The String theory

What is string theory?

But before starting this article one thing must be kept in mind that there exists a possibility for an unproven theory that 100% of it could be wrong. But then one would think that why are we reading it anyway. The simplest reason is that once every great discovery had been a theory.

Introduction

Imagine you’re holding something in your hands like a rope. What is it made of? You would say that it depends upon the type of rope we are talking about like jute, plastic or whatever but what is that made up of. Magnifying the idea very closely we can say molecules. But what are molecules made of – atoms. And on dividing atoms we can find even smaller particles, elementary particles; the electrons, neutrons, protons. And only a few years ago we have become familiar with the fact that even elementary particles are divisible. Quarks or leptons make them up. And that is where our idea stops. We can see any object because it reflects light but anything beyond quarks get so small that for the light waves it is not possible to touch them and get reflected back. Light just passes over them. That is why we cannot see them. This is the reason people believe that quarks, the elementary particles which make the electrons, neutrons and protons are the most fundamental particles of the Universe. But to some physicists it is the same belief like the one which used to be that an atom is indivisible. But here we are. They say that even quarks are made up of something and that is where the idea of string theory turns up. The string theory says that inside a quark you might find a little string of energy. That string might be closed, open, stretched or like a loop or something constantly vibrating. And the pattern of those vibrations is what that makes particles or we can say differentiate one particle from another. 

In the above image you can see that how a different manner of vibration makes different particles.

 

 

 Like as Professor Brian Greene of Columbia University says that these vibrations are same as those vibrations produced by a guitar string. But rather, as the guitar vibrations produce musical notes; these strings on the other, hand create particles. For example, the neutrino is nothing but a closed string vibrating in a different manner than an electron.

Scientists like Hawking and Einstein all throughout their lives tried to find the theory of everything and this string theory can be considered to be the basis of that.

 

Mediating particles

 

Have you ever wondered about “forces” that act between particles? I mean like there are four fundamental forces, but what factor cause these forces. Are there any particles which make these forces happen? Yes, all the forces that exist in nature whether strong or weak are carried by particles. These particles are known as mediating particles. The mediating particles for the four fundamental forces of nature are –

Fundamental forces	Mediating particles
Strong nuclear force	Gluon
Weak nuclear force	W,Z Boson
Electromagnetic forces	Photon
Gravitational force	Graviton (hypothetical)

Photon, the mediating particle of EM forces was earliest to be discovered in 1905 by Einstein. While the Bosons are the latest to be discovered, named after the Indian scientist S.N. Bose.

Superiorities

The main target of this theory is not to justify the fundamental nature of matter but to establish a relation between quantum gravity and general relativity. And if we can join the laws of general relativity and quantum mechanics, it will give us the theory of everything. The Universe then will no longer be a mystery. But what exactly are we talking about these two things –

Quantum mechanics – This is the set of mechanism for particles or matter at the atomic or molecular level dealing with particle physics. As far as we know, all four fundamental forces work everywhere in the Universe (leaving exceptions aside like black holes), even at the quantum level but not gravity. Any theory had never been able to prove or notice gravity at quantum level. So in knowledge of our intellect quantum gravity does not exist.

General relativity – This is an Einsteinian theory (devised by Einstein). Einstein tried to explain and introduce many phenomenons through it and gravitational warp was one of them. Gravitational warp is like a ripple in spacetime. According to relativity, gravity is the curvature in space which causes an object to attract another object. This phenomenon can be understood well from the image below.

In this picture, if you try to imagine the surface as space (or spacetime) you can see well that how a heavier object warps the fabric like spacetime around it to attract a lighter object. This is what causes gravity as per relativity.

So, string theory tries to unite these two theories on the quantum level which is probably one of the most prominent problems of theoretical physics. But the real fact is that it had already combined these two things, mathematically. The thing left to do is to verify it experimentally which is not possible practically. And also, this mathematical derivation was not made possible on the first day of this theory obviously. In the beginning, when the string theory was not working under normal conditions, more dimensions were introduced and the concept of adding more dimensions made the maths completely justified.

Complexities

Now, the question is if this theory is so efficient then what are the odds that stand against it. Like, if the physicists are working on it for decades then why had they never been able to prove it?

We should know that the discovery of quarks was only made possible with the help of the particle accelerator. There is no direct method or any simple microscope kept out there in the laboratories through which we could peep into an atom.

Also, string theory has developed through time based upon different ideologies of different persons. The basic string theory can be proved mathematically but for that to work it will need more than 3 spatial dimensions (the ones in which our Universe works). Yes; 5 models of string theory talk about presence of 10 spatial dimensions whereas the sixth model says that there are 26 dimensions in the known Universe. All these theories altogether are known as the M theory (the term first to be used by Edward Witten).Special theory of relativity talks about time being the 4^th dimension. And this  is what makes the theory complex beyond imagination.

This was the simplest way in which I tried to explain the string theory. I hope  you liked it.

The Absolute Zero

THE ABSOLUTE ZERO

All you need to know about “The lowest temperature possible in our universe”- THE ABSOLUTE ZERO

W

e always hear about temperatures around us or at least we read about them in our books. But one peculiar thing that I noted about them was that on the temperature scale while talking about rising temperatures or hot temperatures they can go as high as a thousand degree Celsius(for e.g. the temperature of the sun is about  5,505°C) or some even infinitely high values. But I never had seen this high variation in case of colder temperatures. I bet for you too that most of you might also have not heard about temperatures much below the freezing point of water i.e. 0°C. The concept of absolute zero is the explanation to this indiscriminant variation between the temperatures below the freezing point (0°C) of water and those above the steaming point (100°C) of water.

What exactly is it?

The temperature of -273.15°C (0°K) is called absolute zero. It is the lowest temperature possible in our in our universe. This means that it cannot get colder than -273°C. Sir William Thomson, 1^st Baron Kelvin first discovered about it in 1848. He set absolute zero as 0 on his temperature scale to get rid of the negative values as present in Celsius scale. This is how he invented the Kelvin scale (as we call it now).

According to Lord Kelvin, heat is just the movement of particles or we can say molecules moving around in a substance. So absolute zero, according to theory, is a condition when molecules stop moving. But mathematically, this cannot be proven. When the speed of the particles at the molecular level gets very low because of the decrease in temperature (kinetic energy of a particle is directly proportional to its temperature) there is still some heat around which keeps it moving. Also according to Heisenberg’s Uncertainty principle we cannot know both a particle’s momentum and position at the same time. But if the temperature of a particle has to be absolute zero then this would mean that its motion will be zero. So its momentum (p=vm) would also be zero and hence its position and momentum will be known at the same time. But this defies the condition of Uncertainty principle. This means that the condition of true -273°C (0°K) is not possible but it is possible to reach really close to it like a billionth of a degree away. But that one too is not an easy thing to accomplish. And the journey along that is quite long. Let’s see:

How the journey around decreasing temperatures leads us to absolute zero-

SUBSTANCES\PLACES	TEMPERATURES
Freezing pt. of water	0°C
Avg. winter temp. of Canada	-15°C
Freezing point of Mercury	-38.7°C
Avg. surface temp. at Moon during the day	-53°C
Avg. surface temp. at Mars during the day	-63°C
Sublimation point of Dry ice (solid Carbon dioxide)	-78.5°C
Coldest surface temp. ever recorded on Earth	-89.2°C
Freezing point of Chlorine	-101.8°C
Freezing point of Ethanol (alcohol)	-114.14°C
Oxygen liquefies at	-183°C
Nitrogen liquefies at	-196.8°C
Freezing point of Nitrogen	-210°C
Freezing point of Oxygen	-223°C
Hydrogen liquefies at	-253°C
Freezing point of Hydrogen	-258°C
Helium liquefies at	-269°C
Avg. temp. of Universe	-270.28°C
Temp. of first ever created Bose-Einstein Condensate (fifth state of matter)	170nK
Lowest temp. artificially created	1pK
Absolute zero	-273.15°C

The above table shows how lower we have to go in order to reach absolute zero. As we go on decreasing temperatures, rate at which chemical reactions happen is slowed down significantly or either stopped entirely. Below 200°C only 3 gases of 3 liquid elements remain unsolidified. Every element except that is in solid state. Unprotected exposure of temperatures at this level is highly lethal to humans. When we reach -250°C conditions become so extreme that almost all chemical reactions are completely halted. Movement for even particles becomes difficult. Only two gases remain that are not solidified. Also, the surface temperature of the minor planet 90377 Sedna is -261°C which makes it the coldest body in our solar system though it reaches that temperature once in every 11,000 years as it is its orbital period. At 272.2 degrees below zero every element is frozen and any chemical reaction is not possible. And even going lower after that, there comes the absolute zero. At this condition movement for any molecule, element or even an atom is not possible. Everything stops here but as we have discussed above, again this condition is not possible. The things that are possible is what we saw in the table above.

The opposite of absolute zero-

As we now know what is the lowest temperature possible so the question arises is there any highest possible temperature in our Universe or is it just infinite. I mean the temperatures like 5.5 trillion degrees have been created in the laboratories on earth. Though these are generated for a very minimal time but what is the maximum value of temperature possible. Is there any opposite existing value for absolute zero? Actually yes, it is possible. But to understand that you might need to know some things about radiation.

Ø Radiation – Radiation actually is the loss of energy either in the form of waves or particles.This radiation is of different types like infrared, ultraviolet, gamma rays, alpha rays et cetera divided on the basis of wavelength. Scientists can detect wavelengths of the range 2nm-2500nm.  

Now, according to Wien, temperature is inversely proportional to the wavelength of radiation emitted by objects. So if we would keep on increasing the temperature, the wavelength would go on decreasing. On increasing the temperature of the object to 1.41 X 10^32 K which is like 141,000,000,000,000,000,000,000,000,000,000 degree Kelvin, the wavelength of the radiation becomes 1.6 X 10^(-35)m (which is 0.00000000000000000000000001616nm and could not be reduced. Decreasing any length beyond that is not possible. So, there comes the shortest distance possible in our Universe known as the ‘Planck length’. It is not possible to obtain any shorter length than the Planck length. This means the temperature cannot be increased further because the wavelength cannot be reduced, which gives us the highest possible temperature in our Universe.

But even after that one would still wonder how can we not add or provide energy to something. Like, in whichever state something is we could still add energy to it in the form of heat or something else. So if we add more energy to an object even after the condition of Planck length is achieved it would result in the formation of a black hole. And this black hole would be different from the others in the sense that unlike other black holes, this one is not made from mass but from energy. (Generally black holes are formed when a “very X 10^100” large mass is compacted in a very small space, for e.g. the mass of a normal black hole is 3-4 times the mass of the sun present within a diameter of 8-9 km.)  

First black hole photo taken by Event Horizon Telescope