Here are a few interesting facts to ponder — things that might not seem possible, but which are true.
Which planet, on average, is closest to the Earth?
You’re probably inclined to say either Venus or Mars, going by the simple logic that in the order of orbits, Venus is #2, Earth is #3, and Mars is #4. You might also have remembered that the distance between each successive orbit follows a formula, meaning that, by definition, Venus has got to be closer to Earth than Mars.
This makes sense because each successive orbit is larger than the previous by an increasing ratio that is similar to the Fibonacci sequence, although it’s hardly exact. It does mean, though, that Earth is closer to Venus than it is to Mars and it naturally follows that it’s closer to Venus than it is to Mercury.
But the question included “on average,” and if we take that into account, then the planet closest to the Earth is… Mercury. in fact, Mercury is the closest to every planet in the solar system, on average, period.
The simple reason for this is that Mercury’s orbital period is so short — a “year” on Mercury is only a smidgen under 88 days, meaning that it orbits the sun 4.15 times (on average) for every orbit that the Earth makes. Meanwhile, Venus only goes around 1.63 times for every Earth year.
This adds up, because Mercury is on the same side of the Sun as we are for a lot longer than Venus, and when Venus, or any planet, is on the far side, its distance from us is basically double the orbit plus the diameter of the Sun.
This is obvious if we really simplify the numbers. Let’s just randomly designate the distances by orbit: Mercury = 1, Venus = 2, Earth = 3, and Mars = 5.
When Mercury and Earth are in alignment on the same side of the Sun, the net distance is 2 (from 3-1). For Venus, it’s 1, and for Mars it’s 2. But put the planets on the other side, and the formula changes to 2O+Sol, or twice the orbital distance plus the diameter of the Sun, so the new figures are:
Mars: 2(5-3)+Sol = 4+Sol
Venus: 2(3-2)+Sol = 2+Sol
Mercury: 2(3-1)+Sol = 4+Sol
We can eliminate the +Sol from each equation since they all cancel out, and this might make it look like Venus is still the closest, but those orbital periods make a big difference, because Mercury spends a lot more time on the near side of the Sun to us than Venus does.
If we look at the averages, because Mercury gets more time in our neighborhood, in the long run it averages out to be the closest planet to Earth — but the formula holds true for every other planet in the Solar System.
Are there more stars in the universe or atoms in a human being?
Using 70 kilos as an average human weight, the answer to this one is rather simple, and the winner outnumbers the loser by a ration of 7 million to 1.
A human body has approximately 7 octillion atoms in it, and most of those are hydrogen, since we are mostly water, and there are two hydrogen atoms per oxygen atom in each molecule of water. The universe has approximately 1 sextillion stars in it and, not surprisingly, most of the universe is also made of hydrogen.
That’s kind of remarkable when you think about it, because hydrogen is the lightest of all of the elements and the simplest of atoms, made of one negatively charged electron and one positively charged proton. Yes, there are variations, or isotopes, with some neutrons slipped in there.
These neutrons are what make so-called “heavy water” so important in nuclear reactions, but chemically they make no difference, since those reactions only rely on the electron and proton.
Now, as to the answer on whether humans have more atoms or the universe has more stars, you may have already guessed it if you remember your STI and/or Greek counting prefixes. “Octillion” comes from the number 8, and refers to a number in the thousands with 8 groups of three zeroes after it. “sextillion” comes from six, and refers to a number in the thousands with 6 groups of zeroes after it.
Since the human body has about 7,000,000,000,000,000,000,000,000,000 atoms in it while the universe only has 1,000,000,000,000,000,000,000 stars, humans win, with 7 million atoms per person for every star.
What would happen to the Earth if the Sun suddenly became a black hole?
Gravitationally, nothing, unless the Sun lost a little mass in the process, in which case we’d drift a bit farther out in our orbit.
Otherwise, though, Earth would get very cold and dark and, depending on the orientation of things, we might or might not get blasted by intense gamma radiation that would scrub the planet clean of all life and its atmosphere.
We wouldn’t be able to see the Moon or planets anymore, just the stars, and we’d freeze to death pretty quickly but don’t worry — the Sun is too small to ever become a black hole.
People have this impression that black holes are cosmic vacuum cleaners that suck up everything that gets near them, but that’s not the case. They’re really just a matter of shoving ten pounds of gravity in a one-pound sack. Okay, maybe more like a hundred tons in a knee sock.
But the point is, the gravitational pull of that black hole is going to be no greater than the pull of the original object, and you have to get a lot closer, physically, before you hit the point where you can no longer escape.
Does my phone have more power than the Apollo 11 computer, and could it land me on the Moon?
Yes… and no. All of our phones have more computational power than a computer the size of a warehouse in 1969, and they can do amazing things. However, they would need very specialized apps in order to be able to do the kinds of calculations needed to adjust velocities and trajectories precisely on the way to the Moon, second to second.
Google Maps won’t do that because we don’t have GPS that works off-Earth. Your phone would have to be able to spot the Moon and either Earth or Sun, plus another star or two, all visually, calculate the angles between them, then keep track of them and use that to calculate velocity and direction.
At the same time, your phone would also have to interface simultaneously with 150 onboard devices and run five to seven programs at once. In case you hadn’t noticed, phones and computers don’t really multitask anymore. They stopped doing that when systems became fast enough to just pick up where it left off when you switched windows, so that it just looks like that other program was running in the background the whole time.
The onboard computer on Apollo 11 was still a lot bigger than computers today, at 70 lbs (32 kgs), but it did the job and, because of the elegant way in which the code was written, it only required a grand total of… 2 kilobytes of memory, which is about 2,000 characters.
Yes, the actual code written for it was a lot bigger, but that 2Kb was working memory, and that was what was so elegant about it. The software itself was stored in static memory, which was literally woven by hand.
No, really. It was even called “rope memory.” This essentially created an incredibly complicated addressing system where the intersection of a particular pair of wires indicates the location of a single bit of data.
Touchtone phones worked on this same principal for years, and your phone and computer keyboards still work this way to this day. In fact, this two-point address scheme is still what makes your touch screens work as well.
It’s still mind-boggling to realize that not only did this computer somehow manage to do all of its runtime stuff in only 2Kb of memory, but that they had conceived of the idea of virtual runtime environments even then, so that they were able to run those five to seven programs at once, in such a small space.
What makes water so special?
The very short version is this: if water didn’t expand when it froze, life on Earth would not be possible and we’d probably be an ice-ball planet.
Water molecules have an interesting property. Made up of one oxygen and two hydrogen atoms, the hydrogen atoms naturally attach to the oxygen at 120° angles. Well, basically, since the whole thing is ultimately defined by the electron field around it in which we can only determine the likelihood of an electron’s location.
But it does give water these properties: When it’s a gas, the molecules bump into and spin off of each other. When it’s a liquid, they flow around each other. However, as the temperature lowers, a funny thing happens. Those hydrogen atoms in the molecules start to line up — remember, a sphere has 360° around it — and so as the water molecules slow down (i.e. as the temperature drops) the molecules line up and lock together and begin to create a crystal lattice.
You can see it large scale in a snow-flake, with its six-sided symmetry, but down on the molecular level what’s really happening is that the molecules are actually forming rigid structures and pushing themselves apart as they align.
And so… as liquid water turns into ice, it expands, and this is good for us (but bad for the Titanic) for one very big reason. It reduces the density of ice, so that it floats in water. If it didn’t, we’d be screwed, because ice would sink, wind up on the bottom, and then tend to never thaw when winter ended.
Eventually, entire lakes, rivers, and seas would completely freeze over, removing liquid water at first from our aquifers and, eventually, from our atmosphere. The Earth would become one vast desert, and the reflection of sunlight because of all that ice would just add to the runaway freezing.
Is time travel possible?
The short answer is “probably not,” at least not to the past, although time travel to the future is technically possible through things like suspended animation — as in if you travel more slowly than everyone else, you’ll objectively get to the future faster.
But your real question is, “Can I jump into a time machine and visit another era?” And the answer is this: “Sure, if you figure out how to actually travel in time, go for it, but you’ll need to figure out how to travel in space as well. Or, at the very least, do complicated equations that would have blown the circuits out of those first NASA computers.
Example: Marty McFly abandons all common sense, and jumps into the crazy old man’s time machine even as he’s being gunned down by terrorists. Marty guns it, the car hits 88 miles an hour, and suddenly Hill Valley and the Twin Pines mall vanish…
And the car is drifting somewhere in interstellar space. Since it’s not pressurized, Marty very quickly dies, alone and billions of miles away from Earth. End of movie, and the trilogy never exists.
That’s because everything in the universe constantly moves. You may think that all of those atoms in your body don’t move at all, but that’s not true at all. The ones that are part of organs or tissues or the like may seem to be stuck in place, but they are constantly vibrating as they react with neighboring atoms. This is why you’re not a frozen block of ice.
The universe has two speed limits — the fastest you can go and the slowest you can go. If you have any mass at all, no matter how small, you can never reach the speed of light, or C. If you have no mass, you can only ever travel at C — which isn’t all that weird when you think about it.
Meanwhile, the bottom speed limit of the universe is motionless, which is defined as Absolute 0, or 0ºKelvin (-273.15ºC or -459.67ºF). Nothing can reach this temperature, because it would mean that it would have absolutely no motion at all.
The problem is that if something is not moving at all, we know its precise location. And, if we know its location, we cannot know its exact momentum. This is the core of the Heisenberg Uncertainty Principle, and, obviously, if an object is completely motionless, then we know both its location and its momentum.
As it turns out, molecules have a very clever way of hiding themselves when they get close to 0ºK. they turn into a fifth state of matter called a Bose-Einstein Condensate. In this case, suspecting that we’re about to figure out where they are, all of the atoms being reduced in temperature suddenly give up their angular momentum gladly. At the same time, they all kind of smear into a indeterminate blob, so that we have no idea where any single atom in the group is.
And… problem solved. Okay, the atoms aren’t thinking at all while this is happening. It’s just a result of the change in velocity that dictates which property is going to be hidden. But just as you can’t accelerate mass past the universal speed limit, you can’t slam the brakes on mass and bring it to a complete stop.
Note that I have no idea whether the Bose-Einstein thing affects photons, since photons do have momentum and spin, but by virtue of having no mass probably also have no real location, especially because (just a guess) they still move at the same speed at 0ºK.
Photons are tricksey fuckerses.
But despite all of that, okay. Let’s assume that time travel is possible. Marty hops in that DeLorean, travels back 30 years and, assuming that time travel is legit, he’s still not going to be in the same place on Earth because gravity isn’t going to work that way either.
Gravity is a very long range force, and it’s very strong on cosmic scales, but it’s absolutely not on quantum scales, and this may actually be the reason that it’s been so hard to reconcile classical physics with the quantum.
Look at it this way. Why do “flat-earthers” exist? Because, from their very limited perspective living on the face of the planet, the place really does look flat.
Even if you march their sorry asses to the beach and make them watch as giant cargo ships rise above and vanish below the horizon, they still won’t buy it.
You need to take them up and beyond so that they can actually see the curve and experience the gravity and all of that. I mean, after all, even if you circumnavigate the globe by boat, plane, train, automobile, or whatever, it’s still going to seem flat to you without that heightened experience.
So… how does gravity affect space time? It bends it. Or, in other words, gravity takes “flat” space time and curves it. And on a human scale, this is really easy to experience. Toss a ball into the air and watch it fall. It’s not going to land in quite the same place.
But on the quantum scale? Nope. Everything there would appear “flat” as well, because any bend of space that gravity might create would be totally imperceptible to particles so small.
So the force that would normally hold Marty and the DeLorean onto the ground on Earth and keep him in Hill Valley become totally irrelevant when you start to fuck with the quantum shiz that would be necessary for time travel.
The DeLorean pops out from here but is no longer bound to Earth or anything else by gravity, since it’s skidding gleefully through time but not limited by velocity — as in it will never travel faster than light, but does so by following an alternate path through space that, nevertheless, will still land it at the target date and place on the particular world it departed from.
In the Universe at large, that time and date 30 years ago in Hill Valley is exactly where it was in the 30 years ago of the place Marty left, which means he’s at least 22 billion miles away from the solar system, with the Earth itself some smaller increment nearer or farther.
It definitely doe not include the about 19 billion kilometers that the entire Milky Way Galaxy has moved toward the Great Attractor between the constellations of Leo and Virgo. Without that DeLorean being able to do some very complicated math and some space travel as well, it’s going to be a very short trip to the past, and no coming back to the future