Abdul Wahab - science4fun

Black holes are one of the most interesting objects while studying astronomy. They were once considered as objects of science fiction. But today, they are a reality and one of the mysterious objects in the universe.

What is a Black Hole?

Black holes are objects in our universe that are known for their very strong gravity. The gravity of a black is so strong that no object (e.g. stars) or light can escape from it. They are very massive objects that have a mass of 10 times to a few billion times the mass of our Sun.

The thing that makes black holes to have a very strong gravity is its compactness. All the matter in a black hole is compressed so much that it only occupies a very small point in space, also called the singularity.

Formation of Black Holes

There are several ways in which black holes are formed. But most of the black holes are formed when a large star dies. When a large star consumes all of its nuclear fuel, it starts to collapse. Then suddenly it bursts into the universe’s most powerful explosion, called a supernova.

After the supernova, the remaining core of the star undergoes a sudden collapse due to its own gravity. The matter is compressed so much that its density reaches to infinity at the center, and a black is formed. Due to infinite density, the gravity at the center of black becomes infinite and is called a singularity. You can consider singularity as a single point with infinite density and gravity where the laws of physics, as we know them, breaks.

Properties of a Black Hole

Black holes can’t be seen directly with naked eyes or telescopes, because light can’t escape its immense gravity. Scientists find black holes by observing light and objects that surround it. Black holes are perfect spheres and are featureless objects. But they may have a charge which is found when a black hole repels like-charges and attracts opposite charges.

Event Horizon

Black holes are dark and they can have various sizes, e.g. some are the size of a city while larger ones can reach half the size of our solar system. The size of a black hole is actually the size of its event horizon. An event horizon is the defining boundary of a black beyond which nothing comes out of a black hole. Moreover, beyond the event horizon, our laws of physics break and scientists are still unaware what could be inside an event horizon?

Facts

The largest black hole in our universe has a mass of 66 billion times the mass of our Sun.
Stephen Hawking has found that black holes also emit certain radiation called Hawking radiation. Due to this fact, black holes have a limited lifespan and they also evaporate.
Supermassive black holes have the mass of several billion times the mass of our Sun. It is considered that supermassive black holes are present at the center of galaxies.

Asteroids were first discovered in 1801 and since then, there have been over 150 million discovered asteroids measuring over 100 meters in size. The first asteroid to be discovered was Ceres which is also the largest asteroid in our solar system.

What is an Asteroid?

Asteroids are the solid objects mostly made of rocks and metals. They are irregular in shape and have varying sizes from a few meters to a few hundred kilometers. Asteroids in our solar system mostly orbit around the Sun and are different from comets, moons, and planets.

Most of the asteroids in our solar were formed along with the formation of the planets around 4.5 billion years ago. Due to this reason, asteroids can be studied to find the condition of the newly born solar system.

Composition of Asteroids

There are various types of asteroids that are in different parts of the solar system. So their composition also varies between rocky, icy, and metallic. Most of the asteroids have rocky composition along with metals. There are also many asteroids whose surface is covered with ice. The ice can be made of various substances, e.g. water, carbon dioxide, and ammonia.

Types of Asteroids

Asteroids can be categorized in various ways, e.g. according to their size, color, and composition. But according to their composition, there are 3 main types of asteroids which are carbon, metallic, and stony asteroids.

Carbon Asteroids – These asteroids are black in color due to the high percentage of elemental carbon; they contain around 75% carbon.
Metallic Asteroids – Most parts of these asteroids are metallic along with some rocky surfaces. There are various metals from which they are formed, but most common are iron and nickel.
Stony Asteroids – The major constituent of these asteroids is silica, also called silicon dioxide. It is the same silica that makes sand on the Earth on which you step-on.

Where Asteroids are Found?

Individual asteroids are found throughout our solar system. But, the majority of the asteroids are found in the asteroid belt. The asteroid belt is an orbit around the Sun that is located after the Mars and before the Jupiter. It is estimated that the asteroid belt contains around 2 million asteroids that are larger than 1 km in size.

There are also asteroids that are near the Earth and are called Near-Earth Asteroids (NEAs). NEAs pass closely to the Earth and there are around 14,000 known NEAs.

What are Meteoroids, Meteorites, and Meteors?

Meteoroids are different from asteroids in many aspects and are relatively smaller in size. Most of the time, they are smaller pieces that are torn from asteroids and comets. Meteoroids have various sizes that range from 10 micrometers to 10 meters. Our Earth is constantly hit by these objects that burn in the atmosphere.

Most of the meteoroids that hit the Earth are completely vaporized in the atmosphere and are called meteors. They vaporize because of the intense heat produced by their friction with the atmosphere due to higher velocities. Meteoroids enter the Earth’s atmosphere at the speed ranging between 10 to 70 km/sec. But very few meteoroids survive the intense heat and successfully reach the Earth; they are called meteorites.

Facts

There are asteroids that share their orbit with larger planets and are called Trojan asteroids.
When an asteroid or piece of it enters in the atmosphere of the Earth, it is called a meteoroid.
There is a theory about dinosaur extinction which says that dinosaurs became extinct after a large asteroid, around 10 km in diameter, hit the Earth.

Meet one of the smallest animals, the tardigrade, one of the most resilient and toughest animals found on the Earth. Tardigrades are very famous for surviving almost all the extremes conditions, e.g. space, volcanoes, high pressure, dryness, hot, and cold.

What Extreme Environments Tardigrades Can Survive?

There have several reports from many scientists that, tardigrades have been spotted in hot boiling water of natural geysers and highly cold environment of Antarctica at around -40 °C. Scientists have even sent the tardigrades to the moon and still think that tardigrades have many chances of surviving at the moon.

They have very special abilities which allow them to survive without water for more than 120 years. They have been tested to survive the hot temperatures up to 151 °C and cold temperatures up to -272 °C (near absolute zero).

Scientists even think that they have survived the past global mass extinctions which includes meteorite impacts, high energy bursts of gamma rays, and several other astrophysical events of the past.

How Tardigrades Survive Extreme Environments?

Tardigrades gain the ability to survive extreme environments by bringing some transformations in themselves. When they encounter extreme conditions, they change state from normal to cryptobiosis; also called death-like state. In this state, their metabolic activity (life-sustaining chemical reactions) drops to an undetectable level. Further, their body turn curls and becomes dehydrated for protection purpose.

The tardigrades get to their normal state when environmental conditions become favorable and they somehow get hydrated again.

What Do They Look Like?

tardigrade-image-from-scanning-electron-microscope — Image of a tardigrade taken by an scanning electron microscope.

Tardigrades are categorized as micro-animals and their average length is around 0.5 mm. They are so small that you can’t see them without a microscope. Their body looks similar to household worms, but they are different from them. They have 8 legs and each of them have claws at their feet for moving on various surfaces. The body of an average-sized tardigrade is roughly made of 40,000 cells. Also, there are a few species of tardigrades whose length can reach up to 1.2 mm and they have large number of cells.

Diet

Tardigrades mostly depend on fluids coming out from moss, lichen, and algae for their food. There are few species that are carnivores that can even survive on other living organisms or can kill other tardigrades for food.

Habitat

tardigrade-in-water — Tardigrade in water under a microscope

Tardigrades are one of those living things that are found across the whole Earth. They are living in Antarctica, deep oceans, high mountains, volcanoes, cities, and forests etc. They can survive almost any environment, but they mostly love to live in wet environments; because they love water! The most likely place of their occurrence is near mosses and algae.

Interesting Facts

In 2016 a report was published in a science journal that described the successful revival of 30 years old tardigrades that were in cryptobiosis state.
There are more than 1,000 species of tardigrades; some of them have eyes, while others have no eyes.
The other names of tardigrades are moss piglets and water bears. They got these names due to their resemblance with bear and piglet.

Radioactivity is a very famous term in nuclear physics and chemistry that describes how unstable atoms release certain radiations for the purpose of getting stability. You may have probably heard about uranium, a radioactive element, used for making atomic bombs and electricity from nuclear power plants. It is possible due to the radioactive nature of uranium.

What is Radioactivity?

Radioactivity is a natural phenomenon in which atoms of elements that have unstable nuclei (nuclei = plural of nucleus), disintegrate for getting stability. There are 3 main reasons behind an unstable nucleus in an atom. These reasons are:

higher number of protons
higher number of neutrons
higher energy of the nucleus

When an element decay, it can change from one element to another for achieving stability. Sometimes when an element decay, it doesn’t change from one element to others but simply gets stability by releasing extra energy in the form of gamma rays.

Isotopes

periodic-table — Periodic table of elements

There are around 118 known elements that differ from each other by the number of protons in their atoms. For example, hydrogen has 1 proton and helium has 2 protons. The nucleus also has neutrons which when change in an element, creates a new isotope of that element.

Isotopes of an element have the same chemical properties, but they differ only in weight due to a difference in the number of neutrons. For example, hydrogen has three isotopes; protium, deuterium, tritium. These isotopes differ from each other due to a difference in the number of neutrons, while the number of protons remains the same. Elements from hydrogen to bismuth in the periodic table have at least one stable isotope. But, elements after bismuth have no stable isotope; they are all radioactive.

Types of Radioactivity

Radioactive isotopes of elements can emit 3 three types of radiations known as alpha rays, beta rays, and gamma rays.

Alpha rays – Alpha rays are positive charged particles that are composed of two protons and two neutrons (also called nuclei of helium). Alpha rays have a positive charge due to the presence of protons; the positively charged particles.
Beta rays – Beta rays are the streams of negatively charged particles, e.g. electrons, or positrons.
Gamma rays – Gamma rays are neutral and are different from alpha rays and beta rays because they are not made of matter particles. Instead, they are high energy electromagnetic radiations; a form of light that is very energetic and can’t be seen with naked eyes.

Half-Life and Measurement of Radioactivity

A sample of a radioactive isotope of an element decays continuously at a fixed rate until the whole material has change into a stable isotope of an element. The term half-life is often used to define time in which half of the sample will turn into stable isotope. For example, the half-life of carbon-14 is around 5,730 years. It defines, if you place 1 kg sample of carbon-14, half of the carbon-14 will turn into a stable isotope in around 5,730 years.

Radioactivity and Human Health

Radiations from the decay of radioactive isotopes are not considered good for health due to several dangers involved in it. For example, when these radiations act on the human body, it damages the DNA and structures of cells. This results in the production of cancerous cells in our body and ultimately make a person very sick.

Facts

Radioactivity was first discovered by Henry Becquerel while working on an ore of uranium element called pitchblende.
Not all radiations are bad! We use X-rays to take photographs of the human body’s inside for detecting any damage or diagnosing some diseases.
Gamma rays are very penetrating radiations, they can easily penetrate through 1 meter thick wall of concrete – much like visible light penetrates through a transparent glass.

Organic chemistry is one of the most famous branches of chemistry that you may have heard in your chemistry classes. It is most of the time considered to be a branch of science that deals with molecules involved with living things only. In fact, it is a much broader field and covers many compounds that are not directly linked with life.

What is Organic Chemistry?

Organic chemistry is simply a branch of chemistry that deals with compounds that contain carbon atoms. In other words, the whole organic chemistry revolves around carbon due it is unique properties. Some of the examples of organic compounds are plastics, oils, gasoline, rubbers, and cellulose, etc.

Organic Compounds

Organic chemistry covers a variety of organic compound types, some of which are hydrocarbons, alcohols, aromatic compounds, ketones, and aldehydes. There are also many compounds that contain carbon atoms but they are not classified as organic compounds. For example, carbon dioxide, carbon monoxide, and sodium bicarbonate.

One of the most famous types of organic compounds is hydrocarbons. Hydrocarbons are the type of organic compounds that contain only carbon and hydrogen atoms. There are 3 main types of hydrocarbons, which are alkanes, alkenes, and alkynes. The gas that you use for cooking is methane which belongs to alkanes.

Organic compounds and processes involved in them are also the basis for life. Some of the types of organic compounds involved with living things are nucleic acids, proteins, lipids, and carbohydrates.

Why Carbon Is Important?

Carbon has the ability to make chemical bonds with four elements, or with itself and three other elements. Due to this reason, carbon can form a wide variety of small and long compounds. It can even form very long compounds, known as polymers, which can contain 50,000 atoms or more in a single compound. Carbon is also the building block of life, which is also the second reason for its importance. There is no life-form on the earth including microorganisms that don’t contain carbon.

Facts

Carbon atoms constitute around 18% of our bodies.
DNA is an organic compound and is a very long chain of atoms. There are billions of atoms that constitute a single DNA compound.
Diamond is a form of elemental carbon, but its atoms are arranged in such a way that it becomes transparent, hardest, and of course expensive object.