Lois & Clark Forums Forums General Discussion Off Topic You can't go home again

Female Hawk, Corinna, is just finishing a remarkable Elseworld fic where Clark Kent was brought to New Krypton at fifteen instead of at thirty, and teenaged Clark was given an amnesia-inducing drug, so that he couldn't remember his life on the Earth. In Corinna's fic Lois arrived on New Krypton, however, and together they made the journey back to Earth. I complained in some FDK I wrote that Clark was making three separate light-year-long trips in space, and after these super-marathon journeys he was still able to meet his happy and healthy parents back on Earth, which wouldn't possible. But really, that's exactly what happened in the show, too. The only difference is that Clark was older when he made his return trip to New Krypton in the show, and his parents knew where he was going (as did Lois, whom he was sort of standing up, too, but that is another story!). So the impossible space flights were already established facts in the show, and Corinna just took the idea and ran with it!

Anyway, I remained unhappy about this back-and-forth space travelling, and Corinna asked me why I kept insisting that such return trips in space would be impossible. So that's why I'll try to answer now.

First of all, space is unimaginably vast. It really is. That is why it is humanly impossible to understand how far away even the nearest star apart from the Sun is. Heck, it's extremely hard to understand how far away even the Sun is, even though it's not impossible to understand that. To make a mental picture of it myself, I have made my own little model of the inner solar system.



This is an image of the Sun. The Sun isn't actually yellow, but never mind – the idea that the Sun is yellow is firmly established, and I needed a big round yellow thing to represent it. I needed a huge ball or a balloon, but I couldn't get one, so I persuaded an aquaintance of mine to sew a round yellow table-cloth for me instead. The diameter of the table-cloth is two meters, a little more than two yards. Two people held up the table-cloth for me to make it look round, and there I had my model Sun.

To make models of the planets of the inner solar systems I used cotton balls, two centimeters in diameter. That's because the diameter of the Sun is about a hundred times the diameter of the Earth (actually a little more, but never mind). Take a look at the picture of the Sun again! Can you see a sunspot on it? The size of that sunspot is about the size of the Earth, when you compare it with the Sun.



Tiny planet Earth.

Anyway, I used a small white cotton ball to represent Venus, a similar blue cotton ball for the Earth and a red one for Mars. For Mercury and the Moon I used little yellow peas.

Now I needed to place my model Sun and planets at the correct distances from each other. The distance between the Sun and the Earth is about a hundred Sun diameters, so if the diameter of the Sun is two meters, then the distance between the model Sun and Earth must be two hundred meters. Two friends of mine held up the yellow "Sun” for me, and I took the blue cotton "Earth" and walked away with it. I stopped after two hundred meters, and it was amazing how my friends and the model “Sun had shrunk when I looked back at them. But the yellow “Sun” looked about as big as the real Sun generally looks in the Earth's skies, so I guess I got the relative sizes and distances of my model Solar system moderately right. But the people who held up the "Sun" told me that the "Earth" I held up to them disappeared from view long before I had made it to the proper distance from them. At a distance of two hundred meters, my two centimeter cotton ball Earth was just too tiny to be visible.

A planet that is of great interest to us on the Earth is Mars, because it is the nearest planet to us where there is a reasonable chance of finding signs of past life. (Some optimists believe there is still microbial life on Mars.) So how far away is Mars? It is actually about one and a half times as far away from the Sun as the Earth is, so if the distance between the Sun and the Earth is two hundred meters, then the distance between the Sun and Mars is three hundred meters. But since Mars and the Earth follow their own individual orbits around the Sun, the distance between these two planets varies. The minimum distance in real life is 75 million kilometres (which is the same as four light-minutes), and the maximum distance is 225 million kilometres, or twelve light-minutes. That is the distance to Mars, which will be humanity's first incredibly important stepping-stone in our attempts to go to distant worlds. (Yes, we – or you Americans – have already made it to the moon, believe me.) But we have not made it to Mars, not so that we have managed to send astronauts there. Why not? It's because it is too far, too difficult, too expensive, too risky. Humanity is not sufficiently technologically advanced to send people there, not yet.

Maybe you object that I seem so certain that American astronauts have landed on the Moon. If people have landed on the Moon, surely we can also send people to Mars? Surely the difference can't be that great?

But it is. The difference is distance. The distance to the Moon is about 450,000 kilometers. Let's make a round figure and say that the distance to the Moon is 500,000 kilometers, or half a million kilometres. Remember that the minimum distance to Mars is 75 million kilometres. That means that even when Mars is at its closest, it is 150 times farther away from us than the Moon. Suppose you have a kid and you have taught him to swim a hundred yards. Would you say that just because he knows how to swim a hundred yards, he can also swim 150 times farther than that, or ten miles? Would you be comfortable dropping your kid in the middle of a ten-mile lake, just because he knows how to swim a hundred yards?

On August 31 New York Times ran an opinon piece by Lawrence M. Krauss, where he argued that it may be possible to send astronauts to Mars, but not to bring them home again. Here are some quotes from what Krauss said:

So the cost of sending people to Mars would be prohibitive. But that is not all:

So this is Krauss' solution:

The problem of bringing the astronauts back to Earth is worse than sending them to Mars in the first place, according to Krauss. He argues that we should send older astronauts to Mars and let them work and do science there until they die on the red planet.

So according to Lawrence M. Krauss, you can't go home even from Mars! But he is wrong about that. Sooner or later, barring the possibility that some catastrophe befalls our civilization, humans will invest the money and figure out the science needed to send other humans to Mars and back again. Because even though it will be exceedingly hard to send humans to Mars and back again, it will not be impossible. Again the reason is distance. Mars is only between four and twelve light-minutes away, after all.

But Mars is, at best, the home of a few super-hardy microbes. If we are looking for planets that host higher life forms, we'll have to look much, much farther away. We'll have to look for other solar systems, and the nearest possible solar system is the Alpha Centauri star system, four light years away. We don't know if any of the three suns of the Alpha Centauri system have planets, and we don't know if any of the hypothetical planets there are able to sustain life. We do know, however, that if we are looking for advanced alien life forms, the Alpha Centauri system is the absolutely closest place for us to look. And it is four light years away. Remember that the minimum distance to Mars is four light minutes. How many minutes are there in a year? The answer is 60 x 24 x 365, or 525,600 minutes. Therefore the distance to Alpha Centauri is about half a million times longer than the minimum distance to Mars, and about 175,000 times longer than the maximum distance to Mars. Suppose you have taught your kid to swim across a ten mile lake, which would not be an impossible feat. But surely you don't believe that just because your kid can swim across a ten mile lake, he can also swim more than a hundred thousand times longer than that, or more than a million miles in one go? How many times would he have to swim around the Earth before he had logged a million miles?

Now maybe you object that the comparison between swimming and going somewhere in a spaceship isn't fair. The human body can only do so much and swim so far, but surely we can build far, far better spaceships than the ones we have today, and surely we can make much, much better and more efficient fuel? Surely we can travel exponentially faster than we are able to do today?

Before we talk about how fast we might be able to travel, consider the problems of travelling fast. Take a look at this car:



Why is the car so smashed up? It's because it collided with something, and it was travelling too fast. The faster you go, the worse the consequences will be when you collide with something. But surely that isn't something we need to worry about in space, where there is nothing to collide with?

Wrong. There are certainly things to collide with in space, because space isn't empty. Certainly the risk of colliding with a space boulder is close to zero. The risk of colliding with a pebble is far greater, and it is a certainty that you will collide with tiny grains of dust. But if you travel at a sizable fraction of the speed of light, those tiny grains of dust will hit your ship with the force of a volley of tiny bombs, making your ship and anyone inside it look like Swiss cheese.



Also, the ubiquitous even tinier particles out there will hit your ship like an incessant shower of radioactive particles. That's right, those particles that aren't radioactive in themselves will gain so much energy from a head-on collision with your speeding ship that they will literally make your ship glow with X-rays. Face it, after speeding through space and colliding with everything out there your ship will be in no better shape than the car wreck in the picture above!

The fact that you will be colliding with particles all the time also means that space will exert friction on your ship. All those incessant mini-collisions will slow you down. Space will feel “thick”, forcing you to fight your way ahead. You'll need huge amounts of fuel to keep your speed up.

Suppose this problem is solvable. You may be able to deflect all those particles, creating innumerable ricochets. (Thanks, Sue!) That means you only have to concentrate on travelling fast enough. Piece of cake, right?

Wrong. Here is where Einstein gets into the picture.



According to Einstein, it is impossible for anything to travel faster than light, or for anything made of matter to even travel as fast as light. I don't know why that is so, but I know, more or less, the basics of how it works. Most humans intuitively expect speed to be something that increases linearly. If we add one unit of extra energy to a vehicle, we expect to get one extra unit of speed out of that energy. Think of it like this. Here you can see a dad pulling his kids on a sled:



Imagine, instead, that the dad was setting the sled in motion by pushing it. One push represents one unit of energy, and this unit of energy will give the sled a certain speed. The dad, who is in better shape than he looks, is able to keep up with the sled by running behind it, and before it slows down he gives it another push, an identical unit of new energy. Since the sled has now been given two units of energy, it should now move by “two units of speed”, which means it would go twice as fast as when it was given just one unit of energy, assuming there is no such thing as friction.

Sounds good. Except that's not how it works. The speed of an object is not an isolated phenomenon, but it is tied to the mass of the object that moves at this speed. Mass and speed are linked together. You have to consider the momentum of an object, the combination of its mass and speed.

Here on Earth, we move at such low speeds that if we add a unit of energy to something to increase its speed, then 99.9999% of that energy will either actually increase the speed of the object or else be lost as heat. Only a tiny, tiny fraction of that unit of energy will change the mass of the object whose speed we wanted to increase. But as we move faster, an increasingly larger fraction of each unit of energy that we add in order to increase our speed will actually change our mass instead. Our mass will increase as we add more energy in order to gain more speed. As we approach the speed of light, more than half of each extra unit of energy that we add will increase our mass instead of our speed. In the end, 99.999999…% of each extra unit of energy that we add will increase our mass.

So according to Einstein, when you try to increase your speed, your acceleration will show what is called “a decaying exponential curve” instead. It looks like this:



As you try to increase your speed, you will get ever-decreasing “speed returns” on your “energy investments”, and the “extra calories” will just make you fatter instead!

No really, I'm just joking. You won't grow fatter, just more massive. This effect has already been proved with subatomic particles. As their speed increases, they gain more mass.

So try as you might, you won't ever shatter the universal speed limit, the speed of light! Okay, I can't resist this image:



Man gaining mass as he is trying to travel faster than light?

So you simply can't travel faster than light, or even as fast as light. Okay, but what about wormholes? They can transport you pretty much instantly over enormous distances in space, can't they? They can – if they exist. But there are problems here. Astronomers agree that wormholes can only exist in the immediate vicinity of a black hole. Disregarding the unimaginable dangers of closely approaching a black hole and actually diving into the wormhole connected to it (and most astronomers believe that the wormhole will collapse if anything falls into it), you will actually have to travel to the black hole under your own power in order to avail yourself of the wormhole that may be connected to it! So how far away is the nearest black hole? Would you believe I came across an answer to that question just yesterday? According to a magazine called BBC Sky at Night, July 2008, the nearest black hole is a binary system called A0620-00, and it is about 3,500 lightyears away. Do you realize how long it will take to travel 3,500 lightyears if you can't travel faster than the speed of light (and actually you can't even travel that fast)? It will take thousands of years! Forget about the wormholes!



Wormhole. Let's hope you emerge safely from it, if you manage to transport yourself to the wormhole in the first place. Don't hold your breath.

So it will take much too long to travel to the wormholes that might be out there for us to use them for transportation, assuming they don't kill us instantly if we manage to travel to one of them. But it's not only the wormholes that are so far away that a journey there will take a horribly long time. Actually, most astronomers agree that it may well take thousands of years to travel even to the very nearest star, Alpha Centauri, even though it's only four light years away. That's because of the enormous problems that come with travelling really fast in space. Remember all the tiny particles in space that are going to hit you like a shower of nuclear mini-warheads, or, at best, slow you down enormously. Also, remember that the faster you go, the harder it becomes to accelerate. So it may not be possible to travel more than a few dozen times faster than today's fastest spaceships, and if so it will certainly take thousands of years to reach Alpha Centauri. But if it takes that long, is it going to be possible at all to send human beings to another solar system?

Maybe it will. One possibility is that you have a multi-generation ship, where people have children on board. These children grow up and have children of their own, who in turn grow up and have children of their own, etcetera. That way it will not be the original astronauts who make it to the stars, but their distant descendants.

Another possibility is that the astronauts are put in suspended animation. In theory, they could survive in suspended animation for thousands of years and then be woken up when they approached their target.

A third possibility is that it might be possible to travel at a speed close to the speed of light after all. If so, the astronauts' “personal time” will slow down. Let's assume it would be possible to travel fast enough to make it to Alpha Centauri in, say, six years. That would not be a forbiddingly long time, and while the astronauts' personal time would slow down, the effect would not be very large. And if it was possible to travel at the same speed home again, the astronauts could return home within, say, twenty years. Please note that twenty years would have passed on the Earth! For the astronauts, the time would be shorter. But many of the astronauts' near and dear ones would still be alive after twenty Earth years, and the Earth the astronauts returned to would not, hopefully, have changed beyond recognition.

However, if it was possible to travel to Alpha Centauri in six years, would it really be possible to return home? Remember that Lawrence M. Krauss argued that it will be too hard to bring astronauts home from a place as close to home as Mars! The main reason cited by Krauss was that it would cost too much fuel. But seriously, how much fuel would it take to send a spaceship to Alpha Centauri, boost its speed to more than 50% of the speed of light, spend more fuel keeping up that speed in spite of all the particles hitting you, then spend huge amounts of fuel to brake once you reach your target, and then use more fuel to accelerate to 50% of the speed of light again, keep the speed in spite of all the tiny particles pelting you and trying to slow you down, and then finally using your last fuel to slow down and come to a safe descent on the Earth? How much fuel would it take? Seriously, people. That kind of thing isn't possible.



This spaceship is having no trouble making a U-turn in space. In real life, this would be an extraordinarily fuel-consuming move.

Therefore, you might go to Alpha Centauri if you travel slowly, spend as little fuel as possible and allow your journey to take at least a thousand years. But if you travel that slowly, you can not go home again. The time and the people you knew will be buried in the dust of time long, long before you even reach your target.

And that's why you can't go home again.

Ann

P.S. Would it be possible for baby Kal-El to travel to the Earth in a space ship? Yes, if he was put in suspended animation. Would it be possible for Zara and Ching to locate Clark on the Earth and travel there to get him? Only if they arrived after a virtually immortal Clark Kent had already lived for centuries on the Earth (so they wouldn't be able to meet thirty-year-old Clark Kent). Would they be able to bring him to New Krypton to prevent a civil war there? No. The civil war would be long over when they arrived on New Krypton. Could Clark go home again? Yes, but he could never return to the time he had left behind.

The other thing worth mentioning about wormholes is that they're called that for a reason; there seem to be good reasons to believe that if they exist at all, they're microscopically small -- As in the width of a photon or two -- or collapse within microseconds of being formed.

Thanks for posting such a detailed and well-informed post. Since my science knowledge is primarily based on reading science fiction novels, it was particularly helpful.

Of especial interest is the fact that I'm currently beta-ing a fic for Bobbart, who's basing it on "All Shook Up", the episode about the Nightfall asteroid. Bob is treating the event with much more scientific rigor. I'm learning a lot just by beta-ing.

Alas, if you put in too much rigor, it's hard to write the story. Not to say that it can't be done, and done well - I particularly remember books by Hal Clement ("Mission of Gravity" comes to mind), Robert L. Forward ("Dragon's Egg", "Camelot 30K", and many others), and Poul Anderson ("Tau Zero", where his protagonists travel in a ship so near the speed of light that time slows and they make it to the end of the universe, a particularly bold concept that had me applauding) Plus, in "Tau Zero", if I recall correctly, some of the main characters were Swedish.

But here in our little L&C world, we just have to go with the flow and suspend our disbelief. Alas if you know too much and find it hard to suspend!

So in Corrina's excellent "Awaken My Heart", where Clark & Lois travel from New Krypton to Earth in a spaceship - yes, I see your concerns (you've just detailed them!)

So it's time to break out the champagne and just christen the spaceship the NKSS Plot Device.

And thanks for making such a great post that inspires such comments!

Just an afterthought: Star Trek and Stargate SG-1 wouldn't be here if it wasn't for fictionalized wormholes!

Artemis

Iolanthealias said:

Absolutely! So let me tell you a little snippet about myself. I read my first Superman comics back in 1968, but it was in 1969 that I became a die-hard Superman fan. That was because I read a comic where Superman proposed to Lois Lane, and he seemed absolutely serious about wanting to marry her! Wow!

But would you know that in the same year, 1969, I also became totally enchanted with space for the first time? I saw the movie 2001: A Space Oddyssey, which totally wowed me with its magnificent portrait of the grandeur of space. So the thing is, I have been a Superman fan (or a Lois and Superman/Clark Kent fan) and a space buff for almost forty-one years! That's why both Superman and space matter greatly to me. And that's why I prefer fics where the awesome splendour of space is treated with, well, let me call it respect.

But I completely agree with Artemis that there is so much popular science fiction that would be just impossible if you don't suspend your disbelief and accept the (totally faulty) concept that travelling far and fast in space is a piece of cake. I used to be a die-hard Star Trek fan, too, mostly because I was fascinated by Mr. Spock. Even though I knew that all that talk about "warp speed" was nothing but a load of junk!

I have so enjoyed Corinna's fic, which is a brilliant take on LnC canon. Also, her portrait of "mind-wiped" Kal-El on New Krypton is amazing! Brava!!!!!

Ann

P.S. Artemis, you now have 1313 posts. To my astro-mind, 1313 means galaxy NGC 1313, which is a very pretty and fascinating galaxy, in my opinion. So for today, I'm going to call you Galacto-Artemis!

NGC 1313, or Galacto-Artemis

Thanks, TOC. That is a very pretty galaxy. BTW, I'm in awe of all the new photos from the Hubble after its repair.
Thinking more about wormholes and science fiction, I think the human imagination is much wider than reality.

Artemis
"It only Herz for a little while."

Wow! Ann!

You've just convinced me that I did the right thing in not even attempting to explain how Lois got to NK and how Lois and Kal got back.

Simply put, I could not have written what you did - an understandable, clear, scientifically-sound argument. (Not suggesting I would argue it was possible, because clearly, it wasn't).

My question to you was ... IF we can accept that Lois got there within a short period of time, why can't we accept they Lois and Kal got back?

I do understand that it is totally outside the realms of possibility - but hey, FoLCs write about a lot of things that aren't possible.

However, that doesn't mean you should stop pulling us up when less-scientific writers such as myself cross the line of believability.

Thanks, Ann for putting such effort into an answer. I learnt a lot - not only from this post - but also your other FDK.

Corrina.

Hmmm. I've been working a bit more on my first post to try to improve it, and I wanted to talk a bit more about the friction exerted by space if you travel fast enough. I tried to insert another picture, but it turned out I wasn't allowed to, because I'm only allowed eight pictures per post.

Oh well. So I'll add the extra snippet of information here, then. Maybe somebody will enjoy it!



This is a picture of a star named Mira. Mira is about as massive as our own Sun is, which means that it weighs about 300,000 times as much as the Earth does. But unlike the Sun, Mira is a cool red giant, monstrously puffed up.

For some reason, Mira is speeding through space. It's moving ahead at about 461,000 kilometers per hour, or 291,000 miles per hour. Bear in mind that the speed of light is about 300,000 kilometers per second, or about 186,000 miles per second. If I did the calculations correctly, this means that Mira is speeding through space at about 0.004% the speed of light. That is fast, but not fast enough if you are a short-lived human being who wants to travel far and fast in space. Assuming I did the calculations correctly, if you travel at 0.004% the speed of light, it will take you about 232 years to travel a single lightyear in space. Not very impressive.

Still, even though Mira travels at "only" 0.004% the speed of light, it nevertheless creates its own "bow shock" in space, a crescent-formed shock front ahead of itself. This bow shock is made up of all those tiny particles it collides with in space, plus some of its own puffed-up atmosphere. Still more impressive, Mira has left behind a wake or a tail of particles that is thirteen lightyears long!



The full extent of Mira's tail.

For comparison, this is an image of the bow shock and tail left by a speeding bullet on the Earth. But the bullet moves far more slowly than Mira, at least a hundred times slower, I think. I found an answer on the web saying that a bullet moves, at best, 4000 feet per second. Have fun figuring out how much that is in miles per hours.



In the picture of Mira its tail and bow shock are blue in color. In reality both tail and bow shock would be invisible to the human eye. Both glow in the far ultraviolet, which is an energetic form of radiation that is harmful to the human body. The ultraviolet light is caused by the violent collision between the speeding star and the particles it encounters in space.

So you can see that you are going to have problems with the tiny particles that suffuse our galaxy (the so-called "interstellar medium") if you want to travel at speeds that are even close to the speed of light!

Ann

2,727.3 mph. Also 4000 fps is 3.57 times the speed of sound at 1 atm. That's why you hear the crack of a bullet being fired. Superman need only go about 1120 fps for us to hear his sonic boom. (This varies with temperature and altitude, but 1120 is the standard number used for the speed of sound on earth. It decreases with altitude; in other words you can break the sound barrier at slower speeds).
Yes, I think this shows the attraction of the concept of wormholes through space to travel anywhere. Friction is negated. Too bad they aren't real! Interesting discussion.

Artemis