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The Universal Declaration of Human Rights
The Universal Declaration of Human Rights (UDHR) is a milestone document in the history of human rights. Drafted by representatives with different legal and cultural backgrounds from all regions of the world, the Declaration was proclaimed by the United Nations General Assembly in Paris on 10 December 1948 General Assembly resolution 217 A as a common standard of achievements for all peoples and all nations. It sets out, for the first time, fundamental human rights to be universally protected and it has been translated into almost 500 languages.
Preamble
Whereas recognition of the inherent dignity and of the equal and inalienable rights of all members of the human family is the foundation of freedom, justice and peace in the world,
Whereas disregard and contempt for human rights have resulted in barbarous acts which have outraged the conscience of mankind, and the advent of a world in which human beings shall enjoy freedom of speech and belief and freedom from fear and want has been proclaimed as the highest aspiration of the common people,
Whereas it is essential, if man is not to be compelled to have recourse, as a last resort, to rebellion against tyranny and oppression, that human rights should be protected by the rule of law,
Whereas it is essential to promote the development of friendly relations between nations,
Whereas the peoples of the United Nations have in the Charter reaffirmed their faith in fundamental human rights, in the dignity and worth of the human person and in the equal rights of men and women and have determined to promote social progress and better standards of life in larger freedom,
Whereas Member States have pledged themselves to achieve, in co-operation with the United Nations, the promotion of universal respect for and observance of human rights and fundamental freedoms,
Whereas a common understanding of these rights and freedoms is of the greatest importance for the full realization of this pledge,
Now, Therefore THE GENERAL ASSEMBLY proclaims THIS UNIVERSAL DECLARATION OF HUMAN RIGHTS as a common standard of achievement for all peoples and all nations, to the end that every individual and every organ of society, keeping this Declaration constantly in mind, shall strive by teaching and education to promote respect for these rights and freedoms and by progressive measures, national and international, to secure their universal and effective recognition and observance, both among the peoples of Member States themselves and among the peoples of territories under their jurisdiction.
Article 1.
All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.
Article 2.
Everyone is entitled to all the rights and freedoms set forth in this Declaration, without distinction of any kind, such as race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status. Furthermore, no distinction shall be made on the basis of the political, jurisdictional or international status of the country or territory to which a person belongs, whether it be independent, trust, non-self-governing or under any other limitation of sovereignty.
Article 3.
Everyone has the right to life, liberty and security of person.
Article 4.
No one shall be held in slavery or servitude; slavery and the slave trade shall be prohibited in all their forms.
Article 5.
No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment.
Article 6.
Everyone has the right to recognition everywhere as a person before the law.
Article 7.
All are equal before the law and are entitled without any discrimination to equal protection of the law. All are entitled to equal protection against any discrimination in violation of this Declaration and against any incitement to such discrimination.
Article 8.
Everyone has the right to an effective remedy by the competent national tribunals for acts violating the fundamental rights granted him by the constitution or by law.
Article 9.
No one shall be subjected to arbitrary arrest, detention or exile.
Article 10.
Everyone is entitled in full equality to a fair and public hearing by an independent and impartial tribunal, in the determination of his rights and obligations and of any criminal charge against him.
Article 11.
(1) Everyone charged with a penal offence has the right to be presumed innocent until proved guilty according to law in a public trial at which he has had all the guarantees necessary for his defence.
(2) No one shall be held guilty of any penal offence on account of any act or omission which did not constitute a penal offence, under national or international law, at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time the penal offence was committed.
Article 12.
No one shall be subjected to arbitrary interference with his privacy, family, home or correspondence, nor to attacks upon his honour and reputation. Everyone has the right to the protection of the law against such interference or attacks.
Article 13.
(1) Everyone has the right to freedom of movement and residence within the borders of each state.
(2) Everyone has the right to leave any country, including his own, and to return to his country.
Article 14.
(1) Everyone has the right to seek and to enjoy in other countries asylum from persecution.
(2) This right may not be invoked in the case of prosecutions genuinely arising from non-political crimes or from acts contrary to the purposes and principles of the United Nations.
Article 15.
(1) Everyone has the right to a nationality.
(2) No one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality.
Article 16.
(1) Men and women of full age, without any limitation due to race, nationality or religion, have the right to marry and to found a family. They are entitled to equal rights as to marriage, during marriage and at its dissolution.
(2) Marriage shall be entered into only with the free and full consent of the intending spouses.
(3) The family is the natural and fundamental group unit of society and is entitled to protection by society and the State.
Article 17.
(1) Everyone has the right to own property alone as well as in association with others.
(2) No one shall be arbitrarily deprived of his property.
Article 18.
Everyone has the right to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief, and freedom, either alone or in community with others and in public or private, to manifest his religion or belief in teaching, practice, worship and observance.
Article 19.
Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
Article 20.
(1) Everyone has the right to freedom of peaceful assembly and association.
(2) No one may be compelled to belong to an association.
Article 21.
(1) Everyone has the right to take part in the government of his country, directly or through freely chosen representatives.
(2) Everyone has the right of equal access to public service in his country.
(3) The will of the people shall be the basis of the authority of government; this will shall be expressed in periodic and genuine elections which shall be by universal and equal suffrage and shall be held by secret vote or by equivalent free voting procedures.
Article 22.
Everyone, as a member of society, has the right to social security and is entitled to realization, through national effort and international co-operation and in accordance with the organization and resources of each State, of the economic, social and cultural rights indispensable for his dignity and the free development of his personality.
Article 23.
(1) Everyone has the right to work, to free choice of employment, to just and favourable conditions of work and to protection against unemployment.
(2) Everyone, without any discrimination, has the right to equal pay for equal work.
(3) Everyone who works has the right to just and favourable remuneration ensuring for himself and his family an existence worthy of human dignity, and supplemented, if necessary, by other means of social protection.
(4) Everyone has the right to form and to join trade unions for the protection of his interests.
Article 24.
Everyone has the right to rest and leisure, including reasonable limitation of working hours and periodic holidays with pay.
Article 25.
(1) Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing and medical care and necessary social services, and the right to security in the event of unemployment, sickness, disability, widowhood, old age or other lack of livelihood in circumstances beyond his control.
(2) Motherhood and childhood are entitled to special care and assistance. All children, whether born in or out of wedlock, shall enjoy the same social protection.
Article 26.
(1) Everyone has the right to education. Education shall be free, at least in the elementary and fundamental stages. Elementary education shall be compulsory. Technical and professional education shall be made generally available and higher education shall be equally accessible to all on the basis of merit.
(2) Education shall be directed to the full development of the human personality and to the strengthening of respect for human rights and fundamental freedoms. It shall promote understanding, tolerance and friendship among all nations, racial or religious groups, and shall further the activities of the United Nations for the maintenance of peace.
(3) Parents have a prior right to choose the kind of education that shall be given to their children.
Article 27.
(1) Everyone has the right freely to participate in the cultural life of the community, to enjoy the arts and to share in scientific advancement and its benefits.
(2) Everyone has the right to the protection of the moral and material interests resulting from any scientific, literary or artistic production of which he is the author.
Article 28.
Everyone is entitled to a social and international order in which the rights and freedoms set forth in this Declaration can be fully realized.
Article 29.
(1) Everyone has duties to the community in which alone the free and full development of his personality is possible.
(2) In the exercise of his rights and freedoms, everyone shall be subject only to such limitations as are determined by law solely for the purpose of securing due recognition and respect for the rights and freedoms of others and of meeting the just requirements of morality, public order and the general welfare in a democratic society.
(3) These rights and freedoms may in no case be exercised contrary to the purposes and principles of the United Nations.
Article 30.
Nothing in this Declaration may be interpreted as implying for any State, group or person any right to engage in any activity or to perform any act aimed at the destruction of any of the rights and freedoms set forth herein.
The Universal Declaration of Human Rights (UDHR) is a milestone document in the history of human rights. Drafted by representatives with different legal and cultural backgrounds from all regions of the world, the Declaration was proclaimed by the United Nations General Assembly in Paris on 10 December 1948 General Assembly resolution 217 A as a common standard of achievements for all peoples and all nations. It sets out, for the first time, fundamental human rights to be universally protected and it has been translated into almost 500 languages.
Preamble
Whereas recognition of the inherent dignity and of the equal and inalienable rights of all members of the human family is the foundation of freedom, justice and peace in the world,
Whereas disregard and contempt for human rights have resulted in barbarous acts which have outraged the conscience of mankind, and the advent of a world in which human beings shall enjoy freedom of speech and belief and freedom from fear and want has been proclaimed as the highest aspiration of the common people,
Whereas it is essential, if man is not to be compelled to have recourse, as a last resort, to rebellion against tyranny and oppression, that human rights should be protected by the rule of law,
Whereas it is essential to promote the development of friendly relations between nations,
Whereas the peoples of the United Nations have in the Charter reaffirmed their faith in fundamental human rights, in the dignity and worth of the human person and in the equal rights of men and women and have determined to promote social progress and better standards of life in larger freedom,
Whereas Member States have pledged themselves to achieve, in co-operation with the United Nations, the promotion of universal respect for and observance of human rights and fundamental freedoms,
Whereas a common understanding of these rights and freedoms is of the greatest importance for the full realization of this pledge,
Now, Therefore THE GENERAL ASSEMBLY proclaims THIS UNIVERSAL DECLARATION OF HUMAN RIGHTS as a common standard of achievement for all peoples and all nations, to the end that every individual and every organ of society, keeping this Declaration constantly in mind, shall strive by teaching and education to promote respect for these rights and freedoms and by progressive measures, national and international, to secure their universal and effective recognition and observance, both among the peoples of Member States themselves and among the peoples of territories under their jurisdiction.
Article 1.
All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.
Article 2.
Everyone is entitled to all the rights and freedoms set forth in this Declaration, without distinction of any kind, such as race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status. Furthermore, no distinction shall be made on the basis of the political, jurisdictional or international status of the country or territory to which a person belongs, whether it be independent, trust, non-self-governing or under any other limitation of sovereignty.
Article 3.
Everyone has the right to life, liberty and security of person.
Article 4.
No one shall be held in slavery or servitude; slavery and the slave trade shall be prohibited in all their forms.
Article 5.
No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment.
Article 6.
Everyone has the right to recognition everywhere as a person before the law.
Article 7.
All are equal before the law and are entitled without any discrimination to equal protection of the law. All are entitled to equal protection against any discrimination in violation of this Declaration and against any incitement to such discrimination.
Article 8.
Everyone has the right to an effective remedy by the competent national tribunals for acts violating the fundamental rights granted him by the constitution or by law.
Article 9.
No one shall be subjected to arbitrary arrest, detention or exile.
Article 10.
Everyone is entitled in full equality to a fair and public hearing by an independent and impartial tribunal, in the determination of his rights and obligations and of any criminal charge against him.
Article 11.
(1) Everyone charged with a penal offence has the right to be presumed innocent until proved guilty according to law in a public trial at which he has had all the guarantees necessary for his defence.
(2) No one shall be held guilty of any penal offence on account of any act or omission which did not constitute a penal offence, under national or international law, at the time when it was committed. Nor shall a heavier penalty be imposed than the one that was applicable at the time the penal offence was committed.
Article 12.
No one shall be subjected to arbitrary interference with his privacy, family, home or correspondence, nor to attacks upon his honour and reputation. Everyone has the right to the protection of the law against such interference or attacks.
Article 13.
(1) Everyone has the right to freedom of movement and residence within the borders of each state.
(2) Everyone has the right to leave any country, including his own, and to return to his country.
Article 14.
(1) Everyone has the right to seek and to enjoy in other countries asylum from persecution.
(2) This right may not be invoked in the case of prosecutions genuinely arising from non-political crimes or from acts contrary to the purposes and principles of the United Nations.
Article 15.
(1) Everyone has the right to a nationality.
(2) No one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality.
Article 16.
(1) Men and women of full age, without any limitation due to race, nationality or religion, have the right to marry and to found a family. They are entitled to equal rights as to marriage, during marriage and at its dissolution.
(2) Marriage shall be entered into only with the free and full consent of the intending spouses.
(3) The family is the natural and fundamental group unit of society and is entitled to protection by society and the State.
Article 17.
(1) Everyone has the right to own property alone as well as in association with others.
(2) No one shall be arbitrarily deprived of his property.
Article 18.
Everyone has the right to freedom of thought, conscience and religion; this right includes freedom to change his religion or belief, and freedom, either alone or in community with others and in public or private, to manifest his religion or belief in teaching, practice, worship and observance.
Article 19.
Everyone has the right to freedom of opinion and expression; this right includes freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers.
Article 20.
(1) Everyone has the right to freedom of peaceful assembly and association.
(2) No one may be compelled to belong to an association.
Article 21.
(1) Everyone has the right to take part in the government of his country, directly or through freely chosen representatives.
(2) Everyone has the right of equal access to public service in his country.
(3) The will of the people shall be the basis of the authority of government; this will shall be expressed in periodic and genuine elections which shall be by universal and equal suffrage and shall be held by secret vote or by equivalent free voting procedures.
Article 22.
Everyone, as a member of society, has the right to social security and is entitled to realization, through national effort and international co-operation and in accordance with the organization and resources of each State, of the economic, social and cultural rights indispensable for his dignity and the free development of his personality.
Article 23.
(1) Everyone has the right to work, to free choice of employment, to just and favourable conditions of work and to protection against unemployment.
(2) Everyone, without any discrimination, has the right to equal pay for equal work.
(3) Everyone who works has the right to just and favourable remuneration ensuring for himself and his family an existence worthy of human dignity, and supplemented, if necessary, by other means of social protection.
(4) Everyone has the right to form and to join trade unions for the protection of his interests.
Article 24.
Everyone has the right to rest and leisure, including reasonable limitation of working hours and periodic holidays with pay.
Article 25.
(1) Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing and medical care and necessary social services, and the right to security in the event of unemployment, sickness, disability, widowhood, old age or other lack of livelihood in circumstances beyond his control.
(2) Motherhood and childhood are entitled to special care and assistance. All children, whether born in or out of wedlock, shall enjoy the same social protection.
Article 26.
(1) Everyone has the right to education. Education shall be free, at least in the elementary and fundamental stages. Elementary education shall be compulsory. Technical and professional education shall be made generally available and higher education shall be equally accessible to all on the basis of merit.
(2) Education shall be directed to the full development of the human personality and to the strengthening of respect for human rights and fundamental freedoms. It shall promote understanding, tolerance and friendship among all nations, racial or religious groups, and shall further the activities of the United Nations for the maintenance of peace.
(3) Parents have a prior right to choose the kind of education that shall be given to their children.
Article 27.
(1) Everyone has the right freely to participate in the cultural life of the community, to enjoy the arts and to share in scientific advancement and its benefits.
(2) Everyone has the right to the protection of the moral and material interests resulting from any scientific, literary or artistic production of which he is the author.
Article 28.
Everyone is entitled to a social and international order in which the rights and freedoms set forth in this Declaration can be fully realized.
Article 29.
(1) Everyone has duties to the community in which alone the free and full development of his personality is possible.
(2) In the exercise of his rights and freedoms, everyone shall be subject only to such limitations as are determined by law solely for the purpose of securing due recognition and respect for the rights and freedoms of others and of meeting the just requirements of morality, public order and the general welfare in a democratic society.
(3) These rights and freedoms may in no case be exercised contrary to the purposes and principles of the United Nations.
Article 30.
Nothing in this Declaration may be interpreted as implying for any State, group or person any right to engage in any activity or to perform any act aimed at the destruction of any of the rights and freedoms set forth herein.
The unanimous Declaration of the thirteen united States of America
hen in the Course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn that mankind are more disposed to suffer, while evils are sufferable than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security. — Such has been the patient sufferance of these Colonies; and such is now the necessity which constrains them to alter their former Systems of Government. The history of the present King of Great Britain is a history of repeated injuries and usurpations, all having in direct object the establishment of an absolute Tyranny over these States. To prove this, let Facts be submitted to a candid world.
He has refused his Assent to Laws, the most wholesome and necessary for the public good.
He has forbidden his Governors to pass Laws of immediate and pressing importance, unless suspended in their operation till his Assent should be obtained; and when so suspended, he has utterly neglected to attend to them.
He has refused to pass other Laws for the accommodation of large districts of people, unless those people would relinquish the right of Representation in the Legislature, a right inestimable to them and formidable to tyrants only.
He has called together legislative bodies at places unusual, uncomfortable, and distant from the depository of their Public Records, for the sole purpose of fatiguing them into compliance with his measures.
He has dissolved Representative Houses repeatedly, for opposing with manly firmness his invasions on the rights of the people.
He has refused for a long time, after such dissolutions, to cause others to be elected, whereby the Legislative Powers, incapable of Annihilation, have returned to the People at large for their exercise; the State remaining in the mean time exposed to all the dangers of invasion from without, and convulsions within.
He has endeavoured to prevent the population of these States; for that purpose obstructing the Laws for Naturalization of Foreigners; refusing to pass others to encourage their migrations hither, and raising the conditions of new Appropriations of Lands.
He has obstructed the Administration of Justice by refusing his Assent to Laws for establishing Judiciary Powers.
He has made Judges dependent on his Will alone for the tenure of their offices, and the amount and payment of their salaries.
He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.
He has kept among us, in times of peace, Standing Armies without the Consent of our legislatures.
He has affected to render the Military independent of and superior to the Civil Power.
He has combined with others to subject us to a jurisdiction foreign to our constitution, and unacknowledged by our laws; giving his Assent to their Acts of pretended Legislation:
For quartering large bodies of armed troops among us:
For protecting them, by a mock Trial from punishment for any Murders which they should commit on the Inhabitants of these States:
For cutting off our Trade with all parts of the world:
For imposing Taxes on us without our Consent:
For depriving us in many cases, of the benefit of Trial by Jury:
For transporting us beyond Seas to be tried for pretended offences:
For abolishing the free System of English Laws in a neighbouring Province, establishing therein an Arbitrary government, and enlarging its Boundaries so as to render it at once an example and fit instrument for introducing the same absolute rule into these Colonies
For taking away our Charters, abolishing our most valuable Laws and altering fundamentally the Forms of our Governments:
For suspending our own Legislatures, and declaring themselves invested with power to legislate for us in all cases whatsoever.
He has abdicated Government here, by declaring us out of his Protection and waging War against us.
He has plundered our seas, ravaged our coasts, burnt our towns, and destroyed the lives of our people.
He is at this time transporting large Armies of foreign Mercenaries to compleat the works of death, desolation, and tyranny, already begun with circumstances of Cruelty & Perfidy scarcely paralleled in the most barbarous ages, and totally unworthy the Head of a civilized nation.
He has constrained our fellow Citizens taken Captive on the high Seas to bear Arms against their Country, to become the executioners of their friends and Brethren, or to fall themselves by their Hands.
He has excited domestic insurrections amongst us, and has endeavoured to bring on the inhabitants of our frontiers, the merciless Indian Savages whose known rule of warfare, is an undistinguished destruction of all ages, sexes and conditions.
In every stage of these Oppressions We have Petitioned for Redress in the most humble terms: Our repeated Petitions have been answered only by repeated injury. A Prince, whose character is thus marked by every act which may define a Tyrant, is unfit to be the ruler of a free people.
Nor have We been wanting in attentions to our British brethren. We have warned them from time to time of attempts by their legislature to extend an unwarrantable jurisdiction over us. We have reminded them of the circumstances of our emigration and settlement here. We have appealed to their native justice and magnanimity, and we have conjured them by the ties of our common kindred to disavow these usurpations, which would inevitably interrupt our connections and correspondence. They too have been deaf to the voice of justice and of consanguinity. We must, therefore, acquiesce in the necessity, which denounces our Separation, and hold them, as we hold the rest of mankind, Enemies in War, in Peace Friends.
We, therefore, the Representatives of the united States of America, in General Congress, Assembled, appealing to the Supreme Judge of the world for the rectitude of our intentions, do, in the Name, and by Authority of the good People of these Colonies, solemnly publish and declare, That these united Colonies are, and of Right ought to be Free and Independent States, that they are Absolved from all Allegiance to the British Crown, and that all political connection between them and the State of Great Britain, is and ought to be totally dissolved; and that as Free and Independent States, they have full Power to levy War, conclude Peace, contract Alliances, establish Commerce, and to do all other Acts and Things which Independent States may of right do. — And for the support of this Declaration, with a firm reliance on the protection of Divine Providence, we mutually pledge to each other our Lives, our Fortunes, and our sacred Honor.
New Hampshire:
Josiah Bartlett, William Whipple, Matthew Thornton
Massachusetts:
John Han****, Samuel Adams, John Adams, Robert Treat Paine, Elbridge Gerry
Rhode Island:
Stephen Hopkins, William Ellery
Connecticut:
Roger Sherman, Samuel Huntington, William Williams, Oliver Wolcott
New York:
William Floyd, Philip Livingston, Francis Lewis, Lewis Morris
New Jersey:
Richard Stockton, John Witherspoon, Francis Hopkinson, John Hart, Abraham Clark
Pennsylvania:
Robert Morris, Benjamin Rush, Benjamin Franklin, John Morton, George Clymer, James Smith, George Taylor, James Wilson, George Ross
Delaware:
Caesar Rodney, George Read, Thomas McKean
Maryland:
Samuel Chase, William Paca, Thomas Stone, Charles Carroll of Carrollton
Virginia:
George Wythe, Richard Henry Lee, Thomas Jefferson, Benjamin Harrison, Thomas Nelson, Jr., Francis Lightfoot Lee, Carter Braxton
North Carolina:
William Hooper, Joseph Hewes, John Penn
South Carolina:
Edward Rutledge, Thomas Heyward, Jr., Thomas Lynch, Jr., Arthur Middleton
Georgia:
Button Gwinnett, Lyman Hall, George Walton
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed, — That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn that mankind are more disposed to suffer, while evils are sufferable than to right themselves by abolishing the forms to which they are accustomed. But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security. — Such has been the patient sufferance of these Colonies; and such is now the necessity which constrains them to alter their former Systems of Government. The history of the present King of Great Britain is a history of repeated injuries and usurpations, all having in direct object the establishment of an absolute Tyranny over these States. To prove this, let Facts be submitted to a candid world.
He has refused his Assent to Laws, the most wholesome and necessary for the public good.
He has forbidden his Governors to pass Laws of immediate and pressing importance, unless suspended in their operation till his Assent should be obtained; and when so suspended, he has utterly neglected to attend to them.
He has refused to pass other Laws for the accommodation of large districts of people, unless those people would relinquish the right of Representation in the Legislature, a right inestimable to them and formidable to tyrants only.
He has called together legislative bodies at places unusual, uncomfortable, and distant from the depository of their Public Records, for the sole purpose of fatiguing them into compliance with his measures.
He has dissolved Representative Houses repeatedly, for opposing with manly firmness his invasions on the rights of the people.
He has refused for a long time, after such dissolutions, to cause others to be elected, whereby the Legislative Powers, incapable of Annihilation, have returned to the People at large for their exercise; the State remaining in the mean time exposed to all the dangers of invasion from without, and convulsions within.
He has endeavoured to prevent the population of these States; for that purpose obstructing the Laws for Naturalization of Foreigners; refusing to pass others to encourage their migrations hither, and raising the conditions of new Appropriations of Lands.
He has obstructed the Administration of Justice by refusing his Assent to Laws for establishing Judiciary Powers.
He has made Judges dependent on his Will alone for the tenure of their offices, and the amount and payment of their salaries.
He has erected a multitude of New Offices, and sent hither swarms of Officers to harass our people and eat out their substance.
He has kept among us, in times of peace, Standing Armies without the Consent of our legislatures.
He has affected to render the Military independent of and superior to the Civil Power.
He has combined with others to subject us to a jurisdiction foreign to our constitution, and unacknowledged by our laws; giving his Assent to their Acts of pretended Legislation:
For quartering large bodies of armed troops among us:
For protecting them, by a mock Trial from punishment for any Murders which they should commit on the Inhabitants of these States:
For cutting off our Trade with all parts of the world:
For imposing Taxes on us without our Consent:
For depriving us in many cases, of the benefit of Trial by Jury:
For transporting us beyond Seas to be tried for pretended offences:
For abolishing the free System of English Laws in a neighbouring Province, establishing therein an Arbitrary government, and enlarging its Boundaries so as to render it at once an example and fit instrument for introducing the same absolute rule into these Colonies
For taking away our Charters, abolishing our most valuable Laws and altering fundamentally the Forms of our Governments:
For suspending our own Legislatures, and declaring themselves invested with power to legislate for us in all cases whatsoever.
He has abdicated Government here, by declaring us out of his Protection and waging War against us.
He has plundered our seas, ravaged our coasts, burnt our towns, and destroyed the lives of our people.
He is at this time transporting large Armies of foreign Mercenaries to compleat the works of death, desolation, and tyranny, already begun with circumstances of Cruelty & Perfidy scarcely paralleled in the most barbarous ages, and totally unworthy the Head of a civilized nation.
He has constrained our fellow Citizens taken Captive on the high Seas to bear Arms against their Country, to become the executioners of their friends and Brethren, or to fall themselves by their Hands.
He has excited domestic insurrections amongst us, and has endeavoured to bring on the inhabitants of our frontiers, the merciless Indian Savages whose known rule of warfare, is an undistinguished destruction of all ages, sexes and conditions.
In every stage of these Oppressions We have Petitioned for Redress in the most humble terms: Our repeated Petitions have been answered only by repeated injury. A Prince, whose character is thus marked by every act which may define a Tyrant, is unfit to be the ruler of a free people.
Nor have We been wanting in attentions to our British brethren. We have warned them from time to time of attempts by their legislature to extend an unwarrantable jurisdiction over us. We have reminded them of the circumstances of our emigration and settlement here. We have appealed to their native justice and magnanimity, and we have conjured them by the ties of our common kindred to disavow these usurpations, which would inevitably interrupt our connections and correspondence. They too have been deaf to the voice of justice and of consanguinity. We must, therefore, acquiesce in the necessity, which denounces our Separation, and hold them, as we hold the rest of mankind, Enemies in War, in Peace Friends.
We, therefore, the Representatives of the united States of America, in General Congress, Assembled, appealing to the Supreme Judge of the world for the rectitude of our intentions, do, in the Name, and by Authority of the good People of these Colonies, solemnly publish and declare, That these united Colonies are, and of Right ought to be Free and Independent States, that they are Absolved from all Allegiance to the British Crown, and that all political connection between them and the State of Great Britain, is and ought to be totally dissolved; and that as Free and Independent States, they have full Power to levy War, conclude Peace, contract Alliances, establish Commerce, and to do all other Acts and Things which Independent States may of right do. — And for the support of this Declaration, with a firm reliance on the protection of Divine Providence, we mutually pledge to each other our Lives, our Fortunes, and our sacred Honor.
New Hampshire:
Josiah Bartlett, William Whipple, Matthew Thornton
Massachusetts:
John Han****, Samuel Adams, John Adams, Robert Treat Paine, Elbridge Gerry
Rhode Island:
Stephen Hopkins, William Ellery
Connecticut:
Roger Sherman, Samuel Huntington, William Williams, Oliver Wolcott
New York:
William Floyd, Philip Livingston, Francis Lewis, Lewis Morris
New Jersey:
Richard Stockton, John Witherspoon, Francis Hopkinson, John Hart, Abraham Clark
Pennsylvania:
Robert Morris, Benjamin Rush, Benjamin Franklin, John Morton, George Clymer, James Smith, George Taylor, James Wilson, George Ross
Delaware:
Caesar Rodney, George Read, Thomas McKean
Maryland:
Samuel Chase, William Paca, Thomas Stone, Charles Carroll of Carrollton
Virginia:
George Wythe, Richard Henry Lee, Thomas Jefferson, Benjamin Harrison, Thomas Nelson, Jr., Francis Lightfoot Lee, Carter Braxton
North Carolina:
William Hooper, Joseph Hewes, John Penn
South Carolina:
Edward Rutledge, Thomas Heyward, Jr., Thomas Lynch, Jr., Arthur Middleton
Georgia:
Button Gwinnett, Lyman Hall, George Walton
Why is the sky blue?
On a clear sunny day, the sky above us looks bright blue. In the evening, the sunset puts on a brilliant show of reds, pinks and oranges. Why is the sky blue? What makes the sunset red?
To answer these questions, we must learn about light, and the Earth's atmosphere.
THE ATMOSPHERE
The atmosphere is the mixture of gas molecules and other materials surrounding the earth. It is made mostly of the gases nitrogen (78%), and oxygen (21%). Argon gas and water (in the form of vapor, droplets and ice crystals) are the next most common things. There are also small amounts of other gases, plus many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans.
The composition of the atmosphere varies, depending on your location, the weather, and many other things. There may be more water in the air after a rainstorm, or near the ocean. Volcanoes can put large amounts of dust particles high into the atmosphere. Pollution can add different gases or dust and soot.
The atmosphere is densest (thickest) at the bottom, near the Earth. It gradually thins out as you go higher and higher up. There is no sharp break between the atmosphere and space.
LIGHT WAVES
Light is a kind of energy that radiates, or travels, in waves. Many different kinds of energy travel in waves. For example, sound is a wave of vibrating air. Light is a wave of vibrating electric and magnetic fields. It is one small part of a larger range of vibrating electromagnetic fields. This range is called the electromagnetic spectrum.
Electromagnetic waves travel through space at 299,792 km/sec (186,282 miles/sec). This is called the speed of light.
The energy of the radiation depends on its wavelength and frequency. Wavelength is the distance between the tops (crests) of the waves. Frequency is the number of waves that pass by each second. The longer the wavelength of the light, the lower the frequency, and the less energy it contains.
COLORS OF LIGHT
Visible light is the part of the electromagnetic spectrum that our eyes can see. Light from the sun or a light bulb may look white, but it is actually a combination of many colors. We can see the different colors of the spectrum by splitting the light with a prism. The spectrum is also visible when you see a rainbow in the sky.
The colors blend continuously into one another. At one end of the spectrum are the reds and oranges. These gradually shade into yellow, green, blue, indigo and violet. The colors have different wavelengths, frequencies, and energies. Violet has the shortest wavelength in the visible spectrum. That means it has the highest frequency and energy. Red has the longest wavelength, and lowest frequency and energy.
LIGHT IN THE AIR
Light travels through space in a straight line as long as nothing disturbs it. As light moves through the atmosphere, it continues to go straight until it bumps into a bit of dust or a gas molecule. Then what happens to the light depends on its wave length and the size of the thing it hits.
Dust particles and water droplets are much larger than the wavelength of visible light. When light hits these large particles, it gets reflected, or bounced off, in different directions. The different colors of light are all reflected by the particle in the same way. The reflected light appears white because it still contains all of the same colors.
Gas molecules are smaller than the wavelength of visible light. If light bumps into them, it acts differently. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates (releases, or gives off) the light in a different direction. The color that is radiated is the same color that was absorbed. The different colors of light are affected differently. All of the colors can be absorbed. But the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (It is named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)
WHY IS THE SKY BLUE?
The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.
However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.
As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.
THE BLACK SKY AND WHITE SUN
On Earth, the sun appears yellow. If you were out in space, or on the moon, the sun would look white. In space, there is no atmosphere to scatter the sun's light. On Earth, some of the shorter wavelength light (the blues and violets) are removed from the direct rays of the sun by scattering. The remaining colors together appear yellow.
Also, out in space, the sky looks dark and black, instead of blue. This is because there is no atmosphere. There is no scattered light to reach your eyes.
WHY IS THE SUNSET RED?
As the sun begins to set, the light must travel farther through the atmosphere before it gets to you. More of the light is reflected and scattered. As less reaches you directly, the sun appears less bright. The color of the sun itself appears to change, first to orange and then to red. This is because even more of the short wavelength blues and greens are now scattered. Only the longer wavelengths are left in the direct beam that reaches your eyes.
The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water. These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out. You see the longer wavelengths, and the sky appears red, pink or orange.
LEARN MORE ABOUT:THE ATMOSPHERE
WHAT IS THE ATMOSPHERE?
The atmosphere is the mixture of gases and other materials that surround the Earth in a thin, mostly transparent shell. It is held in place by the Earth's gravity. The main components are nitrogen (78.09%), oxygen (20.95%), argon (0.93%), and carbon dioxide (0.03%). The atmosphere also contains small amounts, or traces, of water (in local concentrations ranging from 0% to 4%), solid particles, neon, helium, methane, krypton, hydrogen, xenon and ozone. The study of the atmosphere is called meteorology.
Life on Earth would not be possible without the atmosphere. Obviously, it provides the oxygen we need to breath. But it also serves other important functions. It moderates the planet's temperature, reducing the extremes that occur on airless worlds. For example, temperatures on the moon range from 120 °C (about 250 °F) in the day to -170 °C (about -275 °F) at night. The atmosphere also protects us by absorbing and scattering harmful radiation from the sun and space.
Of the total amount of the sun's energy that reaches the Earth, 30% is reflected back into space by clouds and the Earth's surface. The atmosphere absorbs 19%. Only 51% is absorbed by the Earth's surface.
We are not normally aware of it but air does have weight. The column of air above us exerts pressure on us. This pressure at sea level is defined as one atmosphere. Other equivalent measurements you may hear used are 1,013 millibars, 760 mm Hg (mercury), 29.92 inches of Hg, or 14.7 pounds/square inch (psi). Atmospheric pressure decreases rapidly with height. Pressure drops by a factor of 10 for every 16 km (10 miles) increase in altitude. This means that the pressure is 1 atmosphere at sea level, but 0.1 atmosphere at 16 km and only 0.01 atmosphere at 32 km.
The density of the lower atmosphere is about 1 kg/cubic meter (1 oz./cubic foot). There are approximately 300 billion billion (3 x 10**20, or a 3 followed by 20 zeros) molecules per cubic inch (16.4 cubic centimeters). At ground level, each molecule is moving at about 1600 km/hr (1000 miles/hr), and collides with other molecules 5 billion times per second.
The density of air also decreases rapidly with altitude. At 3 km (2 miles) air density has decreased by 30%. People who normally live closer to sea level experience temporary breathing difficulties when traveling to these altitudes. The highest permanent human settlements are at about 4 km (3 miles).
LAYERS OF THE ATMOSPHERE
The atmosphere is divided into layers based on temperature, composition and electrical properties. These layers are approximate and the boundaries vary, depending on the seasons and latitude. (The boundaries also depend on which "authority" is defining them.)
LAYERS BASED ON COMPOSITION
Homosphere
· The lowest 100 km (60 miles), including the Troposphere, Stratosphere and Mesosphere.
· Contains 99% of the atmosphere's mass.
· Molecules do not stratify by molecular weight.
· Although small local variations exist, it has a relatively uniform composition, due to continuous mixing, turbulence and eddy diffusion.
· Water is one of two components that is not equally distributed. As water vapor rises, it cools and condenses, returning to earth as rain and snow. The Stratosphere is extremely dry.
· Ozone is another molecule not equally distributed. (Read about the ozone layer in the Stratosphere section below.)
Heterosphere
· Extends above homosphere, including the Thermosphere and Exosphere.
·Stratified (components are separated in layers) based on molecular weight. The heavier molecules, like nitrogen and oxygen, are concentrated in the lowest levels. The lighter ones, helium and hydrogen, predominate higher up.
LAYERS BASED ON ELECTRICAL PROPERTIES
Neutral atmosphere
· Below about 100 km (60 miles)
Ionosphere
· Above about 100 km
· Contains electrically charged particles or ions, created by the absorption of UV (ultraviolet) light.
· The degree of ionization varies with altitude.
· Different layers reflect long and short radio waves. This allows radio signals to be sent around the curved surface of the earth.
· The Aurora Borealis and Aurora Australis (the Northern and Southern Lights) occur in this layer.
· The Magnetosphere is the upper part of the ionosphere, extending out to 64,000 km (40,000 miles.) It protects us from the high energy, electrically charged particles of the solar wind, which are trapped by the Earth's magnetic field.
LAYERS BASED ON TEMPERATURE
Troposphere - Height depends on the seasons and latitude. It extends from ground level up to about 16 km (10 miles) at the equator, and to 9 km (5 miles) at the North and South Poles.
· The prefix "tropo" means change. Changing conditions in the Troposphere result in our weather.
· Temperature decreases with increasing altitude. Warm air rises, then cools and falls back to Earth. This process is called convection, and results in huge movements of air. Winds in this layer are mostly vertical.
· Contains more air molecules than all the other layers combined.
Stratosphere - Extends out to about 50 km (30 miles)
· The air is very thin.
· The prefix "strato" is related to layers, or stratification.
· The bottom of this layer is calm. Jet planes often fly in the lower Stratosphere to avoid bad weather in the Troposphere.
· The upper part of the Stratosphere holds the high winds known as the jet streams. These blow horizontally at speeds up to 480 km/hour (300 miles/hour)
· Contains the "ozone layer" located between 15 - 40 km ( 10 - 25 miles) above the surface. Although the concentration of ozone is at most 12 parts per million (ppm), it is very effective at absorbing the harmful ultraviolet (UV) rays of the sun and protecting life on Earth. Ozone is a molecule made of three oxygen atoms. The oxygen molecule we need to breathe contains two oxygen atoms.
· The temperature is cold, about -55 °C (-67 °F) in the lower part, and increases with increasing altitude. The increase is caused by the absorption of UV radiation by the oxygen and ozone.
· The temperature increase with altitude results in a layering effect. It creates a global "inversion layer", and reduces vertical convection.
Mesosphere - Extends out to about 100 km (65 miles)
· Temperature decreases rapidly with increasing altitude.
Thermosphere - Extends out to about 400 km ( 250 miles)
· Temperature increases rapidly with increasing altitude, due to absorption of extremely short wavelength UV radiation.
· Meteors, or "shooting stars," start to burn up around 110-130 km (70-80 miles) above the earth.
Exosphere -Extends beyond the Thermosphere hundreds of kilometers, gradually fading into interstellar space.
· Density of the air is so low that the normal concept of temperature loses its meaning.
· Molecules often escape into space after colliding with one another.
<A name=ICANREAD>I CAN READ
Why is the sky blue?
Light is a kind of energy that can travel through space. Light from the sun or a light bulb looks white, but it is really a mixture of many colors. The colors in white light are red, orange, yellow, green, blue and violet. You can see these colors when you look at a rainbow in the sky.
The sky is filled with air. Air is a mixture of tiny gas molecules and small bits of solid stuff, like dust.
As sunlight goes through the air, it bumps into the molecules and dust. When light hits a gas molecule, it may bounce off in a different direction. Some colors of light, like red and orange, pass straight through the air. But most of the blue light bounces off in all directions. In this way, the blue light gets scattered all around the sky.
When you look up, some of this blue light reaches your eyes from all over the sky. Since you see blue light from everywhere overhead, the sky looks blue.
In space, there is no air. Because there is nothing for the light to bounce off, it just goes straight. None of the light gets scattered, and the "sky" looks dark and black.
<A name=PROJECTS>PROJECTS TO DO TOGETHER
SAFETY NOTE: Please read all instructions completely before starting. Observe all safety precautions.
PROJECT 1 - Split light into a spectrum
What you need:
a small mirror, a piece of white paper or cardboard, water a large shallow bowl, pan, or plastic shoebox a window with direct sunlight coming in, or a sunny day outdoor What to do:
What happened: The water and mirror acted like a prism, splitting the light into the colors of the spectrum. (When light passes from one medium to another, for example from air to water, its speed and direction change. [This is called refraction, and will be discussed in a future issue.] The different colors of light are affected differently. Violet light slows the most, and bends the most. Red light slows and bends the least. The different colors of light are spread out and separated, and we can see the spectrum.)
PROJECT 2 - Sky in a jar
What you need:
a clear, straight-sided drinking glass, or clear plastic or glass jar water, milk, measuring spoons, flashlight a darkened room What to do:
PROJECT 3 -Mixing colors
You need:
a pencil, scissors, white cardboard or heavy white paper crayons or markers, a ruler a small bowl or a large cup (3 - 4 inch, or 7 - 10 cm diameter rim) a paper cup What to do:
What happened: The colors on the wheel are the main colors in white light. When the wheel spins fast enough, the colors all appear to blend together, and the wheel looks white. Try experimenting with different color combinations.
On a clear sunny day, the sky above us looks bright blue. In the evening, the sunset puts on a brilliant show of reds, pinks and oranges. Why is the sky blue? What makes the sunset red?
To answer these questions, we must learn about light, and the Earth's atmosphere.
THE ATMOSPHERE
The atmosphere is the mixture of gas molecules and other materials surrounding the earth. It is made mostly of the gases nitrogen (78%), and oxygen (21%). Argon gas and water (in the form of vapor, droplets and ice crystals) are the next most common things. There are also small amounts of other gases, plus many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans.
The composition of the atmosphere varies, depending on your location, the weather, and many other things. There may be more water in the air after a rainstorm, or near the ocean. Volcanoes can put large amounts of dust particles high into the atmosphere. Pollution can add different gases or dust and soot.
The atmosphere is densest (thickest) at the bottom, near the Earth. It gradually thins out as you go higher and higher up. There is no sharp break between the atmosphere and space.
LIGHT WAVES
Light is a kind of energy that radiates, or travels, in waves. Many different kinds of energy travel in waves. For example, sound is a wave of vibrating air. Light is a wave of vibrating electric and magnetic fields. It is one small part of a larger range of vibrating electromagnetic fields. This range is called the electromagnetic spectrum.
Electromagnetic waves travel through space at 299,792 km/sec (186,282 miles/sec). This is called the speed of light.
The energy of the radiation depends on its wavelength and frequency. Wavelength is the distance between the tops (crests) of the waves. Frequency is the number of waves that pass by each second. The longer the wavelength of the light, the lower the frequency, and the less energy it contains.
COLORS OF LIGHT
Visible light is the part of the electromagnetic spectrum that our eyes can see. Light from the sun or a light bulb may look white, but it is actually a combination of many colors. We can see the different colors of the spectrum by splitting the light with a prism. The spectrum is also visible when you see a rainbow in the sky.
The colors blend continuously into one another. At one end of the spectrum are the reds and oranges. These gradually shade into yellow, green, blue, indigo and violet. The colors have different wavelengths, frequencies, and energies. Violet has the shortest wavelength in the visible spectrum. That means it has the highest frequency and energy. Red has the longest wavelength, and lowest frequency and energy.
LIGHT IN THE AIR
Light travels through space in a straight line as long as nothing disturbs it. As light moves through the atmosphere, it continues to go straight until it bumps into a bit of dust or a gas molecule. Then what happens to the light depends on its wave length and the size of the thing it hits.
Dust particles and water droplets are much larger than the wavelength of visible light. When light hits these large particles, it gets reflected, or bounced off, in different directions. The different colors of light are all reflected by the particle in the same way. The reflected light appears white because it still contains all of the same colors.
Gas molecules are smaller than the wavelength of visible light. If light bumps into them, it acts differently. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates (releases, or gives off) the light in a different direction. The color that is radiated is the same color that was absorbed. The different colors of light are affected differently. All of the colors can be absorbed. But the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (It is named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)
WHY IS THE SKY BLUE?
The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.
However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.
As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.
THE BLACK SKY AND WHITE SUN
On Earth, the sun appears yellow. If you were out in space, or on the moon, the sun would look white. In space, there is no atmosphere to scatter the sun's light. On Earth, some of the shorter wavelength light (the blues and violets) are removed from the direct rays of the sun by scattering. The remaining colors together appear yellow.
Also, out in space, the sky looks dark and black, instead of blue. This is because there is no atmosphere. There is no scattered light to reach your eyes.
WHY IS THE SUNSET RED?
As the sun begins to set, the light must travel farther through the atmosphere before it gets to you. More of the light is reflected and scattered. As less reaches you directly, the sun appears less bright. The color of the sun itself appears to change, first to orange and then to red. This is because even more of the short wavelength blues and greens are now scattered. Only the longer wavelengths are left in the direct beam that reaches your eyes.
The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water. These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out. You see the longer wavelengths, and the sky appears red, pink or orange.
LEARN MORE ABOUT:THE ATMOSPHERE
WHAT IS THE ATMOSPHERE?
The atmosphere is the mixture of gases and other materials that surround the Earth in a thin, mostly transparent shell. It is held in place by the Earth's gravity. The main components are nitrogen (78.09%), oxygen (20.95%), argon (0.93%), and carbon dioxide (0.03%). The atmosphere also contains small amounts, or traces, of water (in local concentrations ranging from 0% to 4%), solid particles, neon, helium, methane, krypton, hydrogen, xenon and ozone. The study of the atmosphere is called meteorology.
Life on Earth would not be possible without the atmosphere. Obviously, it provides the oxygen we need to breath. But it also serves other important functions. It moderates the planet's temperature, reducing the extremes that occur on airless worlds. For example, temperatures on the moon range from 120 °C (about 250 °F) in the day to -170 °C (about -275 °F) at night. The atmosphere also protects us by absorbing and scattering harmful radiation from the sun and space.
Of the total amount of the sun's energy that reaches the Earth, 30% is reflected back into space by clouds and the Earth's surface. The atmosphere absorbs 19%. Only 51% is absorbed by the Earth's surface.
We are not normally aware of it but air does have weight. The column of air above us exerts pressure on us. This pressure at sea level is defined as one atmosphere. Other equivalent measurements you may hear used are 1,013 millibars, 760 mm Hg (mercury), 29.92 inches of Hg, or 14.7 pounds/square inch (psi). Atmospheric pressure decreases rapidly with height. Pressure drops by a factor of 10 for every 16 km (10 miles) increase in altitude. This means that the pressure is 1 atmosphere at sea level, but 0.1 atmosphere at 16 km and only 0.01 atmosphere at 32 km.
The density of the lower atmosphere is about 1 kg/cubic meter (1 oz./cubic foot). There are approximately 300 billion billion (3 x 10**20, or a 3 followed by 20 zeros) molecules per cubic inch (16.4 cubic centimeters). At ground level, each molecule is moving at about 1600 km/hr (1000 miles/hr), and collides with other molecules 5 billion times per second.
The density of air also decreases rapidly with altitude. At 3 km (2 miles) air density has decreased by 30%. People who normally live closer to sea level experience temporary breathing difficulties when traveling to these altitudes. The highest permanent human settlements are at about 4 km (3 miles).
LAYERS OF THE ATMOSPHERE
The atmosphere is divided into layers based on temperature, composition and electrical properties. These layers are approximate and the boundaries vary, depending on the seasons and latitude. (The boundaries also depend on which "authority" is defining them.)
LAYERS BASED ON COMPOSITION
Homosphere
· The lowest 100 km (60 miles), including the Troposphere, Stratosphere and Mesosphere.
· Contains 99% of the atmosphere's mass.
· Molecules do not stratify by molecular weight.
· Although small local variations exist, it has a relatively uniform composition, due to continuous mixing, turbulence and eddy diffusion.
· Water is one of two components that is not equally distributed. As water vapor rises, it cools and condenses, returning to earth as rain and snow. The Stratosphere is extremely dry.
· Ozone is another molecule not equally distributed. (Read about the ozone layer in the Stratosphere section below.)
Heterosphere
· Extends above homosphere, including the Thermosphere and Exosphere.
·Stratified (components are separated in layers) based on molecular weight. The heavier molecules, like nitrogen and oxygen, are concentrated in the lowest levels. The lighter ones, helium and hydrogen, predominate higher up.
LAYERS BASED ON ELECTRICAL PROPERTIES
Neutral atmosphere
· Below about 100 km (60 miles)
Ionosphere
· Above about 100 km
· Contains electrically charged particles or ions, created by the absorption of UV (ultraviolet) light.
· The degree of ionization varies with altitude.
· Different layers reflect long and short radio waves. This allows radio signals to be sent around the curved surface of the earth.
· The Aurora Borealis and Aurora Australis (the Northern and Southern Lights) occur in this layer.
· The Magnetosphere is the upper part of the ionosphere, extending out to 64,000 km (40,000 miles.) It protects us from the high energy, electrically charged particles of the solar wind, which are trapped by the Earth's magnetic field.
LAYERS BASED ON TEMPERATURE
Troposphere - Height depends on the seasons and latitude. It extends from ground level up to about 16 km (10 miles) at the equator, and to 9 km (5 miles) at the North and South Poles.
· The prefix "tropo" means change. Changing conditions in the Troposphere result in our weather.
· Temperature decreases with increasing altitude. Warm air rises, then cools and falls back to Earth. This process is called convection, and results in huge movements of air. Winds in this layer are mostly vertical.
· Contains more air molecules than all the other layers combined.
Stratosphere - Extends out to about 50 km (30 miles)
· The air is very thin.
· The prefix "strato" is related to layers, or stratification.
· The bottom of this layer is calm. Jet planes often fly in the lower Stratosphere to avoid bad weather in the Troposphere.
· The upper part of the Stratosphere holds the high winds known as the jet streams. These blow horizontally at speeds up to 480 km/hour (300 miles/hour)
· Contains the "ozone layer" located between 15 - 40 km ( 10 - 25 miles) above the surface. Although the concentration of ozone is at most 12 parts per million (ppm), it is very effective at absorbing the harmful ultraviolet (UV) rays of the sun and protecting life on Earth. Ozone is a molecule made of three oxygen atoms. The oxygen molecule we need to breathe contains two oxygen atoms.
· The temperature is cold, about -55 °C (-67 °F) in the lower part, and increases with increasing altitude. The increase is caused by the absorption of UV radiation by the oxygen and ozone.
· The temperature increase with altitude results in a layering effect. It creates a global "inversion layer", and reduces vertical convection.
Mesosphere - Extends out to about 100 km (65 miles)
· Temperature decreases rapidly with increasing altitude.
Thermosphere - Extends out to about 400 km ( 250 miles)
· Temperature increases rapidly with increasing altitude, due to absorption of extremely short wavelength UV radiation.
· Meteors, or "shooting stars," start to burn up around 110-130 km (70-80 miles) above the earth.
Exosphere -Extends beyond the Thermosphere hundreds of kilometers, gradually fading into interstellar space.
· Density of the air is so low that the normal concept of temperature loses its meaning.
· Molecules often escape into space after colliding with one another.
<A name=ICANREAD>I CAN READ
Why is the sky blue?
Light is a kind of energy that can travel through space. Light from the sun or a light bulb looks white, but it is really a mixture of many colors. The colors in white light are red, orange, yellow, green, blue and violet. You can see these colors when you look at a rainbow in the sky.
The sky is filled with air. Air is a mixture of tiny gas molecules and small bits of solid stuff, like dust.
As sunlight goes through the air, it bumps into the molecules and dust. When light hits a gas molecule, it may bounce off in a different direction. Some colors of light, like red and orange, pass straight through the air. But most of the blue light bounces off in all directions. In this way, the blue light gets scattered all around the sky.
When you look up, some of this blue light reaches your eyes from all over the sky. Since you see blue light from everywhere overhead, the sky looks blue.
In space, there is no air. Because there is nothing for the light to bounce off, it just goes straight. None of the light gets scattered, and the "sky" looks dark and black.
<A name=PROJECTS>PROJECTS TO DO TOGETHER
SAFETY NOTE: Please read all instructions completely before starting. Observe all safety precautions.
PROJECT 1 - Split light into a spectrum
What you need:
a small mirror, a piece of white paper or cardboard, water a large shallow bowl, pan, or plastic shoebox a window with direct sunlight coming in, or a sunny day outdoor What to do:
- Fill the bowl or pan about 2/3 full of water. Place it on a table or the floor, directly in the sunlight. (Note: the direct sunlight is important for this experiment to work right.)
- Hold the mirror under water, facing towards the sun. Hold the paper above and in front of the mirror. Adjust the positions of the paper and mirror until the reflected light shines on the paper. Observe the colored spectrum.
What happened: The water and mirror acted like a prism, splitting the light into the colors of the spectrum. (When light passes from one medium to another, for example from air to water, its speed and direction change. [This is called refraction, and will be discussed in a future issue.] The different colors of light are affected differently. Violet light slows the most, and bends the most. Red light slows and bends the least. The different colors of light are spread out and separated, and we can see the spectrum.)
PROJECT 2 - Sky in a jar
What you need:
a clear, straight-sided drinking glass, or clear plastic or glass jar water, milk, measuring spoons, flashlight a darkened room What to do:
- Fill the glass or jar about 2/3 full of water (about 8 - 12 oz. or 250 - 400 ml)
- Add 1/2 to 1 teaspoon (2 - 5 ml) milk and stir.
- Take the glass and flashlight into a darkened room.
- Hold the flashlight above the surface of the water and observe the water in the glass from the side. It should have a slight bluish tint. Now, hold the flashlight to the side of the glass and look through the water directly at the light. The water should have a slightly reddish tint. Put the flashlight under the glass and look down into the water from the top. It should have a deeper reddish tint.
PROJECT 3 -Mixing colors
You need:
a pencil, scissors, white cardboard or heavy white paper crayons or markers, a ruler a small bowl or a large cup (3 - 4 inch, or 7 - 10 cm diameter rim) a paper cup What to do:
- Use the bowl to trace a circle onto a piece of white cardboard and cut it out. With the ruler, divide it into six approximately equal sections.
- Color the six sections with the colors of the spectrum as shown. Try to color as smoothly and evenly as possible.
- Poke a hole through the middle of the circle and push the pencil part of the way through.
- Poke a hole in the bottom of the paper cup, a little bit larger than the diameter of the pencil. Turn the cup upside down on a piece of paper, and put the pencil through so the point rests on the paper on a table. Adjust the color wheel's position on the pencil so that it is about 1/2 inch (1 - 2 cm) above the cup.
- Spin the pencil quickly and observe the color wheel. Adjust as necessary so that the pencil and wheel spin easily.
What happened: The colors on the wheel are the main colors in white light. When the wheel spins fast enough, the colors all appear to blend together, and the wheel looks white. Try experimenting with different color combinations.