1.       Standard model of particle physics tries to describe matter in the simplest forms

2.       We see an object when light is reflected by it. When we attempt to see extremely small elementary particles light (electromagnetic wave) gets dodged. When extremely small wavelengths electromagnetic waves cannot be used instead of light because it has high energy and alters the particles. So theories were based assuming the elementary particles were point

3.       Beginning of theory: In 1960s. In the Standard Model which explains fundamental particles and their interaction strange behavior between pairs of mesons was noted. To explain this, it was proposed that that the quarks in mesons are joined by strings

4.       All physical forces except gravity (which was a theory of geometry of space-time)

5.       So there was an absence of a single” theory of everything”

6.       The assumption of particle to be a point was developed into a line model which describes different elementary particles as diverse modes of vibration of the string

7.       The theory was replaced by quantum chromodynamics

8.       In 19 70s it was proposed that oscillations in very small strings give rise to force carrying particles.

9.       Finally, in 1995 Ed Witten combined many forms of super string theory into the of M theory

10.   Strings with ends tied up can be waves which can be constructive (where phases of the overlapping wave match and frequency of the wave is enhanced) or destructive interference

11.   Particular frequencies / energies are possible for particular string

12.   In standard model there are 19 free parameters like mass which we get from the length of the string

13.   So strings are extremely small 1D structures (Planck scale) in loops or stretched in vibrational modes which need additional dimensions of space-time to keep up with mathematical consistency. M theory needs 11 dimensions with three spatial dimensions, one-time dimension, and 6 more small spatial dimensions

14.   String theory answers puzzling questions about quantum gravity and black holes

15.   Currently string theory has not made complete/ testable predictions or proven in an experiment

1.      Ice age is the decrease in the temperature of the Earth's exterior and atmosphere for long periods giving rise to mainland and polar ice sheets and mountainous glaciers

2.      Discrete pulses of cold climate called glacial advances / glacials and intermittent warm periods – interglacials are part of ice ages.

3.      Proofs for ice ages:

a.       Geological - rock scouring, mass of rocks / sediment transmitted and dumped by a glacier, drumlins, valley cutting, and the deposition of till. Glaciations distort and remove geological evidence.

b.      Chemical - noting the ratios of isotopes in fossils in deposits and sedimentary rocks and ocean cores. Water with heavier isotopes has a more heat of evaporation and its percentage reduce with colder conditions

c.       Paleontological- studying variations in the geographical dispersal of fossils as cold adapted organisms go into lower latitudes during glacial period while other organisms become extinct

4.      At least five major ice ages were in the Earth's history:

a.        Huronian- ( 2.4 to 2.1 Ga (billion years) ago /early Proterozoic Eon). It was triggered by the removal of atmospheric methane during the Great Oxygenation Event.

b.      Cryogenian (720 to 630 million years ago / the Cryogenian period) . It was the most severe which ended by the buildup of greenhouse gases from volcanoes

c.        Andean-Saharan (460 to 420 million years ago / Late Ordovician) marked by several sequences of glacials and interglacials lasting several million years.

d.      Karoo Ice Age (360 to 260 million years ago / Devonian period ) The evolution of land plants resulted in increase in planetary oxygen levels. Widespread polar ice caps covered mountain tops in South Africa, Argentina during the Carboniferous

e.       Quaternary Ice Age (2.58 million years ago) marked by sequences of glacial advances, and interglacial periods/ glacial retreats of average 70000 years The earth is presently in an interglacial (Holocene epoch) as about 11,700 years ago the last glacial period ended and Greenland and Antarctic ice sheets are the remains. 18,000 years ago it reached peak conditions when the ice grew more than 12,000 feet thick spreading across Canada, Russia, South America and Scandinavia with 400 feet high sea and temperature of -10 to -40 F. Pine forests and prairie grasses grew in North America. Humans survived as they adapted by creating tools like bone needle to sew warm clothing and they travelled to spread to new regions by ice land bridges. With the advent of Holocene epoch, humans started agriculture and domestication

5.      There has been no ice in high latitudes when ice age is not prevalent

6.      An ice age results in huge change in Earth’s surface as glaciers by gathering rocks and soil and corroding hills restyle the landscape and intense drip in sea levels causes rivers to cut out deeper valleys creating large inland lakes

7.      Causes:

a.       atmospheric composition of carbon dioxide and methane

b.      variations in the earth's orbit around the Sun

c.       volcanic eruptions of supervolcanoes

d.      the tectonic plates movement affecting wind and ocean currents

e.       differences in solar output

f.        the effect of huge meteorites

g.      plate tectonics elevate mountain ranges exposing new rock which gets weathered and broken into oceans absorbing carbon dioxide

1) In biology who discovered nucleus?

2) What is the full form of GDP and  PPP in economics?