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Physics IGCSE > Space Physics > Flashcards

Space Physics Flashcards

1
Q

How long does it take the Earth to rotate fully on its axis?

A

24 hours

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2
Q

What causes the apparant daily motion of the sun and the periodic cycle of day and night?

A

Due to the Earth’s rotation around its axis

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3
Q

How long does it take the Earth to orbit the sun

A

Approx 365 days

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4
Q

What causes the different seasons?

A

The combination of the orbiting of the Earth around the Sun and the Earth’s tilt

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5
Q

How long does it take the moon to orbit the Earth?

A

Approx one month

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6
Q

What causes the periodic nature of the Moon’s cycle?

A

The relative positions of our Sun, Earth, and Moon.
- the moon orbits earth and earth orbits the sun

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7
Q

average orbital speed equation

A

v = (2 x pi x r)/T

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8
Q

Describe the Solar System

A

Contains:
a) one star, the Sun
b) the eight named planets
c) minor planets that orbit the sun (like pluto and asteriods)
d) moons, that orbit the planets
e) smaller Solar system bodies (comets and natural satellites)

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9
Q

The eight planets in order of closest to the sun

A

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

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10
Q

The four planets near to the sun are

A

rocky and small
(mercury, venus, earth and mars)

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11
Q

the four planets furthest from the Sun are

A

gaseous and large
(jupiter, saturn, uranus, neptune)

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12
Q

accretion process

A
  • dust left over after the sun formed contained many heavy elements formed in a supernova explosion
  • first the dust made a disc which rotated around the sun due to gravity
  • slowly the dust started to clump together due to gravitational attraction between the particles
  • the inner planets are rocky because the temperature near the sun meant that only elements with high melting points existed as solids
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13
Q

satellite

A

an object that orbits a larger object

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14
Q

natural satellites

A

Asteroids, comets, moons

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15
Q

Elliptical orbit

A

An orbit that has an oval shaped path (like an elongated circle). Due to the gravitational interactions amoung the sun, planets and other celestial bodies.

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16
Q

where is the sun in the elliptical orbits

A

at one focus of the orbital ellipse (not the center)

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17
Q

The strength of the gravitational field at the surface of a planet depends on…

A

the mass of the planet

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18
Q

The strength of the gravitational field around a planet decreases as..

A

the distance from the planet increases

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19
Q

The speed of light

A

3 x 10^8

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20
Q

equation for calculating time with speed of light

A

time = distance/speed

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21
Q

Why do planets orbit the Sun?

A

Because the Sun contains most of the mass of the Solar System

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22
Q

What keeps the object in orbit around the Sun?

A

The gravitational attraction of the Sun

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23
Q

What affects the strength of the Sun gravitational field?

A

Decreases when the orbital speed decreases as the distance from the Sun increases

24
Q

Why does an object in ellipitcal orbit travel faster when closer to the Sun?

A

The closer, the stronger the gravitational pull

25
Q

Describe the sun

A
  • a star of medium size
  • consisting mostly of hydrogen and helium
  • radiates most of its energy in infrared, visible and ultraviolet regions of the EM spectrum
26
Q

what powers the stars

A

Stars are powered by nuclear reactions that release energy

27
Q

what sort of nuclear reactions occur in stable stars

A

The fusion of hydrogen into helium

28
Q

what are galaxies made up of

A

many billions of stars

29
Q

what is the star in the milky way

A

the sun

30
Q

how can astronomical distances be measured?

A

In light years, where one light year is the distance travelled in the vacuum of space by light in one year

31
Q

one light year is equal to

A

9.5 x 10^15 m

32
Q

describe the life cycle of a star before the hydrogen runs out

A
  1. a star is formed from interstellar clouds of dust and gas that contain hydrogen
  2. a protostar is a interstellar cloud collasping and increasing in temp as a result of its internal gravitational attraction
  3. a protostar becomes a stable star when the inward force of gravitational attraction is balanced by an outward force due to high temp in centre of the star
  4. all stars eventually run out of hydrogen as fuel for the nuclear reaction
33
Q

How are stars formed? (simple answer)

A

from interstellar clouds of gas and dust that contain hydrogen

34
Q

whats a protostar

A

an interstellar cloud collasping and increasing in temperature as a result of its internal gravitational attraction

35
Q

when does a protostar become a stable star

A

when the inward force of gravitational attraction is balanced by an outward force due to the high temperature in the centre of the star

36
Q

what happens when most of the hydrogen in the centre of the star has been converted to helium

A

Most stars would expand to form red giants and more massive stars expand to form red supergiants

37
Q

what does a red giant from a less massive star forms?

A

a planetary nebula with a white dwarf star at its centre

38
Q

what happens when a red supergiant explodes?

A

it explodes as a supernova forming a nebula containing hydrogen and new heavier elements, leaving behind a neutron star or a black hole at its centre

39
Q

what could a nebula from a supernova form

A

new stars with orbiting planets

40
Q

describe the milky way

A

one of many billions of galaxies making up the universe. Has the diameter of 100,000 light years

41
Q

redshift

A

increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies
- in distant galaxies the lines have shifted towards the red end of the specturm

42
Q

how does the light emitted from distant galaxies appear as

A

appears redshifted in comparision with light emitted on the Earth

43
Q

evidence supporting the big bang theory

A

the redshift in the light from distant galaxies

44
Q

What is CMBR?

A

Cosmic microwave background radiation.
- microwave radiation of a specific frequency is observed at all points in space around us.

45
Q

when was CMBR produced and how has it expanded

A
  • produced shortly after the universe was formed
  • the radiation expanded into the microwave region of the electromagnetic spectrum as the universe expanded
46
Q

how can the speed at which a galaxy is moving away from earth be found?

A

from the change in wavelength of the galaxy’s starlight due to redshift

47
Q

how can the distance of a far galaxy be determined?

A

using the brightness of a supernova in that galaxy

48
Q

hubble constant (Ho)

A

the ratio of the speed at which the galaxy is moving away from the Earth to its distance from the Earth

49
Q

hubble constant formula

A

H0 = v/d
v = speed
d = distance

50
Q

current estimate for the hubble constant (H0)

A

2.2 x 10^-18 per second

51
Q

what does 1/H0 =

A

d/v

52
Q

what does 1/H0 represent

A
  • an estimate for the age of the Universe
  • is the evidence for the idea that all the matter in the Universe was present at a single point
53
Q

Properties of CMBR

A
  • has the same intensity everywhere
  • temperature corresponds to 2.7K
  • there is structure in background intensity (has ripples)
54
Q

How does CMBR support the big bang theory

A

Since this radiation was produced shrotly after the big bang and has now been redshifted/expanded into the microwave region

55
Q

Why is our understanding of the earliest moments of the universe unreliable?

A
  • no experimental evidence
  • state of matter is unknown
  • temperature too high to reproduce

Physics IGCSE (20 decks)

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