Chapter XII · Chapter 12

used before a singular noun to mean one of a group, when it is not a particular one

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

on the subject of; concerning

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

from one side of something to the other

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

a mixture of gases (especially oxygen) required for breathing; the stuff that the wind consists of

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

lacking fresh air

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

(quantifier) used with either mass or count nouns to indicate the whole number or amount of or every one of a class

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

used to join words or parts of a sentence that go together

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

one more of the same kind, or a different one

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

one or some or every or all without specification

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

any thing at all

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

the form of “be” used with you, we, they, or a plural noun

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

at the same time that; because; in the way that

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

in or near a particular place or position

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

used with a past participle to form the passive, or with -ing for continuous tenses

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

in the space, time, or range separating two things

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

plural of “body” — the entire physical structure of an organism (an animal, plant, or human being)

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

third-person singular of “bring” — take something or somebody with oneself somewhere

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

used to introduce something that contrasts with what came before

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

showing who or what does the action

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

to be able to, or to be allowed to

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

Dictionary entry pending editorial verification. Tap Listen to hear the word.

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

past form of “cause” — give rise to; cause to happen or occur, not always intentionally

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

get the meaning of something

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

travel across or pass over

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

divisible by two

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

pathetically lacking in force or effectiveness

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

come upon, as if by accident; meet with

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

intended to be given to, or used by, somebody

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

a powerful effect or influence

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

plural of “give” — the elasticity of something that can be stretched and returns to its original length

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

(physics) the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

a man, boy, or male animal already mentioned, as the subject

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

the male already mentioned, as the object of a verb or preposition

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

belonging to a man, boy, or male animal already mentioned

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

without hope because there seems to be no possibility of comfort or success

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

Dictionary entry pending editorial verification. Tap Listen to hear the word.

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

on condition that; in the event that

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

inside something, or within a place, period, or state

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

the form of “be” used with he, she, it, or a singular noun

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

a thing, animal, or idea already mentioned

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

be cognizant or aware of a fact or a specific piece of information; possess knowledge or information about

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the superlative of “little” that can be used with mass nouns and is usually preceded by “the”; a quantifier meaning smallest in amount or extent or degree

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

of comparatively little physical weight or density

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

the deliberate act of deviating from the truth

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

produced by a manufacturing process

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

a quantifier that can be used with count nouns and is often preceded by “as” or “too” or “so” or “that”; amounting to a large but indefinite number

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

extraordinarily good or great; used especially as intensifiers

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

a person who carries a message

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

plural of “mind” — that which is responsible for one's thoughts, feelings, and conscious brain functions; the seat of the faculty of reason

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

(comparative of “much” used with mass nouns) a quantifier meaning greater in size or amount or extent or degree

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

plural of “move” — the act of deciding to do something

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

assign a specified (usually proper) proper name to

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

in such a manner as could not be otherwise

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

not ever; at no time in the past or future

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

information about recent and important events

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

not any; not one

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

used to make a word, phrase, or sentence negative

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

plural of “ocean” — a large body of water constituting a principal part of the hydrosphere

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

belonging to, or connected with, somebody or something

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

on one occasion

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

not transmitting or reflecting light or radiant energy; impenetrable to sight

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

belonging to the speaker and others

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

used when we are both doing the action and receiving it

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

not allowed to continue to bat or run

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

have ownership or possession of

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

by chance

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

by chance

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

be fully aware or cognizant of

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

express in words

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

give a certain impression or have a certain outward aspect

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

plural of “shadow” — shade within clear boundaries

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

(quantifier) used with either mass nouns or plural count nouns to indicate an unspecified number or quantity

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the unlimited expanse in which everything is located

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

plural of “speed” — distance travelled per unit time

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

plural of “star” — (astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

(of a nose) blocked

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

fastener consisting of a narrow strip of welded metal used to join steel members

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the real physical matter of which a person or thing consists

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the star that is the source of light and heat for the planets in the solar system

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

lengthen or extend in duration or space

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

in a swift manner

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

any piece of work that is undertaken or attempted

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

express in words

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

plural of “tell” — a Swiss patriot who lived in the early 14th century and who was renowned for his skill as an archer

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

used to introduce the second part of a comparison

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

used to introduce what somebody said, thought, or felt

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

used before a noun that is already known, already mentioned, or the only one of its kind

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

the people or things already mentioned, as the object

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

in or at that place or location

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

any movable possession (especially articles of clothing)

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

judge or regard; look upon; judge

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

used for a person or thing that is near, or that has just been mentioned

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

the plural of “that”: the people or things further away, or already known

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

in spite of the fact that

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

information about recent and important events

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

used before the base form of a verb to make the infinitive

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

transmitting light; able to be seen through with clarity

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

travel across or pass over

From this reading But even though we cannot traverse space ourselves, there is a messenger that can, a messenger that needs no air to sustain him, that moves more swiftly than our feeble minds can comprehend, and this messenger brings us tidings of the stars--his name is Light.

the speaker and others, as the object of a verb or preposition

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

unusually great in size or amount or degree or especially extent or scope

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

precisely as stated

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

structure consisting of a sloping way down to the water from the place where ships are built or repaired

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the speaker together with one or more other people

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

(often used as a combining form) in a good or proper or satisfactory manner or to a high standard (“good” is a nonstandard dialectal variant for “well”)

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

used to ask for information about something

From this reading WHAT THE STARS ARE MADE OF How can we possibly tell what the stars are made of?

used to introduce a clause giving more about a thing just mentioned

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

extraordinarily good or great; used especially as intensifiers

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

the internal mechanism of a device

From this reading Light tells us many marvellous things, and not the least marvellous is the news he gives us of the workings of another force, the force of gravitation.

used for something imagined, polite, or habitual in the past

From this reading If we think of the vast oceans of space lying between them and us, and realize that we can never cross those oceans, for in them there is no air, it would seem to be a hopeless task to find out anything about the stars at all.

the person or people being spoken to

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.

belonging to the person or people being spoken to

From this reading In some ways gravitation is perhaps more wonderful than light, for though light speeds across airless space, it is stopped at once by any opaque substance--that is to say, any substance not transparent, as you know very well by your own shadows, which are caused by your bodies stopping the light of the sun.