Einstein’s Repulsive Einstein’s Repulsive IdeaIdea

Unit 2 Section A

Albert Einstein (1879---1955)

Do you have any idea about the formation of our universe before reading this article?

A human being is part of the whole called by us universe, a part limited in time and space. We experience ourselves, our thoughts and feelings as something separate from the rest. A kind of optical delusion of consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection for a few persons nearest to us. Our task must be to free ourselves from the prison by widening our circle of compassion to embrace all living creatures and the whole of nature in its beauty. The true value of a human being is determined by the measure and the sense in which they have obtained liberation from the self. We shall require a substantially new manner of thinking if humanity is to survive.

---Albert Einstein, 1954

An Overview of Cosmology

Objectives

• Develop perspective on the history of human knowledge of the universe

• Understand the process of scientific exploration of the universe

• Contemplate the current state of astronomy and think about future missions

For thousands of years, astronomers wrestled with basic questions about the size and age of the universe. Does the universe go on forever, or does it have an edge somewhere? Has it always existed, or did it come to being some time in the past?

What is Cosmology?

2nd Century: Claudius Ptolemy (Physics of Aristotle)Model: Earth-centered Cosmology

Three scientific revolutions in cosmology

16th Century: Nicolaus Copernicus (Physics of Newton) Model: Sun-centered Cosmology

20th Century: Edwin Hubble (Physics of Einstein) Model: Big Bang Cosmology

Our View of the Cosmos - the story of scientific models

Big idea: Earth was viewed as a stationary center of the universe, with sun, moon, and stars revolving about it in circular orbits and at a uniform rate.

Earth-centered Cosmology: Claudius Ptolemy, 100-170 AD

Sun-centered Cosmology: Nicholas Copernicus 1473-1543

Big idea: Copernican system placed the sun motionless at the center of the solar system with all the planets, including the earth, revolving around it.

Big Bang Cosmology: Edwin Hubble and Albert Einstein

Big idea: The universe had exploded and expanded from a small, hot, dense state into what we see today.

the theory of the cosmic explosion that marked the origin of the universe. According to the big-bang theory, at the beginning of time, all of the matter and energy in the universe was concentrated in a very dense state, from which it exploded, with the resulting expansion continuing until the present. This big bang is dated between 10 and 20 billion years ago. In this initial state, the universe was very hot and contained a thermal soup of quarks, electrons, photons, and other elementary particles. After many millions of years the expanding universe, at first a very hot gas, thinned and cooled enough to condense into individual galaxies and then stars.

Big Bang Theory

History of expansion: A rough picture of how the universe's expansion

decelerated, then began to accelerate. Fate is not known.

Einstein’s Repulsive Idea

This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion.

Einstein’s Repulsive Idea

Some theorists think the Universe is filled with a mysterious dark energy, a sort of negative gravity.

The Hubble Space Telescope recently captured light from a supernova located farther from Earth than any previously seen.

The finding has bolstered cosmological models for the universe's expansion and a mysterious “dark energy” pervading it. The supernova, or exploding star, is located 10 billion light-years from Earth.

Dark Energy73%

Dark Matter23%

“Normal Matter”4%

Conclusions

• Big Bang model describes our current understanding of the universe.

• New discoveries, such as dark matter and accelerating expansion (Dark Energy), lead us to refine our model.

• Science is an ongoing process - forcing us to test our model through prediction and observation. The more tests it passes, the greater is our confidence in it.

1. What does it mean to say that the universe is accelerating? 2. What are the difficulties in studying and understanding the

universe?

New technology has made cosmology one of the most exciting sciences today, but not all the answers have been found. Watch the video segment the Gravity and the Expanding Universe and answer the following two questions.

Einstein’s Repulsive Idea

The scientific style is dictated by the purpose of the type of writing. The scientist or engineer will generally write to describe a phenomenon, an experiment or a process, or to explain a theory. Hence they belong to the category called exposition. In this text, the author explains Einstein’s repulsive idea and its relationship to the latest research of expanding universe.

Key words in the text

general relativity

gravity and antigravity

supernova

Hubble Space Telescope

cosmological term

Relativity After all, his special and general r

elativity theories made the astonishing assertion that time, space and matter could be squeezed and stretched like so much India rubber. (Para.1)

Einstein in 1905, at the age of 26

Special Relativity---We cannot catch up with light.---Mass is a form of energy.

E = m c2

General RelativityGR encompasses gravity and describes the expanding universe and black holes.

The trouble was that some sort of antigravity force——Einstein called it the “cosmological term”—— was required to make the predictions of general relativity match what astronomers believed the actual universe looked like. (Para. 1)

Einstein’s Repulsive Idea

Question: Why did Einstein hypothesize the cosmological constant? Why did he later discard it?

The great physicist was hugely relieved when the discovery of the expanding universe in the 1920s let him cross out what he declared was “my greatest blunder.” (Para. 1)

Einstein’s Repulsive Idea

Question: 1. Why did Einstein call his cos

mological constant his “greatest blunder”?

2. What is the assumption taken from Hubble’s discovery and recent astronomical data?

Using the Hubble Space Telescope to find and study a distant supernova, astronomers from two rival research teams have jointly gathered the strongest evidence yet that the expansion of the universe is actually speeding up. (Para. 2)

Hubble Space Telescope (HST): the first general-purpose orbiting observatory, Named after American astronomer Edwin P. Hubble. The Hubble Space Telescope was launched on April 24, 1990.

The first hint came a couple of years ago, when two independent teams of astronomers tried to calibrate the cosmic expansion using Type Ia supernovas, a kind of exploding star whose intrinsic brightness is highly consistent. (Para. 4)

Supernova: a stellar explosion that produces an extremely bright object made of plasma that declines to invisibility over weeks or months.