Although the entire universe may be much larger than our observable universe, we can see only within our observable universe. The "boundary" of our observable universe is called

A) the cosmological horizon.
B) the Big Bang.
C) the lookback time.
D) the Hubble Deep Field.


A) the cosmological horizon.

Physics & Space Science

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Thermal Expansion: The coefficient of linear expansion of copper is 17 × 10-6 K-1. A block of copper 30 cm wide, 45 cm long, and 10 cm thick is heated from 0°C to 100°C What is the change in the volume of the block?

A. 2.3 × 10-5 m3  B. 4.6 × 10-5 m3 C. 5.2 × 10-5 m3 D. 6.9 × 10-5 m3 E. 14 × 10-5 m3

Physics & Space Science

A huge (essentially infinite) horizontal nonconducting sheet 10.0 cm thick has charge uniformly spread over both faces. The upper face carries +95.0 nC/m2 while the lower face carries -25.0 nC/ m2

What is the magnitude of the electric field at a point within the sheet 2.00 cm below the upper face? (?0 = 8.85 × 10-12 C2/N ? m2) A) 0.00 N/C B) 3.95 × 103 N/C C) 6.78 × 103 N/C D) 7.91 × 103 N/C E) 1.36 × 104 N/C

Physics & Space Science

When the principal quantum number is n = 5, how many different values of ? are possible?

1.1 2.5 3.9 4.25

Physics & Space Science

A helium nucleus?

A. A B. B C. C D. D E. zero F. Other G. AA H. BB I. CC J. DD

Physics & Space Science