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Ravi Speaks on scientific facts, Ponnur (2026)

10/09/2025

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చంద్రగ్రహణం రోజూ జరుగుతుందా? నెలకోసారి జరుగుతుందా?

ప్రతిరోజూ చంద్రుడు కృష్ణపక్షంలో తగ్గుతూ పోతాడు. శుక్లపక్షంలో పెరుగుతూ వస్తాడు. అయితే రోజూ చంద్రగ్రహణం జరుగుతుందా? నెలకోసారి జరుగుతుందా?

చంద్రుడు రావడం, పోవడం అంటూ ఏదీ లేదు. 'చంద్రుడు' ఓ ఉపగ్రహం. అది భూమి చుట్టూ ప్రదక్షిణం (revolution) చేస్తుంది. తన చుట్టూ తాను తిరుగుతుంది. కూడాను. దీన్నే భ్రమణం (spin) అంటారు. తన చుట్టూ తాను తిరిగేటందుకు పట్టే సమయం, భూమి చుట్టూ ఓ రౌండు వేసి రావడానికి పట్టే సమయం చంద్రుని విషయంలో దాదాపు సమానం. చంద్రుడు, భూమి తదితర ఎన్నో గ్రహాలు, ఉపగ్రహాలు సూర్యుడిలా స్వయంప్రకాశాలు (luminescenst) కావు. చంద్రుడి మీదైనా, భూమ్మీదయినా సూర్యకాంతి పడి అది పరావర్తనం (reflection) చెందడం వల్ల మనకు చంద్రుని వెన్నెల ఏర్పడుతుంది. అంటే చంద్రుని వెన్నెల వెలుగు కూడా సూర్యుని పరావర్తిత కాంతి మాత్రమే! చంద్రుని మీద నుంచి గానీ, మరే ఇతర ఖగోళస్థానాల నుంచి గానీ భూమిని దూరం నుంచి చూస్తే ఇది కూడా పెద్ద చందమామలాగా ఉంటుంది. శుక్లపక్షమైనా, కృష్ణపక్షమైనా చంద్రుడి మీద నుంచి వాస్తవంగా, స్వతహాగా వెలువడే వెన్నెల వెలుగు మోతాదులో తేడా లేదు. చంద్రుడికున్న శాపం వల్ల 14 రోజులు తగ్గుతూ వస్తాడని, 14 రోజులు పెరుగుతూ వస్తాడని చెప్పే పుక్కిటి పురాణాలకు శాస్త్రీయ ఆధారం లేదని, నాడు పరిమిత పరిజ్ఞానంతో కూడిన మానవ పరిశీలన ఆధారంగా ఏర్పర్చుకున్న
నిరాధార నమ్మకాలే అలా ఉన్నాయని అనడానికి చంద్రకళలు (lunar phases) ఓ ఉదాహరణ. చంద్రకళలు ఎలా ఏర్పడతాయి, గ్రహణాలు ఎలా ఏర్పడతాయి అన్న విషయాల తెలుసుకోవాలంటే చంద్రుని భ్రమణ, పరిభ్రమణాల గురించి భూమి భ్రమణ, పరిభ్రమ ణాల గురించి కొంత ప్రాథమిక పరిజ్ఞానం అవసరం.

మనకు సూర్యుడు సుమారు 15 కోట్ల కి.మీ. దూరంలో ఉన్న అతి దగ్గరి నక్షత్రం. మనకు చంద్రుడు సుమారు మూడున్నర లక్షల కిలోమీటర్ల దూరంలో ఉన్న అతి దగ్గరి సహజ ఉపగ్రహం, మన భూమికున్న ఒకే ఒక సహజ ఉపగ్రహం. అయితే ఈ దూరాలు ఎల్లవేళలా నెలపొడవునా చంద్రుడి విషయంలోనూ, సంవత్సరం పొడవునా సూర్యుడి విషయంలోనూ ఒకేవిధంగా ఉండవు. పెరుగుతూ తగ్గుతూ ఉంటాయి. ఇది కొద్దిగా దీర్ఘ వృత్తాకారం (elliptical) గా ఉంటుంది. సూర్యుడు మనకు అత్యంత ఎక్కువ దూరంగా ఉండేది చలికాలంలో కాదనీ, అత్యంత తక్కువ దూరమైతే వేసవికాలంలో కాదనీ మనం గుర్తుంచుకోవాలి. నిజానికి సూర్యుడు మనకు చలికాలంలో దగ్గరగానూ, వేసవికాలంలో దూరంగానూ ఉంటాడు. సూర్యుని చుట్టూ మన భూమి తిరిగే కక్ష్యారూపం దీర్ఘవృత్తంలో ఉండడం వల్ల, ఆ దీర్ఘవృత్తంలో సూర్యుడు మధ్యలో కాకుండా ఓ నాభి (focus) దగ్గర ఉండడం వల్ల సూర్యుడు మనకు సంవత్సరంలో గరిష్టంగా 15,20,98,155 కి.మీ దూరంలోనూ కనిష్టంగా 14,71,01,455 కి. మీ. దూరంలోనూ ఉంటాడు. అలాగే భూమి చుట్టూ తిరిగే చంద్రుని కక్ష్య (lunar trajectory) కూడా దీర్ఘవృత్తాకారంలో ఉంటుంది. భూమి దాని మధ్యలో కాకుండా ఓ నాభి దగ్గర ఉంటుంది. అందువల్ల సూర్యుడి విషయంలో మాదిరిగానే చంద్రుడు మనకు నెలలో (28.5 రోజుల్లో) గరిష్టం 4,06,282 కి.మీ. దూరంలోనూ కనిష్టం 3,56,749 కి.మీ. దూరంలోనూ ఉంటుంది. సూర్యుడి చుట్టూ భూమి, భూమి చుట్టూ చంద్రుడు తిరుగుతుండడం వల్ల సూర్యుడి చుట్టూ భూమి ఓసారి తిరిగేటప్పటికి చంద్రుడు భూమి చుట్టూ దాదాపు 12 రౌండ్లు కొడతాడు. కాబట్టి ప్రతినెలా ఓమారు భూమికీ సూర్యుడికీ మధ్య చంద్రుడి ఉండేలా, మరోమారు సూర్యుడికీ చంద్రుడికీ మధ్యలో భూమి ఉండేలా చంద్రపరిభ్రమణం ఉంటుంది. అంటే నెలకోసారి సూర్యగ్రహణం, ఓసారి చంద్రగ్రహణం ఏర్పడాలి. ఓవిధంగా చెప్పాలంటే ప్రతి అమావాస్యనాడు సూర్యుగ్రహణం ఉండాలి. ఇక పౌర్ణమి అన్నమాటే ఉండకూడదు. కానీ ఇలా జరగడం లేదు. దానికి కారణాలు తెలుసుకుందాం.

సూర్యుని చుట్టూ భూమి తిరిగే దీర్ఘవృత్తాకార మార్గాన్ని ఎల్లిప్టిక్ అంటారు. ఈ దారి దాదాపు ద్వితీయం (2-dimensional) కాబట్టి ఈ మార్గాన్ని ఒక ఊహాతలం (నేల) మీద ఉన్న ఊహా రైలుమార్గంగా భావిద్దాం. అంటే భూమి అనే రైలు ఈ దీర్ఘ వృత్తాకారంలో ఉన్న రైలు పట్టాలపై తన చుట్టూ తాను తిరుగుతూ పరిగెడుతున్నదన్నమాట. అయితే భూమి చుట్టూ తిరుగుతున్న చంద్రుని బాటను కూడా ఓ దీర్ఘవృత్తాకారంలో వేసిన రైలుమార్గం అనుకొంటే అది ఎలా ఉంటుంది? అది కూడా భూమి తిరిగే రైలుమార్గమున్న నేల మీదే ఉంటుందా? అంటే ఈ రెండు రైలుమార్గాలు ప్రతినెలా రెండుచోట్ల కలుసుకుంటాయా? కానీ చంద్రుడు తిరిగే రైలుమార్గం ఆ నేల మీద లేదు. ఆ నేలకు సుమారు 50 కోణంలో ఏటవాలుగా పైకి కట్టిన గోడ మీద ఉన్నట్టు ఊహించుకుందాం. అంటే ఎల్లిప్టిక్ తలం (plane)లో కాకుండా చంద్రుని కక్ష్యామార్గం 50 కోణంలో ఏటవాలుగా ఉందన్నమాట. కాబట్టి ప్రతినెలా చంద్రుడు సూర్యుడికి, భూమికి సరిగ్గా మధ్యలో రాదు. అలాగే భూమి ప్రతినెలా సూర్యుణ్ణి, చంద్రుణ్ణి కలిపే సరళరేఖల మధ్యలో ఉండదు. అంటే ప్రతి పౌర్ణమినాడు భూమి నీడ చంద్రుడి మీద పడదు. కేవలం 6 నెలలకోమారు మాత్రమే కొద్దో గొప్పో గ్రహణాలు జరుగుతాయి. సంపూర్ణ సూర్యగ్రహణం, సంపూర్ణ చంద్రగ్రహణం సంభవించాలంటే భూమి నుంచి సూర్యుడు, చంద్రుడు ఉన్న సాపేక్షదూరాలు కూడా అనువుగా ఉండాలి. అందువల్లే కొన్ని సందర్భాలలో మాత్రమే గ్రహణాలు వస్తాయి. ఖగోళ సూత్రాల ఆధారంగా వాటిని సులభంగా లెక్కించగలం. చివరిగా ఓ మాట. గ్రహణాల వల్ల ఎటువంటి అరిష్టాలు ఉండవు. చంద్రగ్రహణాలు తరచూ సంభవిస్తూ ఉంటాయి. కానీ సూర్యగ్రహణాలు అరుదుగా ఏ చోటనైనా అరుదుగా సంభవిస్తాయి. అటువంటి అరుదైన సూర్యగ్రహణాన్ని సరైన ఫిల్టర్ల సాయంతో చూడటం జీవితంలో మధురమైన అనుభూతిగా భావించాలి తప్ప, ఇళ్ళల్లో దాక్కోనవసరం లేదు.

11/08/2025

TOP 10 AI tools you must master to make your job easy!

1. ChatGPT.com – solves anything
2. RecCloud.com – converts speech to text
3. MidJourney.com – generates art
4. Replit.com – writes and runs code
5. Synthesia.ai – creates AI videos
6. Soundraw.io – produces music in seconds
7. Fliki.ai – turns text into TikToks
8. Starry.ai – creates AI avatars
9. SlidesAI.io – makes presentations for you
10. PicWish.com– edits photos fast

28/01/2025

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How does a Phone Battery percentage display work?

The battery percentage display in smartphones works through a combination of technologies, primarily voltage-based measurement and coulomb counting, along with advanced battery management systems.

Voltage-Based Measurement:

This method relies on measuring the battery’s voltage and correlating it with the battery’s state of charge (SOC). A fully charged lithium-ion battery typically has a voltage around 4.2V, while a nearly depleted one will have around 3.0V. The phone’s system uses pre-defined curves that map voltage levels to battery percentages. Although simple, this method can be inaccurate under varying conditions like temperature changes, load fluctuations, and as the battery ages.

Coulomb Counting:

A more advanced method involves coulomb counting. Here, the system tracks the actual flow of electric charge (in coulombs) in and out of the battery. It measures the current (in amperes) over time and calculates how much charge is being consumed or restored. This method gives a more accurate real-time reading of battery percentage because it tracks the actual usage instead of relying solely on voltage. However, coulomb counting can drift over time, so it’s often combined with voltage measurements for recalibration.

Hybrid Systems:

Most modern smartphones use a hybrid approach, combining both methods. Voltage readings are used to recalibrate the system at full charge or near empty, while coulomb counting provides accurate real-time tracking of charge usage during normal operation. This combination helps counter inaccuracies caused by temperature, battery age, and different usage patterns.

Additionally, manufacturers are now implementing AI-based battery management systems, which learn user behavior and optimize power consumption, further improving the accuracy of battery percentage readings.

~ Adusumalli Ravi Kumar
Physical Science Teacher

02/03/2024

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What are the differences between an Ocean, a Sea, a Bay and a Gulf?

The term “ocean,” as defined by Merriam-Webster, is ”the whole body of saltwater that covers nearly three-fourths of the surface of the earth.” Comprising 1.3 billion cubic kilometers of water, this is the global body of water that covers roughly 71% of the earth. We often hear and speak of the ocean as it’s divided into five components: Arctic, Atlantic, Indian, Pacific and Southern (Antarctic). While these are often referred to as individual oceans (plural), there is no real barrier separating them. Because these are all connected, there is truly only one ocean (singular).
generally “sea” does refer to a smaller segment of the ocean, there are different types of seas in geology: marginal and inland. A marginal sea is one that is defined by its proximity to the land that surrounds it, such as the Mediterranean Sea, the Black Sea or even the Gulf of Mexico (more on that in a minute). Alternatively, an inland sea, while also shallow, is—you guessed it—more inland and covers part of a continent. These are also sometimes called epieric or epicontinental seas. Epimeric or inland seas have changed throughout periods of time as the earth has evolved, but they are typically landlocked and connect to the broader ocean through a very small channel. Modern-day examples of these include the Baltic Sea and the Hudson Bay.
Both bays and gulfs are also part of a sea or ocean. A bay is a broad, recessed coastal inlet where the land curves inward. There is a coastline on three sides of a bay. A gulf is a more defined and deeper inlet with the entrance more enclosed than a bay.

~ Adusumalli Ravi Kumar
Physics Teacher

14/12/2023

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Yes, that's absolutely right! The vast majority of the internet, about 99%, is actually connected by a network of undersea cables. These cables are like thick, underwater highways made of bundles of fiber optic strands, carrying information in the form of light pulses across vast distances.

Imagine a giant spiderweb sprawling across the ocean floor, with each strand representing a cable connecting different continents and countries. That's kind of what this undersea network looks like!
[Image of Undersea cables map]

Here's how it works:

1. **Data is converted into light:** When you send an email, make a video call, or stream a movie, your device first converts the digital information into light pulses.
2. **Light travels through the cables:** These light pulses then zoom through the hair-thin fiber optic strands of the undersea cables, guided by internal reflections.
3. **Repeaters boost the signal:** Due to the distance, the signal needs a little boost along the way. Repeaters placed at intervals in the cables amplify the light pulses, ensuring they reach their destination with enough power.
4. **Data is converted back:** Once the light pulses reach their destination, they're converted back into the original digital information, allowing you to receive emails, watch videos, and stay connected.

These undersea cables are truly the backbone of our modern, interconnected world. They carry everything from emails and social media posts to financial transactions and scientific data. Without them, the internet would be a much slower and fragmented place.

Here are some additional facts about undersea cables:

* There are over 1.5 million kilometers (932,000 miles) of undersea cables in operation worldwide.
* The longest cable system, the SEA-ME-WE 3, stretches over 23,000 kilometers (14,300 miles) from South Africa to Australia.
* The first transatlantic cable, TAT-1, was laid in 1858 and could transmit a single telegraph message per minute. Today's cables can carry billions of bits of data per second.

So next time you're scrolling through your phone or watching a video online, remember the amazing network of undersea cables that makes it all possible!

~ Adusumalli Ravi Kumar
Physics Teacher

15/11/2023

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What is Hawk-Eye Technology used in different sports?

Hawk-Eye, a technology, that is a computer system is used in numerous sports like cricket, tennis, football, badminton, and volleyball. It is usually used to track the trajectory of the ball and is used to display a profile of a statistical path as the moving image to take the decision over the issues that arise during when the game takes place.
The word “Hawk” itself means that something that is vigilant, watchful and has extremely keen sight.
The present study aims at using the hawk-eye technology in sports with regard to the latest trends in the sports arena. It is most commonly used in technologies in different sports. It is put up for a variety of uses like, providing a way to collect interesting statistics, to construct very suggestive visual representations of the game that is being played and helping the viewers for a better understanding of the umpire decisions. The Hawk-Eye is one of such technologies which is considered to be a really the top invention for various sports. The main idea behind its invention was to monitor the trajectory of the ball during the entire duration of the gameplay. It was developed as a replay system, originally for TV Broadcast coverage. Even the scenario of the hawk-eye invention and its use was discussed internationally, where they found it to be reliable for the decision.
Hawk-Eye is the first company to receive a FIFA Goal Line Technology (GLT) license. It is used in sports as this technology allows the officials to make quick and accurate decisions to try and interrupt play as little as possible, for making the game be played fairly.

~ Adusumalli Ravi Kumar
Physics Teacher

08/11/2023

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What is the Gel that is applied before an Ultrasound Scan?

Ultrasound is a special form of technology that sends pulsing sound waves at a high frequency deep into the tissue of a patient using a probe or a transducer. The gel is rubbed onto the skin to help the transducer easily glide along the surface. The device can receive and also send sound waves, which then appear as images that are seen on a computer screen. A sonographer looks at the images to make sure that everything appears normal. This is done in real time and the person operating the ultrasound technology can move the transducer or the probe as required to get a fully defined picture of what’s happening beneath skin level. Screenshot images can also be taken and printed out if required.

Ultrasound gel is composed of a mix of propylene glycol and water. Propylene glycol is a synthetic product that is commonly found in hygiene, cosmetic and food products. It is quite sticky and thick. It’s important for it to have a sticky texture so that it stays on your skin and doesn’t drip off when the ultrasound is being performed.
The gel has a shelf life of approximately 5 years if the bottle remains unopened. Once opened, however, it’s recommended that it be used up within 28 days for the purpose of infection control.

Another thing that can get in the way of reducing clear images is static electricity. Ultrasound gel eliminates the static so that the procedure can be done effectively without any risk of static getting in the way.

~ Adusumalli Ravi Kumar
Physics Teacher

13/07/2023

Let's know (13/07/2023)

What makes Adhesives sticky?

The function of adhesives is to hold things together. Adhesives come in many forms, including glue, tape and sealant, and are used in a variety of everyday applications. In addition, natural substances can act as adhesives, such as soda and caramel. The stickiness of the adhesive is caused by molecular bonds, and its strength depends on how much stress is needed to pull those bonds apart.
Every substance contains molecules that have a positive or negative charge. For two substances to bond, their opposing charges need to be attracted to each other in the exact amount of charge. For example, to produce a molecule of hydrogen chloride (HCl), the positive charge of the hydrogen atom bonds with the negative charge of the chlorine atom, and the combination of the two creates a strong, neutral bond. Adhesives contain long chains of protein molecules that bond with the molecules of the surface they are spread upon by entering the pores and spaces of the material. Therefore, smooth surfaces such as glass don’t react well to adhesives because there aren’t any pores for molecules to enter.
There are glues for glasses.
Some glass glues are designed to work by chemically bonding with the glass surfaces, which typically involves the adhesive molecules reacting with the silicates in the glass to create a strong bond. Other glass glues work by physically interlocking with the glass surfaces, which typically involves the adhesive molecules forming small hooks or bonds that attach to the surface of the glass.

~ Adusumalli Ravi Kumar
Physics Teacher

15/06/2023

I love this symbol as a physicist! And I always believe that...

In quantum physics, as Niels Bohr said, the opposite of a deep scientific truth can also be another deep truth. In other words, the opposite of true can also be true and this is verified by Heisenberg's principle of exactness.

~ Adusumalli Ravi Kumar
Physics Teacher

03/06/2023

Let us know (03/06/2023)

How Does An Air Conditioner (AC) Work?

An air conditioner in a room or a car works by absorbing hot air from a particular room, processing it into itself with the help of a refrigerant and a series of coils, and then releasing cool air into the same room where the hot air was originally collected.

This processing is mainly carried out via five components:

Evaporator
Compressor
Condenser
Expansion valve
Refrigerants

Parts Of An AC:

There are two main types of air conditioning systems: window systems and split systems, which are further divided into mini-split and central systems. In everyday language, these are commonly referred to as window ACs or split ACs.

Regardless of the type of installation, all air conditioners consist of four main components, which are listed below:

Evaporator
An evaporator is basically a heat exchanger coil that is responsible for collecting heat from the interior of a room by means of a refrigerating gas. This component is called an evaporator and is where the liquid refrigerant absorbs heat and evaporates into a gas.
The most common refrigerant gases used in air conditioning systems include hydrofluorocarbons or HFCs such as R-410A, chlorofluorocarbons or CFCs such as R-22 and hydrocarbons such as R-290. This gas actually absorbs heat from the room and passes to the next component for further processing, which…

Compressor
As the name implies, the gaseous refrigerant is compressed here. It is located in the outdoor unit, i.e. in the part that is installed outside the house.

Condenser
The condenser absorbs the evaporated refrigerant from the compressor, converts it back into a liquid and expels the heat to the outside. Of course, it is also located on the outside unit of the split AC.

Expansion Valve
The expansion valve, also known as a throttle device, is located between the two coils, the cooling coils of the evaporator and the hot coils of the condenser. It controls the amount of refrigerant moving towards the evaporator.

Note that in the case of window ACs, the three components mentioned above are all located in a small metal box installed in a window opening.

These are the main components of an air conditioner. Let’s look at how they work together to make an air conditioner do what it does.

AC Operating Principle Of The Air Conditioner
An air conditioner collects hot air from a particular room, processes it into itself with the help of a refrigerant and a series of coils, and then releases cool air into the same room where the hot air was originally collected. This is basically how all air conditioners work.

Debunking The Myth
Many people believe that an air conditioner, with the help of machines installed in it, generates cooled air, which can cool a room so quickly. This might also explain why it consumes so much electricity. In reality, however, this is a mistake. An air conditioner is not a magical device; it only uses some physical and chemical phenomena very effectively to cool a particular room.

What Happens When You Turn On The Air Conditioning?
When you turn on an air conditioner and set the desired temperature, say 20 degrees Celsius, the thermostat installed in it will detect that there is a difference between the temperature of the room air and the temperature you have chosen.

This warm air is sucked in through a grill at the bottom of the indoor unit, which then flows through some pipes through which the refrigerant, i.e. a coolant, flows. The refrigerant fluid absorbs the heat and itself becomes a hot gas. Thus, heat is removed from the air that falls on the evaporator coils. Note that the evaporator coil not only absorbs heat, but also flushes moisture out of the incoming air, which helps to dehumidify the room.

This hot refrigerant gas is then passed on to the compressor located on the outside unit. True to its name, the compressor compresses the gas so that it becomes hot as the compression of a gas increases its temperature.

This hot high-pressure gas then reaches the third component – the condenser. Here, too, the condenser stays true to its name and condenses the hot gas into a liquid.

The refrigerant enters the condenser as a hot gas but quickly becomes a cooler liquid because the heat from the “hot gas” is dissipated into the environment through metal fins. As a result, the refrigerant loses its heat as it leaves the condenser and becomes a cooler liquid. This flows through an expansion valve – a tiny hole in the system’s copper tube – which controls the flow of the cool liquid refrigerant into the evaporator, so that the refrigerant arrives at the point where its journey began.

The whole process repeats itself again and again until the desired temperature is reached. In short, an air conditioner sucks in warm air, again and again, cools it and pushes it back into the room until there is no warm air left to cool down.

~ Adusumalli Ravi Kumar
Physics Teacher

17/05/2023

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