, and evaporates.

Here’s the general picture. Black Holes can only radiate from the event horizon region which, in a very large Black Hole is going to be very cold because it’s not radiating very much, so initially only things like the mass-less photon escapes. Assuming there’s no incoming to replace the loss, the Black Hole shrinks, and as it gets smaller it warms up slightly (that’s what things that shrink tend to do) and can radiate particles with small mass – say neutrinos. When the Black Hole is tiny, it’s very warm, in a relative sense, and it can go out with a ‘bang’, maybe emitting an electron or positron which is way more massive. When there’s no more Black Hole, the vacuum energy still produces at random virtual particle pairs, but there’s no more event horizon from which to separate those virtual particle pairs and thus its all back to normal – the two annihilate and return to their vacuum energy state. That’s where the popular accounts end. End of story. The ultimate fate of Black Holes will be to evaporate via Hawking radiation, even if it does take trillions of years.

Alas, the written texts forget to mention that radiation emission (and other forms of emitted stuff) is a two-way street, not a one-way street. Black Holes can acquire stuff, as well as radiate stuff. If deposits exceed withdrawals, then Black Holes will always have a positive ‘stuff’ balance and thus won’t fully evaporate. Now this is perhaps why Hawking radiation hasn’t been observed. The tiny amount of Hawking radiation (outgoing) will be swamped by the greater, many orders of magnitude greater, amounts of incoming radiation and other stuff impacting the Black Hole.

Forget Black Holes (and their massive gravity) for a moment and concentrate on Planet Earth. Even at night, you see lots of suns – stars. You see them because they are radiating photons – particles of electromagnetic energy of which visible light is a small part. In fact you only detect a tiny fraction of visual photons because your visual detection devices (eyes) aren’t that efficient. Optical telescopes pick up a lot more of them, but they’re still just as real. You are also being hit by photons in the infrared, the ultraviolet, in radio wavelengths, X-ray photons, gamma-ray photons, etc. Though Earth’s atmosphere shields us from some of these photons (ultraviolet photons are far greater in number at the top of our atmosphere than at the bottom), you still get impacted by multi-billions of them; Planet Earth many orders of magnitude more. Some of the photons get reflected back into space; these don’t add to Earth’s energy/mass balance. Overall, there are roughly one billion photons for each and every fundamental particle with mass, like electrons and neutrinos.

Now in addition Earth (and you too) gets hit with cosmic rays, neutrinos, and cosmic dust. Even if you luck out, Planet Earth gets impacted by meteors and other outer space debris, sometimes debris large enough to not only hit the surface but do considerable damage. Planet Earth’s mass increases by many tons a day, all due to Earth’s sweeping up of the interplanetary dust and small rocks that intersect Earth’s orbit. The trillions of neutrinos that hit us are so ghostly that nearly all pass right through you and the entire planet as well despite them having a tiny amount of mass, so as far as our planet is concerned, they are of little significance. 

Now what about a Black Hole?

To be continued…

*If it helps to conceive of the concept of the vacuum energy, here’s an analogy. Think of the invisible but energetic atmosphere as the vacuum energy. Part of that atmosphere consists of invisible water vapour. But, all of a sudden, and for reasons that must have been mysterious to the ancients, part of the atmosphere undergoes a phase change into something you can see; into something solid – like a particle. You get mist/fog (clouds), rain drops, snow, sleet, hail, etc. Then, equally mysterious, those solid bits eventually undergo another phase change (evaporation standing in for annihilation) back to invisible water vapour in the equally invisible atmosphere. And so you have the invisible vacuum energy that generates particle-antiparticle pairs which annihilate back into the vacuum energy.

**The surface area of the event horizon is the same for both incoming and outgoing so there is no need to take that (non) variable under consideration.

Energy: A Passport to Your Afterlife?

When you die, your energy has to go somewhere. Some say that’s your passport to the afterlife. Your energy is you after you die. I say that’s a load of codswallop!

I read a while back that because your body contains energy and because energy can’t be destroyed, when you die it’s your body’s residual (‘life force’ or ‘psychic’) energy supply that becomes the ‘you’ in the realm of the afterlife. Sorry, ‘fraid not. It’s an interesting idea but with no ultimate merit.

It is crystal clear that when you die your physical body goes nowhere; not to La-La-Land Hell; not to Never-Never-Land Heaven. More likely as not you’re buried, cremated or given to the medical students to gawk at and dissect. What about that other ‘half’ of you, your energy? Where does it go, if it in fact it goes at all?

An Energetic Afterlife: The living body is full of energy. What happens to all that energy when the living body turns into the unliving body? Energy, after all, can neither be created nor destroyed; only changed in form. Can you take your energy with you to an afterlife; in fact is it your body’s energy that becomes ‘you’ in an afterlife? Alas, no. Let’s examine the various forms of energy, see which forms apply to the living body, and what happens to those relevant forms of energy when you start to push up those daisies. I’ll start with the non-starters, for starters.

Kinetic/Potential Energy: Kinetic energy is energy of motion, but after you die, you don’t move, so your kinetic energy is zero. Your potential energy is also zero unless an outside force propels you into motion and you (well your body) gain kinetic energy, but you have no control over that motion. If you just lie forever on the slab (or in the grave), your potential energy is for all practical purposes, zero.

Gravitational Energy: Your living body has mass therefore it has gravity. Your dead body has mass, therefore gravity. Gravity stays put when you die; you don’t take gravity with you into the great unknown, or rather gravity doesn’t take you into the great unknown.

Nuclear Energy: Nuclear energy comes in two forms. Firstly, there’s nuclear fusion which does not happen inside you unless you’re a Sun God (or the Sun) or an H-bomb. Secondly, there’s nuclear fission which comes in two forms, fast and slow. Fast nuclear fission is akin to an A-bomb going boom. Slow nuclear fission is radioactivity. You are slightly radioactive since some of the carbon you ingest is radioactive not to mention radioactive stuff from nuclear fallout and the natural environment that gets into your system. But once you die your intake ceases and that radioactive energy just ticks away and decays in the fullness of time down to nothing, or at least down to non-radioactive substances. All those alpha particles, beta particles and gamma rays just go back into the environment.

Sound Energy: The energy of sound is apparent when sonic booms rattle windows and opera singers shatter wine glasses. Alas, while you may have been the biggest loudmouth on the block while alive, when you’re dead, you can hear a pin drop!

Solar Energy: Ultimately the product of nuclear fusion, you can lie in the Sun and get a nice tan and your quota of Vitamin D, but sitting in the sunshine won’t increase your athletic abilities or contribute in anyway to increasing your body’s supply of energy. If that’s what you want, eat sugar.

Thermal/Geothermal/Heat Energy: Sitting in a hot tub; soaking in a thermal hot spring may make you feel good, but such pursuits do nothing to increase your energy levels. Again, if you want more energy reserves (body fat), eat lots of sugar.

Wind & Wave Energy: You may pass wind and make waves but these forms of ultimately what is solar energy transformed contributes nothing whatever to your energy quota and is irrelevant from the point of view of any afterlife you aspire to.

And now let’s turn to forms of more energetic relevance. 

Body Heat: On average, your body is warmer than the surrounding environment, so when you die, this infrared (IR) heat energy in keeping with the second law of thermodynamics cools off and obtains equilibrium with the temperature of the surrounding environment. Your IR energy just goes into warming up the surroundings until your body and your surroundings are the same temperature. Your dead body, while you still have a body, will contain heat energy since your dead body has a temperature. But since that temperature is the same temperature as the surrounding temperature, that energy is useless for performing any actual useful function. Besides, that heat energy stays with the dead body. Now what would be impressive is that when you die your body temperature immediately drops way, way, way below room temperature as if your entire packet of body energy just packed up and moved somewhere else. Alas, that doesn’t seem to happen. In fact, to be honest, it doesn’t happen full-stop. 

Chemical/Electrical Energy: You do have lots of chemical energy within you, all manner of chemistry is going on inside you and some of that chemical energy is converted to electrical energy. What happens to that electrical energy when you die? Well, what happens to the electrical energy in a wire leading to the light bulb when you turn off the switch? Same difference. That’s in fact one definition of death – no electrical energy present.

Body Chemistry: What about all that chemistry inside you? Well, when you die, your bodily chemistry goes into reverse. Entropy resumes its natural order and increases. Your disorder increases. Your body’s chemistry breaks down and decays to less complex chemistry (giving off odours in the process), but that decay is caused by other organisms, usually microbes. Microbes decrease their disorder by causing yours to increase. You no longer eat; you are now the eaten. Your chemical/electrical energy becomes their chemical/electrical energy. You don’t take it with you; you don’t share it; you give it all away. Your loss is the gain of others. When the very last bits of you are consumed, fossilized, weathered and eroded away to dust and below down to individual atoms scattered to the four corners of the globe, then there’s no ways and means of talking about your energy – it’s gone; not destroyed, just gone.

Body Chemistry Frozen: So what if your body is put in dry ice or liquid nitrogen, etc. where no microbes can get at you? Well, you’re entropy (disorder) might not increase, but it doesn’t decrease either (you’re entire life is one long battle keeping disorder at bay). In short, once you’re dead, there’s no way to decrease disorder; the best you can hope for is a stalemate. But again, your dead body’s temperature is the same as its surroundings, so nothing useful can be accomplished; there’s no net energy flow from A to B or from B to A. What about just being put in a sterile environment at body or at least room temperature? Alas, that won’t work since your dead body will be consumed from the inside by the billions of hungry microbes already living inside of you. If you’re frozen stiff, then the microbes inside you are also frozen and can’t munch on you.

In conclusion, all the energy that’s part and parcel of, and in you right now as a living being will get disbursed into the wider environment once you kick-the-bucket. You can’t have an energetic afterlife based on your energy reserves at time of death. There just is no association between your energy and an energetic afterlife. Sorry ‘bout that!