This is in continuation of Time Travel.

In the previous post, I explained the consequences of using a time machine. However, there's a bigger problem than that. The machine can only travel in time, not space.

Which means, even if we travel in time, we will be on the same spot in space. Therefore, our initial position (from where we travel in time) and our final position (where we arrive after traveling in time) will be different. How different?


The Earth rotates from west to east.

The equatorial circumference of the Earth is 40,075 km. (Source)

That means, if we're on the equator, we travel 40,075 km (in space) every day, just because of the rotation of the Earth. (From this point forward, let's assume the person who is going to travel in time does so on the equator.)

Number of minutes in one hour is 60, and number of hours in a day is 24. So, in a minute, (if at the equator) we travel x km.

x = 40,075 / 24 * 60
x = 40,075 / 1440
x = 28 (approximate value)

So, if the person travels one minute in the past, he will be 28 km west of his initial position (because the Earth rotates from west to east)

But wait. That's just the tip of the iceberg. Not only does the Earth rotate continuously, it also revolves around the sun.



The circumference of Earth's orbit around the sun is 940,000,000 km (940 million) (Source)

The Earth covers this distance in 365.25 days. (Source)

So, in a minute, the Earth travels y km.

y = 940,000,000 / 365.25 x 1440
y = 940,000,000 / 525960
y = 1787 (approximate value)

Put it all together and, in 1 minute, if your position in space remains constant,



where,


So, to overcome this problem, the time machine would also have to travel in space. Therefore, a time machine would also have to possess the ability to teleport us.

Special thanks to Harshvardhan for helping me conduct the research.

A lot of people are talking about time travel and it is one of those things that people believe would be possible in the coming future. Well, I'm no scientist. So, I don't know if it is possible scientifically. However, let's assume that it is possible and that a device capable of time travel was made.

What then? Well obviously, it has to be tested. But, how will that be done?

Two options; going into the past, or going into the future.

Let's assume Dr. T invented this device that is capable of time travel. And let's say Dr. T wants to test it by going into the past. However, he knows the consequences of messing with the past. So, he decides to just go 5 minutes back into the past, just to see if it works.

To make this post less complicated, I'll refer to Dr. T of the past as Dr. U.

If Dr. T went 5 minutes into the past, he will see Dr. U pondering over what to do with the machine. And, if he waits for 5 minutes, Dr. U will also make up his mind to go 5 minutes into the past to test his machine. And this can keep looping.

Unless, Dr. T sends a sign to Dr. U telling him that time travel is possible. That would thus tell Dr. U that his machine works and so, after 5 minutes, he won't use his machine. But, by doing that, the time that Dr. T lived in has changed. It is now a world where Dr. T doesn't go into the past.

So, Dr. T can't return to his present, because there will be another Dr. T there. However, he can't stay in this world either, because of Dr. U.

A possible way to counter this would be to ask a friend for help. Let's call him Mr. X.

Now, before Dr. T goes into the past, he tells Mr. X to kill Dr. T after he sends a sign to Dr. U. Thus, if Dr. T dies in the past, Dr. U can live on to be Dr. T and know that the time machine works.

To make things easy,

At 13:15, Present,

Dr. T: Mr. X,  at 13:20, I'll travel back in time (to 13:15) and send Dr. U a sign. As soon as Dr. U gets that sign, he'll tell you. After you find out, look for me in this room, and kill me.

At 13:20, Present,

Dr. T travels back in time.

At 13:15, Past,

Dr. U: Mr. X,  at 13:20, I'll travel back in time (to 13:15) and send Dr. U a sign. As soon as Dr. U gets that sign, he'll tell you. After you find out, look for me in this room, and kill me.

Now that Mr. X knows he has to kill Dr. T, Dr. T sends the sign.

At 13:16, Past,

Dr. U: It worked. Time travel is possible.

Hence, hearing of the success, Mr. X goes to the room to kill Dr. T.

At 13:20, Past,

Dr. U is confident time travel works. Mr. X has killed Dr. T. And Past is now Present.

So, just to check if time travel is possible, scientists will have to do this much thinking. And, the scientist that travels time will have to die, and let his "clone" take over.

But, what if the experiment was to travel in the future?

Going into the future is, as you'd imagine, the opposite of going into the past. The main problem with going into the past is having a clone of you. However, when you travel into the future, for the period of time you skipped, you didn't exist in the world. So, without raising any concerns, you can only travel short distances of time (in the future).

So, if Dr. T goes into the future at 13:15, and he goes to 13:20, he will have to come back to the present between 13:15 and 13:20. But, that means, travelling in the future is quite easy.

However, let's assume Dr. T lives in the year 1900 and travels 100 years into the future.

In 1900, Present,

Dr. T goes into the future.

In 2000, Future,

Dr. T sees a mobile phone and decides to bring it back with him.

In 1900, Present,

The mobile phone is now in this year. Which means, the future of the world has changed. The future that saw the invention of the phone has changed. And so, theoretically speaking, the phone that Dr. T brought back doesn't exist anymore.

So, as you can imagine, time travel is quite paradoxical. And so, I hope they never perfect it. Because, there's no saying how a small change in the past might factor into the world that we live in today. 

A friend of mine had written a program that would balance chemical equations. I didn't want to copy her, nor did I think I'd be able to write such a program so I decided to start with a simple quadratic equation solver.

I just wish I had done this before solving 100s of them as homework.

Right now, it can only solve them using the factorisation (or splitting the middle term) method. But, other methods will be added soon. Here's a demo.

If you could select one superpower, what would it be?

It's been a very interesting question, asked a lot in Facebook groups or on pages.

For the sake of keeping it short, let's only consider controlling the 4 main elements of nature; air, earth, fire and water.

When you think about it, each of these elements can be destructive, and constructive. Air contains oxygen which is necessary for living, on the other hand, too much of air (cyclones/tornadoes) can be destructive. Water is a necessity for most living things, but then, too much water, in the form of a flood or tsunami, is destructive. Earth is a surface that we can walk on. Without it, we would just keep falling. Actually, we would just float in air, but that's a topic for another day. However, "faults" in Earth can lead to earthquakes which can result in tsunamis and floods.

But, when you consider fire, you realize that fire can cause destruction even if it's in a small quantity. Fire spreads and even a small fire can turn into a huge one and ultimately burn cities to the ground. Which is why, in my opinion, fire is the most destructive.

However, that's not the only reason for choosing fire. If you think about it, earth, water and air are necessities, fire is a luxury (read the third paragraph). Of course, you can't cook without fire, but, cooking itself is a luxury. We can eat raw fruits and vegetables, we'll still get the necessary nutrients. But, we want a better taste, so we cook it, hence, fire is a luxury. Fire also provides warmth, another reason why it's a luxury. Fire is the reason we can drive vehicles, another luxury.

Even if you look at it from a mythological point of view, fire was always held in high regard. Prometheus was a Titan (Greek mythology) who was known to give several gifts to mankind. One of them was the nourishing part of cows (or beef). But, all of this went unpunished by Zeus, the King of Gods. However, when Prometheus stole fire from Mount Olympus (the residence of Gods) and gave it to mankind, Zeus eternally punished Prometheus. Fire was God's greatest gift to humanity.

But, the uniqueness of fire remains constant throughout the argument. If I was to possess the power of controlling water, I would be able to breathe and stay dry underwater (by controlling the water in a definite way). If the element in question was earth, I would still be able to change the hardness of the earth to survive a fall (though the fall itself might kill me). Similarly, controlling the air, I would be able to fly, and remain unharmed in a hurricane etc.

But fire is a tricky element. No matter how precise I am with controlling fire, if my body isn't immune to heat, I wouldn't be able to effectively use fire. Because, just being near a fire is enough to feel the heat and if my body can't withstand it, controlling the flame is a useless ability.

So, if I was to choose a superpower, I wouldn't choose controlling fire. However, if I was to choose two superpowers, I would choose controlling fire and immunity to heat.

Which element would you like to control?

"Memory of an elephant" is an English proverb that means really good memory. I was a bit curious about it so I looked it up on the Internet.

Turns out, it has scientifically been proven that elephants have really good memory. (Source) But, after reading about elephants, I started reading about spiders (I don't know why)

It's been an urban myth, I guess, that a spider's legs are immune to adhesion i.e. a spider's legs can walk on sticky surfaces (webs) But, after just a minute of reading, I understood that it's not the case. A spider isn't immune to adhesion. Spiders just have the option of making sticky web and normal web.

That means, the spider remembers which part of the web is non-sticky and treads only on that part.

Even in your house, if you see a cobweb, what do you do? You remove it and kill the spider if it's nearby. But if he's not, he will weave another web and he'll have to remember which parts of it are sticky.

And that's just a common spider. Bigger spiders that live in forests weaves HUGE networks of webs and they still know which part is safe to walk on.

According to the article on elephants, one elephant remembered another one for 23 years even though they were together only for a few weeks. It's safe to say that an elephant's memory span can go up to 30 years. And according to the same article, an elephant's lifespan is 50 - 60 years. Also, elephants can keep track of around 30 companions at once.

Now, a common garden spider lives for 1 - 2 years and will remember about his webs for all his life. Bigger spiders like tarantulas live for 25 years or so, and they will remember about their webs for all their life as well.

I really hate it that the proverb is "memory of an elephant", when it could've been a number of other animals. I just happened to read about spiders and find out that they have an excellent memory as well.