Today I Learn

2021-03-17 15:07:12 ​​What are White Dwarf Stars?

White dwarfs are dead stars. A single white dwarf contains roughly the mass of our sun in a volume no bigger than our planet. Our sun will become a white dwarf someday. White dwarfs are the hot, dense remnants of long-dead stars. They are the stellar cores left behind after a star has exhausted its fuel supply and blown its bulk of gas and dust into space. These exotic objects mark the final stage of evolution for most stars in the universe – including our sun – and light the way to a deeper understanding of cosmic history.

White dwarfs are born when a star shuts down. A star spends most of its life in a precarious balance between gravity and outward gas pressure. The weight of a couple octillion tons of gas pressing down on the stellar core drives densities and temperatures high enough to ignite nuclear fusion: the fusing together of hydrogen nuclei to form helium. The steady release of thermonuclear energy prevents the star from collapsing on itself.

@TodayILearn Open / Comment

2021-03-14 04:13:44 Lightning

Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions in the atmosphere or ground temporarily equalize themselves, causing the instantaneous release of as much as one gigajoule of energy. This discharge may produce a wide range of electromagnetic radiation, from very hot plasma created by the rapid movement of electrons to brilliant flashes of visible light in the form of black-body radiation.

Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms and other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions.

@TodayILearn Open / Comment

2021-03-12 05:23:18 What countries are included in UK?

The official name of the UK is the "United Kingdom of Great Britain and Northern Ireland". The name refers to the union of what were once four separate nations: England, Scotland, Wales and Ireland (though most of Ireland is now independent). The United Kingdom is made up of: England - The capital is London.

@TodayILearn Open / Comment

2021-03-11 04:51:05 What are vaccine passports?

Even though the nomenclature comes from passports, most vaccine passports have been envisaged as digital documents. They are supposed to function as proof that the holder has been vaccinated against Covid-19 and is, therefore, “safe”.

What vaccine passports do we have now?

Israeli government, several associations and non-profits have been issuing their own versions for international travel.

Whom will vaccine passports help?

The primary benefit will be to the tourism and the hospitality industries, which are both seen as being at the heart of Covid-19 spread and are the worst hit by the pandemic.

@TodayILearn Open / Comment

2021-03-09 18:13:59 How cockroach can live without head ?

A cockroach can live for a week without its head. Due to their open circulatory system, and the fact that they breathe through little holes in each of their body segments, they are not dependent on the mouth or head to breathe. The roach only dies because without a mouth, it can't drink water and dies of thirst.

@TodayILearn Open / Comment

2021-03-08 03:34:29 ​​​​What is Mammography or Mammogram?

A mammogram is an x-ray picture of the breast. It can be used to check for breast cancer in women who have no signs or symptoms of the disease. It can also be used if you have a lump or other sign of breast cancer.

Screening mammography is the type of mammogram that checks you when you have no symptoms. It can help reduce the number of deaths from breast cancer among women ages 40 to 70. But it can also have drawbacks. Mammograms can sometimes find something that looks abnormal but isn't cancer. This leads to further testing and can cause you anxiety. Sometimes mammograms can miss cancer when it is there. It also exposes you to radiation. You should talk to your doctor about the benefits and drawbacks of mammograms. Together, you can decide when to start and how often to have a mammogram. Mammograms are also recommended for younger women who have symptoms of breast cancer or who have a high risk of the disease.

When you have a mammogram, you stand in front of an x-ray machine. The person who takes the x-rays places your breast between two plastic plates. The plates press your breast and make it flat. This may be uncomfortable, but it helps get a clear picture.

@TodayILearn Open / Comment

2021-03-08 03:34:18 Open / Comment

2021-03-06 08:51:04 ​​What are Anti Drone Systems?

Anti drone systems are used to detect and/or intercept unwanted drones and unmanned aerial vehicles (UAVs). Hostile drones may be used to deploy explosives, smuggle contraband or gather intelligence on sensitive assets, and the proliferation of low-cost UAVs has led to an increase in incidents. Anti drone technology is deployed to protect areas such as airports, critical infrastructure, large public spaces such as stadiums, and military installations and battlefield sites.

Modern anti drone radar systems may use a variety of radar technologies, including ESA (electronically scanned array), staring radar, and micro-Doppler, depending on requirements for range, size of protection zone, number of simultaneous targets to track, and ability to deal with environmental clutter. They provide 3D airspace tracking and use sophisticated signal processing techniques to accurately detect and identify drones. As each detection method has its advantages and drawbacks, multi-sensor anti-drone systems will combine different sensor types along with sensor fusion algorithms to provide a complete integrated solution.

@TodayILearn Open / Comment

2021-03-06 08:51:01 Open / Comment

2021-03-06 08:50:16 New Zealand

New Zealand is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island and the South Island —and more than 700 smaller islands, covering a total area of 268,021 square kilometres.

Capital: Wellington

Dialing code: +64

Population: 49.2 lakhs (2019)

Prime minister: Jacinda Ardern

@TodayILearn Open / Comment