Time Travel (part 2)

In my previous post I described how Time Dilation works (the faster you move through space, the slower you move through time.)  This time round my endeavor is to show how one can use this method to time travel into the future.

In October 1971, Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four atomic clocks aboard two commercial aircraft and flew them around the earth twice. They compared the clocks with two stationary clocks on the ground and found out that the clocks on the planes were 40 billionths of a second slower than the clocks on the ground, just as Einstein had predicted more than 60 years ago. This is a very tiny amount of time but we also have to realize that a commercial plane's maximum speed is only 885 km/h. This is less than 0.000001% the speed of light (1,080,000,000 km/h) which is required to completely slow down time.

Now, if you haven't read my post on Time Dilation I suggest you do that first before you continue further as the stuff below might get a bit confusing.

Let us explore and understand how Time Dilation works for Einstein's theory of Time Travel. Firstly, did you know that we are already time traveling, you, me, at this very moment! Yes, we are time traveling every second of our lives from when we are born until we die! I know this sounds weird but let me explain.

The Earth goes around the Sun at 30 km per second; 30km/s

The speed of light (c) = 300,000 km/s,

Hence, to find out the percentage of the speed of light at which the earth travels round the sun, we calculate thus:

30/300000 = 1/10000   i.e. 30/300000 = 0.0001 or 0.01%

Now imagine someone lived for 30,000 days or 82 and a half years on Earth and his cousin lived on for the exact age on a stationary planet far away (this is hypothetical; no planet has yet been found to be so). Since Earth is moving around the Sun at 30 km/s, the time slows down by 0.01% for people living on the Earth but it will continue its normal course of speed for people living in a stationary planet. We don't realize this is happening as we don't have a stationary planet in the Universe with people living on it. If the imaginary people on the stationary planet could communicate with us we would know that both cousins were exactly 30,000 days old yet the one on Earth lived 3 days longer than the one on the stationary planet because of Time Dilation. The inhabitant of the stationary planet will see this period as 30,003 days if recorded while actually for us on the earth it would mean only 30,000 days.

Some scientists say that if we can build a space ship to orbit a massive object like a star or a black hole at  high speeds, maybe at 150,000 km/s (50% of the speed of light) it can travel through time. Five years on the  space ship will be 10 years on Earth! Scientist are looking for other cost effective ways to do this and the space ship idea does seem kind of unrealistic as you won't go very far into the future and it will probably cost you millions of dollars.

I think we will just have to wait for new discoveries and hope that one day we will be able to time travel into the future. Exciting thought..

Time Travel Part 1

Time Dilation

Before we jump into time travel, we need to understand time dilation. In 1904 there was a big issue on the speed of light:   

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( c = speed of light )

If an observer is moving towards a light beam, he should record c as, c =186,000 miles per second + the speed of the observer. 

If an observer is moving away from a light beam, he should record c as, c = 186,000 miles per second - (minus) the speed of the observer. 

If an observer is moving along with a light beam (in the same direction), he should record that c = 186,000 miles per second - (minus) the speed of the observer. 

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Of course, light can only be observed, it has no other use in the universe and if light is observed to be traveling at more than 186,000 miles per sec, it has has no speed limit. This could ruin the 200 years of research that scientists have been doing on the speed of light and time travel. They would have to start all over again and many theories in physics would be of no use. 

                                          A young patent clerk by the name of Albert Einstein saved the day. He suggested that if observers (moving and stationary) have to agree on the speed, they will have to disagree on time. Which means time will be running at different speeds for different observers. I know this sounds weird but I will give you an example and try my best to explain what Einstein said. 

                                           Let's say we have a spaceship A that is stationary in space while another spaceship B is moving at 93,000 miles per sec (half the speed of light). The spaceships are parallel to each other. Spaceship (a) is stationary at point (c) and 12 light seconds away is point (d) (light second means the distance light travels in one second; 186,000 miles). The halfway line is 6 light seconds away. (click on the diagram below)

When spaceship (b) approaches point c, both spaceships fire a light beam and spaceship (b) continues to go forward. When the light beams reach point (d), Spaceship (a) records that light travels 12 light seconds in 12 seconds; 1 light second per second. Correct.

{ Normally, observers will disagree on the speed of an object. For example, imagine you are traveling on a highway at 80 mph and a car traveling at 100 mph overtakes you; To a person standing at the side of the road, the car will be traveling at a 100 mph but for you it would be only 20 mph because you are already traveling at 80 mph. } 

                                                       So what about spaceship (b)? It is moving towards the light beam (in the same direction), so will it see the light beam go slower? No. This is because time, in spaceship (b), slows down. 2 seconds in the stationary world will only be 1 second inside spaceship (b) because it’s traveling at half the speed of light. When speed is at 0%, time is at 100%. 100% speed is c (speed of light) so when speed is at 100% or 186,000 miles per hour, time is at 0%. 

To sum it up, the faster you move through space, the slower you move through time. So at the speed of light, time will completely stop. Are you with me so far?   

                                                               When spaceship (b) reaches the half way mark, light has reached point (d) (in 12 seconds). Now spaceship (b) will record that light travels at 6 light seconds in 6 seconds; 1 light second per second. Correct. Without time slowing down, spaceship (b) will observe the light beam travel 6 light seconds in 12 seconds and that’s basically why observers have to disagree on the time.

I can give you a brief explanation on time slowing down. Imagine that there is a clock shaped like this, with a top and a bottom. It has a light beam reflecting back and forth form the top and the bottom. Each time the light beam hits the top or bottom, the clock advances by one second. 

Now, imagine the clock starts moving in one direction (click the diagram).

Notice that the the light beam will take a longer time to travel between the plates when the clock is moving and time will slow down. This is similar to how time slows down when we move. 

Now, imagine a car going East at 100 mph. It stops, and goes North at the same speed. It decides it wants to go Northeast at 100 mph. When it's going East at a 100 mph, it is going North at 0 mph and vice versa. But when it's going Northeast (the speed is 100 mph), it's going East at 50 mph and North at 50 mph. 

In here, North is represented by space and East is represented by time. The car is an object traveling through space. So again, the faster you move through space, the slower you move through time. This phenomenon is called Time Dilation. Several researches have been done by some of the best scientists in world and they all show that time dilation actually occurs.  

This is the end of part 1. Part 2 will be coming out soon. Please comment and give me your feedback, tell me if I have missed anything.

And the next time you are traveling in a plane or a car, remember this:

You are traveling fast through space but slower through time...

Gravity (part 2), Black Holes

So in my last blog, I talked about gravity and how it affects the Universe. This time, I will be talking about black holes.

What is a black hole? It is a region of space with a gravity so strong that nothing, not even light can escape. Black holes are formed by huge stars that collapse.

To understand how a black hole forms, let's look at the life cycle of a star. A star is formed when a large amount of gas, mostly hydrogen, starts to collapse in on  itself due to its gravitational attraction. As it contracts, the atoms of the gas collide with each other with increased frequency and at greater speeds. As a result, the gas heats up.

Eventually, the gas becomes so hot that when the hydrogen atoms collide they no longer bounce off each other, instead fuse together to form a colossal amount of heat, in the process forming helium. The heat released in this reaction, which is like a controlled hydrogen bomb explosion, is what makes the star shine. This additional heat also increases the pressure of the gas until it's sufficient to balance the gravitation attraction, and the gas stops contracting. The gravity tries to make the star smaller and denser but the heat generated inside the star expands the star. This keeps the star stable.

The star expands slowly overtime (about 13 billion years) until it becomes twice as big. As it gets bigger, it cools down by a few hundred degrees and turns red. A star like this is called a 'red giant'. When a star becomes a red giant, it's inching closer to its death. A star dies when it  has lost all its hydrogen fuel which kept it expanding. Small to medium sized stars like our Sun usually fade away when they have lost all their fuel leaving a small intact core (called a white dwarf). 


Bigger stars are much more dangerous. When a big star loses its fuel, gravity takes over and starts contracting the star. The reason why this does not happen with smaller stars is because smaller stars are not heavy enough to have a strong gravity. As the hydrogen fuel gets over, nothing can stop the star from contracting and the star keeps on getting smaller and smaller. As it shrinks, it gets denser and its gravity at the centre becomes stronger. Usually, when the star is 60 km in diameter, it's so dense that 1 tablespoon of the star would weigh about 2 cruise ships! 


When the star is 30 km in diameter, it becomes so dense that even light cannot escape its gravitational pull. This is when no light from the star goes far enough to be visible and the star is now a black hole. The star continues to get smaller and smaller until it reaches singularity. If a beam of light gets close enough, it will get pulled into the black hole. Anything that gets close enough is sucked into the black hole. A black hole the size of a neutron would weigh about a billion tones! That's really heavy. If one could hold a black hole, it would go straight through the hand and continue to go down through the floor and into the Earth until it reaches the centre.


Thanks for reading this, I will post another blog soon. Please comment 

Gravity

This time I am going to talk about Gravity and how it affects us and the Universe.

Have you ever wondered how and why the Earth orbits the Sun or the Moon orbits the Earth? You might say that the Sun's gravity keeps the Earth on track and the Earth's gravity keeps the Moon orbiting the Earth. But shouldn't the gravity of the Sun just pull the Earth towards it instead of having it revolve around it? Well, this does not happen because Space behaves like a fabric.

Anything that has a mass has its own gravity. Yes I have my own gravity and you too. Even tiny dust particles have their own gravity even though you don't notice it. And when anything has gravity, it bends the fabric of Space. Lets say you have a piece of cloth/paper (fabric of Space) and you stretch it so that it's flat but slightly relaxed at the same time. You then put a ball (the Sun) on top of it and notice how the fabric bends inwards.

This is the similar to what happens in space. No, space does not bend like a fabric, but it acts like it does. All objects bend space forming a gravitational cone, with the object being in the middle. The Sun's gravitational cone is huge, it extends out much further than the Solar System.  An object's gravitational cone depends on the mass (and not the size) of the object.

If the gravitational cone is big enough, the object can have a satellite orbiting around it. The Earth is a satellite of the Sun and so are the other planets in the Solar System. The Sun's gravitational cone keeps the planets in orbit.

Let's say that the Sun's gravitational cone is an actual cone and a ball is going around the centre of the cone. If the ball is going too slow, it will spiral inwards and fall into the centre. If it's going too fast, it will spiral outwards and fall off the edge of the cone. If it's going on a steady pace and not too fast or slow, it will maintain a steady orbit around the centre. The moon maintains a steady orbit around the Earth and the Earth maintains a steady orbit around the Sun. If Earth was going too slow, we would have crashed into the Sun by now!

Gravity is also capable of bending light! Albert Einstein first suggested that gravity bends light.To confirm this, a detailed experiment was carried out by Sir Arthur Eddington in 1919 (during a solar eclipse). The results were analysed, and in 1920, it was confirmed that gravity bends light. What happened in this experiment to prove thus? During the solar eclipse Eddington could clearly see the stars, hitherto not seen due to the overwhelming brightness of the Sun. The eclipse blocks this dazzle to some extent making the stars visible. What Eddington saw, however, was interesting: the stars appeared to be a little more closer to the Sun than their normal position. Why? This was because the light of those stars had bend towards the Sun due to the gravitational pull of the Sun. This phenomenon is called the Gravitational lens of the Sun. All star that are big enough to have a gravity that strong have a gravitational lens.

I will soon create a link explaining through a video how this gravitational lens works.

In all, the Universe depends on gravity and it would be impossible for life to survive without it.

Although the Universe depends on it, gravity can also turn into the most dangerous things in the Universe. These dangerous things are called black holes.

I will talk about black holes in my next blog.

e=mc squared

Hi everyone, this is my new blog. In my blogs, I will be talking about physics as you may have guessed from the title, and I hope this will help you.

Many of you know Einstein's most popular equation, e=mc squared, but do you know what it means? Well, let me tell you what it means. E stands for energy, M for mass and C stands for speed of light (which is 300 million metres per second). What this means is that the total amount of energy an object has is its mass multiplied by the speed of light squared. For example, 2 kg of water will have an enery of : 

2 x c squared (300,000,000 x 300,000,000) = 1,800,000,000,000,000,000, Joules

( A Joule equals approximately the energy of a 1kg text book dropped from a height of 1.5 metres)

That's a lot of energy (enough to blow up 4 or 5 cities)!! Now, you might be thinking how could water have so much energy? Well this is the best way to explain :

• Hydrogen is the basic element which makes all other elements. A hydrogen atom consists of a proton and a neutron in the nucleus and an electron orbiting the nucleus. The process of making other elements using hydrogen is called fusion (that fuses two or more hydrogen atoms together). This process happened in the big bang and still happens in stars that are about to die.
• If you slam two hydrogen atoms together, you will create a helium atom which consists of two protons, two nuetrons and two electrons. If you slam three hydrogen atoms together you will create a lithium atom which consists of three protons, nuetrons and electrons each. The more hydrogen atoms you slam together, the more different types of elements you make, until you reach elements like uranium which have more than 90 nuetrons, protons and electrons.
• Now, if you can fuse hydrogen atoms together to form other elements, you can also seperate other elements to make hydrogen (using a process called fission). Note that in the process of fusion or fission, the matter does lose or gain mass.
• Like I said before, all elements are made up of hydrogen, and therefore one can say that an object that weighs n grams is made up of n grams of hydrogen. (I know this sounds a bit weird but lets all stick to this)!!
• As you know, when a hydrogen atom splits, it creates an immense amount of energy (like what happens in an atomic bomb). An atomic bomb contains about 2 party balloons of hydrogen ( imagine this blowing up a whole city)!! This gives you an idea of the amount of energy hydrogen atoms have.
• Using fission, if you completely convert all othere elements of an object into hydrogen, and blow it up (like an atom bomb), you would find out exactly how much energy that object has (you can call this potential energy).

So, how does that 2 kg of water have that much energy? Refer to the first two paragraphs in case the information was too heavy to stay on!!

Well the composition of water is H2O, so if you take out all hydrogen atoms and convert oxygen back into hydrogen and blow it up, you would find out that the water has enough energy to blow up 4 or 5 cities! Be careful though, stand at least at a 200 km radius or you will be evaporated!!

So now I hope you understand the meaning of e=mc squared.

PS: Despite all this, I am still wondering how Einstein came up with c, the speed of light.

Do write back....I will post another blog soon!